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The following paragraphs give a general indication of the source of origin of these
samples and of the consultative and advisory duties carried out for the various services
and departments of the Council.
River Thames
The condition of the river flowing as it does through the County of London, is a matter
of great importance to the Council. In addition to effluents from the Council's own
sewage treatment plants, there are sources of pollution from other sewage works,
impure tributaries, trade discharges, and contamination from shipping. To assess the
condition of the water under varying conditions of fresh water and tidal flow, and to
compare the state between seasons of the year and over periods of years, regular weekly
examinations are made, involving chemical analysis of water taken from 26 points
over a distance of 80 miles. The area examined extends from the upper limit of the tidal
reaches of the Thames at Teddington to the outer estuary sludge dumping area at Black
Deep.
The condition of the river is worst in the summer because of higher air temperature
and normally reduced fresh water flow, the most critical period being July to September.
In 1955 the average daily fresh water flow over Teddington was only 301 million
gallons as compared with 502 million gallons daily in the previous year. The warm
weather coupled with the heated discharges from power stations resulted in the highest
average water temperatures yet recorded from Kew to Gravesend. Sulphide was present
extensively but, although higher concentrations were found than in the previous year,
the number of occasions when daily samples contained sulphide was approximately the
same.
In view of the weather conditions, the low fresh flow and the water temperature,
it would have been expected that the condition of the water would have been worse
than found. New sedimentation tanks were put into service at the Northern Outfall
Works during the year and there is evidence that the consequent reduced loading on
the river prevented more serious deterioration.
The Scientific Adviser continued to be a member of the Thames Survey Committee
of the Department of Scientific and Industrial Research, and also of the Heated and
Other Effluents Committee of the Ministry of Housing and Local Government. Both
committees deal with aspects of the condition of the water of the river and are to report
in due course their recommendations for its improvement.
Sewage treatment
The treatment of sewage at both Outfall Works is the joint responsibility of the Chief
Engineer and the Medical Officer, and as a result of the happy collaboration which
exists between their staffs, the Scientific work is carried out in the closest co-operation
with the staff of the Chief Engineer. In addition to daily consultations on the works,
the analytical results and research progress are discussed at a weekly meeting at the
County Hall between the Divisional Engineer (Main Drainage) and the Scientific
Adviser to suggest policy of operation, and to discuss methods of improving efficiency
or overcoming difficulties.
The analytical work includes examination of the following samples:—incoming
sewages, effluents from different sections of the plant, sludges sent to sea, sludges entering
and leaving digestion tanks, activated sludges, waters from the steam raising plant and
effluent liquors from Beckton Gas Works (North Thames Gas Board). Routine
observations of atmospheric pollution are also made daily.
In July the new sedimentation plant designed by the Chief Engineer was officially
opened and this necessitated an increase in the amount of laboratory work. With the
advent of the new plant it is anticipated that the automatic sampling apparatus also
designed by the Chief Engineer, and which is now in experimental use, will prove a
great asset.
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