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Water as delivered to the consumer is examined monthly by the
Counties Public Health Laboratory on behalf of the Company and
a further 12 chemical and 26 bacteriological samples were examined by
the Public Health Departments in the supply area. All were satisfactory.
The following is a representative analysis:
Chemical analysis in parts per million.
Total solid matter in solution (dried at 180° C.) 220
Combined chlorine 22.0
Nitric nitrogen 12.0
Nitrous nitrogen none
Ammonia, free and saline 0.010
Ammonia, albuminoid 0.039
Oxygen absorbed from permanganate in 4 hours at 26.7° C. 0.15
Hardness—by acidimetric titration—Temporary 51
Permanent 69
Total 120
Reaction for free chlorine negative
pH 7.5
Iron 0.02
Bacteriological examination.
Action by free chlorine during transit of the sample was
prevented at the time of sampling.
Number of colonies per ml. developing upon agar in 2 days at 37° C. 0
Number of colonies per ml. developing upon agar in 3 days at 22° C. 0
Organisms of the coliform group absent in 100 ml.
Streptococci do.
CI. welchii do.
This water has the same general characteristics as previous samples taken
from this source. It is of satisfactory organic purity and moderate hardness,
and the reaction (pH) is well within the 'neutral' range. There was no residual
chlorine at the time of receipt.
Although the water itself was bright and clear, slightly bluish in colour
and of attractive appearance, there was present a small quantity of rapidly
settling insoluble scaly matter, both brown and grey in colour. This scaly
matter contained, besides oxide of iron, numerous bacteria of apparently harmless
saprophytic types such as accumulate in the scale of pipes from time to
to time, and have no adverse significance.
The bacteriological condition of the sample taken for bacteriological
examination was excellent and none of the scale observed in the chemical
sample was detected.
The small amount of scale deposit is regarded as being the result of a
chance occurrence which might occur at any time, and as judged by these
samples the water is pure and wholesome and suitable for the public supply.
The average hardness of the samples taken by all the local
authorities' Public Health Departments was 8.75°. Three slightly
exceeded the statutory limit of 9° and 12 were below.
Drainage and Sewerage
Construction of the deep manholes to the sewers in Blakehall
Road and Grosvenor Avenue were completed during the year. These
will greatly facilitate the work of maintenance.
Sewage is pumped to the disposal works of the Croydon Corporation
in Beddington, except at various points on the fringes of the district
where it is more conveniently drained to the sewage systems of neighbouring
authorities.
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