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6. Water Analysis —Professor Thorpe, of the Government Laboratory, reports that
he has examined the water supplied to the Metropolis during the month of October by the
eight Water Companies. The particulars relating to the four Companies (New River, West
Middlesex, Chelsea, and Grand Junction) supplying the City of Westminster, are as follows:—
Thirteen samples of each Company's water were examined. Taking the average amount of
organic impurity in a given volume of the Kent Company's water, during the nine years ending
1876 as unity, the proportional amount contained in an equal volume of water supplied by
each of the Metropolitan Water Companies was, on the 19th October:—Kent, 1.0; New
River, 6.2 ; Chelsea, 4.0 ; West Middlesex, 3.7 ; Southwark, 8.8 ; Grand Junction, 9.0 ;
and Lambeth, 8.8 ; East London (19th October) 8.5, (27th October) 4.4.
From these figures it is evident that the water supplied has been anything but satisfactory.
Professor Thorpe reports more fully, as follows :—
" Of the Thames-derived supplies those of the Chelsea and West Middlesex Companies,
taken on the 19th October, contained proportions of organic matter which were not
sensibly different from those found in the two preceding months and were of good
quality, but the water distributed by the Southwark, Grand Junction, and Lambeth
Companies on the same date was of very unsatisfactory quality, the amount of organic
impurity present being practically as great as that contained in certain samples taken
from these Companies' mains in May and June when the quality of the water was
exceptionally bad. The analytical data, however, indicate that the additional organic
matter which is washed into the river by the exceptional rains is mainly of vegetable
origin.
" The New River Company's water obtained from the river Lea and Wells contained
an amount of vegetable organic matter much in excess of that usually found in this
supply. The organic impurity in the sample taken on the 19th October, although less
than that present in some of the Thames-derived supplies, exceeded any amount which
had been found in the New River Company's water during recent years. The water
was of indifferent quality.
" In addition to the above analytical examination, the 105 samples, collected during
October at various places in the districts supplied by the several Companies, have been
examined, and estimations have been made of the amounts of ' oxygen consumed ' (measure
of organic pollution) and 4 albuminoid ammonia ' (measure of nitrogenous organic pollution)
the degree of turbidity, if any (indication of inefficiency of filtration or of disturbance in
the mains), has also been recorded:
" With reference to the five Thames-derived waters, the results show that in all
cases the mean proportions of organic matter were much higher than in August and
September. The amount of organic impurity in the Chelsea and West Middlesex
Companies' supplies was somewhat larger than is usual in October and remained practically
constant until the 16th ; after this date it began to rise steadily and continued to do so
until the end of the month, when the amounts exceeded those found in June and July,
and were the highest recorded this year. A consideration of the data shows that
these Companies had made fair use of their storage, and the average quality of their
supplies was superior to that of the other three Companies which distribute Thames
water. The Southwark, Grand Junction, and Lambeth Companies' waters contained
larger mean amounts of organic impurity than had been found in any previous month
this year, the Southwark Company being the worst in this respect. On many occasions
during the latter half of the month the supplies of these three Companies were of very
high colour and unsatisfactory quality. The Water Examiner's Reports show that the
storage capacities of the Southwark and Lambeth Companies' unfiltered water reservoirs
(expressed in days' supply) are now not very different from those possessed by the Chelsea
and West Middlesex Companies, nevertheless my regular examinations of the Metropolitan
supplies certainly indicate that the former Companies do not, or are unable to, make
the best use of their stored water.