The methods available to dispose of liquid sewage in the country are
water-tight cesspools and irrigation.
_Vaults._--Water-tight cesspools should be constructed of hard-burned
brick, laid in cement, and having a similar brick or a concreted bottom.
The inside and outside surfaces of the brick wall should be coated with
a thin layer of cement, and clay rammed in around the wall, to increase
its imperviousness to water. It should be vaulted above, and topped by
a square or round central opening, covered with stone or iron plate.
Cesspools are also made of cast or wrought iron, the joints being made
water-tight. Cesspools must be ventilated by two pipes, one rising several
feet above ground, the other carried to the roof of the house, barn, or
other structure near by. The current will, in most cases, tend down the
short and up the long pipe. The latter may be dispensed with and the soil
pipe of the house act as a flue, provided all branches are perfectly
trapped.
[Illustration: Fig. 6.--Settling chamber and flush tank for surface
and subsurface irrigation of sewage. (From Gerhard's "The Disposal of
Household Wastes," 1890.)]
_Irrigation._--The disposal of sewage by irrigation is by far the best
method now within reach. Two methods are in use, viz, surface and subsoil
irrigation. The first in its most complete form consists in carrying the
liquid sewage to a piece of ground set apart for the purpose and carefully
underdrained. The sewage is allowed to flow over the ground in shallow
channels. The fluid slowly disappears in the soil and enters the drains
as comparatively pure water, which may be allowed to flow into a stream.
For villages this is the best means of disposing of sewage. Those who as
village officials may be interested in this method will find plans of
such sewage farms, together with faithful accounts of their operation and
the results obtained, in the annual report of the State Board of Health
of Massachusetts for 1892, page 559, and same report for 1893, page 563.
Suggestions for its application to country houses are given farther on.
For isolated rural homes, or village homes commanding a certain amount of
ground around the house, the liquid sewage from water-closets, the kitchen
and chamber slops may be disposed of by the simple means of subsoil
irrigation, first described by Mr. Moule and subsequently elaborated by
Colonel Waring.
The system as used at present in its most successful form consists,
outside of the house, of the following parts (see fig. 6):
Two adjoining water-tight receptacles of brick. One of these receives
the sewage from the house and is intended to act as a settling chamber
for the coarser particles, paper, etc. This communicates with the second
receptacle, which receives from it the fluid sewage. This chamber is
called the flush tank and is provided with a siphon. When the fluid has
reached a certain level, the siphon is set in operation and discharges the
contents of the chamber at one time into the subsoil pipes.
[Illustration: Fig. 7.--Subsurface irrigation of sewage: _a_, absorption
tiles (Gerhard's "The Disposal of Household Wastes"); _b_ and _c_, lines
of absorption tiles showing their relation to flush tank (From Waring's
"Sewerage and Land Drainage").]
From the second cistern a system of subsoil pipes laid over a treeless
piece of ground, preferably a lawn, receives and discharges the sewage
into the ground. These pipes should consist of porous tiles, 2 inches
in diameter and about 1 foot long, laid from 8 to 16 inches beneath the
surface of the ground, and with a gentle inclination of 2 or 3 inches for
every 100 feet. The tiles should have open joints not less than one-fourth
of an inch wide. They are laid upon earthen gutters and the joints are
protected above by caps from being clogged with earth. The intermittent
discharge of the liquid sewage is quite essential to the successful
working of this system. If the sewage is allowed to dribble away into the
pipes certain portions of these will become supersaturated with fluid and
others will not receive any; the purification of the sewage in the soil is
thereby rendered imperfect. The discharge of a large quantity of fluid at
one time, besides scouring the system of pipes, fills it more uniformly
and distributes the work to all parts of the subsoil system.
The successful construction of such a plant requires the services of
someone familiar with it, and it is therefore not necessary for me to
do more than call attention to it here as a highly recommended system
for homes, especially in villages, where the proper amount of land is
procurable and where the sewage must be disposed of in a manner both
inoffensive and safe. In any case the soil of such land must be porous,
not clayey and retentive. Those who wish to familiarize themselves with
the details will find descriptions in the Sanitary Engineer for 1883, page
530, by Philbrick; in "The Disposal of Household Wastes," by Gerhard, and
in "Sewerage and Land Drainage," by Waring. The entire plant is said to
cost $200 to $300, the annual expenditures for cleaning, repairs, etc.,
about $10.
The method of subsurface irrigation just described may be too complex
and too expensive where land is abundant and neighboring houses at some
distance. The simpler method of surface irrigation may be resorted to by
laying out at some distance--at least 100 feet--from the house a small
sewage farm where the sewage may flow in shallow trenches over the surface
and slowly sink into the ground. Such an irrigation field must have the
same qualities demanded by subsurface irrigation. Its surface should have
sufficient slope and the soil should be porous, not retentive. The liquid
sewage, including kitchen and chamber slops, is conducted to this field in
a water-tight tile drain and then allowed to flow into shallow trenches.
To avoid the overloading of the soil with sewage at any one place the
main distributing trench should be so arranged that it and the irrigating
trenches branching from it may be temporarily blocked at any point to
divert the sewage into one or more different trenches every day. In winter
the warmth of the sewage will keep it in motion and the filtration will
go on although the field may be covered with snow and ice. The use of the
flush tank as described above would cause a more uniform distribution of
the fluid over the field and make the filtration distinctly intermittent.
The ground between the trenches may be cultivated to increase the amount
of evaporation. If conveniently situated, an orchard may be used as the
irrigation field. It should be distinctly understood, however, that
marketable fruits and vegetables should not be carelessly allowed to come
in contact with fresh sewage, nor should the irrigation field be near the
well unless the latter is fairly deep and tubed or tiled to the surface of
the water.