Sewerage and Sewage Disposal / by Henry Robinson.

Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: Sewerage and Sewage Disposal / by Henry Robinson. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    sewer when the level of the sewage reaches a certain height, or when the sewage shoots over a weir after a certain velocity has been attained. These prevent the sewer from getting under pressure, when the house drains become gorged. In calculating the size of a sewer the volume that has to be dealt with in a limited time governs the whole matter. One inch of rainfall an hour would represent 3630 cubic feet per acre of surface per hour. This quantity, how- ever, flows off the whole area at different rates according to the condition of the surfaces, and the possibility of a sewer having to receive the maxi- mum rainfall, is confined to small areas, the calcula- tions for which would apply to tributary sewers and not to outfalls. The Royal Commission on Metropolitan Sewage Discharge reported in 1884 that 75,251 acres repre- sented the area sewered, the population on which was 2,656,000, the number varying from 7*3 to 253 per acre, and the volume varying from o' 04 cubic feet per acre per minute to 0*83, the average maxi- mum being * 14 cubic feet per acre per minute. It has been estimated that there are on an average 1800 people per mile of sewer in London. At Berlin, the population density varies from 220 to 25 per acre. The smaller figures of course apply to suburban parts. The Lower Thames Valley Main Drainage Board was constituted on the basis of the several districts contributing 250 gallons per day per