Modern Filter Plant of New Chester Water Company
Ten Rectangular Filter Units Superimposed Above Clear Water Basin—Two-Compartment Sedimentation Basins—Riffle Plate Type Aerators—Automatic Chlorinators in Duplicate
ISAAC S. WALKER
General Manager, New Chester Water Company
THE new modern filter plant built for the New Chester Water Company of Chester, Pa., by the New York Continental-Jewell Filtration Company, was placed in initial operation about May 1. The original contract for this work was let on October 28, 1916, but the work was greatly delayed due to construction difficulties encountered during the war period. The New Chester Water Company was incorporated in the year 1885. For thirty-five years it has been engaged in serving Chester and adjoining communities with the most important and indispensable of all commodities, namely,—pure and wholesome water. The territory served by the company comprises the City of Chester, the townships of Chester, Nether Providence, Aston, Upper Chichester, Lower Chichester and Edgmont, and the boroughs of Marcus Hook, Parkside, Linwood, trainer and Upland. The Water Company supplies at the present time a total population of possibly 75,000 to 80,000. There are about 14,000 consumers, all of whom are metered.
Prior to the construction of the new plant the water supply was filtered at the plant located at Harrison Hill about three miles outside of the city. This plant was also of the New York Continental-Jewell Filtration type, consisting of 18 filters; 12 of which were of the old style wooden tub type and 6 of the more modern concrete type. With the former arrangement the operation of the works was as follows:
Pumping Station and Reservoir
The pumping station is located at Front and Fulton Sts., Chester, Pa., and draws its water from the Delaware river through two suction lines; one 30-inch and one 36-inch in diameter, extending from the point about 550 feet out in the Delaware River channel to a suction well located on the shore. From this well the water is pumped by two 10-million gallon Snow pumping engines through a single 30-inch force main, approximately 3 miles long to the reservoirs at Harrison Hill. These reservoirs are in duplicate, each with a capacity of about 6 1/2 million gallons, and were used for the storage and coagulation of raw water. From these basins the water flowed by gravity to the filtration plant and from thence into a filtered water basin of 3 million gallons capacity, from which it was supplied by gravity to the City distribution system. The elevation of the reservoirs is approximately 200 feet above the city.
New Plant of Gravity Mechanical Type
The new plant is of concrete construction, of the gravity mechanical type, consisting of a two compartment sedimentation basin, 10 rectangular filter units superimposed above a clear water basin, and a low lift pumping, plant, and is located on ground adjoining the present pumping station at Front and Fulton Streets. The location of the new plant along the river has necessitated the double pumping of all the water and for this purpose the low lift pumping station has been constructed adjoining the high lift station, and is equipped with two 12 million gallon centrifugal pumps, operated by steam turbines. The suction lines of these pumps have been connected up to the old suction lines extending from the intake well and the pumps deliver raw water through a 36-inch raw water supply main to the new sedimentation basins. The lift is approximately 30 feet.
Prior to the entry of the water into the sedimentation basin it first passes over aerators of the riffle plate type to insure adequate aeration of the raw water before it enters the basins. It is anticipated that these aerators will be effective in removing tastes which are occasionally experienced during the winter months. Arrangements are such that the aerators may be by-passed and the raw water discharged directly into the sedimentation basins. After passing through the sedimentation basins, the water is discharged through a 36-inch main extending from the sedimentation basin to the end of the filter pipe gallery. It then passes through a concrete flume in the pipe gallery to which connections are made for the supply to each filter. After passing through the filters the water is discharged through the down draft pipes into a central compartment of the clear water basin below the pipe gallery. From this compartment it passes through a Venturi meter, located at the bottom of the basin and into the basin proper. The Venturi meter records the entire output from the plant. Immediately after passing through the meter the. water is sterilized with chlorine. It has a retention period of about two hours in the basin before being pumped to the city.
System to Be Turned Over to Direct Pumping Basis
The high lift pumps now take their suction from the filtered water basin and are used to pump filtered water to the reservoirs at Harrison Hill, which were formerly used for raw water storage. With this arrangement, therefore, the filtered water reservoir supply now amounts to about 13 millions gallons compared with only 3 million gallons stored under the old system. Arrangements are now being made to connect the 30-inch force main direct to the distribution system, thus turning the system over onto a direct pumping basis, and converting the large main formerly used as a transmission main into a distribution line. With this arrangement also, the pressures in the city will be increased from 15 to 20 lbs.
The new plant is designed for a normal capacity of 12,500,000 gallons per 24 hours. The effluent controllers are arranged for adjustment for rates up to 25 per cent, in excess of the normal rate.
Construction of Sedimentation Basin
The sedimentation basin, as constructed, has a capacity of 1,250,000 gallons. The basin is divided into two compartments. With the plant running at its rated capacity of 1,250,000 gallons per 24 hours, the subsidence period will be about 2 1/2 hours. Sulphate of alumina is used for coagulation. The solution is controlled by the manual adjustment of orifices in orifice tanks. The solution discharges from the orifice tanks into the raw water suction main directly ahead of the low lift pumps.
In ordinary operation there is sufficient alkalinity in the raw water to insure a complete decomposition of the applied coagulant. Provision has been made however for applying lime solution if there is at any time a deficiency of alkalinity in the raw water. The quantity of lime supplied will be governed by manual adjustment of a dry feed machine, which will feed the dry hydrated lime into a receiving tank at which point it will receive a supply of water, and the solution so formed will be discharged into the raw water suction main at a point in advance of that at which the sulphate of alumina solution is applied.
Filter Units and Equipment
There are ten filter units, each of which are divided into two compartments by means of a transverse central wash water flume. Each compartment has an area of 224 square feet; being 14 feet wide and 16 feet long. The two compartments of each filter are controlled by one set of operating valves. The gutters for removing the waste wash water are constructed of concrete and discharge into the central flume above mentioned. From this flume the waste water is conveyed to the sewer main.
The filters are equipped with Wheeler filter bottoms, in accordance with the standard method of construction of that type of bottom.
Above the Wheeler bottoms the gravel is placed in six layers ranging from 1 1/8-inch at the bottom to 1/8-inch at the top, totalling 9-inch in depth. The filter sand is provided in each filter to a depth of 27 inches. The effective size of the sand is from .50 millimeters to .60 millimeters, with a uniformity coefficient of not more than 1.5.
Filter Valves Hydraulically Controlled
All filter valves are hydraulically operated and controlled at the marble operating tables, located on the operating floor. Each filter is equipped with an indicating loss of head gauge mounted upon its operating table. The effluent from each filter is controlled by means of a Simplex rate of flow controller. These controllers are provided with hydraulic cylinders by means of which the effluent valves may be operated from the operating tables independently of the automatic controlling elements of the effluent controllers proper.
Within the clear well, a float is provided, which actuates a pilot valve which in turn supplies water to the hydraulic cylinders of all effluent controllers in operation, and in the event of the water level in the clear well rising to a predetermined point, all the filters will thus be made to automatically shut off, and when the water recedes in the clear well, the controllers will automatically open and the filters continue in service.
Wash water for filters is supplied by means of a steam turbine operated centrifugal pump, located in the high service pump room, which supplies wash water during washing of the filters at a rate of about 14 gallons per square foot of filtering area per minute. An auxiliary connection has also been installed from the high service pump discharge line to the wash water main by means of which filters can be washed directly from city pressure in event of the wash water pump being out of service. On this connection a pressure reducing valve has been installed in order to reduce the pressure from the high service line to a point suitable for wash water applications to the filters.
Automatic Chlorinators Installed in Duplicate
Wallace & Tiernan chlorinators of the automatic type have been installed in duplicate. The rate of application of the chlorine is automatically controlled by means of floats actuated by columns of water corresponding with the differential head produced in the Venturi Tube constructed in the bottom of the clear water basin.
Sedimentation basins are provided with drain pipes and vales to permit of the ready cleansing of these basins and the removal of sludge.
Provisions for applying chemicals and chemical storage are made on the second floor of the low lift pump house. A hydraulic plunger elevator has also been furnished for conveying the chemical supplies to the storage room. A portion of the second floor of the low lift pump room has been partitioned off for use as a laboratory.
There are within the limits of the city of Chester about 70 miles of pipe lines, ranging in size from 2 inches up to 30 inches. The total distribution system of the Company, including the lines in outlying communities, comprises about 111 miles. Under prevailing prices for pipe and labor, these lines could not be duplicated for less than 3 1/2 million dollars.
At the present time pressures in the city average about 60 lbs. When the system is changed to a direct pumping basis, the pressures will be increased on the average from 10 to 15 lbs.
There are 262 fire hydrants in service within the city limits, and 331 on the entire distribution system. The spacing of fire hydrants is much greater than is permitted in many cities, and is not in accordance with good practice.
Services All Metered
All services of the Water Company are metered. There are no flat rate services, excepting city fire hydrants. The change from flat rate to metered service was completed in 1915, and the entire expense of this installation was borne by the Water Company. At the present time the total investment of the Company in water meters is about $230,000.
The Chester plant is operated under the direct supervision of Mr. R. B. Campion, superintendent, and Mr. Perkins Boyton, chemist, is in charge of the filter plant.
Besides the New Chester Water Company at Chester, Pa., the same interests control and operate the Delaware Water Supply Company, Delaware; the Green Castle Water Works, Green Castle, Ind., and the Vincennes Water Supply Company, Vincennes, Ind. The executive committee is composed of William P. Gest; H. Ashton Little; Jay B. Lippincott; H. Boardman Hopper; Walter Godley, Treasurer; M. G. Mitch, Secretary, and Isaac S. Walker, General Manager.