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During the year no less than 310 such samples were taken and
examined. Of these, 129 were samples of chlorinated water passing
into public supply; everyone of these was free from coliform
organisms and of a very high standard of purity.
Chemical examinations of the water from individual wells now
in use, showed that the organic quality remained entirely satisfactory
throughout the year.
Bacteriological examinations of the untreated water showed
that, under normal conditions, the wells produce a water of remark'
able purity. Only at times of serious flooding by the river Thames
is a temporary deterioration sometimes observed in one or more of
the wells. Under the present arrangements this can readily be dealt
with by shutting down the wells concerned for a few days.
There have been complaints that the water tastes of chlorine.
Every effort is made to reduce this to a mininium but this nuisance
cannot be eliminated unless new and very expensive apparatus is
installed.
Fortunately the proportion of residents who are unduly
sensitive to the taste is not large and I am able to say, with confidence,
that the small quantity of chlorine is quite harmless and that
the water supply is wholesome in every respect.
Richmond water contains 30 parts per 100.000 of hardness and
is not plumbo'solvent.
(b) The supply of the Metropolitan Water Board is received
in bulk through six connections off the 30 inch M.W.B. main.
The source of the water is the River Thames abstracted at
Wraysbury, Laleham and Walton intakes and stored in the Thames
Valley reservoirs. After storage the water is treated at the filtration
works at Hampton and Surbiton.
All the water is chlorinated before it leaves the works and
adequate contact to ensure complete action has been provided at
Hampton by the building of a contact tank which first came into
operation in July, 1948. Since the 19th October the filtered water
has been treated by the method of controlled super'chlorination in
place of the ammonia-chlorine process. Free chlorine is a much
more powerful disinfectant than chloramine and there is, in addition,
a considerable saving in the cost of chemicals.