St. Tammany farmer. [volume] (Covington, La.) 1874-current, 1915-09-04

lively small size of the sanitary sew
ers of the separate system, the air
In them IN much moro frequently and
completely changed by the daily fluc-
tuations in the depth of sewage and
by the currents Of air through ordi-
nary ventilation openings. Hence.
in separate systems. ventilation is
easier and more perfect.
20. In case the sewage has to be
purified the separate system Is more
economical. because only the sani-
tary sewage need be treated. the
storm sewage being discharged into
nearby natural watercourses.
80. In small cities, and in large
portions Of large cities, the storm
water can usually be carried some
distance in the guetters. and then re-
moved by comparatively short
lengths Of storm sewers, laid at shall
low depths and discharging into the
nearest suitable natural watercours-
es. In such cases. . separate system
of sewers will usually cost only .
fraction, frequently only one-thtrd,
as much as . combined system. For
small towns, the great cost of COM
bined system would often prohibit
the construction of sewers entirely,
or postpone 1t almost Indefinitely,
we're 1t not that Z separate system
can be built 20 cheaply. On this
account alone, the introduction of
the separate system Of sewers has
been Of incalculable benefit In Ameri-
ca.
81. In cas- the sewage must be
purified, It must be remembers that
tho early how Of storm sewage from
the streets Is foul. to some extent
from the droppings Of animals and
other surface fllth; and 1t may in
some cases be questionable whethe-
this may not require publication in
addition to the sanitary sewage.
80. On the basis Of cost. the sep
arate system is usually the better for
small cities, for suburban and some
times residence districts Of large
where the sanitary sewage requires
treatment while the storm sewage
can be safely discharged into nearby
watercourses. The separate system
has just been recommended for the
city :of Baltimore on this last &C
count
SO. General Description Of Sew
ers-Sewers ~ usually built, are
smooth pipe or masonry conduits. a.
nearly water-tight( ~ practicable,
buried In the ground as deeply as
necessary to serve the adjacent hous-
es and drain other territory tribu-
tary upstream. They are very care
I'M 4AA +~ -
line, Determined by the engineer
who made the sewer plans.
-. Sewage Disposal-There ie
some confusion as to the meaning
which should be given to the term
Sewage Disposal. there being . ten
dency to treat It as meaning the
same thing as sewage publication.
It seems wise to hold more closely
to the strict meaning of the words.
Sewage disposal refers to the
means adopted for disposing Of or
getting rid Of sewage.
Sewage publication is Treatment OF
sewage to rid 1t Of its foul tmpuri-
ties and render 1t harmless.
IS. Chemical Precipitation-In
this method certain chemicals (usu-
ally lime, alum. or iron) are added
to the sewage to precipitate the sus-
pended organic matter, in precipita-
ton tanks.
Sc. Settling Tanks.-These are
for preliminary treatment. some
times given sewage before filtering
1t, in order to get rid Of part Of the
solid matter In the sewage. which
otherwise might tend to clog the
filters. Some bacterial publication
also occurs in settling tanks.
81. Septic Tanks-These tanks
are larger than settling tanks, and
hold the sewage and sludge Tor solid
matter settling in the Tank long
enoug for bacteria to act and to affect
partial publication. This Is also
usually 4 treatment preliminary te
liberation.
80. Intermittent Sand Filtera-
tion-In this method the sewage Is
discharged Internationally. upon the
surface Of sand filters. The sewage
may or may not have flrst pre1imi-
nary treatment In tanks. This is q
very efficient method, and il one OF
the most common 1t present in use
80. Contact Beds-These are al
ters Of coarse material (say 1-S inch
to one inch si1e) with water-tigh4
wallis and bottoms. which are alter
nately filled with sewage. allowed ia
stand full for Z certain contact peri.