View report page

44
the supply of raw materials. For example, on the "vehicle" side, linseed oil has
had to be replaced by materials such as plastics or chlorinated rubber. A failure
of concrete was investigated and attributed to the nature of the aggregate and
its lack of grading. Much attention was paid to the sulphate content of the subsoils
and underground waters of new estates in view of the potential deleterious
effect on ordinary portland cement concrete.
Public Health
Regular chemical analyses and bacteriological examinations were made of the
drinking waters derived from private wells supplying hospitals and institutions ;
all these are chlorinated before use. Assays were made by various methods of the
polluting matter (total deposit, tarry matter, sulphur gases, etc.) in the air in various
parts of London and also, for comparison, at premises outside the county. This
work was done in conjunction with a scheme sponsored by the Department of
Scientific and Industrial Research. This subject (atmospheric pollution) assumed
importance in view of the proposals for erecting new electricity generating stations
which would involve the consumption of large quantities of coal; the question,
therefore arose as to the desirability of flue gas washing to prevent access of sulphur
gases to the air. The air in the Council's vehicular tunnels was examined in order
to ensure safe conditions from the health aspect as regards the carbon monoxide
and lead contents derived from motor exhaust fumes (the lead coming from leaded
petrol).
Main
Drainage
The laboratories at the two outfall works are wholly concerned with work
for the main drainage service, and some is also done at the central laboratory. The
sewage of London north of the River Thames is treated at the Northern Outfall
Works by sedimentation, and a portion of it subsequently by the activated sludge
process. That from south London is submitted at the Southern Outfall Works to
sedimentation only. In both cases the sedimented matter (sludge) is taken out
to the estuary in ships and dumped ; the effluent is discharged into the river at the
outfalls. After being out of operation during the war years the activated sludge
plant was re-started in 1946, and a stock of activated sludge having been conserved,
smooth building-up of treatment was effected. The effluents from the outfall
works are discharged into the River Thames, and natural oxidation by the dissolved
oxygen in the water is the final process in their purification. A careful watch was
therefore kept on the condition of the water of the river by regular sampling and
analysis at many points between Teddington weir and the estuary. The sludge
digestion plant at the Northern Outfall Works functioned satisfactorily, the
temperature of operation being 85° F. ; the sludge gas produced (containing about
70 per cent, methane) was used for power production. Work on the composting
of sewage products was continued and large quantities of compost for use on Council
farms were made from household refuse and sludge screenings. Advice was given
as required as to the nature of industrial discharges into sewers, particularly in regard
to their compliance with the requirements of the Public Health (London) Act, 1936,
and batches of safety lamps for use in the sewers were tested.
Public
Control
The work of the chemical branch for the public control service is mainly to
comply with various Acts of Parliament. The Fertilisers and Feeding Stuffs Act,
(1926), under which the Chemist-in-Chief is the official agricultural analyst for the
county, was designed to prevent fraud in connection with the sale of these materials,
and statutory statements of essential ingredients have to be made; samples are
examined to ascertain compliance with these statements. The Petroleum
Consolidation Act (1928), London County Council (Celluloid) Act, and the London
Building Act (1930) regulate the storage and use of inflammable materials samples
of which were tested as to compliance with the various requirements. Firms
operating certain dry-cleaning processes work under licence ; plants were examined
and samples of the atmosphere in them analysed to ascertain whether the conditions
of the licence were being fulfilled.