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be as high as obtains in the baths where the water is filtered, but the water can be
rendered reasonably safe from a health point of view by suitable chlorination. This
does not, however, abolish the great disadvantage to feeble swimmers and nonswimmers
of having a water which soon becomes turbid, because a drowning person
might be unobserved, whereas in clear water he would be easily seen and probably
rescued. In the case of the "filtered" baths, advice is given to the parks department
on the control of the chlorination and filtration of the water.
Greenwich
power
station.
In addition to the sampling and examination of fuels for the tramways and
other departments and the routine necessary for the maintenance of adequate
control in the water system of the power station and in the combustion of the various
fuels employed, the work of the Greenwich laboratory during the year has included
the investigation of a number of corrosion problems, and considerable assistance
has been given in connection with official tests on de-aerating plant and certain
steam-raising units.
The corrosion of iron work in contact with new flooring in the switch house
was found to be due to the presence of chloride in the flooring composition employed
and was remedied by replacing the material by a Portland cement mixture at the
places of contact.
Cases of corrosion in a boiler of the Council's sludge vessel the "John Perring"
and in a Stirling boiler at the Northern Outfall works were also investigated at some
length, and remedial measures were recommended which appear to have been
effective in countering the corrosion troubles.
Battcrsea and
Fulham
power
stations.
The possible effect of flue gases emitted from these stations upon the atmosphere
of the surrounding districts has been under consideration, and observations, additional
to those included under the general scheme of investigation of atmospheric pollution
in which the Council and many other local bodies in Great Britain co-operate with
the Department of Scientific and Industrial Research, have been made by order
of the Public Health Committee at places in the county.
The authorities responsible for both of the projected super-stations have been
alive to the necessity of treating the flue gases with a view to the removal of sulphur
acids and the reports of a committee presided over by the Government Chemist
have shown that a measure of success has been achieved on a fairly large experimental
scale. The possibility that the water used in washing the flue gases may have an
unfavourable effect on the water of the Thames has been considered. The attention
of the Port of London Authority has been directed to the matter and the Authority
appears to have obtained reasonable safeguards.
The chemist assisted by experimental work and attendance at conferences
in the presentation of the Council's case against the proposals for the enlargement
of the Fulham station, which was heard by the Electricity Commissioners
in December, 1930.
Outfalls.
The regular examination of the sewage treated at the outfalls and of the effluent
and sludge produced has been carried on since the present treatment was started
in 1888 and 1890 respectively. At both outfalls the percentage of dry matter in
the sludge was between 7 and 8, the difference being about 0.2 per cent. in favour
of Barking. The dry matter in individual cargoes varied from 1.0 per cent. to 16.0
per cent. at Barking and from 0.8 per cent. to 13.9 per cent. at Crossness, the
distribution of individual results being fairly uniform around the mean which in
each case fairly represents the "mode" of its constituents. On comparing with
results obtained in the earlier years of the outfalls it does not appear that the use of
chemical precipitants produced a less watery sludge when allowance is made for
the weight contributed by the precipitants themselves.
River
Thames.
The examination of the water of the Thames near the outfalls, begun in 1885,
and more extended examinations in the course of the sludge ships and at a few places
above the outfalls have been continued. The condition of the upper reaches of the