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In 1892, before the Crossness works were completed,
upwards of 50,000,000,000 gallons of sewage were treated at the
outfalls, and more than a million-and-a-half tons of sludge,
precipitated therefrom, was taken out to sea in the
Council's fleet of sewage vessels. Considerable outlay was
incurred for materials for precipitation and deodorisation.
Some 13,850 tons of lime, 3,140 tons of proto-sulphate of
iron, 174 tons of manganate of soda, and a large quantity of
sulphuric acid were used. The summer of 1893 having been
exceptionally hot, the fact that no serious complaints of
offensive smells were made is all the more significant. It is
a significant fact, moreover, that fish are now to be found in
parts of the river, from which, prior to the completion of the
precipitation works, they were absent. It is but just to
mention that the present method of dealing with the sewage
was originated by the late Metropolitan Board of Works, and
was in partial operation during their regime; the gigantic
works for the purpose having been designed and largely
carried out by their engineer.
Sewer Emanations.—Sewer air investigations have
been carried out for some time past, for the County Council,
by Mr. J. Parry Laws, in conjunction with Mr. Dibdin the
Chemist to the Council, which go to show that the microorganisms
of sewer air are almost invariably less in number
than the micro-organisms to be found in fresh air surrounding
the sewer at the same time, in the same vicinity; and the
"important conclusion" deduced from observation is, that
" the micro-organisms of sewer air are derived from the microorganisms
of fresh air and not from the micro-organisms of
sewage." As it is deemed " most desirable to study the
micro-organisms existing in sewage under various conditions,
with a view to classifying them, and determining the relative
frequency with which each different species occurs," and as
it" will be necessary to determine whether some of the