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137
standing, the Act is not without value and contains powers which,
when the times are less out of joint, may be found useful for
promoting some of the objects it was intended to subserve.
METROPOLITAN MAIN DRAINAGE.
The attention of the Metropolitan Board of Works has been
largely occupied, for some time past, with reference to the disposal
of sewage at the main drainage outfalls; and reports, which
should have considerable interest for all concerned in the sanitary
administration of London and the riverian districts, have been
presented to the Board by its Works and General Purposes
Committee; viz., On the disposal of the sewage of the Metropolis;
and On the treatment of sewage at main drainage outfalls. The
Committee reported, November 27th, that "by chemical precipitation
a good effluent water could be obtained, and that they
were pursuing their enquiries as to the best method of dealing
with the residue or sludge." As the result of long-continued
and practical experiments, conducted by Mr. Dibdin, the chemist
to the Board, to whose aid Dr! Dupre was subsequently called,
the Committee came to the conclusion that "chemical precipitation
of the solid matters held in suspension in the sewage can be
effected by the addition of various reagents, but that no practical
advantage accrues from the addition to the sewage of more
precipitating matters than are really necessary for facilitating
the natural tendency to solid deposit." It was found that the
sewage can be sufficiently clarified by the addition of 3.7 grains
of lime and 1.0 grain of protosulphate of iron (green vitriol) to
each gallon of sewage, and by subsidence in settling tanks during
a period of from one to two hours; the effect being, besides the
removal of the solids, that "the grosser odours of the sewage
are destroyed, and the foul and offensive appearance removed.''
The conclusions arrived at by the Committee, and the chemist
to the Board, were submitted to four eminent chemists, Sir
F. A. Abel, Dr. Odling, Dr. Williamson, and Dr. Dupre, who
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