The age-herald. [volume] (Birmingham, Ala.) 1897-1902, 1902-04-10

ly so within the last five years. He esti-
mates however that in 1910 the two
trunk sewers will be serving a population
of 100000. This estimate was considered
low by several of the commise ion who
discussed the matter. BY this time the
sewers will be taxed to their full extent
and If the city continues to grow new
ones will have to be built. This popula-
tion contiguous to the sewerage system
would probably mean total population
for the county of from 100000 to $50. 900
people.
Mr.. Gray estimates that In the year
1903, If the sewers be finished by that
time, they will be serving a population of
105,50O. In 1910 a population of 14S.5OO. in
1920 population of 232, 600, in 1880 a popu-
lation of 34S,OO0 and half a million in 1910.
SEVERAL METHODS
OF SEWAGE DISPOSAL.
Mr.. Gray discusses in detail the various
methods of sewage disposal, viz: Crude
disposal, disposal by chemical precipita-
tion and disposal by irrigation or filtra-
ton.
Crude disposal is discharging the sew
age In its crude or unclarified state into
some water course, as is done now with
the cityS sewage. This Is the cheapest
as we'll as the simplest method of dispos-
ing of sewage, but requires a large
stream to sufficiently dilute it.
Chemical precipitation consists In col
lectfng the sewage in tanks and mixing
certain chemicals with it, which precipi-
tates all matter in suspension and a por-
tion of the impurities in solution, leaving
a comparatively clear and odorless af-
fluent which may be discharged into any
stream whose waters are not used for
domestic purposes.
Irrigation or filtration upon land con-
sists in discharging the crude sewage
upon the earth. the coarser material be-
ing left on the surface of the ground
while the finer portion of the sewage
passes into the earth to a greater or less
depth. The water descends still further,
coming in contact with the air in the
earth. The impurities which the sewage
contains are thereby oxidized; that Is,
purified by the action of bacteria, which
are dependent for life upon the oxygen
contained in the air. The purified liquid
may descend still lower OF 1t may be car
ried off in underground drains laid for
that purpose. The insoluble matter con-
tained in the soil is also oxidized and
mingled to fine powder. There is a dis
In the former only so much sewage is
applied to the land as will be beneficial
to the vegetation. In filtration the guam
tity is governed by the amount the ma
terial will purify.
RECOMMENDS THE
SEPTIC SYSTEM.
A somewhat new system, and the one
which Mr.. Gray recommends be first tried,
is what is known as the septic system.
This consists of collecting the sewage In
an underground tank usually air tight.
and from which the light is excluded. The
tank is built of masonry and is designed
to hold one or more days foW or sew
age. The sewage is retained in the tank
twenty-four hours or more, during which
time ii undergoes more or less fermen-
tation, which Is caused by the action OF
bacteria in the sewage. A scum from two
to three inches in thickness soon rises to
the surface More or less of this scum
eventually sinks to the bottom, portions of
which are again carried to the surface by
the formation of gases in the material,
which gases are the result OF the working
of the bacteria.
The repeat ed rising and settling of this
scum results in the deposit of fine pow
derry mass at the bottom of the tank. The
effect on the sewage Is to reduce and sepa-
rate to a great degree. the solids In sus-
pension from the water contained in the
sewage, forming a fairly clear effluent
This effluent is drawn on from the tank
and run into filter beds.
The beds are underdrained. and the un-
derdrains are provided with gates, and