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62
are the trustworthiness of a certain type of CO2 recorder and the efficiency of a plant
for de-aerating boiler feed-water.
Outfalls.
At the outfall laboratories systematic daily examinations of sewage treated
and the resulting effluent and sludge, as well as the water of the river Thames at
both high and low tides, and other analyses in connection with the working of the
outfalls have been continued. In addition much experimental work needed to
throw light on matters connected with the river, or sewage treatment, has been
undertaken at these laboratories.
Biological
treatment of
sewage.
The experimental treatment of large volumes of sewage, and, later, of large
volumes of effluent by mechanical agitation has been continued with uniformly
satisfactory results. Further points in connection with this mode of treatment
need investigation and are the subject of experimental observation.
river Lee.
Visits to this river in April and October showed that it continued to be in the
bad condition which has now been observed for some years from Tottenham Lock
downwards. Chemical and all other evidence pointed to the relatively pure water
from above the lock having been mixed with very large proportions of sewage, with
the result that the water itself is like a dilute sewage and the bed very foul and
continuously bubbling and throwing up black masses. The surface of the river
down to Spring Hill was very bad in October. The natural stream flowing alongside
Hackney Marshes was much polluted, but being shallow and swift was not offensive,
although black stains on the banks showed that the water contained much
putrescible matter. The tidal portion of the Lee Navigation was in a bad
condition in April.
River
Thames.
The systematic examination of the river Thames was continued in 1924 at points
from Waterloo Bridge to the Edinburgh Lightship, which is in the vicinity of the
discharge area for sludge from the Council's outfalls and for waste matters discharged
by other bodies. In addition to examination of the water, the survey of the
river bottom, which has beenin progress for some time, was carried out. The results
obtained from the examination of both river water and material from the bed showed
that, from the Chapman Light at the upper end of Sea Reach onwards to the estuary,
the evidence of pollution and deterioration of the river was small and rapidly
decreased seaward. In the neighbourhood of actual discharge no evidence of general
pollution was found.
Although provision was made for additional treatment of sewage at the outfalls,,
at no time did it become necessary to use chemical precipitants. This was in part
attributable to the relatively low temperature of the river water and the abnormal
fresh water flow of the river during the summer months.