8
was laid and brought into operation during the year, to augment the supply from
the existing gallery at Arapoliem. The new gallery was found to yield a water
definitely superior in quality to the old one.
Of the ten municipalities which use sand filters, Periyakulam, which, during
the last year, headed the list with a uniformly good record has lost its place and
fared badly this year. The Madras Corporation sand filters have given the most
satisfactory results of all the sand filter installations in the Presidency. Cocanada,
which promised to do well during the first two examinations in 1919, was found,
at the end of the year, to have fallen below the mark and has not since been able
to rise to the original level of efficiency. At Adoni, Salem and Ellore, no benefit
has been derived from the process of sand filtration. The sand filters in the other
municipalities have given indifferent or poor results.
Of the three towns which employ mechanical filters, the proper dosage of
alum, on which the success of this system of purification largely depends has been
lost sight of and doses considerably short of the optimum have been employed with
disappointing results. The filter beds committee appointed in. G.O. No. 1042 W.,
dated 21st May 1914, inspected Chidambaram water-works in February 1920.
They found that in the pressure mechanical filter there, the dose of alum used
was minute and absolutely insufficient, with the result that the raw water passed
through and out of the filter almost unchanged.
The three hill stations supplies were found to be in good order at the first
examination, though samples drawn immediately after the first heavy rains, showed
some signs of deterioration.
Such of the municipalities as depend wholly or in part on wells and springs
yielded very variable results. Kumbakonam, which derives its supply from a very
deep sub-artesian borehole, showed as usual, a high and uniform standard of bac-
terial purity at the first examination, but the second examination conducted in
December last showed evidence of a slight deterioration in quality. The unusually
heavy and incessant rains in the Tanjore district during October and November
1920, evidently accounted for this deterioration.
Jail supplies.—Almost all the jail supplies came in for a great measure of
criticism and in some cases it was found necessary to condemn the supplies without
reservation (vide appendix II). The Inspector-General of Prisons was addressed
specially in such cases to enable him to take necessary steps for carrying out the
remedial measures suggested.
Railway station supplies. —In some of the five stations where municipal water
is stored for supply on the platform, storage in dirty railway reservoirs was found
to adversely affect the quality of the water. In the remaining thirteen stations the
water-supply varied in quality within wide limits (vide appendix III). The railway
authorities evinced a deep interest in the question of their water-supplies and made
definite attempts to follow the suggestions offered for their improvement.
(3) Experiments with chlorine solutions..
In June 1919, Major Quirke, and subsequently the Surgeon-General
with the Government of Madras, desired that the Institute should conduct
experiments to determine whether bleaching powder solutions cannot be prepared
at Guindy and issued to cholera parties for the sterilisation of infected water supplies.
Although this method of water sterilisation has of recent years and especially
during the war, been recognized as the most effective, it was quite a new system
and the details of its working bad to be studied before its adoption here.
Bleaching powder, being a very unstable compound and its keeping properties in
the state of powder being liable to very wide variations, experiments were
conducted to ascertain—
(1) the keeping properties of bleaching powder solutions under different
conditions and in different strengths ;
(2) the bactericidal effect of solutions so stored.