6
(c) Though the solid matter has been removed, it is only converted into
matter in solution, and the effluent from a septic tank is therefore subject
to renewed putrefaction, with all the nuisances of the original sewage. The effluent
can, however, now be run without difficulty upon coke beds, where all organic
matter is finally reduced to simple inorganic compounds such as carbonic acid,
nitrates and so on.
(d) This effluent from the beds is, or ought to be, not only free from the
possibility of further putrefaction, so that it can if necessary be allowed to run
into a stream or river, but its constituents are more adapted than those of the original
sewage for the growth of plants, and, subject to certain modifying conditions, its
manurial value is increased.
6. The general arrangement of the sewage system under discussion is shown in
the accompanying sketch map. The "farm" occupies a small depression, which
debouches upon the flat land along the bank of the river Adyar. The sewage from
the institute enters the septic tank at "A". A is the septic tank proper and B a
storage reservoir for use in working the filter beds. C and D are two Dibden
filters. At "B" there is a bye-pass, by means of which crude sewage can be
passed directly upon the farm, and at E there is a model of a Massachusets sand
filter. Plot 3 (shown on the plan) has for over a year received only crude sewage,
plot 2 septic tank effluent passed through the sand filter, and plot 1 septic tank
effluent which has been filtered through the Dibden beds.
7. The farm has been run by an overseer on Rs. 40, and four menials. The
ground has been levelled, and terraced, and cleared of jungle. Up to quite recently
the farm was utilised strictly for experimental purposes, the quantity of sewage
run on, and the produce from the different beds being carefully weighed, and the
amount recorded by the overseer— ride statements.
8. By April 1906 the experiments regarding the utilisation of sewage, as far as
could be shown in the installation under review, seemed to be sufficiently complete,
and had it not been that at this time the farm was invaluable to the vaccine section
in helping it to tide over its season of danger, the working of the farm proper
might well have been dispensed with.
9. During the hot seasons of 1903-1904 and 1904-1905 the manufacture of
vaccine had been conducted with such difficulty that it was becoming doubtful
whether a reduced output during certain months should not be asked for. At first
these difficulties were considered to be due to the direct effect of the high tempera-
ture on the vaccine, hut it gradually became evident that the trouble was almost
entirely due to want at this time of green matter in the diet of the calves.
10. To help meet the hot weather of 1906-1907, the farm has been made sub-
ordinate to the much more pressing and important needs of the vaccine section,
and the staff have been employed in raising crops, much larger than could have been
done by the sewage alone, by means of irrigation from the river, manuring and
ordinary agricultural operations. The whole available area of irrigable land has
been utilised in this way, as shown in the plan, and on an average close upon 100 lb.
of green cholam, outakiri and lucerne given daily to the calves. So long as water
remained in the upper portions of the river, plots VI, VII and VIII which are
used as quarantine grazing ground were kept irrigated by the sewage farm staff to
aid in the general scheme for maintaining the vaccine production.
11. So helpful has the farm been in this way that if further experiments be
uncalled for, the farm can scarcely now, without other arrangement being made, be
given over without much detriment to the vaccine section, since the calves derive
from it during the hottest months the only green grazing and the only green cholam
obtainable, the latter not being available for purchase except at a prohibitive price.
In addition to the institute sewage works the staff have worked those at Government.
House, Guindy.
12 The installation, we have already remarked, had special application to
special conditions in India, but it was intended in the first place to dispose of all
nuisance connected with the institute sewage.