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39
The measurements made during 1953 again showed variations in different localities
of the County due to factors such as local sources of pollution ; there was also a well
marked contrast between urban and rural conditions. Seasonal fluctuations were clearly
evident during the cycle of months, the generally higher level of pollution found in
winter months being due to the combined effect of increased coal consumption and the
occurrence of meteorological conditions unfavourable to dispersal of particles and gases
emitted from chimneys. The rainfall in 1953 was appreciably below the annual average
and this tended to render the air pollution deposit, as measured by the deposit gauge,
rather less than in recent years. A slight increase in the average amount of sulphur
gases present in the air was attributable to the same cause.
By a standing agreement with the Ministries concerned, the Chemist-in-Chief
accompanied the Chief Alkali Inspector of the Ministry of Housing and Local Government
on visits of inspection to test the efficiency of the flue gas washing plants at
Battersea and Bankside Power Stations.
In October, 1953, the Chemist-in-Chief gave a Chadwick Lecture on ' Air
Pollution ' at the Royal Society of Arts. He was also appointed to be a member of the
Government Committee set up, under the Chairmanship of Sir Hugh Beaver, to report
on the problem of Air Pollution.
Swimming baths and ponds
The Council maintains 15 open-air swimming baths for public use and 20 others,
mostly indoor baths, at schools and institutions. Recommendations on treatment are
given by the Chemical Branch and close collaboration is maintained with the other
departments concerned on all aspects of maintenance, alterations and improvements.
Reports are received of the daily tests made by bath attendants and, in addition, all the
baths are visited at regular intervals for inspection and sampling. In 1953, 437 samples of
water were examined chemically and 523 bacteriologically.
During the bathing season all water used in the public swimming baths is chemically
treated, filtered and chlorinated, the breakpoint system of chlorination being used. This
system ensures that a satisfactory residual of free chlorine is present without causing
inconvenience to bathers, and a sufficiently large dosage can be applied to deal with the
heavy pollution load when the baths receive intensive use. Care is taken to maintain
good clarity in the water and instruments for making clarity measurements have been
provided at the baths. It is of interest to record that full-length visibility under the
surface was sometimes achieved, the maximum length being 300 feet, and the water
then had the deep blue colour which bathers find attractive.
Some of the results established by special investigations made during the year were :
Equalisation of chlorine residual over the bath was obtained by use of the suction
sweeper line at the deep end ; this led to improved bacteriological results.
It was shown that the time necessary to obtain deep-end chlorine residuals,
using only shallow-end inlets, was about one-quarter of the turnover time.
An improvised filtration plant, for small indoor baths, functioned successfully
throughout the year and gave a satisfactory bacteriological condition.
During the winter season, with bathing limited to a few hardy early morning
bathers, turbidity in an untreated open-air bath was reduced by the use of hypochlorite
extracted from bleaching powder.
In September, 1953, a paper by officers of the Chemical Branch and Chief Engineer's
Department was read to the Annual Conference of the National Association of Bath
Superintendents.