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APPENDIX I.
REPORT ON THE WORKING OF THE SEWAGE INSTALLATION AT THE KING
INSTITUTE OF PREVENTIVE MEDICINE.
By the SUPERINTENDENT.
1. The sewage works and the farm connected with it, which are the subject
of the present report, were devised by Lieutenant-Colonel W. G. King,
then Sanitary Commissioner, with the idea that, whilst they should prevent all
nuisance arising from the institute sewage, they should also be of use in deter-
mining experimentally the best methods of disposal and utilisation of sewage in
India, especially those methods most suitable to Municipalities and most valuable
to ryot cultivators. Apart therefore from the demonstration that a sewage could
be disposed of easily and without nuisance, the main question which the system
had to determine was whether, agriculturally, filtered sewage had advantages to the
ryot over unfiltered sewage. This question has been answered in the case of the.
institute Sewage in the negative, but, as will be seen later, this cannot be applied to
all sewage, and the working of a sewage plot in connection with Government
House, Guindy, has shown that here treatment of the sewage is a necessity, not only
to prevent nuisance in its disposal, but in order to get the benefit of its manurial
value agriculturally.
2. It will be desirable, before describing the results of experiments with this
system, to outline briefly the general principles of the disposal of sewage by bacterial
methods.
3. 3. It will not be necessary to go into the various steps by which such methods
have been built up or modified in the light of experience. It will be sufficient for
the purpose of this report if we indicate broadly what is at present known on the
subject.
4. If sewage be run directly upon soil, a very large area of land is required
to dispose of it, owing to the fact that the organic matter in suspension would, if
in any quantity, quite prevent the growth of vegetation, or indeed allow of any
other process but ultimate putrefaction of such matter in situ. Could the organic
matter of sewage be first broken down into chemical bodies more suitable for plant
life, the question of its disposal would be enormously simplified.
5. The bacterial methods have as their object the achievement of this result.
( a) In certain systems of bacterial treatment of sewage, the sewage is run
direct upon coke beds of special construction, where, as it trickles down, it is
subjected to the action of organisms (aerobes), which convert all the contained
organic matter into simple non-putresible compounds. Even such resistant sub-
stances as paper are said in - these beds to undergo rapid solution. As a rule,
however, the direct treatment of sewage by the aerobic bacteria of a filter bed is
rendered impossible by the fact that the solid matter of the sewage sooner or later
clogs the filter.
(b
) it is here that the function of a septic tank comes in. It has been found
that, if sewage he allowed to remain undisturbed one or two days in bulk, most
powerful fermentative changes go on, which result in the solution of all solid
organic matter. These fermentative changes are the result of the action of
anaerobic bacteria, or those which flourish best where oxygen is absent. A septic
tank is merely a closed receptacle devised to allow sewage to be subject to this
fermentation. As it leaves the septic tank sewage may quite well be as full of
bacteria, if not wore so, than when it went in, but it is free or almost free from
solid matter.