Sewerage Works at Hendon, Eng.
At a recent date the chairman of the Hendon local board opened the new pumping station which had been erected near Cool Oak-lane, to deal with the sewage from what is known as the “Station District,” forming part of the low level area. The latter comprises about 1100 acres. It had become necessary to drain this district in consequence of the complaints made by the Regent’s Canal Company, who own the Brent reservoir at Hendon, into which pollution from the houses in the Station District found its way when the cesspools overflowed. The Thames conservators also complained of the same state of things, the river Brent being a tributary of the Thames. The board accordingly instructed their engineer, S. S. Grimley, A. M. I. C. E., to prepare the recessary drawings, and in June, 1891, the tender of James Dickson, of St. Albans, was accepted for the sewer, which was constructed with Hassall’s double-lined pipes, eighteen inches in diameter, surrounded with Portland cement concrete. The tender of Joseph Mestonof Westminster, was accepted for sewering and making up three roads leading to the outfall sewer, and the tender of Messrs. Crossley brothers of London and Manchester, was accepted for the machinery. The total cost of the works has been 6358l., being well within the engineer’s estimate. The machinery consists of two seven horse-power (nominal) Lrossley’s “Otto” gas engines, with tube ignition, which give about eleven and one-half horse power each upon the brake. Each gas engine drives a set of three-throw plunger pumps eighteen inches in diameter by ten inch stroke, by means of countershafting and belts. Each set of pumps, at thirty revolutions per minute, will throw 350 gallons per minute, or over 500,000gallons in twenty-four hours, into the high-level gravitating sewer through a nine inch rising main about 800 feet long. This sewage flows about one and one half miles through the gravitating sewer to the outfall works, where it is treated on the ferrozonc and polarite process of the International Water and Sewage Purification Company, hast and loose pulleys are provided for each set of pumps and the countershaft is fitted with the necessary clutches, which enable cither gas engine to work either set of pumps or both sets if necessary. Counters are fixed on the pumps to check the quantity of sewage lifted, and access to both suction and delivery valves is obtained by removing one cover to each pump, instead of having access covers to both suction and delivery valves, as usual. Floats are arranged in the pump well to actuate the striking levers, carrying the belts on the fast pulleys, when the sewage collects in the well, and back to the loose ones when the well is empty. Thus the plant may be said to be automatic in its action. The sewage is screened on arriving at the pumping station and then flows into the pump wells, from which it is raised through a nine inch suction pipe to each set of pumps, this pipe being furnished with a suction valve and strainer. The consumption of gas is about twentythree cubic feet per brake horse-power per hour, with a crankshaft speed of about thirty revolutions per minute and an engine speed of about 180 revolutions per minute. The engine house is built with cast-iron columns bolted to the concrete foundations. These are connected with angle and T-iron framing, and covered with eighteen 15. W. G. corrugated iron, so as to be easily removable, as in course of time, and when the vacant land in the station district becomes covered with houses, it will probably be necessary to extend the new outfall sewer to the existing outfall works, and there erect a permanent engine house. The machinery, however, is designed to take the sewage from the whole lew level area, and will only require re-erecting in its ultimate permanent position.