Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~RIEF DESCRIPTION OF THE INVENTION BACKGROUND
AN~ SUMMARY OF THE INVEN~ION
The invention relates to an improved method and
submerged system for efficiently mixing gas with waste water
and for flushing accumulated debris from such submerged system.
Industrial waste, sewage and the like are commonly
purified by pumping the li~uid into a large tank, pond or b~sin
where a bacteria population consumes the inorganic and organic
material. Because the dissolved oxygen in the waste water is
usually insufficient to support the required population of
bacteria, the water must be aerated. This can be done with a
surface aerating machine which has beaters extending into the
waste water from above the water surface to agitate the water
and incorporate air. Alternatively, air can be diffused through
the bottom of the basin, e.g., through a porous medium.
Surface aerators are not efficient and cause certain mechanical
problems. The energy loss of diffusing air is also great and
a diffused system is not suitable for installation in an
existing pond.
Waste water can also be aerated by pumping through
submerged tubes with openings through which air is drawn or pumped
into the tubes to create turbulent mixing. Such devices include
vortex, jet, Venturi and impingement type devices and are
much more energy ef~icient than diffusion or surface aerator
systems.
One problem which can arise with systems o~ this
sort in which water and gas are mixed in a chamber is that
small particles in an aeration basin, tank or pond can be caught
within the mixing chambers, the pump or the conduits therebetween,
to eventually clog the same. In sewage treatment, material
such as hair, paper, cloth, etc. will become lodged in the
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chambers, eventually blocking water flow and reducing the effect-
iveness of the system. Since submerged systems of this type
normally pump a great volume of water, even a small number of
particles in the body of waste water will eventually become
lodged within the mixing chambers. It is not normally desirable
to shut down the system for maintenance, and removal of this
material, even when the basin is drained, can be a difficult task.
However, these systems can be flushed of such
debris by directly or indirectly connecting the inlets of
each of the mixing chambers to which waste water is normally
supplied for aeration to a higher, backflush location
closer to or above water surface. If the pump is turned off
while air continues to flow into the chambers, the difference
in pressure between the water at the mixing chambers and the
higher location causes flow of the air backward through the
inlets to that back-flush location to flush the system.
Surprisingly, the air pumps waste water at a substantial flow
rate and pressure backward through the system. A separate
line can be used with a valve to flush the debris directly
above the surface where it can be collected. The waste water
can be back-flushed through the pump to clean the pump screen
provided that the pump and its strainer are mounted above the
mixing chambers.
The air can be intermittently turned on and off to
create pulsations of water which act as a hammer to dislodge
debris.
Other objects and purposes of the invention will be
clear from the following detailed description of the drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS:
FIGURE 1 shows a schematic side view of the system
of the present invention in use;
FIGURE 2 shows a planar view of the system of
FIGURE l;
FIGURE 3 shows a sectional view of a mixing chamber
of the present invention;
FIGURE 4 shows a sectional view of a helical air
mixing chamber;
FIGURE 5 shows a partial sectional view of the
mixing chamber of FIGURE 4;
FIGURE 6 shows a schematic view of another
embodiment;
FIGURES 7 and 8 show a further embodimènt.
DETAILED DESCRIPTION OF ~HE DRAWINGS:
.
Reference is now made to FIGURES 1 and 2 which
schematically illustrate one embodiment of the present in-
vention. In the embodiment of FIGURES 1 and 2, a plurality
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of circumferentially disposed mixing chambers 20, each preferably
identical to the other, are circularly disposed around a dome ;
manlfold 22 which include~ an upper section 24 into which
water is pumped and a lower section 26 connected to a source
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of air or oxygen at a suitable pressure. Each of the mixing
chambers is of the type shown in detail in FIGURES 3-5 and
discussed in detail below.
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A plurality of conduits 30, ea~h formed of a metal
segment 32 and a plastic segment 34 connect section 24 to
each mixing chamber 20 so that water is continuously
pumped through each chamber 20. A similar series of conduits
40 formed of metal portion 42 and a plastic portion 44 also
connect section 26 to each of the mixing chambers 20. As
will be apparent below, each of the mixing chambers forms
parallel streams of air and gas which interact within an
extending chamber of the mixing chamber to form tiny bubbles
which efficiently mix with the pumped waste water. Manifold
22 is suspended from a fibreglass floating work platform 50
by means ~f guide bars 52 and 54 and two bars behind them in
Figure 1. Industrial air piping conduit 60 is attached to guide
bar S4 for supplying air to section 26. C~ble 62 connects the
manifold 22 to a frame 64 on platform 50 for lifting manifold 22
and holding manifold 22 in position for maintenance.
A conventional submersible pump 66 is mounted above
manifold 22 and includes an optional strainer basket 67
which keeps most debris from entering the pump and being
lodged therein. For many installations the basket can be
omitted and the debris which collects in the pump,
backflushed as described below. Conduit 68 connects pump
66 to section 24.
Floating work platform 50 is provided with suitable
railings 70 of a height so that the unit can be lifted to a
level for convenient work on the mixing chambers and pump.
An on-shore air pump 74 is schematically shown as connected
to line 60 for pumping air, oxygen or other gas to section
26 for mixing with the pumped waste water.
When it is desired to clean the inevitable particles
and debris which will accumulate within the pump 66 and the
mixing chamber 20, pump 66 can simply be turned off while the
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air pump 74 continues forcing air into the mixing chambers.
However, surprisingly, instead of moving out of the outlet,
the air will pump waste water back through the inlet, opposite
to the direction of flow during aeration, through conduits 34
and 32 into section 22, through conduit 68 and through pump
66, blowing off the debris which has accumulated on the outside
of strainer basket 67. This occurs because the water pressure
at the level of the strainer basket is lower than the water
pressure at the level of the mixing chambers 20. The outlet -
point for the back-flushing should be as close to the waterline
as possible. Alternatively, flushing can be accomplished by
operating a valve 76 in a line 78 which connects to conduit 68.
With many pumps, particularly those mounted out of the water, ~ -
flushing through a separate line is preferable to flushing -
through the pump. The debris will now be blown into the air
and since the pressure differential is greater, the force ~ -
produced, by the air which works as an air hammer, will blow
the debris through the system and back-flush all of the
material in a few minutes. Turning the air on and off ~`
repeatedly creates pulsations which will dislodge almost all
debris and back-flush it from the system.
FIGURES 3-5 illustrate the unique mixing chamber 20
of the present invention. Waste water flows from the inlet
through passage 100 into the extending chamber 102. At the
intersection between passage lOO and section 102, a step region
104 is provided at which a plurality of bores terminates. To
keep the vortices within chamber 102 at high air pressure, the
bores inject the gas at an angle between roughly 11 and 22
1/2. A chamber with helical vanes in the bores as shown in
FIGURES 4 and 5 creates greater wave generating conditions.
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Thus, two parallel stream~ of gas and waste water
are created as shown in FIGUPE 3. As streams move along the
chamber 102, the friction between them causes waves to form
and the air thus trapped in waves to disperse into tiny
bubbles. Since the air and gas streams move in the same
direction, effective mixing is achieved at minimum energy
consumption. It is desirahle that under most co~ditions
the mixing take place within chamber 102 and for that reason
the chamber is slightly tapered inwardly within the portion 110 with
the cross-section decreasing in the direction from inlet
to outlet and more radically tapered within portion 112.
These tapers extend the maximum air flow rate with which
the system will operate by several times without sub-
stantial loss of efficiency.
The helical guide vanes 106 ~rovide a twi ting
motion to the air and thus create more waves which also help
the interface break up more quickly by creating instability.
The mixing chambers can be made of any suitable
materials such as stainless steel, aluminum or plastic.
;~ FIGURE 6 shows another embodiment in which the
submersible pump is replaced with a conventional waste
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;water pump 200 mounted beside tank 202 and oonnected to
manifold 204 by line 206- Pump 200 has an inlet 207. A ~lurality
of mixing chambers 208 are mounted about manifold 204 and
can be any suitable mixing device such as a jet, vortex,
Venturi or impingement type device. Air pum~ 210 is also
mounted beside tank 202 and is connected to manifold 204
by line 212. Valve 214~can be opened to back-flush waste
water as described above while pump 200 is turned off and
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pump 210 continues to force gas into the mixing chambers of
device 208. The gas then pumps the waste water back
through manifold 204 and line 212 where it leaves via valve
214. The waste water returns to the tank and the debris
is caught in strainer 216 if desired.
FIGU~ES 7 and 8 illustrate yet another embodiment
of the invention which utilizes mixing chambers as
described above. In the arrangement of FI~URES 7 and 8, water
in a suitable tank 300 is pumped through a straight line pipe
302 by a pump 304. A plu_ality of mixing chambers 306
extend outwardly from pipe 302 at separated locations as
shown in FI~URE 7. Air is supplied to a second pipe 308
which extends above and parallel to pipe 302. Alternatively, -~
one pipe can be within the other. Pipe 308 is connected to
the individual mixing chambers for injecting air into those
chambers. ~ipes 302 and 308 preferably extend along the
center of the basin 300 parallel to the edges so as to cause
a favorable pattern of water flow from one side to the other
using a minimum amount of energy to create maximum flow and
aeration. The system is flushed by opening valve 310 while
pump 304 is turned off and air continued to be supplied to
chambers 306.
Many changes and modifications in the above described
embodiments of the invention can, of course, be carried out with-
out departing from the scope of the invention. The system can
be used with non-aqueous liquids and gas other than air such as
pure oxygen can be added. Accordingly, that scope is intended
to be limited only by the scope of the appended claims.
