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The incidence of coliform pollution was due to temporary features such as plant breakdown
and was speedily rectified.
During the 1960 winter season 10 of the open air baths were in constant use. These baths
were regularly treated with the supernatant liquid extracted from bleaching powder. The
total number of bathers during the winter season was about 30,000 and it is of interest that
at this level of bathing concentration the treatment used could regularly ensure waters
with clarity of more than 20 feet.
The baths at schools and institutions vary in size from 10,000 to 100,000 gallons. Many
of them are used by other organisations and councils.
The annual lectures to bath superintendents and attendants on swimming bath water
treatment and testing were given by a member of the Branch. These lectures proved most
useful, particularly as an opportunity for discussing possible improvements and problems
which have arisen during the preceding summer season.
The treatment and testing of the water at the 45 paddling pools in the Council's parks
has been standardised and research work has commenced to investigate the possibilities of
improving this treatment by the use of quaternary ammonium compounds.
Ventilation of vehicular tunnels
Weekly tests are made of atmospheric conditions in Blackwall and Rotherhithe tunnels
at times when the tunnels are carrying heavy traffic. This information assists the Chief
Engineer to assess the degree of forced ventilation needed.
More than 1,000 vehicles an hour pass through each tunnel during much of the day.
In periods of congestion vehicles are subjected to frequent braking and acceleration; these
conditions favour an increased output of exhaust pollutants, thus making great demands
upon the ventilation system.
The measurements made during the year showed that, in general, the exhaust gases in
the atmosphere of each tunnel were diluted to a tolerable level in respect of toxic components.
The amount of black suspended matter, for which there is no recognised standard, was
unpleasantly high at times in both tunnels. Heavy vehicles of the diesel type, though producing
relatively little carbon monoxide, can be prolific sources of smoke unless properly
maintained and correctly driven. A bad form of driving, which has a particularly marked
effect on the confined atmosphere of a tunnel, is the use of excessive fuel injection instead
of the appropriate gear-change when mounting long upward slopes. Towards the end of
1960 the Minister of Transport stated that he was considering amending the law to
prevent the misuse of the excess fuel device.
Disinfectants
Samples of disinfectants supplied under contract were regularly examined to ensure
conformity with specification in regard to germicidal power, emulsion stability and freedom
from staining action on linen.
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