13. The amount of water pumped from the well which supplies the institute
averages 10,000 gallons per diem. The great bulk of this apparently enters the
closed sewerage system and enters the septic tank or is allowed to pass direct upon
the farm, but only 5,000 to 6,000 gallons are recoverable (vide later). The major
portion of the sewage is derived from water used in wahing down the calf stalls,
but there are in addition several latrines and other feeders, etc. The sewage as
might be expected is a dilute one and comparatively free from human excreta. As
seen in. the sewers it is a thin fluid containing particles of dung, paddy husks, etc.
Though not objectionable when freshly collected, it, quickly becomes so when kept.
In the septic tank it, becomes covered with a frothy greyish brown scum which
contains a good deal of solid matter. Collected and observed in the laboratory the
fermentating action is beautifully displayed, masses of material alternately rising,
and falling as bubbles of gas form or detach themselves. After passing through
the septic tanks the sewage is a darkish clear fluid containing black amorphous
. granular matter. After filtration the effluent is slightly turbid but has practically
no odour, and kept it does not become objectionable.
14
14. For demonstration purposes nothing can more strikingly illustrate the value
of the bacterial method of sewage disposal, and in the perfection of its results the
present installation has subserved its object.
15. An instructive contrast in this respect are the arrangements for the disposal
of sewage at Government House. This is a concentrated sewage containing much
!
human excremental matter, soap, etc. It is received direct from an open ehannel
without any septic tank. There is a small sand filter, and a plot of land for the
utilisation of the sewage in growing lucerne and guinea grass. In a very short time
it was found necessary to leave the sand filter severely alone as any attempt to get
the thick sewage through this led to the greatest nuisance from the odour and the
necessity of constantly removing the sand which had then to be buried. The two
overseers who have at different times had charge of the farm have, in self-defence,
found it necessary to allow the solid matter to sediment and bury this in pits.
Allowed to run direct upon the beds the crude sewage has to be used with the
greatest care to prevent clogging of the soil, nuisance, and death of crops.
16. Here the disposal of sewage without nuisance is not automatically carried
out, but is managed only by constant attention and by such an archaic method
as burying solid matter in pits. The use of a septic tank, which probably would
not, as we shall see later, need to be a large one, is in this case therefore highly
desirable.
17. Though the installation has done all that could be desired in disposing of
sewage passed into it, yet there are certain matters in its working which are
worthy of note, as they have an important bearing on the putting up of similar
installations in India.
18. The septic tank has a capacity of about 1,600 cubic feet or 10,000 gallons
and the reservoir of about 1,200 cubic feet or 7,500 gallons, the total capacity of the
system being about 17,500 gallons. This is far more than is necessary for the
institute sewage even were the quantity of this doubled, a sojourn of 24 hours in
the tank, even in Europe, being now considered sufficient, whilst at the temperature
of Madras fermentation is certain to be far more rapid in its action.
19. The filter beds again measure 37 feet by 35 feet and are 4 feet deep.
These are even more out of proportion large to the amount of sewage than the septic
E tank, though I have no doubt they were arranged to suit requirements judged by
English standards.
20. In the intensely dry conditions of India, where, especially in porous soil,
an immense amount of fluid can soak in leaving scarcely a trace, a much smaller
sewage installation than is generally supposed requisite will probably be found
ample for institutions, small municipalities and so on.
21. To draw conclusions from the present experiments regarding sewage
disposal on a large scale would not however, I think, be justifiable, and this is
especially so where the question of the utilisation of sewage is at stake.