JP2006247498A - Membrane washing method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane washing method and an apparatus which can perform a membrane surface washing using an upward flow by arbitrarily changing the stream of the upward flow while keeping a steady-state operation, thereby applying turbulent flow to the front face of the membrane without any control operation of an air diffuser, like change of aeration air volume. <P>SOLUTION: In dipped type membrane separation apparatuses 24 disposed in a treating tank 23 storing treating object liquid 22, the membrane surface is washed by the upward flow caused by bubble flow, circulation flow 29 is formed in the treating tank 23 around the apparatuses 24 by the upward flow flowing out of the apparatuses 24. The flow direction of the circulation flow 29 is periodically or irregularly changed by direction-change plates 32, 33 dipped in the treating object liquid, thereby the flow state of the upward flow in the inner passage of the dipped type membrane separation apparatuses 24 is repeatedly changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a membrane cleaning method and apparatus, and relates to a technique for improving the stability of membrane separation treatment in water treatment such as sewage, industrial wastewater, and domestic wastewater.

  Conventionally, in the membrane separation activated sludge method, for example, as shown in FIG. 13, raw water 1 to be treated is introduced into a system composed of a reaction tank 2 and a membrane separation tank 3 (also serving as a reaction tank). The mixed liquid containing activated sludge is biologically treated while circulating over the reaction tank 2 and the membrane separation tank 3, and the mixed liquid is filtered through a membrane by the submerged membrane separation device 4 immersed in the membrane separation tank 3, so that solid-liquid separation is performed. The membrane permeate is taken out as treated water 5. Further, the flocculant 6 is added to appropriate portions of the raw water 1, the reaction tank 2, and the membrane separation tank 3.

  In such a membrane separation apparatus that uses a membrane as a means for separating solid liquid, a means for controlling contamination on the surface of the membrane is required. For this reason, in the above-described configuration, aeration air is supplied from the diffuser 7 disposed at the lower part of the submerged membrane separation device 4, and the upward flow of the solid-gas / liquid mixed phase generated by the bubble flow of the aeration air is along the membrane surface. The flow of water is disturbed on the membrane surface by cross-flow, and the possibility that the pores of the membrane may be blocked due to the possibility that the colloidal substance is strongly pressed against the membrane surface by filtration is possible in terms of time probability. As much as possible, it suppresses dirt on the film surface.

  When the bubble flow is used as the upward flow generating means as in the above-described submerged membrane separation device 4, the upward flow becomes a solid-gas / liquid mixed phase flow of water, solid matter, and bubble flow. The flow is constantly changing due to turbulence, and efficient cleaning is possible. Such a bubble flow is generally used from the practical point of view, and it is not practical to use a pump as the water flow generating means because of excessive energy.

  However, when a flat membrane filtration membrane is used in the submerged membrane separation device 4, in order to prevent the accumulation of dirt on the membrane surface, the gap between the membranes is widened, a large aeration amount is given by coarse bubbles, and the rise by bubble flow When irregular turbulence is caused in the flow, the amount of aeration per unit membrane area becomes excessive. As described above, the energy required to generate a flow sufficient to suppress the contamination of the membrane surface generally requires more energy than that required for filtration when separating a material having a colloidal size or larger.

  For example, Patent Document 1 discloses a method using a bubble flow. In this method, the gel layer and cake layer adhering to the membrane surface are peeled off by bubbles ejected from the diffuser, and the membrane unit is immersed in the liquid in the treatment tank, and the diffused pores are large and coarse below the membrane unit. A bubble diffusing device and a fine bubble diffusing device with small diffusing holes are provided.

  Then, both the diffusers are operated continuously or intermittently at the same time, or only the microbubble diffuser is operated continuously, and the coarse bubble diffuser is operated intermittently, or both diffusers are operated. Both diffusers are operated such that the devices are operated intermittently, and coarse bubbles and microbubbles act on the membrane surface of the membrane unit.

Moreover, what is described in Patent Document 2 is to eject coarse bubbles through an ejection pipe by a blower different from the blower for the air diffuser, and to remove sludge adhering to the membrane surface by colliding the coarse bubbles with the membrane module. Is.
Japanese Patent No. 3341427 JP 11-314025 A

  By the way, in the submerged membrane separation apparatus using the above-described bubble flow, sufficient turbulent flow required for cleaning cannot be generated everywhere on the membrane surface unless a large amount of aeration air is supplied, and the aeration amount is not sufficient. In some cases, there is a stagnant portion of the mixed liquid at the end of the casing through which the upward flow flows, and this tendency increases as the amount of aeration decreases.

  There are a shape of the submerged membrane separation device, a shape of the water tank, a position of the submerged membrane separation device in the water tank, a constituent member that obstructs the flow, and the like to define the flow state of the upward flow. Further, when the energy spent for aeration is small, the stagnation point is always at the same position.

  This situation is shown in FIGS. FIG. 14 shows the flow of bubbles and the flow of the mixed liquid when the immersion type membrane separation apparatus is used alone. This submerged membrane separation apparatus 10 has a membrane cartridge 12 arranged in two upper and lower stages inside a casing 11, and the membrane cartridge 12 has flat membrane membranes arranged on the front and back of a filter plate, A channel having a predetermined gap is formed between adjacent membrane cartridges 12 arranged in parallel with each other.

  An upward flow is generated in the casing 11 by the bubble flow of aeration air ejected from an air diffuser (not shown), and the liquid mixture around the submerged membrane separator 10 flows into the casing 11 from the lower end opening. It flows as an upward flow of a solid-gas-liquid mixed phase together with the bubble flow, the upward flow flowing out from the upper end opening of the casing 11 flows along with the mixed liquid around the upper end opening of the casing 11, and a circulating flow is generated in the tank. When the submerged membrane separator 10 is arranged in the center of the tank, the circulation flow is formed symmetrically on both sides of the submerged membrane separator 10 and radially about the submerged membrane separator 10.

  At this time, the upward flow mainly flows near the center of the casing 11 inside the casing 11 and the flow of the upward flow is poor or stagnation occurs near the inner wall surface of the casing 11, and the cleaning effect of the film surface by the upward flow is obtained. The region 13 is weak or has no cleaning effect.

  FIG. 15 shows the flow of bubbles and mixed liquid when a plurality of submerged membrane separation devices 10 are used. In this case, since the water flow ejected from each submerged membrane separator 10 influences each other, the circulation flow formed in the tank is at the center position of the plurality of submerged membrane separators 10, that is, two left and right ones. It is formed symmetrically about the middle.

  By receiving the influence of the circulating flow in the tank, the flow of the upward flow in the casing 11 of each submerged membrane separation device 10 is not linear, and drifts to one side of the casing 11 and the other side is due to the upward flow. The region 13 has a weak cleaning effect on the film surface or no cleaning effect.

  The present invention solves the above-described problem, and without changing the aeration device control operation such as changing the amount of aerated air, appropriately changing the flow of the upflow while maintaining a steady operation state, An object of the present invention is to provide a film cleaning method and apparatus capable of performing film surface cleaning by upward flow by applying turbulent flow to the front surface.

  In order to solve the above-described problems, the membrane cleaning method of the present invention performs membrane surface cleaning by an upward flow generated along with a bubble flow in an immersion type membrane separation apparatus disposed in a processing tank storing a liquid to be processed. The circulating flow is formed in the tank around the submerged membrane separator by the upward flow flowing out from the submerged membrane separator, and the direction of the circulating flow is periodically changed by the diverting means immersed in the liquid to be treated. The flow state of the upward flow in the flow path in the submerged membrane separation apparatus is repeatedly changed by changing the direction or irregularly.

  In the above configuration, for example, when the upward flow that flows out from the upper part of the flow path of the submerged membrane separator flows out mainly on both sides of the treatment tank with the submerged membrane separator as the boundary, the liquid to be treated is mainly submerged membrane separation. After flowing as a downward flow on both sides of the apparatus, it mainly flows into the lower part of the flow path of the submerged membrane separator from both sides of the processing tank, and the circulating flow circulates in the processing tank around the submerged membrane separator. In the flow path in the submerged membrane separation apparatus, the upward flow mainly becomes a high-speed flow near the center of the flow path, and a low-speed flow or stagnation is generated at portions corresponding to both sides of the treatment tank, that is, near the flow path wall surface. For this reason, in the flow path of the submerged membrane separation apparatus, there are a region where the membrane surface cleaning is effectively applied by the high-speed flow and a region where the membrane cleaning ability is reduced by the low-speed flow or stagnation.

  In addition, when the upward flow that flows out from the upper part of the flow path of the submerged membrane separator flows out to one side of the treatment tank, the liquid to be treated flows mainly as a downward flow through one side of the submerged membrane separator. Later, it mainly flows from one side of the treatment tank to the lower part of the flow path of the submerged membrane separator, and the circulation flow circulates in the treatment tank on one side of the submerged membrane separator. In the flow path, the upward flow is a flow that changes to one side of the processing tank with respect to the flow path direction. For this reason, in the flow path of the submerged membrane separation apparatus, the flow rate is high at a location corresponding to one side of the treatment tank, and stagnation occurs at a location corresponding to the other side of the treatment tank, so that the membrane cleaning ability of the relevant portion is increased. Decrease.

  For this reason, it is immersed by changing the flow direction of the circulating flow periodically (every predetermined time) or by changing the direction irregularly (every arbitrary time) by the turning means immersed in the liquid to be treated. The flow state of the upward flow in the flow path of the mold membrane separation device, that is, the flow direction and strength is repeatedly changed to form fluctuations in the flow of the upward flow over time, and the flow in the submerged membrane separation device The entire surface of the membrane is washed by appropriately changing the place where the stagnation occurs in the road and changing the place where the upward flow flows at a high flow velocity.

  The membrane cleaning apparatus of the present invention has an immersion type membrane separation device disposed in a tank for storing a liquid to be treated, and the immersion type membrane separation device performs membrane surface cleaning by the upward flow generated along with the bubble flow, and the immersion type. In the processing tank that forms a circulating flow in the tank around the submerged membrane separation device by the upward flow flowing out from the membrane separation device, the flow direction of the circulating flow is periodically changed by the operating part immersed in the liquid to be processed. Or a turning means for turning at irregular intervals.

  Further, the diverting means has an operation part arranged opposite to the both side positions of the treatment tank through the submerged membrane separation device, and an operation position for immersing in the treatment target liquid and a non-operation position for retreating to the treatment target liquid surface. And a drive device that drives each of the direction change plates alternately between the operation position and the non-operation position periodically or irregularly.

  With the above-described configuration, by immersing one of the deflecting plates in the circulation flow, the circulation flow naturally flows in a direction easy to flow due to the resistance, and the flow of the circulation flow changes. The direction of the circulating flow is changed by immersing each turning plate alternately in the circulating flow periodically (every predetermined time) or irregularly (every arbitrary time) by the timer control. To do. As a result, the flow state of the upward flow in the flow path of the submerged membrane separation device, that is, the flow direction and strength are repeatedly changed to form fluctuations in the flow of the upward flow over time. The place where the stagnation generated in the flow path of the separation device is appropriately changed, and the whole membrane surface is washed by changing the place where the upward flow flows at a high flow rate.

  Further, the diverting means comprises an operating part that is immersed in the processing target liquid and disposed at the top of the processing tank, and a rotor for guiding the processing target liquid to one side or the other side of the processing tank according to the rotation direction, and a rotor And a drive device that reverses the rotation direction of the rotor periodically or irregularly.

  With the above-described configuration, the rotor sends out the liquid to be processed by its rotation, and induces the liquid to be processed by generating a flow velocity difference and a pressure difference on both sides of the rotor. A flow directed toward the high flow velocity and low pressure is generated in the liquid to be treated by induction by the rotor, and this flow becomes an induced flow to attract the surrounding liquid to be treated, for example, circulation from one side of the treatment tank to the other side. A flow is generated.

  The rotor can be more effective by being placed in the upward flow part of the circulating flow, that is, in the upward flow that flows out of the submerged membrane separator, and the rotor is the boundary by changing the rotation speed. The pressure difference generated on both sides can be adjusted.

  The driving device changes the direction of the circulating flow by reversing the rotation direction of the rotor periodically (every predetermined time) or irregularly (every arbitrary time) by timer control or the like. As a result, the flow state of the upward flow in the flow path of the submerged membrane separation device, that is, the flow direction and strength are repeatedly changed to form fluctuations in the flow of the upward flow over time. The entire surface of the membrane is washed by appropriately moving the place where the stagnation generated in the flow path in the separation device is moved, and changing the place where the upward flow flows at a high flow rate.

  As described above, according to the present invention, by changing the flow direction of the circulating flow, the flow of the upward flow is maintained while maintaining the steady operation state without accompanying the control operation of the air diffuser such as changing the amount of aerated air. Fluctuation can be formed in the state, and turbulent flow can be applied to the front surface of the film surface to perform film surface cleaning by upward flow.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a plurality of submerged membrane separation devices 24 are arranged in a row in a processing tank 23 into which a processing target liquid 22 flows from an inflow system 21 so as to be immersed in the stored processing target liquid 22. It is also possible to arrange only one immersion membrane separator 24.

  The submerged membrane separation device 24 has a plurality of membrane cartridges 26 arranged in two upper and lower stages inside a casing 25. The membrane cartridge 26 has flat membrane-like filtration membranes arranged on the front and back of a filter plate. A channel having a predetermined gap is formed between adjacent membrane cartridges 26 arranged in parallel along the vertical direction.

  A diffuser 28 connected to the blower 27 is disposed below each submerged membrane separator 24, and the solid-gas / liquid mixed phase rises inside the casing 25 by the bubble flow of aerated air ejected from the diffuser 28. A flow is generated, and the liquid mixture around the submerged membrane separation device 24 flows into the casing 25 from the lower end opening, and flows inside the casing 25 as an upward flow of the solid-gas liquid phase together with the bubble flow. This upward flow supplies the mixed liquid in a cross flow along the membrane surface of the membrane cartridge 26, cleans the membrane surface, flows out from the upper end opening of the casing 25, and forms a circulating flow 29 inside the treatment tank 23.

  Each membrane cartridge 26 communicates with the water conduit 30, the mixed liquid is filtered using the suction pressure by the suction pump 31 as a driving pressure to separate the solid and liquid, and the membrane permeate is taken out of the system through the water conduit 30.

  The treatment tank 23 is provided with turning means for changing the flow direction of the circulating flow 29, and this turning means will be described below. A pair of diverting plates 32 and 33 are arranged opposite to each other on both sides of the treatment tank 23 via a plurality of submerged membrane separation devices 24, and each diverting plate 32 and 33 constitutes an operating part of the diverting means. It is also possible to arrange not only a single plate but also a plurality of each.

  Each of the deflecting plates 32 and 33 is provided so as to be movable between an operation position immersed in the processing target liquid 22 and a non-operation position retracted to the liquid surface of the processing target liquid 22, and in this embodiment, shown in FIG. Thus, the vertical distance a to the submerged membrane separator 24 at the operating position is 0.2 to 0.7 m, and the horizontal distance b is 0.1 to 1.0 m.

  As shown in FIG. 3, the deflecting plates 32 and 33 are connected to hydraulic actuators 34 and 35 that constitute driving devices, respectively, and the hydraulic actuators 34 and 35 are connected to the water guide pipe 30 via electric valves 36 and 37. In communication, the discharge pressure of the suction pump 31 is the operating pressure. An electric motor can be used as the driving force for each of the deflecting plates 32 and 33, but it is advantageous in that the suction pump 31 can be effectively used.

  The water pressure actuators 34 and 35 push the respective deflecting plates 32 and 33 into the operating position against an urging means (not shown) such as a spring during operation in which the water pressure is applied, and each diverting plate 32 in a state where the water pressure is released. 33 return to the inoperative position. Each electric valve 36, 37 is connected to a control device 38. The control device 38 operates each electric valve 36, 37 periodically at a predetermined time cycle or irregularly at a random time cycle. The hydraulic actuators 34 and 35 are driven, and the deflecting plates 32 and 33 are alternately driven across the operating position and the non-operating position.

  Hereinafter, the operation of the above-described configuration will be described. The operation of this apparatus is an intermittent filtration operation that repeats, for example, a 15-minute operation of the pump and a 2-minute operation stop of the pump by timer control or the like in a state where the aeration by the aeration device 28 is always continued.

This intermittent filtration operation will be described in detail below.
1. At the time of pump operation, either one, here, the hydraulic pressure actuator 34 is applied with an operating pressure to place the deflecting plate 32 at the operating position, and in this state, the pump operation is continued for 15 minutes.
2. The pump operation is stopped for 2 minutes while the aeration of the air diffuser 28 is continued.
3. The pump operation is resumed, the operating pressure of one of the hydraulic actuators 34 is released and the direction change plate 32 is retracted to the non-operation position, and the operation pressure is applied to the other hydraulic pressure actuator 35 to bring the direction change plate 33 to the operation position. Place and continue pumping for 15 minutes in this state.
4). The pump operation is stopped for 2 minutes while the aeration of the air diffuser 28 is continued.
Repeat the above operation. The cycle time for replacing the deflecting plates 32 and 33 is set in consideration of the time until dirt adheres firmly to the film surface, but in this embodiment, it is performed every time the operation is stopped.

  In the filtration operation, in the submerged membrane separation device 24, an upward flow is generated along with the bubble flow of the aerated air diffused from the diffuser 28, and the membrane surface of the membrane cartridge 26 is washed by the upward flow, and the submerged membrane is also used. A circulating flow 29 is formed in the tank around the submerged membrane separation device 24 by the upward flow flowing out from the separation device 24.

  By the way, for example, in a state where both the deflecting plates 32 and 33 are retracted to the non-operating position, the upward flow flowing out from the upper part of the flow path formed by the casing 25 of the submerged membrane separator 24 is mainly composed of a plurality of submerged membranes. It flows out to both sides of the treatment tank with the intermediate position of the separation device 24 as a boundary. When there is one submerged membrane separator 24, the submerged membrane separator 24 is the boundary.

  Since the liquids to be treated 22 flowing out from the respective submerged membrane separators 24 influence each other, the mainstream of the treatment tank 23 is mainly flown down the outside of the submerged membrane separators 24 at both ends. Flows into the lower part of the flow path formed by the casing 25 of the submerged membrane separator 24 from both sides.

  For this reason, the circulation flow 29 is formed symmetrically around the center position of the plurality of submerged membrane separation devices 24, that is, between the left and right two units, and circulates inside the treatment tank 23. Due to the influence of the flow 29, the flow of the upward flow in the casing 25 of each submerged membrane separation device 24 is not linear, and drifts to one side of the casing 25, and the other side cleans the membrane surface by the upward flow. This is a region where the effect is weak or there is no cleaning effect.

  Further, as shown in FIG. 1, in the state where one of the deflecting plates 32 is immersed in the operating position, the deflecting plate 32 is against the upward flow flowing out from the upper part of the flow path of the casing 25 of the submerged membrane separation device 24. By becoming a resistance, the circulating flow 29 flows in a direction that easily flows.

  For this reason, the upward flow flowing out from the upper part of the flow path of the casing 25 of the submerged membrane separation device 24 is biased and flows out to one side of the processing tank 23, so that the liquid 22 to be treated is mainly submerged membrane separation at one side end. After flowing down on one side of the apparatus 24, it mainly flows from one side of the treatment tank 23 into the lower part of the flow path of the casing 25 of the submerged membrane separation apparatus 24, and the circulating flow 29 is a plurality of submerged membranes. The inside of the tank is circulated on one side of the treatment tank 23 with respect to the separation device 24, and the upward flow in the flow path of the casing 25 of each submerged membrane separation apparatus 24 is directed to one side of the treatment tank 23 with respect to the flow path direction. The flow will change. For this reason, in the flow path of the casing 25 of each submerged membrane separation device 24, a stagnation region 39 is generated at a site corresponding to the other side of the processing tank 23, and the membrane cleaning ability of this site is reduced.

  For this reason, the control device 38 operates the electric valves 36 and 37 to drive the hydraulic actuators 34 and 35 every time when the operation is stopped, that is, periodically in a predetermined time cycle, and alternately turns the deflecting plates 32 and 33. To drive between the operating position and the non-operating position. At this time, each of the deflecting plates 32 and 33 may change the angle around the axis of the hydraulic actuators 34 and 35 for each operation. It is also possible to exchange the direction change plates 32 and 33 irregularly in a random time cycle.

  When one of the deflecting plates 32 is retracted to the non-operating position and the other of the deflecting plates 33 is immersed in the operating position, the flow of the circulating flow 29 is reversed during the next filtration operation, and each nuclear immersion type membrane separation is performed. The flow state of the upward flow, that is, the flow direction and strength changes in the flow path of the casing 25 of the apparatus 24, and the upward flow changes to the other side of the processing tank 23 with respect to the flow path direction.

  For this reason, the stagnation region 39 in the flow path of the casing 25 of each submerged membrane separation device 24 is eliminated, and the high-flow-rate flow acts on this part to restore the membrane surface cleaning ability. A stagnation region 39 is newly generated on one side.

  Accordingly, by alternately immersing the deflecting plates 32 and 33 and reversing the flow direction of the circulating flow 29, the flow state of the upward flow in the flow path of the submerged membrane separation device 24, that is, the flow direction and strength is repeated. As the time passes, fluctuations are formed in the flow of the upward flow, and the place where the stagnation occurs in the flow path of the casing 25 of the submerged membrane separation device 24 is appropriately transitioned, and the upward flow has a high flow velocity. The entire film surface is cleaned by changing the flow point of the film. In the above-described operation, it takes time until the flow direction of the main circulating flow 29 in the treatment tank is reversed. However, the dirt on the film surface does not progress during the operation stop, but rather the disturbance is effective for cleaning the film surface. work.

  Therefore, it is possible to apply a strong water flow at a high flow rate efficiently on the membrane surface with less energy than in the past, and the ineffective membrane area that cannot be filtered while dirt is attached is reduced. Aeration energy per membrane area can be reduced.

  Since the shape and the inclination angle of the deflecting plates 32 and 33 affect the flow state of the upward flow and the circulating flow 29 that flow out of the submerged membrane separation device 24, and also the fluctuation of the upward flow in the casing 25. The setting is performed so that a high flow rate periodically acts on the entire membrane surface of the membrane cartridge 26 due to fluctuations in the upward flow. The fluctuation cycle of the upward flow, that is, the cycle time for replacing the deflecting plates 32 and 33 takes into account the time until the dirt adheres firmly to the film surface, and the high-speed flow before each dirt on the film surface becomes strong. Is set to act periodically on all parts of the membrane surface.

4 to 6 show other embodiments of the present invention, and the same reference numerals are given to components that perform the same operations as those of the previous embodiment, and description thereof will be omitted.
In this configuration, the diverting means includes a rotor 41 that constitutes an operating part, a motor 42 that constitutes a driving part that drives the rotor 41, and a control device 38 that controls driving of the motor 42. The control device 38 controls the rotation speed and rotation direction of the motor 42, and reverses the rotation direction of the rotor 41 regularly or irregularly.

  The rotor 41 includes a shaft portion 43 and a plurality of paddle portions 44 provided spirally on the shaft portion 43. If the rotor 41 is small, it may be attached to the submerged membrane separation device 24 or piping, and the large one may be installed in the treatment tank 23.

FIG. 4 schematically shows a state in which the rotor 41 is partially immersed in the vicinity of the liquid surface of the processing target liquid 22, but in reality, the effect is higher when the rotor 41 is submerged.
Further, the rotor 41 is provided at a plurality of locations above the treatment tank 23 corresponding to the upward flow above the submerged membrane separation device 24. In this embodiment, as shown in FIG. The vertical distance c up to 24 is 0.3 to 0.7 m, and the horizontal distance d is 0.0 to 0.5 m. The rotor 41 can also be disposed below the submerged membrane separation device 24.

  Furthermore, as shown in FIG. 12, the number of submerged membrane separators 24 increases according to the capacity of the processing tank 23, but the rotor 41 may be provided with one unit per two submerged membrane separators 24. Alternatively, the number of the rotors 41 may be reduced by increasing the size of the rotor 41.

  In the above-described configuration, the suction pump 31 and the blower 27 are driven during the filtration operation, and each rotor 41 is rotated in one direction by the motor 42. In the submerged membrane separation device 24, an upward flow is generated along with the bubble flow of aerated air diffused from the air diffuser 28, and the membrane surface of the membrane cartridge 26 is cleaned by the upward flow, and the submerged membrane separation device 24. A circulating flow 29 is formed in the tank around the submerged membrane separation device 24 by the upward flow flowing out of the submerged membrane separator 24.

  At this time, as shown in FIG. 7, each rotor 41 rotated by the motor 42 sends out the liquid 22 to be processed in the rotation direction by the rotation of the paddle portion 44, and a high speed region with a high flow velocity is set on one side of the rotor 41 as a boundary. Then, a low speed region with a low flow velocity is formed on the other side, and a flow velocity difference and a pressure difference are generated between both sides to induce the processing target liquid 22. Due to the induction by the rotor 41, a flow toward the high flow velocity and low pressure side is generated in the processing target liquid 22, and this flow becomes an induced flow to attract the surrounding processing target liquid 22, and for example, from one side of the processing tank 23 A circulating flow 29 toward the other side is generated.

  The control device 28 reverses the rotation direction of the rotor 41 by the motor 42 periodically (every predetermined time) or irregularly (every random time) by timer control or the like. In this embodiment, the rotation direction of the rotor 41 is reversed during continuous filtration operation, but it is also possible to reverse the rotation direction of the rotor 41 while the intermittent filtration operation is stopped, as in the previous embodiment. is there.

  When the rotation direction of the rotor 41 is reversed, the high speed region and the low speed region on both sides of the rotor 41 are interchanged, and the flow direction of the circulating flow 29 is reversed. Therefore, the circulating flow 29 can be controlled only by giving rotational energy to the rotor 41, and the direction of the flow can be changed with a smaller power than the aeration power.

  As a result, the flow state of the upward flow in the flow path of the casing 25 of the submerged membrane separation device 24, that is, the flow direction and strength are repeatedly changed to form fluctuations in the flow of the upward flow over time. In addition, the entire portion of the membrane surface is washed by appropriately changing the place where the stagnation occurs in the flow path of the submerged membrane separation device 24 and changing the place where the upward flow flows at a high flow rate.

  The rotor 41 can perform a more effective action by being arranged in the upward flow portion of the circulating flow 29, that is, in the upward flow flowing out of the submerged membrane separation device 24. Further, since the action of the rotor 41 has an influence on the water depth, the flow state of the circulating flow 29 is adjusted by adjusting the pressure difference generated on both sides of the rotor 41 by changing the rotation speed of the rotor 41 according to the water depth. To eliminate the occurrence of stagnation. Further, the adjustment of the rotational speed of the rotor 41 is also effective in dealing with the occurrence of stagnation due to other factors, such as the shape of the processing tank 23.

FIG. 9 shows the contamination of the membrane when the filtration operation is performed without controlling the circulating flow by the rotor 41. The amount of aerated air supplied by the air diffuser 28 per unit amount of the processing target liquid 22 is shown. It shows the daily change of the suction pressure necessary for maintaining the flux constant and continuing the filtration operation, assuming that the state of 20 m ³ is the aeration air amount 100% (20 m ³ -air / m ³ -water).

  In FIG. 9, the graph line (middle) a indicates the state of dirt (suction pressure) on the membrane surface of the submerged membrane separator 24 at the location (1) near the center of the treatment tank 23 in the configuration shown in FIG. (End) b is the state (suction pressure) of the membrane surface of the submerged membrane separator 24 in the locations (2), (3), and (4) close to the water tank wall surface of the treatment tank 23 in the configuration shown in FIG. Show.

  As clearly shown in FIG. 9, after a certain period of time, the film surface becomes dirty at both the location (1) near the center of the treatment tank 23 and the locations (2), (3), and (4) near the water tank wall. The suction pressure rises with the progress of, and is particularly noticeable at locations (2), (3), and (4) close to the water tank wall surface.

  FIG. 10 shows the contamination of the membrane when the filtration operation with the circulation flow control by the rotor 41 is performed, and is necessary for maintaining the flux constant and continuing the filtration operation with the aeration air amount being 90%. This shows the daily changes in suction pressure.

  As is clear from FIG. 10, even if the filtration operation is continued, the suction pressure at both the location (1) near the center of the treatment tank 23 and the locations (2), (3), and (4) near the water tank wall surface. Does not rise, and can maintain a state in which dirt on the film surface does not progress.

The schematic diagram which shows the film | membrane washing | cleaning apparatus in embodiment of this invention The principal part enlarged view which shows the arrangement position of the direction change board in the embodiment Schematic diagram showing the drive mechanism of the deflection plate in the same embodiment The schematic diagram which shows the film | membrane washing | cleaning apparatus in other embodiment of this invention. The top view which shows the film | membrane washing | cleaning apparatus in the embodiment The perspective view which shows the rotor in the same embodiment Schematic showing the action of the rotor in the same embodiment The principal part enlarged view which shows the arrangement position of the rotor in the embodiment The graph which shows the daily change of the filtration operation without a rotor in a comparative test The graph which shows the daily change of the filtration driving | operation with the rotor of this invention in a comparative test. Schematic diagram showing the location of contamination in a filtration operation without a rotor in a comparative test The schematic diagram which shows the film | membrane washing | cleaning apparatus in other embodiment of this invention. Schematic diagram showing the conventional membrane separation activated sludge method Schematic diagram showing the flow state in a submerged membrane separator with a conventional configuration Schematic diagram showing the flow state in the submerged membrane separation device in another conventional configuration

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Inflow system 22 Processing object liquid 23 Processing tank 24 Immersion type membrane separator 25 Casing 26 Membrane cartridge 27 Blower 28 Air diffuser 29 Circulation flow 30 Water guide pipe 31 Suction pump 32, 33 Diverting plate 34, 35 Hydraulic actuator 36, 37 Electric valve 38 Control device 39 Stuffing area 41 Rotor 42 Motor 43 Shaft part 44 Paddle part

Claims (4)

In the submerged membrane separation device disposed in the treatment tank for storing the liquid to be treated, the membrane surface is cleaned by the upward flow generated along with the bubble flow, and the submerged membrane separation device is generated by the upward flow flowing out of the submerged membrane separation device. By forming a circulating flow in the tank around the tank and periodically changing the flow direction of the circulating flow by the turning means immersed in the liquid to be treated, or by changing the flow direction irregularly, the immersion type A membrane cleaning method characterized by repeatedly changing the flow state of an upward flow in a flow path in a membrane separation apparatus. An immersion membrane separation device is placed in a tank for storing the liquid to be treated, and the immersion membrane separation device performs membrane surface cleaning by the upward flow generated along with the bubble flow, and the upward flow that flows out of the immersion membrane separation device. In the treatment tank that forms a circulation flow in the tank around the submerged membrane separation device, the flow direction of the circulation flow is changed periodically or irregularly by the operation part immersed in the liquid to be treated. A film cleaning apparatus provided with a turning means for turning. The diverting means has an operation part arranged opposite to both side positions of the treatment tank through the submerged membrane separation device, and extends over an operation position where the treatment target liquid is immersed and a non-operation position where the treatment target liquid is retracted. A plurality of direction change plates provided movably, and a drive device for driving each direction change plate alternately between an operating position and a non-operating position periodically or irregularly. 2. The membrane cleaning apparatus according to 2. The diverting means has an operating part that is immersed in the processing target liquid and arranged at the top of the processing tank, and rotates the rotor for guiding the processing target liquid to one side or the other side of the processing tank according to the rotation direction. The film cleaning apparatus according to claim 2, further comprising a driving device that drives and reverses the rotation direction of the rotor periodically or irregularly.

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