Specification of Henry Young Darracott Scott : treating sewage water.

  • Scott, H. Y. D.
Date:
1872
Catalogue details

Licence: Public Domain Mark

Credit: Specification of Henry Young Darracott Scott : treating sewage water. Source: Wellcome Collection.

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    5 _Scott’s Improvements in Treating Sewage Water. extract the ammonia. With waste waters comparatively free from suspended matter the process of removing the ammonia may be applied at once. The chief object of the precipitation, so far as my present object is 5 concerned, is to avoid burthening valuable products to be obtained with the comparatively worthless substances which would otherwise be thrown down with them. The effluent from tank No. 1 will probably carry away with it in solution notable quantities of lime or lime salts which it is very desirable 10 but not essential to remove in tank No. 2, by the addition to it of super¬ phosphate of magnesia, superphosphate of lime, phosphate of soda, or phospheric acid, which will precipitate it as insoluble phosphate. These substances may be used singly or in conjunction, but I prefer to employ superphosphate of magnesia. The deposit thus formed may be collected 15 and dried for manure, or it may be subject to distillation, and be con¬ verted into charcoal which will be useful for many purposes. The carbon is of course supplied by the organic matter which the precipitate carries down with it in settling. Appreciable quantities of ammonia will also be found in this deposit. The lime carried away in solution from tank 20 No. 1 may be partially removed also by filtration through charcoal, burnt ballast, or other suitable substance. The effluent from tank No. 2 thus freed from lime passes on to tank No. 3, where, and in tank No. 3a, the operation for the extraction of the ammonia is to be carried out by extracting it with phosphate of mag- 25 nesia, with which it enters into combination readily. This salt is well known to be very insoluble in weak ammoniacal solutions, and the idea of taking advantage of this property for the extraction of ammonia from them is not new. Various attempts have been made to effect the object by bringing together in the ammoniacal liquid to be treated phosphoric SO acid and magnesia in the form of soluble salts of those substances, in the hope that the ammoniacal phosphate of magnesia would be precipitated ; but all such attempts have proved failures for reasons well known to chemists. When forming this salt for purposes of analysis, chemists invariably allow the liquid to stand for several hours after concentrating 35 the solution operated upon by evaporation, as the salt, notwithstanding its insolubility in weak ammoniacal solutions, has the peculiarity of precipitating very slowly. The conditions of concentration and long standing are of course impracticable with sewage and other polluted water