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10
In November, 1918, the Highways Engineer was instructed to submit a scheme
with plans and estimates for screening or otherwise dealing with the whole of the
refuse collected, and in February, 1919, the plans were approved by the Council.
Col lection.—The refuse is collected by means of 16 motor vans, each having
a capacity of 8 cubic yards, equal to a load of from 2 to 3 tons, with three dustmen
besides the motor driver.
Disposal.—The dust lorries, on arriving at the Depot are first passed over a
weighbridge. They then deposit their loads in a large concrete pit capable of
holding 180 tons, which equals the maximum tonnage collected in one day.
This pit enables the motors to discharge their loads immediately, and they are
thus quite independent should any delay arise through a temporary stoppage of the
screening plant.
The refuse is lifted out of the pit by means of a 35 h.p. electrically driven crane,
fitted with a grab capable of lifting two cubic yards at a time. This grab discharges
over a steel hopper, thence on to a shaking sieve or screen constructed in four
sections, each section moving in a different direction (at any given time) to the other
three.
The refuse passes down from one section to another, is turned over, shaken,
sifted and separated into four grades according to the size and nature of the various
constitutuents as follows :—
(a) Fine Ash and Dust.
(b) Breeze, which consists of cinders and unburnt or partially burnt coal.
(c) Miscellaneous refuse, waste paper, bottles, rags bones, etc.
(d) Tins and iron articles.
(a) The fine ash, as it falls from the sieve, passes over a magnetic separator
which extracts particles of iron such as nails, pins, hairpins, etc., after
which it passes to a crusher, and is ground into a fine powder having a
commercial value as a fertiliser.
(b) The breeze also passes over a magnetic separator which recovers aiiy iron
articles. It is then shot direct into a breeze washer which cleanses it,
removing broken glass, crockery, etc.
This washed breeze has a commercial value as a low grade fuel especially
useful with a forced draught.
(c) The miscellaneous refuse also passes over a magnetic separator which
extracts further iron articles such as tins, wire, etc., and then on to a
moving belt conveyor passing between a number of sorters who pick
off waste paper, rags, bones, bottles and any other saleable articles.
The residue passed on^ is shot into the stoke-hole and burnt by means
of forced draught under a Babcock boiler, thus raising steam to drive
the plant.
(d) The iron articles collected from the magnetic separators are put through
a de-soldering furnace, the solder extracted and the iron residue pressed
into bales by means of an hydraulic press.
From the house refuse received in the Depot, it will be seen that the following
saleable products are extracted:—
(1) Fine Ash (manure).
(2) Breeze (low grade fuel).
(3) Waste Paper.
(4) Rags.
(5) Bones.
(6) Bottles, jars and glass.
(7) Solder.
(8) Old iron and tins.