The Project Gutenberg eBook of Transactions of the American Society of Civil Engineers, vol. LXXII, June, 1911, by American Society of Civil Engineers and E. D. Hardy

This ebook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this ebook or online at https://www.gutenberg.org/license. If you are not located in the United States, you’ll have to check the laws of the country where you are located before using this eBook.

Title: Transactions of the American Society of Civil Engineers, vol. LXXII, June, 1911

Subtitle: Water Purification Plant, Washington, D. C. Results of Operation.

Author: American Society of Civil Engineers and E. D. Hardy

Release Date: December 27, 2008 [EBook #27632]

Language: English

Credits: Produced by Juliet Sutherland, Christina and the Online Distributed Proofreading Team at https://www.pgdp.net

*** START OF THIS PROJECT GUTENBERG EBOOK ***

PLATE 1: WASHINGTON AQUEDUCT, D. C. FILTRATION PLANT INJECTOR SAND-HANDLING SYSTEM

AMERICAN SOCIETY OF CIVIL ENGINEERS

INSTITUTED 1852

TRANSACTIONS

Paper No. 1191

WATER PURIFICATION PLANT, WASHINGTON, D. C.

RESULTS OF OPERATION.[1]

BY E. D. HARDY, M. AM. SOC. C. E.

WITH DISCUSSION BY MESSRS. ALLEN HAZEN, GEORGE A. JOHNSON,

MORRIS KNOWLES, GEORGE C. WHIPPLE, F. F. LONGLEY, AND E. D. HARDY.

The Washington filtration plant has already been fully described.[2] At the time that paper was written (November, 1906), the filtration plant had been in operation for only about 1 year. It has now been in continuous operation for 5 years, and many data on the cost, efficiency, and methods of operation, have accumulated in the various records and books which have been kept. It is thought that a brief review of the results, and a summary of the records in tabular form, will be of interest to the members of the Society, and it is also hoped that the discussion of this paper will bring out the comparative results of operation of other filter plants. As a matter of convenience, the following general description of the plant is given.

Description of the Filtration Plant.—The Washington filtration plant was completed and put in operation in October, 1905. It consists of a pumping station for raising the water from the McMillan Park Reservoir to the filter beds; 29 filters of the slow sand type, having an effective area of 1 acre each; the filtered-water reservoir, having a capacity of about 15,000,000 gal.; and the necessary piping and valves for carrying water, controlling rates of filtration, etc.

1 Presented at the meeting of February 15th, 1911.

2 "Works for the Purification of the Water Supply of Washington, D. C.," by Allen Hazen and E. D. Hardy, Members, Am. Soc. C. E., Transactions, Am. Soc. C. E., Vol. LVII, p. 307.

In the pumping station, there are three centrifugal pumps, which are directly connected to tandem compound engines; two sand‑washer pumps; three small electric generating sets for furnishing electric light; and four 200‑h.p., water-tube boilers.

Each of the centrifugal pumps has a nominal capacity of 40,000,000 gal. per day when pumping against a head of 21 ft., and each sand‑washer pump has a capacity of 2,500,000 gal. when pumping against a head of 250 ft. The electric light engines and generators supply the current for lighting the pumping station, the office and laboratory and other buildings, and also the courts and interior of the filter beds, and for operating a machine‑shop.

The filters and filtered‑water reservoir are built entirely of concrete masonry. The floors are of inverted groined arches on which rest the piers for supporting the groined arch vaulting. All this concrete work is similar to that in the Albany, Philadelphia, and Pittsburg filters.

The filters contain, on an average, 40 in. of filter sand and 12 in. of filter gravel. The gravel is graded from coarse to fine; the lower and coarser part acts as part of the under‑drain system, and the upper and finest layer supports the filter sand. The raw water from the pumps is carried to the filters through riveted steel rising mains which have 20‑in. cast‑iron branches for supplying the individual filters. The filtered water is collected in the under‑drainage system of the several filter beds, and is carried through 20‑in., cast‑iron pipes to the regulator‑houses. These regulator‑houses contain the necessary valves, registering apparatus, etc., for regulating the rate of filtration, showing the loss of head, shutting down a filter, filling a filter with filtered water from the under‑drains, and for turning the water back into the raw‑water reservoir, or wasting it into the sewer. From the regulator‑houses, the filtered water flows directly to thefiltered‑water reservoir. Generally, five filters are controlled from one house, but there are two cases where the regulator‑houses are smaller, and only two filters are controlled from each.

The dirty sand removed from the filters is carried by a portable ejector through one or more lengths of 3‑in. hose and a fixed line of 4‑in. pipe, to the sand washers. From the sand washers, the washed sand is carried to the reinforced concrete storage bins, each of which has a capacity of 250 cu. yd., and is at such an elevation that carts may be driven under it and loaded through a gate.

Until April, 1909, the sand was replaced in the filters by carts which were filled through the gates in the sand bins. It was then hauled to the top of the filter beds and dumped through the manholes on the chutes, which could be revolved in any direction. These chutes were used to prevent the sand from being unduly compacted in the vicinity of the manholes, and to facilitate spreading it in the filters. Since April, 1909, all the sand has been replaced by the hydraulic method. An ejector is placed under the gate in the sand bin, and the sand is carried in a reverse direction from the bin through the 4‑in. piping and one or more lengths of hose to the filter bed. This process has lowered the cost of re‑sanding considerably, and present indications are that it will prove entirely satisfactory in every way.

The average effective size and uniformity coefficient of the filters are shown in Table 1.

TABLE 1—FILTER SAND AS ORIGINALLY PLACED.

Filter No.

Average effective size, in millimeters.

Average uniformity coefficient.

Depth of sand, in inches.

Average turbidity.

1

0.32

1.88

35.3

2,600

2

0.30

1.78

37.7

2,200

3

0.32

1.77

40.2

3,000

4

0.29

1.80

42.5

1,800

5

0.34

1.74

44.9

2,700

6

0.31

1.78

37.7

2,300

7

0.29

1.72

40.1

2,300

8

0.32

1.75

40.2

2,800

9

0.32

1.78

42.5

2,900

10

0.30

1.69

39.5

2,500

11

0.34

1.93

37.1

2,600

12

0.29

1.66

34.7

2,100

13

0.32

1.83

33.6

3,500

14

0.29

1.66

33.6

2,600

15

0.33

1.75

39.0

2,400

16

0.33

1.78

42.3

3,000

17

0.33

1.86

45.5

3,300

18

0.34

1.80

48.7

3,100

19

0.34

1.80

52.0

...

20

0.34

1.87

39.0

2,700

21

0.32

1.82

42.3

2,400

22

0.33

1.74

45.5

2,200

23

0.33

1.81

48.7

2,300

24

0.35

1.80

52.0

2,600

25

0.29

1.64

39.5

2,400

26

0.31

1.71

37.1

2,100

27

0.31

1.71

34.7

1,900

28

0.33

1.93

33.6

2,300

29

0.34

1.93

33.6

3,000

Maximum

0.36

1.93

52.0

3,300

Minimum

0.29

1.64

33.6

1,800

Average

0.32

1.77

40.4

2,600

Description of Washington Aqueduct.—The water supply of Washington is taken from the Potomac River, at Great Falls, about 16 miles above the city. At that place, a dam has been built across the river, which holds the water at an elevation of 150.5 ft. above mean tide at Washington. From Great Falls the water flows by gravity for a distance of 16 miles through a 9‑ft. conduit, three reservoirs, and a tunnel. From McMillan Park Reservoir, the last of the three, the water is lifted by centrifugal pumps about 21 ft. to the filters. After passing through the filters, it flows to the filtered‑water reservoir, and later to the city mains. In its passage from Great Falls to the filters, the water flows through three settling reservoirs, which have already been referred to. These reservoirs are known as the Dalecarlia, the Georgetown, and the McMillan Park Reservoirs, and have available capacities of 141,000,000, 140,000,000, and 180,000,000 gal., respectively.

Turbidity.—The Potomac River water is rather turbid, the turbidity being caused by very fine particles of clay. The river is subject to sudden fluctuations, it being no uncommon thing to have a turbidity of 100 one day, and 1,000 the next. The high turbidity usually disappears about as rapidly as it comes, and is seldom higher than 500 for more than 5 days at a time. It is frequently the case, however, that a succession of waves of high turbidity will appear so close together that the effect of one has not disappeared before that of another is felt.

The clarification of the water supply begins at the dam at Great Falls. Here it is a clarification by exclusion, for when an excessive quantity of mud appears in the river water, the gates are closed, and the muddy water is allowed to flow over the dam and form mud‑bars in the Lower Potomac, while the city is supplied from the water stored in the three settling reservoirs. Until a comparatively recent date, the excessively muddy water was never excluded, having been taken, like other decrees of Providence, as it came.

During the summer of 1907, the practice of shutting out water with a turbidity of 500 or more was established for the warm months. This practice was discontinued during the cold months, as it was feared that a very high consumption of water might occur at the time of low water in the reservoirs, and so cause a partial famine. During the winter of 1909‑10, however, the gates were closed, as was the practice throughout the summer months.

When the reservoirs are well filled, and the consumption of water is less than 70,000,000 gal. per day, it is safe to close the gates at Great Falls for a period of about 4 days.

FIGURE 1—PLAN AND PROFILE OF WASHINGTON AQUEDUCT.

While a considerable reduction in turbidity is effected in each of the reservoirs, the bulk of the mud is deposited at the upper end of Dalecarlia Reservoir. This reservoir had become so completely filled, that, in 1905, it was necessary to dredge a channel through the deposit, in order to allow the water to pass it. During the summers of 1907 and 1908, a 10‑in. hydraulic dredge removed more than 100,000 cu. yd. of mud which had been deposited in this reservoir. The mud deposited in Georgetown and McMillan Park Reservoirs is so fine that the accumulation of many years is not very noticeable in its effect on the depth of water.

The particles of clay which remain in the water after its passage through the three reservoirs, are so exceedingly small that they do not settle out in any reasonable length of time. Even the filtration of the water through one or more slow sand filters occasionally fails to remove the last trace of turbidity. This is especially true in the colder months, and not a winter has passed when the water supply has not been noticeably turbid at some time.

A general idea of the quantity of mud contained in the river water, the quantity excluded by closing the gates at Great Falls, and that removed by sedimentation and filtration, may be gained from Table 2, which is, of course, only a rough approximation.

Table 2 also shows that the gates were closed 10.50% of the time, thereby excluding 40.06% of the total suspended matter which otherwise would have entered the system.

The turbidities, bacterial counts, and chemical analyses of numerous samples of water are shown in Tables 3, 4, 5, and 6. The amount of work done in the pumping station, average consumption of water, death rate from typhoid fever, and filter runs are shown in Tables 7, 8, 9, and 10.

Raking.—At the time the filters were first put in service, the sand bins had not been completed, and, consequently, the work of cleaning the filters was carried on in the old‑fashioned way of scraping by hand and wheeling out the sand in barrows. This method of cleaning was used from October, 1905, to April, 1906; then the regular sand‑handling system was commenced.

At times, during the first two summers the filters were in operation, considerable difficulty was experienced in keeping them cleaned as fast as was necessary to provide an ample supply of filtered water. For a short period in each summer it was found necessary to organize night shifts, and keep the work of cleaning in progress for from 16 to 24 hours per day.

FIGURE 2—GENERAL PLAN OF WASHINGTON FILTRATION PLANT SHOWING FINISHED SURFACES.

TABLE 2—TONS OF SUSPENDED MATTER ENTERING SYSTEM, ETC.

Month.

Amount that would have entered the system if the gates had been left continuously open.

Number of hours gates were closed.

Amount shut out.

Amount deposited in Dalecarlia Reservoir.

Amount deposited in Georgetown Reservoir.

Amount deposited in McMillan Park Reservoir.

Amount entering filtration plant.

Total.

1909.

July

318

32.0

3

0

125

74

116

318

August

146

47.0

1

0

78

38

29

146

September

97

57.0

7

21

13

38

18

97

October

61

90.5

8

7

9

25

12

61

November

50

60.0

4

13

5

17

11

50

December

370

99.0

126

108

33

59

44

370

1910.

January

2,410

136.0

1,109

1,020

67

117

97

2,410

February

839

117.5

481

126

56

75

101

839

March

208

7.5

13

43

15

13

124

208

April

321

65.0

17

195

43

43

23

321

May

197

84.5

58

54

22

24

39

197

June

1,505

124.0

786

535

49

88

47

1,505

Total

6,522

920.0

2,613

2,212

515

611

661

6,522

In order to relieve the situation at such times, the expedient of raking was tried. This was first attempted with the filters filled with water; the effluent was first shut off in order to prevent a downward flow of water, and the filter was then raked or harrowed from boats. This method was not satisfactory, however, as the work was neither as uniform nor as thorough as necessary. Later, the filters were drained to the necessary depth, and the surface of the sand was thoroughly stirred with iron garden rakes. The filters were then filled with filtered water through the under‑drains and put in service.

This latter method proved so satisfactory that it has been resorted to at all times when the work was at all pressing. When the runs were of short duration, and the depth to which the mud had penetrated the filter sand was slight, a raking seemed to be nearly as effective in restoring the filter capacity as a scraping; it could be done in 8 hours by 3 laborers, and there seemed to be no ill effects from lowered efficiency.

TABLE 3—TURBIDITIES.

Average by Months.

(United States Geological Survey Standard.)

Month.

Great Falls.

RESERVOIRS:

Dalecarlia Outlet.

Gerogetown Outlet.

McMillan Park Outlet.

Filtered water.

Max.

Ave.

Max.

Ave.

Max.

Ave.

Max.

Ave.

Max.

Ave.

1905.

October

100

36

40

21

32

18

20

11

4

1

November

35

19

34

19

22

14

14

11

3

1

December

1,500

199

250

84

150

74

95

39

14

6

1906.

January

700

94

180

60

120

60

85

52

20

12

February

120

45

85

41

55

29

35

22

5

3

March

1,750

272

350

181

120

56

90

46

8

6

April

1,270

167

180

72

95

58

75

46

12

7

May

600

56

50

20

45

16

34

10

3

2

June

1,700

303

500

125

450

94

180

41

13

2

July

1,000

130

180

54

150

47

250

43

13

3

August

1,530

375

250

112

95

66

65

45

5

2

September

120

33

180

34

95

28

75

25

7

2

October

1,025

127

110

37

60

24

55

21

1

1

November

160

27

75

20

45

16

24

13

1

1

December

600

69

110

31

80

28

80

26

8

2

1907.

January

400

135

150

70

110

75

70

53

11

7

February

55

26

26

15

36

16

40

17

5

2

March

950

248

180

77

130

70

90

57

7

4

April

200

47

80

33

60

30

45

24

4

2

May

130

29

40

18

26

15

14

9

1

1

June

400

104

160

48

75

32

40

18

1

1

July

600

114

130

61

78

47

45

31

1

1

August

800

73

130

35

85

26

30

14

1

0

September

600

129

[1]

[1]

150

51

70

28

1

0

October

75

32

[1]

[1]

65

28

75

26

4

0

November

300

97

[1]

[1]

100

45

45

23

2

1

December

680

135

[1]

[1]

180

61

100

46

10

4

1908.

January

2,100

202

340

73

250

82

160

65

20

7

February

3,000

302

300

52

150

52

75

32

7

4

March

300

91

150

78

100

68

65

42

5

4

April

75

23

65

41

37

27

26

20

3

2

May

2,000

172

130

48

85

37

50

20

1

1

June

400

40

70

29

40

24

30

18

1

1

July

1,500

149

...

74

170

44

75

15

0

0

August

900

129

200

[1]

150

56

85

39

2

1

September

75

24

[1]

[1]

50

19

35

18

0

0

October

95

20

[1]

[1]

55

18

28

15

0

0

November

24

11

[1]

[1]

20

11

19

10

0

0

December

20

9

17

11

14

9

10

7

0

0

1909.

January

400

72

95

32

60

23

25

16

4

1

February

650

194

120

64

90

51

55

35

4

3

March

250

51

[1]

[1]

90

44

60

37

8

4

April

750

98

[1]

[1]

130

42

76

31

2

1

May

480

57

[1]

[1]

30

19

30

12

2

1

June

650

141

[1]

[1]

120

51

80

30

1

0

July

400

48

[1]

[1]

215

46

120

35

2

1

August

180

23

[1]

[1]

50

17

18

9

0

0

September

26

16

24

14

[1]

[1]

25

6

0

0

October

14

10

15

10

11

9

8

4

0

0

November

11

9

11

8

10

8

6

4

0

0

December

600

63

110

31

80

28

50

15

3

0

1910.

January

3,000

357

200

58

150

53

115

30

5

2

February

3,000

143

150

55

120

50

100

36

7

4

March

210

36

100

35

95

38

100

43

9

5

April

350

55

100

25

55

18

25

8

1

0[2]

May

300

33

55

19

50

17

28

13

1

0[2]

June

1,500

246

180

42

110

37

50

16

1

0[2]

Fiscal years.

1905-06[2]

1,750

133

500

70

450

47

180

31

20

5

1906-07

1,530

114

250

46

150

37

250

29

13

2

1907-08

3,000

117

340

53

250

45

160

31

20

2

1908-09

1,500

79

200

50

170

32

85

22

8

1

1909-10

2,100

86

200

30

215

29

120

18

9

1

1 Reservoirs out of service.

2 October to June 30th.

TABLE 4—BACTERIA.

Averages by Months.

Month.

RESERVOIRS:

Dalecarlia Inlet.

Dalecarlia Outlet.

Georgetown Outlet.

McMillan Park Outlet.

Filtered water.

1905.

October

...

...

...

210

80

November

...

...

...

150

27

December

...

15,500

...

3,800

60

1906.

January

...

2,800

...

1,500

39

February

2,900

4,100

1,800

550

16

March

1,800

1,100

900

650

19

April

3,300

1,700

700

400

22

May

425

210

95

65

17

June

7,900

4,600

325

220

17

July

13,500

600

475

160

26

August

8,700

1,100

1,200

190

14

September

425

250

140

135

14

October

2,300

950

650

270

16

November

1,800

1,100

1,200

220

12

December

6,900

3,800

3,600

700

45

1907.

January

4,400

2,400

2,200

950

70

February

1,000

950

1,000

700

45

March

11,500

8,300

7,200

3,600

65

April

3,700

2,100

1,400

475

21

May

750

350

325

130

26

June

2,300

1,000

600

100

18

July

2,700

575

350

160

17

August

3,000

275

425

80

17

September

6,200

[1]

1,900

230

32

October

1,400

[1]

950

275

27

November

8,900

[1]

6,600

1,500

27

December

16,000

[1]

9,600

4,300

190

1908.

January

11,000

8,700

9,400

3,700

190

February

11,500

6,000

5,000

2,800

75

March

4,600

4,000

2,900

1,300

30

April

700

450

250

120

13

May

9,500

1,100

650

325

17

June

750

120

110

95

12

July

4,900

...

400

150

8

August

1,600

325

300

100

12

September

325

[1]

200

80

11

October

375

[1]

325

140

8

November

550

[1]

300

200

12

December

800

750

375

170

23

1909.

January

11,000

2,700

1,600

700

31

February

8,000

3,500

2,400

1,300

60

March

3,800

[1]

2,600

1,000

39

April

2,200

[1]

1,400

550

12

May

900

[1]

350

140

16

June

3,400

[1]

1,200

170

21

July

550

[1]

500

250

33

August

400

[1]

325

55

18

September

325

240

[1]

70

18

October

350

275

250

130

20

November

600

500

500

180

13

December

21,000

9,100

5,900

4,500

250

1910.

January

76,000

78,000

88,000

52,000

800

February

45,000

35,500

31,000

17,500

350

March

9,900

7,600

7,400

4,800

80

April

7,900

4,100

3,500

650

29

May

1,230

810

830

448

28

June

3,660

930

800

324

27

Fiscal years:

1905-06

3,300[2]

4,300[3]

750[4]

850[2]

33[2]

1906-07

4,900

1,900

1,700

650

31

1907-08

6,360

2,700

2,900

1,300

55

1908-09

3,400

2,000

950

400

21

1909-10

14,300

13,900

10,900

6,890

143

1 Reservoirs out of service.

2 October to June 30th.

3 December to June 30th.

4 February to June 30th.

TABLE 5—RESULTS OF TESTS FOR Bacillus Coli.

Percentage Positive.

Month.

Great Falls, or Dalecarlia Reservoir Inlet.

Dalecarlia Reservoir Outlet.

Georgetown Reservoir.

McMillan Park Reservoir (applied water).

Filtered water reservoir.

Tap water from various parts of city.

10 c.c.

1 c.c.

0.1 c.c.

10 c.c.

1 c.c.

0.1 c.c.

10 c.c.

1 c.c.

0.1 c.c.

10 c.c.

1 c.c.

0.1 c.c.

10 c.c.

1 c.c.

10 c.c.

1 c.c.

1906.

January[1]

55.6

38.9

22.2

69.2

23.1

7.7

56.0

40.0

8.0

55.6

22.2

0

7.2

0

...

...

February

33.3

26.7

6.7

26.1

17.4

8.7

30.4

13.0

4.4

8.3

4.2

0

0

0

...

...

March

50.0

12.5

0

45.5

18.2

0

20.8

8.3

0

18.5

7.4

3.7

0

0

0

0

April

72.2

33.3

16.7

95.5

50.0

4.6

59.1

22.7

4.6

32.0

8.0

0

4.0

0

0

0

May

20.0

8.0

4.0

20.0

12.0

0

7.8

0

0

0

0

0

0

0

0

0

June

57.7

38.5

19.2

40.0

32.0

8.0

50.0

34.6

0

23.1

7.7

3.8

0

0

3.1

0

July

65.0

50.0

5.0

60.0

25.0

10.0

15.0

5.0

5.0

9.5

0

0

4.8

0

...

...

August

84.6

69.2

61.5

88.5

65.4

34.6

80.0

57.7

23.1

63.0

33.3

0

7.4

3.7

11.9

5.1

September

50.0

10.0

0

30.0

10.0

10.0

40.0

10.0

0

32.0

12.0

0

8.0

0

3.1

0

October

60.0

30.0

10.0

55.5

33.3

0

80.0

60.0

20.0

48.1

22.2

3.7

3.7

0

13.0

3.7

November

37.5

0

0

25.0

12.5

12.5

37.5

25.0

0

20.0

12.0

0

8.0

0

0

0

December

55.5

44.5

0

66.7

44.5

22.2

66.7

22.2

0

20.8

8.3

4.2

16.7

8.3

7.5

0

1907.

January

77.8

33.3

22.2

66.7

33.3

0

55.5

55.5

22.2

69.3

34.6

3.8

19.2

11.5

14.0

0

February

37.5

25.0

0

12.5

0

0

37.5

12.5

0

17.4

4.4

0

0

0

2.9

0

March

87.5

50.0

0

75.0

37.5

0

50.0

25.0

0

30.8

7.7

0

0

0

2.1

0

April

44.5

11.1

11.1

66.7

22.2

11.1

77.8

11.1

11.1

46.1

19.2

3.8

3.8

0

3.2

0

May

91.3

65.2

17.4

88.9

33.3

0

87.5

50.0

12.5

23.1

0

0

0

0

1.4

0

June

80.0

68.0

24.0

87.5

62.5

0

66.7

44.5

11.1

40.0

8.0

0

0

0

0

0

July

42.3

30.8

19.2

25.0

12.5

0

22.2

22.2

0

3.8

0

0

0

0

1.4

1.4

August

48.1

29.6

3.7

33.3

16.7

16.7

36.4

18.2

0

14.8

3.7

0

0

0

0

0

September

62.5

54.1

25.0

...

...

...

41.7

33.3

16.7

16.0

4.0

0

4.0

0

1.7

0

October

51.9

40.8

7.4

...

...

...

53.3

40.0

6.7

38.7

25.8

9.7

6.5

0

12.5

2.8

November

80.0

64.0

24.0

...

...

...

72.7

54.5

0

58.6

17.3

3.5

0

0

4.9

0

December

56.0

48.0

16.0

...

...

...

46.2

38.5

7.7

45.2

29.0

0

19.3

3.2

12.9

4.3

1908.

January

46.2

30.8

15.4

50.0

12.5

0

33.3

0

0

22.6

9.7

3.2

3.2

0

1.9

1.9

February

12.5

0

0

25.0

0

0

12.5

0

0

0

0

0

0

0

0

0

March

38.5

19.2

7.7

44.4

11.1

0

11.1

0

0

9.7

0

0

0

0

0

0

April

15.4

7.7

0

0

0

0

0

0

0

6.7

3.3

0

0

0

0

0

May

76.0

52.0

40.0

87.5

50.0

12.5

33.3

22.2

0

45.1

16.2

0

0

0

0

0

June

7.7

0

0

0

0

0

11.1

0

0

0

0

0

0

0

0

0

July

26.9

15.4

11.5

22.2

22.2

0

11.1

0

0

6.4

6.4

0

0

0

0

0

August

46.2

26.9

3.9

44.4

33.3

0

62.5

25.0

12.5

12.9

3.2

0

0

0

1.6

0

September

20.0

8.0

4.0

42.9

28.6

1.4

22.2

11.1

0

16.7

10.0

0

0

0

4.3

0

October

18.4

3.7

0

0

0

0

9.1

0

0

9.7

6.4

3.2

0

0

0

0

November

13.0

0

0

28.6

0

0

11.1

0

0

6.6

0

0

0

0

0

0

December

11.5

7.7

3.8

0

0

0

12.5

0

0

3.2

0

0

0

0

0

0

1909.

January

12.0

8.0

0

30.0

10.0

0

0

0

0

3.2

3.2

0

3.2

0

0

0

February

52.1

47.8

47.8

28.6

14.3

0

37.5

0

0

7.1

3.6

3.6

0

0

3.4

3.4

March

69.4

34.6

3.8

50.0

25.0

0

44.5

11.1

0

32.3

19.4

3.2

6.5

0

2.8

1.4

April

42.3

15.4

3.9

33.3

22.2

11.1

44.4

22.2

11.1

36.6

10.0

0

0

0

0

0

May

88.4

26.1

4.3

50.0

12.5

0

33.3

0

0

12.9

3.2

0

0

0

0

0

June

85.0

60.0

25.0

60.0

40.0

10.0

44.4

33.3

11.1

53.3

20.0

0

0

0

1.4

0

July

34.8

8.7

4.4

...

...

...

33.3

11.1

0

25.8

12.9

0

0

0

0

0

August

50.0

15.4

7.7

...

...

...

40.0

10.0

0

22.6

6.5

3.2

0

0

0

0

September

43.5

21.8

8.7

25.0

25.0

12.5

0

0

0

13.3

3.3

0

0

0

0

0

October

36.4

13.6

0

18.2

0

0

0

0

0

3.2

0

0

0

0

0

0

November

4.5

0

0

10.0

0

0

0

0

0

0

0

0

0

0

0

0

December

38.5

23.1

7.7

36.4

36.4

18.2

33.3

22.2

11.1

29.0

22.6

0

9.7

6.5

7.3

1.5

1910.

January

72.0

48.0

24.0

44.5

33.3

11.1

75.0

25.0

0

61.3

35.5

9.7

5.8

3.2

15.9

3.2

February

47.8

43.5

17.4

63.2

21.1

5.3

40.0

30.0

5.0

32.2

7.1

0

3.6

0

0

0

March

33.3

14.8

0

30.8

11.1

3.7

29.6

22.2

7.4

12.9

3.2

0

0

0

0

0

April

41.7

33.3

20.8

40.0

32.0

16.0

38.5

23.1

15.4

23.3

13.3

0

0

0

0

0

May

47.8

17.4

0

52.0

20.0

0

36.0

16.0

4.0

16.1

12.9

0

0

0

0

0

June

95.5

86.4

31.8

80.8

46.2

19.2

64.0

28.0

8.0

43.3

6.7

0

0

0

1.4

0

Fiscal years:

1905-06

35.2

19.4

9.3

0.0

3.2

5.2

6.4

4.9

1.7

4.3

8.3

.8

.3

1.8

1.3

0

1906-07

61.5

43.6

9.2

7.7

9.2

2.3

1.1

9.8

0.7

2.5

3.0

.4

.5

2.1

5.4

1.0

1907-08

44.6

31.3

3.0

2.3

2.3

3.1

4.4

2.1

4.1

2.2

9.4

.4

.8

0.3

3.1

0.9

1908-09

38.9

20.3

8.4

0.0

5.0

0

7.4

8.5

2.8

6.7

7.1

.8

.8

0

1.2

0.4

1909-10

45.5

26.9

0.1

5.3

4.0

8.8

7.9

9.8

6.2

3.6

0.4

.1

.3

0.8

2.2

0.4

1 Presumptive tests.

TABLE 6—SUMMARY OF SANITARY CHEMICALS ANALYSES OF WEEKLY SAMPLES, JULY 1ST, 1909, TO JUNE 30TH, 1910.

(Results in Parts per Million.)

(A) MAXIMUM.

Reservoirs.

Turbidity[1]

Ammonia.

Nitrogen as:

Hardness

Alkalinity

Chlorine

Free

Albuminoid

Total

Nitrites

Nitrates

Dalecarlia inlet

2,100

0.034

0.264

0.280

0.0070

0.45

120.0

106.0

5.4

Dalecarlia outlet[2]

200

0.034

0.180

0.206

0.0050

0.70

115.0

105.8

5.7

Georgetown outlet[3]

215

0.030

0.182

0.182

0.0060

0.60

115.0

105.0

4.9

McMillan Park outlet

120

0.028

0.126

0.154

0.0060

0.65

118.0

104.4

4.2

Filtered water

9

0.016

0.078

0.086

0.0010

0.70

119.5

106.3

4.5

TABLE 6—(Continued.)

(B) MINIMUM.

Reservoirs.

Turbidity[1]

Ammonia.

Nitrogen as:

Hardness

Alkalinity

Chlorine

Free

Albuminoid

Total

Nitrites

Nitrates

Dalecarlia inlet

7

0.000

0.016

0.016

0.0000

0.00

52.9

39.5

1.0

Dalecarlia outlet[2]

7

0.000

0.040

0.040

0.0000

0.00

54.3

38.2

0.9

Georgetown outlet[3]

7

0.000

0.044

0.044

0.0000

0.00

51.4

40.6

0.7

McMillan Park outlet

2

0.000

0.010

0.010

0.0010

0.00

51.4

38.5

0.2

Filtered water

0

0.000

0.000

0.000

0.0000

0.00

52.9

40.3

0.4

TABLE 6—(Continued.)

(C) AVERAGE.

Reservoirs.

Turbidity[1]

Ammonia.

Nitrogen as:

Hardness

Alkalinity

Chlorine

Free

Albuminoid

Total

Nitrites

Nitrates

Dalecarlia inlet

86

0.006

0.167

0.113

0.0027

0.19

93.2

81.4

2.9

Dalecarlia outlet[2]

30

0.008

0.106

0.114

0.0023

0.18

95.5

79.5

3.4

Georgetown outlet[3]

29

0.005

0.101

0.106

0.0027

0.18

93.4

80.9

2.9

McMillan Park outlet

18

0.004

0.077

0.081

0.0027

0.17

94.0

83.0

2.7

Filtered water

1

0.002

0.027

0.029

0.0000

0.19

94.9

84.0

2.8

1 Summary of daily samples of water.

2 Reservoir out of service from July 1st to September 13th, 1909.

3 Reservoir out of service from September 10th to October 4th, 1909.

No chemical determinations were made during February, March, April, and May, 1910, on account of the rearrangement of the laboratory and equipment.

TABLE 7—DAILY RESULTS AT PUMPING STATION.

(A)

Month.

MILLION GALLONS PUMPED:

Lift to filters.

Pressure at sandwasher pumps, per square inche.

COAL CONSUMED PER DAY IN TONS.

STATION DUTY, PER 100 LB. OF COAL CONSUMED.

To filters.

To sand washers.

Max.

Min.

Ave.

Max.

Min.

Ave.

Max.

Min.

Ave.

Max.

Min.

Ave.

1909.

July

76.16

57.65

64.05

1.140

0.298

0.730

24.18

110.0

13.4

8.4

10.8

67.8

52.3

61.4

August

69.31

54.44

61.42

0.629

0.157

0.441

22.18

110.0

12.4

8.0

10.1

64.2

49.5

56.6

September

66.02

52.82

69.32

0.831

0.207

0.572

22.26

110.0

12.7

8.7

10.5

61.0

48.9

55.1

October

78.50

48.12

59.18

0.761

0.060

0.467

21.84

110.0

13.4

8.0

10.3

59.6

49.1

53.6

November

64.92

49.83

55.25

0.468

0.141

0.272

20.49

110.0

11.3

7.9

9.2

55.6

45.7

51.1

December

67.83

48.32

56.77

0.307

0.039

0.174

20.54

110.0

10.3

8.5

9.5

61.0

45.4

50.4

1910.

January

70.04

51.02

62.49

0.499

0.008

0.156

22.43

110.0

12.7

9.1

10.4

59.6

49.8

54.9

February

70.79

55.19

60.28

0.284

0.041

0.173

21.44

112.3

12.3

8.7

10.2

57.4

44.8

51.5

March

59.11

51.64

56.04

0.409

0.063

0.171

19.76

120.0

10.5

7.8

9.2

53.2

45.2

49.8

April

66.53

53.79

58.32

0.715

0.167

0.474

20.78

120.0

11.1

8.1

9.7

58.7

47.2

53.7

May

61.93

54.55

57.76

0.525

0.059

0.251

20.30

120.0

10.1

7.4

8.8

60.7

48.1

54.9

June

70.49

50.42

58.37

0.281

0.124

0.207

21.19

117.3

12.3

7.4

9.1

60.1

49.9

54.4

Fiscal years:

1909-10

78.50

48.12

59.19

1.140

0.008

0.373

21.45

113.3

13.4

7.4

9.8

67.8

44.8

54.0

1905-06[1]

80.59

57.18

66.07

2.062

0.089

0.747

21.71

107.4

14.8

6.4

8.9

79.6

48.2

62.8

1906-07

80.29

57.44

66.89

2.120

0.023

0.580

21.60

120.8

15.0

7.0

10.0

71.6

46.5

58.6

1907-08

80.38

54.35

64.91

0.735

0.017

0.347

22.20

125.0

12.0

7.2

9.6

70.7

51.3

60.3

1908-09

78.93

47.83

61.47

0.875

0.060

0.453

22.52

122.3

13.2

7.0

10.0

74.0

45.7

57.7

TABLE 7—(Continued.)

(B)

Fiscal Year.

Name of coal used.

Cost per ton.

Duty per 100 lb. of coal consumed.

Cost of coal per 1,000,000 ft-lb. of work performed.

1905‑06

George's Creek Big Vein

$3.34

62.8

$0.00238

1906‑07

George's Creek Big Vein

3.43

58.6

0.00261

1907‑08

George's Creek Big Vein

3.75

60.3

0.00278

1908‑09

Orenda

3.47

57.7

0.00268

1909‑10

Orenda

3.15[2]

54.0

0.00255

1 Raw water shut off from city supply on October 5th.

2 Corrected for increase or decrease in ash and British thermal units, as determined by United States Geological Survey.

TABLE 8.—AVERAGE CONSUMPTION OF WATER FOR TWENTY-FOUR HOURS, PER MILLION GALLONS.

Month.

FISCAL YEARS.

1903.

1904.

1905.

1906.

1907.

1908.

1909.

1910.

July

59.80

61.50

63.20

69.80

69.18

68.64

71.08

64.05

August

59.00

59.70

67.70

71.40

68.03

67.74

68.14

61.42

September

56.50

61.10

67.90

71.30

69.82

68.93

65.83

60.32

October

58.70

59.10

63.90

68.40

69.14

66.46

65.89

59.18

November

54.70

58.60

62.10

66.10

65.51

61.54

60.06

55.25

December

60.70

60.10

70.30

67.20

65.71

62.29

57.99

56.77

January

60.10

65.30

75.10

65.30

67.62

63.36

57.72

62.49

February

59.30

67.80

86.00

68.70

74.68

68.17

55.42

60.28

March

55.30

60.00

67.60

64.30

64.23

59.63

55.31

56.04

April

55.10

57.20

63.10

62.70

63.45

61.51

58.19

58.32

May

57.70

60.80

66.30

65.60

62.47

62.96

59.25

57.76

June

59.50

62.30

70.60

67.80

63.53

67.96

60.12

58.37

Average

58.03

61.10

68.70

67.40

66.90

64.91

61.47

59.19

The length of runs, depth of scraping, etc., after the scraping or raking, are shown in Tables 10 and 11.

Sand Handling.—For the first three years of operation, the sand was carried from the sand bins in carts and dumped through the numerous manholes of the filters on chutes which could be revolved in various directions, in order to facilitate the spreading of the sand evenly over the surface of the filter.

About a year ago, however, this method was changed, by substituting sand ejectors for the carts. By this method, an ejector is either attached to, or placed directly under, the outlet gate of the sand bin, the gate is opened, and the ejector is started. From this ejector, the sand is carried back through the line of 4‑in. fixed pipe, and one or more lengths of 3‑in. hose, to the point of discharge in the filter bed which is being re‑sanded.

TABLE 9.

(A) NUMBER OF DEATHS FROM TYPHOID FEVER, BY MONTHS, IN THE DISTRICT OF COLUMBIA FOR THE LAST FOURTEEN FISCAL YEARS.

Fiscal year.

July.

August.

September.

October.

November.

December.

January.

February.

March.

April.

May.

June.

Total.

1896‑97

8

15

25

25

18

16

13

4

4

4

6

9

147

1897‑98

10

16

18

10

9

18

8

4

2

9

6

20

130

1898‑99

24

22

22

28

21

16

10

4

7

6

3

6

169

1899‑1900

9

38

30

28

27

26

17

6

8

10

5

12

193

1901‑02

16

33

28

21

22

16

19

8

12

9

13

9

206

1902‑03

21

39

25

32

19

20

9

5

9

6

6

3

194

1903‑04

17

26

18

19

8

14

5

5

6

10

8

8

144

1904‑05

16

22

25

14

11

9

11

1

5

7

1

3

125

1905‑06[1]

15

30

23

26

14

6

6

4

5

4

10

9

152

1906‑07

21

32

21

25

17

4

7

6

4

6

7

2

152

1907‑08

10

18

17

19

11

7

4

1

1

8

8

3

107

1908‑09

15

13

23

17

16

13

16

8

3

8

7

7

146

1909‑10

12

12

17

12

12

2

3

4

7

5

5

4

95

Average

15.3

25.5

22.9

21.5

16.6

13.1

9.6

4.4

5.8

6.7

6.4

7.5

155.4

TABLE 9—(Continued.)

(B) NUMBER OF DEATHS FROM TYPHOID FEVER REDUCED TO DEATH RATES PER 100,000 INHABITANTS PER YEAR.

Fiscal year.

July.

August.

September.

October.

November.

December.

January.

February.

March.

April.

May.

June.

Annual death rate.

1896‑97

35

65

109

109

78

70

56

17

17

17

26

39

53

1897-98

43

69

78

43

39

78

31

17

8

38

25

85

46

1898-99

102

93

93

119

89

68

42

17

29

25

12

26

59

1899‑1900

37

158

125

116

112

108

69

24

33

41

20

49

74

1900-01

82

167

118

102

114

69

28

8

32

8

16

40

65

1901-02

64

132

112

84

88

64

75

31

47

35

51

35

68

1902-03

83

153

98

126

75

79

35

19

35

23

23

12

63

1903-04

66

100

69

73

31

54

19

19

23

38

30

30

46

1904-05

61

83

95

53

42

34

41

4

19

26

4

11

39

1905-06

56

111

85

97

52

22

22

15

18

15

36

33

47

1906-07

69

105

69

82

56

13

24

20

13

20

24

7

42

1907-08

35

64

60

67

39

25

14

4

4

28

28

11

32

1908-09

53

45

80

60

56

45

56

28

10

28

24

24

43

1909-10

42

42

60

42

42

7

11

14

24

17

17

14

28

Average monthly death rate.

59

99

89

84

65

53

38

24

22

26

24

30

...

1 Filtered water supplied since October, 1905.

FIGURE 3—WASHINGTON AQUEDUCT, D. C., FILTRATION PLANT. SAND HANDLING, SYSTEM.

FIGURE 4—WASHINGTON AQUEDUCT, D. C., FILTRATION PLANT. WASHER SAND‑HANDLING, SYSTEM.

FIGURE 5—WASHINGTON AQUEDUCT, D. C., FILTRATION PLAN. EJECTOR SAND‑HANDLING, SYSTEM.

TABLE 10—PERIODS OF OPERATION, AND QUANTITIES FILTERED.

Month.

Number of filter runs ended after:

NUMBER OF DAYS SINCE PREVIOUS:

MILLION GALLONS FILTERED SINCE PREVIOUS:

Scraping.

Raking

Scraping.

Raking

Scraping.

Raking.

Max.

Min.

Ave.

Max.

Min.

Ave.

Max.

Min.

Ave.

Max.

Min.

Ave.

1909.

July

14

0

89

44

67.4

0

0

0

229.01

106.27

163.289

0

0

0

August

8

0

74

51

60.4

0

0

0

175.54

124.94

152.581

0

0

0

September

13

0

98

53

68.3

0

0

0

237.52

114.37

161.702

0

0

0

October

18

5

81

32

59.9

43

33

39.4

206.09

78.78

132.359

96.50

71.51

82.708

November

8

2

79

44

53.4

47

37

42.0

168.19

82.32

112.603

99.00

90.23

94.615

December

3

4

62

61

61.3

63

50

57.3

135.77

128.33

132.647

144.35

106.11

125.940

1910.

January

9

4

95

79

88.0

88

72

77.0

204.38

146.58

178.461

189.48

152.33

170.735

February

1

4

99

99

99.0

93

51

71.0

205.73

205.73

205.730

192.98

118.85

158.890

March

3

4

120

110

113.7

108

101

104.3

275.96

257.36

265.493

249.68

224.49

238.993

April

10

12

126

62

84.8

129

21

65.3

295.96

104.13

181.972

307.57

45.22

142.448

May

3

2

86

38

69.7

55

32

43.5

186.64

81.66

150.230

102.15

69.79

85.978

June

13

2

100

61

79.7

129

78

103.5

213.70

130.85

171.059

181.25

167.84

174.540

Year 1909‑10

103

39

126

32

71.1

129

21

66.6

295.96

81.66

159.151

307.57

45.22

143.832

Fiscal years:

1905-06

71

0

195

38

91.1

0

0

0

497.45

116.66

240.379

0

0

0

1906-07

101

4

199

24

77.0

32

14

21.7

466.12

69.76

220.693

103.28

32.13

76.870

1907-08

143

77

180

11

54.9

63

7

28.6

477.19

28.20

146.912

165.25

17.08

75.775

1908-09

128

50

135

11

49.9

93

13

34.2

298.08

39.26

125.617

244.19

41.41

88.439

In re‑sanding a filter, it is first filled with water to the proposed depth of the sand layer. The outlet end of the hose is connected to a 3‑in. pipe which is supported on a boat, and the sand is discharged through this pipe at the point required. Work is first begun at the far end of the filter, and it is gradually filled by swinging the boat from side to side and backing it by degrees to the front end.

At first it was feared that a small quantity of mud would be deposited on the surface of the old sand, and that this mud would ultimately cause subsurface clogging. For this reason, when this method was first adopted, a man was required to rake the sand very thoroughly in front of the discharge. Later, it was found that by giving the end of the discharge pipe a slope of about 45° downward from the horizontal, the force of the current of sand and water could be depended on to cut the old surface of sand to any required depth, and move it ahead together with the new sand, thus completely breaking up the possible mud layer between the old and new sand layers. After having used this method almost exclusively for 15 months, in which time eleven filters have been re‑sanded, and 24,531 cu. yd. of sand have been replaced, there seems to be no indication of an increased initial loss of head. The sand is very compact, and has no apparent tendency to separate into different sizes. The general appearance is similar to that of very fine sand on the seashore. The filters re‑sanded in this way have been considerably more efficient than those in which the sand was replaced with carts, and as yet, no harmful results have been noted. The rate at which the sand is replaced is shown in Table  12, and the cost of labor for sand handling is given in detail in Table 14, which shows that quite a perceptible saving has been effected by the hydraulic method.

The figures showing the cost for sand handling do not include any charge for the quantity of water used, that item having been carried on the pumping‑station account.

TABLE 11—QUANTITIES OF SAND REMOVED.

Month.

NO. OF FILTERS SCRAPED WHEN LAST TREATMENT WAS:

CUBIC YARDS WHEN LAST TREATMENT WAS:

DEPTH, IN INCHES, WHEN LAST TREATMENT WAS:

Scraping.

Raking.

Scraping.

Raking.

Scraping.

Raking.

Max.

Min.

Ave.

Max.

Min.

Ave.

Max.

Min.

Ave.

Max.

Min.

Ave.

1909.

July

14

0

338

121

190.6

0

0

0

2.51

0.90

1.415

0

0

0

August

8

0

356

149

218.5

0

0

0

2.65

1.11

1.631

0

0

0

September

8

0

524

97

178.6

0

0

0

3.90

0.72

1.330

0

0

0

October

9

5

150

93

115.8

301

121

169.0

1.12

0.69

0.862

2.24

0.90

1.256

November

2

2

134

88

111.0

132

81

106.5

1.00

0.65

0.825

0.98

0.60

0.790

December

0

2

0

0

0

133

126

129.5

0

0

0

0.99

0.94

0.965

1910.

January

2

4

155

112

133.5

195

121

147.8

1.15

0.83

0.990

1.45

0.90

1.100

February

0

4

0

0

0

390

160

225.8

0

0

0

2.90

1.19

1.678

March

1

4

489

489

489.0

262

179

214.3

3.64

3.64

3.640

1.95

1.33

1.593

April

4

12

172

84

119.3

230

146

178.8

1.28

0.62

0.885

1.71

1.09

1.331

May

1

2

320

320

320.0

249

241

245.0

2.38

2.38

2.380

1.85

1.79

1.820

June

0

2

0

0

0

203

190

196.5

0

0

0

1.51

1.41

1.460

Year 1909-10

49

37

524

84

176.7

390

81

181.0

3.90

0.62

1.314

2.90

0.60

1.373

Fiscal Years:

1905-06

71

0

600

71

250.0

0

0

0

4.47

0.53

1.799

0

0

0

1906-07

94

2

536

52

259.0

398

276

337.0

4.00

0.56

1.931

2.95

2.05

2.500

1907-08

81

53

527

46

190.2

411

35

118.4

3.92

0.21

1.507

3.06

0.21

0.881

1908-09

92

50

580

55

169.5

472

81

177.5

4.31

0.41

1.259

3.51

0.60

1.317

TABLE 12—RATES OF SAND HANDLING.

Date

SAND REMOVED FROM FILTERS.

SAND REPLACED IN FILTERS.

Ejector hours.

Cubic yards of sand removed

Average rate in cubic yards per hour

Ejector hours.

Cubic yards of sand removed

Average rate in cubic yards per hour

1906.

April

49

253

5.2

...

...

...

May

380

2,511

6.6

...

...

...

June

567

3,280

5.8

...

...

...

July

931

5,376

5.8

...

...

...

August

105

533

5.1

...

...

...

September

315

1,892

6.0

...

...

...

October

1,067

5,173

5.8

...

...

...

November

168

935

5.6

...

...

...

December

203

1,073

5.3

...

...

...

1907.

January

399

2,974

7.3

...

...

...

February

140

1,139

8.1

...

...

...

March

115

878

7.6

...

...

...

April

427

3,103

7.3

...

...

...

May

133

939

7.0

...

...

...

June

105

674

6.4

...

...

...

July

7

46

6.6

...

...

...

August

90

574

6.4

...

...

...

September

306

1,396

6.5

...

...

...

October

273

1,701

6.2

...

...

...

November

202

1,258

6.8

...

...

...

December

304

2,138

5.9

...

...

...

1908.

January

546

3,708

6.8

...

...

...

February

98

776

7.9

...

...

...

March

315

2,832

9.0

...

...

...

April

469

3,775

8.1

...

...

...

May

182

1,414

7.8

...

...

...

June

280

2,057

7.4

...

...

...

July

280-1/2

2,683

9.6

...

...

...

August

327-1/2

2,808

8.6

...

...

...

September

402

3,371

8.4

...

...

...

October

308

2,696

8.7

...

...

...

November

47-1/2

333

7.0

...

...

...

December

153-3/4

1,268

8.3

...

...

...

1909.

January

119-1/2

1,055

8.8

...

...

...

February

161-1/2

1,479

9.2

...

...

...

March

144

1,465

10.2

...

...

...

April

214-3/4

2,260

10.5

188

2,405

12.8

May

219-3/4

2,223

10.1

190

2,196

11.5

June

355

3,096

8.7

243

3,054

12.6

July

312-1/4

2,707

8.7

425-1/2

4,050

9.5

August

218-3/4

1,955

9.0

64-1/2

620

9.6

September

172-1/2

1,360

7.9

408

2,842

7.0

October

203

1,870

9.2

261-1/4

2,350

9.0

November

54

397

7.4

0

0

...

December

62

382

6.2

0

0

...

1910.

January

104

703

6.8

0

0

...

February

106-1/2

1,058

9.9

28-1/4

371

13.1

March

98

985

10.0

72

1,008

14.0

April

268-3/4

2,852

10.7

134-1/4

2,159

16.1

May

58-3/4

693

11.8

171-3/4

3,042

17.7

June

58-3/4

642

10.9

9-3/4

166

17.0

The cost for pumping water for sand handling, including all labor, materials, and repairs, amounts to $0.06 per cu. yd. of sand ejected and washed, and $0.03 per cu. yd. for replacing.

In addition to the water used for carrying the sand which is being replaced, it is customary to keep a slight upward flow in the filter, thus using about 500,000 gal. of filtered water per day for this purpose. Assuming the value of this water to be the total cost for pumping, filtering, etc., or $3.80 per 1,000,000 gal., the cost per cubic yard of sand replaced would be about $0.02 when one ejector is used, and $0.01 when two are in operation.

It is not considered absolutely necessary to have an upward flow of water in the filter which is being re‑sanded, and it is not always done. It was used, however, as an additional safeguard against the formation of a stratum of mud between the old and new layers of sand while the hydraulic method was in an experimental stage.

The quantities of sand removed from the filters per scraping and the rates of sand handling are shown in Tables 11 and 12.

Cost of Operation.—It is frequently difficult to compare the relative cost of corresponding items for different plants, because of the different methods of dividing the cost and the varying opinions of the officials as to what should properly be charged to each item.

In order that the data may be in sufficient detail to permit it to be rearranged to compare with other plants, a list of employees and charges for supplies is given in Table 13. This list accounts for the entire appropriation for the care and maintenance of the filtration plant, including pumping the water to the filters, parking and caring for the grounds, buildings, roads, sidewalks, etc. The cost for the various items per million gallons pumped to the filters is shown in Table 14, and the cost per cubic yard of sand handled in Table 15.

Preliminary Treatment.—Before the present filtration plant was designed, Rudolph Hering, George W. Fuller, and Allen Hazen, Members, Am. Soc. C. E., made an investigation and report. This report was dated February 18th, 1901, and contained the following paragraph:

"In consideration of the full evidence, we recommend the construction of a complete system of slow or sand filters, with such auxiliary works as may be necessary for preliminary sedimentation, and the use of a coagulant for part of the time. There is no reason to believe that the use of this coagulant will in any degree affect the wholesomeness of the water."

Notwithstanding this opinion, considerable prejudice existed among the citizens of Washington against the use of a coagulant, and, as finally passed, the bill providing for the construction of the filters did not include an appropriation for the coagulant.

TABLE 13—LIST OF EMPLOYEES, RATES OF PAY, AND APPROXIMATE COST FOR SUPPLIES.

1 Superintendent

$3,000.00

1 Chief Chemist and Assistant Superintendent

2,100.00

1 First Assistant Chemist

1,500.00

1 Second Assistant Chemist

1,000.00

1 Stenographer and Clerk

1,200.00

1 Surveyor

1,200.00

1 Laboratory Helper

720.00

1 Janitor

600.00

1 Chief Steam Engineer

1,800.00

1 First Assistant Steam Engineer

1,440.00

1 Second Assistant Steam Engineer

1,080.00

3 Oilers, at $900 each

2,700.00

3 Firemen, at $900 each

2,700.00

3 Laborers, at $540 each

1,620.00

1 Filter Foreman

1,200.00

2 Foremen, at $900 each

1,800.00

1 Timekeeper

900.00

3 Watchmen and Gauge Tenders, at $900 each

2,700.00

1 Machinist

1,140.00

1 Blacksmith

900.00

1 Storekeeper

900.00

1 Painter

900.00

1 Mechanic

900.00

1 Electrician

900.00

4 Skilled Laborers at $600 each

2,400.00

1 Watchman and Special Officer

900.00

1 Recorder

720.00

27 Laborers, at $1.50 per day for 300 days

12,150.00

3 Teams, at $2.00 per day for 200 days

1,200.00

Laboratory and office supplies

2,700.00

Filter supplies, tools, hose, repair of roads, parks, shrubs, etc.

8,820.00

Pumping station supplies, oil, waste, packing, repairs, etc.

3,570.00

3,600 tons of coal, at $3.15 per ton

11,340.00

Charges in U. S. Engineer Office, labor

2,900.00

Charges in U. S. Engineer Office, materials

400.00

Total

$82,000.00

The results obtained from operating the filters being such as to justify the conclusions in the report referred to, an experimental plant was constructed for the purpose of studying the efficiency of various methods of preliminary treatment of the water. This plant consisted of three cylindrical concrete filter tanks, each 10 ft. in diameter. These tanks were filled with the layers of gravel and sand necessary to make them represent as accurately as possible the large slow sand units of the main filtration plant. Means were also provided for giving a preliminary treatment to the water supplying each of these experimental slow sand filters. In two cases, the preliminary treatment was rapid filtration, while the third consisted of sedimentation and coagulation. The sedimentation tank was of sufficient size, when compared with the area of the experimental slow sand filter, to represent the Georgetown and McMillan Park Reservoirs when used in connection with the large filters. The first preliminary filter was very similar in construction and operation to a mechanical filter. The sand for this filter was taken from the main filters, and, consequently, was finer than is generally used in mechanical filters. The second preliminary filter was a Maignen scrubber. It consisted of a cylindrical concrete tank, 4 ft. in diameter and 8‑1/2 ft. deep, which contained 12 in. of cobble‑stones on the bottom, then, successively, 12 in. of egg‑size coke, 12 in. of stove‑size coke, 24 in. of nut‑size coke, and 24 in. of sponge clippings as the final or top layer.

TABLE 14—COST PER MILLION GALLONS FILTERED.

(A) LABOR.

Month.

Office and laboratory.

Pumping station.

FILTER OPERATIONS:

Parking (care of grounds).

Experimental filters.

Main office.

Total.

Sand handling.

Repairs, etc.

1909.

July

$0.73

$0.57

$0.86

...

$0.31

...

$0.15

$2.62

August

0.75

0.64

0.59

...

0.71

...

0.14

2.83

September

0.83

0.67

0.80

...

0.51

...

0.17

2.98

October

0.72

0.66

0.73

...

0.34

...

0.08

2.53

November

0.87

0.76

0.42

...

0.38

...

0.18

2.61

December

0.90

0.69

0.27

...

0.40

...

0.12

2.38

1910.

January

0.81

0.63

0.33

...

0.14

...

0.10

2.01

February

0.94

0.74

0.35

$0.07

0.11

...

0.16

2.37

March

0.92

0.81

0.30

0.07

0.18

...

0.13

2.41

April

0.93

0.83

0.49

0.03

0.36

...

0.13

2.77

May

0.86

0.72

0.36

0.03

0.55

...

0.18

2.70

June

0.88

0.67

0.38

...

0.38

...

0.12

2.43

Average

0.84

0.70

0.27

[1]0.25

0.36

...

0.14

2.56

Fiscal years:

1905‑1906

0.45

0.45

0.47

0.02

0.01

...

0.09

1.49

1906‑1907

0.57

0.57

0.58

0.21

0.07

$0.03

0.04

2.07

1907‑1908

0.70

0.56

0.42

0.32

0.15

0.09

0.09

2.36

1908‑1909

0.72

0.61

0.41

0.34

0.22

0.01

0.13

2.44

TABLE 14—(Continued.)

(B) MATERIALS.

Month.

Office and laboratory.

Pumping station.

FILTER OPERATIONS:

Parking (care of grounds).

Experimental filters.

Main office.

Total.

Sand handling.

Repairs, etc.

1909.

July

...

...

$0.01

...

...

...

...

$0.01

August

$0.01

...

...

...

$0.07

...

$0.01

0.09

September

0.05

$0.31

0.04

...

0.01

...

0.03

0.44

October

0.08

0.11

0.13

...

0.46

...

0.02

0.80

November

0.13

0.78

0.10

...

0.34

...

0.02

1.37

December

0.03

0.17

0.05

...

0.01

...

0.05

0.31

1910.

January

0.12

0.74

0.14

...

0.01

...

...

1.01

February

0.07

1.88

0.18

...

0.01

...

0.01

2.15

March

0.26

0.28

0.01

...

...

...

...

0.55

April

0.18

1.22

0.10

...

0.29

...

0.02

1.81

May

0.06

0.72

0.02

...

0.11

...

0.02

0.98

June

0.54

2.23

...

[2]$2.16

0.46

...

0.04

5.43

Average

0.13

0.69

0.02

[3]0.21

0.17

...

0.02

1.24

Fiscal years.

1905‑1906

0.04

0.59

0.02

...

...

...

...

0.65

1906‑1907

0.03

0.67

0.08

0.20

0.02

...

...

1.00

1907‑1908

0.05

0.54

0.04

0.07

0.06

...

0.01

0.77

1908‑1909

0.10

0.69

0.05

0.18

0.18

...

0.02

1.22

1 $0.02 for new sand-handling system.

2 $2.02 for new sand-handling system.

3 $0.16 for new sand-handling system.

TABLE 14—(Continued.)

(C) TOTALS.

Month.

Office and laboratory.

Pumping station.

FILTER OPERATIONS:

Parking (care of grounds).

Experimental filters.

Main office.

Total.

Sand handling.

Repairs, etc.

1909.

July

$0.73

$0.57

$0.87

...

$0.31

...

$0.15

$2.63

August

0.76

0.64

0.59

...

0.78

...

0.15

2.92

September

0.88

0.98

0.84

...

0.52

...

0.20

3.42

October

0.80

0.77

0.86

...

0.80

...

0.10

3.33

November

1.00

1.54

0.52

...

0.72

...

0.20

3.98

December

0.93

0.86

0.32

...

0.41

...

0.17

2.69

1910.

January

0.93

1.37

0.47

...

0.15

...

0.10

3.02

February

1.01

2.62

0.53

$0.07

0.12

...

0.17

4.52

March

1.18

1.09

0.31

0.07

0.18

...

0.13

2.96

April

1.11

2.05

0.59

0.03

0.65

...

0.15

4.58

May

0.92

1.44

0.38

0.03

0.66

...

0.20

3.63

June

1.42

2.90

0.38

2.16

0.84

...

0.16

7.86

Average.

0.97

1.39

0.29

0.46

0.58

...

0.16

3.80

Fiscal years:

1905‑1906

0.49

1.04

0.49

0.02

0.01

...

0.09

2.14

1906‑1907

0.60

1.24

0.66

0.41

0.09

$0.03

0.04

3.07

1907‑1908

0.75

1.13

0.46

0.39

0.21

0.09

0.10

3.13

1908‑1909

0.82

1.30

0.46

0.52

0.40

0.01

0.15

3.66

The two preliminary filters were operated at a rate of about 50,000,000 gal. per acre per day, and the three slow sand filters at rates of from 3,000,000 to 4,000,000 gal. per day.

This plant was put in service during the early part of February, 1907, and was kept in practically continuous operation until the end of July, 1908.

FIGURE 6—WASHINGTON AQUEDUCT, D. C.

EXPERIMENTAL FILTERS BELOW DALECARLIA RESERVOIR COAGULATING BASINS AND APPARATUS.

TABLE 15—AVERAGE COST FOR LABOR FOR SAND HANDLING.

(A) PER MILLION GALLONS PUMPED TO FILTER.

Month.

Scraping.

Ejecting.

Washing.

Smoothing.

Raking.

Re-Sanding.

Total.

1909.

July

$0.10

$0.21

$0.03

$0.02

...

$0.21

$0.57

August

0.07

0.16

0.03

0.01

...

0.04

0.31

September

0.05

0.13

0.02

0.01

$0.01

0.27

0.49

October

0.06

0.15

0.03

0.01

0.02

0.12

0.39

November

0.02

0.06

...

...

0.02

...

0.70

December

0.02

0.04

0.01

...

0.01

0.01

0.09

1910.

January

0.04

0.07

...

0.01

0.02

...

0.14

February

0.04

0.10

...

0.01

...

0.02

0.17

March

0.04

0.06

...

0.01

0.01

0.05

0.17

April

0.10

0.15

0.04

0.01

0.02

0.06

0.38

May

0.02

0.03

0.01

...

0.01

0.11

0.18

June

0.02

0.04

...

...

0.02

0.01

0.09

Average

0.05

0.10

0.01

0.01

0.01

0.08

0.26

Fiscal years:

1905‑06

0.06

0.29

0.02

0.06

...

0.04

0.47

1906‑07

0.07

0.20

0.05

0.02

...

0.24

0.58

1907‑08

0.09

0.14

0.03

0.01

0.02

0.13

0.42

1908‑09

0.07

0.15

0.03

0.01

0.01

0.14

0.41

TABLE 15—(Continued.)

(B) PER CUBIC YARD OF SAND.

Month.

Scraping.

Ejecting.

Washing.

Smoothing.

Raking.

Re-Sanding.

Total.

1909.

July

$0.08

$0.15

$0.03

$0.01

...

$0.10

$0.37

August

0.07

0.15

0.03

0.01

...

0.11

0.37

September

0.07

0.17

0.03

0.01

...

0.17

0.45

October

0.06

0.15

0.03

0.01

...

0.09

0.34

November

0.10

0.23

0.02

0.02

...

...

0.37

December

0.12

0.25

0.04

0.02

...

0.08

0.51

1910.

January

0.10

0.19

...

0.02

...

...

0.31

February

0.07

0.15

...

0.01

...

0.09

0.32

March

0.06

0.11

...

0.02

...

0.08

0.27

April

0.07

0.09

0.03

0.01

...

0.05

0.25

May

0.06

0.09

0.03

0.01

...

0.06

0.25

June

0.06

0.12

...

0.01

...

0.10

0.29

Average

0.07

0.14

0.02

0.01

...

0.10

0.34

Fiscal years:

1905‛06

0.07

0.35

0.04

0.07

...

0.14

0.67

1906‑07

0.06

0.19

0.03

0.02

...

0.17

0.47

1907‑08

0.09

0.15

0.03

0.01

...

0.14

0.42

1908‑09

0.06

0.14

0.03

0.01

...

0.13

0.37

For convenience in referring to the different systems, the combined rapid and slow sand filter will be designated as Filter Plant No. 1, the combined Maignen scrubber and slow sand filter as Filter Plant No. 2, and the combined coagulating basin and slow sand basin as Filter Plant No. 3.

The length of run of Filter Plant No. 1 was relatively long at first. The rapid rate of filtration, however, tended to carry the clay, which was suspended in the applied water, to a considerable depth in the filtering material, so that the runs gradually decreased in length until they were reduced to about three days. Unfortunately, it was necessary to use unfiltered water for washing, which, together with the great penetration from the applied water, finally made it necessary to remove all the filtering materials, and wash them.

Although this preliminary filter was operated at a high rate, its efficiency was quite satisfactory. In fact, at times when the applied water was comparatively good, very little work was left for the slow sand filter. At times of high turbidity, however, some of the exceedingly fine mud in the applied water passed through this filter, as well as the slow sand filter connected with it, and it proved to be absolutely impossible to produce a clear effluent at all times with this combination.

Filter Plant No. 2 proved more economical and convenient in operation, but somewhat less efficient than Filter Plant No. 1. Neither filter could be depended on to give a clear effluent when the applied water was turbid.

In the operation of Filter Plant No. 3, sulphate of alumina was used when the applied water contained too much turbidity to be treated satisfactorily by slow sand filters.

When the water was comparatively clear, either one of the three systems, or slow sand filtration alone, was entirely satisfactory. At times of high turbidity, however, Filter Plant No. 3 was the only one which could be depended on to produce a clear effluent.

A fair comparison between the results of the three systems when treating turbid water in January, 1908, is given in Table 16.

Table 16 shows very clearly that neither Filter Plant No. 1 nor No. 2 would prove at all satisfactory when treating turbid water, while No. 3 could be depended on under all conditions. The results of operation are shown in detail in Tables 17, 18, and 19. It will be noticed in Table 17, that on March 10th, 1908, Filter Plant No. 1 was put out of service and a Puech system of preliminary filters was substituted for it.

The Puech preliminary filters consisted of five units containing gravel of varying sizes through which the water was filtered successively before it was finally applied to the final slow sand filter. A general idea of this system may be obtained by referring to Figure 8.

TABLE 16—TURBIDITY RESULTS WITH EXPERIMENTAL FILTERS, DURING PERIOD OF HIGH TURBIDITY, JANUARY, 1908.

Date.

Raw water.

Filter No. 1

Filter No. 2

Filter No. 3

Effluent preliminary filter.

Effluent sand filter.

Effluent preliminary filter.

Effluent sand filter.

Effluent coagulant basin.

Effluent sand filter.

January 12th

40

10

1

12

1

2

0

January 13th

110

45

2

51

2

2

0

January 14th

210

95

3

113

4

2

0

January 15th

325

190

12

222

15

3

0

January 16th

360

210

37

247

42

5

0

January 17th

242

122

24

147

26

6

0

January 18th

137

...

...

73

7

6

0

January 19th

117

40

12

cleaning

...

5

0

January 20th

72

31

6

sand filter

...

cleaning

0

January 21st

55

20

4

25

4

sand filter

...

January 22d

49

17

3

21

4

sand filter

...

January 23d

40

12

3

15

3

3

0

January 24th

40

11

3

13

3

3

0

It is unfortunate that this system was not in operation in January, 1908, when the water was cold and turbid. The results, however, indicate that it would be no more successful than either Filter Plant No. 1 or No. 2.

Experimental Rate Studies.—In September, 1908, an experimental plant consisting of six small filters was put in operation. The object of these experiments was to study the relative efficiencies and cost for the operation of slow sand filters when operated at different rates.

The units of the plant consisted of cylindrical galvanized‑iron tanks 4 ft. in diameter and 9 ft. high. The filter sand in these tanks was taken from the supply for the main filters. It was supported on gravel layers and supplied with under‑drains of suitable sizes for the proposed rate of flow in each case.

The units of the experimental plant were designated as Nos. 1, 2, 3, 4, 5, and 6, and it was the original intention to operate them at rates of 1,000,000, 3,000,000, 6,000,000, 10,000,000, 30,000,000, and 100,000,000 gal. per acre daily, respectively.

This schedule of rates was carried out in a general way with all the filters, with the exception of Nos. 5 and 6. For these, the rates were found to be higher than could be maintained for any great length of time, owing to the deeper penetration of the mud in the filter sand, which caused high initial losses of head, short runs, and deep scrapings. A rate of about 30,000,000 gal. was maintained in the case of Filter No. 5 from the time it was started on September 9th, 1908, until November 8th, 1909, when it was reduced to about 17,000,000 gal., which rate was maintained thereafter until the filter was shut down in February, 1910.

FIGURE 7—PLAN OF FILTER‑HOUSE AND EQUIPMENT.

In the case of Filter No. 6, it was found impossible to maintain a rate of 100,000,000 gal. for more than a very few days at a time. It was started at about this rate, however, at the beginning of each run, and kept as high as possible for the remainder of the time during the first seven runs. At the end of the seventh run, on October 17th, 1908, the filter was given a very deep scraping and re‑sanded.

FIGURE 8—DIAGRAMMATIC SKETCH SHOWING ARRANGEMENTS FOR TESTING "PUECH" SYSTEM OF WATER FILTRATION AT WASHINGTON D. C., U. S. A.

The layer of clean sand restored the original capacity, and the filter was operated as before, but with gradually decreasing rates until December, 1908, when the rate was reduced to about 40,000,000 gal. Even this lower rate was too high to be maintained without removing and replacing a large part of the sand. The rates, therefore, gradually decreased to about 23,000,000 gal. on March 13th, 1909, when the filter was again re‑sanded. After this re‑sanding the rate was reduced to about 20,000,000 gal., and the filter was operated at approximately that rate until it was again re‑sanded on November 13th, 1909, when the rate was again reduced to about 14,000,000 gal., which was maintained until the filter was put out of service on February 28th, 1910.

This experimental plant was in service from September, 1908, to the latter part of February, 1910, or for about 1‑1/2 years, and the leading results are summarized in Table 20.

TABLE 17—RECORD OF EXPERIMENTAL FILTER PLANT NO. 1.

Date.

Preliminary Filter.

Final Filter.

Turbidity.

Bacteria.

Rate, millions of gallons per acre daily.

Loss of head.

Rate, millions of gallons per acre daily.

Loss of head.

Applied water.

Effluent preliminary filter.

Effluent final filter.

Applied water.

Effluent preliminary filter.

Effluent final filter.

1907.

Feb.   8

19.40

0.71

3.10

0.17

...

...

...

1,100

2,000

2,500

Feb.   9

21.50

0.81

3.11

0.16

...

...

...

200

950

500

Feb. 10

20.60

0.95

3.04

0.14

...

...

...

...

...

...

Feb. 11

20.10

1.08

3.03

0.12

12

3

2

600

900

1,300

Feb. 12

19.80

1.23

3.02

0.13

14

4

2

650

650

650

Feb. 13

19.50

1.38

2.96

0.12

15

6

2

600

600

950

Feb. 14

21.20

1.67

3.21

0.11

15

4

2

650

700

800

Feb. 15

25.40

2.03

3.90

0.13

12

4

2

600

550

800

Feb. 16

25.00

2.23

3.89

0.12

14

3

2

850

550

500

Feb. 17

Shut down for changes in size of meter and piping.

Feb. 18

...

...

...

...

...

...

...

1,200

...

650

Feb. 21

38.60

1.59

3.93

0.18

20

4

2

1,800

1,100

700

Feb. 22

38.00

1.84

3.92

0.15

15

3

2

Holiday.

Feb. 23

42.10

2.36

3.95

0.14

20

5

2

1,600

600

220

Feb. 24

47.90

3.04

3.93

0.13

20

6

3

Sunday.

Feb. 25

Shut down change meter from outlet to inlet.

1,400

800

450

Feb. 27

...

2.24

...

0.13

17

6

3

700

550

280

Feb. 28

49.80

2.55

3.90

0.13

15

6

3

800

470

230

Mar.   1

50.00

2.90

3.93

0.13

15

5

3

650

450

140

Mar.   2

50.20

3.21

3.93

0.13

15

5

3

1,000

650

200

Mar.   3

38.80

3.09

3.89

0.13

31

8

3

Sunday.

Mar.   4

50.00

3.54

3.93

0.12

35

10

5

1,200

...

...

Mar.   5

50.00

4.01

3.90

0.13

135

39

8

13,000

3,700

600

Mar.   6

50.00

4.82

3.90

0.13

135

39

8

18,000

4,500

...

Mar.   7

50.00

5.89

3.90

0.13

102

34

6

24,000

5,000

2,000

Mar.   8

50.00

6.58

3.90

0.13

100

25

4

22,000

5,000

1,400

Mar.   9

50.00

7.21

3.93

0.13

90

25

4

24,000

4,000

650

Mar. 10

50.00

7.52

3.90

0.13

82

22

5

Sunday.

Washed.

Mar. 11

50.00

0.84

3.90

0.13

68

19

6

18,000

2,100

350

Mar. 12

50.00

0.95

3.96

0.13

46

19

4

11,000

6,000

310

Mar. 13

50.00

1.17

3.99

0.13

40

19

4

9,000

4,900

300

Mar. 14

50.00

1.53

4.01

0.13

39

17

4

5,500

1,300

130

Mar. 15

50.00

2.27

4.05

0.13

35

15

4

6,500

1,500

60

Mar. 16

50.00

3.08

4.03

0.13

60

20

4

5,000

1,200

100

Mar. 17

50.00

4.26

4.03

0.13

135

35

4

Sunday.

Mar. 18

50.00

5.65

4.00

0.13

170

49

7

9,000

1,200

95

Mar. 19

50.00

7.02

4.01

0.13

125

37

6

7,000

600

100

Washed.

Mar. 20

50.00

1.08

3.98

0.13

102

30

5

4,800

300

75

Mar. 21

50.00

1.23

3.98

0.12

125

32

4

8,500

1,000

85

Mar. 22

50.00

1.46

4.00

0.13

190

65

4

7,500

1,100

45

Mar. 23

50.00

1.76

3.99

0.13

180

65

6

7,500

600

55

Mar. 24

50.00

2.11

3.99

0.12

140

52

7

Sunday.

Mar. 25

50.00

2.46

4.00

0.11

88

30

5

4,400

500

85

Mar. 26

50.00

2.75

4.00

0.12

62

22

4

3,600

300

65

Mar. 27

50.00

3.04

4.08

0.13

47

18

4

2,200

160

60

Mar. 28

50.00

3.38

3.94

0.11

35

10

3

1,300

100

55

Mar. 29

50.00

3.70

4.00

0.11

26

8

3

700

80

29

Mar. 30

50.00

4.42

4.00

0.11

25

6

3

310

70

35

Mar. 31

50.00

5.25

3.99

0.11

21

5

2

Sunday.

Apr.   1

50.00

6.14

4.00

0.12

20

5

2

600

25

30

Washed.

Apr.   2

50.00

2.10

4.00

0.12

24

5

2

270

28

32

Apr.   3

50.00

3.00

4.00

0.12

24

5

2

460

26

43

Apr.   4

50.00

4.01

4.00

0.12

20

5

2

280

20

26

Apr.   5

50.00

5.15

4.00

0.12

20

4

2

450

37

41

Washed.

Apr.   6

50.00

O.76

3.59

0.12

20

4

2

320

6

34

Apr.   7

50.00

O.99

3.47

0.12

20

4

2

Sunday.

Apr.   8

50.00

1.39

4.03

0.14

18

3

2

330

10

20

Apr.   9

50.00

2.04

4.01

0.13

18

3

2

140

9

35

Apr. 10

50.00

3.03

4.02

0.13

30

2

1

750

43

29

Apr. 11

50.00

4.45

4.02

0.14

66

1

1

4,000

900

26

Apr. 12

50.00

6.14

4.01

0.13

72

11

2

14,000

1700

41

Washed.

Apr. 13

50.00

0.95

4.00

0.14

80

21

2

13,000

1300

70

Apr. 14

50.00

1.18

4.00

0.13

77

25

3

Sunday.

Apr. 15

50.00

1.57

4.00

0.14

62

21

3

7,000

380

55

Apr. 16

50.00

2.33

4.00

0.15

47

20

3

3,600

160

33

Apr. 17

50.00

3.33

4.00

0.15

39

15

2

1,600

70

39

Apr. 18

50.00

4.81

4.00

0.16

30

10

2

1,810

130

34

Apr. 19

50.00

6.29

3.99

0.16

25

7

2

790

50

32

Washed.

Apr. 20

50.00

0.93

4.01

0.16

20

5

2

540

24

28

Apr. 21

50.00

1.36

3.97

0.16

20

3

2

Sunday.

Apr. 22

50.00

2.22

4.02

0.16

18

2

1

235

15

28

Apr. 23

50.00

3.33

3.99

0.14

15

2

1

170

14

16

Apr. 24

50.00

4.78

3.97

0.15

19

1

1

150

32

14

Apr. 25

50.00

6.43

3.90

0.15

34

1

1

700

20

18

Washed.

Apr. 26

50.00

O.97

3.97

0.14

46

2

1

1,200

16

16

Apr. 27

50.00

2.37

4.00

0.14

52

3

1

1,700

25

17

Apr. 28

50.00

5.33

3.99

0.14

45

4

1

Sunday.

Washed.

Apr. 29

50.00

0.81

3.99

0.14

44

5

1

600

16

17

Apr. 30

50.00

1.75

3.99

0.14

39

6

1

550

27

12

May   1

50.00

0.80

3.99

0.14

31

5

1

500

24

11

Washed.

May   2

50.00

1.13

4.00

0.14

24

4

1

500

12

16

May   3

50.00

2.09

4.00

0.14

19

3

1

280

30

25

May   4

50.00

3.80

4.00

0.14

16

2

1

400

20

12

May   5

50.00

5.38

4.00

0.14

15

1

1

Sunday.

Washed.

May   6

50.00

0.91

3.90

0.14

13

1

1

390

50

40

May   7

50.00

1.56

3.90

0.14

12

1

1

190

19

80

May   8

50.00

2.25

3.99

0.14

10

1

1

...

...

...

May   9

50.00

3.37

4.00

0.14

10

1

1

390

21

38

May 10

50.00

5.16

4.00

0.14

10

1

1

300

14

13

Washed.

May 11

50.00

1.03

4.00

0.14

12

1

1

390

13

12

May 12

50.00

1.89

4.00

0.14

17

1

1

Sunday.

May 13

50.00

3.82

4.00

0.14

35

2

1

600

33

15

May 14

50.00

6.31

4.00

0.14

39

3

1

500

27

7

Washed.

May 15

50.00

0.85

4.00

0.14

17

2

1

500

20

29

May 16

50.00

1.42

3.99

0.14

24

2

1

290

19

40

May 17

50.00

2.47

3.99

0.14

18

2

1

260

19

16

May 18

50.00

4.31

4.00

0.13

15

1

1

190

16

20

Washed.

May 19

50.00

0.83

3.99

0.13

12

1

1

Sunday.

May 20

50.00

1.66

4.00

0.13

12

1

1

260

17

41

May 21

50.00

3.83

4.00

0.13

16

1

1

260

26

25

Washed.

May 22

50.00

0.82

3.99

0.13

20

1

1

280

16

19

May 23

50.00

1.64

4.00

0.13

15

1

1

130

20

22

May 24

50.00

3.85

4.00

0.13

15

1

1

170

17

32

Washed.

May 25

50.00

0.84

4.00

0.13

15

1

1

340

25

55

May 26

50.00

1.67

3.99

0.13

18

1

1

Sunday.

May 27

50.00

3.03

4.00

0.13

13

1

1

210

10

40

Washed.

May 28

50.00

0.87

4.01

0.13

16

1

1

260

26

55

May 29

50.00

1.43

4.01

0.13

16

1

1

500

19

50

May 30

50.00

2.55

4.00

0.13

14

1

1

Holiday.

May 31

50.00

4.19

4.00

0.13

17

1

1

380

22

50

June   1

50.00

6.26

3.99

0.13

15

1

1

900

27

50

Washed.

June   2

50.00

0.78

3.98

0.13

17

1

1

Sunday.

June   3

50.00

1.19

4.00

0.13

24

1

1

550

41

50

June   4

50.00

2.15

4.00

0.13

37

2

1

6,500

150

60

June   5

50.00

3.67

4.01

0.13

65

4

1

3,200

150

46

June   6

50.00

6.06

4.00

0.14

77

12

1

1,500

60

27

Washed.

June   7

50.00

0.86

4.00

0.14

64

19

1

2,100

68

45

June   8

50.00

1.41

4.00

0.14

46

16

1

600

35

44

June   9

50.00

2.62

4.01

0.14

44

12

1

Sunday.

June 10

50.00

4.79

4.00

0.14

36

8

1

240

31

35

Washed.

June 11

50.00

0.77

4.00

0.14

30

6

1

280

47

47

June 12

50.00

1.20

4.01

0.14

34

6

1

330

70

55

June 13

50.00

2.42

4.00

0.14

35

8

1

480

43

75

June 14

50.00

4.44

4.00

0.15

31

7

1

440

55

45

Washed.

June 15

50.00

0.80

3.99

0.15

32

6

1

420

17

34

June 16

50.00

1.15

4.00

0.15

26

5

1

Sunday.

June 17

50.00

2.15

3.99

0.14

26

5

1

340

55

37

June 18

50.00

4.36

4.00

0.14

31

6

1

440

14

140

Washed.

June 19

50.00

0.79

4.01

0.15

37

8

1

500

70

24

June 20

50.00

1.19

4.00

0.15

30

7

1

330

49

27

June 21

50.00

2.65

3.98

0.14

25

5

1

170

30

18

June 22

50.00

5.58

4.00

0.14

20

4

1

100

18

13

Washed.

June 23

50.00

0.85

3.62

0.13

26

3

1

Sunday.

June 24

50.00

2.02

3.99

0.13

140

11

1

1,700

27

36

June 25

50.00

4.77

3.99

0.13

130

26

1

400

70

23

Washed.

June 26

50.00

0.73

4.01

0.13

82

27

1

750

200

41

June 27

50.00

1.17

4.01

0.13

65

18

1

...

...

...

June 28

50.00

3.10

3.99

0.13

47

16

1

...

20

...

Washed.

June 29

50.00

0.67

3.99

0.13

37

7

1

220

35

29

June 30

50.00

1.02

4.00

0.13

30

6

1

Sunday.

July   1

50.00

2.70

3.99

0.13

30

6

1

400

46

3

Washed.

July   2

50.00

0.69

4.00

0.13

32

7

1

180

80

38

July   3

50.00

1.21

3.99

0.13

36

8

1

350

70

90

July   4

50.00

3.40

3.99

0.13

44

10

1

Holiday.

Washed.

July   5

50.00

0.77

3.99

0.13

44

11

1

550

180

34

July   6

50.00

1.19

4.01

0.13

39

10

1

250

60

26

July   7

50.00

3.72

3.99

0.13

34

8

1

Sunday.

Washed.

July   8

50.00

0.78

3.97

0.13

25

5

1

220

31

21

July   9

50.00

1.27

3.98

0.13

22

4

1

50

10

9

July 10

50.00

3.11

4.09

0.13

47

9

1

Lost.

Washed.

July 11

50.00

0.83

3.99

0.13

90

19

1

150

19

8

July 12

50.00

1.47

3.99

0.13

97

25

1

300

40

23

July 13

50.00

3.61

4.00

0.13

96

29

1

220

47

16

Washed.

July 14

50.00

0.84

3.99

0.13

90

30

1

Sunday.

July 15

50.00

1.30

4.00

0.13

95

30

1

375

55

21

July 16

50.00

2.72

3.99

0.14

120

35

1

Lost.

90

13

July 17

50.00

5.08

3.99

0.14

85

32

1

270

2

11

Washed.

July 18

50.00

0.85

3.99

0.14

56

22

1

1,675

70

50

July 19

50.00

1.43

4.00

0.14

41

12

1

450

95

22

July 20

50.00

3.23

3.99

0.14

62

19

1

300

38

11

Washed.

July 21

50.00

0.80

3.99

0.14

62

21

1

Sunday.

July 22

50.00

1.06

3.98

0.14

80

26

1

1,400

150

7

July 23

50.00

2.18

3.99

0.14

105

30

1

3,700

Lost.

11

July 24

50.00

4.95

3.98

0.15

95

30

1

770

Lost.

22

Washed.

July 25

50.00

0.84

3.98

0.15

77

22

1

250

33

11

July 26

50.00

1.22

3.98

0.15

67

19

1

140

100

4

July 27

50.00

2.36

4.00

0.16

54

15

1

300

95

7

July 28

50.00

4.74

3.98

0.16

46

12

1

Sunday.

Washed.

July 29

50.00

0.83

3.99

0.17

36

10

1

470

110

18

July 30

50.00

1.02

4.00

0.17

29

7

1

Plates lost.

July 31

50.00

1.66

4.00

0.17

21

5

1

Plates lost.

Aug.   1

48.20

2.95

4.00

0.17

16

4

1

Plateslost.

Aug.   2

46.40

4.96

4.00

0.17

15

2

1

130

42

13

Washed.

Aug.   3

42.60

0.79

4.00

0.17

16

1

1

120

4

16

Aug.   4

49.10

0.91

4.00

0.17

21

1

1

Sunday.

Aug.   5

49.10

1.59

4.00

0.17

29

1

1

230

160

11

Aug.   6

48.20

3.16

4.00

0.17

34

2

1

85

200

12

Aug.   7

45.60

5.65

3.99

0.17

21

2

1

200

Lost

4

Washed.

Aug.   8

50.00

0.80

3.99

0.17

19

2

1

100

70

11

Aug.   9

49.10

0.94

4.00

0.17

16

1

1

75

44

9

Aug. 10

48.20

1.51

4.00

0.17

24

1

1

60

13

6

Aug. 11

48.20

3.32

4.00

0.17

62

3

1

Sunday.

Washed.

Aug. 12

41.90

0.83

3.99

0.17

120

14

1

620

110

5

Aug. 13

49.10

1.14

3.99

0.17

107

29

1

820

53

36

Aug. 14

49.10

1.72

4.00

0.18

82

30

1

850

160

110

Aug. 15

48.20

3.30

4.00

0.18

65

22

1

150

37

4

Aug. 16

46.40

0.84

4.00

0.19

45

15

1

270

110

13

Aug. 17

48.20

1.05

4.00

0.19

35

10

1

340

110

6

Aug. 18

50.00

1.54

4.00

0.19

21

5

1

Sunday.

Aug. 19

49.10

2.29

4.00

0.19

18

4

1

180

85

13

Aug. 20

49.10

3.74

3.99

0.19

20

2

1

210

85

8

Washed.

Aug. 21

44.10

1.01

3.98

0.19

20

2

1

1300

115

9

Aug. 22

45.60

1.86

4.00

0.19

27

2

1

3800

265

1

Aug. 23

47.30

4.08

3.99

0.19

49

2

1

2500

70

13

Washed.

Aug. 24

41.30

1.29

3.97

0.19

36

6

1

3900

46

6

Aug. 25

44.10

2.11

3.98

0.20

34

7

1

Sunday.

Aug. 26

48.20

3.42

3.99

0.20

21

5

1

700

140

0

Aug. 27

48.20

5.10

4.00

0.20

19

4

1

470

100

4

Washed.

Aug. 28

46.40

1.28

4.00

0.20

18

3

1

500

49

3

Aug. 29

41.90

1.90

4.02

0.20

17

2

1

360

80

0

Aug. 30

45.60

3.23

4.00

0.20

15

1

1

320

190

1

Aug. 31

46.40

4.57

4.00

0.20

13

1

1

200

20

3

Sept.   1

50.00

5.17

3.65

0.20

14

1

1

Sunday.

Sept.   2

48.20

5.97

4.00

0.20

12

1

1

Holiday.

Washed.

Sept.   3

47.30

1.13

4.00

0.20

12

1

1

300

9

1

Sept.   4

48.20

2.01

4.00

0.20

16

1

1

600

60

2

Sept.   5

46.40

5.41

3.67

0.20

34

1

0

360

72

...

Washed.

Sept.   6

40.60

1.42

3.98

0.20

160

12

0

15000

140

0

Sept.   7

42.60

5.19

3.99

0.20

64

18

1

2000

130

1

Washed.

Sept.   8

42.60

1.25

4.00

0.20

56

18

1

Sunday.

Sept.   9

46.40

3.07

4.00

0.22

59

18

1

220

80

4

Washed.

Sept. 10

45.60

1.02

3.99

0.23

57

16

1

18000

57

8

Sept. 11

48.20

2.36

4.00

0.23

65

18

1

2700

90

1

Washed.

Sept. 12

44.10

1.14

3.99

0.24

72

18

1

1000

47

4

Sept. 13

46.40

3.61

3.99

0.25

87

20

1

2300

77

5

Washed.

Sept. 14

38.20

1.42

3.97

0.26

72

19

1

2400

80

5

Sept. 15

45.60

4.27

4.00

0.27

65

18

1

Sunday.

Washed.

Sept. 16

40.00

1.06

3.99

0.28

65

18

1

Lost.

22

Lost.

Sept. 17

46.40

2.48

4.01

0.28

52

16

1

420

75

1

Washed.

Sept. 18

46.40

1.11

4.00

0.28

60

13

1

900

37

3

Sept. 19

46.40

2.76

4.00

0.28

85

16

1

2000

186

0

Washed.

Sept. 20

44.10

1.12

4.00

0.31

100

19

1

4200

110

7

Sept. 21

48.20

2.07

3.99

0.33

120

24

1

1100

110

3

Washed.

Sept. 22

44.10

1.30

3.67

0.34

137

29

1

Sunday.

Sept. 23

45.60

3.79

3.99

0.39

112

25

1

2400

50

2

Washed.

Sept. 24

45.60

1.15

3.97

0.40

100

25

1

4000

69

4

Sept. 25

48.20

2.06

4.00

0.42

432

53

1

56000

680

0

Sept. 26

Stopped, unable to wash preliminary.

Sept. 28

50.00

1.74

4.00

0.71

127

35

1

...

...

37

Washed.

Sept. 29

44.10

2.85

3.99

0.82

105

31

1

Sunday.

Sept. 30

44.90

3.78

3.97

1.04

115

32

1

Lost.

Lost.

160

Washed.

Oct.   1

44.10

1.20

3.98

1.34

82

26

1

600

180

55

Oct.   2

49.10

3.22

3.97

1.54

65

19

1

4,400

120

5

Washed.

Oct.   3

44.10

1.31

3.97

1.56

59

17

1

900

55

10

Oct.   4

49.10

2.97

3.97

1.65

55

15

1

850

60

6

Washed.

Oct.   5

44.90

1.31

3.98

1.75

59

16

1

2,000

110

38

Oct.   6

46.40

3.65

3.99

1.89

59

17

1

Sunday.

Washed.

Oct.   7

44.90

1.34

3.98

1.99

52

13

1

1,250

70

15

Oct.   8

49.10

3.49

3.98

2.17

54

13

1

11,000

65

6

Washed.

Oct.   9

44.10

1.20

3.97

2.33

51

13

1

2,000

85

4

Oct. 10

49.10

2.22

3.98

2.55

50

12

1

800

36

10

Oct. 11

46.40

4.59

4.00

2.51

47

11

1

2,000

57

10

Oct. 12

Shut off to remove sand in preliminary filter in order to clean out the under-drains.

Nov.   5

50.00

1.38

3.97

3.49

185

50

1

...

...

...

Nov.   6

48.20

3.25

3.98

3.79

170

52

1

5,000

1,500

240

Washed.

Nov.   7

45.60

1.18

3.98

4.05

100

35

1

14,000

1,000

220

Nov.   8

48.20

4.08

3.99

4.37

95

32

1

1,900

270

160

Nov.   9

42.00

6.58

3.98

4.39

80

27

1

4,000

500

190

Nov. 10

Shut down for scraping. Removed 266,000 cu. cm. of sand.

Nov. 12

50.00

0.98

3.99

0.25

40

10

1

...

...

...

Nov. 13

50.00

1.51

4.00

0.22

36

8

1

1,600

750

85

Nov. 14

48.20

2.60

4.00

0.21

42

11

1

2,700

700

210

Nov. 15

47.30

3.80

4.00

0.20

35

9

1

1,800

350

180

Nov. 16

47.30

4.87

4.00

0.19

26

5

1

1,100

200

34

Nov. 17

50.00

5.75

4.00

0.19

20

4

1

Sunday.

Nov. 18

50.00

6.41

4.00

0.19

17

3

1

1,600

290

55

Washed.

Nov. 19

48.20

1.06

3.99

0.20

16

2

1

1,300

480

60

Nov. 20

48.20

2.05

3.99

0.20

45

3

1

6,500

3,700

800

Nov. 21

48.20

3.48

3.99

0.20

52

9

1

9,900

4,000

300

Nov. 22

47.30

4.85

3.99

0.20

65

17

1

10,000

1,000

380

Nov. 23

48.20

6.11

3.99

0.20

49

15

1

18,000

1,000

320

Washed.

Nov. 24

46.40

3.71

3.98

0.20

134

24

1

Sunday.

Nov. 25

Shut down for fear of washing preliminary with such muddy water.

Nov. 29

50.00

1.55

4.00

0.21

80

25

1

...

...

...

Nov. 30

47.30

3.14

3.98

0.22

54

16

1

3,800

950

160

Dec.   1

47.30

4.48

3.98

0.23

37

10

1

Sunday.

Dec.   2

47.30

5.63

3.98

0.25

36

6

1

2,900

550

90

Washed.

Dec.   3

46.40

0.98

3.99

0.25

29

6

1

2,900

480

75

Dec.   4

50.00

1.15

3.99

0.26

20

4

1

2,000

270

70

Dec.   5

50.00

1.48

4.00

0.25

18

3

1

1,100

270

50

Dec.   6

48.20

2.04

3.63

0.25

16

2

1

3,000

...

...

Dec.   7

48.20

2.80

4.00

0.26

14

1

1

2,400

190

10

Dec.   8

50.00

3.40

3.72

0.27

12

1

1

Sunday.

Dec.   9

49.10

3.93

4.00

0.27

11

1

1

1,200

170

7

Dec. 10

49.10

4.50

4.00

0.27

12

1

1

800

90

55

Dec. 11

48.20

5.52

4.00

0.27

255

44

1

6,500

---

---

Dec. 12

Shut down 12/11 at 6 P.M. turbidity too high to wash.

Dec. 15

---

---

---

---

---

---

---

Sunday.

Dec. 16

50.00

4.02

3.99

0.28

90

35

2

---

---

---

Washed.

Dec. 17

40.00

1.90

3.97

0.30

70

25

2

21,000

10,000

1,200

Washed.

Dec. 18

44.10

1.08

3.97

0.31

49

15

2

6,500

4,200

800

Dec. 19

48.20

1.88

3.98

0.31

39

10

1

Lost.

Lost.

Lost.

Dec. 20

46.40

4.77

3.99

0.31

42

13

1

Lost.

Lost.

Lost.

Dec. 21

46.40

6.68

3.99

0.32

26

6

1

Lost.

Lost.

Lost.

Washed.

Dec. 22

49.10

1.14

3.99

0.32

20

4

1

Sunday.

Dec. 23

49.10

2.17

4.00

0.31

34

7

1

1,400

300

100

Dec. 24

49.10

3.76

4.00

0.31

195

56

1

9,000

950

70

Dec. 25

Shut down 12/24 at 9 P.M. turbidity too high to wash. Holiday.

Dec. 30

50.00

2.61

3.97

0.33

56

19

2

---

---

---

Dec. 31

44.80

5.57

3.98

0.36

39

12

1

---

---

---

Washed.

1908.

Jan.   1

46.40

1.30

3.98

0.36

31

6

1

Holiday.

Jan.   2

48.20

3.36

4.00

0.36

39

9

1

---

---

---

Jan.   3

47.30

4.95

3.99

0.35

36

9

1

3,100

490

90

Jan.   4

50.00

5.28

3.99

0.35

32

7

1

2,400

240

43

Jan.   5

49.10

6.26

4.00

0.35

26

5

1

Sunday.

Washed.

Jan.   6

49.10

0.99

3.98

0.35

20

4

1

600

200

37

Jan.   7

50.00

1.15

4.00

0.35

20

4

1

1,100

150

47

Jan.   8

50.00

1.41

4.00

0.35

22

4

1

1,900

160

30

Jan.   9

49.10

1.92

4.00

0.35

45

11

1

13,000

1,300

70

Jan. 10

49.10

2.56

4.00

0.36

70

25

1

10,000

3,500

170

Jan. 11

50.00

3.17

3.99

0.37

56

18

1

16,000

4,000

240

Jan. 12

49.10

3.73

4.00

0.37

40

10

1

Sunday.

Jan. 13

50.00

4.14

4.00

0.37

110

45

2

8,500

1,200

840

Jan. 14

49.10

4.65

3.99

0.38

210

95

3

16,000

3,900

500

Jan. 15

49.10

5.23

3.99

0.41

325

190

12

24,000

7,000

550

Jan. 16

50.00

5.75

3.99

0.43

360

210

37

28,000

8,500

1,200

Jan. 17

49.10

6.34

4.00

0.45

242

122

24

65,000

15,000

1,700

Jan. 18

---

---

---

---

---

---

---

---

---

---

Jan. 19

50.00

1.17

4.00

0.46

117

40

12

Sunday.

Jan. 20

50.00

1.38

4.00

0.46

72

31

6

1,600

1,800

320

Jan. 21

50.00

1.68

3.57

0.37

55

20

4

5,000

450

Jan. 22

49.10

2.04

4.00

0.44

49

17

3

3,600

600

100

Jan. 23

50.00

2.47

3.24

0.33

40

12

3

1,800

290

130

Jan. 24

49.10

3.03

3.00

0.34

40

11

2

2,300

270

65

Jan. 25

50.00

3.61

3.00

0.35

39

10

2

1,100

180

60

Jan. 26

49.10

4.18

2.99

0.35

32

7

2

Sunday.

Jan. 27

50.00

4.81

3.00

0.35

32

7

2

300

40

24

Jan. 28

48.20

5.45

2.99

0.35

45

12

2

1,200

90

31

Jan. 29

49.10

6.01

2.99

0.35

60

21

2

1,000

230

50

Jan. 30

49.10

6.62

2.99

0.36

57

22

2

1,400

170

48

Washed.

Jan. 31

50.00

1.30

2.99

0.36

42

15

2

1,100

190

23

Feb.   1

50.00

1.51

2.99

0.37

39

11

2

750

40

31

Feb.   2

50.00

1.78

3.00

0.37

27

7

2

Sunday.

Feb.   3

49.10

2.13

3.00

0.37

29

6

2

1,300

200

7

Feb.   4

50.00

2.69

3.00

0.37

25

5

1

600

160

18

Feb.   5

49.10

3.31

2.99

0.37

24

5

1

750

140

41

Feb.   6

50.00

3.89

2.99

0.37

20

4

1

2,000

180

29

Feb.   7

48.20

4.50

2.99

0.37

17

3

1

...

38

15

Feb.   8

49.10

5.11

2.99

0.37

15

3

1

900

95

24

Feb.   9

49.10

5.65

3.00

0.38

14

3

1

Sunday.

Feb. 10

49.10

6.43

2.99

0.38

11

3

1

850

85

21

Feb. 11

50.00

6.90

3.00

0.38

10

3

1

1,000

70

20

Washed.

Feb. 12

49.10

1.29

2.99

0.38

8

2

1

750

20

16

Feb. 13

50.00

1.50

2.99

0.39

9

2

1

700

40

11

Feb. 14

50.00

1.80

2.99

0.39

9

2

1

1,200

39

7

Feb. 15

49.10

2.35

3.00

0.39

61

13

1

5,500

600

7

Feb. 16

49.10

3.28

2.99

0.39

80

30

2

Sunday.

Feb. 17

48.20

4.85

2.99

0.39

80

29

3

33,000

3,800

130

Feb. 18

47.30

6.39

2.99

0.39

130

44

3

---

2,600

160

Feb. 19

45.50

7.32

2.98

0.40

320

143

6

28,000

6,000

180

Washed.

Feb. 22

50.00

1.40

3.00

0.41

85

30

5

Holiday.

Feb. 23

50.00

1.77

3.00

0.41

60

21

4

Sunday.

Feb. 24

49.10

2.25

2.99

0.41

46

14

3

3,600

2,800

90

Feb. 25

50.00

2.61

3.00

0.41

31

7

2

2,300

140

47

Feb. 26

50.00

3.06

3.00

0.41

30

6

2

3,800

140

45

Feb. 27

48.20

3.65

2.99

0.41

30

5

1

1,300

100

22

Feb. 28

50.00

4.24

3.00

0.41

37

6

1

1,400

100

40

Feb. 29

48.20

5.28

2.99

0.41

123

52

2

13,500

420

40

Washed.

Mar.   1

44.60

1.56

2.99

0.42

97

39

5

Sunday.

Mar.   2

48.20

2.90

2.99

0.42

82

30

4

8,000

320

60

Mar.   3

46.40

4.69

2.98

0.42

87

33

4

11,000

750

30

Mar.   4

47.30

6.13

2.99

0.42

67

24

3

6,000

290

34

Mar.   5

48.20

7.31

2.99

0.42

59

19

3

4,400

220

41

Washed.

Mar.   6

49.10

1.53

2.99

0.42

72

24

2

7,000

170

41

Mar.   7

50.00

1.95

3.00

0.43

82

30

2

9,500

210

34

Mar.   8

49.10

2.62

2.99

0.43

92

37

3

Sunday.

Mar.   9

50.00

3.19

3.00

0.43

125

56

4

11,000

700

65

Mar. 10

Preliminary filter discontinued and the Puech system started.

TABLE 17—RECORD OF EXPERIMENTAL FILTER, PUECH SYSTEM.—(Continued.)

Date.

PUECH SYSTEM:

FINAL FILTER.

TURBIDITY.

BACTERIA.

Rates, millions of gallons per acre daily.

Rate, millions of gallons per acre daily.

Loss of head.

Applied water.

Effluent, preliminary filter.

Effluent, final filter.

Applied water.

Effluent, preliminary filter.

Effluent, final filter.

1908.

Mar. 11

265

170

90

53

18

2.99

0.53

155

80

7

6,500

8,500

490

Mar. 12

265

170

90

53

18

2.99

0.60

135

70

7

5,900

6,000

360

Mar. 13

265

170

90

53

18

3.00

0.60

122

52

6

1,900

1,700

140

Mar. 14

265

170

90

53

18

3.00

0.61

97

40

5

1,800

1,600

130

Mar. 15

265

170

90

53

18

2.99

0.64

77

31

4

Sunday.

Mar. 16

265

170

90

53

18

3.00

0.69

65

26

3

1,400

1,200

50

Mar. 17

241

155

82

48

16

2.99

0.71

59

19

3

900

200

45

Mar. 18

252

162

86

50

17

2.99

0.75

67

22

2

1,000

700

33

Mar. 19

241

155

82

48

16

2.99

0.78

60

21

2

...

800

44

Mar. 20

294

189

100

59

20

2.99

0.85

57

18

2

1,300

650

37

Mar. 21

279

179

95

56

19

2.99

0.92

67

21

2

800

600

34

Mar. 22

265

170

90

53

18

2.99

0.99

80

27

2

Sunday.

Mar. 23

265

170

90

53

18

2.99

1.06

90

32

2

4,600

1,300

33

Mar. 24

265

170

90

53

18

2.99

1.12

82

34

3

2,500

950

38

Mar. 25

265

170

90

53

18

2.99

1.18

67

27

3

1,600

...

30

Mar. 26

265

170

90

53

18

2.99

1.22

60

20

3

550

400

24

Mar. 27

265

170

90

53

18

3.00

1.23

59

18

2

950

360

28

Mar. 28

265

170

90

53

18

3.00

1.25

51

14

2

650

230

18

Mar. 29

265

170

90

53

18

2.99

1.28

31

6

2

Sunday.

Mar. 30

265

170

90

53

18

2.99

1.36

30

5

1

500

160

25

Mar. 31

265

170

90

53

18

2.99

1.43

39

7

1

750

140

26

April   1

265

170

90

53

18

3.00

1.48

44

9

1

750

60

41

April   2

265

170

90

53

18

2.99

1.56

42

9

1

1,100

140

26

April   3

318

204

108

64

22

2.99

1.63

41

8

1

1,500

47

11

April   4

294

189

100

59

20

2.99

1.70

54

13

1

700

80

35

April   5

279

179

95

56

19

3.00

1.73

50

13

1

Sunday.

April   6

279

179

95

56

19

2.99

1.76

41

9

1

440

65

17

April   7

265

170

90

53

18

3.00

1.78

35

6

1

650

65

34

April   8

265

170

90

53

18

3.00

1.79

39

6

1

550

44

10

April   9

265

170

90

53

18

3.00

1.79

40

6

1

390

30

25

April 10

265

170

90

53

18

3.00

1.77

40

6

1

500

27

16

April 11

265

170

90

53

18

3.00

1.78

45

7

1

430

28

28

April 12

265

170

90

53

18

2.99

1.80

52

11

1

Sunday.

April 13

265

170

90

53

18

...

1.81

50

10

1

490

17

26

April 14

Shut down on account of losing water when aqueduct was drained; also cleaned coarse sand filter. Started April 22d.

April 23

241

155

82

48

16

...

1.82

29

4

1

140

600

38

April 24

241

155

82

48

16

3.00

1.87

21

3

1

200

1,000

13

April 25

241

155

82

48

16

2.99

1.95

20

3

1

85

180

25

April 26

252

162

86

50

17

3.00

1.95

24

3

1

Sunday.

April 27

241

155

82

48

16

3.00

1.93

18

2

1

95

35

23

April 28

241

155

82

48

16

3.00

1.96

20

2

1

70

24

18

April 29

241

155

82

48

16

2.99

1.97

24

3

1

110

21

24

April 30

241

155

82

48

16

2.99

2.03

21

2

1

70

25

6

May   1

241

155

82

48

16

3.00

2.07

32

4

1

130

20

18

May   2

241

155

82

48

16

2.99

2.12

26

3

1

140

16

12

May   3

241

155

82

48

16

2.99

2.17

22

3

1

Sunday.

May   4

241

155

82

48

16

3.00

2.19

19

2

1

85

30

17

May   5

241

155

82

48

16

3.00

2.20

18

2

1

130

33

9

May   6

241

155

82

48

16

2.99

2.23

18

2

1

230

55

6

May   7

252

162

86

50

17

3.00

2.24

19

2

1

160

75

10

May   8

241

155

82

48

16

3.00

2.25

19

2

1

375

55

8

May   9

318

204

108

64

22

2.99

2.29

18

2

1

1,200

12

9

May 10

318

204

108

64

22

2.99

2.30

30

3

1

Sunday.

May 11

265

170

90

53

18

2.99

2.33

60

10

1

2,800

130

11

May 12

252

162

86

50

17

2.99

2.39

70

15

1

2,900

135

9

May 13

241

155

82

48

16

3.00

2.41

66

14

1

1,800

110

16

May 14

265

170

90

53

18

3.00

2.38

45

7

1

2,700

65

18

May 15

252

162

86

50

17

3.00

2.41

39

5

1

950

45

14

May 16

241

155

82

48

16

3.00

2.41

49

7

1

800

32

10

May 17

241

155

82

48

16

3.01

2.34

46

7

1

Sunday.

May 18

241

155

82

48

16

3.00

2.31

31

4

1

700

26

6

May 19

252

162

86

50

17

3.00

2.26

36

4

1

375

28

17

May 20

252

162

86

50

17

3.00

2.20

41

5

1

425

38

11

May 21

344

221

117

69

23

3.00

2.18

30

3

1

300

25

9

May 22

241

155

82

48

16

3.01

2.17

53

7

1

950

220

18

May 23

265

170

90

53

18

2.99

2.25

127

38

1

2,400

600

21

May 24

331

212

112

66

22

3.00

2.19

110

39

3

Sunday.

May 25

318

204

108

64

22

3.01

2.02

90

25

3

600

300

40

May 26

279

179

95

56

19

3.02

1.87

135

45

3

3,200

110

34

May 27

265

170

90

53

18

3.01

1.63

110

39

3

14,500

320

45

May 28

252

162

86

50

17

3.01

1.41

90

27

3

1,000

95

28

May 29

252

162

86

50

17

3.01

1.24

70

17

3

1,100

150

26

May 30

252

162

86

50

17

3.01

1.07

50

9

2

Holiday.

May 31

241

155

82

48

16

3.01

1.03

34

4

2

Sunday.

June   1

252

162

86

50

17

3.00

0.83

35

4

1

...

...

...

June   2

241

155

82

48

16

3.00

0.74

39

5

1

...

...

...

June   3

252

162

86

50

17

3.00

0.68

35

4

1

...

...

...

June   4

241

155

82

48

16

3.00

0.63

30

3

1

...

...

...

June   5

252

162

86

50

17

2.99

0.60

30

3

1

...

...

...

June   6

241

155

82

48

16

3.00

0.56

27

3

1

...

...

...

June   7

241

155

82

48

16

2.99

0.53

22

2

1

...

...

...

June   8

241

155

82

48

16

3.00

0.49

20

1

1

...

...

...

June   9

241

155

82

48

16

2.99

0.46

20

1

1

...

...

...

June 10

241

155

82

48

16

3.00

0.44

17

1

1

...

...

...

June 11

331

212

112

66

22

2.98

0.42

12

1

1

...

...

...

June 12

318

204

108

64

22

2.98

0.42

11

1

1

...

...

...

June 13

265

170

90

53

18

3.00

0.40

36

3

1

...

...

...

June 14

252

162

86

50

17

2.99

0.40

39

5

1

...

...

...

June 15

241

155

82

48

16

2.99

0.39

25

3

1

...

...

...

June 16

241

155

82

48

16

2.99

0.40

34

3

1

...

...

...

June 17

252

162

86

50

17

2.99

0.41

64

11

1

...

...

...

June 18

241

155

82

48

16

2.99

0.42

57

11

1

...

...

...

June 19

241

155

82

48

16

2.99

0.42

46

8

1

...

...

...

June 20

241

155

82

48

16

2.99

0.42

40

5

1

...

...

...

June 21

241

155

82

48

16

3.00

0.43

28

4

1

...

...

...

June 22

241

155

82

48

16

2.99

0.43

25

3

1

...

...

...

June 23

241

155

82

48

16

2.99

0.43

25

3

1

...

...

...

June 24

241

155

82

48

16

2.99

0.43

29

4

1

...

...

...

June 25

241

155

82

48

16

2.99

0.43

18

2

1

...

...

...

June 26

241

155

82

48

16

2.80

0.42

15

1

1

...

...

...

June 27

241

155

82

48

16

2.99

0.44

12

1

1

...

...

...

June 28

241

155

82

48

16

2.99

0.44

9

1

1

...

...

...

June 29

241

155

82

48

16

2.99

0.44

8

1

1

...

...

...

June 30

241

155

82

48

16

2.99

0.44

10

1

1

...

...

...

July   1

241

155

82

48

16

3.00

0.45

8

1

1

80

10

4

July   2

241

155

82

48

16

3.00

0.46

8

1

0

290

24

5

July   3

241

155

82

48

16

3.00

0.47

8

1

0

350

45

6

July   4

241

155

82

48

16

2.99

0.49

9

1

0

...

...

...

July   5

305

195

103

61

21

3.00

0.51

10

1

0

...

...

...

July   6

241

155

82

48

16

3.00

0.51

9

1

0

300

36

7

July   7

241

155

82

48

16

2.99

0.53

8

1

0

110

10

3

July   8

252

162

86

50

17

3.00

0.53

9

1

0

85

22

2

July   9

241

155

82

48

16

3.00

0.54

8

1

0

85

26

2

July 10

...

...

...

...

...

...

...

...

...

...

200

3

5

July 11

305

195

103

61

21

3.00

0.56

12

1

0

145

7

3

July 12

241

155

82

48

16

2.99

0.58

11

1

0

...

...

...

July 13

241

155

82

48

16

3.00

0.60

10

1

0

115

34

55

July 14

241

155

82

48

16

2.99

0.62

16

1

0

300

55

30

July 15

241

155

82

48

16

2.99

0.64

17

1

0

180

32

23

July 16

241

155

82

48

16

3.00

0.67

13

1

0

100

115

3

July 17

241

155

82

48

16

2.99

0.71

10

1

0

65

275

5

July 18

241

155

82

48

16

2.99

0.73

11

1

0

38

425

10

July 19

241

155

82

48

16

3.00

0.76

12

1

0

...

...

...

July 20

241

155

82

48

16

2.99

0.79

10

1

0

95

90

70

July 21

252

162

86

50

17

2.99

0.83

10

1

1

70

17

4

July 22

241

155

82

48

16

2.99

0.87

13

1

1

440

8

5

July 23

305

195

103

61

21

2.99

0.92

54

4

1

650

26

5

July 24

331

212

111

66

22

2.98

0.99

305

61

1

1,650

...

...

July 25

265

170

90

53

18

2.98

1.08

330

85

1

2,600

115

15

July 26

252

162

86

50

17

2.98

1.21

290

77

2

...

...

...

July 27

305

195

103

61

21

2.98

1.40

335

87

2

35,000

250

...

July 28

252

162

86

50

17

2.98

1.68

170

52

2

1,200

1,350

15

July 29

252

162

86

50

17

2.97

2.14

180

52

2

2,000

600

13

July 30

252

162

86

50

17

2.97

2.65

237

56

2

800

1,300

12

July 31

241

155

82

48

16

2.95

3.01

250

60

2

1,000

310

7

TABLE 18—RECORD OF EXPERIMENTAL FILTER PLANT NO. 2.

Date.

PRELIMINARY FILTER.

FINAL FILTER.

TURBIDITY

BACTERIA

Rate, millions of gallons per acre daily.

Loss of head.

Rate, millions of gallons per acre daily.

Loss of head.

Applied water.

Effluent preliminary filter.

Effluent final filter.

Applied water.

Effluent preliminary filter.

Effluent final filter.

1907.

Feb.   8

21.50

0.04

2.81

0.17

...

...

...

1,100

2,100

...

Feb.   9

21.60

0.04

1.09

0.06

...

...

...

200

550

2,100

Feb. 10

20.90

0.05

1.59

0.08

...

...

...

...

...

...

Feb. 11

19.80

0.05

3.01

0.15

12

6

2

600

1,160

1,100

Feb. 12

19.70

0.06

3.01

0.14

12

5

2

650

400

700

Feb. 13

19.60

0.06

3.01

0.12

15

5

2

660

900

700

Feb. 14

24.70

0.07

2.65

0.13

15

6

2

650

1,100

900

Feb. 15

37.20

...

3.40

0.12

12

5

2

600

800

850

Feb. 16

37.30

...

3.40

0.11

14

4

2

850

950

600

Feb. 17

Shut down for changes in meters and piping.

Feb. 18

...

...

...

...

...

...

...

1,200

...

600

Feb. 21

44.50

...

4.36

0.19

20

6

2

1,800

1,400

800

Feb. 22

48.60

...

4.37

0.16

15

4

2

Holiday.

Feb. 23

48.40

...

4.20

0.15

20

7

2

1,600

750

380

Feb. 24

48.30

...

4.02

0.13

20

10

3

Sunday.

Feb. 25

Shut down several hours.

0.14

20

10

3

1,400

1,000

450

Feb. 26

48.60

0.04

4.12

0.14

20

10

3

700

800

260

Feb. 27

53.20

0.04

4.08

0.15

17

8

3

700

700

290

Feb. 28

52.80

0.04

4.09

0.15

15

8

3

800

650

500

Mar.   1

53.00

0.04

4.10

0.16

15

8

3

650

550

200

Mar.   2

53.30

0.04

4.11

0.16

15

7

3

1,000

800

300

Mar.   3

50.60

0.05

4.11

0.16

31

11

3

Sunday.

Mar.   4

42.40

0.05

4.12

0.17

35

15

6

1,200

1,500

360

Mar.   5

42.70

0.05

4.11

0.17

135

52

10

13,000

850

...

Mar.   6

48.60

0.07

4.13

0.17

135

54

12

18,000

8,000

...

Mar.   7

50.50

0.08

4.12

0.18

102

46

8

24,000

6,500

1,800

Mar.   8

51.80

0.09

4.12

0.18

100

40

6

22,000

6,000

1,600

Mar.   9

53.00

0.10

4.12

0.18

90

40

5

24,000

6,000

800

Mar. 10

54.40

0.12

4.11

0.19

82

39

6

Sunday.

Mar. 11

51.00

0.12

4.12

0.19

68

32

7

18,000

4,300

240

Mar. 12

51.20

0.12

4.07

0.19

46

25

5

11,000

4,600

210

Mar. 13

50.50

0.12

4.00

0.19

40

20

5

9,000

1,500

200

Mar. 14

46.50

0.12

...

0.20

39

20

4

5,500

1,200

90

Mar. 15

45.80

0.12

3.98

0.20

35

18

4

6,500

1,100

150

Mar. 16

42.50

0.12

3.97

0.19

60

24

4

5,000

800

160

Mar. 17

49.30

0.14

3.98

0.19

135

45

5

Sunday.

Mar. 18

52.60

0.16

3.98

0.20

170

59

9

9,000

1,700

100

Mar. 19

53.50

0.17

4.01

0.19

125

51

8

7,000

1,000

120

Mar. 20

52.90

0.17

3.99

0.18

102

40

6

4,800

700

75

Mar. 21

48.20

0.16

4.00

0.19

125

42

5

8,500

1,100

90

Mar. 22

51.80

0.18

4.01

0.20

190

82

5

7,500

1,100

55

Mar. 23

51.60

0.19

4.01

0.20

180

75

6

7,500

1,300

90

Mar. 24

48.20

0.17

4.01

0.20

140

68

7

Sunday.

Mar. 25

48.50

0.18

4.01

0.20

88

40

5

4,400

900

75

Mar. 26

45.90

0.18

3.98

0.20

62

32

4

3,600

750

90

Mar. 27

50.50

0.20

4.04

0.20

47

25

4

2,200

400

60

Mar. 28

49.60

0.20

3.92

0.19

35

16

3

1,300

350

55

Mar. 29

42.20

0.17

3.98

0.19

26

12

3

700

180

20

Mar. 30

48.00

0.22

4.01

0.19

25

7

3

310

220

39

Mar. 31

49.10

0.22

3.99

0.20

21

6

2

Sunday.

April   1

49.10

0.24

4.00

0.20

20

6

2

600

110

38

April   2

49.70

0.25

4.00

0.20

24

6

2

270

110

29

April   3

51.40

0.27

4.00

0.21

24

6

2

460

85

31

April   4

48.70

0.27

4.00

0.22

20

6

2

280

60

22

April   5

48.10

0.27

4.00

0.22

20

5

2

450

70

40

April   6

Shut down awaiting Mr. Maiguen to apply bone-charcoal.

April   7

Removed 1.06 in. of sand.

Sunday.

April   8

52.20

0.33

4.05

0.27

18

4

3

330

...

...

April   9

46.90

0.29

4.02

0.29

18

4

2

140

60

32

April 10

47.60

0.31

4.03

0.28

30

4

1

750

120

28

April 11

46.00

0.30

4.04

0.28

66

7

2

4,000

...

32

April 12

45.40

0.31

4.03

0.29

72

20

3

14,000

2,900

85

April 13

45.10

0.32

3.99

0.32

80

30

3

13,000

2,500

95

April 14

49.00

0.34

4.00

0.32

77

35

4

Sunday.

April 15

47.80

0.35

3.99

0.33

62

31

4

7,000

1,100

60

April 16

47.40

0.36

3.99

0.34

47

27

4

3,600

650

31

April 17

45.60

0.36

4.00

0.34

39

21

3

1,600

160

38

April 18

45.70

0.36

4.00

0.34

30

13

2

1,810

210

42

April 19

45.60

0.37

4.00

0.34

25

9

2

790

190

34

April 20

45.30

0.40

4.00

0.36

20

6

2

540

87

23

April 21

47.20

0.44

3.99

0.38

20

4

2

Sunday.

April 22

45.20

0.42

3.99

0.38

18

3

1

235

55

22

April 23

44.90

0.44

4.05

0.40

15

3

1

170

45

16

April 24

40.50

0.41

4.02

0.44

19

2

1

150

14

14

April 25

39.60

0.41

4.03

0.45

34

3

1

700

12

23

April 26

40.70

0.44

4.05

0.45

46

4

1

1,200

80

16

April 27

39.30

0.44

4.00

0.44

52

4

1

1,700

160

23

April 28

34.70

0.43

4.05

0.44

45

5

1

Sunday.

April 29

37.20

0.45

4.00

0.42

44

6

1

600

60

10

April 30

43.00

0.49

4.00

0.41

39

7

1

550

55

15

May   1

41.30

0.49

4.00

0.41

31

6

1

500

80

17

May   2

42.40

0.49

4.00

0.41

24

5

1

500

80

19

May   3

40.70

0.48

4.00

0.40

19

4

1

280

75

48

May   4

33.80

0.47

4.00

0.39

16

3

1

400

80

9

May   5

26.20

0.43

4.00

0.39

15

1

1

Sunday.

May   6

29.00

0.38

3.99

0.37

13

2

1

390

100

65

May   7

27.60

0.36

...

0.37

12

2

1

190

60

19

May   8

24.70

0.31

3.99

0.37

10

2

1

...

...

...

Washed.

May   9

24.40

0.03

3.98

0.39

10

2

1

390

65

10

May 10

24.80

0.04

4.00

0.42

10

2

1

300

80

18

May 11

50.00

0.06

4.00

0.44

12

2

1

390

110

12

May 12

50.00

0.08

4.00

0.48

17

2

1

Sunday.

May 13

50.00

0.09

4.00

0.47

35

3

1

600

100

18

May 14

50.00

0.10

4.00

0.46

39

4

1

500

65

15

May 15

48.50

0.15

4.00

0.45

17

3

1

500

70

16

May 16

47.00

0.16

4.00

0.46

24

3

1

290

70

16

May 17

47.00

0.16

3.99

0.47

18

3

1

260

40

9

May 18

47.00

0.19

4.00

0.48

15

2

1

190

...

17

May 19

47.00

0.21

3.99

0.51

12

2

1

Sunday.

May 20

46.60

0.24

4.00

0.53

12

2

1

260

40

13

May 21

46.40

0.24

4.00

0.55

16

2

1

260

65

9

May 22

46.40

0.27

4.00

0.58

20

2

1

280

35

12

May 23

46.40

0.29

4.00

0.61

15

2

1

130

35

10

May 24

46.40

0.30

4.00

0.63

15

2

1

170

26

6

May 25

46.40

0.32

4.00

0.66

15

2

1

340

80

13

May 26

46.40

0.34

3.99

0.70

18

2

1

Sunday.

May 27

46.40

0.86

3.99

0.74

13

2

1

210

80

7

May 28

46.40

0.38

3.15

0.76

16

2

1

260

70

10

May 29

46.00

0.44

3.88

0.78

16

2

1

500

55

12

May 30

45.60

0.46

3.99

0.86

14

2

1

Holiday.

May 31

45.60

0.46

4.00

0.92

17

2

1

380

65

11

June   1

45.60

0.46

4.00

0.98

15

2

1

900

48

10

June   2

45.60

0.48

4.00

1.09

17

2

1

Sunday.

June   3

45.60

0.51

4.00

1.20

24

2

1

550

75

16

June   4

45.60

0.54

4.00

1.32

37

3

1

6,500

...

22

June   5

45.60

0.55

4.00

1.48

65

5

1

3,200

140

19

June   6

45.60

0.56

4.01

3.66

77

16

1

1,500

210

14

June   7

45.00

0.57

4.00

1.80

64

27

1

2,100

230

20

June   8

45.00

0.57

4.00

1.90

46

22

1

600

240

33

June   9

45.00

0.55

4.01

2.00

44

18

1

Sunday.

June 10

45.00

0.56

4.00

2.09

36

12

1

240

110

43

June 11

45.00

0.58

4.00

2.17

30

8

1

280

130

60

June 12

45.00

0.60

4.01

2.27

34

8

1

330

150

60

June 13

45.00

0.62

4.00

2.36

35

10

1

480

...

120

June 14

45.00

0.63

3.99

2.49

31

9

1

440

...

65

June 15

45.00

0.64

3.99

2.56

32

8

1

420

...

49

June 16

44.70

0.65

4.00

2.63

26

7

1

Sunday.

June 17

44.40

0.64

4.00

2.67

26

6

1

340

270

55

June 18

45.00

0.63

3.98

2.69

31

7

1

440

140

65

June 19

45.00

0.63

4.00

2.73

37

10

1

500

110

24

June 20

45.00

0.62

4.01

2.72

30

9

1

330

70

34

June 21

45.00

0.61

4.01

2.68

25

7

1

170

130

60

June 22

Shut down to scrape and apply asbestos and coke; removed 0.79 in. of sand.

June 23

Applied 8 lb. of asbestos and 10 lb. of bone-charcoal.

June 25

50.00

0.54

4.00

0.27

130

45

1

400

...

...

June 26

50.00

0.57

4.01

0.46

82

37

1

750

550

35

June 27

50.00

0.63

4.01

0.55

65

26

1

...

1,200

140

June 28

50.00

0.65

3.99

0.63

47

21

1

...

1,200

26

June 29

50.00

0.70

4.00

0.73

37

9

1

220

800

22

June 30

50.00

0.77

3.99

0.82

30

8

1

Sunday.

July   1

50.00

0.87

4.00

0.80

30

8

1

400

90

37

July   2

50.00

0.95

4.01

0.73

32

9

1

180

230

25

July   3

50.00

1.01

4.00

0.66

36

10

1

350

80

58

July   4

50.00

1.03

4.00

0.58

44

12

1

Holiday.

July   5

50.00

1.07

3.99

0.54

24

14

1

550

130

47

July   6

50.00

1.10

4.00

0.52

39

12

1

250

110

33

July   7

50.00

1.14

4.00

0.50

34

10

1

Sunday.

July   8

50.00

1.16

4.00

0.48

25

7

1

220

190

14

July   9

50.00

1.18

4.00

0.46

22

5

1

50

30

3

July 10

50.00

1.20

3.99

0.45

47

11

1

Lost.

Lost.

Lost.

July 11

50.00

1.20

3.99

0.45

90

30

1

150

140

12

July 12

50.00

1.20

4.01

0.44

97

35

1

300

110

20

July 13

50.00

1.15

4.00

0.47

90

39

1

220

120

14

July 14

50.00

1.15

4.00

0.48

90

40

1

Sunday.

July 15

50.00

1.14

3.99

0.48

95

40

1

375

320

19

July 16

50.00

1.19

4.00

0.48

120

45

1

Lost.

150

12

July 17

50.00

1.21

4.00

0.48

85

42

1

270

60

5

July 18

50.00

1.19

3.99

0.50

56

32

1

1,675

23

39

July 19

50.00

1.16

3.99

0.52

41

20

1

450

200

13

July 20

50.00

1.16

3.99

0.56

62

29

1

300

220

8

July 21

50.00

1.19

3.99

0.63

62

31

1

Sunday.

July 22

50.00

1.20

3.99

0.77

80

36

1

1,400

70

9

July 23

50.00

1.21

3.99

0.93

105

40

1

3,700

370

25

July 24

50.00

1.38

3.99

1.07

95

40

1

770

260

31

July 25

50.00

1.17

3.99

1.22

77

32

1

250

230

3

July 26

50.00

1.07

4.00

1.37

67

29

1

140

90

12

July 27

50.00

1.11

4.00

54

25

1

300

180

6

July 28

50.00

1.22

3.98

1.65

46

19

1

Sunday.

July 29

50.00

1.21

4.00

1.82

36

16

1

470

230

18

July 30

50.00

1.20

3.99

1.98

29

11

1

Plates lost.

July 31

50.00

1.20

3.99

2.11

21

9

1

Plates lost.

Aug.   1

51.00

1.21

3.99

2.27

16

6

1

Plates lost.

Aug.   2

51.00

1.21

3.99

2.43

15

4

1

130

130

4

Aug.   3

51.00

1.21

4.00

2.66

16

3

1

120

80

4

Aug.   4

50.00

1.21

3.99

2.95

21

3

1

Sunday.

Aug.   5

50.00

1.21

3.98

3.22

29

3

1

230

210

4

Aug.   6

50.00

1.22

3.98

3.50

34

4

1

85

320

19

Aug.   7

50.00

1.21

3.99

3.74

21

4

1

200

Lost.

19

Aug.   8

48.20

1.20

...

4.09

19

4

1

100

150

17

Aug.   9

50.00

1.18

...

4.45

16

3

1

75

220

9

Aug. 10

47.30

1.16

...

4.67

24

3

1

60

250

10

Aug. 11

Shut down to drain and scrape sand filter; O.9 in. depth over all.

Aug. 16

Out of service all the rest of month washing sponge and asbestos.

Sept.   3

50.00

0.02

4.00

0.16

12

5

1

300

...

...

Sept.   4

50.00

0.02

3.99

0.14

16

6

1

600

260

370

Sept.   5

50.00

0.02

4.01

0.13

34

6

1

360

71

165

Sept.   6

46.40

0.02

4.00

0.12

160

52

1

15,000

1,900

120

Sept.   7

50.00

0.03

4.00

0.11

64

26

1

2,000

170

62

Sept.   8

46.40

0.04

3.99

0.11

56

25

1

Sunday.

Sept.   9

50.00

0.05

4.90

0.11

59

25

1

220

13

19

Sept. 10

50.00

0.05

4.00

0.11

57

21

1

18,000

100

24

Sept. 11

50.00

0.06

4.00

0.11

65

25

1

2,700

150

25

Sept. 12

50.00

0.07

4.00

0.12

72

26

1

1,000

190

36

Sept. 13

50.00

0.08

4.00

0.12

87

30

1

2,300

...

35

Sept. 14

50.00

0.09

4.01

0.12

72

27

1

2,400

130

230

Sept. 15

48.20

0.11

4.00

0.12

65

25

1

Sunday.

Sept. 16

51.00

0.13

4.00

0.12

65

25

1

Lost.

Lost.

27

Sept. 17

50.00

0.14

4.00

0.12

52

21

1

420

60

29

Sept. 18

49.10

0.14

4.00

0.13

60

18

1

900

80

41

Sept. 19

50.00

0.15

4.00

0.13

85

22

1

2,000

...

19

Sept. 20

49.10

0.17

4.00

0.13

100

29

1

4,200

300

28

Sept. 21

49.10

0.18

4.00

0.13

120

34

1

1,100

160

30

Sept. 22

48.20

0.20

4.00

0.13

137

41

1

Sunday.

Sept. 23

49.10

0.19

4.00

0.13

112

37

1

2,400

90

34

Sept. 24

46.40

0.19

3.99

0.14

100

35

1

4,000

210

12

Sept. 25

46.40

0.20

4.00

0.14

432

80

1

56,000

510

27

Sept. 26

45.60

0.24

4.00

0.15

385

80

4

1,300

450

55

Sept. 27

44.80

0.27

4.00

0.16

245

70

3

4,000

240

41

Sept. 28

46.40

0.30

3.99

0.16

127

46

2

15,000

430

37

Sept. 29

46.40

0.31

3.99

0.16

105

41

2

Sunday.

Sept. 30

46.40

0.31

4.00

0.17

115

42

1

Lost.

1,600

110

Oct.   1

48.20

0.33

4.00

0.18

82

36

1

600

600

120

Oct.   2

50.00

0.33

4.01

0.19

65

27

1

4,400

170

47

Oct.   3

48.20

0.33

4.00

0.19

59

34

1

900

210

44

Oct.   4

48.20

0.34

4.00

0.19

55

20

1

850

200

37

Oct.   5

50.00

0.38

4.00

0.19

9

21

1

2,000

150

34

Oct.   6

48.20

0.41

4.00

0.19

59

24

1

Sunday.

Oct.   7

48.20

0.42

4.00

0.19

552

17

1

1,250

200

28

Oct.   8

50.00

0.42

4.00

0.19

54

16

1

11,000

210

28

Oct.   9

44.80

0.40

4.00

0.19

51

16

1

2,000

310

29

Oct. 10

48.20

0.42

4.00

0.19

50

15

1

800

220

16

Oct. 11

48.20

0.43

4.00

0.20

47

13

1

2,000

310

46

Washed.

Oct. 12

50.00

0.14

4.00

0.20

36

11

1

1,200

370

25

Oct. 13

47.30

0.15

4.00

0.21

40

15

1

Sunday.

Oct. 14

50.00

0.18

4.00

0.22

47

19

1

1,200

390

22

Oct. 15

53.00

0.20

4.00

0.23

41

16

1

900

140

16

Oct. 16

50.00

0.20

4.00

0.24

35

12

1

Lost.

310

18

Oct. 17

50.00

0.21

4.00

0.25

30

8

1

550

180

7

Oct. 18

50.00

0.21

4.00

0.25

25

6

1

260

100

33

Oct. 19

50.00

0.21

4.00

0.25

25

6

1

750

220

15

Oct. 20

50.00

0.22

4.00

0.25

20

5

1

Sunday.

Oct. 21

50.00

0.23

4.00

0.25

19

5

1

480

120

11

Oct. 22

50.00

0.24

4.00

0.26

18

4

1

230

70

7

Oct. 23

50.00

0.25

4.00

0.26

15

3

1

250

120

12

Oct. 24

50.00

0.26

4.00

0.26

15

3

1

300

80

12

Oct. 25

50.00

0.27

4.00

0.27

15

2

1

450

60

15

Oct. 26

50.00

0.28

4.00

0.27

15

2

1

450

Lost.

14

Oct. 27

50.00

0.29

4.00

0.27

13

2

0

Sunday.

Oct. 28

50.00

0.30

4.00

0.27

13

2

0

190

110

9

Oct. 29

50.00

0.31

4.00

0.27

25

2

0

380

...

...

Oct. 30

50.00

0.32

4.00

0.27

21

3

0

...

...

...

Oct. 31

Out of commission. 4-in supply pipe stopped up.

Nov.   4

50.00

0.16

4.00

0.28

125

11

1

...

...

...

Nov.   5

50.00

0.17

4.00

0.28

185

61

1

6,000

3,000

220

Nov.   6

50.00

0.18

4.00

0.29

170

66

1

5,000

1,100

150

Nov.   7

50.00

0.20

4.00

0.30

100

45

1

14,000

1,600

120

Nov.   8

50.00

0.21

4.00

0.32

95

42

1

1,900

2,000

29

Nov.   9

50.00

0.22

4.00

0.34

80

36

1

4,000

2,000

110

Nov. 10

50.00

0.23

4.00

0.36

67

29

1

Sunday.

Nov. 11

50.00

0.24

3.46

0.38

52

20

1

1,900

460

160

Nov. 12

50.00

0.26

3.99

0.40

40

13

1

7,500

1,100

110

Nov. 13

50.00

0.27

4.00

0.44

36

10

1

1,600

550

50

Nov. 14

50.00

0.28

4.00

0.49

42

13

1

2,700

950

48

Nov. 15

50.00

0.29

4.00

0.55

35

11

1

1,800

900

49

Nov. 16

50.00

0.30

4.00

0.65

26

7

1

1,100

360

35

Nov. 17

50.00

0.31

3.98

0.80

20

5

1

Sunday.

Nov. 18

50.00

0.32

3.99

0.98

17

4

1

1,600

200

35

Nov. 19

50.00

0.34

3.99

1.26

16

3

1

1,300

400

55

Nov. 20

50.00

0.35

3.98

1.64

45

4

1

6,500

3,500

200

Nov. 21

50.00

0.36

3.99

2.03

52

12

1

9,900

4,500

130

Nov. 22

50.00

0.37

3.98

2.33

65

24

1

10,000

5,500

220

Nov. 23

50.00

0.38

3.99

2.60

49

19

1

18,000

3,500

100

Nov. 24

50.00

0.40

3.98

2.85

134

32

1

Sunday.

Nov. 25

48.20

0.45

3.98

3.10

225

87

2

50,000

19,000

340

Nov. 26

50.00

0.49

3.98

3.62

237

90

2

40,000

11,000

220

Nov. 27

50.00

0.51

3.99

4.15

185

77

2

16,000

7,500

310

Nov. 28

50.00

0.54

3.84

4.44

130

57

2

Holiday.

Nov. 29

50.00

0.55

3.67

4.55

80

36

1

10,000

2,200

80

Nov. 30

50.00

0.56

3.44

4.65

54

25

1

3,800

2,200

55

Dec.   2

Shut down to scrape sand filter.

Dec.   6

50.00

0.64

4.00

0.46

16

3

1

---

---

---

Dec.   7

50.00

0.64

4.00

0.39

14

3

1

2,400

1,200

490

Dec.   8

50.00

0.64

4.01

0.35

12

2

1

Sunday.

Dec.   9

50.00

0.65

4.01

0.33

11

2

1

1,200

420

60

Dec.   10

50.00

0.65

4.00

0.33

12

2

1

800

950

66

Dec.   11

47.30

0.64

4.00

0.35

255

84

3

6,500

1,600

140

Dec.   12

46.40

0.70

3.98

0.39

212

100

6

48,000

15,000

1,800

Dec.   13

50.00

0.79

3.98

0.49

495

217

9

42,000

20,000

1,600

Dec.   14

52.00

0.84

3.97

0.65

357

167

9

49,000

9,500

1,200

Dec.   15

49.10

0.84

3.98

0.77

157

76

6

Sunday.

Dec.   16

49.10

0.86

3.97

0.84

90

42

4

19,000

800

700

Dec.   17

49.10

0.88

3.98

0.91

70

31

2

21,000

18,000

1,600

Dec.   18

48.20

0.89

3.98

0.94

49

21

2

6,500

7,000

600

Dec.   19

50.00

0.91

3.98

0.97

39

13

1

Lost.

Lost.

Lost.

Dec.   20

49.10

0.92

3.98

1.03

42

16

1

"

"

"

Dec.   21

50.00

0.94

3.98

1.08

26

7

1

"

"

"

Dec.   22

50.00

0.97

3.98

1.13

20

5

1

Sunday.

Dec.   23

50.00

0.95

3.98

1.19

34

9

1

1,400

500

160

Dec.   24

47.30

0.93

3.98

1.28

195

75

2

9,000

1,700

130

Dec.   25

44.10

0.91

3.97

1.47

445

210

9

Holiday.

Dec.   26

46.40

1.01

3.97

1.63

370

172

7

51,000

8,000

250

Dec.   27

50.00

1.11

3.98

1.81

245

110

5

55,000

5,600

210

Dec.   28

48.20

1.12

3.99

1.87

102

46

3

10,000

4,500

140

Dec.   29

50.00

1.14

3.99

1.85

75

32

2

Sunday.

Dec.   30

49.10

1.15

3.98

1.86

56

24

2

4,400

1,900

190

Dec.   31

50.00

1.17

4.00

1.87

39

15

1

14,000

1,300

60

1908.

Jan.   1

50.00

1.18

3.98

1.90

31

8

1

...

...

...

Jan.   2

50.00

1.18

3.99

1.94

39

11

1

4,400

750

45

Jan.   3

50.00

1.19

3.98

1.98

36

11

1

3,100

1,600

70

Washed.

Jan.   4

50.00

0.17

3.97

2.09

32

9

1

2,400

1,200

43

Jan.   5

50.00

0.18

3.98

2.22

26

6

1

Sunday.

Jan.   6

50.00

0.19

3.98

2.28

20

5

1

600

600

49

Jan.   7

50.00

0.20

3.98

2.37

20

5

1

1,100

330

49

Jan.   8

50.00

0.21

3.99

2.43

22

5

1

1,900

900

43

Jan.   9

50.00

0.23

3.98

2.52

45

13

1

13,000

3,400

50

Jan. 10

50.00

0.24

3.99

2.66

70

30

1

10,000

8,000

50

Jan. 11

50.00

0.27

3.98

2.74

56

22

1

16,000

220

200

Jan. 12

50.00

0.28

3.98

2.83

40

12

1

Sunday.

Jan. 13

49.10

0.30

3.98

2.93

110

51

2

8,500

1,200

43

Jan. 14

48.20

0.33

3.99

3.04

210

113

4

16,000

6,000

280

Jan. 15

46.40

0.35

3.98

3.21

325

222

15

24,000

9,500

700

Jan. 16

50.00

0.40

3.98

3.49

360

247

42

28,000

14,000

900

Jan. 17

50.00

0.43

3.98

3.86

242

147

26

65,000

20,000

1,200

Jan. 18

50.00

0.46

3.91

3.99

137

73

7

7,000

6,500

400

Jan. 19

...

...

...

...

...

...

...

Sunday.

Jan. 20

Scraped.

Jan. 21

50.00

0.48

3.00

0.76

55

25

4

...

...

...

Jan. 22

50.00

0.48

3.01

0.60

49

21

4

3,600

1,900

150

Jan. 23

50.00

0.49

3.00

0.57

40

15

3

1,800

700

170

Jan. 24

50.00

0.49

2.99

0.60

40

13

3

2,300

950

90

Jan. 25

50.00

0.50

2.99

0.65

39

12

3

1,100

800

95

Jan. 26

50.00

0.50

2.98

0.69

32

9

2

Sunday.

Jan. 27

50.00

0.51

2.99

0.76

32

9

2

300

700

70

Jan. 28

50.00

0.52

2.99

0.82

45

15

2

1,200

900

70

Jan. 29

50.00

0.55

2.99

0.90

60

26

2

1,000

1,400

95

Jan. 30

50.00

0.57

2.98

0.98

57

27

2

1,400

210

33

Jan. 31

50.00

0.58

2.98

1.08

42

18

2

1,100

750

45

Feb.   1

50.00

0.59

2.99

1.16

39

14

2

750

1,000

70

Feb.   2

49.10

0.60

2.99

1.22

27

9

2

Sunday.

Feb.   3

49.10

0.61

2.98

1.30

29

8

2

1,300

750

20

Feb.   4

50.00

0.64

2.99

1.40

25

6

2

600

900

60

Feb.   5

50.00

0.66

2.99

1.50

24

6

2

750

200

75

Feb.   6

50.00

0.67

2.99

1.55

20

5

2

2,000

800

60

Feb.   7

50.00

0.68

3.00

1.56

17

4

1

...

600

34

Feb.   8

50.00

0.69

3.00

1.53

15

4

1

900

220

35

Feb.   9

50.00

0.71

3.00

1.54

14

4

1

Sunday.

Feb. 10

50.00

0.72

2.99

1.60

11

4

1

850

500

28

Feb. 11

50.00

0.74

2.99

1.62

10

4

1

1,000

500

23

Feb. 12

50.00

0.75

2.98

1.68

8

4

1

750

290

18

Feb. 13

50.00

0.76

2.99

1.74

9

4

1

700

260

10

Feb. 14

48.20

0.76

2.99

1.77

9

4

1

1,200

250

27

Feb. 15

51.80

0.79

2.99

1.89

61

18

1

5,500

4,800

13

Feb. 16

48.20

0.79

2.99

2.08

80

40

2

Sunday.

Feb. 17

48.20

0.81

2.99

2.24

80

40

3

33,000

1,300

60

Feb. 18

47.30

0.82

2.99

2.31

130

65

3

...

950

120

Feb. 19

51.80

0.92

2.99

2.45

320

200

7

28,000

22,000

360

Feb. 20

52.70

0.99

2.99

2.61

177

97

9

22,000

16,300

350

Feb. 21

51.80

1.03

2.99

2.68

105

52

6

10,600

3,800

270

Feb. 22

50.90

1.07

2.99

2.72

85

42

5

Holiday.

Feb. 23

50.00

1.09

2.99

2.76

60

30

4

Sunday.

Feb. 24

51.80

1.12

2.99

2.80

46

19

3

3,600

1,700

120

Feb. 25

50.00

1.14

2.99

2.84

31

9

2

2,300

1,300

60

Feb. 26

50.00

1.17

3.00

2.87

30

8

2

3,800

1,300

43

Feb. 27

48.20

1.18

2.99

2.90

30

7

1

1,300

900

42

Feb. 28

47.30

1.19

2.99

2.94

37

7

1

1,400

800

31

Feb. 29

51.80

1.23

2.99

3.01

123

49

2

13,500

750

35

Mar.   1

48.20

1.20

2.98

2.99

97

44

5

Sunday.

Mar.   2

50.00

1.28

2.99

3.12

82

35

4

8,000

2,500

70

Mar.   3

50.90

1.32

2.98

3.22

87

38

4

11,000

6,000

55

Mar.   4

50.00

1.33

2.99

3.28

67

29

3

6,000

1,400

38

Mar.   5

50.00

1.35

2.99

3.32

59

23

3

4,400

2,500

37

Mar.   6

Discontinued; sand filter being used for sedimentation experiments.

FIGURE 9—DETAIL OF STRAINER SYSTEM.

TABLE 19—RECORD OF EXPERIMENTAL FILTER PLANT. No. 3.

Date.

SAND FILTER.

TURBIDITY.

BACTERIA.

COAGULANT.

Rate.

Loss of head.

Applied water.

Effluent, coagulant.

Effluent, sand.

Applied water.

Effluent, coagulant.

Effluent, sand.

Grains, per gallon.

1907.

Feb.   12

2.99

0.18

14

...

2

...

...

...

...

Feb.   13

3.00

0.17

15

...

2

600

...

...

...

Feb.   14

3.19

0.18

15

...

2

650

...

...

...

Feb.   15

3.86

0.22

12

...

2

600

...

2,500

...

Feb.   16

3.84

0.29

14

...

2

850

...

1,600

...

Feb.   17

...

...

...

...

...

...

...

...

...

Feb.   18

...

...

...

...

...

1,200

...

300

...

Feb.   21

3.91

0.32

20

...

2

1,800

...

550

...

Feb.   22

3.95

0.39

15

...

2

2

Holiday.

Feb.   23

3.94

0.43

20

...

3

1,600

...

1,100

...

Feb.   24

3.89

0.47

20

...

3

3

Sunday.

Feb.   25

4.19

0.52

20

...

3

1,400

...

600

...

Feb.   26

4.13

0.57

20

...

3

700

...

650

...

Feb.   27

3.32

0.62

17

...

3

700

...

2,300

...

Feb.   28

4.41

0.67

15

...

3

800

...

550

...

Mar.   1

3.91

0.72

15

...

3

650

...

300

...

Mar.   2

3.93

0.79

15

...

3

1,000

...

270

...

Mar.   3

3.90

0.82

31

...

3

Sunday.

Mar.   4

3.92

0.80

35

...

3

1,200

...

140

1.45

Mar.   5

3.96

0.98

135

...

4

13,000

...

190

1.94

Mar.   6

4.05

1.25

135

29

2

18,000

2,100

160

2.03

Mar.   7

3.95

1.52

102

15

1

24,000

3,500

160

1.50

Mar.   8

3.90

1.67

100

15

1

22,000

1,800

130

1.38

Mar.   9

3.93

1.80

90

15

1

24,000

3,500

130

1.37

Mar. 10

3.95

1.91

82

16

1

Sunday.

1.26

Mar. 11

3.96

2.08

68

18

1

18,000

6,000

120

1.24

Mar. 12

4.02

2.19

46

18

1

11,000

9,000

140

1.08

Mar. 13

4.02

2.31

40

15

1

9,000

5,000

120

0.94

Mar. 14

3.96

2.44

39

16

1

5,500

3,600

90

0

Mar. 15

4.07

2.42

35

20

1

6,500

3,800

85

0

Mar. 16

3.85

2.20

60

29

1

5,000

3,500

100

1.26

Mar. 17

3.95

2.21

135

25

1

Sunday.

1.52

Mar. 18

3.88

2.86

170

25

1

9,000

1,900

85

1.75

Mar. 19

3.82

3.31

125

21

1

7,000

700

65

1.57

Mar. 20

3.78

3.47

102

20

1

4,800

1,500

60

1.31

Mar. 21

3.71

3.70

125

20

1

8,500

1,500

70

1.38

Mar. 22

3.64

3.81

190

25

1

7,500

1,100

35

1.57

Mar. 23

3.58

3.95

180

26

1

7,500

470

55

1.68

Mar. 24

3.46

4.18

140

19

1

Sunday.

1.52

Mar. 25

Scraped, 1.03 in. of sand removed.

Mar. 27

4.06

0.22

47

8

1

2,200

480

60

1.08

Mar. 28

4.02

0.37

35

...

0

1,300

250

80

1.00

Mar. 29

4.02

0.46

26

...

...

700

240

65

0

Mar. 30

Shut down to fill coagulant basin.

...

...

25

...

...

310

...

...

0

Mar. 31

4.00

0.45

21

15

1

Sunday.

0

Apr.   1

3.39

0.42

20

15

1

600

1,000

43

0

Apr.   2

3.06

0.46

24

17

1

270

Lost.

35

0

Apr.   3

3.01

0.49

24

17

1

460

"

41

0

Apr.   4

2.95

0.50

20

15

1

280

550

27

0

Apr.   5

2.95

0.51

20

13

1

450

1,000

60

0

Apr.   6

2.96

0.49

20

12

1

320

50

35

0

Apr.   7

2.99

0.48

20

12

1

Sunday.

0

Apr.   8

3.01

0.49

18

12

1

330

650

22

0

Apr.   9

3.01

0.55

18

12

1

140

750

21

0

Apr. 10

3.02

0.57

30

15

0

750

5,000

29

0

Apr. 11

3.04

0.61

66

16

0

4,000

550

25

1.11

Apr. 12

3.09

0.72

72

13

0

14,000

2,200

17

1.15

Apr. 13

3.07

0.88

80

19

0

13,000

3,900

25

1.14

Apr. 14

2.98

1.04

77

18

1

Sunday.

1.17

Apr. 15

2.97

1.20

62

18

1

7,060

2,200

19

1.09

Apr. 16

3.01

1.32

47

17

1

3,600

900

22

1.08

Apr. 17

3.05

1.44

39

19

0

1,600

1,100

12

0

Apr. 18

3.04

1.41

30

20

1

1,810

1,870

14

0

Apr. 19

3.04

1.35

25

18

1

790

910

14

0

Apr. 20

3.07

1.30

20

15

1

540

480

15

0

Apr. 21

3.07

1.26

20

15

1

Sunday.

...

Apr. 22

3.04

1.21

18

12

0

235

420

21

0

Apr. 23

3.06

1.22

15

10

0

170

420

8

0

Apr. 24

2.99

1.26

19

10

0

150

250

17

0

Apr. 25

3.04

1.27

34

12

0

700

260

19

0

Apr. 26

3.07

1.28

46

12

0

1,200

320

80

0

Apr. 27

2.94

1.49

52

...

0

1,700

1,500

70

0

Apr. 28

2.96

1.88

45

...

1

Sunday.

0

Apr. 29

2.99

2.40

44

33

1

600

1,400

19

0

Apr. 30

3.00

2.83

39

29

1

550

1,200

14

0

May   1

3.01

2.71

31

21

1

500

1,300

20

0

May   2

3.01

2.51

24

15

1

500

850

16

0

May   3

3.00

2.36

19

12

1

280

650

34

0

May   4

3.01

2.29

16

10

0

400

550

24

0

May   5

3.01

2.25

15

9

0

Sunday.

0

May   6

3.06

2.32

13

8

0

390

460

80

0

May   7

2.96

2.46

12

7

0

190

...

18

0

May   8

3.00

2.51

10

5

0

...

...

...

0

May   9

3.00

2.77

10

5

0

390

1,100

14

0

May 10

3.01

2.87

10

5

0

300

500

21

0

May 11

2.99

3.16

12

6

0

390

650

16

0

May 12

3.00

3.34

17

7

0

Sunday.

0

May 13

3.00

3.44

35

9

0

600

470

27

0

May 14

3.01

3.46

39

12

0

500

550

25

0

May 15

3.01

3.56

17

...

0

500

900

23

0

May 16

2.93

4.07

24

...

0

290

2,500

25

0

May 17

3.01

4.34

18

...

0

260

2,000

16

0

May 18

2.93

4.25

15

8

0

190

600

19

0

May 19

2.97

4.36

12

8

0

Sunday.

0

May 20

3.01

4.64

12

8

0

260

450

15

0

May 21

2.99

4.55

16

8

0

260

330

14

0

May 22

3.01

4.57

20

8

0

280

390

22

0

May 23

3.00

4.51

15

8

0

130

240

19

0

May 24

2.98

4.44

15

8

0

170

240

30

0

May 25

3.00

4.38

15

8

0

340

400

41

0

May 26

3.00

4.38

18

8

0

Sunday.

0

May 27

Shut down to scrape sand filter; 1.09 in. of sand removed.

May 28

Cleaning coagulant basin and treating coagulant basin with 1:2,000,000 solution of copper sulphate.

May 29

16

...

...

solution of copper sulphate.

May 30

3.00

0.11

14

8

1

Holiday.

0

May 31

3.01

0.10

17

8

1

380

18,000

150

0

June   1

3.01

0.09

15

8

1

900

7,000

150

0

June   2

3.01

0.10

17

8

1

Sunday.

0

June   3

3.01

0.10

24

10

1

550

8,000

130

0

June   4

3.04

0.11

37

13

1

6,500

7,500

140

0

June   5

3.00

0.11

65

29

1

3,200

3,600

110

0

June   6

3.00

0.11

77

46

1

1,500

800

60

1.17

June   7

2.99

0.12

64

21

1

2,100

1,500

90

1.18

June   8

2.98

0.17

46

22

1

660

1,000

60

0

June   9

3.00

0.18

44

30

1

Sunday.

0

June 10

3.01

0.18

36

26

1

240

400

32

0

June 11

3.00

0.17

30

20

1

280

300

31

0

June 12

3.00

0.17

34

22

1

330

...

28

0

June 13

2.99

0.17

35

25

1

480

480

39

0

June 14

2.98

0.17

31

22

1

440

550

32

0

June 15

2.99

0.19

32

22

1

420

450

27

0

June 16

3.02

0.21

26

18

1

Sunday.

0

June 17

2.99

0.23

26

16

1

340

750

14

0

June 18

3.02

0.25

31

20

1

440

750

21

0

June 19

3.02

0.29

37

27

1

500

460

35

0

June 20

3.00

0.32

30

21

1

330

440

88

0

June 21

3.01

0.36

25

16

1

170

370

23

0

June 22

3.00

0.40

20

12

1

100

300

17

0

June 23

2.97

0.43

26

11

1

Sunday.

0

June 24

2.97

0.44

140

36

1

1,700

350

22

1.59

June 25

3.02

0.45

130

27

1

400

250

16

1.55

June 26

Interrupted, defective meter.

750

330

...

0

June 27

3.00

0.43

65

15

0

...

1,400

...

0

June 28

3.00

0.44

47

19

0

...

1,400

120

0

June 29

2.99

0.44

37

20

0

220

300

...

0

June 30

2.97

0.42

30

19

0

Sunday.

0

July   1

2.99

0.37

30

18

0

400

600

85

0

July   2

3.01

0.33

32

19

0

180

1,000

50

0

July   3

3.00

0.31

36

21

0

350

310

21

0

July   4

3.00

0.30

44

30

0

Holiday.

July   5

3.00

0.29

44

35

0

550

400

41

0

July   6

3.00

0.28

39

30

0

250

280

22

0

July   7

3.00

0.28

34

24

0

Sunday.

0

July   8

3.00

0.28

25

16

0

220

260

27

0

July   9

3.00

0.27

22

13

0

50

40

19

0

July 10

2.98

0.27

47

27

1

Lost.

Lost.

Lost.

0

July 11

3.00

0.27

90

41

1

150

50

8

1.27

July 12

3.00

0.29

97

21

1

300

200

13

1.27

July 13

3.00

0.34

90

20

0

220

160

17

1.27

July 14

3.00

0.40

90

19

0

Sunday.

1.27

July 15

3.00

0.54

95

18

0

375

150

1.27

July 16

3.00

0.59

120

20

0

Lost.

50

Lost.

1.36

July 17

3.00

0.58

85

16

0

270

60

3

1.26

July 18

2.99

0.61

56

13

0

1,675

70

1.17

July 19

3.01

0.61

41

18

0

450

700

11

0

July 20

2.99

0.51

62

27

0

300

720

8

0

July 21

3.00

0.47

62

32

0

Sunday.

0

July 22

3.00

0.47

80

34

0

1,400

560

14

1.17

July 23

3.01

0.49

105

21

0

3,700

490

40

1.25

July 24

3.01

0.60

95

19

0

770

110

80

1.27

July 25

3.00

0.68

77

16

0

250

80

5

1.22

July 26

2.99

0.68

67

17

0

140

40

4

0

July 27

3.00

0.69

54

20

0

300

130

21

0

July 28

3.00

0.72

46

27

0

Sunday.

0

July 29

3.00

0.74

36

26

0

470

290

100

0

July 30

2.99

0.76

29

19

0

Lost.

Lost.

Lost.

0

July 31

2.99

0.77

21

12

0

Lost.

Lost.

Lost.

0

Aug.   1

3.00

0.75

16

9

0

Lost.

Lost.

Lost.

0

Aug.   2

3.00

0.74

15

8

0

130

140

4

0

Aug.   3

3.00

0.74

16

7

0

120

180

6

0

Aug.   4

3.00

0.75

21

6

0

Sunday.

Aug.   5

3.00

0.76

29

8

0

230

100

44

0

Aug.   6

3.00

0.79

34

12

0

85

470

...

0

Aug.   7

2.99

1.01

21

12

0

200

450

...

0

Aug.   8

3.00

1.31

19

11

0

100

180

45

0

Aug.   9

2.98

1.44

16

9

0

75

80

16

0

Aug. 10

3.00

1.44

24

9

0

60

90

11

0

Aug. 11

3.00

1.49

62

22

0

Sunday.

Aug. 12

3.00

1.62

120

39

0

620

260

16

1.45

Aug. 13

2.97

2.06

107

22

0

820

520

10

1.38

Aug. 14

2.97

3.06

82

19

0

850

120

26

1.22

Aug. 15

2.81

3.91

65

15

0

150

260

6

1.17

Aug. 16

3.00

4.29

45

18

0

270

340

17

0

Aug. 17

3.00

3.86

35

22

0

340

200

13

0

Aug. 18

3.00

3.47

21

13

0

Sunday.

Aug. 19

3.00

3.49

18

10

0

180

220

17

0

Aug. 20

3.00

3.56

20

8

0

210

180

16

0

Aug. 21

3.00

3.58

20

10

0

1,300

650

8

0

Aug. 22

2.99

3.73

27

13

0

3,800

360

6

0

Aug. 23

3.00

4.00

49

34

0

2,500

700

10

0

Aug. 24

3.00

4.05

36

26

0

3,900

630

12

0

Aug. 25

2.98

4.06

34

24

0

Sunday.

Aug. 26

3.00

4.20

21

13

0

700

310

16

0

Aug. 27

3.00

4.31

19

11

0

470

250

12

0

Aug. 28

2.99

4.40

18

10

0

500

160

18

0

Aug. 29

3.01

4.41

17

9

0

360

110

9

0

Aug. 30

2.98

4.46

15

8

0

320

310

14

0

Aug. 31

Scraped. 1.88 in. of sand removed.

13

...

...

200

100

...

0

Sept.   5

3.00

0.10

34

4

0

360

950

...

1.04

Sept.   6

3.00

0.10

160

3

0

15,000

1,500

190

1.35

Sept.   7

3.00

0.09

64

3

0

2,000

260

100

1.20

Sept.   8

3.00

0.08

56

4

0

Sunday.

...

1.04

Sept.   9

3.00

0.08

59

3

0

220

180

38

1.04

Sept. 10

2.97

0.07

57

3

0

18,000

150

29

1.06

Sept. 11

2.98

0.07

65

2

0

2,700

200

37

1.04

Sept. 12

2.98

0.08

72

2

0

1,000

125

19

1.04

Sept. 13

3.00

0.08

87

3

0

2,300

200

72

1.20

Sept. 14

3.00

0.08

72

3

0

2,400

360

36

1.12

Sept. 15

3.00

0.08

65

3

0

Sunday.

1.04

Sept. 16

3.00

0.08

65

2

0

Lost.

Lost.

38

1.04

Sept. 17

3.00

0.08

52

2

0

420

200

38

1.07

Sept. 18

3.00

0.08

60

2

0

900

200

17

1.07

Sept. 19

2.98

0.08

85

2

0

2,000

220

25

1.12

Sept. 20

2.98

0.09

100

2

0

4,200

320

31

1.24

Sept. 21

2.99

0.09

120

3

0

1,100

160

19

1.33

Sept. 22

3.00

0.09

137

3

0

Sunday.

1.45

Sept. 23

3.02

0.09

112

4

0

2,100

190

15

1.41

Sept. 24

3.00

0.10

100

4

0

4,000

620

13

1.33

Sept. 25

3.00

0.11

432

3

0

56,000

290

7

1.83

Sept. 26

2.99

0.11

385

2

0

1,300

950

19

2.34

Sept. 27

3.00

0.12

245

4

0

4,000

Lost.

20

1.91

Sept. 28

2.98

0.13

127

4

0

15,000

1,000

8

1.54

Sept. 29

2.98

0.14

105

4

0

Sunday.

1.34

Sept. 30

2.99

0.15

115

3

0

Lost.

Lost.

46

1.35

Oct.   1

3.00

0.15

82

3

0

600

1,700

22

1.24

Oct.   2

2.98

0.16

65

3

0

4,400

550

8

1.09

Oct.   3

3.00

0.17

59

2

0

900

330

15

1.04

Oct.   4

2.99

0.17

55

2

0

850

250

11

1.03

Oct.   5

2.99

0.19

59

2

0

2,000

450

25

1.04

Oct.   6

2.98

0.20

59

2

0

Sunday.

1.04

Oct.   7

2.98

0.21

52

2

0

1,250

2,300

42

1.04

Oct.   8

2.97

0.21

54

2

0

11,000

100

15

1.04

Oct.   9

2.98

0.22

51

2

0

2,000

1,600

7

1.04

Oct. 10

2.98

0.24

50

2

0

800

Lost.

24

1.04

Oct. 11

2.98

0.25

47

2

0

2,000

1,200

21

0

Oct. 12

2.97

0.26

36

3

0

1,200

1,200

19

0

Oct. 13

2.98

0.27

40

4

0

Sunday.

0

Oct. 14

2.98

0.29

47

5

0

1,200

830

25

0

Oct. 15

2.99

0.31

41

5

0

900

Lost.

105

0

Oct. 16

2.99

0.32

35

4

0

Lost.

550

19

0

Oct. 17

2.98

0.34

30

4

0

550

800

21

0

Oct. 18

3.00

0.35

25

4

0

260

350

9

0

Oct. 19

3.00

0.35

25

4

0

750

310

35

0

Oct. 20

3.00

0.35

20

3

0

Sunday.

0

Oct. 21

3.00

0.35

19

3

0

480

540

35

0

Oct. 22

2.99

0.36

18

3

0

230

440

17

0

Oct. 23

2.99

0.37

15

3

0

250

440

39

0

Oct. 24

2.98

0.38

15

3

0

300

500

60

0

Oct. 25

2.99

0.39

15

3

0

450

410

65

0

Oct. 26

2.99

0.40

15

3

0

450

500

44

0

Oct. 27

2.99

0.41

13

2

0

Sunday.

0

Oct. 28

2.99

0.43

13

2

0

190

500

50

0

Oct. 29

2.98

0.44

25

2

0

380

60

75

0

Oct. 30

2.99

0.46

21

2

0

450

180

3

0

Oct. 31

2.96

0.48

25

3

0

2,300

390

75

0

Nov.   4

3.00

0.51

125

2

0

...

...

...

0

Nov.   5

3.00

0.53

185

2

0

6,000

1,600

90

1.70

Nov.   6

2.99

0.56

170

2

0

5,000

3,900

6

1.70

Nov.   7

2.99

0.60

100

3

0

14,000

300

9

1.48

Nov.   8

2.99

0.64

95

3

0

1,900

230

2

1.27

Nov.   9

2.99

0.70

80

4

0

4,000

2,700

200

0

Nov. 10

2.99

0.79

67

4

0

Sunday.

0

Nov. 11

2.99

1.00

52

6

0

1,900

2,000

200

0

Nov. 12

2.99

1.46

40

9

0

7,500

2,300

160

0

Nov. 13

2.98

2.09

36

10

0

1,600

1,100

170

0

Nov. 14

2.99

2.74

42

9

0

2,700

950

130

0

Nov. 15

2.99

2.98

35

8

0

1,800

800

11

0

Nov. 16

2.99

3.03

26

8

0

1,100

800

90

0

Nov. 17

3.00

3.07

20

6

0

Sunday.

0

Nov. 18

3.00

3.09

17

5

0

1,600

700

100

0

Nov. 20

2.99

3.17

45

3

0

6,500

120

120

0

Nov. 21

2.99

3.22

52

3

0

9,900

1,000

80

0

Nov. 22

2.99

3.27

65

5

0

10,000

3,200

90

0

Nov. 23

2.99

3.33

49

8

0

18,000

2,400

100

0

Nov. 24

2.99

3.41

134

11

0

Sunday.

0

Nov. 25

2.98

3.54

225

12

1

50,000

2,100

65

1.68

Nov. 26

2.98

3.68

237

13

1

40,000

2,400

95

1.76

Nov. 27

2.99

3.96

185

16

1

16,000

2,600

60

1.74

Nov. 28

2.98

4.29

130

18

1

Holiday.

1.57

Nov. 29

2.97

4.48

80

19

1

10,000

2,500

65

1.50

Nov. 30

2.97

4.54

54

15

1

3,800

1,900

85

0

Dec.   6

Scraped, 1.62 in. of sand removed.

Dec.   8

2.97

0.16

12

3

0

Sunday.

1.17

Dec.   9

2.98

0.16

11

3

0

1,200

410

10

1.17

Dec. 10

2.98

0.15

12

3

0

800

550

150

1.17

Dec. 11

2.99

0.15

255

3

0

6,500

600

130

1.52

Dec. 12

3.00

0.13

212

2

0

48,000

500

130

1.99

Dec. 13

2.98

0.13

495

4

0

42,000

500

120

2.06

Dec. 14

2.99

0.14

357

5

0

49,000

750

150

2.12

Dec. 15

2.99

0.15

157

6

0

Sunday.

1.69

Dec. 16

2.98

0.16

90

9

0

19,000

900

20

1.28

Dec. 17

2.98

0.20

70

12

0

21,000

400

170

1.17

Dec. 18

2.98

0.24

49

12

1

6,500

7,000

350

1.17

Dec. 19

2.98

0.29

39

9

1

Lost.

Lost.

Lost.

1.17

Dec. 20

2.98

0.36

42

7

1

Lost.

Lost.

Lost.

1.17

Dec. 21

2.97

0.45

26

5

0

Lost.

Lost.

Lost.

1.17

Dec. 22

2.98

0.57

20

4

0

Sunday.

1.17

Dec. 23

2.98

0.71

34

3

0

1,400

1,300

220

1.17

Dec. 24

2.98

0.83

195

2

0

9,000

1,000

140

1.49

Dec. 25

2.98

0.97

445

2

0

Holiday.

2.43

Dec. 26

2.98

1.11

370

2

0

51,000

1,000

39

2.15

Dec. 27

2.98

1.27

245

3

0

55,000

1,600

70

1.91

Dec. 28

2.98

1.40

102

4

0

10,000

1,000

80

1.50

Dec. 29

2.98

1.60

75

3

0

Sunday.

1.21

Dec. 30

2.97

1.85

56

3

0

4,400

700

80

1.17

Dec. 31

2.98

2.07

39

2

0

14,000

1,200

65

1.17

1908.

Jan.   1

2.99

2.11

31

2

0

Holiday.

1.17

Jan.   2

2.98

2.17

39

2

0

4,400

700

19

1.17

Jan.   3

2.98

2.26

36

2

0

3,100

1,000

13

1.17

Jan.   4

2.98

2.34

32

2

0

2,400

550

19

1.17

Jan.   5

2.98

2.41

26

2

0

Sunday.

1.17

Jan.   6

2.98

2.49

20

2

0

600

230

18

1.17

Jan.   7

2.98

2.58

20

2

0

1,100

370

12

1.17

Jan.   8

2.99

2.61

22

2

0

1,900

1,100

20

1.17

Jan.   9

2.99

2.63

45

2

0

13,000

1,200

22

1.21

Jan. 10

2.98

2.67

70

2

0

10,000

700

16

1.17

Jan. 11

2.98

2.72

56

2

0

16,000

1,200

11

1.17

Jan. 12

2.98

2.78

40

2

0

Sunday.

1.17

Jan. 13

2.98

2.84

110

2

0

8,500

90

6

1.27

Jan. 14

2.98

2.95

210

2

0

16,000

150

23

1.56

Jan. 15

2.98

3.07

325

3

0

24,000

1,100

19

1.92

Jan. 16

2.98

3.23

360

5

6

28,000

1,000

14

2.10

Jan. 17

2.97

3.73

242

6

0

65,000

490

23

1.91

Jan. 18

2.98

4.42

137

6

0

7,000

1,600

14

1.66

Jan. 19

2.99

4.75

117

5

0

Sunday.

1.50

Jan. 21

Scrape, 1.45 in. of sand removed.

Jan. 23

3.00

0.14

40

3

0

...

...

...

1.17

Jan. 24

3.00

0.14

40

3

0

2,300

550

55

1.17

Jan. 25

3.00

0.13

39

3

0

1,100

850

95

0

Jan. 26

3.00

0.13

32

3

0

Sunday.

0

Jan. 27

3.00

0.13

32

2

0

300

280

60

0

Jan. 28

2.99

0.15

45

3

0

1,200

700

70

0

Jan. 29

2.99

0.20

69

6

1

1,000

900

75

0

Jan. 30

2.99

0.24

57

8

1

1,400

650

50

0

Jan. 31

2.99

0.30

42

6

1

1,100

600

36

0

Feb.   1

2.99

0.34

39

5

1

750

50

25

0

Feb.   2

2.99

0.41

27

4

1

Sunday.

0

Feb.   3

2.99

0.51

29

3

0

1,300

220

16

0

Feb.   4

2.99

0.56

25

3

0

600

370

10

0

Feb.   5

2.99

0.58

24

4

0

750

700

21

0

Feb.   6

2.99

0.61

20

6

0

2,000

650

4

0

Feb.   7

3.00

0.64

17

8

1

...

410

26

0

Feb.   8

2.99

0.66

15

8

1

900

160

42

0

Feb.   9

3.00

0.67

14

8

1

Sunday.

0

Feb. 10

2.99

0.67

11

8

1

850

450

18

0

Feb. 11

3.00

0.66

10

7

1

1,000

600

26

0

Feb. 12

3.01

0.64

8

6

1

750

350

16

0

Feb. 13

3.00

0.62

9

5

1

700

120

10

0

Feb. 14

3.00

0.61

9

5

1

1,200

950

43

0

Feb. 15

3.00

0.60

61

5

1

5,500

1,000

23

0

Feb. 16

3.00

0.60

80

6

1

Sunday.

0

Feb. 17

3.00

0.62

80

14

1

33,000

6,100

36

0

Feb. 18

2.99

0.67

130

20

1

...

2,000

11

0

Feb. 19

2.99

0.76

320

18

2

28,000

9,000

120

0

Feb. 20

2.99

0.83

177

15

2

22,000

8,500

190

0

Feb. 29

3.00

0.85

123

8

1

...

...

...

0

Mar.   1

3.00

0.87

97

9

1

Sunday.

0

Mar.   2

2.99

0.92

82

13

1

8,000

4,400

50

0

Mar.   3

2.98

0.96

87

19

1

11,000

2,100

26

0

Mar.   4

2.99

1.02

67

21

1

6,000

4,700

7

0

Mar.   5

2.99

1.08

59

25

1

4,400

10,000

36

0

Mar.   6

2.99

1.15

72

25

2

7,000

7,400

50

0

Mar.   7

2.98

1.21

82

25

2

9,500

6,500

28

0

Mar.   8

2.99

1.25

92

29

2

Sunday.

0

Mar.   9

2.99

1.30

125

34

2

11,000

4,800

25

0

Mar. 10

2.99

1.35

142

39

2

8,500

1,200

23

0

Mar. 11

2.99

1.39

155

35

2

6,500

2,400

20

0

Mar. 12

2.99

1.42

135

29

2

5,900

1,500

11

0

Mar. 13

2.99

1.46

122

19

2

1,900

1,100

12

0

Mar. 14

2.99

1.47

97

12

1

1,800

700

6

0

Mar. 15

2.99

1.48

77

8

1

Sunday.

0

Mar. 16

3.00

1.52

65

9

0

1,400

700

8

0

Mar. 17

2.99

1.66

59

7

0

900

800

11

0

Mar. 18

2.99

1.72

67

11

1

1,000

650

8

0

Mar. 19

2.99

1.75

60

24

1

...

600

18

0

Mar. 20

2.99

1.81

57

25

1

1,300

750

20

0

Mar. 21

2.99

1.89

67

22

1

800

480

18

0

Mar. 22

2.99

1.95

80

21

1

Sunday.

0

Mar. 23

3.00

2.00

90

26

1

4,600

440

19

0

Mar. 24

2.98

2.06

82

32

1

2,500

1,200

10

0

Mar. 25

2.99

2.17

67

39

1

1,600

650

20

0

Mar. 26

2.99

2.24

60

36

1

550

410

7

0

Mar. 27

2.99

2.29

59

30

1

900

900

29

0

Mar. 28

3.00

2.32

51

21

1

650

250

42

0

Mar. 29

2.99

2.35

31

18

1

Sunday.

0

Mar. 30

3.00

2.38

30

14

1

500

650

28

0

Mar. 31

2.99

2.43

39

9

1

750

290

30

0

Apr.   1

2.99

2.50

44

7

1

750

390

32

0

Apr.   2

2.99

2.58

42

8

1

1,100

280

47

0

Apr.   3

2.99

2.65

41

11

1

1,500

550

70

0

Apr.   4

2.99

2.74

54

12

1

700

380

4

0

Apr.   5

3.00

2.82

50

12

1

Sunday.

0

Apr.   6

2.99

2.88

41

14

1

440

150

4

0

Apr.   7

2.99

2.98

35

13

1

650

270

42

0

Apr.   8

2.98

3.15

39

11

1

550

210

65

0

Apr.   9

2.99

3.35

40

8

1

390

160

95

0

Apr. 10

2.98

3.50

40

8

1

500

130

130

0

Apr. 11

2.99

3.65

45

7

0

430

145

100

0

Apr. 12

2.99

3.79

52

5

0

Sunday.

0

Apr. 13

2.99

3.92

50

4

0

490

160

80

0

Apr. 14

2.99

4.05

45

4

0

550

170

90

0

Apr. 15

2.99

4.16

45

3

0

420

160

12

0

Apr. 16

...

4.24

45

3

0

360

130

90

0

Apr. 21

Scraped, 0.12 in. of sand removed.

Apr. 23

...

0.13

25

2

0

140

140

...

0

Apr. 24

3.00

0.12

21

2

0

200

Lost.

150

0

Apr. 25

3.00

0.10

20

2

0

85

550

45

0

Apr. 26

3.00

0.10

21

3

0

Sunday.

0

Apr. 27

3.00

0.10

18

3

0

95

850

50

0

Apr. 28

3.00

0.10

20

3

0

70

220

48

0

Apr. 29

3.00

0.09

24

3

0

110

210

95

0

Apr. 30

3.00

0.09

21

3

0

70

140

29

0

May   1

3.00

0.09

32

3

0

130

210

65

0

May   2

3.00

0.09

26

3

0

140

140

55

0

May   3

3.00

0.11

22

5

0

Sunday.

0

May   4

3.00

0.11

19

4

0

85

210

75

0

May   5

3.00

0.11

18

4

0

130

150

48

0

May   6

2.99

0.12

18

3

0

230

430

50

0

May   7

3.00

0.13

19

3

0

160

90

40

0

May   8

3.00

0.14

19

3

0

375

425

7

0

May   9

2.99

0.14

18

3

0

1,209

180

6

0

May 10

3.00

0.14

30

3

0

Sunday.

0

May 11

3.00

0.13

60

3

0

2,800

150

12

0

May 12

3.00

0.13

70

3

0

2,900

225

26

0

May 13

3.00

0.13

66

7

0

1,800

450

53

0

May 14

3.00

0.14

45

9

0

2,700

550

10

0

May 15

2.99

0.14

39

7

0

950

300

65

0

May 16

2.99

0.22

49

6

0

800

250

49

0

May 17

2.99

0.33

46

4

0

Sunday.

0

May 18

2.99

0.44

31

3

0

700

1,700

80

0

May 19

2.98

0.62

36

3

0

375

950

53

0

May 20

2.99

0.75

41

3

0

425

700

46

0

May 21

2.99

0.89

31

4

0

300

600

6

0

May 22

2.99

1.01

50

5

0

950

230

17

0

May 23

2.99

1.12

127

5

0

2,400

32

28

0

May 24

2.99

1.20

110

6

0

Sunday.

0

May 25

2.99

1.24

90

9

0

1,100

850

9

0

May 26

2.98

1.31

135

11

0

3,200

150

17

0

May 27

2.97

1.54

110

12

0

1,450

175

8

0

May 28

2.97

1.81

90

10

0

1,000

132

7

0

May 29

2.97

2.08

70

7

0

1,100

230

8

0

May 30

2.97

2.36

50

5

0

Holiday.

0

May 31

2.98

2.63

34

4

0

Sunday.

0

June   1

2.98

2.77

35

2

0

...

...

...

0

June   2

2.98

2.84

39

2

0

...

...

...

0

June   3

2.98

3.02

35

3

0

...

...

...

0

June   4

3.00

3.01

30

4

0

...

...

...

0

June   5

3.00

2.97

30

5

0

...

...

...

0

June   6

3.01

2.81

27

5

0

...

...

...

0

June   7

3.01

2.62

22

5

0

...

...

...

0

June   8

3.01

2.38

20

4

0

...

...

...

0

June   9

3.00

2.19

20

3

0

...

...

...

0

June 10

3.01

2.02

17

3

0

...

...

...

0

June 11

2.99

1.89

12

3

0

...

...

...

0

June 12

2.98

1.92

11

2

0

...

...

...

0

June 13

2.98

1.99

36

2

0

...

...

...

0

June 14

2.98

2.08

39

2

0

...

...

...

0

June 15

2.98

2.25

25

4

0

...

...

...

0

June 16

2.98

2.54

34

5

0

...

...

...

0

June 17

2.97

2.85

64

5

0

...

...

...

0

June 18

2.97

3.20

57

5

0

...

...

...

0

June 19

2.98

3.47

46

7

0

...

...

...

0

June 20

2.99

3.73

37

8

0

...

...

...

0

June 21

2.99

4.10

29

8

0

...

...

...

0

June 22

2.99

4.44

25

6

0

...

...

...

0

June 23

2.99

4.61

25

5

0

...

...

...

0

June 26

3.01

0.09

15

2

0

...

...

...

0

June 27

3.00

0.09

12

2

0

...

...

...

0

June 28

3.00

0.09

9

2

0

...

...

...

0

June 29

3.00

0.08

8

2

0

...

...

...

0

June 30

3.00

0.07

10

2

0

...

...

...

0

July   1

3.00

0.07

6

2

0

80

75

3

0

July   2

3.00

0.07

8

2

0

290

20

3

0

July   3

3.00

0.07

8

2

0

350

140

4

0

July   4

3.00

0.07

9

2

0

Holiday.

0

July   5

3.00

0.07

10

2

0

Sunday.

0

July   6

3.00

0.07

9

2

0

300

52

4

0

July   7

3.00

0.07

8

2

0

110

35

2

0

July   8

3.00

0.07

9

2

0

85

105

2

0

July   9

3.00

0.07

8

2

0

85

80

3

0

July 10

...

...

...

...

...

300

65

1

0

July 11

3.00

0.08

12

2

0

145

95

11

0

July 12

3.00

0.08

11

2

0

Sunday.

0

July 13

3.00

0.08

10

2

0

115

105

7

0

July 14

3.00

0.09

16

2

0

800

34

1

0

July 15

3.00

0.09

17

2

0

180

165

3

0

July 16

3.00

0.10

14

2

6

100

95

2

0

July 17

3.00

0.10

10

2

0

65

65

1

0

July 18

3.00

0.11

11

2

0

38

200

24

0

July 19

3.00

0.11

12

2

0

Sunday.

0

July 20

3.00

0.12

10

2

0

95

31

1

0

July 21

3.00

0.12

10

2

0

70

100

2

0

July 22

3.00

0.13

13

2

0

450

13

4

0

July 23

2.99

0.13

54

2

0

650

325

4

0

July 24

2.99

0.14

305

2

0

1,650

325

...

0

July 25

3.00

0.15

330

4

0

2,600

55

2

0

July 26

3.00

0.15

290

9

0

Sunday.

0

July 27

3.00

0.16

335

11

0

35,000

1,200

6

0

July 28

2.99

0.17

170

10

0

1,200

675

6

0

July 29

3.00

0.17

180

8

0

2,000

270

11

0

July 30

2.99

0.18

237

7

0

800

190

2

0

July 31

3.00

0.19

250

6

0

1,000

310

6

0

TABLE 20—SUMMARY OF RESULTS OF EXPERIMENTAL FILTERS.

Filter number

Number of runs

1

3

2

6

3

11

4

12

5

25

6

28

Rate, million gallons per acre per day:

Maximum...............

1.35

3.95

7.96

12.60

37.5

118.9

Minimum................

0.62

2.30

3.73

5.77

6.68

7.1

Average.................

1.06

3.26

6.69

10.17

26.1

38.54

Length of run, in days:

Maximum...............

233.5

150.5

75.2

90.9

48.71

39.83

Minimum................

181.7

42.0

14.5

10.1

0.67

0.62

Average.................

206.4

109.6

48.89

40.5

14.41

12.61

Million gallons filtered per acre per run:

Maximum...............

242.61

484.46

534.67

960.72

1,463.35

1,022.27

Minimum................

202.60

135.66

93.79

92.57

19.53

53.32

Average.................

218.58

302.82

326.76

417.23

374.14

361.92

Cubic yards of sand removed per acre at end of each run:

Maximum...............

269

269

672

1,612

2,420

3,360

Minimum................

269

134

101

134

134

101

Average.................

269

213

272

392

583

635

Cubic yards of sand removed per acre per million gallons filtered..........

1.23

0.70

0.83

0.94

1.55

1.72

Average initial loss of head..........

0.07

0.19

0.51

0.78

3.88

5.38

Turbidity, influent:

Maximum...............

120

120

120

120

90

100

Minimum................

2

2

2

2

2

2

Average.................

20

20

21

22

18

19

Turbidity, effluent:

Maximum...............

11

13

17

18

30

30

Minimum................

0

0

0

0

0

0

Average.................

1

1

2

2

4

3

Percentage reduction..........

95.0

95.0

90.5

90.9

77.8

84.3

Bacteria, influent:

Maximum...............

180,000

180,000

180,000

110,000

180,000

37,500

Minimum................

22

20

22

20

25

24

Average.................

4,800

5,100

4,500

4,200

6,900

5,900

Bacteria, effluent:

Maximum...............

4,000

1,300

3,200

5,400

12,800

2,400

Minimum................

2

3

1

1

2

2

Average.................

160

85

110

120

190

180

Percentage,Reduction..........

96.7

98.3

97.6

97.3

97.3

97.0

Number of samples examined for bacillus coli in influent:

10 c.c. ...................

549

478

476

436

325

336

1 c.c. ...................

560

492

486

445

335

342

0.1 c.c. ................

525

459

452

413

318

317

0.01 c.c. ..............

511

443

439

405

308

304

0.001 c.c. ............

500

434

429

394

299

294

Number of samples examined for bacillus coli in effluent:

10 c.c. ...................

512

452

454

404

296

309

1 c.c. ...................

513

454

457

406

299

311

0.1 c.c. ................

480

419

426

383

271

286

0.01 c.c. ..............

478

406

410

367

261

276

0.001 c.c. ............

478

406

410

367

261

276

Number samples positive, influent:

10 c.c. ...................

226

211

201

258

136

152

1 c.c. ...................

127

123

116

108

81

93

0.1 c.c. ................

55

59

54

51

43

42

0.01 c.c. ..............

26

34

33

33

27

25

0.001 c.c. ............

6

6

5

6

3

3

Number samples positive, effluent:

10 c.c. ...................

100

109

134

98

94

106

1 c.c. ...................

51

61

55

56

46

50

0.1 c.c. ................

9

13

16

16

4

13

0.01 c.c. ..............

0

0

0

0

0

0

0.001 c.c. ............

0

0

0

0

0

0

Percentage of samples showing bacillus coli in influent:

10 c.c. ...................

41.2

44.2

42.2

59.2

41.9

45.2

1 c.c. ...................

22.7

25.0

23.9

24.3

24.2

27.2

0.1 c.c. ................

10.5

12.8

11.9

12.3

13.5

13.2

0.01 c.c. ..............

5.1

7.7

7.5

8.2

8.8

8.2

0.001 c.c. ............

1.2

1.4

1.2

1.5

1.0

1.0

Percentage of samples showing bacillus coli in effluent:

10 c.c. ...................

19.5

24.1

29.5

24.2

31.7

34.3

1 c.c. ...................

10.0

13.4

12.0

13.8

15.4

16.1

0.1 c.c. ................

1.9

3.1

3.8

4.2

1.5

4.5

0.01 c.c. ..............

0

0

0

0

0

0

0.001 c.c. ............

0

0

0

0

0

0

Cost per million gallons for sand handling..........

$0.43

$0.25

$0.29

$0.33

$0.54

$0.60

Interest charges at 3%..........

6.85

2.25

1.12

0.73

0.32

0.22

Total..........

7.28

2.50

1.41

1.06

0.86

.82

Coli tests presumptive.

DISCUSSION

ALLEN HAZEN, M. AM. SOC. C. E. (by letter).—This paper contains a most interesting and instructive record of the actual operation of a large filter plant, and also a record of a number of experiments. The author has described some useful arrangements for improving the efficiency or reducing the cost.

The utility of raking, as an intermediate treatment between scrapings, seems to have been clearly demonstrated. Its practical effect is to allow a greater quantity of water to be passed between scrapings, thereby saturating—if the term may be used—the surface layer with clay and other fine matter before removing it, instead of taking it off when only a thin surface layer of it has been thus saturated.

The large proportion of the total purification that takes place in passing through three reservoirs successively, holding in the aggregate a quantity of water equal to about 7 days' use, is very striking. Taking all the records, the percentage remaining after passing through these reservoirs, is as follows:

Sediment for the year, 1909-1910, Table 2

17%

Turbidities, 5-year average, Table 3

25%

Bacteria, 5-year average, Table 4

24%

Bacteria, selected winter months with high numbers in the raw water

20%

Bacteria, selected summer months with high numbers in the raw water

2.5%

There is considerable seasonal fluctuation in the results of settling and filtering, as is shown in Table 21.

TABLE 21—AVERAGE REMOVAL OF TURBIDITY AND BACTERIA BY WASHINGTON FILTERS FOR WHOLE PERIOD, ARRANGED BY SEASONS.

Winter.

Spring.

Summer.

Fall.

Year.

Turbidity, in parts per million:

raw

135

96

144

42

105

settled

33

28

27

15

26

filtered

4

3

1

0.5

2

Percentage left from:

settling

24

29

19

36

25

filtering

12

10

4

3

8

both

3

1

0.3

1

2

Bacteria per cubic centimeter:

raw

16,600

4,150

4,100

1,960

6,700

settled

6,300

980

160

270

1,940

filtered

149

29

18

22

54

Percentage left from:

settling

38

24

4

14

29

filtering

2.4

3.0

11.2

8.2

2.8

both

0.90

0.79

0.44

1.12

0.81

The fluctuation in the efficiency of the plant as a whole by seasons is greater with the turbidity than with the bacteria. During the winter the effluent contains 3% of the turbidity of the raw water, and in summer only 0.3 per cent. Most of this difference is represented by the increased efficiency of the filters in summer, and only a little of it by the increased efficiency of settling. With bacteria, on the other hand, the seasonal fluctuation of the plant as a whole is comparatively small, but the settling and storage processes are much more efficient in summer than in winter, the filters being apparently less efficient. The writer believes that they are only apparently less efficient, and not really so, the explanation being that some bacteria always grow in the under‑drains and lower parts of the filter, and are washed away by the effluent. The average number of bacteria in summer in the settled water is 160 per cu. cm. and in the filtered water 18. These are very low numbers. It is the writer's view that nearly all of these 18 represent under‑drain bacteria, and practically bear no relation to those in the applied water, and, if this view is correct, the number of bacteria actually passing through the various processes is at all times less than the figures indicate. In the warmer part of the year the difference is a wide one, and the hygienic efficiency of the process is much greater than is indicated by the gross numbers of bacteria.

The reduction of the typhoid death rate has not been as great with the change in water supply as was the case at Lawrence, Albany, and other cities, apparently because the Potomac water before it was filtered was not the cause of a large part of the typhoid fever.

The sewage pollution of the Potomac is much less than that of the Merrimac and the Hudson, and it is perhaps not surprising that this relatively small amount of pollution was less potent in causing typhoid fever than the greater pollution of rivers draining more densely populated areas.

The method of replacing the washed sand hydraulically seems to have worked better than could have been reasonably anticipated, and the writer believes that this was due, in part, to the excellent method of manipulation described in the paper. It is his feeling, however, that part of the success is attributable to the very low uniformity coefficient of the sand. In other words, the sand grains are nearly all of the same size, due to the character of the stock from which the filter sand was prepared; and, therefore, there is much less opportunity for separation of the sand according to grain sizes than there would be with the filter sand which has been available in most other cases. Filter sand with a uniformity coefficient as low as that obtained at Washington has been rarely available for the construction of sand filters, and while the method of hydraulic return should certainly be considered, it will not be safe to assume that equally favorable results may be obtained with it with sands of high uniformity coefficients until actual favorable experience is obtained.

The writer believes that in calculating the cost of the water used in the plant itself the price chosen by the author, covering only the actual operating expenses of pumping and filtering, is too low. The capacity of the whole Washington Aqueduct system is reduced by whatever quantity is used in this way, and, in calculating the cost of sand handling, the value of the water used should be calculated on a basis which will cover the whole cost of the water, including all capital charges, depreciation, operating expenses, and all costs of every description. On this basis the water used in the sand‑handling operations would probably be worth five or more times the sum mentioned by the author.

The cost of operation of the plant has come within the estimates made in advance, and has certainly been most reasonable. The cost of filter operations has averaged only about 50 cents per million gallons, and is so low that it is obvious that the savings which may be made by introducing further labor‑saving appliances would be relatively small. It will be remembered that ten or fifteen years ago the cost of operating such filters under American conditions was commonly from $2 to $5 per million gallons.

The experiments represented by Tables 17 to 19, inclusive, serve to show that preliminary filtration, or multiple filtration, or any system of mechanical separation is incapable of entirely removing the finer clay particles which cause the residual turbidity in the effluent. They also show that this turbidity may be easily and certainly removed by the application of coagulant to the raw water during the occasional periods when its character is such as to require it.

These general propositions were understood by those responsible for the original design of the plant, as is shown by the author's quotations. These experiments, however, were necessary in order to demonstrate and bring home the conditions to those who thought differently, and who believed that full purification could be obtained by filtration alone, or by double filtration, without recourse to the occasional use of coagulant.

The experiments briefly summarized in Table 20 are of the greatest interest and importance. Six small filters, otherwise alike and like the large filters, all received the same raw water and were operated at different rates to determine the effect of rate on efficiency.

That the experimental results from the filter operating at the same rate as the large filters were on the whole somewhat inferior to those from the large filters for approximately the same period, may be attributed to the fact that the experimental filter was new while the large filters had been in service for some time and had thereby gained in efficiency. The greatest difference was in the coli results in Table 20, where it is shown that 24% of the 10‑cu. cm. effluent samples from the experimental filter contained coli, in comparison with only from 1 to 3% of such samples from the main filters.

The results from the experimental filter operating at a rate of 1,000,000 gal. per acre daily may fairly be excluded, as the effluent probably contained more under‑drain bacteria in proportion than filters operated at higher rates. The number of bacteria in the filter operating at a 3,000,000‑gal. rate were 1.7% of those in the applied water; for the filter operating twice as fast, the percentage was 2.4; and, for the one operating more than ten times as fast, was only 3.0; thus indicating a surprisingly small increase in the number of bacteria with increase in rate.

Further and more detailed study by the writer of the unpublished individual results, briefly summarized in Table 20, confirms the substantial accuracy of the comparison based on the average figures as stated in that table.

It must be kept in mind, in considering these results, that the number of bacteria in each case is made up of two parts, namely, those coming through the filter—which number is presumably greater as the rate is greater—and, second, those coming from harmless growths in the under‑drains and lower parts of the filter—the numbers of which per cubic centimeter are presumably less as the rate is greater—and these two parts, varying in opposite directions, may balance each other, as they seem to do in this case, through a considerable range. It may thus be that the number of bacteria really passing the filter varies much more with the rate than is indicated by the gross results.

It is also of interest to note that the sand filter (called a preliminary filter) in Table 18, filled with the same kind of sand, when operated at an average rate of 50,000,000 gal. per acre daily for a year, allowed 18% of the applied bacteria to pass, in comparison with 3% found in Filter No. 6 of Table 20, operated at an average rate of 38,000,000 gal. per acre daily.

There was one point of difference in the manipulation: the preliminary filter was washed by a reversed current of water, as mechanical filters are washed, while Filter No. 6 was cleaned by scraping off the surface layer, as is usual with sand filters. Whether the great difference in bacterial results with a relatively small difference in rate is to be attributed to this difference in manipulation the writer will not undertake to state.

If the experimental results of Table 20 indicate correctly the conditions which obtain in filtering Potomac water, then increasing the rate of filtration so as to double it, or more than double it, would make but little difference in the quality of the effluent as measured by the usual bacterial methods. If the increase in rate were accompanied by the preliminary filtration of the water, then, presumably, there would be little change in the quality of the effluent, and the maintenance of excellent results might be incorrectly attributed to the influence of the preliminary filter.

It would also seem that the apparatus which is sometimes used for determining and controlling the rate with more than the ordinary degree of precision is hardly justified by such experimental results as those presented by the author.

In contrast to these results may be mentioned those obtained by Mr. H. W. Clark,[1] for experimental filters operated with Merrimac River water, at rates ranging from 3,000,000 to 16,000,000 gal. per acre daily. The results are the average of nearly two years of experimental work, the period having been nearly coincident with that covered by the author's experiments, and of many hundreds of bacterial analyses of each effluent, and form, with the author's experiments, the most thorough‑going studies of the effect of rate on efficiency that have come to the writer's attention.

Mr. Clark's results are given in Table 22.

1 Journal, New England Water-Works Association, Vol. 24, p. 589.

TABLE 22.

Effective size of sand.

Filter No.

Rate in gallons acre daily.

Bacteria per cubic centimeter in

Bacteria efficiency.

B. Coli in 1 cu. cm. (percentage of positive tests).

0.28

A

3,000,000

48

99.1

5.0

0.25

B

5,000,000

85

98.4

24.0

0.22

C

7,500,000

105

98.1

25.0

0.22

D

10,000,000

110

98.0

25.0

0.22

E

16,000,000

280

95.0

38.0

It will be seen that the number of bacteria passing increases rapidly with the rate, and whether the total number of bacteria is considered or the B. coli results, the number passing is approximately in proportion to the rate. In other words, doubling the rate substantially doubles the number of bacteria in the effluent.

This is entirely in harmony with all the Lawrence experimental results extending over a period of 20 years. There have been occasional apparent exceptions, but, on the whole, experience with Merrimac River water has uniformly been that more bacteria pass as the rates are higher.

The theory sometimes advanced, that the efficiency of filtration is controlled to a certain extent by gelatinous films, and that, as far as thus controlled, is less dependent on rate, would not seem to be borne out by these results. The Merrimac River water, carrying large amounts of organic matter, would certainly seem better adapted to the formation of such films than the clay‑bearing Potomac water, comparatively free from organic matter; but it is the Potomac water which seems to show the least influence of rate on efficiency.

The experiments show that turbidity passes more freely at the higher rates with the Potomac water, as has also been found to be the case with other clay‑bearing waters.

In the last lines of Table 20 are given cost per million gallons for filtering at various rates. There is no discussion of these figures, and as they differ considerably from those which the writer has been accustomed to use, the calculation in Table 23, made three years ago for a particular case, may be of interest.

TABLE 23—RELATIVE COST OF FILTERING AT DIFFERENT RATES.

Nominal rate, in millions of gallons per acre daily:

3

5

10

20

Percentage which average yield is of nominal rate

85

80

75

65

Average output per acre, in millions of gallons per day

2.55

4.00

7.5

13.0

Cost of that part of filters per acre dependent on rate

$12,000

$20,000

$40,000

$80,000

Cost of that part of filters per acre not dependent on rate

50,000

50,000

50,000

50,000

Total cost of filters per acre

60,000

70,000

90,000

130,000

Cost per million gallons of capacity

20,600

14,000

9,000

6,500

Cost per million gallons of average daily output

24,400

17,500

12,000

10,000

Capital charges and depreciation at 6% on cost per million gallons

4.00

2.87

1.97

1.64

Operating expenses, the same at all rates

1.00

1.00

1.00

1.00

Total cost of filtering, excluding pumping, storage, and all auxiliaries

5.00

3.87

2.97

2.64

Relative cost

1.29

1.00

0.77

0.68

When the costs of pumping, pure‑water reservoirs usually necessary, etc., are taken into account (which add equally to the cost at all rates), the cost of filtering will vary less with the rate than is indicated.

The effect of rate on cost, as calculated in Table 23, and also the percentages of the bacteria of the raw water found in the effluents by the author and by Mr. Clark, are shown on Figure 10.

Considering all these results together, and also all the other evidence known to the writer bearing on this point, it seems clear that filters are not as sensitive to changes in rate, within reasonable limits, as has been frequently assumed; but, on the other hand, there is usually a substantial increase in the percentage of bacteria passing through a filter with increased rate.

Filters furnish relative, not absolute, protection against infectious matter in the raw water. The higher the bacterial efficiency, the more complete is this relative protection.

The cost of filtering does not decrease in inverse ratio to the rate, but at a much slower rate. This is especially true with rates of more than 5,000,000 or 6,000,000 gal. per acre daily.

In general, a rate of filtration may rationally be selected at which the value of the possible danger resulting from an increase in rate is equal to the saving that may be made in cost by its use. This point must be a matter of individual judgment. The tendency of the last few years has been to use higher rates, or, in other words, to cheapen the process and to tolerate a larger proportion of bacteria in the effluent. The use of auxiliary processes has been favorable to this, especially the use of chloride of lime, in connection with either the raw water or the effluent.

FIGURE 10—RATE MILLION GALLONS PER ACRE DAILY.

By the judicious use of this substance, efficiency may be maintained while using higher rates than would otherwise have been desirable.

The writer believes that there will be many cases where the added risk of using too high a rate is not worth the relatively small saving in cost that accompanies it.

GEORGE A. JOHNSON, ASSOC. M. AM. SOC. C. E.—This paper contains information of an exceedingly interesting nature. There is comparatively little difficulty in obtaining accurate figures on the cost of construction of water purification works, but, with costs of operation of such works, it is different. The data available in published reports and papers are usually more or less fragmentary, and unexplained local conditions with reference to the character of the raw water, the cost of labor and supplies, and methods of apportioning these costs, introduce variables so wide as frequently to render the published figures almost useless for purposes of comparison.

Mr. Hardy's paper is noteworthy in that it presents certain relatively new features of slow sand filter operation which have been only lightly touched on in water purification literature up to the present time. These refer particularly to means whereby a filter may be continued in service without removing a portion of the surface layer of the filter surface itself when the available head has become exhausted, and to methods whereby washed sand may be expeditiously and more economically restored to the filter than has been the case hitherto.

Sand handling is the most important item of expense in the operation of a slow sand filter. Quite recently a charge of $1.50 per cu. yd. for sand scraping, transportation to sand washers, washing, and restoring to the filter, was not considered exorbitant, but the improved methods developed during recent years at Washington, Philadelphia, Albany, and more recently at Pittsburg (at all of which places hydraulic ejection plays an important part), have shown the feasibility of reducing this figure by nearly, if not quite, two‑thirds.

The practice observed at Washington of raking over the surface of the sand layer when the available head becomes exhausted, in order to avoid the cost and loss of time necessitated by shutting down the filter and scraping off the surface layer, is unquestionably one of the most striking advances in slow sand filter operation in recent years. In rapid sand filter operation, to prolong the period of service between washings, agitation of the filter surface has been used to advantage for many years. The full value of surface raking may not be generally appreciated, but the results which have followed a trial of this procedure at Washington, Philadelphia, and Pittsburg have shown that the output of filtered water between scrapings may be doubled or trebled thereby, with no injury to the filter itself or to the quality of the filtered water. The cost of raking over the surface of a 1‑acre slow sand filter unit is less than $10 at all the above‑mentioned places, which fact in itself shows the great saving in money and time effected by periodically substituting surface raking for scraping. Under ordinary conditions it has been found that a filter can be raked to advantage at least twice between scrapings.

In the case of filters thus raked, a deeper penetration of suspended matter into the sand layer is inevitable, but at Pittsburg, as at Washington, such penetration does not extend more than about 2 in. below the filter surface. When the filter is finally scraped, a deeper layer is removed, of course, but it is clearly more economical to remove a deep layer at one operation than to remove separately several thinner layers of an equal total thickness.

The lost‑time element is an important one, and at Washington this was the main reason for trying surface raking. It became necessary to increase the output of the filters, and the ordinary scraping consumed so much time that the sand‑handling force was increased, working day and night. The raking expedient introduced at this time overcame this, and Mr. Hardy states that it is still followed when the work is at all pressing. The speaker has found at Pittsburg, as Mr. Hardy has found at Washington, that raking is nearly if not quite as effective as scraping in restoring the filter capacity.

Eleven years ago the speaker was connected with the preliminary investigations into the best methods of purifying the Potomac River water for Washington. It then appeared that while for the greater part of the time during an average year the Potomac River could be classed among the clear waters of the East, there were periods when excessive turbidity made it necessary to consider carefully methods of preparatory treatment before this water could be filtered effectively and economically. As Mr. Hardy has said, considerable prejudice existed against the use of a coagulating chemical, and the expedient was therefore adopted of giving the water a long period of sedimentation in order to remove enough of the suspended matter to allow the clarified water to be treated on slow sand filters. The expert commission, consisting of Messrs. Hering, Fuller, and Hazen, recommended the occasional use of a coagulating chemical, but this recommendation was not carried out.

The Potomac River is somewhat peculiar, in that the turbidity of its waters, as shown by the results presented in Mr. Hardy's paper, ranges from 3,000 to practically nothing. The bacterial content also varies widely, and Mr. Hardy's tables show this variation to be from 76,000 to 325 per cu. cm. Such a water as this requires particularly careful preparatory treatment. The Dalecarlia Reservoir has a capacity of something like 2 days' storage, the Georgetown Reservoir the same, and the McMillan Park Reservoir nearly 3 days, making a total sedimentation of more than 7 days. Without the use of a coagulant, it is significant that during a period of five years, even with 7 days' sedimentation, the average maximum turbidity of the water delivered to the filters was 106 parts per million, and the maximum average turbidity in one month was 250 parts per million. The water filtration engineer can readily understand that waters as turbid as this cannot be treated economically and efficiently in slow sand filters. It would appear that coagulating works might advantageously have been installed at the entrance to the Dalecarlia Reservoir. If this had been done, and coagulant had been added to the water at times when it was excessively turbid, a considerably shorter period of subsequent sedimentation than now exists would in all probability have rendered the water at all times amenable to efficient and economical slow sand filter treatment.

The prejudice in Washington against the use of coagulants has also manifested itself in other localities, but the results which have been obtained during the past twenty years from rapid sand filters and from slow sand filters, treating waters previously coagulated with salts of iron or alumina, have shown how thoroughly unreasonable were these objections. In this connection it is interesting to note that there are in the United States more than 350 rapid sand filter plants, and that nearly 12% of the urban population of Continental United States is being supplied with water filtered through rapid sand filters, in connection with all of which a coagulating chemical is used in the preparatory treatment.

TABLE 24—TYPHOID FEVER DEATH RATES IN CITIES OF THE UNITED STATES WITH POPULATIONS IN 1910 OF 100,000, OR MORE.

Statistics gathered by correspondence and from Reports of the Bureau of the Census, Department of Commerce and Labor, Mortality Statistics.

NOTE.—

Statistics from Birmingham, Ala., Dayton, Ohio, Fall River, Mass., Louisville, Ky., Memphis, Tenn., Oakland, Cal., and Providence, R. I., are not included, as they are incomplete.

City.

TYPHOID FEVER DEATH RATE PER 100,000 POPULATION.

1906

1907

1908

1909

1910

Average for six years, 1900-05, inclusive.

Average for five years, 1906-10, inclusive.

Average for 11 years, 1900-11, inclusive.

Albany, N. Y.

20

20

11

19

15

25

17

21

Atlanta, Ga.

50

64

47

44

43

65

50

58

Baltimore, Md.

34

41

31

23

41

36

34

35

Boston, Mass.

22

10

26

14

11

23

16

20

Bridgeport, Conn.

10

13

13

13

9

15

12

14

Buffalo, N. Y.

24

29

21

23

20

29

23

26

Cambridge, Mass.

18

10

10

9

12

18

12

15

Chicago, Ill.

18

18

15

12

14

27

16

22

Cincinnati, Ohio

71

46

19

13

6

54

31

44

Cleveland, Ohio

20

19

13

12

19

51

17

36

Columbus, Ohio

45

38

110

17

13

61

45

54

Denver, Colo.

68

67

58

24

30

37

49

42

Detroit, Mich.

22

28

22

19

16

17

22

19

Grand Rapids, Mich.

39

30

30

17

27

34

28

31

Indianapolis, Ind.

39

29

26

22

31

76

30

55

Jersey City, N. J.

20

14

10

8

10

19

12

16

Kansas City, Mo.

38

40

35

23

38

48

35

42

Los Angeles, Cal.

18

23

19

18

12

35

18

27

Lowell, Mass.

7

9

24

11

21

19

14

17

Milwaukee, Wis.

31

26

17

21

45

19

28

23

Minneapolis, Minn.

33

26

18

20

58

38

29

34

Nashville, Tenn.

66

85

62

53

48

54

58

56

Newark, N. J.

18

24

12

11

13

17

16

17

New Haven, Conn.

54

30

34

20

17

44

31

38

New York, N. Y.

15

17

12

12

12

19

14

17

New Orleans, La.

30

56

31

25

28

40

34

37

Omaha, Nebr.

28

24

22

31

75

20

36

27

Paterson, N. J.

4

11

10

5

7

25

7

17

Philadelphia, Pa.

74

60

36

22

17

47

42

45

Pittsburg, Pa.

141

135

53[1]

13[1]

12[1]

132

71

104

Richmond, Va.

44

41

50

24

22

66

36

53

Rochester, N. Y.

17

16

12

9

13

15

13

14

St Louis, Mo.

18

16

15

15

14

33

16

25

St Paul, Minn.

21

17

12

20

20

14

18

16

San Francisco, Cal.

...

57

27

17

15

20

29

24

Scranton, Pa.

11

76

11

11

14

18

35

26

Syracuse, N. Y.

10

16

15

12

30

14

17

15

Toledo, Ohio

45

36

40

31

32

36

37

36

Worcester, Mass.

12

14

10

8

16

17

12

15

Washington, D. C.

52

36

39

33

23

59

37

49

1 Filtered water section. Allegheny District not included.

Attention has repeatedly been called to the fact that the relatively high typhoid death rate in Washington, since the filter plant was installed, was a possible indication that the filters were inefficient. It is true that there has not been the marked reduction in the typhoid death rate in Washington, following the installation of the water filtration works, that has been observed in other cities in America. For the six years prior to the date on which filtered water was supplied to the citizens of Washington, the average typhoid fever death rate was 59 per 100,000 population, as against 37 per 100,000 for the five years following, a reduction of 37 per cent. At Albany, N. Y., where the first modern slow sand filter was built in 1899, the typhoid death rate has been reduced by 75 per cent. At Cincinnati, Ohio, the average death rate from typhoid ranged around 50 per 100,000 for years, but since the installation of the filtration plant it has been reduced to a point which places that city, with respect to freedom from typhoid fever, at the head of all the large cities in America; in 1910 the death rate from typhoid in Cincinnati was 6 per 100,000. Similarly, at Columbus, Ohio, where the typhoid death rate before the installation of the filtration plant in 1906 was even higher than at Cincinnati, it was reduced to less than 13 per 100,000 in 1910, whereas, for the previous five years, it was 61 per 100,000. Philadelphia, before the installation of the filtration works, had a typhoid death rate of 60 or more per 100,000, and in 1910 the death rate from this disease was 17. Pittsburg, at least that part of it now supplied with filtered water, for years had a typhoid death rate of more than 130 per 100,000, but the present rate is about 12 per 100,000.

TABLE 25—AVERAGE MONTHLY RESULTS FOR THE PERIOD, 1905-1910.

Reservoirs.

Period of sedimentation in days.

Turbidity in parts per million.

Bacteria per cubic centimeter.

PERCENTAGE REMOVED

Turbidy

Bacteria

River

...

106

6,400

...

...

Dalecarlia

2.2

50

5,000

53

22

Georgetown

2.2

38

3,400

24

32

McMillan

2.8

26

2,000

31

41

Totals and averages

7.2

...

...

75

69

While it may perhaps seem unreasonable to single out Washington as a particular sufferer in this respect, it is highly probable that a large share of the typhoid is still caused by secondary infection, flies, impure milk, and private and public wells. The speaker remembers distinctly that ten years ago, when he made an investigation into the purity of the water of about 100 public wells in that city, a large number of them showed unmistakable evidence of being polluted with sewagic matter. Conclusive evidence would be secured to dispel any doubt as to the sanitary quality of the filtered product if hypochlorite of lime were added to the filtered water throughout one year or throughout the typhoid months. It seems strange to the speaker, that for this, if for no other reason, this safe and non‑injurious germicide has not as yet been used at Washington, in view of the fact that at the present time it is being used continuously or intermittently in the treatment of the water supplies of scores of the most important cities of this country, among which may be mentioned New York, Philadelphia, Cincinnati, Pittsburg, St. Louis, and Minneapolis.

MORRIS KNOWLES, M. AM. SOC. C. E. (by letter).—This description of the operation of the Washington Filtration Works is timely and of great interest. It is ten years since the writer, in collaboration with Charles Gilman Hyde, M. AM. SOC. C. E., presented a similar record for the Lawrence, Mass., filter. That paper was the first complete, detailed, and continuous history of the actions and results obtained for a long period of time with such a purification works. [1] Since then, the art of filtration has advanced in many ways, particularly in regard to the methods of cleaning slow sand filters and in the accompanying processes. It is well, therefore, again to take account of stock and see really what progress has been made. Therefore, Mr. Hardy's paper, giving a description of the operations of a system thoughtfully designed, after long consideration of the problem, and of operations carried on under efficient and economical administration, with thorough record of all details, should furnish a groundwork for the careful consideration of the question stated above.

The writer, using as a text some of the ideas given in the paper, but more particularly some of those becoming prevalent elsewhere, desires to discuss methods and costs of operation, especially in relation to sand handling; and to offer suggestions looking toward greater efficiency, as well as economy, in carrying out the standard and well‑tried methods.

Theory of Slow Sand Filtration.—First, what is the process of slow sand filtration? The answer to this question involves many factors, some of which are even yet but imperfectly understood. In the early history of filtration, at the time of the construction of the London filters, only the straining capacity of the sand bed, to remove gross particles, was known. Later, when the organic contents of water had become better understood, the chemical or oxidizing powers of the process were recognized as performing an important part. Finally, co‑existent with the discovery of the so‑called "germ theory of disease," a study of the bacterial action of filters resulted in the recognition of its importance. It is now universally thought that each of these factors performs its useful function; that the size of the sand, the amount of organic matter remaining on the surface of the bed, the turbidity of the applied water, and the bacterial content of the influent, are some of the things on which depends the determination of the relative importance of each.

1 Transactions, Am. Soc. C. E., Vol. XLVI, p. 258.

Engineers have been taught to believe, by the German school of thought, that the film of organic matter on the surface of the sand plays a very important role in filtration. This Schmutzdecke, as it is called, has been considered so precious that stress has been placed on treating it with great care. It was not to be wholly removed at the time of cleaning, and it was not to be walked on, or indented, or in any other way consolidated or destroyed. In fact, in some cases, the wasting of the first water after cleaning has been advocated, for the reason that not a sufficient amount of this organic film would be left on top of the sand to begin the filtration process properly immediately after the cleaning.

In late years, however, there has been a tendency to depart from this fundamental doctrine of slow sand filtration. Various new processes for cleaning the sand surface have been advocated; some of these partly destroy and others completely exterminate any semblance of a bacterial film on the sand bed. These ideas, advanced without any real and serious discussion of their intrinsic merits, or their effects on the public health, are not founded on long continuous records of such results as are necessary to establish confidence in the final value of any of these methods.

Rapid advances along this line have been made more recently, notwithstanding the occurrence of notable instances of trouble and the resultant need of complete repair of filtration beds. Because of the rough treatment of the sand surface, a penetration of organic matter and filth into the bed had taken place. This caused deep clogging, prevented the usual yield of water, and brought about a lessened bacterial efficiency, due to the attempt to force water through the filters, and because some organic matter and growths in the lower part of the bed had furnished a breeding place for more bacteria.

All these endeavors to reduce the work of cleaning have been commendable, because scraping and sand handling are the items of greatest expense in slow sand filter maintenance. Every one has been desirous of minimizing this cost. However, as the writer will endeavor to show, it seems that attempts along this line should be with the idea of doing more economically, as well as efficiently, the things which one knows will accomplish the proper results, rather than unwisely to adopt new methods which have not been tried for a long enough period to determine their effect on the public health.

Pittsburg Methods.—When first taking up the problem of design in Pittsburg, in 1902, the writer had presented to him for consideration and adoption, a suggestion that a certain method of cleaning sand filters, which would involve the washing of the sand in place (similar to that recently tried at the Jerome Park Experiment Station, New York City), would be advisable and economical. The decision then made has never been regretted. As this plan involved such a complete departure from those principles which had been well tried and had proven successful, it was believed that it was not safe to adopt such a method on the municipal filtration works, from which the people were to derive their drinking water. There is more to be considered in such a problem than mere economy of operation; the economy of human life, the effect on which requires far longer than a few months of trial to determine, is a much more important factor. Believing that no one should depart, until after a long period of conclusive experimentation, from that principle which is known to be safe (viz., to take off a small portion of the clogging surface), the writer studied to determine more efficient and economical methods of accomplishing this end.

A device for scraping the material, in just the same way as with shovels, but more efficiently and more exactly, was developed by George P. Baldwin, M. Am. Soc. C. E., under the general supervision of the Bureau of Filtration, of which the writer was in charge. However, on account of the unfortunate and earlier arrangement of other constructive matters, which the City's Legal Department advised could not be changed without upsetting the contract, the entrance doors to the original forty‑six filters were not built large enough to permit the rapid and economical transfer of these machines, and, as this act takes so large a proportion of the total time of operation, it has not been found economical to use them. The additional ten filters, recently constructed, with doors especially designed and large enough to pass the machines, have not yet been placed in operation. This is said to be on account of lack of funds and of employees. Therefore, there has been no opportunity to demonstrate what the scraping machines can do, under the conditions for which they were designed to operate. The restoring machine, a complementary device in mechanical operation, which simply replaces the sand in the same condition that it would be if wheeled back, but, with a small percentage of moisture, has accomplished its purpose well and economically. The sand is placed in the filters so that there is no further settling; with a smooth surface, needing no additional adjustment; with absolutely no possibility of sub‑surface clogging; and with the filters starting off exceedingly well in operative results.

Washington Methods.—In Washington, it is stated that the filters are still cleaned by the old‑fashioned method of scraping with shovels, throwing the sand into piles, and afterward removing it with a movable ejector. Between scrapings there is also an occasional mid‑period action of raking the unwatered sand surface, for the purpose of stirring up the dirty film. This process does not remove any of the clogging material from the bed, but it is said that no injurious effects are produced, and that it is economical. It is stated that the so‑called "Brooklyn method," of stirring the surface of the sand while the water is on the bed, has been tried at Washington, but with unsatisfactory results. It seems to have been advocated with greater fervor in some other places.

The method of dry raking does not remove the dirty material, but loosens up the pores of the surface, and through this porosity permits clogging to penetrate deeper into the filter. The method of raking with water on the bed, although it removes some of the organic dirt, also permits deeper penetration of the remainder. The latest devised system of washing the sand in place, by upward spraying with water, called the "Blaisdell method," thoroughly destroys the Schmutzdecke above, and, at the same time, must permit the formation of a subsidiary one below. In the Nichols method, the material removed by shovel scraping is conveyed by an ejector to a portable separator, where it receives a single washing; the dirty water overflows to the sewer, while the washed sand is discharged through a hose and deposited on the recently scraped surface. As the latter is partly impregnated with impurities, there is, by this process, a tendency toward sub‑surface clogging.

All these processes are marked and serious departures from the well‑tried method of cleaning slow sand filters, which, it is well known, will operate successfully to purify polluted river waters and make them safe to drink. In all there is the danger that they have not been sufficiently and carefully tried, under scientific observation, as to results and possible effects on the public health, to be sure that the bacterial efficiency can long continue to be satisfactory, with the application of specifically infected waters. It is dangerous, and may even jeopardize the safety of human lives, to experiment on water which is furnished for drinking purposes. There is also the added danger, well known from past experience, that in a few years (it may be more or less, depending on the extent and intensity of the new workings) the filters will need renovation, partly, if not wholly, throughout the entire bed. Thus, considering the total cost during a long term of years, the apparently cheaper method may become the most expensive.

There is also an interesting query in regard to the Washington method of replacing sand in the filters, and it is worthy of most careful thought and attention. If the process described can be carried on with success and safety, it will prove to be a long and progressive step in the methods of operation. The difficulty, however, is in determining from any short‑term runs whether such a process can be continued permanently without impairing the efficiency of the sand bed. Apparently good conditions may change, after a few years' trial, and be followed by unsafe results and predicaments. This replacing of sand with whatever dirt and detritus may travel with it in the carrying water is certainly not equivalent to the care with which it has been understood that sand should be deposited in filters. It is not comparable with the care with which it is placed, when wheeled from a washer, where dirty water overflows the lip, or where it is placed by a machine restorer in the filter, where the transporting water also overflows the weir and is carried to the sewer.

These cheap and rapid methods of doing the work, advanced in the interests of economy, and the idea that sand filters, receiving polluting waters, can operate at higher rates than those which we have demonstrated, and, therefore, have been led to believe are safe, is a speeding up of the whole organization and of operating conditions. It is like speeding up a machine for the purpose of getting a greater output, with the usual result that fast running means quicker wearing out of both man and machine. Quicker operations generally mean carelessness in doing the work, especially in municipal service. Carelessness is engendered by the thought that such work can be handled in a rough and rapid way, and, further, by the ridicule of all these things, which we have learned to be careful about, as old‑fogyish, out‑of‑fashion, and archaic. Carelessness in operation breeds contempt for the art. Some of the less efficient filter plants, from the standpoint of effect on the public health, may reflect such ill‑considered methods.

Economy with Efficiency in Operation.—It is particularly important to find out whether one can secure the desired economy, and, at the same time, the required efficiency. The development of efficiency in every line of human endeavor is receiving much attention at present, and not the least cause for this is the growing recognition of the demand for a high standard of service for the expense caused. One of the first requirements is to have well‑defined ideals and standards. When one knows how to secure a good and safe result, it is unwise to depart therefrom for a mere whim, or to secure a supposedly lessened expense, unless other facts be also determined favorably. The desire for economy must be tempered by good sense, which means that one should be willing to change a method only when the wisdom of such has been clearly demonstrated. Efficient service can only be secured by strict discipline, accompanied by fair dealing. This means employing no more men than are actually necessary, paying them on the basis of the standard of service and output produced, taking an interest in the working conditions, and providing for their health and welfare.

About twelve years ago, the writer made some investigations of the efficiency of laboring gangs in scraping and handling sand at filter beds, [1] and found that ten men was the most economical number to use in scraping the surface of the Lawrence filter, as then built and operated. This result was determined by numerous studies of the output per man per minute, with different numbers of men working under different conditions. This same sort of study has been carried further by adepts in the art, in reference to shop and similar management, but one fails to find corresponding development along this line in municipal organization except by a few of the scattered Bureaus of Municipal Research. These results, also, have related to a few of the more common and general factors, such as determining the cost per mile, or per square yard, of street cleaned, or per million gallons of water pumped.

1 Transactions, Am. Soc. C. E., Vol. XLVI, p. 291.

The cost of the management of water‑works, one of the largest factors of public enterprise, has never been investigated extensively and thoroughly. There is much possibility in planning for greater efficiency and in determining what can be accomplished under economical administration. Every one is aware of the multiplicity of men in municipal service. Some of these are entirely incompetent, others partly so; the recent appointees may be more efficient, but the majority of them gradually deteriorate under the subtle influence of the prevailing atmosphere, and each new incoming administration places more and more men on the work, without reason or necessity. All these tendencies have made the cost and maintenance of public work greater and greater, and, at the same time, have resulted in frequently and steadily decreasing the output and efficiency per employee.

The Washington situation, however, presents an admirable contrast to this, because of the methods of administration of the public works of the District of Columbia and their freedom from petty political influence. The limited number of employees has tended toward economy, and rendered this plant the envy of all who have desired to obtain good management. Its cost items have been looked on as a result long hoped for, but seldom obtained. It is to be regretted, therefore, that such an abrupt change in methods of removing clogging material and replacing sand has taken place without years of experimental trial on filters not furnishing drinking water to the public, and without an attempt, under such excellent conditions, to maintain the efficiency by a better labor output and by improved working and machine methods in the performance of the older and established order of doing things.

In preparing water for the use of the people, the realms of the unknown are so much larger than those which have been investigated and developed that there may be many undiscovered factors affecting the public health, and many ways in which it is dangerous to depart from well‑known and surely safe methods. Who can say that in some subtle and, at present, unknown manner, the failure in some places, where filtration is practiced, to reduce the death rate from typhoid fever may not be due to the introduction of radical departures from the older, slower, safer, and more efficient methods which have produced such excellent results, both in America and in Europe? Further, in cases where there has been a falling off in the typhoid death rate, the failure to secure an accompanying improvement in general health conditions, which follows so closely in communities supplied by water filtered in accordance with the more conservative principles, may be due to the introduction of some of these not thoroughly tried processes. Some day full information may be available as to the influence of these methods of plant operation on the health of the community. Until that time, is it not a much better policy to follow the principles which have been proven by many years of experience to produce safe results, and to make the foremost object the improvement of the methods of operation in accordance with these established truths?

There is opportunity for the upbuilding of greater efficiency in the conduct of employees and in securing the maximum output, by establishing more comfortable and healthful conditions than usually exist. The elimination of political influence from municipal service is also a task which challenges the people of to‑day, and the operating and managing engineer is in a position to perform an important part in accomplishing this end. The number of employees can be reduced to those actually needed, and the way opened for the employment of men who thoroughly understand the necessities of honesty and efficiency in the conduct of public affairs. It should be remembered that to design and construct well is only half the job; to operate economically and efficiently is even more of a problem than to build, and requires just as good talent, just as keen appreciation of the various problems, and is even more essential to public welfare. It seems to the writer that the logical development of the art of obtaining economy as well as efficiency should be along these lines, rather than to revolutionize methods, without having a long‑period test of their value, and at the same time allow political influences to control, to a large extent, the labor item.

Preliminary Treatment.—The decision as to the preliminary treatment of the Potomac River water before filtration is of interest, particularly because various other conclusions have been reached in different sections of the country. However, in the main, these decisions have been due to differences in the character of the waters, but it must be evident that they have sometimes been the result of ill‑considered action, or the desire to promote some special interest. The use of preliminary filters, which involves a large investment, is not always to be commended, particularly because at times of reasonably good water the removal of some of the organic matter is really injurious and lessens the effect of the final filters.

For a long time, the writer has believed that, where other things are equal, and where there is no important reason for double or preliminary filtration, long periods of storage, accompanied by the use of coagulant at times of severe and extreme muddiness, as planned at Washington, solves the problem in the most practical and economical way. It is true that the investment for a large storage basin may equal, or even exceed, that required for preliminary filters; but the influence of storage on the quality of raw water is never injurious, and, by ripening the condition of the water, may be greatly beneficial in the process of filtration.

The storage available in such a basin makes it possible to shut off the supply from the river during the worst conditions of the water. The duration of the most troublesome spells ordinarily does not exceed a few days, and it is usually possible to secure sufficient capacity in the basin to tide over these periods. Then again, long periods of storage, in addition to assisting in breaking up organic matter, permit the dying out of bacteria, particularly many of the pathogenic kind, and, therefore, the water is rendered much safer from this standpoint. In other words, there is additional insurance in long storage against the faulty and careless operation of incompetent filter employees. The addition of coagulant, especially the fact that only a very small investment of capital is required for the necessary apparatus for dosing the water, and that the cost of the coagulating materials has to be met only when used, seems to give the process, in a most satisfactory manner, the requirement for economical management and thoroughness in preparing the water for final filtration.

Parking Public Works.—It is disappointing that the author has not mentioned some of the steps contemplated in reference to the landscape treatment of the Washington filtration area. Probably every one has been impressed by the barren aspect of the works as they are approached, and as one looks over them. Recently, however, it is stated that some steps have been taken to lay out the grounds, treat the surface in an attractive manner, and make a park of the area. The writer has a firm opinion that when an investment is made for public works, it costs but little in addition to construct buildings along appropriate architectural lines, to treat the grounds in a pleasing manner, and to make the entire works a credit to the municipality from an artistic standpoint. When treated on broad lines, such areas become public parks, and afford open breathing places for the residents, and, if near centers of population, may well be equipped with playground facilities for the children. When thus developed they should have care, that the planting and equipment should not deteriorate and the last state become worse than the first.

The influence which these ever‑present examples of attractiveness have on the community is becoming better recognized by students of social progress, and there seems to be no doubt that spending money on such features is not only desirable from the artistic standpoint, but is justified on practical grounds as well. It is cheaper than to create parks, when necessity and demand can no longer be resisted, by buying property and occasionally tearing down buildings and constructing de novo. That this work is now being done in Washington, even after construction, is certainly a recognition of the advisability of original efforts in this direction.

George C. Whipple, M. Am. Soc. C. E. (by letter).—Mr. Hardy's paper is an excellent presentation of the results of the operation of the Washington water filtration plant from the time of its construction in 1905 until June, 1910. Papers of this character are altogether too infrequent, and the actual results from the filters now in use are not readily accessible in detailed form. Yet it is only by studying the results obtained by filters in actual use that improvements can be made and the art advanced.

Among the many important facts brought out by Mr. Hardy, only a few can be selected for discussion. One of these is the operation of filters under winter conditions. It is well known that the efficiency of sedimentation basins and filters is lower during winter than at other times, yet it is just at this season of the year that there is the greatest danger of typhoid fever and similar water‑borne diseases being transmitted by water. Most of the great typhoid epidemics have occurred during cold weather, and the very use of the term "winter cholera" is of significance. Apparently, typhoid bacilli and similar bacteria are capable of living and retaining their vitality longest during that season of the year. Just why this is so, bacteriologists have not satisfactorily explained. Doubtless many factors are involved. Because of the increased viscosity of the water, sedimentation takes place less readily at lower temperatures, and inasmuch as sand filtration is partly dependent on sedimentation, the efficiency tends to fall off in cold weather. During winter some of the external destroying agencies are less potent, such as the sterilizing effect of sunlight, and the presence and activity of some of the larger forms of microscopic organisms which prey on the bacteria. Another factor may be the greater amount of dissolved oxygen normally present in water during cold weather, as experiments have shown that dissolved oxygen favors longevity.

Still another reason for the larger numbers of bacteria that pass through a water filter during cold weather may be the effect that the low temperature has on the size of the bacteria themselves. A few experiments made recently by the writer appear to indicate that at low temperatures the gelatinous membrane which surrounds the bacterial cells tends to become somewhat contracted, thus decreasing the apparent size of the bacteria as seen under the microscope. Either this contraction occurs, or the cells themselves are smaller when they develop in the cold. It is possible also that low temperature affects the flagella of the organisms in the same way. It is not unreasonable to suppose that the effect of low temperature is to form what may be, in effect, a protective coating around the cells, which tends to make them smaller, less sticky, and less subject to outside influences. This would tend to make them pass through a filter more readily. In line with this idea also is the well‑known fact that disinfection is less efficient in cold water than in warm water.

Another way of viewing the matter is that cold retards the growth of bacteria on the filter, thus reducing the effect of the Schmutzdecke. Still another view of the greater danger from bacterial contamination in winter is the theory that cold prolongs the life of the bacteria by merely preventing them from living through their life cycle and reaching natural old age and death as rapidly as in warm weather.

Another topic in Mr. Hardy's paper which has interested the writer is that of preliminary filters. The experiments described at length indicate clearly that such devices would prove of little or no benefit under the conditions existing in Washington, and that when the river contains considerable amounts of suspended clay nothing less than chemical coagulation will suffice to treat the water so that the effluent will be perfectly clear. Preliminary filters have been used for a number of years at various places and with varying success. In few instances have they been operated for a sufficient length of time or been studied with sufficient care to determine fully their economy and efficiency as compared with other possible methods of preliminary treatment.

Among other experiments on this matter are those made at Albany, N. Y., and published by Wallace Greenalch, Assoc. M. Am. Soc. C. E., in the Fifty‑ninth Annual Report of the Bureau of Water for the year ending September 30th, 1909. The Hudson River water used at Albany is quite different in character from the Potomac River water used at Washington, as it is less turbid and contains rather more organic matter. The results obtained in these experiments showed that during the summer the number of bacteria in the effluent from the experimental sand filter used in connection with a preliminary filter did not differ widely from the number found in the effluent of the city filter where there was no other preliminary treatment than sedimentation. In the winter, however, the numbers of bacteria did not increase in the effluent from the experimental filter as they did in the effluent from the city filter. This is shown by Table 26, taken from the report mentioned.

Apparently, therefore, at Albany the benefits of the preliminary filter, as far as bacterial efficiency is concerned, would be confined to a short period of three or four months in each year. Under such circumstances it may well be questioned whether the advantages of preliminary filtration justify its cost.

TABLE 26—RESULTS OF EXPERIMENTS WITH PRELIMINARY FILTER AT ALBANY, N. Y.

Month

Bacteria in raw water.

Bacteria in preliminary filter effluent.

Bacteria in effluent from experimental sand filter.

Bacteria in effluent from city filter.

1906.

March

133,480

36,000

151

706

April

77,420

4,810

72

155

May

15,800

2,250

48

37

June

4,520

358

38

34

July

2,090

163

25

22

August

2,740

121

36

22

September

8,280

445

20

24

October

38,350

4,235

67

227

November

67,910

15,570

337

341

December

645,500

25,440

144

2,783

1907.

January

127,560

4,660

48

443

February

28,000

1,800

13

116

On the diagram, Figure 11, will be found various data taken from the published records of the Albany filter, from 1899 to 1909. These data include: The numbers of bacteria before and after filtration; the percentage of bacteria remaining in the effluent; the average quantity of water filtered, in millions of gallons per day; the quantities of water filtered between scrapings; the turbidity of the raw water; the cost of filtration, including capital charges and cost of operation; and the typhoid death rates of the city per month. Several points are brought out conspicuously by this diagram. One is the uniformly low death rate from typhoid throughout the entire period. The filter was operated from 1899 until the fall of 1907 with raw water taken from what is known as the "Back Channel." Since then it has been taken from a new intake which extends into the Hudson River itself. Until the fall of 1908 the preliminary treatment consisted merely of sedimentation, but since then the water has received an additional preliminary treatment in mechanical filters operated without coagulant, along the lines of the experiments just mentioned. During this time the average rate of filtration of the sand filter has not changed materially, although it is said that the maximum rate has been increased since the preliminary filters were put in service. The study of the bacteriological analyses shows that the best results were obtained during 1902, 1903, and 1904. Since then the numbers of bacteria in both the raw and filtered water have increased. This was especially noticeable during the winters of 1907 and 1908 when the water was taken from the new intake. It will be interesting to compare the results after the preliminary filters have been operated for a long period to ascertain their normal effect on efficiency and on the increased yield.

FIGURE 11—FILTERS AT ALBANY, N. Y. RESULTS OF OPERATION. 1899‑1909. COMPILED FROM DATA IN ANNUAL REPORTS.

Another fact to be drawn from the plotted Albany data is the increase in the cost of filtration, both in capital charges and in operation. From 1899 until 1906 the cost of operation, including the cost of low‑lift pumping, was approximately $5 per million gallons of water filtered; and the total cost of filtration, including capital charges, was about $10 per million gallons. During the year ending September 30th, 1909, the cost of operation had increased to $7.63 per million gallons, and the total cost of filtration to $15.92 per million gallons, or approximately 50% in three years.

TABLE 27—RESULTS OF BACTERIOLOGICAL ANALYSES OF SAMPLES OF WATER AT PEEKSKILL, N. Y., BEFORE AND AFTER FILTRATION.

BACTERIA PER CUBIC CENTIMETER.

Date.

Raw water.

Clear reservoir.

Effluent No. 1.

Effluent No. 2.

Effluent No. 3.

Effluent No. 4.

Tap in city.

1909.

December 29th

190

100

...

...

...

...

...

1910.

February 15th

135

10

10

30

20

...

265

March 31st

225

50

25

45

60

...

35

May 18th

300

29

22

26

35

43

36

July 6th

300

44

9

3

41

10

31

August 16th

60

5

0

4

1

13

15

October 3d

550

14

12

14

38

...

...

November 21st

315

22

26

17

6

...

...

1911.

January 25th

415

7

8

4

6

...

7

Average

277

30

14

16

26

22

65

TABLE 27—(Continued.)

FILTER SAND TESTS FOR B. Coli.

Quantity of water tested.

PERCENTAGE OF SAMPLES CONTAINING B. Coli.

Raw.

Filtered.

0.1 cu. cm.

0

0

1.0 cu. cm.

20

0

10.0 cu. cm.

40

0

As a matter of record, the results of a series of analyses made at Peekskill, N. Y., during 1910 are presented in Table 27. A sand filter was constructed for the water supply of this city in 1909, and put in operation in December. The filter has a capacity of 4,000,000 gal. per day. The supply is taken from Peekskill Creek, and the water receives about one week's nominal storage before flowing to the filters. An aerator is used before filtration during the summer, when algae are likely to develop in the reservoir. The filter was installed after an epidemic of typhoid which was apparently caused by an infection of the water supply. Normally, the water has been little contaminated, but the supply is subject to accidental contamination at any time, among other possible sources of infection being the camps of workmen now engaged in constructing the Catskill Aqueduct for New York City.

TABLE 28—AVERAGE RESULTS OF CHEMICAL ANALYSIS AT PEEKSKILL, N. Y., MADE AT INTERVALS OF SIX WEEKS DURING 1910.

Parts per Million.

Parts per Million.

Raw water.

Filtered water.

Raw water.

Filtered water.

Turbidity

2.000

0.000

Total residue

70.00

76.00

Color

25.000

20.000

Loss on ignition

19.00

17.00

Nitrogen as albuminoid amonia

0.112

0.076

Fixed residue

50.00

59.00

Nitrogen as free ammonia

0.024

0.006

Iron

0.17

0.13

Nitrogen as nitrites

0.001

0.001

Total hardness

38.70

45.10

Nitrogen as nitrates

0.060

0.060

Alkalinity

33.90

42.60

Incrustants

4.600

4.500

Chlorine

2.60

2.70

F. F. LONGLEY, ASSOC. M. AM. SOC. C. E. (by letter).—In this paper the author has presented a mass of data which will be welcomed by engineers engaged in water purification work, because complete operating records form a substantial basis for improvement in the art, and are often the inspiration for interesting discussions and the exchange of experiences of different observers whose views are mutually appreciated.

Recent tendencies in filtration engineering have been largely in the direction of reducing the cost of operation. A comparison of the operating costs of the earlier American plants of about a decade ago, with those here presented of the Washington plant, is very gratifying to those who have been intimately connected with the latter work. Through perfection in design and reasonable care in operation, the cost of filter cleaning, which is a very considerable part of the total cost, has been reduced to an unusually low figure, without any sacrifice in efficiency, and in the interests of the public health.

Table 14 shows that, from the first year, there has been a progressive increase in the total cost of operation per million gallons filtered, but this has not meant an increase in the annual total expenditure. The largest percentage of increase in any item has been in "Care of Grounds and Parking," and covers much‑desired landscape improvements. Aside from this, the principal factor affecting the table of costs has been the reduction in water consumption in the District of Columbia. Nothing pertaining to this reduction has produced any corresponding reduction in the force required for the maintenance and operation of the filtration plant, office and laboratory, and pumping station, though probably there has been some reduction in filter cleaning. Obviously, then, the total cost per million gallons would increase.

This decrease in consumption has been brought about by the elimination of waste in the distribution system, which is not in the same department as the filtration plant, but with regard to which a word may not be amiss in connection with this discussion.

The Washington Aqueduct was built half a century ago on lines which at that time were considered extraordinarily generous. Until recently, therefore, there has been no occasion for concern over the high rate of consumption. During recent years, however, the use and waste of water have increased, reaching a climax under unusual conditions in the winter of 1904‑05. The maximum capacity of the aqueduct system is about 90,000,000 gal. The maximum daily consumption at the time mentioned arose almost to 100,000,000 gal., with the result that, before normal conditions were restored, the reservoirs of the system were almost depleted.

This had a beneficial effect, as provision was made for an active campaign for reducing the waste of water, which was known to be very large. These investigations, using the pitometer, were begun in July, 1906, and have been pursued continuously since that time, with most excellent results. Up to January, 1909, leaks aggregating about 12,000,000 gal. per day were detected and eliminated, and about half the house services had still to be covered by the pitometer bureau.

Although this reduction in waste has brought about an apparent increase in the cost of filtration, its economical results have been far‑reaching. The causes which brought about this investigation also resulted in securing an appropriation for the study of the question of increased supply. The writer was in charge of these studies, and the most significant conclusion was that, owing to the excellent results of the efforts for waste restriction, the total consumption and waste of water in the district during the next few years would be far enough below the safe working capacity of the existing aqueduct system to make it entirely safe to postpone the construction of new works, involving the expenditure of several million dollars, in spite of the threatening conditions of a few years ago.

There has been so much controversy over typhoid fever in the District of Columbia that the writer hesitates to discuss this subject. Viewing the situation through the perspective of several years, however, it does not seem to be as hopeless as the criticisms of four or five years ago would lead one to believe.

In Table 9, showing the typhoid death rates, out of nine years given prior to 1905‑06, when the filters were started in operation, only one shows an annual death rate as low as the highest one since that year. Further than this, the annual average typhoid death rate for the period since that year has been one‑third lower than for a corresponding period before the filters were started.

The exhaustive researches of the Public Health and Marine Hospital Service into this whole question, covering a period of about four years, have raised the present filtered water supply of the District of Columbia above any well‑founded criticism. There has long been a strong and growing feeling that the water supply, before filtration was introduced, had been blamed for more than its share of the typhoid, and this is borne out by much evidence that has been presented from time to time.

It is not an unreasonable conjecture, therefore, that perhaps the reduction of one‑third in the total typhoid death rate may represent a much larger reduction in that part of the total which was due to polluted water alone; and that, as the authorities in the District of Columbia and in certain other cities, particularly in the South, are now recognizing, the fight against much of the remaining typhoid must be in the direction of the improvement of milk supplies, precautions against secondary infection, and attention to a large number of details surrounding the individual, which may effectively protect him against the insidious attack of the disease favored by unknown agencies.

EXPERIMENTS IN FILTER CLEANING.

The author refers to the difficulty encountered during the first two summers in keeping the filters cleaned fast enough to maintain the capacity of the plant. The real seriousness of this may be judged from the following facts. The average increase in loss of head on all the filters for the entire year, July 1st, 1906, to July 1st, 1907, was about 0.053 ft. per day. During the 1906 period of low capacity under discussion, the loss of head on twelve of the filters increased for a period of eight days at the average rate of 0.45 ft. per day, or about nine times the normal rate of increase. This difficulty was caused by the presence of large numbers of micro‑organisms in the applied water. During the first summer (1906) this fact was not recognized, but the sudden decrease in capacity was supposed to have been caused by the unusually high and long‑continued turbidity which prevailed during that summer in the Potomac River, and persisted in the water supplied to the filters even after about four days of sedimentation in the reservoirs. During the second summer (1907) the same phenomenon of suddenly and rapidly increasing losses of head appeared again, but without any unusual turbidity in the applied water. Investigation, however, showed the presence of large quantities of organisms, particularly melosira and synedra, in the applied water, and examinations in subsequent years have shown a periodic recurrence of these forms in quantities sufficient to cause the trouble mentioned. In June, 1907, examination showed repeatedly more than 1,000 and 1,500 standard units of melosira per cu. cm., and one count showed nearly 3,000 standard units.

Several expedients were tried in an effort to restore the rapidly decreasing capacity of the filters. One of the earlier conjectures as to the cause of the trouble was that it might be due to the accumulation of large quantities of air under the surface of the sand, as air had been observed bubbling up through the sand, especially in filters which had been in service for some time. The expedient was tried, therefore, of draining the water out of the sand and then re‑filling the filter in the usual manner from below, in the hope of driving out the entrained air. Presumably this treatment got rid of the air, but it did not restore the capacity of the filter, as the point of maximum resistance was in the surface of the sand and not below it.

As the author states, raking the filters was tried and found to give results which were satisfactory enough to meet the emergencies already referred to. When the filters were first put in operation, in the fall of 1905, the method of bringing back the capacity of a filter after the end of a run was to remove all the dirty sand to a depth determined by the marked discoloration caused by the penetration of the clay turbidity. This sometimes necessitated the removal of large quantities of sand at a cleaning, as the turbidity was exceedingly fine, and penetrated at times to a depth of 3 or 4 in.

With the idea of effecting an economy in the cost of cleaning the filters, a schedule of experiments was arranged shortly before July 1st, 1907. The general object of the experiments was to determine, first, the relative costs of all different methods tried; second, whether the removal of only a thin layer of sand, or the mere breaking up of the surface of the sand by thorough raking, would give the filter its proper capacity for the succeeding run; third, whether the filters under these treatments would maintain a high standard of quality in the effluents; fourth, whether the continued application of any less thorough method than the one then in use might materially affect the future capacity of the filters.

To this end the filters were divided into four groups which, during a period of about six months, were subjected to treatments as follows:

Group A.—

Filters scraped deep at the end of each run;

Group B.—

Filters scraped light at the end of each run;

Group C.—

Filters raked at the end of each run, until raking failed to bring back the proper capacity; then they were scraped light, and at the end of the next run the raking was resumed;

Group D.—

Light scrapings and rakings alternate at ends of runs.

The term "deep scraping" means the removal of practically all the discolored sand, in accordance with the usual practice prior to the beginning of these experiments; "light scraping" means the removal of only a thin surface layer of sand. This depth has usually averaged about 3/8 in. "Raking" means the thorough breaking up of the clogged surface of the filter by iron‑toothed rakes, to a depth of about 1 or 2 in.

Results.—A general summary of the results of these experiments is given in Table 29, which also shows the relative costs of the different methods per million gallons of water filtered. A normal period of 9 months just prior to the beginning of these experiments shows a labor cost (corresponding to that in Table 29) of $0.29‑1/4 per million gallons filtered.

TABLE 29—AVERAGE RESULTS.

Per Run:

Per Million Gallons Filtered

Bacteria per cu. cm. in effluent.

Turbidity in effluent.

Group.

Number of filters.

Number of days of service.

Million gallons filtered.

Cost of labor per treatment.

Sand removed in cubic yards.

Sand removed in cubic yards.

Cost of labor.

A

5

82

221.2

$68.44

215

1.11

$0.309

13

1

B

9

36

101.4

29.25

84

0.83

0.288

16

1

C

5

21

60.0

10.92

24

0.40

0.182

18

1

D

10

32

86.0

20.10

46

0.54

0.234

22

1

Capacity of Filters.—The capacity of the filters under the different methods of treatment are shown in a general way in Table 29 for days of service and millions of gallons filtered per run. This element by itself is decidedly in favor of the deep scrapings, and least in favor of the repeated rakings.

A clearer conception of the capacities of the filters under these different conditions may be obtained from the four diagrams, Figure 12, showing, for the four different groups, the average number of days of service of the successive runs. The diagram for Group A shows that the variations in the period of service of the filters scraped each time to clean sand follow a more or less definite curve from year to year. For the period covered by this curve, the tendency seems to be toward a slight decrease in capacity from year to year, as shown by the lower average maximum and minimum in the second year than in the first. Group B shows a sudden decrease in capacity following the first light scrapings and, since that time, a low but quite constant capacity. Group C shows a constantly decreasing capacity with successive rakings. The only significance attaching to the curve after the first raking is the prohibitively low capacity indicated, and the ineffectiveness of the measures taken to restore the capacity after the sixth raking. Group D, after the first raking, shows a prohibitively low and constantly decreasing capacity. The diagrams for C and D indicate a dangerous reduction in capacity if long persisted in. The method followed with Group C may be dismissed with the statement that it is entirely insufficient, and would be of use only in the rarest emergencies.

As far as the question of capacity is concerned, these diagrams indicate that a filter in normal condition may safely be raked once. It is believed that the constantly decreasing capacity shown in Group D is not due so much to the rakings as to the small quantities of sand removed at the alternate scrapings, and therefore it would not be proper to condemn this method of treatment without a further trial in which this defect was remedied. This view seems to be supported by the results of Group B. The low but approximately constant capacity there shown would undoubtedly have been higher if a greater depth of sand had been removed each time.

FIGURE 12—AVERAGE NUMBER OF DAYS OF SERVICE OF SUCCESSIVE RUNS FOR GROUPS A, B, C, AND D.

Quality of the Effluent.—The averages given in Table 29 show but little difference in the bacterial contents of the effluents from the four groups of filters. All are entirely satisfactory, and the differences in favor of one method or another are small. In looking for possible differences in the quality of the effluents from the four groups, it was thought that such differences might be most apparent at a time when the entire plant was working under the most adverse conditions. The bacterial counts, therefore, were summarized for the period from December 23d, 1907, to January 6th, 1908, inclusive, following a period of high turbidity and high bacteria in the raw water, with results as follows:

Group............

A

B

C

D

Maximum.......

204

178

189

206

Minimum........

61

45

62

57

Average.........

120

107

104

155

The following is a summary of the turbidity results for a similar period:

Group............

A

B

C

D

Maximum.......

10.8

11.7

8.7

9.3

Minimum........

6.7

4.7

6.2

5.7

Average.........

8.7

8.3

7.2

7.9

These numbers, though high, do not show any significant differences. All the averages for each group are less than the lowest maximum, and all are greater than the highest minimum, and therefore vary less than do the individual filters, from other causes, within the different groups.

Future Capacity of the Filters.—An indication of the dangers which might affect the future capacity of the filters was shown in the above discussion of the present capacity. A more effective way of showing this was obtained by a study of the initial resistances or losses of head in the four groups. A filter kept in ideal condition would show no increase in this initial loss of head from one run to the next. If there is such an increase, it means that at some future time measures more heroic than ordinarily used would be necessary to restore the proper capacity.

The average initial losses of head for the different groups are plotted on the diagram, Figure 13. Group A shows an initial loss of head, increasing gradually but slightly during more than two years of service. In Group B the initial loss of head increased in a manner similar to that in Group A, up to the time of the beginning of these experiments; after which the increase becomes more rapid. Groups C and D show conditions generally similar to Group B, with some variations which are self‑explanatory.

Conclusions.—The quality of the effluents from all four groups was satisfactory, and no consistent difference was apparent in favor of one or another method of treatment. The method pursued with Group C was entirely insufficient to maintain the capacity indefinitely. The methods pursued in Groups B and D were both insufficient, but would have been more effective if a greater depth of sand had been removed. The costs of treatment of Groups B and D were less than for Group A. It appears, then, that a treatment which would be more economical than the old method of Group A, and would still maintain the proper capacity, would be one similar to that of Groups B or D, with the removal of a quantity of sand greater than was done in the case of these two groups, but less than in the old method.

FIGURE 13—AVERAGE INITIAL LOSSES OF HEAD FOR GROUPS A, B, C, AND D FOR SUCCESSIVE RUNS.

At the time the above results were summarized, it was proposed to proceed with the filter treatment along the lines just mentioned. The writer did not have an opportunity to study the subsequent results, as he was transferred to other work. A statement by the author of any new facts that may have come to light in this connection would be of interest.

Mention should be made, too, of another expedient that was used to hasten the restoration of the capacity of a filter, which proved to be a most useful one. The removal of the scraped sand from a filter was a matter of a good many hours' work, under the most favorable conditions. To get the filters quickly into service again, the dirty sand in a number of them was simply scraped from the surface, heaped into piles, and left there; then the water was turned in, and the filter was started again. This was done with some hesitation at first for fear the presence of the piles of dirty sand might cause high bacterial counts in the effluents of those filters. No such effect was observed, however, the counts being entirely normal throughout. The writer subsequently found the same treatment being applied as an emergency measure at the Torresdale plant, in Philadelphia, and, through the courtesy of the Chief Engineer of the Bureau of Filtration, was furnished with the bacterial counts through a number of runs made under these conditions, and there, too, the results were entirely normal.

There was practically no economy in this method, as the sand had ultimately to be ejected and washed. The piling up of the sand had the effect of reducing the effective filtering area by a small percentage, with a corresponding increase in the actual rate of filtration, but this was of trifling importance. The great benefit derived from the method was the saving of time in getting a filter back into service after scraping, and in this respect it was very valuable.

PHYSICAL THEORY OF PURIFICATION OF WATER BY SLOW SAND FILTERS.

The first and most natural conception of the action of a sand filter is that the removal of impurities is effected by a straining action. This, of course, is perfectly true as far as it relates to a large part of the visible impurities. Much of this is gross enough to be intercepted and held at the surface of the sand. This very straining action is an accumulative one. After a quantity of suspended matter thus strained out mats itself on the surface of the sand, it in turn becomes a strainer, even better adapted than the clean sand surface which supports it for the removal of suspended matter from the water.

This, however, cannot explain certain features of the purification of water by a layer of sand. The removal of color, the reduction of nitrates, and certain other changes in the organic content of the water have for a long time been recognized as due to a bio‑chemical action carried on by certain bacteria in the sand. Both the straining action and this bio‑chemical action are not all‑sufficient for the explanation of certain phenomena, and it has been recognized, too, that sedimentation in the pores of the sand played a large part in the purification process in those cases in which it was apparent that the biological agencies were not the chief ones.

In the purification of water containing only insignificant quantities of suspended matter, but a relatively large amount of unstable organic matter, it will be conceded at once that the chief factor in the purification is the nitrification produced by the bacteria in the upper layers of the sand. On the other hand, the purification by sand filters of a hypothetical water containing no organic matter, but only finely‑divided mineral matter in suspension, could take place only by the physical deposition of the particles upon the sand grains. Between these two extremes lie all classes of water. In all problems of water purification by filtration through sand, both these factors—biological action and sedimentation—play their parts, assisting and supplementing each other, the relative importance of one factor or the other depending on the place of the particular water in question on the scale between the two extreme conditions just mentioned.

In Mr. Hazen's paper on "Sedimentation"[1] there is an interesting development of the theory of the removal of suspended matter by sedimentation in the pores of a layer of sand. The factors influencing this removal are the rate of filtration, the effective size of the sand, and the temperature of the water. For the conditions at the Washington plant, it may be assumed that the first two of these factors are constant. The third factor, however, varies through wide limits, and the observations on the turbidity removal, and on the different phases of the filter operation of which the turbidity of the water is a factor under varying temperature conditions, together with the known relations between hydraulic values and temperatures of water, furnished good substantiative evidence that this highly‑induced sedimentation may be a considerable factor in the purification of the water as effected at this plant. This temperature relation, briefly stated, is as follows: For particles of a size so small that the viscosity of the water is the controlling factor in determining the velocity of their subsidence in still water, that velocity will vary directly as (T + 10) / 60, in which T is the temperature, in degrees, Fahrenheit. That is, when the temperature of the water is between 70° and 80° Fahr., a particle will settle with twice the velocity it would have if the water were near the freezing point.

The layer of sand in a slow sand filter may be considered as a very great number of small sedimentation basins communicating one with another, not in the manner of basins connected in series, but rather, as Mr. Hazen has expressed it, as a long series of compartments connected at one side only with a passageway in which a current is maintained. In any section of the sand layer there are areas through which the water passes with a velocity much greater than its mean velocity through the total area of voids, while there are other areas in which the velocity is very much less, perhaps in an almost quiescent state from time to time, greatly favoring the deposition of particles, but with a gentle intermittent circulation, displacing the settled or partly‑settled water and supplying from the main currents water containing more suspended matter particles to be removed. There is thus a considerable percentage of the total volume of voids in which the water is subjected to very favorable conditions for sedimentation, almost perfect stillness and an exceedingly small distance for a particle to settle before it strikes bottom on the surface of a grain of sand.

1 Transactions, Am. Soc. C. E., Vol. LIII, p. 59.

If sedimentation were the predominating factor in the purification of the water, we would then expect to find the following phenomena in the operation of the filters: A more rapid deposition of a given amount of sediment under summer temperature conditions than under winter, as the water passes through the sand, and therefore, for the former condition of higher temperature:

- (a) A greater concentration of this turbidity-producing material in the top layer of sand, or, in other words, a thinner sand layer to be removed in scraping if all the dirty sand is removed;

- (b) Because of the greater concentration, a greater rate of Increase of the loss of head, and consequently shorter periods of service between scrapings;

- (c) A higher limit for turbidity in the water applied to the filter to produce a given turbidity in the effluent.

The operation of this plant during the first year and a half offered an excellent opportunity for the study of sedimentation in the sand, and the data in Table 30 are presented to show that certain of the phenomena of filter operation observed during this period seem to be fairly explicable by the physical theory of purification. These data are given only for the period of operation before the summer of 1907. At that time the experiments in filter cleaning already described were begun. Before that time, whenever a filter had been cleaned, all the discolored sand had been removed, leaving for the following run a new sand surface substantially in the perfect condition of a newly‑constructed filter. After that time the experimental methods of cleaning, and the new routine adopted as a result thereof, interfered with the tracing of the evidence as clearly as during the earlier periods.

TABLE 30—SERVICE PERIODS AND SCRAPING DEPTHS FOR RUNS ENDING IN VARIOUS MONTHS; COVERING ENTIRE PERIOD, OCTOBER 1ST,  1905, TO MARCH 1ST, 1907.

Month.

Number of filters.

Average period of service in days.

Average depth of sand removed, in inches.

Mean temperature, in degrees, Fahrenheit.

January

13

75

2.09

39

February

6

98

2.46

37

March

5

130

2.66

41

April

8

149

2.96

53

May

7

130

2.80

67

June

11

124

2.35

77

July

17

70

2.12

81

August

2

49

1.98

80

September

5

73

2.48

76

October

37

70

1.56

64

November

20

42

0.81

49

December

14

57

0.94

40

FIGURE 14—PERIODS OF SERVICE AND DEPTHS OF SCRAPING FOR RUNS ENDING IN VARIOUS MONTHS COVERING ENTIRE PERIOD OCT. 1, 1905, TO MAR. 1, 1907.

Table 30 and the corresponding diagram, Figure 14, show the general variations in the length of runs and depth of penetration, with the seasonal temperature changes. The increase in length of runs and quantity of sand removed under low temperature conditions is very marked. There is, however, a secondary maximum which appears, as the diagram shows, where a minimum for the year would be expected. This may have been an irregularity occurring this one year, which will not appear in the average of several years, and caused by some factor which has escaped observation. A careful analysis of the data at hand fails to show any explanation for it. It may exist in some of the little‑understood biological actions which have their maximum effect under warm‑water conditions, or it may be due—in some obscure way—to the liberation of air under the surface of the sand, accumulating with pressure enough to break the surface at innumerable points, thereby reducing the loss of head and extending the period of service. Some evidence was observed pointing to this explanation, but it was never conclusively proven.

The general effect of temperature changes on the rapidity of removal of the sediment and its consequent concentration in the sand layer, however, seems plainly evident.

In corroboration of the third point mentioned in the theoretical consideration of turbidity removal in the filters, the daily turbidities of the filtered water have been classified and summarized for different turbidities in the applied water, and also for different temperatures. The average turbidities thus obtained are given in Table 31.

TABLE 31—TURBIDITY IN FILTERED WATER AT DIFFERENT TEMPERATURES PRODUCED BY GIVEN TURBIDITY IN APPLIED WATER.

Turbidity of applied water.

TEMPERATURE, IN DEGREES, FAHRENHEIT.

40°

40°‑50°

50°‑60°

60°‑70°

70°

20

1.8

1.3

1.2

1.5

1.7

20-40

4.8

5.0

3.5

3.0

2.6

40-60

7.9

6.9

5.4

...

3.7

60-80

10.7

7.7

...

...

5.4

80-100

11.3

...

...

...

...

100

...

...

...

...

12.0[1]

1 For an average turbidity = 150. approximately.

The influence of the temperature of the water on the turbidity of the effluent is very pronounced. For a temperature of less than 40° Fahr. (actual average temperature about 35°), the turbidity of the filtered water for a given turbidity of the applied water is practically twice as great as for a temperature greater than 70° (actual average temperature about 75°). This fact fits in very nicely with the influence of temperature on sedimentation. Referring again to this temperature relation, as set forth on a previous page, the hydraulic subsiding value of a particle in water, of a size so small that viscosity is the controlling factor in its downward velocity, is approximately twice as great at 75° as at 35 degrees. We would then expect to find that, in order to obtain a given turbidity in the filtered water, a raw water may be applied at 75°, having twice the turbidity of the water applied at 35°, to produce the same turbidity; and further, as the turbidity of the filtered water, for a given temperature condition, varies quite directly in proportion to the turbidity in the applied water, it follows that an applied water of given turbidity will produce an effluent at 35° with a turbidity twice as great as at 75 degrees. This is quite in accordance with the facts obtained in actual operation, as indicated on the diagram, Figure 15.

Preliminary Treatment of the Water.—The most striking features of the bacterial results given in Table 4 are, first, the uniformly low numbers of bacteria in the filtered water during perhaps 8 or 9 months of the year, and the increase in numbers each winter. This is shown clearly in the analysis of bacterial counts in Table 32.

TABLE 32—CLASSIFICATION OF DAILY BACTERIAL COUNTS IN THE FILTERED-WATER RESERVOIR DURING THE PERIOD, NOVEMBER 1ST, 1905, TO FEBRUARY 1ST, 1908.

Bacterial count between:

No. of days.

Percentage of whole.

0 and 20 per cu. cm.

291

41.0

20 and 40 per cu. cm.

245

34.6

40 and 60 per cu. cm.

63

8.9

60 and 80 per cu. cm.

30

4.2

80 and 100 per cu. cm.

28

4.0

92.7

100 and 200 per cu. cm.

29

4.1

200 and 300 per cu. cm.

13

1.8

300 and 500 per cu. cm.

5

0.7

500 and 1000 per cu. cm.

5

0.7

7.3

Total

100.0

The tests for Bacillus Coli in Table 5 show results which correspond closely to these, with this organism detected only infrequently, except during the periods of high bacteria, and both of these are parallel to the turbidity variations in the filtered water. These variations follow closely the variations in the turbidity and in the bacterial content of the water applied to the filters.

By all standards of excellence, the sanitary quality of the water during the greater part of the time is beyond criticism. In view of the close parallelism of turbidity and bacterial results in the applied and in the filtered water, it is entirely logical to conclude that, if the quality of the applied water could be maintained continually through the winter as good as, or better than, it is during the summer, then the filtered water would be of the perfect sanitary quality desired throughout the entire year.

This was all foreseen ten years ago, when Messrs. Hering, Fuller, and Hazen recommended auxiliary works for preliminary treatment of the supply, although, as the author states, these works were not provided for in the original construction. As prejudice against the use of a coagulant seemed to be at the bottom of the opposition to the preliminary treatment, a campaign of education bearing on this point was instituted, in addition to the systematic studies of different preliminary methods to which the author refers. As a result of the combined efforts of all those interested in promoting this improvement, an appropriation was finally made for the work in 1910. The coagulating plant has since been built, and the writer is informed that coagulation was tried on a working scale a short time ago during a period of high turbidity. A statement of the results of this treatment on the purification of the water in the reservoir system and in the filter plant would be of great interest.

FIGURE 15—TURBIDITY IN APPLIED WATER.

Hydraulic Replacing of Filter Sand.—The author has adopted a method of replacing clean sand in the filters which will commend itself to engineers as containing possibilities of economy in operation. The first experiments in the development of this method at the Washington plant were carried out some three years ago, while the writer was still there. Substantially the same methods were used then as are described in this paper, but examination of the sand layer by cutting vertically downward through it after re‑sanding in this manner showed such a persistent tendency toward the segregation of the coarse material as to hold out rather discouraging promises of success. The greatest degree of separation seemed to be caused by the wash of the stream discharging sand on the surface. It was observed that, near the point where the velocity of the stream was practically destroyed, there seemed to be a tendency to scour away the fine sand and leave the coarse material by itself, and pockets of this kind were found at many points throughout the sand layer. The author states that, in the recent treatment of the filters by this method, there has been no apparent tendency for the materials to separate into different sizes, and it is fortunate if this work can be done in such a manner as to avoid this separation entirely.

It may be questioned whether a certain amount of segregation of the materials will make any practical difference in the efficiency of a filter. In all probability this depends on the degree of the segregation, the quantity of pollution in the water to be filtered, the rate of filtration, and the uniformity of methods followed in the operation, etc. For an applied water as excellent in quality as that of the Washington City Reservoir during favorable summer conditions, a considerable degree of segregation might exist without producing any diminution in efficiency. For a badly polluted water, however, such as the applied water at this plant during certain winter periods, or the water of a great many other polluted supplies, it might be found that even a slight lack of homogeneity in the sand might make an appreciable difference in the results of filtration.

As a result of the experiments herein described, however, this method may be applied at other plants where conditions seem to warrant it, with a largely increased measure of confidence; although, as in the case of the adoption of any new or radical departure, that confidence must not be permitted to foster contempt of the old and tried methods, but its operation must be watched with the utmost caution, until long experience shall have demonstrated its perfect suitability and defined its limitations.

E. D. Hardy, M. Am. Soc. C. E. (by letter).—It was not the writer's original intention to enter into a discussion of either the theory of water purification or of the experimental work on sand handling, but simply to present the main results of operation largely in tabular form. He is gratified, however, to have these sides of the question so ably brought out in Mr. Longley's discussion.

Mr. Hazen referred to the inferior efficiencies of the experimental filters for rate studies (as shown in Table 20) in the removal of the B. Coli from the water tested. This inferiority is really less than the figures in the table would indicate, as the tests for the experimental filters were presumptive only (as shown by the note at the foot of Table 20), while those for the main filters were carried through all the confirmatory steps.

From experiments[1] made by Messrs. Longley and Baton in the writer's office, it would seem reasonable to assume that about one‑half of the positive results, would have been eliminated had the confirmatory steps been taken. In other words, the figures showing the number of positive tests for B. Coli in Table 20 should be divided by two when comparing them with corresponding ones for the main filters.

Mr. Knowles seems somewhat apprehensive regarding the methods described in the paper of restoring the capacity of the filters by raking, and replacing sand by the hydraulic method, and yet, from Mr. Johnson's discussion, it would seem that the practice of raking filters between scrapings had recently been adopted at the Pittsburg plant.

1 Published in the Journal of Infectious Diseases, Vol. 4, No. 3, June, 1907.

Before the practice of raking was finally adopted as a part of the routine filter operation, the subject was given a great deal of thought and study, as may be seen by referring to Mr. Longley's discussion.

The re‑sanding has been done by the hydraulic method, for nearly two years, and, as far as the writer is able to judge, this method has been more economical and also more satisfactory in every way than the old one. As Mr. Hazen states, this does not prove that the hydraulic method would be as satisfactory for other filter plants and other grades of sand. The elevated sand bins at the Washington plant fit in well with this scheme, and save the expense of one shoveling of the sand; and the low uniformity coefficient of the sand is favorable in decreasing its tendency to separate into pockets or strata of coarse and fine sand. The method of washing is also well adapted to this method of re‑sanding, as the sand is made very clean in its passage through the washers and storage bins. The hydraulic method of replacing sand tends to make it cleaner still, because any clay which may be left in the sand is constantly being carried away over the weir and out of the bed, to the sewer. Sand replaced by the hydraulic method is much more compact than when replaced by other methods, and consequently the depth of penetration of mud in a filter thus re‑sanded is less. Careful tests of the effluents from filters which have been re‑sanded by the two methods have invariably shown the superiority of the hydraulic method.

The experiment of replacing sand by water, referred to by Mr. Longley, was not considered a success at the time, and the method was abandoned for about a year. At that time an attempt was made to complete the re‑sanding of a filter which had been nearly completed by the old method. The precaution of filling the filter with water was not taken, nor was any special device used for distributing the sand. When this method was again taken up, various experiments were tried before the present method was adopted.

Mr. Whipple's remarks on the results from the operation of filters under winter conditions are very interesting, and, considering his standing as an authority in such matters, they are worth careful consideration.

In the operation of the Washington plant, it has always been noticeable that the results were much poorer in winter than in summer. In fact, nearly all the unsatisfactory water which has been delivered to the city mains has been supplied during the winter months. On the other hand, the typhoid death rate has always been comparatively low in cold weather. These facts would seem to indicate that the water supply was not responsible for the typhoid conditions.

*** END OF THIS PROJECT GUTENBERG EBOOK ***

Updated editions will replace the previous one—the old editions will be renamed.

Creating the works from print editions not protected by U.S. copyright law means that no one owns a United States copyright in these works, so the Foundation (and you!) can copy and distribute it in the United States without permission and without paying copyright royalties. Special rules, set forth in the General Terms of Use part of this license, apply to copying and distributing Project Gutenberg™ electronic works to protect the PROJECT GUTENBERG™ concept and trademark. Project Gutenberg is a registered trademark, and may not be used if you charge for an eBook, except by following the terms of the trademark license, including paying royalties for use of the Project Gutenberg trademark. If you do not charge anything for copies of this eBook, complying with the trademark license is very easy. You may use this eBook for nearly any purpose such as creation of derivative works, reports, performances and research. Project Gutenberg eBooks may be modified and printed and given away—you may do practically ANYTHING in the United States with eBooks not protected by U.S. copyright law. Redistribution is subject to the trademark license, especially commercial redistribution.

START: FULL LICENSE

THE FULL PROJECT GUTENBERG LICENSE

PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK

To protect the Project Gutenberg™ mission of promoting the free distribution of electronic works, by using or distributing this work (or any other work associated in any way with the phrase “Project Gutenberg”), you agree to comply with all the terms of the Full Project Gutenberg™ License available with this file or online at www.gutenberg.org/license.

Section 1. General Terms of Use and Redistributing Project Gutenberg™ electronic works

1.A. By reading or using any part of this Project Gutenberg™ electronic work, you indicate that you have read, understand, agree to and accept all the terms of this license and intellectual property (trademark/copyright) agreement. If you do not agree to abide by all the terms of this agreement, you must cease using and return or destroy all copies of Project Gutenberg™ electronic works in your possession. If you paid a fee for obtaining a copy of or access to a Project Gutenberg™ electronic work and you do not agree to be bound by the terms of this agreement, you may obtain a refund from the person or entity to whom you paid the fee as set forth in paragraph 1.E.8.

1.B. “Project Gutenberg” is a registered trademark. It may only be used on or associated in any way with an electronic work by people who agree to be bound by the terms of this agreement. There are a few things that you can do with most Project Gutenberg™ electronic works even without complying with the full terms of this agreement. See paragraph 1.C below. There are a lot of things you can do with Project Gutenberg™ electronic works if you follow the terms of this agreement and help preserve free future access to Project Gutenberg™ electronic works. See paragraph 1.E below.

1.C. The Project Gutenberg Literary Archive Foundation (“the Foundation” or PGLAF), owns a compilation copyright in the collection of Project Gutenberg™ electronic works. Nearly all the individual works in the collection are in the public domain in the United States. If an individual work is unprotected by copyright law in the United States and you are located in the United States, we do not claim a right to prevent you from copying, distributing, performing, displaying or creating derivative works based on the work as long as all references to Project Gutenberg are removed. Of course, we hope that you will support the Project Gutenberg™ mission of promoting free access to electronic works by freely sharing Project Gutenberg™ works in compliance with the terms of this agreement for keeping the Project Gutenberg™ name associated with the work. You can easily comply with the terms of this agreement by keeping this work in the same format with its attached full Project Gutenberg™ License when you share it without charge with others.

1.D. The copyright laws of the place where you are located also govern what you can do with this work. Copyright laws in most countries are in a constant state of change. If you are outside the United States, check the laws of your country in addition to the terms of this agreement before downloading, copying, displaying, performing, distributing or creating derivative works based on this work or any other Project Gutenberg™ work. The Foundation makes no representations concerning the copyright status of any work in any country other than the United States.

1.E. Unless you have removed all references to Project Gutenberg:

1.E.1. The following sentence, with active links to, or other immediate access to, the full Project Gutenberg™ License must appear prominently whenever any copy of a Project Gutenberg™ work (any work on which the phrase “Project Gutenberg” appears, or with which the phrase “Project Gutenberg” is associated) is accessed, displayed, performed, viewed, copied or distributed:

This eBook is for the use of anyone anywhere in the United States and most other parts of the world at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org. If you are not located in the United States, you will have to check the laws of the country where you are located before using this eBook.

1.E.2. If an individual Project Gutenberg™ electronic work is derived from texts not protected by U.S. copyright law (does not contain a notice indicating that it is posted with permission of the copyright holder), the work can be copied and distributed to anyone in the United States without paying any fees or charges. If you are redistributing or providing access to a work with the phrase “Project Gutenberg” associated with or appearing on the work, you must comply either with the requirements of paragraphs 1.E.1 through 1.E.7 or obtain permission for the use of the work and the Project Gutenberg™ trademark as set forth in paragraphs 1.E.8 or 1.E.9.

1.E.3. If an individual Project Gutenberg™ electronic work is posted with the permission of the copyright holder, your use and distribution must comply with both paragraphs 1.E.1 through 1.E.7 and any additional terms imposed by the copyright holder. Additional terms will be linked to the Project Gutenberg™ License for all works posted with the permission of the copyright holder found at the beginning of this work.

1.E.4. Do not unlink or detach or remove the full Project Gutenberg™ License terms from this work, or any files containing a part of this work or any other work associated with Project Gutenberg™.

1.E.5. Do not copy, display, perform, distribute or redistribute this electronic work, or any part of this electronic work, without prominently displaying the sentence set forth in paragraph 1.E.1 with active links or immediate access to the full terms of the Project Gutenberg™ License.

1.E.6. You may convert to and distribute this work in any binary, compressed, marked up, nonproprietary or proprietary form, including any word processing or hypertext form. However, if you provide access to or distribute copies of a Project Gutenberg™ work in a format other than “Plain Vanilla ASCII” or other format used in the official version posted on the official Project Gutenberg™ website (www.gutenberg.org), you must, at no additional cost, fee or expense to the user, provide a copy, a means of exporting a copy, or a means of obtaining a copy upon request, of the work in its original “Plain Vanilla ASCII” or other form. Any alternate format must include the full Project Gutenberg™ License as specified in paragraph 1.E.1.

1.E.7. Do not charge a fee for access to, viewing, displaying, performing, copying or distributing any Project Gutenberg™ works unless you comply with paragraph 1.E.8 or 1.E.9.

1.E.8. You may charge a reasonable fee for copies of or providing access to or distributing Project Gutenberg™ electronic works provided that:

• You pay a royalty fee of 20% of the gross profits you derive from the use of Project Gutenberg™ works calculated using the method you already use to calculate your applicable taxes. The fee is owed to the owner of the Project Gutenberg™ trademark, but he has agreed to donate royalties under this paragraph to the Project Gutenberg Literary Archive Foundation. Royalty payments must be paid within 60 days following each date on which you prepare (or are legally required to prepare) your periodic tax returns. Royalty payments should be clearly marked as such and sent to the Project Gutenberg Literary Archive Foundation at the address specified in Section 4, “Information about donations to the Project Gutenberg Literary Archive Foundation.”

• You provide a full refund of any money paid by a user who notifies you in writing (or by e-mail) within 30 days of receipt that s/he does not agree to the terms of the full Project Gutenberg™ License. You must require such a user to return or destroy all copies of the works possessed in a physical medium and discontinue all use of and all access to other copies of Project Gutenberg™ works.

• You provide, in accordance with paragraph 1.F.3, a full refund of any money paid for a work or a replacement copy, if a defect in the electronic work is discovered and reported to you within 90 days of receipt of the work.

• You comply with all other terms of this agreement for free distribution of Project Gutenberg™ works.

1.E.9. If you wish to charge a fee or distribute a Project Gutenberg™ electronic work or group of works on different terms than are set forth in this agreement, you must obtain permission in writing from the Project Gutenberg Literary Archive Foundation, the manager of the Project Gutenberg™ trademark. Contact the Foundation as set forth in Section 3 below.

1.F.

1.F.1. Project Gutenberg volunteers and employees expend considerable effort to identify, do copyright research on, transcribe and proofread works not protected by U.S. copyright law in creating the Project Gutenberg™ collection. Despite these efforts, Project Gutenberg™ electronic works, and the medium on which they may be stored, may contain “Defects,” such as, but not limited to, incomplete, inaccurate or corrupt data, transcription errors, a copyright or other intellectual property infringement, a defective or damaged disk or other medium, a computer virus, or computer codes that damage or cannot be read by your equipment.

1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the “Right of Replacement or Refund” described in paragraph 1.F.3, the Project Gutenberg Literary Archive Foundation, the owner of the Project Gutenberg™ trademark, and any other party distributing a Project Gutenberg™ electronic work under this agreement, disclaim all liability to you for damages, costs and expenses, including legal fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH DAMAGE.

1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a defect in this electronic work within 90 days of receiving it, you can receive a refund of the money (if any) you paid for it by sending a written explanation to the person you received the work from. If you received the work on a physical medium, you must return the medium with your written explanation. The person or entity that provided you with the defective work may elect to provide a replacement copy in lieu of a refund. If you received the work electronically, the person or entity providing it to you may choose to give you a second opportunity to receive the work electronically in lieu of a refund. If the second copy is also defective, you may demand a refund in writing without further opportunities to fix the problem.

1.F.4. Except for the limited right of replacement or refund set forth in paragraph 1.F.3, this work is provided to you ‘AS-IS’, WITH NO OTHER WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PURPOSE.

1.F.5. Some states do not allow disclaimers of certain implied warranties or the exclusion or limitation of certain types of damages. If any disclaimer or limitation set forth in this agreement violates the law of the state applicable to this agreement, the agreement shall be interpreted to make the maximum disclaimer or limitation permitted by the applicable state law. The invalidity or unenforceability of any provision of this agreement shall not void the remaining provisions.

1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the trademark owner, any agent or employee of the Foundation, anyone providing copies of Project Gutenberg™ electronic works in accordance with this agreement, and any volunteers associated with the production, promotion and distribution of Project Gutenberg™ electronic works, harmless from all liability, costs and expenses, including legal fees, that arise directly or indirectly from any of the following which you do or cause to occur: (a) distribution of this or any Project Gutenberg™ work, (b) alteration, modification, or additions or deletions to any Project Gutenberg™ work, and (c) any Defect you cause.

Section 2. Information about the Mission of Project Gutenberg™

Project Gutenberg™ is synonymous with the free distribution of electronic works in formats readable by the widest variety of computers including obsolete, old, middle-aged and new computers. It exists because of the efforts of hundreds of volunteers and donations from people in all walks of life.

Volunteers and financial support to provide volunteers with the assistance they need are critical to reaching Project Gutenberg™’s goals and ensuring that the Project Gutenberg™ collection will remain freely available for generations to come. In 2001, the Project Gutenberg Literary Archive Foundation was created to provide a secure and permanent future for Project Gutenberg™ and future generations. To learn more about the Project Gutenberg Literary Archive Foundation and how your efforts and donations can help, see Sections 3 and 4 and the Foundation information page at www.gutenberg.org.

Section 3. Information about the Project Gutenberg Literary Archive Foundation

The Project Gutenberg Literary Archive Foundation is a non-profit 501(c)(3) educational corporation organized under the laws of the state of Mississippi and granted tax exempt status by the Internal Revenue Service. The Foundation’s EIN or federal tax identification number is 64-6221541. Contributions to the Project Gutenberg Literary Archive Foundation are tax deductible to the full extent permitted by U.S. federal laws and your state’s laws.

The Foundation’s business office is located at 809 North 1500 West, Salt Lake City, UT 84116, (801) 596-1887. Email contact links and up to date contact information can be found at the Foundation’s website and official page at www.gutenberg.org/contact

Section 4. Information about Donations to the Project Gutenberg Literary Archive Foundation

Project Gutenberg™ depends upon and cannot survive without widespread public support and donations to carry out its mission of increasing the number of public domain and licensed works that can be freely distributed in machine-readable form accessible by the widest array of equipment including outdated equipment. Many small donations ($1 to $5,000) are particularly important to maintaining tax exempt status with the IRS.

The Foundation is committed to complying with the laws regulating charities and charitable donations in all 50 states of the United States. Compliance requirements are not uniform and it takes a considerable effort, much paperwork and many fees to meet and keep up with these requirements. We do not solicit donations in locations where we have not received written confirmation of compliance. To SEND DONATIONS or determine the status of compliance for any particular state visit www.gutenberg.org/donate.

While we cannot and do not solicit contributions from states where we have not met the solicitation requirements, we know of no prohibition against accepting unsolicited donations from donors in such states who approach us with offers to donate.

International donations are gratefully accepted, but we cannot make any statements concerning tax treatment of donations received from outside the United States. U.S. laws alone swamp our small staff.

Please check the Project Gutenberg web pages for current donation methods and addresses. Donations are accepted in a number of other ways including checks, online payments and credit card donations. To donate, please visit: www.gutenberg.org/donate

Section 5. General Information About Project Gutenberg™ electronic works

Professor Michael S. Hart was the originator of the Project Gutenberg™ concept of a library of electronic works that could be freely shared with anyone. For forty years, he produced and distributed Project Gutenberg™ eBooks with only a loose network of volunteer support.

Project Gutenberg™ eBooks are often created from several printed editions, all of which are confirmed as not protected by copyright in the U.S. unless a copyright notice is included. Thus, we do not necessarily keep eBooks in compliance with any particular paper edition.

Most people start at our website which has the main PG search facility: www.gutenberg.org.

This website includes information about Project Gutenberg™, including how to make donations to the Project Gutenberg Literary Archive Foundation, how to help produce our new eBooks, and how to subscribe to our email newsletter to hear about new eBooks.

Table of Contents

The Project Gutenberg eBook of Transactions of the American Society of Civil Engineers, vol. LXXII, June, 1911, by American Society of Civil Engineers and E. D. Hardy

AMERICAN SOCIETY OF CIVIL ENGINEERS

INSTITUTED 1852

TRANSACTIONS

Paper No. 1191

WATER PURIFICATION PLANT, WASHINGTON, D. C. RESULTS OF OPERATION.1

With Discussion by Messrs. Allen Hazen, George A. Johnson, Morris Knowles, George C. Whipple, F. F. Longley, and E. D. Hardy.

DISCUSSION

Experiments in Filter Cleaning.

Physical Theory of Purification of Water by Slow Sand Filters.

THE FULL PROJECT GUTENBERG LICENSE