UTILISATION OF SEWAGE.
To many large and growing towns, the disposal of the sewage is becoming a serious matter, and while several large towns are just now contemplating the expenditure of very large sums for the purpose of getting rid of it, a Company has been formed, and works have been erected at Shrewsbury with a view to utilising this valuable waste material. The process by which this Company profess to be able, without creating a nuisance, (1) to purify the sewage so that the effluent water is sufficiently pure to be admitted into any river, within the requirements of the Rivers’ Pollutions Prevention Act, and (2) to produce ‘native guano,’ is very simple. As the sewage enters the works, clay, charcoal, and blood are added as deodorisers; and after thorough mixing, a solution of sulphate of alumina is added, by which the dissolved and suspended impurities are quickly precipitated in one or other of the settling tanks, from the fourth of which the water runs without further treatment into the river. Dr Wallace reports that the sewage as it enters the works contains 37.5 per cent. of suspended organic and inorganic matter, but that in the effluent water there were only the merest traces of either. By experiment it has been found that in this water fish will live for months. The deposit is then removed from the tank, and, by means of pressure and artificial heat, is deprived of its moisture, till it obtains the consistency and appearance of dry earth. It is then ready for market, and is in such demand, that as yet the Company are unable to overtake all orders, though seventy shillings per ton is charged.