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53
River Lee.
An examination of the portion of the river Lee between Tottenham lock and
Homerton was made in July, when the reach above Lee bridge was found to be
in a very unpleasant condition which was most marked in the neighbourhood of
Tottenham lock. Although some of this reach is outside the county of London,
it is much used by boating clubs and others. Below Lee bridge, the river was not
offensive, although the water was very highly coloured and analysis showed that
it was not very much diluted sewage effluent. Several bathing parties were observed.
Towards the end of November, the condition had appreciably improved but was not
good. It is understood that the problem is being considered by the Ministry of
Health.
River
Wandle.
An examination of the river Wandle was made on 15th July, The general
impression formed was that the river is badly polluted before it reaches the county
of London; that its water is an unsuitable medium for the growth of watercress; that
the Wandle valley effluent is an important source of pollution entering the river
within the county and that the widespread use of the river as a receptacle for refuse of
all kinds adds considerably to its present unpleasant state. The water level was
naturally, having regard to the season, very low at all places. The use of the water
for cooling purposes at the Southern Railway power station at Earlsfield by raising
its temperature accelerates all bio-chemical changes: as re-aeration also occurs, the
net result of this diversion may be good. No real improvement can be expected
unless the contributions, direct and indirect, from places in the upper part of the
valley outside the county are diverted or purified.
Swimming
baths.
During the summer the Council s outdoor baths were very much used. In
those which were not fitted with filtration plant much difficulty was experienced
in keeping the water in good condition. It appears impossible owing, not only
to actual soiling of the water, but to the separation of calcium carbonate as a result
of photo-synthesis, to keep water in such baths reasonably transparent for long
periods. Experiments made in the laboratory, as well as practical experience at
the baths, show that the green growths which spring up in water exposed to daylight
are in some cases very resistent to the chemicals added with a view to their destruction.
This difficulty has been found by many observers, who have sought to keep open
reservoirs and conduits in good condition.
Greenwich
power
station.
The chemical work at the laboratory at the Greenwich power station is concerned
with the scientific control of the station and consists of systematic examinations
of coal and other fuel used both here and at pumping stations, etc., boiler and
condenser waters. Investigations of problems arising out of the working of the
station, such as corrosion, temperature and composition of flue gases, deaerating
and water-softening plants, examination of chemicals and materials used on works,
boiler scales and deposits, etc., are also undertaken. Some of these investigations
are in part made at the County Hall laboratory.
River
Thames.
The very dry weather experienced during the first nine months of 1929, led to
a greatly decreased fresh-water flow of the Thames. The systematic examination
of the river by the chemical staff showed that this had a prejudicial effect on the
condition of the water, more especially in the vicinity of the outfalls. The proportion
of sea-water found at Crossness at the beginning of October amounted to
60 per cent. at high water. Such a great concentration of sea-water indicates how
much the removal of sewage effluent from the river is retarded during seasons of
drought. The improvement of the effluent which will result from the installation
of successive purification units, one of which is now being erected, should do much to
counteract the unfavourable effects of drought.
The condition of the upper part of the tideway of the Thames was examined
periodically during the summer, by means of a vessel placed at the disposal of the
medical officer by the Metropolitan Asylums Board. It was found that instead of
progressively improving as the upper limit of the tide was reached at Teddington,