8
22. Where small installations such as those at the institute or at Government
House are concerned, experience makes it very doubtful whether the utilisation of
the sewage is worth the labour expended upon it since if produce is required it can,
as shown in the present instance, be obtained with infinitely greater ease and
cheapness by simple irrigation from a well or river.
23. The reason is obvious once the practical working of an installation is taken
in hand. It has already been remarked that the conditions in India are such as
tend to make the volume of sewage less than it would be in Europe. Not only so,
but wherever the sewage is allowed to come in contact with the soil, it is sucked
up in astonishing quantities. Thus not only does every leak in the system tell
in a way it would not otherwise do, but in the filter beds, and in the distributary
channels, the loss is enormous. Starting with what seems a considerable inflow
into the sewerage system, it is remarkable how little ground it is possible to
irrigate. Then, again, to irrigate dry and porous soil in India very large quantities
of water are req uired.
24. The result of this is that sewage, which on. account of its constituents
would suffice to manure a considerable area, is capable of irrigating only a very
much smaller area.
25. The appreciation of these conditions suggests their remedy and the
combination of a sewage outflow with, wells water irrigation is au experimant wells worth
trial.Though the institute sewage on account of its nature is not very dilute
adapted to such an experiment, yet in the future it i s proposed to utilise the sewage
not by itself, but in conjunction with irrigation from a large well which was found
buried in the jungle which originally covered the greater portion of the farm.
With two bullocks the whole area could be irrigated (vide sketch map) and all the
manurial value of the sewage utilised in producing a patch of grazing ground which
would be of great use to the vaccine section.
26. In the case of the institute sewage the cultivation of crops is not necessary
to avoid nuisance, since the effluent, with practically no attention, can be allowed
to find its own way into the soil and being non-putrescible it causes no nuisance.
27. In the case of Government House the cultivation of crops is at present
necessary, though it is doubtful if it is economical, but it would not, be necessary
n o r I t h i n k d e s i r a b l e t o c u l t i v a t e c r o p s i f a p r o p e r b a c t e r i a l s y s t e m p r o d u c i n g a
non-putrescible effluent were put in existence. if crops are desired they should be
grown where the y can he done most economically. sewage having a manurial
value, it is desirable of course to utilise it, but if this is done it should be carried
out in conjunction with well irrigation.
28. Whether filtered sewage gives better results agriculturally than crude
sewage, which was the chief question the experiments were designed to answer, has
been put to the test by irrigating continuously for over a year three exactly similar
plots of ground, plot 3, plot and plot 1, respectively, with crude sewage, sewage
passed through the septic tank and a sand filter, and sewage which had been
through the tank and Dibden filter beds. Neither by inspection, nor as the result
of the produce given, was any superiority noted. if anything the superiority lay
with the crude sewage, probably because here wastage was less and more actual
water reached the crops.
29. Table I gives in detail the conditions for one month in the dry weather.
Table II gives the crops grown in one month (June) with the aid of a small
picottah worked by two men also in the dry weather.
30. In the case of the institute the crude sewage was sufficiently dilute not to
clog the soil, and its quantity insufficient to lead to stagnation. It is quite certain
that the sewage from Government House could not, in an untreated state, have
been run on to grass beds, as was the institute sewage, without giving rise to
grave nuisance.
31. The question of the passage of pathogenic organisms through the septic
tank has not been touched upon, since the . subject is one which has been taken
up by many workers and one which did not seem called for in the present instance,