Note: Descriptions are shown in the official language in which they were submitted.
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MEANS FOR ADVANCED WATER TREATM~NT
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Technical Field
5 ~ My invention relates to water treatment devices
and particularly to physicochemical and biological
methods of sewage treatment devices. In the advanced - ;~
waste water treatment process of phosphorous removal
using two steps of lime reaction tanks suspended solids
settled down in the first step lime reaction tank are
collected and pushed back into reaction and flocculation
zone by rake arms~and solids settled down in the second
step lime reaction tank are pumped back into the first
¦ step tank by separate pumps. On the other hand, it is
essential in the biological process of sewage treat-
ment to have high concentration of the activated sludge
and high intensity of turbulence in the aeration
chamber so more sewage can be treated per same volume `
of an aeration tank. But the higher concentration of
~ 20 the activated sludge, the greater amount of suspended ~"
¦ solids is carried out from the activated sludge -~
settling tank. And it is required quite often to ~r~
provide for the second step settling tank to decrease ~i
suspended solids in the effluent. In this case an ;`
additional pump and pipe lines will be required to
recycle suspended solids settled in the second step
` settling tank back into the aeration tank. It is
essential in both cases to eliminate some of the equip-
ment for solids recirculation and consequently to
decrease expenditures.
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Background Art
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The prior art, U.S. Patent ~o. 3,246,7~2,
provided for two settling chambers. Although sludge
return from the first settling chamber is produced
by the action of an aerator, sludge return from the
second settling chamber is produced by using a
separate pump. In case a third settling chamber is
3 needed, an additional pump will be required. So this
, 10 prior art is not as energy-efficient as my invention.
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~ Disclosure of Invention
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In accordance with the present invention,
I provide a waste water treatment apparatus consisting
of a mixing or aeration chamber where mixing or aerat- ~ -
ing means is mounted, and a plurality of settling
chambers adjacent to the aeration chamber and which
work in series. My improved waste water treatment
apparatus possesses the advantage that suspended `
solids settled down in each of the serially operated
settling chambers are returned back into the aeration ~
chamber by the action of the single aerator. The latter
feature is of particular advantage and is a distinct
. 25 improvement over certain prior art apparati because
it eliminates special recycling pumps for each
settling chamber, and consequently reduced capital '
and operating expenses. Another advantage of my
apparatus is that its mixing (or aeration) chamber has
a horizontal sectional area which increases in size
from the bottom to the top, thereby greatly increasing
turbulence in the aeration chamber. The higher
turbulence, the higher biological activity of the'
sludge and higher concentration of the sludge can be
maintained in the aeration chamber. This shape of
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the aeration chamber effects a high degree of waste and
sludge mixing in the aeration chamber with minimum `'
power consumption.
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Brief Description of_Drawings :
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The details of my invention will be described ;
in connection with the accompanying drawings, in ,
which Figure 1 is a schematic vertical sectional
view showing a first embodiment of the invention with ¦
` two settling chambers and improved shape of the j
aeration chamber; Figure 2 is a schematic top plan
view of the first embodiment; Figure 3 is a schematic
vertical sectional view showing a second embodiment
of the invention with two settling chambers working
in series; Figure 4 is a schematic top plan Yiew
of the second embodiment; Figure 5 is a schematic -
top plan view showing a third embodiment of the inven- ~¦
tion with three settling chambers, two of which are
working in parallel and one is in series with those
two; Figure 6 is a schematic vertical sectional
view showing a fourth embodiment of the invention ~ -
with an air-diffuser as an aerator. ~,
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Best Mode for Carrying Out the Invention '
In accordance with the first embodiment of the i;`
invention (Figures 1 and 2), the device of generally
trapezoidal configuration includes housing 1 with
number of septums which create inside of the housing 1
aeration chamber 2 and two settling chambers 3 and 4.
The housing element is bounded by a pair of side
walls 5 and 6, end walls 7 and 8 and a bottom wall 9.
A support (not shown) mounts an aerating element 10,
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which may be of conventional type including a prime
mover ll and a rotating shaft 12 mo~unting an impeller ` "
13. A concentric air passage 14 has a lower end 15
adjacent to the impeller 13, so that with rotation
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5 of the impeller~ air is mixed into the treaked water
in a well known manner. First, second and third
pairs of septums 16, 17 and 18 respectively,`
interconnect an aeration chamber 2 with a pair of
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settling chambers 3 and 4. The septums 17 are sloped
outwardly and terminate above the end walls 7 and 8 -
and form lower ports l9 and 20 through which
activated sludge settled in the chambers 3 and 4 is
recycled or inducted into the aeration chamber 2 under
¦ action of the impeller 13. An effluent trough 21
communicates with an effluent pipe 22 for discharge
of treated water. Sewage inflow pipe 23 is positioned
as shown in Figure l at the lower part o~ the aera-
tion chamber, such that sewage will be immediately
subjected to the action of air bubbles 24 formed by
the impeller. Sewage enters the aeration chamber 2 ~ ~;
and moves upwards, then flows through the passageways ;
between septums 16 and 17 into the settling chambers
from which it is discharged. Activated sludge settles`
in the settling chambers because of its density, t
and collects at the bottom of the settling chambers,
from where it is drawn back into the aeration chamber
by suction produced by the circulating water. Re-
ferring to Figure l, pressure at ports l9 and 20 is
the same because the water is moving at the same
velocity in those two areas, inasmuch as they are equi-
distant from the aerator. Ak any such area where~such ~ ;i
~ a port or conduit exists, the higher the velocity,
.~ of the water, the lower pressure at the port and
hence the greater suction effect. Therefore, if the
aerator lO is not symmetrically placed but is closer
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to settling chamber 4, a greater water velocity will
be produced in the area of port 19 than at port 20;
therefore, pressure at port 19 wil~ be lower than at
20 and consequently there will be greater suction
effect at port 19 than at port 20. In this arrange-
ment of the impeller, settling chambers will work
in series (settling c~lamber 3 as first step and
~ settling chamber 4 as second step). From a considera-
¦ tion of Figures 1 and 2 it will be apparent that only
a single impeller is necessary to create the circula-
tion which draws recycling sludge from both settling
chambers which are working in parallel. Having the
septums 17 slope outwards creates a cross-sectional
area which increases toward the top of the aeration
chamber 2, thereby producing greater turbulence in
the waste water than turbulence in aeration chambers
of the prior art. The net result is increased
capacity of one aeration chamber to treat sewage, ~i
- coupled with a lower requirement for power which must
be delivered by the aerator, to make total operating
expenses lower than the same in the prior art. ,
In Figures 3 and 4 is the second embodiment of
the invention in which is shown another way of putting
two settling chambers in serial operation and recycling
sludge back into aeration chamber from both of them
and yet using only one aerator. This enables a major
portion of' the activated sludge to be removed in ~'
` the first step settling chamber and the remaining ~;
sludge to be removed in the second step settling
chamber downstream, with resultant higher efficiency
of sludge recovery.
As best seen in F'igures 3 and 4, the second step
settling chamber 25 is interconnected by conduit'
sections 26, 27 and 28 to the first step settling
chamber 29. The chamber 25 is bounded by a pair of
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converging walls 30 and 31, an end wall 32, a flat
hollow conduit 33, and a wall 34. The lower end
of the conduit 33 is positioned at the bottom of the
second step settling chamber 25, and terminates at a ! r~
medial level or location 35 of the aeration chamber 36.
Effluent from the chamber 25 flows through a trough 37
feeding an exit pipe 38.
During normal operati~n, the head in the aera-
tion chamber 36 is higher than the head in the first :;
step settling chamber 29, and the head in the second
step settling chamber 25 is below that of the `~
chamber 29. Thus, as water is introduced into the
aeration chamber 36 through a pipe 39 and aeration ;~
takes place, water first travels through the passageway
between septums 40, 41 and 42 to the first step
settling chamber 29 which operates in a manner similar~
to that in the first embodiment. Then water flows
through troughs 26, 27 and 28 to the second step ; j
settling chamber 25 where further settling occurs. ` ¦
Effluent from the chamber 25 flows at the top
through a trough 37 feeding an exit pipe 38. The ~ j
amount of sludge in the effluent from the chamber 25
-is considerably less than that in the chamber 29.
Because of the difference in liquid levels between the
chamber 36 and the chamber 25, sludge can be moved
back into the aeration chamber from the chamber 25 ¦
by creating at the point 35 a pressure lower than at
the point 43. It is accomplished by the fact that ;
two different phenomena are used: in the vicinity
of point 43 pressure differential is produced by the
circulation of water; while at the point 35 pressure -
differential is produced by the motion of the air
bubbles rising to the surface. Because the ~elocity
of rising air bubbles is higher than the velocity of ~,
the clrculating water, it creates lower pressure at ,
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the point 35 of conduit 33 than at port 43, as was
'explained'in the first embodiment~descrip,tion. That
is why a single aerating device 44 for recirculating
sludge from both settling chambers is used in this
5~ embodiment. The aerating device 44 can be either a
mechanical aerator as shown in Figures 1, 2, 3, 4 and
5 or an air diffuser as in Figure 6.
The third embodiment, illustrated in Figure 5
will be seen to be a combination of the features
of the first and second embodiments, in that a pair
of first step settling chambers 51 and 52 are dis-
posed on either side of the aerating chamber 53, this
portion of the third embodiment functioning in
exactly the same manner as the first embodiment. In ¦
addition a second step settling chamber is provided
which receives the effluent through troughs 45, 46
and 47 from the two first step parallel connected
settling chambers. Effluent from the second step
settling chamber 49 leaves the treatment unit at the
top through a trough 50. Sludge from the second step
settling chamber 49 is returned back into aeration . ,
chamber 53 at the end 55 of conduit 54 in exactly
the same manner as the second embodiment. A single
impeller aerating device 48 is used to recover sludge
from each settling chamber in this embodiment. All
three settling chambers 51, 52 and 49 of this emb'odi-
ment can work in series if needed by proper arrange-
ment of the aerating device 48 as is explained in
the first embodiment.
In the fourth embodiment (Figure 6) is shown
(for convenience only) an aeration chamber 56 and
part of the first step settling chamber 57 and'the
second step settling chamber 58. This embodiment
differs from the second embodiment in the use of an
air diffuser aerator 59 instead of a mechanical
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aerator~ The large amount of air tends to rise to
the surface of the aeration cham~er at a very rapid
rate, creating substantial turbulence to achieve
the same hydrodynamic effect as an impeller.
Return of sludge from the settling chambers 57 and 58
back into the aeration chamber 56 is achieved by
positioning the air diffuser 59 underneath an upper
end 60 of the conduit 61. In this embodiment as
well as in the previous ones, no pumps are needed to
circulate sludge from the settling chambers back
into the aeration chamber.
I wish it to be understood that I do not
consider the invention limited to the precise details
of structure shown and set forth in this specifica-
tion, for obvious modifications will occur to those
skilled in the art to which the invention pertains.
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