View report page

25
reasons for this are probably three-fold, for in the first place, the supply of these
materials has now increased to such an extent that it can meet the demand and
competition is again developing; secondly, new and allegedly improved materials
are frequently being produced, the claims for which must be investigated; and
thirdly, it must be remembered that from the economic aspect, if a paint fails in
use, it is not only the cost of the material which is lost but also the cost of the labour
of application which may be about five or six times that of the paint itself. Many
samples of paint were reported as being unsatisfactory, some of the reasons being,
for example, (a) the inclusion of white lead and lithopone in the same pigment,
(b) the use of lithopone in a paint supplied for exterior work, (c) the lack of adhesion
and/or flexibility of the film produced, (d) gritty nature of the finish produced. In
a number of cases of paint failures, the work was inspected and the cause of the
failure diagnosed after the subsequent examination of samples in the laboratory.
Only a few of the other matters dealt with in connection with housing can be listed
shortly, e.g. (a) the decay of wood flooring due to worm attack which started long
before the subsequent growth of dry rot fungus; (6) examination of new types of
wood preservatives ; (c) devising of an impact test for determining the strength of
asbestos composition panels ; (d) investigations as to the failures of plasters; (e) the
possible corrosion of Portland cement concretes by sulphates in soil or ground waters,
and the alternative use of high alumina cement where necessary. Amongst the other
building materials examined may be mentioned Portland and high alumina cements,
bricks, mortars, asphalts and asphalt road surfacing, clinkers, synthetic building
blocks, tiles, synthetic flooring and roofing materials, putty, waterproofers, etc.
The sewage from London north of the River Thames is treated at the Northern
Outfall Works, Beckton, by sedimentation, and about one-third of the flow, subsequently,
by the activated sludge process. That from London south of the Thames
is subjected at the Southern Outfall Works, Crossness, to sedimentation only. In
both cases most of the sedimented matter (sludge) is taken out into the estuary in
ships and dumped ; the effluent is discharged into the river at the outfalls. Work
on the composting of sewage products with pulverised household refuse was continued
in 1948 and large quantities of such compost were made from sludge screenings.
The sludge digestion plant at the Northern Outfall Works dealt with a small proportion
of the sludge, and the sludge gas produced (containing about 70% methane)
was used for power production. The final effluents from the Outfall Works are
discharged into the River Thames and biochemical oxidation by the dissolved
oxygen in the water is the final process in their purification. The condition of the
water of the river is therefore of great importance and a careful watch is kept upon
it by regular weekly sampling and analysis at many points between Teddington
Weir and the sludge dumping area in the estuary.
The laboratories at the two outfall works carried out the chemical analyses
necessary for the control of the various plants during the year : some research work
was also done on several aspects of the sewage disposal problem and as the result
of some of this a provisional patent was taken out by the Council at the end of the
year for a new process for dewatering sludge.
The question of trade discharges into sewers was investigated in a number of
cases as to compliance with the appropriate clauses of the Public Health (London)
Act, 1936.
In view of the decision of the Council in 1947 to construct extensive additions
to the existing sewage treatment plants the Chemist-in-Chief, with the Divisional
Engineer (Main Drainage), Chief Engineer's Department, visited the United States
of America in the early summer of 1948 to study the latest practice in regard to
sewage disposal in that country. The visit was facilitated by the generosity of the
Rockfeller Foundation which made a travel grant for the purpose, and the United
States Public Health Service was also very helpful in making arrangements for the
Main
drainage