JP6411051B2 - Immersion membrane separator and method for operating the same - Google Patents

Description

  The present invention relates to, for example, an immersion type membrane separation apparatus that performs solid-liquid separation and an operation method thereof.

2. Description of the Related Art Conventionally, a technique for performing solid-liquid separation using a flat membrane element is known in wastewater treatment by an activated sludge method in which sewage such as sewage, human waste, domestic wastewater, and factory wastewater is aerobically biodegraded.
The conventional activated sludge method employs a method in which sludge is biodegraded with activated sludge and then the solid-liquid separation between the sludge and the purified water is gravity separated by a sedimentation tank. In the membrane separation activated sludge treatment method, since solid-liquid separation is performed with a membrane, the concentration of activated sludge in the reaction tank can be increased as compared with gravity separation. For this reason, it becomes a processing technique that can increase the processing capacity even in a reaction tank of the same capacity.

A submerged membrane separation apparatus (membrane bioreactor (MBR)) for membrane separation activated sludge treatment using a flat membrane element is, for example, a membrane composed of a plurality of flat membrane elements in an open reaction tank Units are arranged.
Each flat membrane element has a filtrate flow path on the surface or inside of a flat membrane support, and has a filtration membrane covering the surface of the membrane support, and has two or more water collection ports.

A pipe for taking out the filtrate is connected to each water collecting port. The piping is provided with a suction pump. The filtrate is sent to the treated water tank via a pipe.
The liquid to be treated is supplied to the reaction tank from the raw water supply pipe. The raw water supply pipe is provided with a raw water supply pump.
A diffuser tube is disposed directly under each flat membrane element. The air diffuser is connected to a blower installed in the atmosphere by guiding an end different from the end directly below the flat membrane element from the reaction vessel to the outside.

  In this processing apparatus, the liquid to be processed is supplied to the reaction tank by the raw water supply pump, and air is ejected from the air diffuser by driving the blower. The liquid to be treated is raised at a high speed between the elements, a downward flow is formed at a place where the membrane unit of the reaction tank is not installed, and the liquid to be treated in the reaction tank is swirled as a result. The solids contained in the liquid to be treated are prevented from adhering to the element surface. Then, the filtrate passage side of the flat membrane element is intermittently depressurized by intermittent driving of the suction pump, and the intermembrane between the depressurization of the flat membrane element on the filtrate side and the pressurized water pressure on the flat membrane element due to the water level of the reaction tank. Water can be membrane-filtered under a differential pressure, and a filtrate from which a predetermined solid is separated by a membrane from a water collection port via a pipe can be stored in a treated water tank.

In this processing apparatus, the membrane surface of the flat membrane element is washed by the upward flow of the gas-liquid mixture generated by the rise of the air ejected from the diffuser by the drive of the blower, and the membrane in the liquid to be treated is subjected to membrane filtration. Stable membrane filtration operation is performed by suppressing the adhesion of the sludge layer due to the solid content. In recent years, flat membrane elements have been increased in size (lengthened in the height direction) in order to effectively use the upward flow caused by gas-liquid mixing.
Membrane filtration operation is performed continuously, but if it is operated for a certain period of time, dirt that cannot be suppressed by upward flow due to gas-liquid mixing accumulates on the membrane surface, so it is necessary to periodically stop the operation and perform chemical cleaning .

Conventionally, for membrane cleaning, a flat membrane element is immersed in the reaction tank, and the chemical solution is allowed to flow in the direction opposite to the flow of the filtrate with natural flow or a pump. In this state, the film surface (membrane pores) was removed (chemical solution cleaning) by holding for a certain period of time.
However, in the conventional cleaning method, when chemical solution cleaning is performed in a reaction tank for immersion type flat membrane elements arranged in parallel, it is desirable that a sufficient amount of chemical solution flows uniformly into each flat membrane element, Unevenness is likely to occur.
Therefore, it is necessary to flow in the chemical solution until the filtration membrane covering the membrane support is swollen toward the liquid to be treated. As a result, a large amount of chemical solution was required.

In addition, there is a problem that it takes time for the chemical solution to flow in and the filtrate and the chemical solution in the filtrate flow channel are mixed to obtain a uniform concentration, and the time for holding for a certain period of time becomes long.
In addition, if the time for holding the chemical solution is increased, the amount of chemical solution that flows out from the filtration membrane to the liquid to be treated increases, which is effective for cleaning the membrane. It is better to avoid spills as much as possible.

In addition, it is considered that the effect of removing dirt is enhanced by performing aeration cleaning of the film surface during chemical cleaning. In this method, the film surface swells, and if air is diffused in this state, there is a problem that the film is liable to sway, and the welded part of the film may be peeled off or torn.
Therefore, the chemical solution is circulated, and the difference between the amount of inflow fluid flowing into the flat membrane element and the amount of effluent fluid flowing out of the flat membrane element is adjusted to increase or decrease, thereby improving the use efficiency and cleaning efficiency of the chemical solution and further filtering A technique has been proposed in which fouling substances adhering to the surface of the membrane are crushed and separated from the filtration membrane (see, for example, Patent Document 1).

  In addition, in a method for cleaning a flat membrane element having two nozzles for injecting and discharging chemicals in the upper part, the chemical liquid is injected using a water head difference, and the mixed liquid of the chemical liquid and the filtrate stored in the filtration chamber is circulated. The technique to make is proposed (for example, refer patent document 2).

Republished patent 2009-122460 JP 2006-198462 A

However, in Patent Document 1, a circulation system is communicated with one connection part and the other connection part of the membrane module, and this circulation system is communicated with a chemical solution tank for storing a cleaning chemical solution, a chemical solution tank, and one water collecting part. A supply pipe section, a discharge pipe section communicating with the other water collecting section and the chemical liquid tank, and a branch pipe section branched from the supply pipe section and communicated with the chemical liquid tank. However, it requires a supply pump for supplying a chemical solution and a discharge pump for discharging the chemical solution.
Moreover, although patent document 1 discloses connecting a water collection system to both water collection parts at the time of a membrane filtration operation and sucking a filtrate from both water collection parts, in the above-mentioned circulation system, both water collections are disclosed. Since the supply pipe section and the discharge pipe section are connected to the respective sections, there is a problem that the filtrate cannot be sucked without a special device or piping configuration.
Further, in Patent Document 1, when the membrane is washed, the difference liquid amount between the amount of the supply liquid flowing into the membrane module and the amount of the discharge liquid flowing out from the filtrate flow path of the membrane module is adjusted to increase or decrease to supply the difference liquid amount excessively. However, in order to obtain an excessive supply state (a state in which the filtration membrane swells toward the liquid to be treated), the same amount of chemical solution as in the conventional cleaning method is required. .

According to Patent Document 2, at least two nozzles for injecting chemicals and discharging chemicals are connected to the upper part of the substrate so that both surfaces of the substrate are covered in the order of the channel material and the flat membrane, and communicate with the filtration chamber in which the channel material is arranged. Disclosed is a method for cleaning a flat membrane element having a chemical solution injected using a water head difference and circulating a mixed solution of the chemical solution and the filtrate stored in the filtration chamber. Since it is provided in the upper part, there is a possibility that the chemical liquid flowing in from the chemical liquid injection nozzle short-circuits to the chemical liquid discharge nozzle without reaching the filtration chamber.
Further, when Patent Document 2 is applied particularly to a flat membrane element elongated in the height direction, there is a risk that the chemical liquid flowing in from the chemical liquid injection nozzle may short-circuit to the chemical liquid discharge nozzle without reaching the filtration chamber. There is a concern that the lower side membrane surface of the flat membrane element is not sufficiently cleaned, or that the cleaning time is not different from the conventional cleaning method.
Moreover, in patent document 2, in order to close the nozzle for chemical | medical solution injection | pouring at the time of filtration operation, although there are two nozzles, there exists a problem that only one nozzle can be used.

  The present invention has been made in order to solve such a conventional problem, and its object is to perform the separation between the membrane filtration operation by the flat membrane element and the membrane cleaning reliably and easily by switching the on-off valve. Another object of the present invention is to provide a submerged membrane separation apparatus and an operation method thereof.

The submerged membrane separation device according to the present invention includes a flat membrane element having two or more water collection ports for taking out filtrate from the filtration membrane flow path, a reaction tank for immersing the flat membrane element, and a water collection port, respectively. Two water collecting pipes arranged to be opposed to each other, a first on-off valve, a first pipe connected to one of the water collecting pipes, a suction pump for connecting the first pipe to the suction port side, and the other A second pipe connected to the first pipe between the first on-off valve and the suction port of the suction pump; and a second on-off valve provided to the discharge pipe of the suction pump Provided with a filtrate pipe connected to the side, and a chemical solution inlet, one end is connected to the filtrate pipe between the suction pump and the second on-off valve via a third on-off valve, and the other end is A fourth on-off valve is connected to the first pipe between the first on-off valve and the one water collecting pipe. And a third pipe connected Te, the flat membrane element, the two ends of the flat sheet membrane element, one end is the upper end of the dip the flat membrane element, the other end was immersed the A lower end of the flat membrane element, and each of the water collecting ports has one or more upwards at the upper part of the upper end of the flat membrane element and downwards at the lower part of the lower end of the flat membrane element. And the second on-off valve is opened during the membrane filtration operation and closed during the membrane cleaning operation, and the third on-off valve and the fourth on-off valve are closed during the membrane filtration operation and opened during the membrane cleaning operation, suction pump, the first pipe through the one water collecting pipe positioned horizontally disposed to face the current Mizuguchi the lower end from the current Mizuguchi of the lower end of the flat sheet membrane element during membrane filtration operation, and the flat membrane Jer The second pipe from the cement of the upper end of the condenser water inlet through the other water collecting pipe which is located oppositely disposed horizontally on the upper end of the collecting Mizuguchi, sucked to derive the filtrate, the at the time of membrane cleaning operation The chemical solution introduced from the chemical solution introduction unit is sucked from the third pipe to the one water collecting pipe through the first pipe, and the chemical liquid is led out from the other water collecting pipe through the flat membrane element. Aspirate.

The submerged membrane separation apparatus according to the present invention is for cleaning the membrane surface of the flat membrane element by the upward flow of gas-liquid mixing caused by the rise of the air blown by the drive of the blower immediately below the flat membrane element. It is installed and has an air diffuser that ejects air during membrane filtration operation and membrane cleaning operation .
In the submerged membrane separation apparatus according to the present invention, the chemical solution input unit is a chemical solution input port having a check mechanism while having a funnel-shaped input port.
The submerged membrane separation apparatus according to the present invention is a relay tank in which the chemical solution input unit includes an opening-shaped chemical solution input port in a housing and stores the chemical solution introduced into the third pipe by the suction pump. .

In the operation method of the submerged membrane separation device according to the present invention, during the membrane filtration operation, the third on-off valve and the fourth on-off valve of the third pipe are closed, and the first pipe and the second pipe are The suction pump communicates with the first pump and the second pipe with the suction pump and sends the filtrate to the filtrate pipe. During the membrane cleaning operation, the first on-off valve and the second on-off valve And the third on-off valve and the fourth on-off valve of the third pipe are opened, and a predetermined chemical liquid to be introduced in the chemical liquid inlet is fed from the third pipe to the first pipe by the suction pump. And then sucking from the one water collecting pipe to the other water collecting pipe through the flat membrane element, and from the other water collecting pipe to the second pipe and the first water collecting pipe. via one pipe to derive to the third pipe, the flat Inside the element the chemical make up the chemical circulation path to flow from bottom to top.

According to the present invention, while sucking the liquid in the filtrate flow path from one water collecting port, the chemical liquid flows in from the other water collecting port and circulates, so a small amount of chemical liquid is not used until the membrane expands. Each flat membrane element can be filled with a chemical solution to clean the entire membrane surface with a uniform concentration.
In particular, in a flat membrane element that is enlarged in the height direction, it is more effective than flowing in a natural flow and spreading the chemical solution over the entire membrane surface.

According to the present invention, since the cleaning time can be shortened and suction is performed from one side, the outflow of the chemical liquid to the liquid to be processed is suppressed.
According to the present invention, since the film does not swell, even if aeration cleaning is performed at the time of chemical solution cleaning, the film is hardly twisted and the welded portion is not peeled off or torn, so that more effective cleaning is possible.

It is explanatory drawing which shows the membrane filtration driving | running state of the immersion type membrane separator which concerns on 1st embodiment of this invention. It is explanatory drawing which shows the membrane washing | cleaning driving | running state of the immersion type membrane separator which concerns on 1st embodiment of this invention. It is explanatory drawing which shows the membrane filtration driving | running state of the immersion type membrane separator which concerns on 2nd embodiment of this invention. It is explanatory drawing which shows the membrane washing | cleaning driving | running state of the immersion type membrane separator which concerns on 2nd embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a membrane filtration operation state of the submerged membrane separation apparatus 10 according to the first embodiment of the present invention. FIG. 2 shows a membrane cleaning operation state of the submerged membrane separation apparatus 10 according to the first embodiment of the present invention.

In the submerged membrane separation apparatus 10 according to the present embodiment, a membrane unit 13 composed of a plurality of flat membrane elements 15 is arranged in an open reaction tank 11.
Each flat membrane element 15 has a filtrate channel on the surface or inside of a flat plate membrane support, and a filter membrane is disposed so as to cover the surface of the membrane support and communicated with the filtrate channel. Water ports 17a and 17b are provided at both end portions of each flat membrane element 15 (end portions in the vertical direction of the paper surface of FIG. 1). The water collection ports 17a and 17b are connected to water collection pipes 19a and 19b for taking out the filtrate.

  The lower water collecting pipe 19 a is disposed opposite to the water collecting port 17 a at the lower end of the flat membrane element 15. The lower water collecting pipe 19 a is connected to a first pipe 21 having a first on-off valve 23. The first pipe 21 is connected to the suction port of the suction pump 27. The upper water collecting pipe 19 b is disposed so as to face the water collecting port 17 b at the upper end of the flat membrane element 15. The upper water collecting pipe 19 b is connected to the second pipe 25. The second pipe 25 is connected so as to join the first pipe 21 at a junction 21 b on the downstream side of the first on-off valve 23 provided on the first pipe 21 and before the suction side of the suction pump 27.

The discharge side of the suction pump 27 is connected to a filtrate pipe 29 provided with a second on-off valve 31. The filtrate pipe 29 is connected to a treated water tank (not shown) that stores the filtrate.
The discharge side of the suction pump 27 is connected to the third pipe 33 at a merging portion 29 a on the near side of the second on-off valve 31 provided in the filtrate pipe 29. The third pipe 33 is connected to the first pipe 21 at a junction 21 a upstream of the first on-off valve 23 provided in the first pipe 21. The third pipe 33 is provided with a third on-off valve 35 on the side of the joining portion 29 a with the filtrate pipe 29. The third pipe 33 is provided with a fourth on-off valve 37 and a chemical solution inlet 39 on the side of the junction 21 a with the first pipe 21.

The chemical solution introduced from the chemical solution inlet 39 is not particularly limited, but sodium hypochlorite, hydrogen peroxide, hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, citric acid, malic acid, sodium hydroxide, etc. These chemical solutions can be appropriately selected and used.
The liquid to be treated is supplied to the reaction tank 11 through the raw water supply pipe 41. The raw water supply pipe 41 is provided with a raw water supply pump (not shown).
Immediately below the membrane unit 13, there is disposed an air diffusion unit 43 that floats from the bottom of the reaction tank and accommodates it and does not hinder the surroundings. One end of the air supply pipe 47 is connected to the diffuser pipe 45, and the other end is led to the outside of the reaction tank 11 and connected to the blower 49.

Next, the operation of the submerged membrane separation apparatus 10 according to the present embodiment will be described based on FIG.
As shown in FIG. 1, in the submerged membrane separation device 10, when the membrane filtration operation is performed, first, the third on-off valve 35 of the third pipe 33 is prevented so that the filtrate does not flow into the third pipe 33. And the 4th on-off valve 37 is closed. Further, the first on-off valve 23 of the first pipe 21 and the second on-off valve 31 of the filtrate pipe 29 are opened.

Next, the liquid to be treated is supplied to the reaction tank 11 by the raw water supply pump. At the same time, the blower 49 is driven, and the air supplied through the air supply pipe 47 is ejected from the air diffusion pipe 45 toward the membrane unit 13 as indicated by an arrow.
A swirling flow is caused in the liquid to be treated stored in the reaction tank 11 by the ejection of the air. That is, the liquid to be processed is raised between the flat membrane elements 15 at a high speed while accompanying the liquid to be processed in the reaction tank 11 by this jet of air flow, and the membrane unit 13 of the reaction tank 11 is not installed. A downward flow is formed, and the liquid to be treated in the reaction tank 11 is swirled. At the same time, the filtrate passage side of the flat membrane element 15 is intermittently depressurized by intermittent driving of the suction pump 27, and the pressurized water to the flat membrane element 15 is reduced by the depressurization of the flat membrane element 15 on the filtrate side and the water level of the reaction tank 11. The liquid to be treated is subjected to membrane filtration under a transmembrane pressure difference due to pressure. The membrane filtrate is collected from the water collection ports 17a and 17b to the water collection pipes 19a and 19b, and flows into the first pipe 21 and the second pipe 25 from the water collection pipes 19a and 19b, as indicated by arrows, and the filtrate pipe 29 Is stored in the treated water tank.

As described above, according to the submerged membrane separation apparatus 10 according to the present embodiment, the membrane filtration of the liquid to be processed can be continuously performed by performing the aeration operation.
In the immersion type membrane separation apparatus 10 according to the present embodiment, as in the conventional immersion type membrane separation apparatus, dirt accumulates on the membrane of the flat membrane element 15 due to membrane filtration of the liquid to be treated, and the membrane needs to be washed. There is.

Next, a method for cleaning the submerged membrane separation apparatus 10 according to the present embodiment will be described with reference to FIG.
As shown in FIG. 2, the submerged membrane separation apparatus 10 opens the third on-off valve 35 and the fourth on-off valve 37 of the third pipe 33 when the membrane is washed. Further, the first on-off valve 23 of the first pipe 21 and the second on-off valve 31 of the filtrate pipe 29 are closed. As a result, the third pipe 33 is connected to the first pipe 21 via the junction 21a. Further, the third pipe 33 is connected to the discharge side of the suction pump 27 through the merging portion 29a. Further, the first pipe 21 is closed at the section between the joining portion 21 a with the third pipe 33 and the joining portion 21 b with the second pipe 25.

Next, a predetermined chemical solution is charged from a chemical solution inlet 39 having a check mechanism while having a funnel-shaped inlet.
As shown by the arrow, the filtrate containing the introduced chemical liquid flows into the first pipe 21 from the third pipe 33 via the junction 21a as indicated by the arrows by continuous driving (operation) of the suction pump 27, and collects in the lower part. The water flows from the water pipe 19a into each flat membrane element 15 through the water collection port 17a, and is guided to the upper water collection pipe 19b through the water collection port 17b while cleaning the membrane.

The filtrate containing the chemical solution is further sucked by the suction pump 27 from the upper water collecting pipe 19b via the second pipe 25 to the merging section 21b and from the merging section 21b via the merging section 29a to the third pipe 33. Flow into again.
As described above, according to the method for cleaning the submerged membrane separation apparatus 10 according to the present embodiment, the chemical liquid is collected through the third pipe 33 and the first pipe 21 while the chemical liquid is being injected from the chemical liquid inlet 39. After each flat membrane element 15 is supplied from the water pipe 19a and cleaned, it is sucked by the suction pump 27 from the second pipe 25 communicating with the upper water collecting pipe 19b, and the sucked chemical liquid is supplied to the chemical liquid inlet 39 of the third pipe 33. In order to return (circulate), the entire membrane surface can be filled with a small amount of chemical solution and in a short time without adding a large amount of chemical solution until the membrane of each flat membrane element 15 expands, and the entire membrane surface can be washed with a uniform concentration . In particular, in a flat membrane element that is enlarged in the height direction, it is more effective than flowing in a natural flow and spreading the chemical solution over the entire membrane surface.

Further, according to the cleaning method of the submerged membrane separation apparatus 10 according to the present embodiment, the suction amount of the suction pump 27 is the same as or about half that during filtration, and chemical cleaning is performed in a short time with a small amount. The outflow of the chemical liquid to the liquid to be treated can be suppressed.
Moreover, according to the cleaning method of the submerged membrane separation apparatus 10 according to the present embodiment, chemical cleaning can be performed while performing aeration cleaning, and more effective membrane cleaning can be performed.

Further, according to the cleaning method of the submerged membrane separation apparatus 10 according to the present embodiment, the cleaning time can be shortened, and suction is performed by the suction pump 27 from the lower water collecting pipe 19a toward the upper water collecting pipe 19b. Since the chemical liquid is introduced into the lower water collecting pipe 19a against the head of the first pipe 21 by the discharge force of the suction pump 27, the discharge pressure pushes in the suction negative pressure of the suction pump 27 and helps. Flows without delay. Further, the chemical liquid is introduced into the lower water collecting pipe 19a against the head of the first pipe 21 by the discharge force of the suction pump 27. However, since the suction force of the suction pump 27 also affects the inside of the membrane unit 13, the liquid to be treated The outflow of chemicals to the side is suppressed. If this is introduced from the upper water collecting pipe 19b to the lower water collecting pipe 19a with the suction force of the suction pump 27 and sucked from the lower water collecting pipe 19a by the suction force of the suction pump 27, the lower water collecting pipe In order to reach the pressure loss in the membrane unit 13 having a large resistance up to 19a, the discharge pressure of the suction pump must be increased, and there is a membrane that oozes out in the middle of There is no way to avoid the outflow of chemicals.
Further, according to the cleaning method of the submerged membrane separation apparatus 10 according to the present embodiment, since the membrane of each flat membrane element 15 does not swell, each flat membrane element 15 even if diffused cleaning is performed during chemical cleaning. As a result, it is difficult for the film to be twisted or the welded part to be peeled off or torn, and cleaning with higher effectiveness is possible.

FIG. 3 shows a membrane filtration operation state of the submerged membrane separation apparatus 10A according to the second embodiment of the present invention. FIG. 4 shows the membrane cleaning operation state of the submerged membrane separation apparatus 10A according to the second embodiment of the present invention.
The submerged membrane separation apparatus 10 </ b> A according to the present embodiment replaces the third pipe 33 with the third pipe 33 </ b> A provided with the relay tank 51, and the submerged membrane separation apparatus 10 according to the first embodiment of the present invention. Is different. Since the other configuration is the same as that of the submerged membrane separation apparatus 10 according to the first embodiment of the present invention, the same reference numerals are given and description thereof is omitted.
The relay tank 51 is arranged so that the chemical liquid can be introduced into the third pipe 33 </ b> A at the position of the chemical inlet 37 of the third pipe 33.

Next, the operation of the submerged membrane separation apparatus 10A according to the present embodiment will be described based on FIG.
As shown in FIG. 3, in the submerged membrane separation apparatus 10A, when the membrane filtration operation is performed, first, the third on-off valve 35 of the third pipe 33A is prevented so that the filtrate does not flow into the third pipe 33A. And the 4th on-off valve 37 is closed. Further, the first on-off valve 23 of the first pipe 21 and the second on-off valve 31 of the filtrate pipe 29 are opened.
Next, the liquid to be treated is supplied to the reaction tank 11 by the raw water supply pump. At the same time, the blower 49 is driven, and the air supplied through the air supply pipe 47 is ejected from the diffuser pipe 45 toward the membrane unit 13 as indicated by an arrow.

A swirling flow is caused in the liquid to be treated stored in the reaction tank 11 by the ejection of the air. At the same time, the filtrate passage side of the flat membrane element 15 is intermittently depressurized by intermittent driving of the suction pump 27, and the pressurized water to the flat membrane element 15 is reduced by the depressurization of the flat membrane element 15 on the filtrate side and the water level of the reaction tank 11. The liquid to be treated is subjected to membrane filtration under a transmembrane pressure difference due to pressure. The membrane filtrate is collected from the water collection ports 17a and 17b to the water collection pipes 19a and 19b, and flows into the first pipe 21 and the second pipe 25 from the water collection pipes 19a and 19b, as indicated by arrows, and the filtrate pipe 29 Is stored in the treated water tank.
As described above, according to the submerged membrane separation apparatus 10A according to the present embodiment, the liquid to be treated can be obtained by performing the membrane filtration operation, similarly to the submerged membrane separation apparatus 10 according to the first embodiment of the present invention. The membrane filtration can be performed continuously.

Next, based on FIG. 4, a cleaning method for the submerged membrane separation apparatus 10 </ b> A according to the present embodiment will be described.
As shown in FIG. 4, the submerged membrane separation apparatus 10A opens the third on-off valve 35 and the fourth on-off valve 37 of the third pipe 33A and puts a predetermined chemical into the relay tank 51 when cleaning the membrane. To do. Further, the first on-off valve 23 of the first pipe 21 and the second on-off valve 31 of the filtrate pipe 29 are closed. As a result, the third pipe 33A is connected to the first pipe 21 via the junction 21a. In addition, the third pipe 33A is connected to the discharge side of the suction pump 27 via the merging portion 29a. In addition, the first pipe 21 is closed at the section between the junction 21 a with the third pipe 33 </ b> A and the junction 21 b with the second pipe 25.

Next, the filtrate containing the chemical solution introduced into the relay tank 51 is driven by the continuous operation (operation) of the suction pump 27, as indicated by the arrow, from the third pipe 33A via the junction 21a to the first pipe 21. And flows into the flat membrane element 15 from the lower water collecting pipe 19a through the water collecting port 17a, and is guided to the upper water collecting pipe 19b through the water collecting port 17b while cleaning the membrane.
Further, the filtrate containing the chemical liquid flows again from the second pipe 25 via the junction 21b and from the discharge side of the suction pump 27 to the third pipe 33A via the junction 29a.

  As described above, according to the cleaning method of the submerged membrane separation apparatus 10A according to the present embodiment, the chemical solution is poured into the relay tank 51 through the third pipe 33A and the first pipe 21 and the lower water collecting pipe. After supplying and cleaning each flat membrane element 15 from 19a, the suction pump 27 sucks in the second pipe 25 communicating with the upper water collecting pipe 19b, and the sucked chemical solution is returned to the relay tank 51 of the third pipe 33A ( Therefore, it is possible to fill the entire membrane surface with a small amount of chemical solution and a short time without adding a large amount of chemical solution until the membrane of each flat membrane element 15 swells, and to wash the entire membrane surface with a uniform concentration. In particular, in a flat membrane element that is enlarged in the height direction, it is more effective than flowing in a natural flow and spreading the chemical solution over the entire membrane surface.

In addition, according to the cleaning method of the submerged membrane separation apparatus 10A according to the present embodiment, the suction amount of the suction pump 27 is the same as or about half that during membrane filtration, and chemical cleaning is performed in a short time with a small amount. The chemical liquid outflow to the liquid to be treated can be suppressed.
Further, according to the cleaning method of the immersion type membrane separation apparatus 10A according to the present embodiment, chemical cleaning can be performed while performing aeration cleaning, and more effective membrane cleaning can be performed.

Further, according to the cleaning method of the submerged membrane separation apparatus 10A according to the present embodiment, the cleaning time can be shortened, and suction from the lower water collecting pipe 19a to the upper water collecting pipe 19b is performed. The outflow of the chemical liquid to the liquid side is suppressed.
Further, according to the cleaning method of the submerged membrane separation apparatus 10A according to the present embodiment, the membrane of each flat membrane element 15 does not swell, so that each flat membrane element 15 even if diffused cleaning is performed during chemical cleaning. As a result, it is difficult for the film to be twisted or the welded part to be peeled off or torn, and cleaning with higher effectiveness is possible.

In addition, although each said embodiment demonstrated the case where the two water collection ports 17a and 17b were provided, this invention is not restricted to this, You may provide three or more water collection ports.
In each of the above embodiments, the case where the water collection ports 17a and 17b are provided above and below the membrane unit 13 and the water collection pipes 19a and 19b are provided above and below has been described. The water collecting ports 17a and 17b may be provided on both sides and the water collecting pipes 19a and 19b may be provided on the left and right sides.

10, 10A Submerged membrane separator 11 Reaction tank 13 Membrane unit 15 Flat membrane elements 17a, 17b Water collecting port 19a Lower water collecting pipe 19b Upper water collecting pipe 21 First piping 21a, 21b, 29a Merging section 23 First on-off valve 25 Second pipe 27 Suction pump 29 Filtrate pipe 31 Second on-off valve 33, 33A Third pipe 35 Third on-off valve 37 Fourth on-off valve 39 Chemical liquid inlet 41 Raw water supply pipe 45 Aeration pipe 51 Relay tank

Claims (5)

A flat membrane element having two or more water collection ports for taking out filtrate from the filtration membrane channel;
A reaction vessel in which the flat membrane element is immersed;
Two water collecting pipes that are respectively disposed to be opposed to the water collecting port, and
A first pipe provided with a first on-off valve and connected to one of the water collecting pipes;
A suction pump for connecting the first pipe to the suction port side;
A second pipe connected to the other water collecting pipe and connected to the first pipe between the first on-off valve and the suction port of the suction pump;
A second on-off valve, and a filtrate pipe connected to a discharge port side of the suction pump;
Provided with a chemical inlet, one end is connected to the filtrate pipe between the suction pump and the second on-off valve via a third on-off valve, and the other end is the first on-off valve and the one water collecting pipe A third pipe connected to the first pipe through the fourth on-off valve,
The flat membrane element has both ends of the flat membrane element, one end being the upper end of the immersed flat membrane element and the other end being the lower end of the immersed flat membrane element, Each having one or more upwards at the upper part of the upper end of the flat membrane element and downwards at the lower part of the lower end of the flat membrane element ,
The first on-off valve and the second on-off valve are opened during the membrane filtration operation and closed during the membrane cleaning operation,
The third on-off valve and the fourth on-off valve are closed during the membrane filtration operation and opened during the membrane cleaning operation,
The suction pump is connected to the first pipe from the lower water collecting port of the flat membrane element through the one water collecting pipe positioned horizontally and opposed to the lower water collecting port during the membrane filtration operation, and the flat membrane From the water collecting port at the upper end of the element, suction is performed so as to lead the filtrate to the second pipe through the other water collecting pipe positioned horizontally opposite to the water collecting port at the upper end. The chemical solution introduced from the chemical solution introduction unit is sucked from the third pipe to the one water collecting pipe through the first pipe, and the chemical liquid is led out from the other water collecting pipe through the flat membrane element. A submerged membrane separation device characterized by suction. The submerged membrane separation apparatus according to claim 1,
Directly below the flat membrane element, it is installed to clean the membrane surface of the flat membrane element by the upward flow of gas-liquid mixing caused by the rise of the air jetted by the drive of the blower. A submerged membrane separator characterized by having an air diffuser that sometimes ejects air. In the submerged membrane separation apparatus according to claim 1 or 2,
The submerged membrane separation apparatus, wherein the chemical solution inlet is a chemical agent inlet having a check mechanism while having a funnel-like inlet. In the submerged membrane separation apparatus according to claim 1 or 2,
The submerged membrane separation apparatus, wherein the chemical solution input unit is a relay tank having an opening-shaped chemical solution input port in a housing and storing the chemical solution introduced into the third pipe by the suction pump. In the operation method of the submerged membrane separator according to any one of claims 1 to 4,
During the membrane filtration operation, the third on-off valve and the fourth on-off valve of the third pipe are closed, the first pipe and the second pipe are communicated with the suction pump, and the first pipe is connected with the suction pump. And sucking the filtrate from the second pipe and sending it to the filtrate pipe,
During the membrane cleaning operation, the first on-off valve and the second on-off valve are closed and the third on-off valve and the fourth on-off valve of the third pipe are opened, and a predetermined amount that is introduced at the chemical solution introduction unit After the chemical solution is sucked from the third pipe through the first pipe to the one water collecting pipe by the suction pump, the one water collecting pipe passes through the flat membrane element to the other water collecting pipe. A chemical solution circulation path that sucks and leads out from the other water collecting pipe to the third pipe through the second pipe and the first pipe so that the chemical liquid flows from the bottom upward in the flat membrane element The operation method of the submerged membrane separator characterized by comprising.

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