JP2022129028A - Wastewater filtration device and wastewater filtration method - Google Patents

Abstract

To provide a compact wastewater filtration device.SOLUTION: A wastewater filtration device 1 includes: a membrane immersion tank 2 for receiving waste water; a filtration membrane device 3 immersed in the membrane immersion tank 2; treated water discharge means 7 connected to an outlet side of the filtration membrane device 3 for discharging treated water of the waste water treated by the filtration membrane device 3 to the outside of the membrane immersion tank 2; and sludge discharge means 9 provided in an upper part of the membrane immersion tank 2 for discharging sludge generated from the waste water and floating on a surface of the waste water to the outside of the membrane immersion tank 2.SELECTED DRAWING: Figure 1

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste water filter and a waste water filtration method, and more particularly to a waste water filter for treating scrubber waste water from ships.

Techniques for filtering oil-containing wastewater to reduce the volume are known. One example of oily wastewater is scrubber wastewater discharged from a ship's exhaust gas scrubber. An exhaust gas scrubber is a device that removes sulfur oxides (SOx) contained in the exhaust gas of a diesel engine mounted on a ship. There are several types of exhaust gas scrubbers, one of which is a water cleaning type. In the water-cleaning exhaust gas scrubber, cleaning water is sprayed onto exhaust gas from a diesel engine, and the sprayed cleaning water is brought into gas-liquid contact with the exhaust gas to absorb and remove SOx. In addition to SOx, the scrubber wastewater contains fine particles such as dust contained in the exhaust gas, oil, aromatic hydrocarbons, and the like. Scrubber effluent can be cleaned, for example, by a filtration membrane device.

Patent Literature 1 discloses an oil-containing wastewater treatment system in which a separation tank for float-separating the oil content of oil-containing wastewater is provided upstream of a membrane soaking tank in which a hollow fiber membrane module is immersed. Scrubber wastewater from which oil has been separated in advance in the separation tank is supplied to the membrane soaking tank, and is further filtered by the filtration membrane device in the latter stage.

JP 2013-52364 A

Since the oil-containing wastewater treatment system described in Patent Document 1 includes a separation tank and a membrane soaking tank, there is room for improvement in terms of installation area.

An object of the present invention is to provide a compact waste water filter.

The waste water filtration apparatus of the present invention comprises a membrane immersion tank for receiving waste water, a filtration membrane device immersed in the membrane immersion tank, and an outlet side of the filtration membrane device connected to the filtration membrane device to filter waste water treated by the filtration membrane device. It has a treated water discharge means for discharging the treated water to the outside of the membrane immersion tank, and a sludge discharge means provided in the upper part of the membrane immersion tank for discharging the sludge generated from the waste water and floating on the liquid surface of the waste water to the outside of the membrane immersion tank. .

ADVANTAGE OF THE INVENTION According to this invention, a compact waste water filtration apparatus can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the waste water filtration apparatus which concerns on the 1st Embodiment of this invention. It is a schematic block diagram of the waste water filtration apparatus which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram of the waste water filtration apparatus which concerns on the modification of the 2nd Embodiment of this invention. It is a schematic block diagram of the waste water filtration apparatus which concerns on the 3rd Embodiment of this invention.

Several embodiments of the present invention will now be described with reference to the drawings. INDUSTRIAL APPLICABILITY The present invention is mainly applied to a wastewater filtering device for filtering oil-containing wastewater. The wastewater filtration device described below is installed on a ship and treats scrubber wastewater discharged from the ship's exhaust gas scrubber. However, oil-containing wastewater is not limited to scrubber wastewater, and the present invention can be widely applied to the treatment of liquids containing oil, such as wastewater containing oil residue discharged from food factories. Scrubber waste water contains oil and suspended solids (SS), but the present invention can also be applied to filtration devices that filter waste water that does not contain oil, such as liquids containing highly viscous substances.

(First embodiment)
FIG. 1 shows a schematic configuration diagram of a waste water filtration device 1 according to a first embodiment of the present invention. FIG. 1(a) is a side cross-sectional view of the waste water filtration device 1 (cross-sectional view along line AA in FIG. 1(b)), and FIG. 1(b) is from line BB in FIG. 1(a). FIG. 1(c) is a developed side view along line CC of FIG. 1(b). A wastewater filtration apparatus 1 for oil-containing wastewater has a membrane immersion tank 2 into which oil-containing wastewater is introduced and receives the oil-containing wastewater, and a filtration membrane device 3 housed in the membrane immersion tank 2 .

The membrane immersion bath 2 has a generally cylindrical shape, that is, a circular shape on a plane parallel to the liquid surface of the oil-containing waste water. The membrane immersion tank 2 has a volume sufficiently larger than the installation space of the filtration membrane device 3, and the space between the membrane immersion tank 2 and the filtration membrane device 3 is prevented from being clogged with oil-containing solids. be. In order to suppress adhesion of oil-containing solids, it is preferable that the membrane immersion tank 2 is made of a material such as stainless steel and/or the inner surface thereof is lined with polyethylene. The membrane dipping bath 2 is also preferably made of PE (polyethylene), PVC (polyvinyl chloride), PTFE (polytetrafluoroethylene) or ceramic. The top of the membrane immersion bath 2 is opened.

The filtration membrane device 3 is immersed in the oil-containing wastewater introduced into the membrane soaking tank 2 to filter the oil-containing wastewater. The filtration membrane device 3 has bundles 3A and 3B in which a plurality of hollow fiber membrane filters (not shown) are bundled, and the plurality of hollow fiber membrane filters of each bundle 3A and 3B has a common upper support portion 4A and lower support portion. 4B and is supported. The hollow fiber membrane filter is not covered with a casing or the like, and is exposed to the oil-containing wastewater of the membrane soaking tank 2 . The oil-containing wastewater that contacts the side wall of the hollow fiber membrane filter from the outside of the hollow fiber membrane filter is filtered by the side wall of the hollow fiber membrane filter, and the oil content remains on the outside of the side wall, and the oil content is removed or reduced. enters the inner space of the hollow fiber membrane filter. In the following description, the outer space of the hollow fiber membrane filter is called the primary side space, and the inner space of the hollow fiber membrane filter is called the secondary side space. The material of the hollow fiber membrane filter is not limited as long as it is highly hydrophilic, and examples thereof include PTFE (polytetrafluoroethylene), PES (polyethersulfone), and PAN (polyacrylonitrile). Although two bundles 3A and 3B are shown in FIG. 1(a), the number of bundles is not limited at all.

The wastewater filtration device 1 has an oil-containing wastewater supply line L1 for supplying oil-containing wastewater to the membrane immersion tank 2 . The oil-containing wastewater supply line L1 is connected to an exhaust gas scrubber (not shown) of the ship, and supplies oil-containing wastewater generated by the exhaust gas scrubber to the membrane immersion tank 2 . A coagulant addition means 5 for adding a coagulant to the oil-containing wastewater supplied to the membrane soaking tank 2 is provided in the oil-containing wastewater supply line L1. The coagulant addition means 5 includes a coagulant tank 5A, a coagulant supply line 5B connecting the coagulant tank 5A to the oil-containing wastewater supply line L1, and a coagulant injection pump 5C provided on the coagulant supply line 5B. have. Flocculants include inorganic coagulants such as polyaluminum chloride (PAC), ferric chloride, and aluminum sulfate, which coarsen (flocculate) contaminants, especially fine particles, contained in scrubber wastewater, and filter membrane device 3 enhances the capture effect of In some cases, an anionic, cationic, nonionic, or other polymeric flocculation aid may be added. The coagulant is agitated inside the oil-containing waste water supply line L1. Although not shown, a separate tank for adding the flocculant may be provided, and this tank may be provided with a stirring device such as a stirring blade.

The wastewater filtration device 1 has a treated water discharge means 7 connected to the outlet side of the filtration membrane device 3, that is, to the secondary side space. The treated water discharge means 7 discharges the treated water of the oil-containing waste water filtered by the filtration membrane device 3 to the outside of the membrane soaking tank 2 . The treated water discharge means 7 is connected to the suction line 7A, the suction pump 7B provided in the suction line 7A, and the suction line 7A, and stores the treated water of the oil-containing wastewater of the filtration membrane device 3, preferably part of it. It has a treated water tank 7C. The suction line 7A is connected to the secondary space of each hollow fiber membrane filter. The suction pump 7B sucks the treated water into the secondary space. Although illustration is omitted, the water head pressure may be used to suck the treated water. For example, by arranging the suction line 7A vertically so that the treated water flows downward, it is possible to obtain a driving force for sucking the treated water into the secondary space. The treated water sucked into the secondary space can be discharged outside the system (for example, into the sea) after it is confirmed that it satisfies a predetermined water quality standard.

A part of the treated water is stored in the treated water tank 7C and used as backwash water. A backwash line L2 is connected to the treated water tank 7C. The backwash line L2 joins the suction line 7A at a position between the filtration membrane device 3 and the suction pump 7B. The backwash line L2 is provided with a backwash pump 8 for pumping the backwash water. At the time of backwashing, the treated water stored in the treated water tank 7C is supplied to the secondary space of the hollow fiber membrane filter through the backwash line L2, and oil and the like adhering to the membrane surface of the hollow fiber membrane filter are peeled off. It is released into the secondary space. If there is utility water, such as when installing the drainage filter device 1 on a ship, the utility water may be used as backwash water. Although not shown, the suction pump 7B and the backwash pump 8 can be used in common by rearranging the suction line 7A and the backwash line L2 and switching the suction line 7A and the backwash line L2 by a valve.

A drain line L3 is connected to the bottom of the membrane immersion tank 2 for discharging oil-containing waste liquid with a high specific gravity that has settled on the bottom of the membrane immersion tank 2 . The drain line L3 is connected to a waste liquid storage tank (not shown) for storing the oil-containing waste liquid from the membrane immersion tank 2, and the drain line L3 is provided with a drain pump (not shown) for transferring the oil-containing waste liquid to the waste liquid storage tank. there is The oil-containing waste liquid may be taken out from the membrane soaking tank 2 to the drain line L3 continuously or intermittently.

The wastewater filtration device 1 has sludge discharge means 9 for discharging sludge (scum) generated from oil-containing wastewater to the outside of the membrane soaking tank 2 . The sludge discharge means 9 is provided above the membrane soaking tank 2 . The sludge discharge means 9 has a rotatable scraper 9A, a sludge recovery section 9B, and a sludge discharge line 9C connected to the sludge recovery section 9B. The scraper 9A is provided in the upper part of the membrane soaking tank 2, and scrapes the sludge generated from the oil-containing wastewater stored in the membrane soaking tank 2 and floating on the liquid surface of the oil-containing wastewater. The scraper 9A has a rotating shaft 9A1 and at least one, preferably a plurality of (four in this embodiment) blades 9A2 fixed to the rotating shaft 9A1. The blades 9A2 are provided at equal intervals around the rotation axis 9A1 and radially from the rotation axis 9A1. The blade 9A2 is positioned at a height where the lower end is in contact with the liquid surface of the membrane dipping bath 2 or slightly below the liquid surface. The rotating shaft 9A1 extends in the vertical direction, that is, in the direction perpendicular to the liquid surface of the membrane immersion tank 2. As shown in FIG. The center of the rotary shaft 9A1 of the scraper 9A is concentric with the central axis of the film soaking tank 2. A motor 9D is connected to the rotating shaft 9A1. As shown in FIG. 1(b), the rotating shaft 9A1 is rotationally driven by a motor 9D, and the blades 9A2 scrape up the sludge S floating on the liquid surface of the membrane soaking tank 2. As shown in FIG. Since the scraper 9A rotates at a low speed, almost no centrifugal force acts on the sludge S, and the sludge S moves substantially in the circumferential direction.

A sludge recovery section 9B is provided at a position overlapping the movement range of the scraper 9A in the vertical direction. The sludge collecting part 9B is a box-shaped tank or container for collecting the sludge scraped by the scraper 9A. A sludge collection plate 9E is provided upstream of the sludge collector 9B in the rotation direction D of the scraper 9A. As shown in FIG. 1(c), the sludge collection plate 9E slopes upward toward the sludge collection section 9B. As indicated by the dashed line, the blade 9A2 abuts against the sludge collection plate 9E and undergoes bending deformation. The blade 9A2 pushes the sludge S forward along the sludge collection plate 9E and drops it into the sludge collection section 9B. After that, the blade 9A2 restores its original shape and continues to rotate past the sludge collector 9B. The sludge recovered by the sludge recovery section 9B is discharged out of the system through the sludge discharge line 9C. A pump may be provided to transfer sludge to the sludge discharge line 9C.

The waste water filtration device 1 includes a pressurized water generating means 10 for generating pressurized water in which air is dissolved, a treated water supply line L4 connecting the treated water tank 7C to the pressurized water generating means 10, and the pressurized water generating means 10 connected to the membrane soaking tank 2. and a pressurized water supply line L5. The pressurized water generator 10 pressurizes the treated water supplied from the treated water tank 7C through the treated water supply line L4 to dissolve air in the treated water. The pressurized water generating means 10 has a pressurizing pump 10A and a pressurizing tank 10B. The treated water supplied from the treated water supply line L4 is pressurized by the pressure pump 10A. A compressed air supply line 10C joins the treated water supply line L4 between the pressurization pump 10A and the pressurization tank 10B. The compressed air supply line 10C is connected to a compressor (not shown) that produces compressed air. An amount of air corresponding to the pressurized pressure is dissolved in the treated water, and the pressurized water in which the air is dissolved is stored in the pressurized tank 10B. Pressurized water is supplied from the pressurized tank 10B to the lower portion of the membrane soaking tank 2 through the pressurized water supply line L5. The pressurized water supply line L5 is connected to the oil-containing waste water supply line L1, but may be directly connected to the bottom or bottom of the membrane immersion tank 2.

When the pressurized water is introduced into the membrane soaking tank 2, the pressure is reduced to a pressure close to the atmospheric pressure. Microbubbles are generated in the membrane immersion bath 2 by the dissolved air becoming supersaturated. Microbubbles are likely to occur at the solid-liquid interface. For this reason, fine air bubbles adhere to the oil or the like, causing the oil or the like to float. On the other hand, substances with high specific gravity settle, and substances with similar specific gravity to oil-containing wastewater float in the oil-containing wastewater. Particularly in this embodiment, since the fine particles are coarsened by the flocculant, more oil and the like can be floated. The pressurized water generating means 10 can also be omitted. In this case, flotation separation and sedimentation separation are performed due to the difference in specific gravity.

The waste water filter device 1 operates as follows. The oil-containing waste water from the exhaust gas scrubber is supplied to the membrane soaking tank 2 through the oil-containing waste water supply line L1. Due to the suction pressure of the suction pump 7B, mainly water in the oil-containing waste water moves from the primary side space of the hollow fiber membrane filter to the secondary side space, and oil and the like are trapped in the hollow fiber membrane filter. During this time, sludge floating on the liquid surface of the membrane immersion tank 2 is scraped by the scraper 9A and discharged from the sludge collection section 9B. After performing the filtering process by operating the suction pump 7B for a certain period of time, the suction pump 7B is stopped, a valve (not shown) is switched, and backwashing is performed for a short time by the backwashing line L2 (this backwashing is called simple backwashing). ) is preferred. By repeating filtration and simple backwashing as a set, the filtration process can be performed while maintaining the performance of the filtration membrane device 3 . Moreover, since the scraper 9A discharges the sludge, it is possible to prevent the sludge from overflowing from the membrane immersion tank 2 and contaminating the surroundings of the membrane immersion tank 2 with sludge.

Conventionally, as disclosed in Patent Literature 1, a separation tank has been arranged upstream of the membrane soaking tank 2 for floating and separating the oil content of the oil-containing wastewater. On the other hand, in the present embodiment, flotation separation and sedimentation separation are performed in the membrane soaking tank 2 . That is, substances with a large specific gravity settle and accumulate on the bottom of the membrane soaking tank 2, and are periodically withdrawn through the drain line L3. Sludge with a small specific gravity floats and floats near the liquid surface of the membrane soaking tank 2 . At the same time, filtration of oil-containing wastewater is performed in the membrane soaking tank 2 . Thus, in this embodiment, since the membrane soaking tank 2 also has the function of a conventional separation tank, a separation tank is not required, and cost reduction and installation area reduction are possible. In particular, reducing the footprint is advantageous for ships where the footprint is severely restricted.

In addition, in the membrane soaking tank 2, since the oil-containing waste water is filtered at the same time, the density of oil and the like in the primary space of the membrane soaking tank 2 increases. That is, water in the oil-containing wastewater flows out to the secondary space through the wastewater filtration device 1, but oil and the like remain in the primary space, resulting in an increase in the density of the oil and the like in the primary space. . Therefore, the frequency of contact between the oil and the air bubbles, or the contact efficiency, increases, and more oil and the like can be floated as sludge. Such an effect is obtained by integrating the separation tank and the membrane soaking tank 2 .

The cross-sectional shape of the membrane immersion bath 2 may be a shape other than a circle, such as an ellipse. In this case, the scraper 9A may be arranged somewhat eccentrically from the center of the membrane immersion tank 2, or two or more scrapers 9A may be installed.

(Second embodiment)
FIG. 2 is a side sectional view similar to FIG. 1(a), showing a schematic configuration of a waste water filter device 101 according to a second embodiment of the present invention. The sludge discharge means 109 includes a float 109A provided so as to float on the surface of the oil-containing wastewater, a sludge receiver 109B supported by the float 109A, a sludge drain pump 109C housed in the sludge receiver 109B, and sludge drain. and a sludge discharge line 109D connected to the pump 109C. The float 109A is arranged around the sludge receiving part 109B and maintains a constant vertical position with respect to the liquid surface of the membrane soaking tank 2 . The float 109A consists of a plurality of float elements (not shown) equally spaced around the sludge receiver 109B. However, the configuration of the float 109A is not limited as long as a flow path for the sludge to flow into the sludge receiving portion 109B is ensured.

The sludge receiver 109B is a box-shaped tank that receives sludge floating on the liquid surface. The sludge receiving part 109B has a sludge inflow part 109E into which sludge flows. The sludge inflow portion 109E is an upper opening of the sludge receiving portion 109B, but may be an opening provided on the side surface of the sludge receiving portion 109B. The sludge receiving portion 109B is supported by the float 109A so that sludge can flow in from the sludge inflow portion 109E. Specifically, the sludge receiving portion 109B is supported by the float 109A so that its upper end, ie, the sludge inflow portion 109E, is substantially aligned with the liquid surface of the membrane soaking tank 2 or slightly above the liquid surface. Therefore, the sludge floating on the liquid surface flows into the sludge receiver 109B and is discharged out of the system through the sludge discharge line 109D by the sludge drain pump 109C installed in the sludge receiver 109B. It is preferable that the sludge inflow part 109E is positioned not much below the liquid surface of the membrane immersion tank 2 so that sludge mainly flows into the sludge receiving part 109B and oil-containing waste water does not flow in as much as possible. In order to absorb the relative displacement of the sludge receiving part 109B with respect to the membrane immersion tank 2 due to fluctuations and rocking of the liquid surface, at least the section between the sludge receiving part 109B and the penetration part of the membrane immersion tank 2 of the sludge discharge line 109D is It is preferable to use a flexible tube such as a flexible tube.

According to this embodiment, since the sludge receiver 109B is supported by the float 109A, sludge can be reliably discharged even if the liquid surface of the membrane immersion tank 2 fluctuates. When the drainage filter device 101 is installed on a ship, the liquid surface of the membrane immersion tank 2 fluctuates. For this reason, for example, in the first embodiment, the oil-containing waste water may flow out from the sludge recovery section 9B together with the sludge, and the sludge separation efficiency may decrease. Conversely, sludge does not flow into the sludge recovery section 9B, and the sludge discharge efficiency may decrease. In this embodiment, even when the liquid surface fluctuates, the positional relationship between the liquid surface and the sludge inflow portion 109E is kept constant, so that only the sludge can be reliably discharged. Although the sludge receiving part 109B is not fixed to the membrane soaking tank 2, it is preferably provided near the center of the membrane soaking tank 2 in order to efficiently collect the sludge. Moreover, a plurality of sludge receivers 109B can be provided as needed.

(Modification)
FIG. 3 is a side sectional view similar to FIG. 1(a), showing a schematic configuration of a waste water filtering device 201 according to a modification of the second embodiment of the present invention. The sludge discharge means 209 includes a float 209A provided inside the membrane immersion tank 2 so as to float on the surface of the oil-containing wastewater, a sludge drainage pump 209B provided in the oil-containing wastewater and supported by the float 209A, and a sludge drainage. and a sludge discharge line 209C connected to the pump 209B. The sludge drain pump 209B is supported by the float 209A via a support structure 209D so that the sludge suction port 209E is positioned near the liquid surface. Float 209A can have a configuration similar to float 109A of the second embodiment. Sludge floating on the liquid surface is directly sucked by the sludge drain pump 209B and discharged out of the system through the sludge discharge line 209C. Even if the liquid surface of the membrane soaking tank 2 fluctuates, the positional relationship between the liquid surface and the suction port 209E of the sludge drainage pump 209B is kept constant. Therefore, even when the drainage filter device 201 is installed on a ship, it is possible to reliably discharge only sludge, as in the second embodiment. Although the sludge drainage pump 209B is not fixed to the membrane soaking tank 2, it is preferably provided near the center of the membrane soaking tank 2 in order to efficiently collect the sludge. Also, a plurality of sludge drainage pumps 209B can be provided as needed. It is the same as the second embodiment in that the description is omitted.

(Third embodiment)
FIG. 4 is a side cross-sectional view similar to FIG. 1(a), showing a schematic configuration of a waste water filter device 301 according to a third embodiment of the present invention. The sludge discharge means 309 has a roof portion 309A covering the upper surface of the membrane soaking tank 2 and a sludge discharge line 309B connected to the roof portion 309A. The roof portion 309A seals the membrane immersion bath 2 . The sludge discharge line 309B communicates with the space 309C below the roof portion 309A. As the amount of sludge floating on the liquid surface increases, the sludge rises from the liquid surface and fills the space 309C between the roof portion 309A and the liquid surface. Sludge is discharged from the sludge discharge line 309B. A pump may be provided to transfer sludge to the sludge discharge line 309B. The sludge discharge line 309B opens to the roof portion 309A, but may extend downward through the space 309C and open in the space 309C. Also, a plurality of sludge discharge lines 309B may be provided. A pair of screws that mesh with each other may be installed in the space 309C. The screw is preferably provided so that the meshing portion is positioned directly below the opening of the sludge discharge line 309B. The two screws rotate in a direction with an upward velocity component at the mesh. Sludge is lifted upward by a pair of screws and transferred to sludge discharge line 309B. In this embodiment, since the membrane immersion tank 2 is sealed, even if the liquid surface oscillates, the oil-containing wastewater overflows from the membrane immersion tank 2, and the surroundings of the membrane immersion tank 2 may be contaminated with the oil-containing wastewater. do not have. This embodiment can be used in combination with the first and second embodiments.

Reference Signs List 1, 101, 202, 301 Wastewater filtration device 2 Membrane immersion tank 3 Filtration membrane device 5 Coagulant addition means 7 Treated water discharge means 7C Treated water tank 9, 109, 209, 309 Sludge discharge means 9A Scraper 9B Sludge recovery unit 9C, 109D , 209C, 309B sludge discharge line 10 pressurized water generating means 109A, 209A float 109B sludge receiving portion 109C, 209B sludge drainage pump 109E sludge inflow portion 309A roof portion L4 treated water supply line L5 pressurized water supply line

Claims (10)

a membrane soaking tank for receiving wastewater;
A filtration membrane device immersed in the membrane immersion tank;
Treated water discharge means connected to the outlet side of the membrane filtration device and discharging treated water of the waste water treated by the membrane filtration device to the outside of the membrane immersion tank;
a sludge discharge means provided in the upper part of the membrane immersion tank for discharging sludge generated from the waste water and floating on the liquid surface of the waste water to the outside of the membrane immersion tank;
A wastewater filtration device having a a pressurized water generating means for generating pressurized water in which air is dissolved;
a pressurized water supply line connecting the pressurized water generating means to the membrane immersion tank;
The wastewater filtration device according to claim 1, comprising: A treated water tank storing a portion of the treated water;
a treated water supply line connecting the treated water tank to the pressurized water generating means;
3. The waste water filtering device according to claim 2, wherein said pressurized water generating means pressurizes said treated water supplied from said treated water tank through said treated water supply line to dissolve air in said treated water. 4. The waste water filtering device according to any one of claims 1 to 3, further comprising a flocculating agent adding means for adding a flocculating agent to said waste water supplied to said membrane soaking tank. The sludge discharge means is
a rotatable scraper provided at the top of the membrane soaking tank to scrape the sludge;
a sludge recovery unit provided at a position overlapping the movement range of the scraper in the vertical direction;
a sludge discharge line connected to the sludge collector;
The wastewater filtration device according to any one of claims 1 to 4, comprising: The sludge discharge means is
a float provided inside the membrane immersion tank so as to float on the liquid surface;
a sludge receiver supported by the float and receiving the sludge;
a sludge drainage pump accommodated in the sludge receiver;
a sludge drain line connected to the sludge drain pump;
The sludge receiving part has a sludge inflow part into which the sludge flows,
The wastewater filtration device according to any one of claims 1 to 4, wherein the sludge receiving portion is supported by the float so that the sludge can flow in from the sludge inflow portion. The sludge discharge means is
a float provided inside the membrane immersion tank so as to float on the liquid surface;
a sludge drainage pump supported by the float and provided in the drainage;
a sludge drain line connected to the sludge drain pump;
5. The waste water filtering device according to claim 1, wherein said sludge drain pump is supported by said float so that said sludge can flow in from said sludge suction port. The sludge discharge means is
a roof part that covers the upper surface of the membrane immersion tank and seals the membrane immersion tank;
5. The wastewater filtering device according to any one of claims 1 to 4, further comprising a sludge discharge line connected to said roof and communicating with a space below said roof. 9. The waste water filter device according to any one of claims 1 to 8, which is installed on a ship, wherein the waste water contains oil. A wastewater filtration method using a wastewater filtration device having a membrane immersion tank for receiving wastewater and a filtration membrane device immersed in the membrane immersion tank,
discharging sludge generated from the wastewater and floating on the surface of the wastewater to the outside of the membrane soaking tank by a sludge discharging means provided in the upper part of the membrane soaking tank;
discharging the treated water of the wastewater treated by the membrane filtration device to the outside of the membrane immersion tank by a treated water discharge means connected to the outlet side of the membrane filtration device;
Waste water filtration method.

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