Note: Descriptions are shown in the official language in which they were submitted.
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S P E C I F I C ~ T I O N
TITLE OF T~E INVENTION
Solid-Liquid Separator
FIELD OF THE INVENTION
The present invention relates to a solid-liquid separator
to be used in place of a sedimentation basin in an activated
sludge process or a flocculant separation process.
BACKGROUND OF THE INVENTION
The solid-liquid separator of the prior art is exemplified
by a submerged filter system for purification, as shown in
Fig. 1. As shown, a raw liquid supply pipe 2 is opened over
one side of an aeration tank 1, in which is dipped a filter
unit 3. This filter unit 3 is constructed by arranging a
plurality of planar filtration membrane modules 5 vertically
in a casing 4. These filtration membrane modules 5 are
juxtaposed at a constant spacing to form a passage P between
the adjacent ones of them. The filtration membrane modules 5
can be formed of a tubular filter medium of ceramics.
To the individual filtration membrane modules 5, there are
connected suction tubes 6 which are made to communicate with a
permeated liquid suction pipe 7. This permeated liquid suction
pipe 7 has its other end connected to a suction pump 8, and a
liquid feed pipe 9 is connected to the discharge side of the
suction pump 8 and opened above a permeated liquid tank 10.
In the casing 4 of the filter unit 3, there is arranged
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below the filtration membrane modules 5 a diffuser 11 which is
connected via a gas supply pipe 12 to a blower 13. In the
bottom portion of the aeration tank 1, there is opened a
sludge suction pipe 14 which is connected to a sludge pump 15.
As shown in Fig. 2, each filtration membrane module 5 is
composed of a membrane supporting plate 16, a membrane
supporting net 17 and a filtration membrane 18. The membrane
supporting plate 16 is made of a resin and formed with a
permeated liquid passage 19. This permeated liquid passage 19
has its one end opened in the surface of the membrane
supporting plate 16 and its other end communicating with the
corresponding one of the suction tubes 6.
For the process, a raw liquid 20 is supplied from its
supply pipe 2, and an aeration gas 21 such as air containing
oxygen is supplied to the diffuser 11 from the blower 13 via
the gas supply pipe 12 so that it is injected from the
diffuser 11 into the aeration tank 1 to purify the raw liquid
20 biologically.
On the other hand, a purified liquid 22 is subjected to
the solid-liquid separation through the filtration membrane
modules 5 by applying a vacuum to the permeated liquid
passages lg of the filtration membrane modules 5 via the
permeated liquid suction pipe 7 and the suction tubes 6 by the
suction pump 8. Then, a solid content such as sludge is
trapped by the filtration membranes 18 whereas a permeated
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liquid 23 having passed through the filtration membranes 18 is
sucked via the permeated liquid passages 19 and guided to the
permeated liquid tank 10 by way of the suction tubes 6, the
permeated liquid suction pipe 7, the suction pump 8 and the
liquid feed pipe 9.
In this meanwhile, upward liquid flows are established in
the passages P between the individual filtration membrane
modules 5 by the air lifting action of the aeration gas 21 so
that they act as scavenging flows along the membrane faces to
suppress any blocking of the caking layer on the membrane
faces.
Incidentally, in case the solid-liquid separator thus far
described is to be applied to the treatment of sewage or
sludge, it is desired to reduce the power consumption. In
order to maintain the membrane scavenging flows, however, a
certain rate of aeration is indispensable so that the
reduction of the power consumption for the air blower is
restricted to some extent. On the other hand, the demand for
the aeration per unit filtration area could be reduced by
enlarging the vertical length of the membrane modules. From
the standpoint of maintenance, however, the desired vertical
length is about 1 m at most.
SUMMARY OF THE INVENTION
The present inventio~ has been conceived to solve the
above-specified problem and has an object to provide a solid-
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liquid separator which can reduce the power consumption whenapplied to the activated sludge process for sewage, for
example.
In order to achieve the above-specified objec-t, according
to the present invention, there is provided a solid-liquid
separator comprising: a treating tank; means disposed in said
treating tank for establishing a horizontal flow in the same;
and a plurality of stages of submerged filter systems arranged
in said treating tank sequentially in the direction of said
horizontal flow, each of said submerged filter systems having
a plurality of filtration membrane modules juxtaposed at a
suitable spacing for forming the gaps between the adjacent
ones of said filtration membrane modules into passages along
said horizontal flow.
In the above-specified construction of the present
invention, the horizontal flow to be established in the tank
circulates sequentially through the submerged filter systems
of the stages. In each of these systems, the horizontal flow
flows through the passages between the adjacent filtration
membrane modules as a scavenging flow for the membrane faces
of the modules. This scavenging flow prevents the sludge or
the like from depositing on the membrane faces of the
individual filtration membrane modules. At this time, the
horizontal flow having passed through the upstream submerged
filter system goes into the downstream one so that it can be
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used sequentially by the submerged filter systems of the
stages disposed in the treating tank thereby to reduce its
power consumption.
In a more preferable construction of the present
invention, diffusers are disposed below the submerged filter
systems.
According to this construction, by feeding the gas from
the diffusers disposed below the submerged filter systems,
there are established upward flows which go along the membrane
faces of the filtration membrane modules so that it can
promote the rising effect of the scavenging flow. If the
means for establishing the horizontal flow has no function to
introduce oxygen, the gas feed from the diffusers is effective
as the oxygen feeding means.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram showing the entire
construction of the solid-liquid separator of the prior art;
Fig. 2 is a section showing the membrane module which is
used in the solid-liquid separator of the prior art;
Fig. 3 is a schematic diagram showing the entire
construction of a solid-liquid separator according to one
embodiment of the present invention;
Fig. 4 is a schematic diagram showing a submerged filter
system for purification to be used in the same solid-liquid
separator;
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Fig. 5 is a perspective view showing a filtration membrane
module to be used in the same submerged filter system;
Fig. 6 is a schematic diagram showing the entire
construction of a solid-liquid separator according to another
embodiment of the present invention; and
Fig. 7 is a section showing means to be used in the same
solid-liquid separator for generating horizontal flows in the
tank.
EMBODIMENTS
The present invention will be described in the following
in connection with its one embodiment with reference to the
accompanying drawings. In Figs. 3 to 5, a solid-liquid
separator 31 is equipped with a generally elliptical treating
tank 32, which has its inside divided by a partition 33, which
is longitudinally extended at the center of the tank, into two
ha]ves to form ditches at the two sides of the partition 33.
A raw liquid supply pipe 34 is opened in one side of the
treating tank 32, and a plurality of stages of submerged
filter systems 35 for purification are arranged at the two
sides of the partition 33 sequentially along the ditches of
the tank.
At the two end portions of the partition 33, there are
individually arranged pumps 36a and 36b which constitute means
for establishing horizontal flows in the treating tank 32.
The horizontal flows (as indicated by arrows A) thus
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established by the pumps 36a and 36b sequentially circulate in
the individual submerged filter systems 35 at the two sides of
the partition 33.
As shown in Figs. 4 and 5, each submerged filter system 35
has a plurality of filtration membrane modules 37 juxtaposed
vertically at a suitable spacing such that they are arranged
in parallel with the ditches of the treating tank 32, i.e.,
the horizontal flows A. As a result, the ditches thus formed
between the adjacent filtration membrane modules 37 and 37
extend along the horizontal flows A.
Each filtration membrane module 37 is equipped with a
nozzle 39 via the (not-shown) permeated liquid passage which
is formed in the filtration membrane 38, and these nozzles 39
are connected to a suction header 40b via respective suction
tubes 40a. The suction header 40b is connected via a
permeated liguid suction pipe 42 to a suction pump 41 which is
disposed outside of the treating tank 32. The permeated
liquid having passed through the filtration membranes 38 is
extracted by applying a vacuum to the permeated liquid
passages by the suction of the suction pump 41.
As shown in Fig. 4, there are arranged below the submerged
filter systems 35 diffusers 43 which are connected to blowers
44 disposed outside of the treating tank 32, so that the
diffusers 43 can be fed with air or oxygen. Moreover, the
submerged filter system 35 is equipped at its upper and lower
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end portions with guide plates 45 for guiding the horizontal
flows A in the passages between the individual filtration
membrane modules 37.
In the embodiment thus far described, when the raw liquid
is supplied to the treating tank 31 from its supply pipe 34,
it is mixed with the liquid to be treated in the tank. After
this, the raw liquid is caused to flow at one side of the
partition 33 as the horizontal flow A established by the pump
36a and to circulate downward sequentially through the
submerged filter systems 35 which are arranged in the stages
in the treating tank 31.
In this state, the suction pump 41 is energized to apply
the vacuum to the permeated liquid passages of the filtration
membrane modules 37 to separate the solid and liquid of the
liquid to be treated, which flows in the ditches of the
treating tank 32. The permeated liquid having passed through
the filtration membranes 38 is extracted via the nozzles 39,
the suction tubes 40a, the suction headers 40b and the
permeated liquid suction pipe 42.
The liquid to be treated, as flowing as the horizontal
flows A, circulates sequentially through the submerged filter
systems 35 of the stages and is fed at the vicinity of the one
end portion of the partition 33 to the other by the pump 36b.
The aforementioned solid-liquid separating processes are
repeated to separate the raw liquid into the solid and liquid
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while the horizontal flows A are circulating in the ditches of
the treating tank 32.
At this time, the horizontal flows A in each submerged
filter system 35 are guided at the upper and lower end
portions of the filter system 35 by the guide plates 44 to
mainly go into the passages between the filtration membrane
modules 37 so that they become the scavenging flows in
parallel with the faces of the filtration membranes 38 of the
modules 37. These scavenging flows prevent the sludge or the
like from depositing on the membrane faces of the individual
filtration membrane modules 37.
Moreover, the horizontal flow A having passed through the
submerged filter system 35 at the upstream side goes into the
submerged filter system 35 at the downstream side so that
these submerged filter systems 5 arranged in the stages in the
treating tank 32 can use the same horizontal flow A
sequentially to reduce the power to be consumed for rinsing
the membrane faces.
In addition, the air or oxygen to be fed by the blower 44
is diffused from the diffusers 43 to establish upward flows,
as indicated at arrows B. These upward flows B go along the
faces of the filtration membranes 38 of the modules 37 so that
the rinsing effect can be promoted. At the same time, it is
possible to expect the peeling effect of the deposit of the
membrane faces by the bubbles. When the oxygen has to be
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introduced for purifying the liquid to be treated, the supply
of air or oxygen from the diffusers 43 is effective as the
oxygen supply means.
Incidentally, the present embodiment has been described
with the filtration membrane modules 37 being planar.
However, these modules 37 can be made of a tubular filter
medium of ceramics.
Here will be described a solid-liquid separator according
to another embodiment of the present invention with reference
to Figs. 6 and 7. The solid-liquid separator of this
embodiment, as designated at numeral 51, has substantially the
same construction of the solid-liquid separator which has been
described with reference to Figs. 3 to 5. The description of
the components having the same constructions and operations
will be omitted by designating the components at the common
numerals.
The solid-liquid separator 51 of this embodiment is
different from that of the foregoing embodiment in that the
partition 33 has its two ends spaced from the inner wall of
the treating tank 32 and in that the pumps acting as the means
for establishing the horizontal flows A are replaced by rotors
52a and 52b disposed in the treating bath 32.
The rotors 52a and 52b are arranged in line with the
submerged filter systems 35 in the ditches at the two sides of
the partition 33 and are so diagonally disposed that they may
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be at the longest distance. Moreover, the horizontal flows A
are established by the rotations of the rotors 52a and 52b and
fed to the submerged filter systems 35 downstream of the
individual rotors 52a and 52b at the two sides of the
partition 33. As shown in Fig. 5, still moreover, there is
disposed below the rotor 52a or 52b a guide plate 53 for
feeding the horizontal flow A established thereby mainly to
the passages between the individual filtration membrane
modules 37.
By this construction, too, the solid-liquid separation of
the raw liquid is repeated as in the foregoing embodiment by
the submerged filter systems 35 while the liquid to be treated
is circulated in the treating tank 32. Since, moreover, the
horizontal flows A established by the rotors 52a and 52b are
fed as the scavenging flows to the submerged filter systems
35, the deposition of the sludge or the like on the surfaces
of the filtration membranes 38 can be prevented to prevent the
membrane faces from getting clogged. Still moreover, the
liquid to be treated can be aerated with the oxygen while it
is splashed into the air by the rotations of the rotors 52a
and 52b, it can be fed with the oxygen necessary for the
purification without providing any diffuser.
