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37
works; the lower level is supplied from West Wickham and
Orpington Wells with additional Thames-derived water during the
summer months.
All the water is chlorinated before it leaves the works.
Contact tanks are now in operation at all these works to give
opportunity for the chlorine to exert its full effect before the water
is pumped into supply. Any residual chlorine in the well waters
is completely removed before the water leaves the works.
Bacteriological analyses of all supplies are made at least five
times a week and in the case of the river-derived supply the water
is tested bacteriologically at all stages of purification. All new
and repaired mains are disinfected with chlorine before being
restored to use and samples of water from them are tested to
establish that the quality of the water is up to the standard
normally supplied.
None of the supplies is plumbo-solvent.
The closest watch is kept for any evidence of deterioration in
quality whether physical, chemical, bacteriological or biological
and immediate action is taken if the results of analyses are not up
to standard.
The following tables give the average results of the chemical
and bacteriological analyses of the various supplies to the area
for 1954."