The record-union., 1894-02-12


large surface, so that it may be oxygen
ated.
Underground conduits connect the
tanks with the sludge pumps, by which
the sludge is pumped from the settling
tanks to the sludge well, and from this it
is drawn up into four sludge receivers by
exhausting the air from them. They are
each four feet six inches in diameter and
twelve feet six inches high.
When the receivers are full the valves
are reversed and air is pumped into them
at pressure of 100 pounds TO the square
inch, which forces the sludge into pair
OF filter presses. The air pumps, which
are used alternately for exhausting and
forcing, have cylinders six inches in
diameter by siX-inch stroke.
The filter presses press from the sludge
about so per cent. of the moisture; the
residuum taking the form of hard, flat
cakes of black color, free from smell,
and are removed by hand. The dried
cakes are atterward ground and sold as
native guano, and finds ready sale at
about $40 per ton. The same raw ma
terial treated in somewhat similar man
ner was spread upon our city plaza last
summer to help the grass, when trampled
on so much by the crowds attending the
evening concerts. OF the hundreds who
sat upon the grass none suspected its
presence.
SEWAGE FILTERATION WITH SPECIAL
AERATION.
In paper read before the Institution
of Civil Engineers for 1898 81, Sidney h.
Lowcook gives the results of numerous
experiments carried on III Xperimental
filter tanks for the treatment of screened
sewage, after having been treated with
lime and alum III the precipitation tanks.
4 Of III
open joints was laid along the center of
the bottom OF the tank which was covered
with a siX-inch layer OF broken stone; on
this was laid fifteen inches OF stiff clay,
ashes and sand.
The next layer consisted of six inches
OF broken stone. similar TO the bottom
layer; in the middle OF this was three
quarter-lnch iron pipe closed at one end
and pierced along both sides with seven
slxteenth-inch holes six inches apart.
The outer end of this pipe was connected
with the discharge pipe of small air
compressor. The air was discharged into
the perforated pipe in the layer of rough
stone, which served to distribute it
equally through the filter. After the
tank had been in active operation for
thirty-three days, running at the rate of
leo, 900 gallons per acre, analysis showed
that 99.l per cent. of the free ammonia
and $50 per cent. Of the albuminoid
ammonia was removed. the eff1nent being
perfectly clear, colorleSs, odorless and
tasteless.
1t appears from the experiments that
the filters do not clog so quickly when air
is being supplied to the body of the filter
as when it is not; and this is probably due
to the matters which produce the clogging
being broken UP and destroyed in pres
ence OF the air directly they pass below
the surface. The advantages Of this sys-
lem are that soil similar to the gravel beds
east OF the city may be used, the air and
soil piped producing one OF the best fl
tering systems at low cost. and giving re-
suits as satisfactory as high priced plants
ELECTRICAL PURIFICATION.
The London Engineer discussing the
sewage publication problem some time
ago, says: "The first of the processes
claiming our attention is the electrical
process. Plates of wrought iron are
placed in tanks containing sewage, and a
current of electricity is made to flow from
plate to plate through the sewage. The
result is that very tolerable etfiuent is
obtained. The theory of the process is
simple enough. In the first place, the
iron plates corrode, and the oxide OF iron
acts as a purifier in a way not. perhaps,
fully understood. although more than
one plausible explanation has been ad-
Vanced.
''But this action of the iron is only Sec
Ondary. The efficiency of the process is
mainly due to the decomposition Of the
sodium chloride-common salt-which all
town sewage contains to the extent of
fifty or sixty grains in the gallon. This
salt goes away from our dinner-tableS.
All but a small portion of the contents of
our saltcellars ultimately finds its way
into the sewers. The electric current de-
composes the salt: the chlorine is set free
and acts as a disinfectant. 1t appears if
salt were not present in the sewage the
electrical process would have little or no
value.
In a paper on sewerage purification
by electrical means, read before the Insti-
tute of Technology at Boston, the writer
saws: 1.-The organic matter is the most
difficult to destroy or remove, and is the
part most dangerous to health. The oXi-
dation Of the organic matter can be ac-
complished by one method only, chemi-
cal action, whether that be produced by
the addition of chemicals or
electrolytic action. 4 filter is sufficient
when employed internationally, for then
the filter becomes aerated-i. e., charged
with atmospheric oxygen during the pc
riods of rest-and this oxygen destroys
the organic matter in the sewage. OXi-
dation can only be accomplished more or
less eXpensively by chemicals.
The electrical method differs from the
above methods in two points. First the
oxygen and chlorine that produces the
burning up of the organic matter is made
by decomposing. by the aid of a current
of electricity, the water and chlorides of
the sewage itself. Second, the oxygen
and chlorine act much more powerfully
at the moment OF their formation, being
set free in what is called a "nascenV
state.
After treatment the liquid is cleared
and filled with particles of sludge, which
deposit quickly when allowed to rest.
The sewage is pumped into a chute
eighteen inches square, 400 feet long, and
filled with iron plates in groups of fit-
teen. a large mum Der of which are con-
nected in multiple, or parallel from Sec
tions in series with each other. A space
of two or three feet in the chute between
sections is sufficient to prevent undue
leakage.
The six sections take approximately
three volts per section. current 800 am
peres. The consumption of iron plates is
from one to two grains per gallon of sew
age treated if cast iron is used. The We
locity in the chute is about ten to twenty
tive feet per minute, or from 1000 to 10000
gallons per hour. The color shows no
apparent change for twenty Or thirty feet,
then numerous bubbles come to the sur
face, and further on these have brown
color and near the end the liquid is dark.
At points IN the chute the current runs
over or under an adjustable board, Civ
ing it thorough mixing and complete
control of the level in each section OF the
chute. AS the churning action III the
chute has liberated all the hydrogen, the
precipitate settles at once, and in two
hours the clear effiuent may be drawn off
and discharged directly into any con-
venient stream.
The estimated cost of 100000 gallons
a day works, with duplicate engines and
dynamos and iron plates, lasting ten
wears, is put at $780, 900, or 81 per inhabi-
tant. the labor of four men and coal max
sLcs,,t s.l5 do 4