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16
SANITARY CIRCUMSTANCES OF THE AREA.
Water.
See Annual Reports, 1930 and 1932.
There was no water shortage in this district during the year
and no complaints received on the quality of the water.
Drainage and Sewage.
See reports of 1927, 1928 and 1932.
Sewage Works Extensions.
See page 22 of 1931 Annual Report.
The first stage of the extension of the sewage works was
completed by the end of the year and this portion was in operation.
The works have been designed to permit elasticity of operation as
circumstances demand. At the moment, domestic sewage and
trade waste are being dealt with separately.
Domestic Sewage.
After passing through mechanical screens of £ in. bar spacing,
the sewage passes to a circular settling tank which acts as a detritus
tank, a preliminary and a secondary sedimentation tank. l|le
tank is fed by pipes at the bottom, and the sewage passes to a
central weir over which it flows past deflectors and baffles un 1
it finally flows at a low velocity over a circumferential weir. Heau
solids settle to the central cone bottom to which automatic scrape'5
push the primary sludge. This cone, of two day capacity, 15
emptied by hydrostatic pressure. For the time being, and P® "?
the construction of the sludge digesting tanks in the next stage
the extensions, the sludge is being ploughed into land,
period of detention in this tank is 3 hours for a 3 m.g.p.d., or 2 nou
for a 4| m.g.p.d. flow.
The effluent then passes to the Simplex Aeration plant which
consists of 20 units in 4 rows of five. Here the liquor is given four
hours aeration by means of mechanical revolving cones.
The aerated sewage then passes into 24 cone-bottom setting
tanks for detention for a period of 6 hours before the final effuent
is discharged.