New England Waterworks Meeting.
As announced in the previous issue of FIRE AND WATER ENGINEERING, the New England Water Works Association held its December meeting in Boston on the 14th ult., President King occupying the chair. The principal paper of the meeting was on the “Mechanical Filtration Plant of Newport, R. I.,” by K. E. Milligan, manager of the New York Continental-Jeweli Filtration Company. This plant, which is of reinforced concrete construction, was placed in operation last May. The design provides for considerable elasticity in operation, including sedimentation with or without coagulation, separate coagulation within the basin provided, sterilization by hypochlorite solution before or after filtration, and aeration, all in conjunction with mechanical filtration proper. The plant consists essentially of two settling basins arranged to operate as one under normal conditions, a distinct coagulating basin through which the settled water must pass to the filters, six 1,000,000-gallon Continental filters, and a clear-water well below them. The new structure is joined to the pumping station by a covered passage and machinery room. The settling basins are arranged around three sides of the coagulating basin and all occupy a space about 135×70 feet, the coagulating space being 84×25 feet. The settling basins are 10 feet deep, and the coagulating basin is 10 feet in depth. Gravity feeds are provided for the solutions used in the purification process. Four concrete storage lanks are provided above the settling basin for the sulphate of alumina and the hypochlorite of lime solutions. The low-service pumps supplying the filters draw water from a receiving basin near the plant, which is connected with the more distant sources of supply. From the standpoint of filtration, Newport water is difficult to handle on account of its high color. All of it is low in alkalinity, and algae growths at times prevail. The report of the State Board of Health for July, 1910, stales that many micro-organisms were present The capacity of the sedimentation basin is 750,000 gallons, or three hours’ continuous subsidence at the normal filtering value of 6,000,000 gallon in twenty-four hours. In addition, the capacity of the coagulating basin is 250,000 gallon, or a period of one hour’s coagulation, giving a total capacity for subsidence of 1,000,000 gallons, or a period of four hours from the time the water enters the settling basin until it reaches the influent flume to the filters. In the low-service machinery room are located two 6,000,000-gallon centrifugal pumps, each direct connected to vertical Sturtevant engines. These pumps supply the sedimentation basins with water to be pmifield, pumping first to two large aerating devices, one on either side of the two settling basins, and superimposed above them and partly supported on the filter deck. In ibis room are also located a blower, furnishing air to assist in washing the fillers, and two cast-iron float tanks, with levers operating balanced valves on the steam supply to the engines, and these float tanks are connected with the water level in the coagulating basin so that the pumps increase or diminish the supply automatically. A testing table is also located here. At times considerable odor exists in the raw supply, rendering a very thorough aeration necessary before it passes to the filters. The aerating device consists of two large concrete boxes, with sides converging to a common renter. On the sides rest cast-irhn sections about 2 feet square, which are so ridged that when bolted together, covering the entire surface, the whole presents a series of channels abutting one against the other and forcing the incoming water to take a tortuous tangential direction, forming a multiplicity of miniature waterfalls, over which the water passes to a channel at the bottom of the converging slabs, thoroughly aerated, and without further cost than an extra lift of about 4 feet implies. The collecting channel then permits the water to pass mto the settling basins, ami eventually to and through the filters, passing through Weston controllers located in the pipe gallery, and finally to the clear-water well under the filter house, whence high-service pumping equipment delivers it to the consumer. Storage and mixing tanks with agitators are arranged in n gallery elevated above tile main floor, while on the floor are located the orifice and regulating device for feeding the coagulant and hypochlorite solutions. The filter house proper opens into the coagulant tower just above the end wall of the congulating basin. The upper portion contains two hypochlorite of lime tanks and two sulphate of alumina tanks of reinforced concrete, all being 7x7x5 feet inside. The sulphate is lifted by a Imist and bucket in measured quantity and laid upon racks, water being sprayed upon it until dissolved. When the tank is filled to a predetermined point the water is automatically shut off, and the stored solution, of 2 per cent, strength, is ready for use. This solution is kept in motion by agitators, and it is led from a porcelain-lined cast-iron orifice box in measured quantity into the raw water at two points, if required, viz., the suction of the centrifugal pumps and the influent flume of the coagulating basin. While the hypochlorite solution is also used and stored as a 2 per cent solution and fed through similar orifice feed boxes, the handling of the salt itself is somewhat different in order to pass it into the storage tank with the least exposure. Superimposed above the concrete storage tanks are two cast-iron porcelain-lined mixing tanks, with tight covers, equipped with agitators, which revolve at a faster rate than those used in the storage tanks. The hypochlorite is placed in these mixing tanks and thoroughly agitated with a small stream of water passing through the storage tank, which fills to the point required. The hypo is thus kept in a chyle-like condition, gradually weakening in the mixer and passing to the storage tank, where the slower moving agitator keeps it thoroughly mixed Little odor is noted in this process, the mixing occurring once a day. Preliminary operalien of the plant showed that the introduction of the hypo had no apparent effect, even when quantities large enough to convey a distinct odor of chlorine to the filtered water were used. No reduction of bacteria or color was apparent and no appreciable elimination of algae was noted. When coagulation with sulphate of alumina was effected as the water entered the settling basin, and the coagulated water filtered in the usual manner, the hypo solution being fed in minute quantities at the point in the clear-water well at the sump or high-service suction, the desired result was attained, and practically sterile water, clear and bright, was pumped to the consumer. In November of the present year one grain per gallon of sulphate of alumina was fed to the discharge of the low-service centrifulgal pumps, .5 part per million of hypochlorite of lime being applied at the sump or outlet of the clear-water well. The capacity of the latter is 116,000 gallons.
L. A. Rourke, street commissioner of Boston, gave a very interesting illustrated address on the construction work of the Panama canal. This was followed by a paper prepared by Dr. G. T. Swarts, secretary of the Rhode Island Board of Health, entitled “Purification Difficulties.”