View report page

5
5. That the "bacterial effluent" of settled sewage from the coke-beds
does not undergo offensive putrefication at all, even in summer heat, and
can never become offensive. That this effluent satisfactorily supports the
respiration of fish.
6. That the use of chemicals is quite unnecessary under any circumstances
when the above method of treatment is adopted.
Recommendations founded on the above conclusions.
It would appear desirable, therefore, without delay, to commence the treatment
of the London sewage by the above bacterial method. The construction of
the necessary works will take time and will involve expenditure, but unless it is
taken in hand, all considerations tend to show that owing to the increased abstraction
of water by the water companies, both at their existing intakes and at the
newly constructed reservoirs for storm water at Staines, a large portion of the lower
river will continuously deteriorate. This deterioration would arise from the increase
in the amount of the discharge of sewage effluent and the decrease in the upper
river flush. Possible trouble arising from these causes will be absolutely prevented
by adopting, under proper conditions and on a large scale, the treatment which has
been strikingly successful on the experimental scale. It must be remembered that
the condition of the river cannot be improved by any suddenly adopted action.
If the treatment is introduced without delay and is gradually extended it may
reasonably be expected that the increasing deterioration in the lower river water
will first be checked and will ultimately be prevented; while the gradual development
of the treatment will cause the expenditure to be spread over a period of years,
and will prevent it from being unduly burdensome.
It must be remembered that the present settling channels would serve, as at
present, for settling purposes, but by the altered method of working them they
would also act as sludge destroyers. They should, however, undoubtedly be preceded
by grit chambers. It must be further borne in mind that the expense involved in
the purchase and application of chemicals would be dispensed with.
By a considerate adoption of the method, therefore, the expenditure might
be distributed, and need not be large at any one time.
A fuller statement of details is supplied in subsequent sections.
Summary of Information furnished by Towns and Districts in which the
Bacterial Treatment of Sewage has been employed.
Treatment of Sewage has been employed.
At the end of this report a tabulated statement of the results of the Bacterial
or natural process of treating sewage in some of the principal centres throughout the
country, is appended. It has been thought that this information would prove useful
as a means of comparing the results of the various experimental and permanent
installations with the results obtained by the London County Council, and would
show how extensively the method is already in use. It would also serve as a guide
in extending the use of this method of treating sewage to fresh centres of population.
Some of the authorities have furnished most exhaustive records of the
experiments and work which they have carried out, and, with the exception of
Glasgow and Huddersfield, the opinion expressed is entirely in favour of the treatment
of sewage in bacteria beds by a method suited to the requirements of the
district and to the character of the sewage.
At Glasgow the results of the treatment of sewage in experimental bacteria
beds indicated a purification from putrescible matter of 95 per cent., while the open
septic tank was the means of reducing the amount of sludge by 54 per cent. Similar
results have been accepted as satisfactory at other centres. The objection to the use
of bacteria-beds at this centre appears to be that the area required for their
installation at the Dalmuir Sewage Works for the treatment of 49 million gallons,
would be 164 acres, while the system of treatment by lime and sulphate of
alumina could be satisfactorily carried out on a superficial area of 23 acres. By
this latter method it is claimed that every trace of suspended matter is removed, and
that 30 per cent, of purification from putrescible matter is effected.
At Huddersfield the sewage is of an exceptional character, since 30 per cent, is
derived from manufacturing processes, almost wholly woollen, and it contains a
quantity of soap, fat, and dyes, and a variety of chemicals used in the dyeing and
finishing of woollen goods. The best results were obtained by treating the sewage
with a small quantity of lime and sulphate of iron, followed by double contact in