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chlorine is kept as far as possible at two parts per million of
water and the amount of chlorine is tested by the staff at
frequent intervals, that is, about every two hours during the
summer and rather less frequently in the winter. The maintenance
of a regular concentration of chlorine presents some difficulty.
The sudden influx of a large number of bathers on a hot day,
particularly if the bathers are perspiring freely before they
enter the water, can reduce the chlorine content to nil within
a few minutes, whilst increasing the amount of chlorine much
above the usual level in anticipation of large numbers of bathers
can cause some discomfort, particularly a stinging feeling in
the eyes. One cannot always correctly forecast the behaviour of
the public, particularly as the number of bathers can be greatly
altered by variations in our uncertain climate and although
there have, from time to time, been some complaints due to
excess of chlorine in the water, I feel sure that within limits
the freedom of the water from organisms which might carry disease
is of more importance than a possible temporary discomfort.
Samples of water from the swimming baths are taken
regularly for bacteriological examination and also for chemical
analysis. The Colindale Laboratory of the Public Health
Laboratory Service attach the following note to their reports:-
"Swimming-bath water is exposed not only to faecal
contamination but also to contamination with organisms
from the skin and nasopharynx of the bathers. Therefore,
it is recommended that:-
1. No samples from a bath should contain any coliform
organisms in 100ml. of water.
2. In 75% of samples examined the 24 hour plate count
at 37°C. from 1ml. of water should not exceed 10
colonies and the remainder should not exceed 100
colonies.
(From: Report on Public Health & Medical Subjects-No.71
The Bacteriological Examination of Water Supplies-p.19)"
The plate count at the Colindale Laboratory is carried
out for two days which might slightly but not materially increase
the number of colonies found in any sample. It is usual when
taking samples of swimming bath water to take two samples at the
same time from different parts of the bath.
A summary of the reports is as follows:-
A summary of tlie reports is as follows:-