London's Pulse: Medical Officer of Health reports 1848-1972
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Hints from the Health Department. Leaflet from the archive of the Society of Medical Officers of Health. Credit: Wellcome Collection, London
London County Council 1933
[Report of the Medical Officer of Health for London County Council]
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entering the bath tends to pass through it along the shortest path from inlet to outlet.
This has been prevented by providing multiple inlets. Growths and deposits of
eggs of midges on the walls of the baths have given very little trouble, and the
surface of the water has been free from the empty nymph cases, from which
midges had emerged, which are a marked disfigurement of non-filtering baths in
the open air.
The increased clarity of the water is not only of aesthetic value, it prevents the
possibility of bathers who have become unconscious or injured while in the water,
or who have sunk, escaping attention and drowning, as has happened in swimming
baths. This is an important matter in any bath, but more especially so in baths as
much used as those in the Council's parks are, especially in hot weather and school
holidays.
The soluble impurities entering the water are obviously not removed by filtration,
but their amount cannot be increased by auto-digestion of those which are
insoluble, and they are probably changed chemically by the absorption of chlorine.
In any case their chief interest in non-filtering baths is as indicators of matter carrying
bacteria and as food for other organisms. These, with some possible exceptions,
cannot live in water which is effectively chlorinated.
During the spring and summer months of 1927 and 1928, bacteriological examinations
were made of 122 samples from 15 swimming baths and pools to determine the
bacterial content per cubic centimetre and the presence of pollution by organisms of
the bacillus coli group in 10 c.c. or less amounts of the water.
The swimming baths dealt with were at that time classified thus:—
| Number of baths. | Number of examinations made. | Bacterial content per c.c. | B. coli. present in | |||
|---|---|---|---|---|---|---|
| Average. | Highest. | Lowest. | ||||
| 84 | 1,360 | 64,000 | 4 | 1/10 c.c. in 17 samples. 1 c.c. in 33 „ 5 c.c. in 18 „ 10 c.c. in 5 „ Absent in 10 c.c. in 11 samples. | ||
| 1 | (before use) | 3 | 95 | 165 | 5 | 1 c.c. in 1 sample. 10 c.c. in 1 „ |
| (after use) | 3 | 65,000 | 80,000 | 5,000 | Absent in 10 c.c. in 1 sample 1 c.c. in 3 simples. | |
| 19 | 13 | 55 | 0 | 5 c.c. in 2 samples. 10 c.c. in 2 „ Absent in 10 c.c. in 15 samples. | ||
| 13 | 18 | 60 | 0 | 5 c.c. in 1 sample. Absent in 10 c.c. in 12 samples. | ||
It would therefore appear that the effect of the filtration plants might be considered
as having reduced the bacterial content to l/100th of that obtaining in the
untreated open-air baths; and, whereas in the latter 87 per cent. of the samples
showed B. coli pollution in amounts of water ranging from l/10 c.c. to 10 c.c., in the
baths fitted with filtration plants only 15 per cent. of the samples showed B. coli
pollution in amounts of 5 c.c. or 10 c.c. of the water.
The content of free chlorine in the water is as far as possible maintained at from
0.2 to 0.5 part per million. As much as 0.8 per million was found by Dr. J. A.
Glover, of the Ministry of Health, and the chemist to cause no irritation of the eyes