Medical Officers of the Army of India.
For example, we have seen that for a sewage composed of units of 5 oz. solids
(European's) with a dilution of 3 gallons, aggregating with urine about 3,250 gal
-lons a day, we must provide an upward filtration bed of a capacity of 6,000 gallons
to allow space for the filtering material and to ensure at least one day's sojourn
in the tank; we have also to provide a filtering capacity (2nd stage) for 3,250
gallons of effluent daily—or, as previously stated, this must be increased if dilu
-tion is increased. Now take the case of native troops; solid excreta equal to 10 oz.,
plus urine, 30 oz., diluted with I gallon of water per head, gives for 1,000 men, from
1,250 to 1,500 gallons of sewage. We have to arrange for a sojourn in the I st
stage of 6 to 8 days, therefore we must make the capacity of our first upward tank
capable of holding, say, 9,000 to 12,000 gallons, i. e., it will have to be from half
as large again to double the size of the upward bed provided for a similar number
of men in a European regiment. The smaller size would prove ample, in the
writer's opinion, i,e., provision for 9,000 gallons will suffice in the first stage for
a dilution per capita of 1g a l l o n ,
p l u s
a b l u t i o n - w a t e r . B u t o n l y s o m e 1 , 2 5 0 t o
1,500 gallons of hydrolysed effluent will pass over daily, and our downward filter
capacity will only have to accommodate this quantity and therefore will be
only half that required for an equal number of European troops. Thus
this system provides an easy solution of the difficulty, if the men go to the installa
-tions, i. e., there might be at least two, to accommodate the sewage of half a
regiment in each.
The sewage of a bazaar affiliated to a cantonment should be dealt with in
the same manner, and I must reaffirm the conviction that all this can be done, if
the authorities grasp the urgent need for reform.
A few words may be added as to the reasons upon which the writer has based his
opinion as to the relative efficiency of the septic tank and the upward filtration bed (after
Scott Moncrieff's model).
In a trial of the two apparatus side by side extending over four months, with a
highly concentrated sewage which, in comparison with English sewage, may be called
diluted sludge (see analysis previously given Part II). the results of the hydrolytic action in
t he upward fi l t er bed were uni forml y superi or t o t h o s e o b t a i n e d f r o m t h e s e p t i c t a n k , n o t o n l y
in the perfect solution of sludge and suspended sold, but in the diminution of the albumi
- n o i d a m m o n i a . I t m a y r e a d i l y b e u n d e r s t o o d t h a t t h e i m m e n s e e x t e n s i o n o f a r e a t h r o u g h
which the raw sewage must make its way against gravity, by the introduction of anaërobic
cells (in the form of old pots and tins and coarse porous material) affords a better
nidus for the specific action of the anaërobes, which can work to better advantage when
thus spread out, and provided with coigns of vantage, which ensures to some extent the
necessary selection of different organisms at different levels. One cubic metre of coarse
gravel, it has been calculated presents an aggregate superficial area of 56 square metres;
this extension would obviously be less with coarser material, but still it would be very
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