The treatment and utilization of sewage.

  • Corfield, W. H. (William Henry), 1843-1903.
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: The treatment and utilization of sewage. Source: Wellcome Collection.

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

    526/552 (page 490)
    Drying of the sludge. Value of the manure. Lime and black-ash waste. Its anti- septic properties. Improve- ment in the Lee. passed through a drying cylinder—a granular manure being produced, containing about 30 per cent of moisture. This manure is said to lose by air-drying more moisture, and is usually sold with from 14 to 18 per cent of moisture in it. In this condition it is stated to contain from 3 to 4 per cent of ammonia, and about 5 per cent of phosphoric acid, reckoned as tricalcic phosphate of lime, and sells for £3 :10s. per ton. Estimating the ammonia at 7d. per lb. and the phosphoric acid at 4d. per lb., the theoretical value of this manure would be about £4 per ton. We admit, with the Eoyal Commission on Metropolitan Sewage Discharge, that we completely fail to understand how mere dried sewage-sludge can contain so large a percentage of ammonia, and have so high a value. At Tottenham HiUe's process, and at Leyton the Coventry process, have been recently discontinued—the sewage of both places being now treated by lime and black- ash waste (Hanson's process). The black-ash waste, in its crude state the refuse of alkali works, is prepared by Mr. Hanson and sold by him in London in a granular condition, suitable for mixing with sewage, at £3 :10s. per ton. It is stated by Mr. W. C. Young, consulting chemist to the Lee Conservancy Board, to contain 9 per cent of hyposulphite and 23 per cent of sulphite of lime, which, owing to their being powerful reducing or deoxidising agents, impart to the waste considerable antiseptic and deodorising properties. They are not present in new black-ash waste, but are formed in the heaps of this material which have been long exposed to the air, by the oxidation of sulphide of calcium. The hyposiilphite of lime being soluble in water, some of it passes off in the effluent. The beneficial effect of the intro- duction of the hyposulphite with the sewage effluent into the river Lee has been very marked. During 1885 the Lee was in a most filthy condition—chiefly due to the discharge into it of the effluent from the Tottenham sewage—and gave rise to a great popular outcry. In 1886, after the black- ash waste process had replaced Hill^'s, the river was found to have very much improved, and this improvement is