Chautauqua’s Sewage Disposal.
Desirous of proving its enterprise and advancement in practice as well as in theory, Chautauqua, N. Y., famous throughout the literary circles of the world, determined late in 1892 to establish a thorough system of sewerage and sewage disposal. Among the many plans submitted in response to widely circulated proposals that furnished by Engineer W. B. Landreth of Jamestown, N. Y., was accepted as being in every way adapted to the requirements of the place. The plan consisted of a machine house and four masonry tanks. Work was begun April 1, 1893, under supervision of Thomas McKenzie, resident engineer.
The machine house is a wooden building 40 x 40 feet. The sewage enters the building on the west side, the brick underpinning of the building forming one side of the brick channel. A screen made of iron bars, set sloping in the channel threefourths of an inch apart, catches all the heavier particles which are raked off and disposed of by burning in the boiler. The chemical mixers are two large wooden vats, fitted with revolving arms, holding 850 gallons of solution, made by the Bonnot Company of Canton, O. The first tank contains a milk of lime solution, which is applied to the sewage as it passes through the brick channel. The second tank holds the sulphate of alumina which is also applied to the sewage as it passes along through the channel. After receiving the application of chemicals in the proper proportions, the sewage enters a brick mixing well where it is caught up by a vertical centrifugal pump, and discharged again into the main channel to the tanks through a four inch discharge pipe. In this way the chemicals are thoroughly mixed with the sewage. The tanks are built of stone masonry laid solid throughout in American cement mortar, and lined on the inside with one course of brick laid in Portland cement mortar. The two end walls are five feet across on the bottom and four feet on the top. A brick channel two feet wide on the west wall carries the sewage into any of the four tanks, through weirs, six feet long. A channel of like dimensions in the east wall discharges the effluent over steps into a fifteen inch sewer pipe emptying into the lake. The side walls are three feet on the bottom and two feet wide on top. The partition walls are two inches larger. The tops of the walls are covered with sawed sandstone coping, three inches thick bedded in Portland cement mortar. The bottom of the tanks is built of concrete, composed of two parts sand, one part cement, and three parts broken stone or gravel, twelve inches thick. The bottoms of the tanks slope from the sides with a fall of one in thirty, to a sludge channel in the middle of the tanks, two feet wide, which has a fall of two and one-half feet in fifty-six, to the sludge drain.
In each tank there is an eight-inch floating outlet pipe, made of galvanized iron eight feet long, which is held suspended just under the surface of the water by a galvanized iron float. This floating outlet pipe is connected with the fifteen-inch effluent drain under the end wall.
When it becomes necessary to clean any one of the tanks, it is shut ofl by means of the flash board, and after a period of rest, for allowing all of the suspended matter to precipitate, the valve on the floating outlet is opened and the effluent drawn off down to the sludge. The effluent valve is then closed and the sludge valve at the other end of the tanks opened, and the sludge passes into the sludge well through an eight-inch vitrified sewer pipe. The sludge well is built of brick, eight feet in diameter, sixteen feet deep, with twelve-inch “walls, fitted with a cast-iron cover, flush with the machine house floor. After drawing all the sludge from the tank into the well, it is then punq ed with a No. 4 Baldwinsville centrifugal pump, up into a tank on the machine house floor ; from this tank the sludge is pumped into the press with a hydraulic pressure pump, fiUed with a double set of plungers, and rubber valves resting on a cast-iron seat. The valves are fastened with arches and are easily accessible in case they become clogged by waste or other fibrous material. The press is a sixty cell Bonnot press fitted with pressure gauge, rubber gaskets, etc. The sludge is pumped into the press until the gauge shows a pressure of sixty pounds and the water ceases to flow out of the drip cocks. The press is then opened, a car run under the press, and the sludge removed out of the building. The cakes are thirty inches in diameter and one and one-half inches thick. When first taken out of the press the average weight is twenty one pounds: after being thoroughly dried, the average weight is twelve pounds, showing forty-three per cent of water still remaining after pressing. The press, car, pump, chemical mixers, shafting and pulleys were furnished by the Bonnot Company of Canton, O., and the work of erecting and fitting up of the machinery was done by the same company.
Experiments as to the best method, and the amount of chemicals necessary to run the works, were made by Mr. Landreth and Mr. McKenzie. Measurements were also taken of the flow of sewage. The intermittent plan was tried, but the effluent was not as good, and the extra amount of labor in filling, emptying and cleaning the tanks by the intermittent plan made it impracticable. The continuous plan, allowing the sewage to flow from one tank into the other, the effluent flowing from the last tank down ever the steps into the effluent pipe to the lake, was found to give the best results.
By carefully watching the effluent and regulating the amount of chemicals until a good effluent was produced, the amount of chemicals used was found to be eighteen grains lime, six grains alum and about one-half a grain of copperas per gallon of sewage. A sample of the effluent was sent to Prof. Maurice Perkins, member of the New York State Board of Health, professor of chemistry in Union College, Schenectady, N. Y., for analysis. He says in his report: “I think this is quite a successful treatment of sewage. Most all of the albuminoid ammonia seems to have been precipitated, for originally I would expect to find at least ten times as much, and you see there is not quite one third. I should have no hesitation in allowing an effluent like this to flow into a large body of water. Would have no fear as to the fish.”
This effluent was sent to Mr. Perkins during the early attempts at purification of the sewage. Since these experiments have been made, experience in the management of the works and careful measurements of the flow of sewage combine to produce better results, and no doubt an analysis now would show even a purer effluent than the one sent Mr. Perkins, July 15, 1893.
It was estimated that there were on the grounds at Chautauqua about 4000 people. An average of two presses of sludge per day has been taken out since July 15. The whole operation of emptying, cleaning the tank and pressing the sludge occupies about five hours. Two men, an engineer and assistant, are employed at the works through the day, from 7 A. M. to 6 p. M. A third man then comes on and runs the works until midnight, when the flow of sewage ceases and the clear water is allowed to run through the brick channel in the building around the tanks in an open channel to the outlet pipes into the lake. The entire cost of running the plant averages ten dollars per day.