JP2008055361A - Oil separator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil separator which is improved in oil separation efficiency by removing sludge contained in waste water as much as possible in a stage prior to the oil separation process. <P>SOLUTION: The oil separator is provided with a liquid tank for separating oil from waste, wherein the liquid tank 5 is provided with four first to fourth separation tanks 6-9 which are demarcated by first-third partition walls 12, 15, 21, and arranged in parallel. A slanted passage is formed to communicate with a front lower part of the second separation tank 7 through the lower part of the tank 7, toward the inclined lower front side from the first tank 6. The second partition wall 15 is extended toward inclined rear upper side with a front side plate 4d as a base part. The second separation tank 7 is made to communicate with the third separation tank through a first communication hole 17 formed at the upper part of the second partition wall 15. The third separation tank 8 is made to communicate with the fourth separation tank 9 through a second communication hole 23 formed near the bottom part of the third partition wall 21. Sludge settles when passing through the slanted passage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an oil / water separator for separating waste water into oil and water.

  Oil-water mixed wastewater (hereinafter simply referred to as wastewater) discharged by washing and processing is basically treated as sewage. However, wastewater containing a large amount of oil cannot be allowed to flow as sewage. This is because the oil content of the wastewater clogs or accumulates in the sewage pipe and becomes a causative substance of a fire, or causes water pollution when discharged into a river as it is. Therefore, at present, regulations are gradually being made so that wastewater cannot be discharged as sewage unless the oil content in the wastewater is equal to or less than a predetermined value (generally expressed as a normal hexane extract substance content).

Such wastewater is widely derived from industrial wastewater, washing wastewater from restaurants and other restaurants, gasoline station washing wastewater, general household wastewater, and the like, and is discharged in large quantities. However, there has been no apparatus that can treat such waste water in large quantities. For example, although a filter-exchangeable oil / water separator exists, the filter is clogged in a short time, and is not suitable for treating a large amount of wastewater. In addition, the oil can be reused if only the oil can be recovered, but it is difficult to reuse once the oil is adsorbed on the filter.
From this point of view, the applicant has developed an oil-water separation apparatus shown in Patent Document 1 for the purpose of removing oil from wastewater containing a large amount of oil. However, in some cases, the wastewater contains a considerably large amount of sludge in addition to oil. The sludge is suspended matter derived from light metal chips such as aluminum alloy, sludge or fibers. Here, organic solvent heavier than water is also included in the concept of sludge. The oil / water separator of Patent Document 1 cannot sufficiently remove this sludge. If a large amount of sludge is contained in the wastewater, the oil is captured by the sludge, and the oil to be raised is suspended in the water together with the sludge.
The present invention has been made paying attention to such problems existing in the prior art. An object of the present invention is to provide an oil / water separator that improves the efficiency of oil / water separation by removing sludge contained in wastewater as much as possible in the previous stage of the oil / water separation step.

In order to achieve the above object, in the invention according to claim 1, in the oil-water separator having a liquid tank for separating the oil from the waste water mixed with the oil, the liquid tank includes the first to third liquid tanks. The first separation tank includes four first to fourth separation tanks arranged in series, which are partitioned by a partition wall, and the first separation tank is provided with an inlet for introducing waste water, and the introduced waste water is forwarded. An oblique passage that leads obliquely downward passes from the first separation tank to a lower position of the second separation tank and communicates with a lower front position of the second separation tank, and the second partition wall is The second separation tank is separated from the third separation tank by a first communication hole extending obliquely rearward and upward with the bottom or side surface of the liquid tank as a base, and formed in the upper part of the second partition wall. The third separation tank is formed close to the bottom of the third partition wall. The second communication hole is communicated with the fourth separation tank, and the third separation tank is provided with an oil discharge port, and the fourth separation tank is provided with a purified water discharge port. This is the gist.
Further, in the invention of claim 2, in the oil / water separator having the liquid tank for separating the oil from the waste water mixed with the oil, the liquid tank is arranged in series divided by the first to third partitions. The first to fourth separation tanks are provided, and the first separation tank is provided with an inlet for introducing waste water, and the oblique shape guides the introduced waste water obliquely forward and downward. A passage passes from the first separation tank through a lower position of the second separation tank and communicates with a front lower position of the second separation tank, and the second partition wall has a bottom surface or a side surface of the liquid tank. The second separation tank is communicated with the third separation tank by a first communication hole that extends obliquely rearward and upward as a base, and is formed in an upper portion of the second partition wall. The separation tank is formed by a second communication hole formed near the bottom of the third partition wall. The first separation tank is communicated with the first to third separation tanks, and a plurality of sets are continuously arranged, and the third separation tank is the same at the end of the liquid tank. 3 is connected to the fourth separation tank by a fourth communication hole formed near the bottom of the partition wall, the oil separation outlet is provided in the third separation tank, and purified water is supplied to the fourth separation tank. The gist is that a discharge port is provided.

Further, in the invention of claim 3, in addition to the configuration of the invention of claim 1 or 2, a bubble blocking member is suspended from the upper position between the second partition wall and the third partition wall. This is the gist.
Moreover, in addition to the structure of the invention in any one of Claims 1-3, in the invention of Claim 4, in the said 3rd separation tank, the bottom part side and the upper part side are provided in the downstream position of the said foam blockage member. The gist of the invention is that one or a plurality of water flow suppressing members that are not sealed are arranged.
Further, in the invention of claim 5, in addition to the structure of the invention of claim 3, an oil discharge port is provided at the upper position of the third separation tank, and the upper end of the second partition wall, the foam blocking member The gist is that the lower end of the oil and the lower end of the oil outlet are arranged in a substantially horizontal state.
Moreover, in addition to the structure of the invention in any one of Claims 1-5, in the invention of Claim 6, the upper surface of the said 2nd partition makes the sludge which settles in the said 3rd separation tank flow down ahead. The gist is that it also serves as the sludge flow bottom.
Moreover, in addition to the structure of the invention in any one of Claims 1-6, in the invention of Claim 7, in the said 2nd separation tank, the auxiliary | assistant inclination board for promoting the growth of an oil dama is arrange | positioned. The gist of this is

In such a configuration, the wastewater is introduced into the first separation tank from the introduction port, and further, the wastewater flows down obliquely forward and downward in the oblique passage. When passing through the oblique passage, the water layer and the oil layer are roughly separated, and much of the sludge in the wastewater is allowed to sink. In addition, even if waste water is directly supplied into the first separation tank from the introduction port, it may pass through another tank such as a precipitation tank in the middle.
The waste water that has reached the second separation tank quickly reaches the upper layer of the second separation tank because the oil layer has a large buoyancy. A considerable amount of oil is removed at this stage, but a large amount of oil still remains in the aqueous layer. In particular, fine particles with a diameter of about several tens of μm, called so-called oil lumps, are extremely light, so if they diffuse in the water layer, they will move freely in the water due to the pressure of the oscillating water. It's not easy to do. The total amount of oil based on oil lumps is a significant proportion of the wastewater, and there may be cases where oil lumps in the aquifer cannot be discharged as sewage unless the oil lumps in the water layer are sufficiently eliminated.
In the second separation tank, the water layer flowing in from the first separation tank is pushed by the inflowing waste water one after another, and rises obliquely rearward along the inclined surface of the second partition wall. At that time, oil lumps in the water layer come into contact with each other to form larger oil lumps, which gradually grow and increase buoyancy. Further, as described above, the oil dam is free to move in the water layer, but the collision force when the oil dam collides with the inclined surface generates a vector in the direction along the inclined surface. In particular, the oil dam that collides with the inclined surface rises or descends in a plane along the inclined surface. Therefore, the density of oil lumps on the inclined surface increases, and oil lumps that come into contact with each other when moving along the inclined surface form new and larger oil dams one after another, gradually increasing buoyancy. It becomes. Grown oil llamas will gradually rise. The water layer that has reached the second separation tank further flows out from the first communication hole at the top of the second partition wall to the third separation tank.

An aqueous layer containing oil (mainly oil lumps) that has not been removed in the second separation tank will flow into the third separation tank. In the third separation tank, oil further accumulates upward.
Finally, the water layer reaches the fourth separation tank from the second communication hole formed near the bottom of the third partition wall. Since the water layer reaching the fourth separation tank has very little oil, it can be drained as it is as sewage. Further, it may be reused without draining. At that time, for example, it is possible to pass through a filtration membrane or the like and use it as clean water.
It is more preferable for the reliable removal of the oil layer that such first to fourth separation tanks are arranged in a plurality of sets with the first to third separation tanks as one set. In this case, the third separation tank is connected to the fourth separation tank at the end of the liquid tank.

Here, it is preferable that the bubble blocking member is suspended from the upper position between the second partition wall and the third partition wall. This is because it is possible to prevent bubbles generated in the upper part of the waste water from moving in the direction of the third separation tank.
Further, it is preferable that one or a plurality of water flow suppression members that do not seal the bottom side and the top side are disposed in the third separation tank and downstream of the foam blocking member. This suppresses the undulation of the upper part of the liquid layer.
It is preferable that an oil discharge port is provided at an upper position of the third separation tank, and that the upper end of the second partition, the lower end of the foam blocking member, and the lower end of the oil discharge port are arranged in a substantially horizontal state. As a result, the upper surface of the liquid layer is always near the upper end of the second partition wall, and wastewater falls from the second separation tank into the third separation tank, resulting in turbulent flow, or conversely, oil is excessively accumulated in the tank. Stable processing is possible without any problems.
It is preferable that the upper surface of the second partition wall forms a bottom surface in the third separation tank, and in this case, the upper surface of the second partition wall is a sludge stream that allows sludge that settles in the third separation tank to flow forward. It will be the lower surface. As a result, the settled sludge can be quickly moved in the forward direction. It is preferable that a discharge port for discharging sludge accumulated in front of the second and third separation tanks is provided near the base of the second partition wall.

  In the inventions of the above-mentioned claims, it is possible to prevent as much as possible that fine particles derived from oil called so-called oil lumps, which remain in the water layer and are difficult to remove, are combined with the sludge by allowing the sludge to settle. For this reason, the growth of oil dams is promoted and the oil components are likely to rise, so that the oil components can be removed efficiently and promptly, and as a result, the purification efficiency of the waste water is improved. In addition, oil lumps grow along the inclined surface of the second partition wall, but this second partition wall extends to the rear and overlaps with the slant passage so that the path through which the wastewater flows is long. The liquid tank can be made compact.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment in which an oil-water separator according to the present invention is embodied concretely will be described with reference to the drawings. In the following description, the rear or upstream side refers to the left direction in FIGS. 2 to 4, and the front or downstream side refers to the right direction in the drawings. Left and right refer to the left and right direction when facing forward.
(Embodiment 1)
As shown in FIGS. 1 and 2, the oil / water separator 1 includes a rectangular parallelepiped liquid tank 5 including three openable canopies 2 a to 2 c, a bottom plate 3, and four side plates 4 a to 4 d surrounding the side surface. It has. The inside of the liquid tank 5 is divided into four first to fourth separation tanks 6 to 9.
The first to fourth separation tanks 6 to 9 are arranged in series from upstream to downstream. The first separation tank 6 is arranged in the uppermost stream of the liquid tank 5. The first separation tank 6 is partitioned by three side plates 4 a to 4 c and a first partition wall 12. The first partition 12 extends between the left and right side plates 4b and 4c. That is, the tank structure has a flat shape that is wide on the left and right and narrow on the front and rear. The upper part of the first separation tank 6 is expanded to form a shelf 10 and an opening 11 as an inlet for introducing waste water.
On the lower end side of the first separation tank 6, an oblique passage 13 extends obliquely forward and downward. The oblique passage 13 has a lower end of the first partition 12 as a base and an upper swash plate 14a and a rear side plate 4a extending to a position slightly ahead of the front side plate 4d, and a front end connected to the bottom plate 3. The lower swash plate 14b is used. Both swash plates 14a and 14b extend in parallel in a diagonally downward front direction and extend between the left and right side plates 4b and 4c. The oblique passage 13 communicates with the lower front position of the adjacent second separation tank 7.

The second separation tank 7 is divided by left and right side plates 4b and 4c, first and second partition walls 12 and 15, an upper swash plate 14a, and a front side plate 4d and a bottom plate 3. That is, the second separation tank 7 is arranged in an overlapping manner at the upper position of the oblique passage 13. The second partition wall 15 is disposed downstream of the first partition wall 12, extends between the left and right side plates 4b and 4c, and is straight from the front side plate 4d toward the rear obliquely upward at an angle of 35 degrees. It has been extended.
The upper position of the second partition wall 15 is a predetermined lower position (position about 4/5 of the height between the canopies 2a to 2c and the bottom plate 3) spaced from the canopy 2, and the upper end of the second partition wall 15 and the canopy 2a. A first communication hole 17 communicating with the adjacent third separation tank 8 is formed between the first and second separation tanks 8.
The third separation tank 8 is partitioned by left and right side plates 4b and 4c and second and third partition walls 15 and 21. As shown in FIG. 2, the third separation tank 8 is disposed so as to overlap with the second separation tank 7 and the oblique passage 13 in the vertical direction.
The third partition wall 21 is disposed downstream of the second partition wall 15, extends between the left and right side plates 4b and 4c, and extends vertically downward from the base position of the canopy 2a. A lower end side of the third partition wall 21 is opened, and a second communication hole 23 communicating with the adjacent fourth separation tank 9 is formed.

A bubble shielding plate 24 as a bubble blocking member is suspended from the position of the canopy 2a downward in the third separation tank 8. The bubble shielding plate 24 extends between the left and right side plates 4b and 4c. The lower end position of the bubble shielding plate 24 exists on the same horizontal line H as the upper end position of the second partition wall 15.
Within the third separation tank 8, two barriers 25 as water force control members are disposed at the upper position. The barrier 25 is a plate body that is rearwardly inclined toward the upper side, and extends between the left and right side plates 4b and 4c. The upper end position of the barrier 25 exists on the same horizontal line H as the upper end position of the second partition wall 15. A laterally long oil drain hole 26 is formed on the right side plate 4 c in the third separation tank 8 near the third partition wall 21. The lower end position of the oil drain hole 26 exists at a position slightly lower than the horizontal line H.

The fourth separation tank 9 is partitioned by three side plates 4 b to 4 d and a third partition wall 21. In the fourth separation tank 9, a water intake tank 28 is formed on the front side plate 4 d so as to arrange a fourth shielding plate 27 having an L-shaped cross section so as to extend between the left and right side plates 4 b and 4 c. ing. The upper end of the fourth shielding plate 27 exists slightly below the lower end position of the oil drain hole 26. A water intake port 29 is formed in the front side plate 4d so as to face the lower position of the water intake tank 28. A hose 30 for removing the purified waste water is connected to the water intake port 29.
As shown in FIGS. 1 and 2, the front side plate 4d is provided with a first drain pipe 31 for cleaning facing the lowermost position (first sludge pool S1) of the second separation tank 7. Has been. The first drain pipe 31 is provided with a cock 32. Similarly, the front side plate 4d is provided with a second drain pipe 33 for cleaning so as to face the lowermost position (second sludge reservoir S2) of the fourth separation tank 9. The second drain pipe 33 is provided with a cock 32.
Wheels 35 for conveying the oil / water separator 1 are disposed on the bottom plate 3. The liquid tank 5 is heated to a predetermined temperature by a heater (not shown).

The operation of the oil / water separator 1 of the first embodiment having such a configuration will be described.
Waste water mixed continuously with oil from the opening 11 is introduced into the first separation tank 6 by a known introduction means. Waste water is largely separated into a water layer and an oil layer from the first separation tank 6 to the oblique passage 13, and sludge settles in the oblique passage 13, and gradually accumulates on the lower swash plate 14b and the lower swash plate 14b. It flows down and accumulates at the lowest position (first sludge pool S1) of the second separation tank 7 of the lower swash plate 14b. At the stage where the wastewater flows down the oblique passage 13, a large amount of oil is floating in the water layer. The separated water layer and oil layer flow out into the second separation tank 7 from the oblique passage 13 by the pressure of the waste water introduced one after another. When the oil layer reaches the second separation tank 7, it quickly rises to the upper layer of the water layer by its buoyancy. At the same time, bubbles generated by the stirring action of the oil layer and drainage float on the liquid surface.
At this stage, a considerable amount of oil is removed as an oil layer, but a large amount of oil (most of which is oil lumps) still remains in the water layer. In the second separation tank 7, the water layer that flows in from the first separation tank is pushed by the waste water that flows in one after another, and floats obliquely rearward along the inclined surface of the back surface of the second partition wall 15. . When oil lumps in the water layer come into contact with the second partition wall 15, they float along the inclined surface. The density of oil lumps in the vicinity of the inclined surface becomes higher, and the oil dams gradually grow in contact with each other, increasing their buoyancy and successively ascending. The water layer continuously flows out from the first communication hole 17 in the upper part of the second partition wall 15 into the third separation tank 8 while discharging the oil dust to the upper layer.

An aqueous layer containing oil lumps that have not been removed in the second separation tank 7 flows into the third separation tank 8. At this time, most of the bubbles reaching the upper part of the liquid surface are blocked by the bubble shielding plate 24 and are blocked so as not to flow further downstream. Furthermore, the momentum of the waste water that has reached the third separation tank 8 is attenuated by interfering with the barrier 25. Such an oil layer is sequentially discharged from the oil drain hole 26 formed at the oil layer position, and is collected or discarded. In addition, if sludge remains at this stage, the settled sludge is deposited on the second partition wall 15 and gradually accumulates on the second partition wall 15 and then flows down on the second partition wall 15 and flows into the second partition wall 15. 4 is accumulated in the lowermost position (second sludge pool S2) of the separation tank 9.
Finally, the water layer reaches the fourth separation tank 9 from the third communication hole 23, and is further taken out from the water intake port 29 at the lower position of the water intake tank 28 and recovered or discarded.
Further, the sludge accumulated in the first and second sludge pools S1, S2 is discharged from the first and second drain pipes 31, 33 by operating the cock 32 as appropriate.

With this configuration, the oil / water separator 1 according to the first embodiment has the following effects.
(1) The oil content can be efficiently removed from the water layer simply by passing the waste water mixed with oil and water through the four tanks 6 to 7, and a large amount of waste water can be separated.
(2) Although many oil lumps are still diffusing in the water layer in the second separation tank 7, the oil dams grow when they collide with the second partition wall 15 and move along the inclined surfaces. Therefore, oil lumps can be smoothly removed from the water layer. Further, since the second partition wall 15 is an inclined surface that is inclined toward the third separation tank 8 toward the upper part, the rise of the oil dam is promoted, and the prompt growth of the grown oil dam is promoted.
(3) It is characterized in that sludge in the waste water is sufficiently settled and retained by flowing down the long oblique passage 13, and before sludge that interferes with the growth of oil lumps reaches the second separation tank 7 Since it can be removed in large quantities, the oil removal efficiency of wastewater is improved.
(4) The lower end of the oil drain hole 26 exists at a position slightly lower than the horizontal line passing through the upper end of the second partition wall 15. Therefore, only the oil component that always floats upward is discharged from the oil discharge hole 26, and the water layer portion is not discharged.
(5) Since the water intake tank 28 surrounded by the fourth shielding plate 27 is provided in the fourth separation tank 9, for example, the liquid surface is temporarily lowered with sludge discharge, etc. Even if the oil layer is lowered and the oil component enters the fourth separation tank 9, the oil component enters the intake tank 28 because the oil is blocked by the fourth shielding plate 27. There is nothing.
(6) The oblique passage 13, the second separation tank 7, and the third separation tank 8 are arranged to overlap in the vertical direction, and the wastewater treatment path is configured to be very long. It can be made compact and is advantageous in terms of space.

(Embodiment 2)
A second embodiment will be described with reference to FIG. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
In the oil / water separator 51 according to the second embodiment, the length of the upper swash plate 14a constituting the oblique passage 13 is shorter than that of the first embodiment. This is because even if the upper swash plate 14a is short, sludge is deposited and flows down on the lower swash plate 14b, so that the sludge removal effect can be obtained as in the first embodiment. Further, an auxiliary inclined plate 52 for accelerating the growth of oil lumps is disposed at a position in front of the upper swash plate 14a. The auxiliary inclined plate 52 is a plate body that is rearwardly inclined toward the upper side, and extends between the left and right side plates 4b and 4c.

(Embodiment 3)
A third embodiment will be described with reference to FIG. In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
The oil / water separator 61 of the third embodiment has a structure in which a plurality of sets (here, three sets) are connected with the first to third separation tanks 6 to 8 in the oil / water separator 1 of the first embodiment as one set. ing. Each adjacent pair is partitioned by a fifth partition wall 62. As shown in FIG. 3, the third separation tank 8 disposed last is communicated with the fourth separation tank 9 at the end of the liquid tank 5. An oil drain hole 26 is formed only in the final third separation tank 8.
In the third embodiment, the same actions and effects as in the first embodiment are achieved, but in addition, since the waste water passes through the first to third separation tanks 6 to 8 one after another, almost oil lumps are recognized in the water. It becomes possible to remove it cleanly to the extent that it is not possible.

It should be noted that the present invention can be modified and embodied as follows.
In each of the above embodiments, the second partition wall 15 extends obliquely rearward at an angle of 35 degrees with respect to the horizontal. Although it is preferable to raise it as slowly as possible for the growth of oil lumps, it cannot be made so horizontal in view of the efficiency of oil removal. Therefore, the angle of the second partition 15 is preferably in the range of 30 to 50 degrees with respect to the horizontal.
In the above embodiment, the second partition wall 15 extends from the front side plate 4d, but may be configured to extend from the bottom plate 3.
-The drain pipes 31 and 33 as discharge parts for discharging sludge may have a shape other than the above. In the above description, the sludge is discharged by the water pressure in the liquid tank 5, but a structure in which the sludge is sucked by a pump or the like may be used.
-It is also free to use this device 1, 51, 61 as a part of a plant by connecting it to other equipment. In that case, you may make it connect another tank (for example, a precipitation tank and a filtration tank) before and behind the four tanks 6-9.
・ It is free to remove oil and take purified water by means other than the above.
-An oil skimmer may be provided in the middle of the route.
Each of the first to third embodiments has been described by simplifying the structure of the apparatus, and is merely an example. Accordingly, the structure of the partition walls 12, 15, 21 and the structure of the members constituting the liquid tank 5 such as the canopy 2a to 2c liquid are not limited to the above.
In the case where the first to third separation tanks 6 to 8 in the oil / water separator 61 of the third embodiment are used as one set and many sets are connected, it is arbitrary how many sets are connected. You may make it connect 10 sets or more from several sets.
-Besides, it is free to implement in a mode that does not depart from the gist of the present invention.

The perspective view of the oil-water separator of Embodiment 1 of the present invention. Explanatory drawing which materialized the principle of the same oil-water separator. Explanatory drawing which actualized the principle of the oil-water separator of Embodiment 2. FIG. Explanatory drawing which actualized the principle of the oil-water separator of Embodiment 3. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,51,61 ... Oil-water separation apparatus, 5 ... Liquid tank, 6 ... 1st separation tank, 7 ... 2nd separation tank, 8 ... 3rd separation tank, 12 ... 1st partition, 13 ... Oblique shape A passage 15, a second partition 21, a third partition 24, a foam shielding plate as a foam blocking member, and 25 a barrier as a water suppression member.

Claims (7)

In an oil-water separator equipped with a liquid tank for separating the oil from wastewater mixed with oil,
The liquid tank includes first to fourth separation tanks arranged in series, which are partitioned by first to third partition walls,
The first separation tank is provided with an introduction port for introducing waste water, and an inclined passage for guiding the introduced waste water obliquely forward and downward is provided from the first separation tank to the second separation tank. Passing through the lower position and communicating with the lower front position of the second separation tank,
The second partition wall extends rearward and obliquely upward with the bottom or side surface of the liquid tank as a base, and the second separation tank is formed by a first communication hole formed in the upper part of the second partition wall. Communicated with the third separation tank,
The oil / water separator according to claim 3, wherein the third separation tank communicates with the fourth separation tank through a second communication hole formed near the bottom of the third partition wall. In an oil-water separator equipped with a liquid tank for separating the oil from wastewater mixed with oil,
The liquid tank includes first to fourth four kinds of separation tanks arranged in series and partitioned by first to third partition walls,
The first separation tank is provided with an introduction port for introducing waste water, and an inclined passage for guiding the introduced waste water obliquely forward and downward is provided from the first separation tank to the second separation tank. Passing through the lower position and communicating with the lower front position of the second separation tank,
The second partition wall extends rearward and obliquely upward with the bottom or side surface of the liquid tank as a base, and the second separation tank is formed by a first communication hole formed in the upper part of the second partition wall. Communicated with the third separation tank,
The third separation tank is communicated with the first separation tank by a second communication hole formed near the bottom of the third partition;
A plurality of the first to third separation tanks are arranged as a set, and the third separation tank is formed near the bottom of the third partition wall at the end of the liquid tank. An oil-water separator, wherein the oil / water separator is communicated with the fourth separation tank through four communication holes. The oil / water separator according to claim 1 or 2, wherein a foam blocking member is suspended from the upper position between the second partition and the third partition. The one or a plurality of water flow suppression members that do not seal the bottom side and the top side are disposed in the third separation tank and downstream of the foam blocking member. The oil-water separator in any one of -3. An oil discharge port is provided at an upper position of the third separation tank, and an upper end of the second partition wall, a lower end of the foam blocking member, and a lower end of the oil discharge port are arranged in a substantially horizontal state. The oil-water separator according to claim 3. The oil / water separation according to any one of claims 1 to 5, wherein the upper surface of the second partition wall also serves as a sludge flow lower surface for causing sludge settled in the third separation tank to flow forward. apparatus. The oil / water separator according to any one of claims 1 to 6, wherein an auxiliary inclined plate for accelerating the growth of oil lumps is disposed in the second separation tank.

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