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41
that it would not be justifiable to interfere largely with the
sewers, which admittedly allowed the entry of large volumes of
subsoil water, but advised that those most defective in this
respect should be dealt with from time to time.
Shortly after this report was received, changes occurred in
the staff of the Authority, and the new surveyor, Mr. Forder,
was instructed to report and draw up a scheme for the
improvement of the Sewage Works. Mr. Forder also recom
mended chemical precipitation, and ultimately complete plans of
the proposed settling tanks, plant, and so forth, were prepared.
Very careful consideration was given to these plans, and at
length, as the term of office of the Authority had almost expired,
it was decided to take no decisive action until the District
Council had had an opportunity of considering the subject; and
a* the close of the year the matter remained there.
One of the difficulties at the works consists in the large
amount of detached " sewage-fungus" which finds its way into
the river with the effluent. Mr. Forder recommended, as a temporary
expedient, the adoption of a system of wire-screens, which
has now been completed. These screens require the attention of
three men, employed in shifts, and although the screens do not
exclude all the fungus, yet they undoubtedly do prevent a very
large quantity of fungus from daily entering and polluting the
river.
In considering the best way out of the difficulties connected
with the sewage scheme of this District, it is necessary to bear
in mind that, when first designed, it was intended that the
sewage should be purified by means of intermittent downward
filtration, owing to the restricted area of the land available.
For this process the preliminary settlement, as complete as
possible, of the solid matters suspended in sewage is an essential,
and for this purpose a " settling-tank," with coke screens was
provided. In consequence, however, of the volume of sewage
being under-estimated, owing to the admission of large volumes
of subsoil water into some of the sewers, the so-called "settling-