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24
Sewage Works Extensions.
See page 22 of 1931 Annual Report.
During 1932 the Ministry of Health sanctioned the raising of
loans amounting to £123,258 for this work. This amount covers
the construction of the first part of the scheme, of which about 25
per cent is now completed. It is anticipated that the whole of this
section will be put into operation in August, 1933.
Plans are now in preparation for the second part of the
scheme, comprising sludge digesters, sludge lagoons, and road
works. This section will bring the total estimated cost of the
scheme up to £164,168. The general development of the works is
following the lines outlined in the report for 1931, with the exception
that the sludge digestion capacity is being increased, so as
to provide complete digestion for the sludge from a population
of 100,000.
Rivers and Streams.
See 1930 report.
In August, a complaint was received that a number of ducks
at a local farm, on going to the brook first thing in the morning,
shortly after entering the water, expired. Post-mortem examination
disclosed that the deaths were due to cyanide poisoning. Further
up the stream a local factory was in the process of closing down.
Samples of the stream above these works proved to be free from
cyanide, but below, heavily polluted. In one of the processes
carried out at the works, cyanide in large quantities was used.
It appears that some of the vats that contained a strong solution
of cyanide had been emptied into the surface drain that passed
through a cesspool. Ordinarily the contents of this cesspool
leaked into the surrounding soil. Owing to the large volume of
water used for flushing on this occasion, the level of the contents
of the cesspool rose to a height sufficient to allow it to reach a
branch outlet placed high up connecting it to the surface drains
which ran into the brook. The contents of the remaining vats
were otherwise disposed of; the open spaces through which the
brook flowed were closed to prevent children playing in the water;
the system of surface drainage at the works was well flushed;
and aluminoferric deposited in the brook just below the inlet ot
the surface drainage of the factory. The brook water was
analysed at frequent intervals and very soon was proved to contain
only the merest trace of cyanide.