San Antonio daily light. [volume] (San Antonio, Tex.) 1886-1907, 1894-07-23


feet per second per acre for the
resident portion of the city, and
0 COS cubic feet per second per acre
for the extreme suburban Lortion
of the city. These quantities are
| based on a daily flow of $50 gallons
per capita with 70 people to the
acre in the central, 80 people to
the acre in the resident, and 80
people to the acre in the suburban
portions of the city. The remain
ing half section of the sewer is to
provide for the hourly fiuctuation
in the flow of sewage as well as for
small amount of rain water, and
ground water il any shall find its
way to the sewers. The sewers,
therefore, when flowing full, will
have a capacity depending upon
the part OF the city they are in, of
0.032 cubic feet per second per acre;
O023 cubic feet per second and 00l6
cubic feet per second per acre.
Another important question to
be considered is the disposal of the
sewage.
The three principal methods of
sewage disposal are, by filtration
or irrigation, by chemical preceipi-
tation, and by crude disposal into
some near water course.
Irrigation or filtration through
land, consists of discharging the
crude sewage upon the ground, the
coarser material being left on the
surface, while the finer portion
passes into the earth to a greater
or less depth, depending upon the
fineness Of the particles in the
sewage and the coarseness of the
soil. The water freed from the mat
ter in suspension, descends still
further into the ground, where
it comes in contact with
the air contained in the
earth. The impurities which it
contains are thereby oxidized, that
is, purified by the action OF the
bacteria dependent for life upon
the oxygen contained in the air.
The purified liquid may descend
still lower, or it may be carried off
in underground drains laid for that
purpose. The insoluble matter re-
tanned in the soil is also oxidized
or decomposed by slow combus-
ton, and thereby reduced to fine
powder and mingled with the ele-
ments in the earth.
There is a distinction between
irrigation Ind filtration. Irriga-
ton consists in applying only so
much sewage to the land as will
aid the growth of crops and can at
the same time be purified, while
filtration consists Of putting upon
the land all the sewage the area
can properly purify, disregarding
the effect it may have upon the
growing crops, il there be any.
Filtration may be classed as con-
tinuous or intermittent. A con-
slant application of sewage to the
soil is termed continuous, but when
applied Internationally it is called
intermittent filtration. If the air
is cut off as is the case by cOntinu-
Gus filtration, the bacteria die and
publication is interrupted. II on
the other hand, the application of
the sewage is intermittent, air fol-
lows the sewage through the soil
supplying the necessary oxygen.
1t is therefore found that far better
results are obtained, and that with
less area of land, by an intermit-
tent rather than constant applica-
ton of sewage.
In filtration the quantity APP
piled to given area is governed
by the amount the earth will puri-
fly. Different soils differ greatly in
their powers of purifying; coarse,
sandy or gravelly material being
much better than that which is
fine or compact.
Chemical precipitation consists
in collecting the sewage in tanks,
having just previously mixed with
it certain chemicals, the result
of which is to precipitate all
matters in suspension, and por-
ton Of the impurities is So
luton, leaving comparatively
clear and odOrless effluent which
may be discharged into any stream
without causing nuisance, from
which water is not taken for domes-
ic purposes. The sludge collects in
the form of a semi-fluid mass at
the bottom of the tanks, and can
be drawn off, or pumped out into
beds to drain and dry out, or it
may by means Of filter presses be
deprived of so much of it's moist
ure as to enable handling it in
carts, or otherwise, and can be
used for filling low lands, top
dressing grass lands, or it may be
used as a fertilizer If il is found to