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171
Middlesex Company was conspicuous by a higher maximum and
a greater average of organic impurity. Every sample of river
water was clear and bright when drawn from the mains, a fact
highly creditable to the Companies as evidence of the extreme
care taken in filtration.
The Water Examiner's Report—I am indebted to the
courtesy of Major-General A. de C. Scott, R.E., the Water
Examiner, for an early copy of his Annual Report for 1888,
from which most of the following particulars are taken.
General Scott's duties as Water Examiner are multifarious and
important. He makes monthly inspections of the several Metropolitan
waterworks, filter beds, reservoirs, &c., examines the
quality of the water, both at the intakes and after
filtration at the works, and reports, monthly, the results of such
inspections and examinations to the Local Government Board.
Upon him rests the responsibility of seeing that the requirements
of Section 4 of the Metropolis Water Act of 1852 are
complied with—viz., that "every Company shall effectually
filter all water supplied by them within the metropolis before
the same shall pass into the pipes for distribution.'' The
effectual filtration of river water depends, according to the late
Sir F. Bolton (the first Water Examiner, appointed under the
Act of 1871) upon :—
1. A sufficient area of properly constructed filter beds, constantly
cleaned, and fresh sanded from time to time as the original thickness
is reduced ;
2. The rate of filtration being controlled and limited to a certain speed ;
3. The water delivered into the filter beds having been previously stored
in subsiding reservoirs, and the capacity of these reservoirs being
such as to avoid the necessity for the intake of turbid and muddy
water during the time of extraordinary and heavy floods, which
tend to foul and choke the filters.
A limit to the rapidity of filtration has been generally
adopted. It is represented by the passage of about 540 gallons