Los Angeles herald. [volume] (Los Angeles [Calif.]) 1890-1893, 1891-10-12
METHODS OF SEWAGE
An Interesting Paper on the
Subject.
Three Processes Now in Gen
eral Use.
None of Them Perfect in the Opinion
of Experts.
DR.. Thresh's Recommendations to the
Congress of Hygiene and DemOgra-
ply at LondOn-Valuable
Suggestions.

congress, DR.. Thresh asked this ques-
ton:
"Do any of the processes mentioned,
or any combination of such processes,
enable us to get rid of our sewage in
such way as to give rise to no nuisance,
cause 10 danger to health, and this at a
cost sufficiently reasonable, considering
the Importance of attaining such re-
sults?"
In the opinion of most experts at the
present day, the only answer that can
be given to this enquiry is an emphatic
negative.
We can see this from a brief considera-
ton of those methods that are now in
use; they may be divided into three
classes:
l. Lime processes.
2. Processes in which lime is not
used.
8. Irrigation.
l. The first OF these classes may be
briefly disposed of; the lime is used
either alone or i'll combination with
aluminous salts, or, as in Hanson's pro-
cess, with the so-called sulphurous
powder. In each of these cases a good
effluent is the only thing aimed at, as
the sludge is worthless.
1t is also worthy of notice that where
lime has been used to precipitate, it
must also be added to press with I'm
process, in which herring brine is added
to the lime with view OF sterilising the
sewage.
2. Processes in which lime is not
used. The best known of these is the
A B G, in which the sewage is precipi-
tated by mixture of clay, alum and
charcoal, with little blood. A clear,
inodorous and tasteless effluent is pro-
duced, and the sludge is pressed without
lime, dried and ground. 1t is stated to
contain 8 per cent. of ammonia and 5
per cent. of phosphates. Both of these
/ figures seem high if the manure sold
has not been enriched by ammonia or
phosphate. Much has been said for
and against this process. At any rate,
it is better that the sludge, whatever it
contains, should go on the land, than
have to be thrown away, as some times
happens in the lime processes.
The International Sewage Publication
company precipitate with mixture
OF magnetic oxide OF iron and salts
of iron, alumina, and magnesia. The
effiuent is further purified by passing
through a filter bed of gravel and po-
larite. The sludge, when pressed with
out lime, and dried, readily crumbles
into fine powder, and should be OF
some value as manure.
Webster's Process or Electrical Treat
ment-The sewage travels along trough
in which are placed iron plates con-
nected with the terminals of dynamo.
Water is decomposed, and some also
passes into solution, precipitation takes
/ place, and the etfluent is said to be
good.
8. Irrigation-In cases where land is
cheap and of suitable character this
plan may be adopted with success. In
most cases the first cost is great, and so
is the cost of maintenance. 1t is dis
puted point as to whether parasites may
not be communicated to the animals
feeding from the crops raised off
unfiltered sewage, and it is certainly not
advisable, as is sometimes done, to
irrigate fields with untreated sewage, so
that pools of unputrefying matter are
formed, round which cattle are feeding.
In the case of London it is practically
impossible to get land enough to deal
with the enormous volume of sewage,
which is very greatly increased in wet
weather, and though it may be said that
this is in great part rain water, yet the
dirt washed off the streets and the fun
gus torn from the sewers by the in
creased volume of water will render
some method of treatment as necessary
as if it were ordinary sewage.
And now to come to the subject of
this paper; the treatment [ have to lay
before you has been practically tested
by me at experimental sewage works at
Seyton. | have no very novel sugges-
tions as to the precipitation OF sewage,
the originality of my method depending
on the manner in which the sludge cake,
produced by any precipitation process,
may be converted into marketable pro-
ducts.
Let us consider the ordinary compost
ton of sludge cake; it is roughly in 100
parts:
Water. Observation-Disclosures. 80. - 25
Inorganic matter containing phosphates 20
Combustible matter containing nitrogen. SIS
The above figures refer to sludge cake
that has been dried by exposure to the
air for some days.
Now suppose we could afford to distill |
the cake in gas retorts, we should save |
the ammonia; but it could not paw I'M
less one could produce a sludge very
rich in ammonia, and then it would be
salable without further treatment.
There is, however, cheaper way of dis
tillation than that l have lust men
toned. A. Mr.. Rees Reece, in patent
good many years old, described a
method of obtaining tar, ammonia.
acetic acid and inflammabe gas from
peat; this process was in sue
cessful operation for some time
He employed kind of lime
kiln with forced draught, connected to
a series of condensers. The operation
was conducted in such manner that
the material in the lower part of the
furnace was kept in active combustion
its heat distilled the material directlv
above, and this in its turn gradually de-
scended to serve as fuel for the succeed
ing change. Thus nearly the same effect
was produced as if the peat had been
distilled in retorts, except that, instead
of carbonized matter, ash was obtained
l have employed the same method for
dealing with sludge cake, and have made
experiments on sufficiently large
scale to show the possibility Of
practical working. A furnace was SET
up, built of boiler plate, lined with
brick, and fitted with a fan and con-
densers. This was kept burning for
= 700 xuooEo oop&;vro.,e1vx p