Activated-Sludge Treatment. Page: 1 of 2
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BEST 42 Lt Q'l j
UNITED STATES PATENT OFFICE.
WILLIAM C. XOOkt, OF FORT WORTH, TEXAS, ASSIGNOR TO ARMOUR AND COMPANY, OF
CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.
ACTIVATED-SLUDGE TREATMENT.Specification of Letters Patent.
Patented Jan. 29,1918.
Application filed July 9, 1917. Serial ITo. 179,499
To all whom'it may concern:
Be it known that I, WILLIAM C..Moon, a
citizen of the United States, residing at
Fort Worth, in the county of Tarrant and
5 State of Texas, have invented certain new
and useful Improvements in Activated-
Sludge Treatment, of which the .following
is a specification.
The activated sludge method of sewage
to disposal,.though of comparatively modern
origin and in its infancy, is one which is
well known and constitutes a field of activity
for sanitary engineers in. the effort to sur-
mount present difficulties in its application
15 to a wider range of usefulness and in ex-
perimentation to. increase its efficiency and
economical availability.
Briefly and generally stated, the activated
sludge treatment of sewage consists in con-
20 ducting the raw sewage into and through
aerating tanks provided with means for the
introduction of air under pressure to .the
bottom of the.tank, whereby the air is caused
to bubble up through. the liquid sewage.
25 The passage of the air through the sewage
develops in time microscopic aerobic organ-
isms which in the course of their growth or
by -means of conditions provided by their
growth, oxidize. the collodial and 'soluble
30,solids in the sewage causing them to separate
out as flocculent particles. The treated sew-
age, at the proper stage is run into a settling
tank where it is allowed to remain quiescent
-for from thirty minutes to one hour, and.the
35 solids settle -to the -bottoin as a flocculent
ooze, called activated-sludge.
The remaining liquid content of- the sew-
age. is rendered perfectly clear, white and
odorless. This aluent liquid may then be
40 run off through the sewers to rivers or other
natural channels without injury to fish or
Thenace to the health or comfort of people
living adjacent thereto.
The activated sludge is removed from the
45 bottom of -the tank, to be freed of its water
content, and when dried is available as a fer-
tilizer, containing a large percentage of
ammonia 'compounds and being practically.
free from any:offensive odors.
50 To make the process continuous.and in or-
der to hasten the treatment of the raw sew-
age, it is found advantageous to inoculate
the same upon its introduction to the aerat-
ing tanks with activated sludge from sewage
55 previously treated, whereby the process isreduced in point of time from several days
to a few hours.
The de-hydration of the sludge resulting
from this activated sludge method of sewage
disposal, is the most discouraging problem 60
encountered in the practical- employment
of that method of treating industrial sewage.
Activated sludge, by reason of its physi-
cal and chemical characteristics, is a most
valuable fertilizer, but the economical uti- 65
lization of the sludge has not thus far been
possible owing to the fact that as found in
the settling tank the sludge is light and
flaky, has a specific gravity of ab cit 1.02,
and when siphoned off averages 99.5% of 10
water. By subjecting the withdrawn sludge
to a further settling for from four to six
hours, the water content can be reduced to
96 per cent., but prolonged settling is in-
hibited owing to the fact that the sludgebe- 75
comes septic if maintained too long without
air, the cutting off of the air supply per-
mitting the renewed growth of the anaerobic
organisms and their domination of the. grad-
ually weakening aerobic organisms. 80
For the further de-hydrating of the
sludge, extensive experiments have been
made along the lines of centrifuging, filter
pressing and drying, but none of these have
proven satisfactory, being uneconomical by 85
reason of the time required and high cost of -
installation required for the. purpose.
By the present invention, the activated
sludge, Which is different from ordinary sew-
age sludge by reason of the fact that it has as 90
part of its content precipitated colloids and
large numbers of aerobic organisms and
which .sludge has been recovered from sew-
age quite alkaline in nature or which has
been made alkaline, is withdrawn from the 95
settling chamber and heated to a tempera-
ture of from 300 C. to 400 .C. It is then
treated with an acid such as sulfuric acid,
in amount about four times that required to
neutralize the sludge, and-accompanied by 100
thorough gaseous agitation, preferably by
means of air, although steam may be advan-
tageously used in some cases. The acid treat-
ment results in coagulating the sludge and
producing -gases, chiefly carbon dioxid, 105
which causes the sludge to first rise to the
surface -and then settle, thereby permitting
the easy withdrawal of the remaining liquid,
whereby the total volume of sludge to be
handled-.is dereased by about 90 par cent, U01,254,833.
No Drawing.
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Moor, William C. Activated-Sludge Treatment., patent, January 29, 1918; [Washington D.C.]. (https://texashistory.unt.edu/ark:/67531/metapth1258140/m1/1/: accessed June 22, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.