Transactions of the American Society of Civil Engineers, vol. LXXII, June, 1911 / Water Purification Plant, Washington, D. C. Results of Operation. - American Society of Civil Engineers; E. D. Hardy

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.
Month.	Office and laboratory.	Pumping station.	Sand handling.	Repairs, etc.	Parking (care of grounds).	Experimental filters.	Main office.	Total.
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.
Month.	Office and laboratory.	Pumping station.	Sand handling.	Repairs, etc.	Parking (care of grounds).	Experimental filters.	Main office.	Total.
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.]