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distinguish readily between kerosene or paraffin, diesel oil and light fuel such as used in
domestic central heating appliances, chemically these three liquid fuels are indistinguishable.
Because of this it has not been possible to make an investigation at Heathrow. It is understood
that the laboratory are considering the possibility of making an investigation at another
airport where there is less likelihood of emissions of diesel or light fuel oil interfering with
the results.
(b) Odours from a coffee manufacturing process.—It was hoped that this problem would be
solved late in 1971 by which date an entirely new process and method of dealing with the
odours was to have been installed in the factory. The new method would have resulted on
a number of identical pieces of equipment being installed. Unfortunately, in the first two of
these to be installed there were quite serious fires and it was necessary to discover and rectify
the cause before continuing with the operation. This has now been done and the remainder
of the work will proceed.
(c) Odours from a Caramel manufacturing process.—Investigation has been made into the
possibility of reducing the effluvia caused by a caramel manufacturing process. The manufacturers
are experimenting with the possibilities of masking the odour by the use of deodorants.
Preliminary trials have taken place and the method appears to offer a degree of success at
a reasonable cost.
(d) Odours from a refuse tip.—A persistent obnoxious odour affecting a portion of the southern
part of the Borough was traced to the area of stagnant water adjacent to a refuse tip. This
nuisance was eliminated by the use of chemicals after agreement with Thames Conservancy.
WATER
SWIMMING POOLS
There are 22 swimming pools in the Borough, varying in size from the large public baths to

Many of them are unheated and are only used for short periods during the summer season.
Regular tests are carried out on the pool waters to ensure the efficiency of the water purification
processes. The chlorine content and pH value of pool waters are checked by the use of a colour
comparator and pH meter and when necessary bacteriological examination is also carried out.
An area of Ruislip Lido is chlorinated and used for bathing purposes.

Unsatisfactory samples were due to failure on the part of the pool operators to maintain
satisfactory dosage rates.
During the year a new pool was brought into use employing Bromine for water purification.
Bacteriological tests showed this method of treatment to be satisfactory.
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