JP5473897B2 - Membrane module cleaning method and apparatus - Google Patents

Description

  The present invention relates to a membrane module used for filtration or concentration in general water treatment such as clean water and wastewater, and relates to a cleaning method and apparatus thereof.

  As a conventional membrane separation apparatus, for example, an immersion type membrane apparatus in which a plurality of membrane elements are arranged in parallel at appropriate intervals is known. The membrane element is a filter plate made of an organic membrane covering a surface of a rectangular flat filter plate as a membrane support, and the filtration membrane is joined to the filter plate at the peripheral edge. Examples of the membrane support include a resin filter plate, a nonwoven fabric, and a net.

  The membrane element receives the driving pressure and filters the water to be treated with a filtration membrane. Gravity filtration uses the head pressure in the tank as the driving pressure, or suction filtration gives negative pressure as the driving pressure inside the filtration membrane. Used for.

  By the way, when fouling occurs in the membrane element, chemical cleaning for removing the fouling is necessary. This chemical cleaning is performed by supplying the chemical to the permeate flow path between the filter plate and the filtration membrane.

  As this cleaning method, for example, there is a method described in Japanese Patent Publication (Japanese Patent Laid-Open No. 8-281082). In this cleaning method, a chemical solution is injected into the permeate flow channel of the membrane element at a low pressure, the state is maintained for an appropriate time, and then the clean solution is injected into the permeate flow channel to bring the chemical solution to the liquid to be treated. Leach and fill the permeate channel with fresh water.

  Further, there is one described in Japanese Patent Gazette (JP-A-8-290045). In this cleaning method, a chemical solution is injected into the permeate flow path of the membrane element at a low pressure, the state is maintained for an appropriate period of time, and then air is aerated from below the membrane element to peel off deposits on the membrane surface. Let

  By the way, in the conventional cleaning method described above, the chemical solution is leached from the permeate flow path of the membrane element to the liquid to be treated through the filtration membrane, and the filtration membrane and the chemical solution are in temporary contact with each other. Some of the liquid flowed out to the liquid to be treated, and the chemical use efficiency was low.

  Also, in the permeate flow path of the membrane element, the chemical solution does not spread uniformly on the inner membrane surface of the filtration membrane, but concentrates around the inlet where the chemical solution flows, so the entire filtration membrane must be thoroughly washed The cleaning efficiency of the chemical solution was low.

  In addition, when sludge accumulates between the membrane elements due to changes in the properties of the liquid to be treated or troubles in the air diffuser and sufficient filtration cannot be performed, as a method of removing the accumulated sludge, There was no effective removal method other than by manual work.

  The present invention solves the above-described problem, and continues the state in which the chemical solution continues to flow in the permeate flow path of the membrane element, and further circulates the chemical solution to repeatedly contact the filtration membrane and the chemical solution. In addition, the cleaning efficiency of the chemical solution can be increased by spreading the chemical solution uniformly throughout the filtration membrane, and by further repeating the `` swollen state '' and `` deflated state '' of the filtration membrane, It is an object of the present invention to provide a method and apparatus for cleaning a membrane module capable of peeling a fouling substance attached or deposited on the surface of a filtration membrane.

In order to solve the above-described problems, the membrane module cleaning method of the present invention is characterized in that the permeate flow path communicates with one water collection portion and the other water collection portion, and a flat membrane is formed on the main surface of the membrane support. In the membrane module comprising at least one membrane element formed by arranging a filtration membrane comprising: a cleaning chemical solution is supplied from one water collecting portion to the permeate passage of the membrane element, and the other permeate passage from the permeate passage. The cleaning chemical solution is discharged to the water collection section and the cleaning chemical solution continues to flow through the permeate flow path of the membrane element, increasing or decreasing the difference between the inflowing amount flowing into the membrane element and the outflowing amount flowing out from the membrane element. Adjust the difference between the excess flow amount of the differential liquid that causes the filtration membrane to swell away from the main surface of the membrane support, and the difference that the filtration membrane becomes deflated near the main surface of the membrane support this giving repeatedly caused the outflow exceeded state of flow rate The features.

  The membrane module cleaning method of the present invention is characterized in that the fouling substance adhering to the surface of the filtration membrane is promoted by repeating the swelled state and the deflated state of the filtration membrane.

  Further, in the membrane module cleaning method of the present invention, the fouling material deposited between the membrane elements is crushed by repeating the swollen state and the deflated state of the filter membrane, and the filter membrane surface It is characterized by promoting the peeling of the attached fouling substance.

  In the membrane module cleaning method of the present invention, the cleaning chemical solution is circulated and supplied from the other water collecting section to the one water collecting section through the circulation system.

In the membrane module cleaning apparatus of the present invention, the permeate flow path communicates with one water collection section and the other water collection section, and a filtration membrane made of a flat membrane is disposed on the main surface of the membrane support. At least one of the membrane module having a membrane element, and one of the chemical liquid supply means for supplying a wash liquor through the water collecting portion to the permeate flow path of the membrane element, permeate flow path of the membrane element through the other water collecting portion comprising The filtration membrane is separated from the main surface of the membrane support by adjusting the difference between the amount of influent flowing into the membrane element and the amount of influent flowing out of the membrane element. Flow rate adjustment means capable of repeatedly generating an excessive flow-in state of the differential liquid amount that becomes a swollen state and an excessive flow-out state of the differential flow rate in which the filtration membrane is in a deflated state close to the main surface of the membrane support It is characterized by having

  Further, in the membrane module cleaning apparatus of the present invention, the chemical solution supply means is composed of a supply line portion having a supply pump in communication with one water collecting portion, and the chemical solution discharge means is discharged in communication with the other water collection portion. Characterized in that it comprises a discharge pipe section having a pump, and the flow rate adjusting means is branched from the supply pipe section on the discharge side of the supply pump to divert cleaning chemicals and has a flow dividing pipe section having a flow rate adjusting valve. To do.

  Further, the membrane module cleaning apparatus of the present invention has a circulation system that circulates and supplies the cleaning chemical solution from the other water collection unit to the one water collection unit, and the circulation system is a chemical solution supply unit, a chemical solution discharge unit, and a flow rate adjustment unit. And a chemical solution tank, a chemical solution supply means is connected to the chemical solution tank and one water collecting part, and a supply pipe part having a supply pump is provided, and a chemical solution discharge means is connected to the other water collection part and the chemical solution tank. A shunt pipe having a flow control valve, comprising a discharge pipe section having a discharge pump, the flow rate adjusting means branching from the supply pipe section on the discharge side of the supply pump and communicating with the discharge pipe section on the suction side of the discharge pump It is characterized in that it comprises a passage part, or a flow rate adjusting means which consists of a branching line part which branches from the supply pipe part on the discharge side of the supply pump and communicates with the chemical solution tank and serves as a flow rate adjusting valve.

  As described above, the present invention repeatedly adjusts the difference liquid amount of the cleaning chemical solution in the permeate flow path of the membrane element to repeatedly generate the inflow excess state and the outflow state of the difference liquid amount, so that it adheres to the surface of the filtration membrane. The fouling material or the fouling material deposited between the membrane elements can be peeled off from the filtration membrane.

  In addition, the state in which the cleaning chemical solution flows through the permeate flow path of the membrane element can be further increased, and the cleaning chemical solution can be circulated to repeatedly contact the cleaning chemical solution and the filtration membrane, thereby increasing the usage efficiency of the cleaning chemical solution. In addition, the cleaning chemical solution can be efficiently distributed over the entire filtration membrane, thereby increasing the cleaning efficiency of the cleaning chemical solution.

The schematic diagram which shows the washing | cleaning apparatus of the membrane module in embodiment of this invention The schematic diagram which shows the washing | cleaning apparatus of the membrane module in other embodiment of this invention The schematic diagram which shows the washing | cleaning apparatus of the membrane module in other embodiment of this invention The schematic diagram which shows the washing | cleaning apparatus of the membrane module in other embodiment of this invention Sectional drawing which shows the principal part of the membrane module in this invention The perspective view which shows the membrane element of the membrane module in this invention Front view showing the membrane element Schematic diagram showing the action of the membrane module in the present invention The disassembled perspective view which shows the other structure of the membrane element in this invention The perspective view which shows the other structure of the membrane element in this invention The disassembled perspective view which shows other structure of the membrane element in this invention The front view which shows other structure of the membrane element in this invention

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a membrane module 11 constituting a membrane separation apparatus is installed by being immersed in a liquid to be treated in a treatment tank 12. A plurality of membrane modules 11 can be stacked up and down to form a membrane cassette. A diffuser (not shown) is disposed below the membrane module 11.

  In the following, although only the configuration of the cleaning device according to the present invention is illustrated, the membrane module 11 is connected to a water collection system when used, and the inside of the treatment tank 12 is diffused by a gas diffused from an air diffuser (not shown). The liquid to be processed is separated while the membrane surface is washed with the gas-liquid mixed phase flow.

  In the membrane module 11, a plurality of membrane elements 13 are arranged in parallel at predetermined intervals, and both lateral sides of each membrane element 13 are sealed in water-tight portions 14 and 15, respectively, and vertically between the membrane elements 13. Directional flow paths are formed. Each of the water collecting portions 14 and 15 has a hollow shape and has a water collecting space inside, and forms a rectangular box, but the shape thereof may be other than the rectangular shape. In the membrane element 13, the internal permeate flow path communicates with the water collection spaces of both water collection units 14 and 15.

  In the present embodiment, a configuration in which the membrane element 13 is arranged in the vertical direction is shown. However, the arrangement direction of the membrane element 13 is not limited to the vertical direction, and any arrangement is possible as long as it is arranged along the flow direction of the liquid to be processed. Therefore, as will be described later, it can be arranged in the horizontal direction or can be arranged obliquely.

  The membrane module 11 has one connecting portion 16 that communicates with the lower portion of one water collecting portion 14 and the other connecting portion 17 that communicates with the upper portion of the other water collecting portion 15, and the one connecting portion 16 and the other connecting portion. A circulation system 18 communicates with the part 17.

  The one connecting part 16 and the other connecting part 17 are not limited to the illustrated form, and can be provided at any position of the water collecting parts 14 and 15.

  In the present embodiment, only the configuration of the cleaning device according to the present invention is illustrated, but when the membrane module 11 is used, a water collecting system is connected to the one connecting portion 16 and the other connecting portion 17 for use.

  The circulation system 18 includes a chemical tank 19 for storing cleaning chemical liquid, a supply pipe section 20 that communicates with the chemical tank 19 and one of the water collection sections 14, and a discharge pipe that communicates with the other water collection section 15 and the chemical liquid tank 19. A passage part 30 and a branch pipe part 40 branched from the supply pipe part 20 and communicating with the chemical tank 19 are provided.

  The supply pipe section 20 serves as a chemical liquid supply means, and supplies the cleaning chemical liquid to the permeate flow path of the membrane element 13 through one water collecting section 14. The supply line section 20 includes a supply pump 21 for supplying a chemical solution, a throttle valve 22, a flow rate adjustment valve 23, a flow meter 24, and a pressure gauge 25, and the flow rate control unit 26 is configured by the throttle valve 22 and the flow rate adjustment valve 23. Configure.

  The discharge pipe section 30 serves as a chemical liquid discharge means, and discharges the cleaning chemical liquid from the permeate flow path of the membrane element 13 through the other water collection section 15.

  The discharge line section 30 includes a discharge pump 31 for discharging a chemical solution, a throttle valve 32, a flow rate adjustment valve 33, a flow meter 34, and a pressure gauge 35. The flow rate control unit 36 is configured by the throttle valve 32 and the flow rate adjustment valve 33. Configure.

  The diversion pipe section 40 constitutes a flow rate adjusting means, and increases or decreases the difference liquid amount between the inflowing liquid amount flowing into the membrane element 13 and the outflowing liquid amount flowing out from the membrane element 13. The diversion pipe section 40 includes a throttle valve 42 and a flow rate adjustment valve 43, and the throttle valve 42 and the flow rate adjustment valve 43 constitute a flow rate control section 46, and the upstream side discharges the supply pump 21 of the supply pipe line section 20. Branch from the side.

  As another configuration, as shown in FIG. 2, the diversion pipe section 40 is branched from the discharge side of the supply pump 21 of the supply pipe section 20 and connected to the suction side of the discharge pump 31 of the discharge pipe section 30. Is also possible.

  As another configuration, as shown in FIG. 3, it is possible to eliminate the branch pipe section 40.

  As another configuration, as shown in FIG. 4, the branch pipe section 40 is eliminated, two chemical liquid tanks 19 a and 19 b are provided, the upstream side of the supply pipe section 20 communicates with one chemical liquid tank 19 a, and the discharge pipe It is also possible to adopt a configuration in which the downstream side of the passage portion 30 communicates with the other chemical tank 19b.

As shown in FIG. 5, each of the water collecting portions 14 and 15 holds the plurality of membrane elements 13 in a watertight manner via a sealing material (resin or the like) 52 potted in the opening 51. However, the configuration is not limited to the configuration shown in FIG. 3, and there are various structures in which the membrane element 13 is joined to the water collecting portions 14 and 15 in a watertight manner. For example, the openings 51 of the water collecting portions 14 and 15 are not formed as a single opening but are formed in a plurality of slits, the membrane element 13 is inserted into each slit, and a sealing material 52 such as resin is potted in the slits. It is also possible. Alternatively, a sealing material such as rubber can be disposed around the membrane element 13.
(Example 1 of membrane element)
As shown in FIGS. 6 to 8, the membrane element 13 is a filtration membrane comprising a resin filter plate 61 that forms a membrane support, and a flat membrane (organic membrane) that is disposed so as to cover the front and back main surfaces of the filter plate 61. 62, and each membrane element 13 communicates with the water collection space of the water collection cases 14, 15 through a permeate flow path 63 formed between the front and back main surfaces of the filter plate 61 and the filtration membrane 62. . In the present embodiment, the resin filter plate 1 is exemplified as the membrane support, but a flexible material such as a nonwoven fabric or a net may be used as the membrane support.

  The upper end side of the membrane element 13 is positioned on the downstream side in the flow direction of the liquid to be processed, and the lower end side is positioned on the upstream side in the flow direction of the liquid to be processed. The filtration membrane 62 joins the upstream edge 64 and the downstream edge 65 to the end on the main surface of the filter plate 61 to form a joint 66. The filter membrane 62 can also be joined to the end surface of the filter plate 61 by bending the edge.

  In the present embodiment, the joining portion 66 is formed by applying ultrasonic vibration from above the filtration membrane 62 and welding the filter plate 61 and the filtration membrane 62 by frictional heat. However, the filter plate 61 and the filtration membrane 62 may be joined with an adhesive.

  The membrane elements 13 having this structure are arranged in parallel at a predetermined interval, and a plurality of membrane elements 13 are fixed in a watertight manner with a sealing material 52 arranged between them, and both sides of the filter plate 61 along the flow direction of the liquid to be treated. The edge of the filtration membrane 62 is held on the filter plate 61 by the sealing material 52 at the part.

However, as shown in FIG. 7, the sealing material 52 can also be formed for each individual membrane element 13, and on each side of the filter plate 61 along the flow direction of the liquid to be treated for each membrane element 13. The edge of the filtration membrane 62 is held on the filter plate 61 by the sealing material 52. Thereafter, the membrane elements 13 having this structure can be arranged in parallel at a predetermined interval, and a plurality of membrane elements 13 can be bound by a sealing material (resin or the like) 52 arranged between them. Further, as described above, a sealing material such as a rubber material may be disposed on the filtration membrane 62 and the filtration membrane 62 may be joined to the filter plate 61.
(Example 2 of membrane element)
The membrane element 13 can also be configured as shown in FIGS. In this configuration, the filtration membrane 62 forms a reversing portion 62 a that includes the downstream end portion 61 a of the filter plate 61, and the upstream edge 64 is connected to the upstream end on the main surface of the filter plate 61. Bonding portions 66 are formed by bonding to the portions. Membrane module 11 is configured in the same manner as described above by arranging membrane elements 13 having this structure in parallel at predetermined intervals.

When the membrane module 11 supplies the cleaning chemical solution to the membrane element 13 or when the filtration operation is stopped in the state where the above-described diffuser (not shown) is operated, the membrane module 11 It is possible to prevent the filtration membrane 62 from peeling or breaking on the downstream end 61a side.
(Example 3 of membrane element)
The membrane element 13 can also be configured as shown in FIGS. In this configuration, the filtration membrane 62 has a downstream inversion portion 62a that is folded back including the downstream end portion 61a of the filter plate 61, and an upstream inversion portion 62b that is folded back including the upstream end portion 61b. . And the end portions of the filtration membrane 62 overlap each other on the main surface or the end surface of the filter plate 61, the back surface at the other end portion is joined to the front surface at one end portion, and the other toward the downstream side. The joint portion 66 is formed with the end portion of the joint portion positioned outside.

  The filtration membrane 62 may be formed of a single membrane sheet in a loop shape, or may be formed in a loop shape with a plurality of membrane sheets, or may be formed of a membrane sheet that forms a seamless loop shape. It is. Membrane module 11 is configured in the same manner as described above by arranging membrane elements 13 having this structure in parallel at predetermined intervals.

  The membrane module 11 can suppress breakage even when the filtration membrane 62 is swollen when the cleaning chemical solution is supplied to the membrane element 13.

  With the above-described configuration, the supply pump 21 of the supply pipe line section 20 is driven to supply the cleaning chemical liquid from the chemical liquid tank 19 to the one water collecting section 14.

  Then, the cleaning chemical solution is supplied from one water collecting section 14 to the permeate flow path 63 of the membrane element 13, and the cleaning chemical liquid is discharged from the permeate flow path 63 to the other water collection section 15.

  The discharge pump 31 of the discharge pipe section 30 is driven to discharge the cleaning chemical liquid from the other water collecting section 15 to the chemical tank 19. As described above, the discharge conduit portion 30 can be formed in a siphon to discharge the cleaning chemical liquid to the chemical tank 19.

  Then, while the cleaning chemical liquid is circulated and supplied from the other water collecting section 15 to the one water collecting section 14 through the circulation system 18, the cleaning chemical liquid is divided into the chemical liquid tank 19 through the diversion pipe section 40.

  Then, the differential liquid amount of the cleaning chemical liquid flowing through the permeate flow path 63 of the membrane element 13 is adjusted to be increased or decreased by an operation to be described later, so that an excessive inflow state and an excessive outflow state of the differential liquid amount are repeatedly generated.

  That is, as shown in FIG. 8A, the difference amount of the cleaning chemical in the permeate flow path 63 of the membrane element 13 is in an excessive inflow state, that is, from the supply conduit 20 to the permeate flow path 63 of the membrane element 13. When the amount of the inflowing liquid flowing in is larger than the amount of the outflowing liquid flowing out from the permeate flow path 63 of the membrane element 13 to the discharge pipe section 30, the swelled state where the filtration membrane 62 is separated from the main surface of the filter plate 61; Become. As shown in FIG. 8 (b), the difference amount of the cleaning chemical flowing through the permeate flow path 63 of the membrane element 13 is in an excessive outflow state, that is, flows into the permeate flow path 63 of the membrane element 13 from the supply conduit section 20. When the amount of the effluent flowing out from the permeate flow path 63 of the membrane element 13 to the discharge conduit portion 30 is larger than the amount of the inflowing liquid that flows, the filter membrane 62 is in a deflated state close to the main surface of the filter plate 61. Become. The filtration membrane 62 is repeatedly swelled and deflated.

  The sludge 71 attached to the surface of the filtration membrane 62 or deposited between the membrane elements 13 is repeatedly swollen and deflated with the sludge 71 on the filtration membrane surface. The adhesive force of 71 is weakened, and the accumulated sludge is crushed and separated from the filtration membrane.

  That is, repeating the swelled state and the deflated state of the filtration membrane 62 not only enhances the cleaning effect in the periodic cleaning operation, but also releases sludge accumulation and blockage between the membrane elements 13. It is also effective as an operation.

That is,
(Operation example 1)
Steady State In the configuration of FIG. 1, the supply pump 21 and the discharge pump 31 are operated in a steady state, and the opening degree of the flow rate control units 26, 36, and 46 in the supply pipe part 20, the discharge pipe part 30, and the diversion pipe part 40 By adjusting, the ratio of the flow volume which flows through each flow volume control part 26,36,46 is adjusted.

  For example, a flow rate of a predetermined ratio, for example, 70%, out of the total supply amount 100% of the supply pump 21 flows into the membrane module 11 through the flow rate control unit 26 of the supply pipe line unit 20, and one water collection From the portion 14, it flows into the other water collecting portion 15 through the permeate flow path 63 of each membrane element 13. Then, the cleaning chemical liquid is returned from the other water collecting section 15 to the chemical liquid tank 19 by the discharge pump 31 through the flow rate control section 36 of the discharge pipe section 30.

  On the other hand, the flow rate of 30%, which is the remaining proportion of the total supply amount 100% of the supply pump 21, returns to the chemical solution tank 19 through the flow rate control unit 46 of the branch pipe part 40.

  In this state, there is no difference in the amount of the cleaning chemical solution in the permeate flow path 63 of the membrane element 13, that is, the amount of inflow liquid flowing from the supply pipe section 20 into the permeate flow path 63 of the membrane element 13 and the membrane element 13. The amount of the effluent flowing out from the permeate flow path 63 to the discharge conduit portion 30 becomes equal, and the cleaning chemical flows through the permeate flow path 63 without applying a load to the filtration membrane 62.

At this time, the cleaning chemical liquid flowing in from one connecting portion 16 of one water collecting portion 14 flows out from the other connecting portion 17 of the other water collecting portion 15 through the permeate flow path 63 of the membrane element 13. The cleaning chemical solution flows uniformly over the entire filtration membrane 62, the fresh cleaning chemical solution is always in contact with the filtration membrane, and the cleaning chemical solution permeates from the permeate side to the liquid to be treated, thereby increasing the cleaning efficiency.
Further, it is possible to remove the deposits inside the filtration membrane 62 and discharge it outside the system.

Further, the cleaning chemical solution circulates between the membrane element 13 and the chemical solution tank 19, the cleaning chemical solution that has passed through the membrane element 13 passes again through the permeate flow path of the membrane element 13, and the cleaning chemical solution stored in the chemical solution tank 19 is recovered. By repeatedly passing through the permeate flow path of the membrane element 13, the chance of contact between the cleaning chemical and the filtration membrane 62 is increased, and the use efficiency is increased. Furthermore, in such a state in which the load acting on the filtration membrane 62 is suppressed, the filtration membrane 62 is not broken even if aeration is performed, and the cleaning effect can be enhanced by using aeration in chemical cleaning.
Inflated state Next, the opening of the flow rate control unit 46 of the diversion pipe part 40 is reduced, and the flow rate of the cleaning chemical liquid that returns to the chemical tank 19 through the diversion pipe part 40 is suppressed. The flow rate is set to a predetermined ratio, for example, 10% of the supply amount 100%. On the other hand, the opening degree of the flow rate control unit 26 of the supply pipeline unit 20 is increased, and the amount of inflow liquid supplied to the membrane module 11 through the flow rate control unit 26 is 90% of the total supply rate 100% of the supply pump 21. Increase to%.

  In this state, the supply amount (90%) exceeds the discharge amount (70%) of the cleaning chemical solution in the membrane element 13. For this reason, as shown in FIG. 8 (a), the differential liquid amount of the cleaning chemical liquid is in an excessive inflow state, and the amount of liquid retained in the permeate flow path 63 of the membrane element 13 is increased. The swelled state is separated from the main surface of the filter plate 61.

Here, when the fouling substance, here sludge 71, is accumulated between the membrane elements 13, the filtration membrane 62 is swollen so that the accumulated sludge 71 is pressed and crushed. .
Next, the opening degree of the flow rate control unit 46 of the diversion pipe part 40 is increased, and the flow rate of the cleaning chemical liquid returning to the chemical liquid tank 19 through the diversion pipe part 40 is increased. The flow rate is set to a predetermined proportion of the supply amount 100%, for example, 50%. On the other hand, the opening amount of the flow rate control unit 26 of the supply pipeline unit 20 is reduced, and the amount of inflowing liquid supplied to the membrane module 11 through the flow rate control unit 26 is 50% of the total supply rate 100% of the supply pump 21. Reduce to%.

  In this state, the supply amount (50%) is lower than the discharge amount (70%) of the cleaning chemical solution in the membrane element 13. For this reason, as shown in FIG. 8 (b), the differential liquid amount of the cleaning chemical solution is in an excessive outflow state, and the amount of liquid retained in the permeate flow path 63 of the membrane element 13 is reduced. The filter membrane 62 is in a deflated state close to the main surface of the filter plate 61, and the filter membrane 62 is brought into close contact with the filter plate 61 in due course.

  Here, when a fouling substance, here sludge 71, is deposited between the membrane elements 13, the fouling substance pressed in the previously swollen state by the filtration membrane 62 becoming deflated. The filtration membrane 62 is separated from the surface, and the fouling substance is removed from the surface of the filtration membrane 62.

As described above, the difference amount of the cleaning chemical solution in the permeate channel 63 of the membrane element 13 is adjusted to increase / decrease, and the swollen state in the excessive flow state and the deflated state in the excessive flow state are repeatedly generated. The fouling material adhering to the surface of the filtration membrane 62 or deposited between the membrane elements 13 can be peeled off from the filtration membrane by weakening its adhesion.
(Operation example 2)
In the configuration of FIG. 2, the supply pump 21 and the discharge pump 31 are steadily operated to adjust the opening degree of the flow rate control units 26, 36, and 46 in the supply line unit 20, the discharge line unit 30, and the diversion line unit 40. Thus, the ratio of the flow rate flowing through each of the flow rate control units 26, 36, 46 is adjusted.

  In this steady state, the supply amount and the discharge amount of the cleaning chemical solution in the membrane element 13 are equal. The effects in the steady state are the same as in the first operation example.

  Next, in a state where the discharge amount of the supply pump 21 and the discharge amount of the discharge pump 31 are kept constant, the flow rate of the flow rate control unit 46 of the shunt pipe line unit 40 is increased or decreased. Due to the decrease in the flow rate flowing through the flow rate control unit 46 of the diversion channel unit 40, the amount of the cleaning chemical liquid flowing into the membrane module 11 through the flow rate control unit 26 of the supply pipeline unit 20 and the flow rate of the discharge pipeline unit 30. The amount of the cleaning chemical solution flowing out from the membrane module 11 through the control unit 36 increases.

  Since the pressure loss of the membrane element 13 is larger than that of the discharge pipe section 30, the retained liquid of the cleaning chemical liquid that stays in the permeate flow path 63 of the membrane element 13 during a short time when the amount of the cleaning chemical liquid changes. The amount increases, and as shown in FIG. 8A, the filtration membrane 62 is in a swelled state away from the main surface of the filter plate 61. However, the retained liquid amount of the cleaning chemical liquid in the permeate channel 63 gradually decreases with time, and due to the decrease in the retained liquid amount, the filtration membrane 62 becomes the main surface of the filter plate 61 as shown in FIG. It becomes a deflated state close to.

  In this state, the flow rate flowing through the flow rate control unit 46 of the diversion pipe line part 40 of the diversion pipe line part 40 is increased, and the deflated state is maintained. By repeating the above, the swollen state and the deflated state are repeated.

  In the configuration of FIGS. 1 and 2, the cleaning chemical solution is circulated between the membrane module 11 and the chemical solution tank 19 using the circulation system 18. However, it is not always necessary to circulate the cleaning chemical solution, and as shown in FIG. 4, the cleaning chemical solution supplied from one chemical solution tank 19a to the membrane module 11 may be discharged from the membrane module 11 to one chemical solution tank 19b. .

  As described above, as in the previous operation example 1, the filtration membrane is generated by repeatedly generating the swollen state and the deflated state while continuing the state in which the cleaning chemical liquid flows through the permeate flow path of the membrane element 13. The fouling material adhering to the surface of 62 or deposited between the membrane elements 13 can be peeled off from the filtration membrane by weakening its adhesion.

In the configuration of FIGS. 1 and 2, the differential flow rate in the membrane element 13 is adjusted to increase or decrease using the diversion pipe section 40. However, the diversion pipe section 40 is not necessarily required. As shown in FIGS. 3 and 4, the flow control section 26 of the supply pipe section 20 and the discharge pipe section 30 without providing the diversion pipe section 40, It is also possible to increase / decrease the differential flow rate in the membrane element 13 by adjusting the opening degree of at least one of the 36. It is also possible to increase or decrease the differential flow rate in the membrane element 13 by adjusting the output of at least one of the supply pump 21 or the discharge pump 31 of the supply pipe section 20 and the discharge pipe section 30 by inverter control or the like. It is.
Example 1
-Implementation method The membrane module 11 is immersed in activated sludge, and only the filtration operation is performed without aeration, and the sludge is adhered to the membrane surface. The transmembrane pressure difference at the time of disclosure of the filtration operation is measured before and after the chemical cleaning, and the effect of the repeated action of the swelled state and the deflated state of the filtration membrane is determined.
・ Membrane surface adhering sludge This is the sludge when the transmembrane differential pressure reaches about 30 kPa by performing only the filtration operation without aeration. The same sludge state is assumed in each test section.
・ Membrane module Membrane element: 500 × 500 × 6mm
Number of membrane elements: 10 Water collecting part: Provided on both sides of the membrane element.
Forming method of swelling and deflation of the membrane surface In the operation example 1 performed in FIG. 1, that is, in a state where the flow rates of the discharge pump 31 and the supply pump 21 are kept constant, the flow rate of the diversion pipe section 40 is adjusted to increase or decrease Thus, the differential liquid amount in the membrane element 13 is set to the inflow excess state or the outflow excess state.
・ Chemical liquid Chemical liquid: Sodium hypochlorite 0.5%
Chemical injection amount: Increase / decrease the flow rate to 2.5 (L / min) and 1.5 (L / min) in 1 minute cycle.

Chemical drainage: 2.0 (L / min)
Chemical cleaning time: 30 minutes / test category Wash with chemicals without causing swelling or deflation of the membrane surface. That is, the chemical solution injection amount and the chemical solution drainage amount are made equal to 2.0 L / min.

2. Wash with chemicals while causing swelling and deflation of the membrane surface.
-Results When the transmembrane pressure difference was measured after the chemical solution cleaning, the transmembrane differential pressure recovered only to 9.6 (kPa) in the chemical solution cleaning without expansion and contraction of the membrane surface in Test Category 1. In the chemical cleaning that performs expansion and contraction of the membrane surface in Test Category 2, the transmembrane pressure difference recovered to 5.0 (kPa).

From this result, when performing chemical cleaning, the sludge adhering to the membrane surface is peeled off by causing the membrane surface to swell and deflate when the differential liquid amount in the membrane element 13 is set to an excessive inflow state or an excessive outflow state. It becomes easy, membrane permeability can be improved, and it turns out that a cleaning effect increases.
(Example 2)
The items in the previous Example 1, that is, the membrane surface adhering sludge, the membrane module, the chemical solution, and the test category are the same conditions, and the membrane surface expansion / contraction method is the operation example 2 performed in FIG. That is, in a state where the discharge amount of the supply pump 21 and the discharge amount of the discharge pump 31 are kept constant, the flow rate of the flow rate control unit 46 of the diversion conduit unit 40 is adjusted to increase or decrease, and the chemical solution injection amount is 2.5 L in one minute cycle. Increase or decrease the flow rate to 1 / min and 1.5 L / min.
・ Results When the transmembrane pressure difference is measured after the chemical solution cleaning, the transmembrane differential pressure recovers only to 9.6 (kPa) in the chemical solution cleaning without swelling or deflation of the membrane surface in Test Category 1. In the chemical solution cleaning in which the membrane surface of Test Category 2 swells and wilts, the transmembrane pressure difference recovered to 6.8 (kPa).

  From this result, when performing chemical cleaning, the sludge adhering to the membrane surface is peeled off by causing the membrane surface to swell and deflate when the differential liquid amount in the membrane element 13 is set to an excessive inflow state or an excessive outflow state. It becomes easy, membrane permeability can be improved, and it turns out that a cleaning effect increases.

Claims (7)

A membrane comprising at least one membrane element in which a permeate flow channel communicates with one water collection portion and the other water collection portion, and a filtration membrane made of a flat membrane is disposed on the main surface of the membrane support. In the module, the cleaning chemical solution is supplied from one water collecting portion to the permeate flow passage of the membrane element, and the cleaning chemical solution is discharged from the permeate flow passage to the other water collecting portion so that the cleaning chemical solution is permeated through the membrane element. Continue to flow through the flow path and adjust the difference between the amount of inflow flowing into the membrane element and the amount of effluent flowing out of the membrane element to increase or decrease, and the filtration membrane swells away from the main surface of the membrane support The membrane module cleaning is characterized in that it repeatedly causes an inflow excess state of the differential liquid amount to be in a stagnation state and an excess outflow state of the differential flow rate in which the filtration membrane is in a state of being deflated close to the main surface of the membrane support. Method. The method for cleaning a membrane module according to claim 1, wherein peeling of the fouling substance adhering to the surface of the filtration membrane is promoted by repeating the swollen state and the deflated state of the filtration membrane. By repeating the swollen state and the deflated state of the filtration membrane, the fouling material deposited between the membrane elements can be crushed to promote the separation of the fouling material adhering to the surface of the filtration membrane. The method for cleaning a membrane module according to claim 1 . The cleaning method for a membrane module according to any one of claims 1 to 3 , wherein the cleaning chemical solution is circulated and supplied from the other water collecting part to the one water collecting part through the circulation system. A membrane comprising at least one membrane element in which a permeate flow channel communicates with one water collection portion and the other water collection portion, and a filtration membrane made of a flat membrane is disposed on the main surface of the membrane support. A chemical supply means for supplying a cleaning chemical solution to the permeate flow path of the membrane element through one water collection part; and a chemical solution discharge means for discharging the cleaning chemical liquid from the permeate flow path of the membrane element through the other water collection part. The amount of differential liquid between the amount of inflow flowing into the membrane element and the amount of effluent flowing out of the membrane element is adjusted to increase or decrease, so that the filtration membrane is in a state where it swells away from the main surface of the membrane support. A membrane module comprising a flow rate adjusting means capable of repeatedly causing an excess inflow state and an outflow excess state of a differential flow rate in which the filtration membrane is in a state of being deflated near the main surface of the membrane support . Cleaning device. The chemical solution supply means is connected to one water collecting section and is composed of a supply pipe section having a supply pump, and the chemical liquid discharge means is connected to the other water collection section and is composed of a discharge conduit section having a discharge pump, and the flow rate is adjusted. 6. The membrane module cleaning apparatus according to claim 5 , wherein the means comprises a branch pipe section that branches off from the supply pipe section on the discharge side of the supply pump and splits the cleaning chemical solution and has a flow rate adjusting valve. . It has a circulation system that circulates and supplies cleaning chemical liquid from the other water collection section to one water collection section, the circulation system has chemical liquid supply means, chemical liquid discharge means, flow rate adjustment means, and chemical liquid tank, and the chemical liquid supply means is chemical liquid The tank is connected to one water collecting section and has a supply pipe section having a supply pump, and the chemical liquid discharging means is connected to the other water collecting section and the chemical liquid tank and has a discharge pipe section having a discharge pump. The adjusting means branches from the supply pipe section on the discharge side of the supply pump and communicates with the discharge pipe section on the suction side of the discharge pump, and consists of a shunt pipe section having a flow rate adjusting valve, or supplied by the flow control means 6. The membrane module cleaning apparatus according to claim 5 , comprising a branch pipe section having a flow rate adjusting valve which branches from a supply pipe section on the discharge side of the pump and communicates with a chemical tank.

Images