Sewage utilisation / edited by James Forrest.

Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Sewage utilisation / edited by James Forrest. Source: Wellcome Collection.

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    That is, the theoretical annual value of the feces, and that portion of the urine voided with the feces, of an average population amounts to a little over 2s. 6d. per head, while the average value of the whole of the excreta has been variously estimated at from 8s. to 10s. per head per annum. General Scott, C.B., Assoc. Inst. C.E., who has devoted great atten- tion to the production of manures from dry sewage, has recently demonstrated that from the liquid and solid dejections collected on the pail system it is possible to prepare, at a reasonable profit, concentrated manures containing from 5 to 6 per cent, of ammonia and from 8 to 10 per cent, of phosphoric acid, and which would there- fore command a market value of from £7 to £8 per ton, and upwards. Manures of this class are sold at prices approximating to their theoretical value, i.e., their value as indicated by chemical analysis; while feeble manures, such as those prepared from sewage sludge and the contents of ordinary ash-pits and middens, rarely fetch more than from one-fourth to one-tenth of their theoretical value. It would take about 10 tons of pail sewage to produce 1 ton of the above-described concentrated manure, or each ton of such manure would be the annual produce of sixty-two average individuals. As will readily be understood, when the excreta are largely mixed with earth, charcoal, or ashes, which give weight and bulk without value, the possibility of producing high-class manures becomes out of the question. Here is at once the reason why all the poor manures, made from mixtures of excrement with what have been termed “ profligate associates,” are sold with difficulty, and rarely fetch more than a few shillings per ton. Efforts to obtain more concentrated mixtures have from time to time been attended with fair success. The Author has lately inspected the Paris Municipal Works at Bondy, where sulphate of ammonia is being- made from the liquid contents of the fosses mobiles at a small profit. Urine collected separately was some few years back profitably treated at Glasgow for the extraction of carbonate of ammonia; and only last year a company at West Bromwich succeeded in producing a concentrated manure, by boiling down the mixed pail contents to dryness, which commanded £7 10s. per ton. The works had, however, to be abandoned on the score of creating a nuisance. The conclusions formed by the Author upon dry-sewage pro- cesses are:— 1. That in towns where, for local reasons, a water-carriage system for the removal of the excreta is impracticable, it is