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a system of purification which is almost perfect. In course of time it will
no doubt again become necessary for large towns to revert to the London
system, because the great increase in urban development of rural areas
is making it more and more impossible to maintain sources of supply other
than those from rivers.
The River Lea has its source in Bedfordshire and, as it flows southwards
through Hertfordshire, it receives the sewage effluents of a large number
of nearby towns and villages. It supplies about a million Greater London
households, including those in Leyton, with drinking water; and, as the
water is heavily polluted above the intake of the Metropolitan Water Board,
the water authority has the tremendous responsibility of operating a system
of purification which converts its foul raw material into a drinking water
supply which is at least safe, though it may have lost much of its natural
sparkle and palatibility.
Control of Purity.
No public health service is more vulnerable than the public water
supply, and none is more exposed to destruction and contamination by
hostile attack in time of war. In my Annual Report for 1945 I wrote :—
"During the early days of the first London 'blitz' in September, 1940,
one was appalled to see fractured water and sewage mains in bomb craters which
became filled with a mixture of drinking water and sewage. Such fracture of
water mains occurred during almost every heavy air raid, and the Director of
Water Examination has reported that during one night over 500 water mains
were broken. Sewers were damaged during each air raid, with the inevitable result
that untreated sewage was discharged into the river from which the raw water
supplies came. Reservoirs were cut off from purification works by the destruction
of aqueducts. Bombs fell into filter beds and caused short circuits between
filtered and unfiltered water channels. The demand for water to deal with fires
necessitated the occasional by-passing of the slow sand filters in order to maintain
supplies. Here, surely, were circumstances which might be calculated to cause
pollution of water supplies on a scale hitherto unknown. Had the enemy
succeeded in stopping or polluting the water supply of one-sixth of the country's
population, it would have been a staggering blow worth many military victories.
"However, by exercising unremitting attention and supervision, and by the
application of special measures designed to shut out sewage from water channels,
those in charge of London's water supplies were able to avoid a major calamity
to public health and morale. Furthermore, they have achieved the wonderful
record of being able to report that not a single case of typhoid fever attributable
to the water supply has occurred in London since September, 1939. This is
indeed one of the greatest achievements during the war; but, like so much of
the work undertaken in the interests of the public health, it has never received
the appreciation it deserves because it never allowed to occur the disasters it
was designed to prevent."
The passage of time has served but to increase my wonder at the achievement
of the Metropolitan Water Board during these war years, and the fact
that it surmounted all disasters with such complete success that no case of
water-borne disease occurred in the area it serves. A truly wonderful
achievement.
Prevention of River Pollution.
Prior to 1951 it had been found that the Rivers Pollution Prevention
Acts and various local enactments were quite inadequate to prevent gross
pollution of rivers and streams, and great hopes were raised by the replacement
of these statutes by the Rivers (Prevention of Pollution) Act, 1951.
Optimists, who thought that the fight for clean rivers had then been won,