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27
After having the works under his personal control for three
months, Mr. Dibden recommended the following permanent reconstructions.
The Works at the present time are capable of treating
the whole of the sewage, but certain points require attention in
order to put them in the best working condition. The dry weather
flow especially ascertained is equal to 420,000 gallons per day.
For the treatment of this quantity, plus 54,000 gallons, the estimated
increase in two years, extra slate beds and fine clinker beds will be
required. The clinker contact bed capacity can be obtained by
raising the level of the surface of the beds. The additional slate
bed capacity can be provided by filling the existing sedimentation
tank and two slate tanks to the top of the walls with slate, constructing
one new slate bed and arranging the level of the floors of
all the beds so that they drain properly to the fine chamber beds.
After leaving the slate beds the effluent should pass through a
humus collecting chamber, the deposit in which will be passed on
to drainage and drying beds, the fine beds will thus be protected
and the labour otherwise necessary to keep them in the best
working order will be reduced. The present annual cost for
chemicals and sewage disposal is practically sufficient to repay the
loan and interest on the amount required for these alterations, so
that by the adoption of this treatment it can be made without
actual further cost to the ratepayers. In addition to this, all risk
of nuisance from the accumulation of sludge will be absolutely
avoided.
The expert appointed by the Royal Commission in the year
1909 to report upon the working of the slate beds at Devizes
(investigated and reported to the Council by me in 1906) reported
as follows:—
This sludge causes no nuisance during the process of drying,
and when dry, breaks up easily into a substance very like ordinary
soil. No offensive odour could be detected in the bed even when
standing at the bottom of it on a hot day, in fact it smelt exactly
like a damp cellar. The system of beds can be extended as
required, but care must be taken to secure the system of beds
being kept well up to date, and not allowed to fall behind the
requirements of the growing population, overworking the existing
plant by not following out this method, difficulties will arise which
by careful forethought can be easily avoided.