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Sewage
treatment.
Deposit of
sludge at sea
Sludge
vessel?.
Northern
outfall.
ihe sludge vessels made 804 trips and travelled altogether 187,616 nautical
miles.
The constantly increasing flow of sewage to the main drainaga outfalls has
necessitated in recent years consideration of the question of the possibility of dealing
with the sewage by methods other than those hitherto in operation (see Annual
Report for 1928, pp. 168-169). The estimated cost of the installation of plant
capable of treating from 5 to 10 million gallons a day is £225,000, and the
Council approved an estimate of this amount for the purpose. Progress was
made, during the year with the installation of a first unit of the new plant at
the Northern outfall.
During a part of the month of August it was considered advisable to resort to
treatment of the sewage with chemicals. The total expenditure in this respect
amounted to £3,760.
The solids, known as sludge, which are obtained from the sewage after sedimentation
at the outfalls, are conveyed to, and deposited in, the Black Deep in the
Thames estuary. The Deep is also used by other authorities for the deposit cf
waste materials, and the cost of buoying the deposit area is apportioned among the
various authorities using it for deposit purposes. The Council's proportion for the
year 1929 amounted to £266 7s. 4d.
The Council's fleet of sludge vessels consists of five vessels, namely, the Bazalgette
(commissioned in 1887 and re-conditioned in 1921) of 1,000 tons capacity, and the
Henry Ward (commissioned in 1923), the J. H. Hunter (commissioned in 1924), the
G. W. Humphreys (commissioned in 1925), and the John Perring (commissioned in
1926), each of about 1,500 tons capacity. During the year the G. W. Humphreys
became due for her first quadrennial survey by Lloyd's and the work entailed was
carried out at a cost of £1,755. The John Perring and the Henry Ward underwent
annual overhauls at a total cost of £2,603.
The loading of sludge vessels at the Northern outfall is effected by pumping
direct or by gravitation from the overhead sludge tanks. The pumping engines were
obsolete and uneconomical and, to maintain them in working order, heavy repairs
would have been necessary. The Council therefore decided to install two new
steam engines and direct-coupled centrifugal pumps in the main engine-house.
The total estimated cost of the proposed works is £6,500. It was arranged for the
steam engines and pumps and new penstocks required to be obtained under contracts,
and for the new foundations and sump necessary to be executed by the
direct employment of labour. The work was well advanced during the year.
Arrangements have been made for the reconstruction of part of the jetty at
a cost of £27,005, while repairs to the river walling of Barking Creek have been
carried out by the direct employment of labour at a cost of £150.
The construction of bathrooms at the 12 cottages occupied by workmen at the
outfall and the installation of baths therein with the necessary fittings was authorised
at a cost of £1,008.