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The following paragraphs relate these activities to the various responsibilities and
services of the Council with special reference to matters specifically related to public
health.
River Thames
The condition of London's river is of special concern 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 at Teddington to the sludge dumping area at Black Deep in the outer
estuary.
Dissolved oxygen is continuously being absorbed by oxidisable matter present in the
water and the rate of renewal of oxygen from the air depends on the temperature, the wind,
and other factors. If the process of absorption requires more oxygen than can be replaced
from the air, putrescent conditions arise in which sulphate-reducing bacteria produce
hydrogen sulphide from water-soluble sulphate. The summer quarter, July to
September, with its higher temperature and reduced upland flow is normally the
critical period, and in both these respects 1959 was exceptional. The average daily freshwater
flow over Teddington Weir during this quarter was less than half that of the comparable
quarter of the previous year; early in September it was reduced to the statutory
minimum of 170 million gallons daily, which condition prevailed for seven weeks. The
average temperature of the water measured off the outfall works was the highest yet
recorded. These adverse circumstances were associated with a deterioration in the state of
the river as compared with the previous year, although the position was less unfavourable
when comparison was made with 1957 which was a year of normal fresh-water flow. There
was some evidence of improvement in the condition of the river at high tide off the
Northern Outfall Works.
The Scientific Adviser continued to be a member of the Thames Survey Committee of
the Department of Scientific and Industrial Research, and 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 river and are to make 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 of Health. Close daily collaboration is maintained
between their staffs and weekly conferences are held between the Divisional Engineer
(Main Drainage) and the Scientific Adviser, together with their senior officers, to discuss
analytical results and operational practice.
The primary sedimentation tanks at the Northern Outfall Works, installed in 1955,
continued to reduce the amount of suspended matter leaving this section of the plant by
one-half and the oxygen demand by one-third.
Secondary treatment of 40 million gallons daily was given in the paddle-type activated
sludge plant. In mid-September the first steps were taken to build up activated sludge in a
new diffused air plant, and the plant was officially opened by His Royal Highness the Duke
of Edinburgh on 22 October. Units treating 20 million gallons daily were operating at the
end of the year and units for a further 40 m.g.d. were waiting to be put into service. From
the initial operation there was every sign that the new plant would effect a substantial
reduction in the oxygen demand of the effluent.
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