Specification of Alexander Melville Clark : treating sewage.

  • Clark, Alexander Melville.
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Specification of Alexander Melville Clark : treating sewage. Source: Wellcome Collection.

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    Clark's Improvements in Treating Sewage, 2nd. Alnminate of soda, and afterwards phosphoric acid or an alkaline phosphate, or a soluble phosphate of lime or of magnesia. In this case insoluble phosphates of alumina, lime, or magnesia are formed, which unite with the organic matters in suspension with a part of those which 5 are in solution, and with the coloring matters, whilst there remains in solution an ammoniacal salt and an alkaline phosphate, or it may be a phosphate of ammonia. If to these liquids a soluble salt of magnesia be then added a precipitate of double phosphate of ammonia and magnesia is obtained. 10 3rd. Phosphate of soda and a soluble salt of magnesia, giving pre¬ ference more particularly to the tribasic phosphate of soda, mixed chemically or mechanically with phosphate or oxide of iron. In the latter case it is often of advantage to employ as the soluble salt of magnesia a certain quantity of the acid phosphate of this base. As all 15 these reagents are soluble they are mixed with the water to be purified, either by distributing them in the tanks or reservoirs in which the waters are contained, or by supplying them to the flowing water in quantity proportionate to the volume and the degree of impurity of the latter, after which the precipitates are allowed to subside in tanks and 20 the liquid subsequently drained off, but the separation is much more quickly effected by employing Parrot’s filtering tanks. 4th. When the waters to be treated contain but little ammonia, but are chiefly contaminated by the presence of urea or of organic matters, it is in certain cases advantageous to destroy those impurities by the 25 action of nitrous or hyponitric acids, or of nitrous vapours resulting from certain industrial reactions in which the nitric acid is in part deoxidised, or of soluble nitrites. In some cases this reaction may be employed very efficaciously to complete the purification already effected by the first reagents specified. When I employ at same time a soluble 30 phosphate and a salt of magnesia to produce a precipitate of double phosphate of ammonia and magnesia, which takes up all the ammonia that was in solution in the liquids, it may happen that a part of the double phosphate thus formed remains in solution in the clarified waters (since one part of ammonio-magnesian phosphate dissolves in fifteen 35 thousand parts of water), and to avoid the loss which might result from this solubility, slight though it may be, the liquid may be filtered on dolomite (double carbonate of magnesia and lime) which retains all the phosphate dissolved.