View report page

169
F.I.C., and Professor H. R. Kenwood, C.M.G., M.B., C.M., L.R.C.P., D.P.H., was
therefore sought. Their advice endorsed that submitted by the Council's technical
officers. The estimated cost of the installation of plant capable of treating from
5 to 10 million gallons a day is £250,000, and the Council approved an estimate
of this amount for the purpose. Such a plant can only be regarded as the first
unit and the ultimate extent to which it may be necessary to instal plant at one or
both outfalls in order to secure an effluent which may be regarded as sufficiently
satisfactory for discharge into a tidal river such as the river Thames is a matter
upon which no expression of opinion can be given at present. Extreme caution is
advocated, and the gradual building up, or otherwise, in the light of experience
gained in the thorough testing of preceding units of plant In these circumstances
the installation of a first unit of plant at the Northern outfall must be regarded as
experimental.
In the meantime work on the experimental plant installed at the Southern
outfall is being continued and the Council has authorised arrangements for research
into the composition of sludge sent to sea. The water content of the sludge is on
the average 93 per cent., and reductions in this respect would be a matter of considerable
economy.
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 £852.
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 of
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 1928 amounted to £290 6s. 2d.
Deposit of
sludge at sea.
The re-organisation of the Council s fleet of sludge vessels has been completed
and the fleet now 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 J. H. Hunter
became due for her first quadrennial survey by Lloyd's and the work entailed was
carried out at a cost of £1,990. The John Perring and the Bazalgette underwent
annual overhauls at a total cost of £1,230.
Sludge
vessels
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 instal 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.
Northern
outfall.
The removal of hard deposit in the lower sludge store entailed an expenditure
of £500 in the year and the new pumping arrangements, when completed, should
prevent such accumulations in future.
Works have been undertaken at a cost of £288 to prevent the flooding of the
river water tanks by sub-soil water.
The construction of two overhead sludge tanks at the Southern outfall, each
capable of holding 1,500 tons, similar to those erected at the Northern outfall,
has been continued during the year. In addition to the tenders set out in the report
for the year 1927 for various parts of the work the undermentioned tenders were
accepted in 1928 Davy Brothers, Limited, Sheffield, for the supply and erection
of two weir penstocks, £800, and the Sheepbridge Coal and Iron Company, Limited,
Chesterfield, for the erection of cast-iron pipes and valves, £931 5s. Alterations
Southern
outfall.