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The Water Examiner states that the Local Government Board are in communication with the
Water Board as to the experiments which shall be undertaken under section 25 of the Metropolitan
Water Act, 1902, with a view to determining whether the present system of purification cannot be still
further improved, and it is expected that arrangements will shortly be made for carrying out these
investigations.
The need of adequate provision for storing water before running it on the filter beds is insisted upon
in the report, and it is stated that " at present some of the districts which have large storage reservoirs
take water direct from the river or merely run it through some of their smaller reservoirs before passing
it on to the filter beds." The report points to the marked improvement in the quality of the water
supplied to the Grand Junction district, since the bulk of the supply has been taken from the Staines
reservoirs. The Water Examiner anticipates an equally marked improvement in the quality of water
supplied to the Southwark and Vauxhall divisions of the Southern district when the new storage
reservoirs at Walton, which were completed during the year, are brought into use.
Dr. Houston, Director of Water Examinations, in his report to the Metropolitan Water Board for
the 12 months ended March 31st, 1907, makes the following observations upon the importance of
storing water before delivering it to the consumer. He distinguishes between passive storage (holding
water in store for emergency) and active storage (habitually circulating new river water through the storage
reservoirs), and he points out that great caution should be exercised in drawing conclusions
in connection with figures as regards " number of days' storage." Thus he says :—
" For example, a reservoir might hold 365 days' supply and yet the daily supply might be drawn direct from the
river throughout the entire year, the water being simply held in store in case of exceptional drought. This is an extreme
and suppositional case, but in lesser degree the same principle applies to some of the Board's works. For example,
the nominal figures for the number of days storage capacity in connection with the Southwark and Vauxhall Works
during 1906 was 12.7 days ; but in practice it appears to have been customary to draw on this stored water only when
the river was in flood and to turn the raw unstored river water on to the filter beds at such times as the water appeared
to be in good condition. In effect this means that during a proportion of the total number of days throughout the
year 1906, the storage was nil, not 12.7 days. Apart from the necessity of having water in store to cover times of drought,
or periods during which the rivers are in high flood, it is desirable to hold a clear conception of the value of storage
from the point of view of epidemic disease, and conceptions as to " safety " should, as a counsel of perfection, be based on
the minimum number of days any portion of the raw water may be assumed to take in travelling from the river
to the consumer.
There is a consensus of opinion among bacteriologists that pathogenic microbes do not multiply in storage
reservoirs, but gradually lose their vitality.
The time required to effect the destruction of these bacteria is matter for controversy, and although the American
authorities consider a few days may suffice, most British bacteriologists place the limit at a much longer period;
The essential point is that each day's storage makes for safety.'and that time arrives eventually when all the pathogenic
bacteria have perished, and in such a case subsequent filtration alone is required to improve the chemical and
physical qualities of the water already incapable in giving rise to epidemic disease.
There i s indeed an intrinsic biological difference between storage and mere filtration which should not be overlooked
The fact that there are almost insuperable difficulties in directly and practically proving the absolute benefit, as regards
the elimination of pathogenic bacteria, resulting from adequate storage, does not destroy the value of the indirect and
inferential proofs which have led both epidemiologists and bacteriologists to regard storage as of paramount importance.
Until the safety limit has been determined—and it doubtless varies according to the quality of the water, and
the season of the year—it is obviously desirable to store water for as long a time as is economically possible. In this
connection it may be asked whether storage if too prolonged may not actually lead to deterioration in the quality of a
water. Under certain conditions which do not lend themselves to accurate definition, a water may deteriorate on
storage, as judged by its chemical and physical qualities, owing to the abnormal growth and subsequent decomposition
of some species of Diatomacæ, Cyanophycete, and Protozoa. But there are means of combating these retrograde
changes should they occur, and they are more likely to take place, in my opinion, under conditions passive than of active
storage. Moreover, the outstanding fact remains that in relation to danger to health, over storage is believed to be impossible.
It frequently happens that water istakeninfor storage purposes in high flood, when it is of very indifferent quality,
and such water, even after passing through the storage reservoir, might yield to most available tests of purity worse
results than the river water, which by this time had become clear and comparatively pure. But this only points to the
desirability of judicious selection of raw water for storage purposes, and even modern tests are practically powerless
to demonstrate the important changes which take place in a stored water as regards the elimination of disease producing
bacteria. It is quite possible that the outlet water from a storage reservoir might, on a given day actually yield worse
results as judged by original and analytical data, than the raw river water'of that day; yet the former water might bo
quite innocuous, whereas the latter water might contain the specific germs of disease.
Undoubtedly from the epidemiological point of view, apart from the questions of cost and pumping, the storage
reservoirs should be so worked as to give each drop of river water abstracted for water works purposes the maximum
number of days detention in store. For example, given a single reservoir holding 65 days' supply it would be undesirable
on epidemiological grounds to use raw river water for 300 days of the year, and during the remaining 65 days' water which
had been stored for periods varying from 300 to 365 days (passive storage).'-
The London Equalisation of Rates Act, 1894.
The Equalisation of Rates Act provides that the London County Council shall in each year
form a fund equal to a rate of sixpence in the pound on the rateable value of London. The contribution
from each parish to the fund is to be in proportion to its rateable value. The fund thus
formed is to be distributed among the sanitary districts in proportion to their population. Where a
sanitary district comprises two or more parishes, and the aggregate of the contributions from such
parishes is less than the grant apportioned to the district, the difference shall be paid out of the
fund to the sanitary authority, of the district, and no payment towards any equalisation charge shall
be required from'any parish in the district.
Subject to the above, when the contribution from a parish is less than the grant due, the
difference shall be paid out of the fund to the sanitary authority of the district forming or comprising
the parish; and if it exceeds the grant to the parish, the Council shall, for the special purpose of
meeting the excess, levy on the parish a county contribution as a separate item of the county rate.