View report page

246
THE WATEB 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 1887, 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, first Water Examiner, 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.
Sir F. Bolton stated, and it appears to be generally agreed,
the "the rate of filtration should not exceed 540
gallons per square yard of filter bed each 24 hours, or 2½
gallons per square foot per hour." Filtration ought to be
effectual at this rate, which, for all practical purposes, may be
considered as a standard. Effectual filtration is greatly facilitated
by previous subsidence. The average rate of filtration,
per square foot of filtering area, in gallons per hour, by the