Explanation of Plate I.
The modified Scott-Moncrieff installation as used in the Simla experiments;
specification for 1,000 Europeans, or for from 3,000 to 4,000 gallons of sewage—
Fig. I. Plan G is first upward filter bed to which the sewage flows. H. H. H. H. repre-
sent the 4 downward filter beds, the floors of which are laid with herring-bone
drainage channels and require a gentle slope to the outlet pipes.
N.B. —For Native troops and where sewage is not removed by drains, a mixing tank
(not shown) must be erected, as an ante-chamber to G (see text).
Fig. 2. Section of above, showing sewage inlet pipe running to bottom of G; the sewage,
after hydrolysis, is forced upwards through the grating, to the overflow channel
in the walls of G to discharge on to filter H, down through which it flows to outlet.
This latter process may be either in the form of "contact" (the filter filling and
being immediately discharged), or of continuous down filtration, the first efflu-
ent being thoroughly distributed over the filter and being allowed to run through
and escape forthwith, to the channel conducting it to the cultivation ground.
The latter involves a 'cheaper structure and less attention, but the choice depends
on the stage of hydrolysis
I have not figured the simple automatic arrangement for tipping the effluent (from G)
from one filter, when full, to the other. This may be accomplished by means of
a well at the exit end of the filter, in which a float rises with the effluent. and
moves a lever, which (by a connecting rod) tilts the tipper which is balanced
under the effluent discharge pipe from G—a device of Mr. Donaldson's applied
to the installation at the Presidency Jail. Nor have I shown any form of distri-
buting apparatus; they are legion and are figured in all the books on the subject.
Fig. 3. Cross section of first upward bed; needs no detailed explanation. There is always
a permanent water-seal of about 2"—3" above the clinker and between its upper
surface and the exit pipes or notches, which conduct the effluent to a drain in
the masonry wall, which runs round the top of the two sides and the front of
tank G and discharges by a pipe on to the filter beds H.
The apparatus thus figured (1, 2, 3) is specified for the sewage of 1,000 troops (Euro-
peans), if the dilution allowed per capita be 3 gallons (giving a total of a little
over 3 000 gallons); each filter on the plan will accommodate about 1,000 gallons
when plenished with clinker. It is well to have one extra filter in reserve, to
give each a periodic rest in rotation, if necessary. Two filters each to accom-
modate half the total volume of effluent may however be substituted. It the
dilution of the excreta amounts to more than 3 gallons per head, the filter-area
must be increased accordingly, but the hydrolytic tank G need not be enlarged.
The cost of the whole apparatus as specified has been calculated (on the basis of the
Military Works Hand-book for Meerut) as Rs. 2,254, or £150. (This does not
include the cost of the burnt clay or clinker.)
Figs. 4 and 5. Show the same apparatus where the tank G has to be sunk in an excava-
tion, while the effluent therefrom is discharged into a sump J and raised by Per-
sian wheel, 15 feet and discharged on to filters above ground level. A pump
might preferably replace the Persian wheel, and inasmuch as it would raise the
effluent to a greater height, it would allow of the first tank G being at a lower
level and increase the fall for the drains and sewers from the Barrack site.
This device is for very flat sites.