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56
successive additions of sludge and the quality of effluent was not affected by very
considerable differences in depths of diffuser tanks. It was, however, discovered
that a stable liquid could be produced by mere admixture and subsequent sedimentation
of highly activated sludge and effluent. The conditions under which
this result can be assured are being still further investigated.
An important experiment with a system of mechanical agitation different from
that referred to in previous reports is now in progress at Crossness.
The public health problem arising from the fact that the area and population
now served by the Council's main drainage system will be increased in the near
future, will necessitate consideration.
Bathing
lakes, openair
swimming
baths and
paddling:
ponds.
Many examinations of the water of open-air swimming baths, bathing
lakes and paddling ponds were made during the bathing season of 1926.
The most important part of this work was an investigation, extending over
some months, of the results obtained in two baths by the use of a filtration
and chlorination plant. The results of these investigations will be set out in the
ensuing report.
In one of the parks in South London a paddling pond had been cleaned and
refilled with water from the mains. Within a fortnight it was reported that the water
was bright red. Microscopical examination showed that an abundant growth of the
red form of protococcus (var hcematococcus) had caused this visitation, of which
perhaps Egypt affords the earliest recorded instance. A small dose of sulphate
of copper successfully killed the organism, which did not reappear.
River Lee.
The condition of the river Lee continued to be unsatisfactory. Towards the end
of July, after heavy rains, the Navigation Cut from Tottenham Lock downwards
was in a foul condition, chemical analysis showing the water to be badly polluted,
whilst abundant ocular evidence testified to the very unsatisfactory state of the
river bed. Masses of putrefying debris were brought to the surface by the copious
evolution of gas from the bed, and passing barges almost grounded on the black
mud which they brought up in black clouds as they passed. This stream is still
used by the rowing clubs of East London, who continue to put out crews, notwithstanding
the very great sanitary and aesthetic disadvantages of the river in its present
condition.
The natural stream which forms the eastern boundary of the county at Hackney
Marsh is in a dirty condition. It would appear that substantial improvements in the
waters of the tributary brooks, and extensive dredging are needed to restore the
stream to a good condition.
River
Wandle.
I he effect on the water of the river of the improved treatment of sewage from
the districts included in the operations of the Wandle Drainage Board has been the
subject of some investigation. The results of examinations made in January, July and
October show that the effluent discharged at the outfall near Earlsfield Station does
not differ greatly in its degree of purification from the river water with which it mixes
and which, although in a moderately good condition, has already received much
pollution. The effect of the effluent as now discharged on the water immediately
below the outfall is not great and the condition of the river from the outfall down
to the Thames does not appear to have given rise to offence.
Disposal of
house refuse
Reference was made in two previous reports to an experiment conducted
at the Ebury Bridge depot of the Westminster City Council on the storage
of house refuse after the removal of large matters and comminution of
the finer and softer matters remaining. The heap thus obtained was kept
under observation and the changes going on in it were the subject of chemical and
biological examination.
Briefly, the effect of storage is that considerable bio-chemical changes characterised
by a very marked rise of temperature go on. Much of the organic matter is