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188
reservoirs, and of the deodorization of the sewage, now partially
in operation, to which the Council no doubt will give a fair trial,
although the defunct Board is exclusively responsible for the
experiment; an experiment on a vast scale, made, it may be
repeated, in defiance of the recommendations of the Royal Commission,
generally opposed by scientific chemists, and condemned
by their own chosen adviser, Sir Henry Roscoe himself.
It may be added that during the summer of 1889—
from 23rd May to 12th October—1313 tons of manganate of
soda, and 391 tons of sulphuric acid, were used at the Barking
Outfall for disinfecting the effluent before discharge into the
river: at Crossness, the tanks not having been completed,
1686 tons of manganate and 664 tons of acid were applied
to the crude sewage; and at the Storm Overflows, 187 tons
of manganate and 40 tons of acid were used. The total
quantity of manganate was 3197 tons, and of acid 1096 ton3,
at a cost of £25,305 ; these chemicals being used during the
hot weather only. This outlay is independent of that for lime
and sulphate of iron, used for precipitating the sewage at
the Barking Outfall Works; the quantities estimated by the
chemist beiDg, lime 9125 tons, sulphate of iron 2190 tons, for the
year, costing some £10,700, so that the total outlay on chemicals
during the year was, in round figures, £36,000. The precipitated
sludge, it may be mentioned, is taken to the Nore, at a
cost of about fourpence a ton; two ships working night and
day, and a third being required.
From what has gone before, it will be apparent that the best
authorities are unanimous in the view that the sewage, crude or
after precipitation, must ultimately be taken to the land. At
Paris it is stated that 5000 gallons, on an average, are applied
to the acre. At this rate 30,000 acres would be required for
irrigation purposes, were all the sewage of London, averaging
150 million gallons daily, disposed of in this manner. A larger
proportion of a partially purified effluent, presumably, might be