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24
plant is under cover. The tailings then travel on a covered conveyor
belt running the whole length of a series of treatment cells. Alongside
each pair of cells is a small bin capable of holding one hour's
supply of refuse. The refuse is diverted from the conveyor belt
by means of a movable trip into the bin alongside the cell to be
filled and from here is transferred by a grab into the cell. Each day
one cell is charged and one discharged. In the cell it is sown with
a bacterial culture and oxygen-consuming fungus. After a week's
detention in the hermetically sealed cell under anaerobic conditions,
the refuse is subjected to aerobic action for a further
week, air being pumped in under pressure. It is understood that
in the aerobic stage temperatures are reached which are sufficiently
high to ensure the destruction of all pathogenic organisms. By the
end of this time the refuse has been changed into an innocuous
friable material which, after crushing, is ready for use as a fertilizer,
being loaded direct into vehicles or delivered into a covered store.
The amount of fertilizer recovered is anticipated to be 35-40 per
cent. of the gross amount of refuse delivered.
Of the sources of possible nuisances which may arise, some are
inherent in the particular process, while others are common to
other methods of refuse disposal. Of the latter there is the possible
blowing about of dust, paper, etc. on the occasion of the delivery
of the refuse from the collection vehicles ; the possible nuisances
arising from disposal or storage of re-claimed products such as
bottles and fine ash ; and nuisances arising from the incineration
which it is understood will be carried out to a limited extent in
running the machinery working the air-compressing plant. From
the time of despatch from the vehicles to its deposit in the bins
the refuse, crude or separated, is under cover. Anticipated nuisances
from this step onwards are of dust, etc. being blown about when
the refuse is transferred from the bin to the cell; smell from the
bins at the times when they have to be uncovered ; smell from any
liquor waste from the bins, and smell from the treated product at
any stage from the removal from the bin to its disposal. As to the
possibility of smell from the cells during treatment it is understood
that for the first seven days the cells are hermetically sealed.
During the aerobic period of treatment, when compressed air is
being passed through the material, the gases will pass from the cells
through a scrubber, passing then through a stack in which they will
mix with flue gases from the incinerator. A centrifugal fan will
maintain a slight suction on the air in the cells during the treatment
process.
At their meeting on January 1st, 1938, the Council approved
" the principle of destructing all refuse by the ' hyganic ' process."
The weekly average amounts of refuse disposed of in December
were, at the Harrow destructor, 275 tons ; at the Wealdstone
destructor, 150 tons ; at the Pinner controlled tip, 210 tons ; and
at the Stanmore controlled tip, 220 tons.