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SOUTHERN OUTFALL WORKS LABORATORY—
The work at this laboratory consisted of analysing sewage, effluent and sludge for works
control and calculating the load placed on the river by the discharge. Advice was also given
on any scientific problems which arose with the ancillary plant and samples submitted
included waters and scale deposits. This laboratory has specialised in the determination of
hydrogen sulphide in the atmosphere and in solution and of small concentrations of metals
in sewage, effluents and sludge.
River Thames
The condition of the river is a matter of great importance to the Council and since 1893
samples of the water from midstream off both sewage outfall works have been collected
daily for analysis. In recent years a systematic scheme of sampling and examination had
been built up whereby, in addition to daily samples from both outfalls, weekly samples
were taken at twenty.four other points from Kew down to the sludge dumping area in
the Black Deep in the estuary. In the early part of 1959 a modification was made in the
sampling arrangements for the lower river; instead of weekly examination at high water
at all points below the Southern Outfall Works, examinations have been made of high
water samples one week and low water the next, collected at various points between the
Northern Outfall Works and Mucking. These runs were designed to obtain information
about the condition at Mucking, as nearly as possible at dead high or low water. On one
week in each month the examination is extended from Mucking to the dumping area on
a high water run in one of the Council's sludge vessels. Once a fortnight the fresh water
coming over Teddington Weir into the tidal portion of the river is analysed.
In order to assess the condition of the water at any time and compare its state as it
varies between the seasons of the year and over periods of years, a full chemical analysis
is made. Bacteriological work is also carried out.
This information is necessary to ascertain changes in the general condition and to
determine trends when factors such as the flow of fresh water are taken into account.
The most important determination made is that of the dissolved oxygen. This dissolved
oxygen is continuously being absorbed by any oxidisable matter present in the water,
whilst the rate of solution of oxygen from the air by the water depends on the temperature,
the wind, the presence of impurities and other factors. If the former process requires
more oxygen than is present or can be absorbed, putrescent conditions will arise and then
the sulphate.reducing bacteria present will produce hydrogen sulphide from water soluble
sulphate.
The summer of 1960 was unusually wet, with the result that, at all times, the fresh water
flow over Teddington Weir was above average and towards the middle of September
began to rise to volumes which were well above those expected for the last quarter of the
year.
The summer quarter, July to September, with its higher air temperatures and reduced
upland flow, is normally the critical period; in both these respects the summer quarter
of 1960 was exceptional. The average daily fresh water flow over Teddington Weir was
602 million gallons—52 per cent, greater than the average flow taken over the past fifteen
years. At no time did it fall to 300 million gallons a day and by September it had risen to
above 1,000 million gallons a day, a flow reached in September in only one year, 1958, in
the past 30 years.
A survey of the analytical results during the year leads to the following conclusions:
(a) By comparison with conditions during the previous ten years the river showed
an improvement throughout the year, particularly during the summer quarter. At both
high and low water dissolved oxygen was present at all points, a condition not equalled
during any of the previous ten years.
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