SEWAGE DISPOSAL AT COLUMBUS.
Columbus, Ohio, at a conservative estimate has a population of about 142,000—possibly $150,000. It has 167.33 miles of public sewers, varying from ten and one-half feet to eight inches in diameter, the cost of which has been $3,036,834. These sewers are mainly on the combined system and the drainage is into the streams. There arc twenty-two sewers draining into the Scioto and Olentangy rivers between the north and south corporation lines. These, however, are all intercepted by an intercepting sewer, constructed in 1892, at a cost of $430,669.49. which varies in diameter from two to six and one-half feet. In November, 1903, the people voted $1,200,000 bonds for the purpose of sanitary sewage disposal, and under this authorisation the council, by recommendation of the hoard of public service, voted an appropriation of $J6.OOO for experimental work, to determine the best method of sewage purification under Columbus conditions. This preliminary work began about one year ago, and has just been completed. They plan for the purification of a nominal flow of 20,000.000 gallons a dav and propose septic tanks followed by sprinkling filters. The septic tanks will be twelve feet in depth, uncovered, and will have a capacity of about 8,000,000 gallons. The sprinkling filters will he about ten acres in area of broken stone, five feet in depth, laid on hollow free draining bottoms, with sprinkling nozzles fifteen feet between centres, designed under a five-foot head to spray the septic sewage over the surface of the broken stone, at a net rate of 2,000.000 gallons per acre per day. The effluent from these filters will be collected in settling basins, with a capacity of 4,000,000 gallons, and our experiments show that a non-nutrescible effluent can thus lie obtained. * * * The preliminary work consists of the sewage pumping station to pump the sewage of the city to the sewage purification works, and. in times of flood in the Scioto river, to pump the storm water to the full extent of its capacity. 41.000,000 gallons per day, from the low-lving area of the Scioto river. The machinery of the sewage pumping station will consist of three rt.ooo,000 gallon and two 4.000,000 gallon centrifugal pumps. The station complete, including the screen-cages, machinery and buildings, will cost about $136,000. * * * It has been necessary to extend the intercepting sewer by a forty-eight inch cast iron pipe under the river to the pumping station, and construct a force-main of the same dimensions one mile and one-quarter iu length to the purifying works. A ten-inch water main from the distribution system of the citv has also been extended to the purification works, parallel with the force-main above noted. Contracts for the preliminary work for comoletion during 1905 amounted to $460.000: and include the pumping station, with its machinery, screens, gates, valves, the force-main, water main, ditches, levees, culverts, railroad bridge, track and embankments, for supplying coal, to which should he added $06,52 “t for 222 acres of land for the disposal works. T11 addition, the plans require two pumping stations on the Alum crock sewer in the eastern portion of the citv. to raise the sewage to the ridge east of the Scioto river, whence it will flow hr gravity to the main sewage pumping station. The first station will he located half-way tin the slope, designed to pump about forty-five per cent of the drv flow: the one farther east, at the foot of the hill, designed to pump five per cent: while the remain ing fiftv per cent—1,000.000 gallons per day—will he conducted bv gravity through the central relief sewer soon to be completed.