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27
In view of its flooded condition and location in a central area
the tipping method presented a problem. The pit contained
approximately 3½ million gallons of water with a chromate content
of 200 parts per million. The chromate concentration was
such that it was not possible to pump out the water unless the
chromate content could be reduced to below 10 parts per million
because of its effect on the disposal works plant and the effluent
produced.
The offensive smell which arises from wet tipping is mainly
due to the production of hydrogen sulphide. This results from the
breakdown of sulphates by sulphate reducing bacteria.
Discussions took place with officials of the Department of
Scientific and Industrial Research who had found that chromate
has an inhibitory effect on the sulphate reducing organism
desulphovibrio desulphuricans.
Experiments carried out indicated that a nuisance was likely
to occur if tipping took place into water containing chromate
unless the supply of chromate could be replenished. Controlled
tipping started on the 1st June, 1954, and by the end of the
month the chromate content was considerably reduced. Ultimately
it was found necessary to add further supplies of chromate
waste weekly which prevented any nuisance arising.
When the chromate content was down to a trace, the water
was pumped out of the pit with the exception of a small amount
of water which was kept inocuous by the use of chromate waste.
By the end of the year normal dry tipping was being carried on.
It is believed that this is the first time that the nuisance normally
arising from wet tipping has been prevented by the use of
chromate waste.
Requests were received from a number of householders for
assistance in the destruction of wasps nests. Eighty-nine wasps
nests were destroyed. Some requests were declined where the
nests were found to be in positions not causing real inconvenience.
Many householders sought the advice of the Department about
various animal, insect and mite infestations and were given
advice and in some instances practical assistance. That the
public appreciate this service is shewn by the many letters and
messages received.
By arrangement with the Surrey County Council the school
kitchens and canteens (seven in number) were thoroughly sprayed