JP5605802B2 - Flat membrane filtration device and flat membrane filtration method - Google Patents

Description

  The present invention is a flat membrane filtration apparatus for immersing a membrane unit in a treatment tank filled with water to be treated such as sewage or industrial wastewater, generating an upward flow in the tank, separating the liquid into solid, and taking out filtrated water. And a flat membrane filtration method.

  There is a flat membrane filtration device that removes impurities contained in sewage and industrial wastewater. The flat membrane filtration device is arranged in a state where a plurality of membrane elements are immersed in a treatment tank filled with the water to be treated, and sucks and filters the water to be treated from the inside of the membrane module as an assembly of the membrane elements. Thus, filtered water is obtained. Each membrane element is vertically installed in the processing tank with a predetermined interval, and is provided with a diffuser for performing aeration below.

The purpose of aeration is to obtain a cleaning effect that removes solids such as dust that accumulates on the membrane surface during filtration and suction to suppress the clogging of the membrane. Further, a swirling flow is caused in the water to be treated in the treatment tank to give a water flow near the membrane surface, and the inside of the treatment tank is stirred.
Thereby, the filtration process by a membrane module can be performed efficiently. Patent document 1 can be mentioned as an example of such a flat membrane filtration apparatus.

JP 2007-136389 A

  FIG. 9 is an explanatory view of the upward flow of a single membrane module. As shown in the figure, a diffuser tube 204 disposed below the membrane module 202 with respect to the membrane module 202 in which a plurality of membrane elements 200 are arranged in parallel at predetermined intervals and the side surfaces are covered with a casing (not shown). The bubbles ejected from the air concentrate at the center as the arrow A rises. This is because the flow velocity decreases near the casing wall due to wall friction. Therefore, in the side part 206 of the membrane module 202, it is difficult for the crossflow flow that occurs as the bubbles rise, and the membrane surface cleaning effect is reduced by the crossflow flow, and the membrane surface is partially blocked. Occlusion of the membrane surface may reduce the effective membrane area and thus cause an early increase in filtration pressure.

  FIG. 10 is an explanatory view of the upward flow of the membrane module arranged in the vertical direction in the treatment water treatment tank. As shown in the figure, immediately after the diffuser tube 204, the bubbles 205 are ejected all at once, and the liquid phase outside the casing 207 is also sucked in (arrow a). At this time, the gas-liquid two-phase flow consisting of water to be treated and bubbles forms a relatively uniform distribution. However, in the vicinity of the wall of the casing 207, the flow velocity decreases due to the above-mentioned wall friction, so that the flow velocity distribution develops upward. In the upper part of the membrane module 202, a parabolic flow velocity distribution as shown by an arrow b is formed by the crossflow flow. In this case, a place where the flow velocity is fast is concentrated in the central portion (arrow c) in the horizontal width direction, and the flow velocity is slow in a place near the both ends (arrow d).

  Therefore, the film surface is likely to be clogged in a region other than the central portion. In order to eliminate such a place where clogging is likely to occur, it is necessary to increase the amount of aeration. However, while there are places that are not clogged, such as the central part of the membrane element, it is not efficient to increase the amount of diffused air for cleaning and regenerating partially clogged membrane surface regions. . In addition, it is impossible to intensively diffuse only in places where dirt or clogging has progressed. Even if the amount of air diffused is increased only at the location where clogging has progressed, the tendency of side friction near the wall does not change, so only a flow velocity difference occurs between the center and the side, and a parabola. There is a risk that clogging may be facilitated because a flow velocity distribution in the form of particles is easily formed.

  Therefore, in the conventional filtration device, when such a part occurs, the entire membrane surface including the part with little dirt is cleaned by increasing the amount of air diffused at the same time. There was a problem.

On the other hand, there is a method of attaching a rectifying plate as another means for eliminating the central deviation of the flow velocity distribution in the horizontal width direction in the intermembrane flow path. However, the distance between the membrane elements, that is, the width of the flow path between the membranes is usually several mm to several tens mm, and it is difficult to provide the current plate in such a narrow place. Further, when the membrane modules are stacked in multiple stages, it is necessary to arrange the rectifying plates in other stages in the vertical direction for each membrane module, which is not practical.
Accordingly, an object of the present invention is to provide a flat membrane filtration device and a flat membrane filtration method capable of effectively obtaining a membrane surface cleaning effect in order to solve the above-described problems of the prior art.

The flat membrane filtration device of the present invention immerses a membrane module in which side surfaces of a plurality of flat membranes arranged in parallel in a treatment tank of the water to be treated are surrounded by a casing, and the water to be treated is interposed between the membranes of the plurality of flat membranes. In a flat membrane filtration device that separates solid and liquid while generating an upward flow, the inside of the treatment tank is flowable by the upward flow, and a carrier having a density higher than that of water is added to the treatment tank. The ratio of the specific flow velocity difference (F (de / W)), which is the speed difference between the mixed phase fluid and the flow path width W between the equivalent diameter de of the carrier and the flat membrane,
The carrier is characterized in that the ratio of the length of one side to the channel width between the flat membranes is 0.5 or more and 0.9 or less .

The flat membrane filtration device of the present invention diffuses the treatment tank of water to be treated, a membrane module in which side surfaces of a plurality of flat membranes arranged in parallel in the treatment tank are surrounded by a casing, and a flow path between the flat membranes. An aeration means for generating an upward flow of the water to be treated; a carrier capable of flowing in the treatment tank by the upward flow; and a carrier having a density higher than that of water . The ratio of the specific flow rate difference (F (de / W)), which is the speed difference, and the ratio of the equivalent diameter de of the carrier and the channel width W between the flat membranes is expressed by the following equation:
The carrier is characterized in that the ratio of the length of one side to the channel width between the flat membranes is 0.5 or more and 0.9 or less .
In this case, the carrier is preferably a polyhedron.

The carrier may have a ratio of the length of one side to the channel width between the flat membranes of 0.5 or more and 0.9 or less.
The membrane modules are preferably stacked in multiple stages in the vertical direction in the processing tank.

In the flat membrane filtration method of the present invention, the water to be treated is immersed between the membranes of the plurality of flat membranes by immersing the membrane module in which the side surfaces of the plurality of flat membranes arranged in parallel in the treatment tank of the water to be treated are surrounded by the casing. In the flat membrane filtration method in which solid-liquid separation is performed while generating an upward flow, a carrier having a speed difference due to the upward flow with respect to the water to be treated is added to the treatment tank, and a specific flow rate difference (F (de / W)) and the ratio of the equivalent diameter de of the carrier and the flow path width W between the flat membranes are expressed by the following equation:
The carrier has a ratio of the length of one side to the channel width between the flat membranes of 0.5 or more and 0.9 or less, and the water to be treated is solid-liquid while dispersing the carrier in the channel between the membranes. It is characterized by separation.

  According to the flat membrane filtration device and the flat membrane filtration method of the present invention having the above-described configuration, since a carrier having a speed difference due to the upward flow with respect to the water to be treated is used, It becomes difficult to move following the upward flow due to the drag from the gas-liquid two-phase fluid.

  Specifically, the carrier can flow in the treatment tank in an upward flow, and since it has a higher density than water, it is more susceptible to drag from the gas-liquid two-phase fluid and moves in a flow slower than the upward flow. . Further, since the carrier is a polyhedron, the carrier is easily subjected to a drag from the gas-liquid two-phase fluid, and moves in a flow slower than the upward flow.

  For this reason, in the horizontal width direction of the intermembrane flow path, the carrier existing around the casing is difficult to move to the central portion, and is present in a substantially uniform state in a dispersed state. Therefore, it is possible to move upward while being dispersed in the lateral width direction while moving from the inlet portion to the upper outlet portion where there is a diffuser for the intermembrane flow path.

  As described above, the carrier of the present invention functions as a rectifier that moves while dispersing the intermembrane flow path, thereby flattening a gas-liquid two-phase flow velocity distribution in which a portion having a high flow velocity is generated at the center of the flow channel. . Therefore, a shearing force based on the speed difference is generated on the film surface, and the entire film surface can be cleaned evenly, and it is not necessary to increase the amount of air diffusion as in the conventional case to prevent clogging. The amount of air diffused can improve the cleaning effect.

  In addition, the turbulence generated around the bubbles induces a shearing force and contributes to the membrane surface cleaning, and the density is higher than that of water, and turbulence due to fluid vortices and separation occurs around the polyhedral carrier. As a result, shearing force induced by these disturbances is also generated. Therefore, the location where shearing force is generated is increased as compared with the state of the conventional gas-liquid two-phase flow, and the effect of cleaning the membrane surface can be enhanced as compared with the conventional flat membrane type filtration device.

  Further, even in the configuration in which the membrane modules are stacked and arranged in multiple stages in the treatment tank, the carrier that is substantially uniform in the horizontal width direction of the intermembrane flow path in the lower membrane module is maintained in the upper stage while being maintained as it is. Sequentially supplied to the membrane module. For this reason, the difference in flow velocity distribution that has been noticeably generated in the upper membrane module is eliminated, and the membrane surface of the entire range of the membrane module can be evenly cleaned.

It is a structure schematic diagram of the flat membrane filtration apparatus of the present invention. It is explanatory drawing of the parameter of the flow direction width | variety between membranes, and the length of the horizontal direction of a membrane element. It is explanatory drawing of the support | carrier which raises and moves in a multiphase fluid. It is a graph which shows the relationship between a specific flow velocity difference and a size ratio. It is explanatory drawing of the upward flow of an intermembrane flow path. It is the figure which showed typically the whole processing system of the flat membrane filtration apparatus of this invention. It is explanatory drawing of the modification of the flat membrane filtration apparatus of this invention. It is explanatory drawing of the upward flow of the flat membrane filtration apparatus of a modification. It is explanatory drawing of the upward flow of a single membrane module. It is explanatory drawing of the upward flow which laminated | stacked the membrane module in multiple stages.

Embodiments of a flat membrane filtration device and a flat membrane filtration method of the present invention will be described below in detail with reference to the accompanying drawings.
First, the whole structure of the processing system which can apply the flat membrane filtration apparatus of this invention is demonstrated. FIG. 6 is a diagram schematically showing the entire processing system of the flat membrane filtration device of the present invention. As shown in the figure, the waste water treatment system 50 includes a raw water pipe 52 for drawing sewage and industrial waste water, a raw water pump 54 for drawing waste water, a pretreatment tank 56, and a treatment tank 12 in which a flat membrane filtration device is mounted. The filtration pump 58 for taking out filtrate water has a main basic configuration.

  The pretreatment tank 56 is provided with a strainer device for removing large solids and dust contained in the raw water. Moreover, when the biological treatment of raw | natural water is required, it is good also as a structure which applies a biological reaction processing tank. Thereby, the burden of solid-liquid separation by the latter flat membrane filtration apparatus can be reduced. The raw water from which large solids and the like have been removed in such a pretreatment tank 56 is introduced into the treatment tank 12 in which the subsequent flat membrane filtration device is mounted.

  FIG. 1 is a schematic configuration diagram of a flat membrane filtration device of the present invention. As shown in the figure, the flat membrane filtration apparatus 10 of the present invention has a main basic configuration including a treatment tank 12 filled with water to be treated such as sewage and industrial waste water, a membrane unit 20 and a carrier 40.

  The membrane unit 20 includes a membrane module 24 and an air diffuser 30. The membrane module 24 includes a plurality of membrane elements 22 that are flat membranes. The membrane element 22 is a flat filtration membrane. The plurality of membrane elements 22 are arranged in parallel at predetermined intervals so that the membrane surfaces are parallel to each other, and form a membrane module 24 whose side surface is surrounded by a casing 26. The membrane module 24 has a flow path through which water to be treated passes in the vertical direction between the membranes of the membrane element 22 with the upper and lower surfaces opened. The membrane unit 20 is formed on the membrane module 24 by combining an air diffuser 30, a filtration pump 58, and a pipe 28 described later. The membrane module 24 is connected to a filtration pump 58 via a pipe 28. By driving the filtration pump 58, the filtered water (treated water) filtered from the membrane surface of the membrane element 22 passes through the pipe 28 and is discharged to the outside.

  The air diffuser 30 generates bubbles in the treatment tank 12. The air diffuser 30 is attached below the membrane module 24 in the area surrounded by the casing 26 in plan view, and bubbles stay and float in the intermembrane flow path of the membrane module 24. Thereby, the density difference between the inside of the inter-membrane flow path that is in the gas-liquid mixed phase state of the water to be treated and the bubble and the outside of the membrane module 24 in the treatment tank that is in the single phase state of the water to be treated Occurs. In such an intermembrane flow path, an upward flow that is an upward flow is generated. As an example, the air diffuser 30 can employ a configuration in which a plurality of air diffusers are arranged in parallel along the membrane elements 22 arranged in parallel. Further, the air diffuser 30 is configured to provide an air diffuser at a lower portion of the air diffuser and to connect an air diffuser pump (not shown) to arbitrarily adjust the amount of air diffused.

The support | carrier 40 is added to the to-be-processed water in the processing tank 12, and has the speed difference by an upward flow with respect to to-be-processed water.
Specifically, the carrier of the present embodiment is set so as to be able to flow in the treatment tank in an upward flow and to have a density higher than that of water. When the density of the carrier is higher than that of water, the carrier moves in a slower flow than the water to be treated in the water to be treated that moves through the intermembrane flow path. Therefore, the carrier introduced uniformly in the width direction of the intermembrane flow path becomes a center of the water to be treated when the water to be treated moves to the central part by the upward flow. It acts to suppress the movement of the part. For this reason, the carrier moves in a state in which uniform dispersion is maintained when the intermembrane flow path is introduced. Therefore, the gas-liquid two-phase flow velocity distribution can be flattened and the membrane surface of the membrane element can be evenly cleaned.

  In addition, as a material of the support | carrier of this embodiment, it is desirable that it is a material which does not damage the membrane surface of a membrane element. As an example of such a carrier, a polymer gel material having a high water content, a rubber resin, or the like can be used. In addition, a porous material such as urethane foam that is a material having a high porosity that absorbs water in the water to be treated and has a density close to that of water and increases in density can also be applied.

  The carrier of this embodiment is formed to be a polyhedron. The carrier is formed in a cube as an example. A cubic carrier can be easily processed. Such a cubic carrier has a resistance coefficient approximately twice that of a spherical shape. The carrier formed in the polyhedron moves in the water to be treated moving in the intermembrane flow path, and the flow of the water to be treated is easily hindered by the corners, and moves in a slower flow than the water to be treated. Therefore, the carrier introduced uniformly in the width direction of the inter-membrane flow path moves the water to be treated when the water to be treated moves to the center part by the upward flow, and the shape of the polyhedron acts as a drag. The action which suppresses. For this reason, the carrier moves in a state in which uniform dispersion is maintained when the intermembrane flow path is introduced. Therefore, the gas-liquid two-phase flow velocity distribution can be flattened and the membrane surface of the membrane element can be evenly cleaned.

Regarding the density of the carrier, it is basically higher than that of water, and practically, it is preferably lower than 2.5 g / cm ³ . In practical terms, the average flow velocity of the intermembrane flow path is about 0.1 m / s to 0.4 m / s. If the density of a 3 mm square carrier exceeds 2.5 g / cm ³ , it is expected that the terminal sedimentation rate will be 0.2 m / s or more and the flow state will be deteriorated. In the region where the flow rate is low, the intermembrane flow path does not move up and stays in the stagnation part such as the bottom in the membrane separation tank, making it difficult to obtain the effects of the present invention. Therefore, the density of the carrier is desirably higher than 1 g / cm ³ and not higher than 2.5 g / cm ³ .

In addition, the support | carrier 40 can also be set as the structure introduce | transduced into the processing tank 12 by adding to the to-be-processed water previously besides adding to the to-be-processed water in the processing tank 12. FIG.
Further, the carrier of the present invention is set so as to maintain a volume filling rate of several tens of percent of the water to be treated in the treatment tank. In the operation of the flat membrane separator, the concentration of raw water solids in the treatment tank increases due to the removal of the filtered water. Therefore, the concentration of the raw water solids can be adjusted by regularly extracting the solid sludge. The carrier in the treatment tank is also drawn out by this drawing process. In order to maintain the above-mentioned volume filling rate, a predetermined amount of carrier is added simultaneously with the extraction of the solid sludge.

  Next, the conditions of the shape of the carrier 40 will be described in more detail with reference to FIGS. FIG. 2 is an explanatory diagram of parameters of the intermembrane flow path width and the horizontal length of the membrane element. FIG. 3 is an explanatory diagram of the carrier that moves up and down in the multiphase fluid.

  As shown in FIG. 2, the horizontal length of the membrane elements 22 is L, and the distance (flow channel width) between the membrane elements 22 is W. In the general flat membrane filtration device, the flow path width W is sufficiently small with respect to the width length L, and is set in the range of several mm to several tens mm as an example.

  Next, as shown in FIG. 3, with respect to a rectangular parallelepiped having a flow path width W × W in the horizontal cross-sectional direction, there is only one carrier in the horizontal direction and a plurality of carriers are distributed in the vertical direction. Is assumed to exist.

  Then, assuming that such a W × W channel is connected in the horizontal direction having the width L, an intermembrane channel is formed, and the material balance and momentum balance of the carrier will be examined below.

First, the diameter of the carrier is d, and the equivalent diameter de using the same volume sphere diameter can be expressed by Equation 1.

Here, it is assumed that the carrier is adjusted so as to have a constant amount (a constant addition rate) in the range of the flow path width W × W in the horizontal sectional direction as described above. Also, it is assumed that the liquid flows at a constant flow rate in the flow path. Further, it is assumed that bubbles generated from the air diffuser are also diffused at a constant flow rate.
Then, since there is no suction or springing out of these carriers, liquids, and gases in the flow path, it can be considered that the substance amount is preserved.

Therefore, for a two-phase fluid phase of liquid and gas, assuming that the flow rate of this mixed phase fluid (referred to as a fluid mixture of a liquid phase and a gas phase) is u _F and the velocity of the carrier is u _P , the void ratio of the carrier (cut off) Using the area ratio) α _P , the relational expression of the mass balance can be expressed by Equation 2.
Note that J is a volume flux (equivalent velocity) of the entire carrier and the mixed phase fluid, and is given at a constant flow rate as described above, and thus takes a constant value.

Next, consider the balance of momentum, that is, the balance between the gravity of the carrier and the drag received from the fluid. The volume of the carrier is Vol, the cross-sectional area is A (the area given by the equivalent diameter de, which is the circular area of this diameter), the density of the multiphase flow is ρ _L , the density difference between the carrier and the multiphase fluid is Δρ, When the drag coefficient of the carrier is given by C _D , the balance equation can be expressed as Equation 3.

  Note that the gravitational acceleration g is originally a vector and the velocity is also a vector, but in the present embodiment, only a one-dimensional ascending motion is handled, so these physical quantities are represented only by vertical components.

  Further, the term relating to the square of the velocity on the right side of Equation 3 is expressed as a positive value because the density of the carrier is higher than the multiphase flow density, and the gravitational acceleration g is also handled as an absolute value (positive value). .

Then, by simultaneous equations 2 and Equation 3 By modifying Equation velocity u _P of the carrier it can be expressed as Equation 4.

Here, the drag coefficient C _D carrier is a function of Re number (Reynolds number), density difference of the multiphase fluid and the carrier is small.
Therefore, since the flow rate difference is small, the Re number is not large, and can be expressed by an equation that is inversely proportional to the Re number. This is because a laminar flow can be assumed.

Re number in Equation 5, the drag coefficient C _D can be expressed by Equation 6.
Note that ν represents the kinematic viscosity of the multiphase fluid, and the coefficient K is given as a value of about 45.

Next, when Expression 1, Expression 2, Expression 4, Expression 5, and Expression 6 are used, they can be expressed as Expression 7.

Here, the void ratio (cross-sectional area ratio) α _P of the carrier can be expressed as Equation 8 from its definition.

Therefore, Expression 7 can be expressed as Expression 9 using Expression 8.
The obtained Formula 9 shows the difference in velocity between the carrier and the mixed phase fluid. The greater the speed difference, the higher the drag force acting on the carrier, and the higher the shearing force induced from vortices and separation as described above.

  Further, as described above, since the carrier becomes difficult to move along with the mixed phase fluid, the mixed phase fluid makes a movement that resists the tendency of the flow velocity to concentrate in the center in the horizontal width direction of the intermembrane flow path. For this reason, the support | carrier of this embodiment disperse | distributes to the said width direction, it acts as a rectifier of a mixed phase fluid, and can raise the above-mentioned effect.

Therefore, in Equation 9, it can be considered that the difference in flow velocity is maximized if the following equation (Equation 10) on the right side of Equation 9 is minimized.

  Equation 10 corresponds to the specific speed difference. This size ratio (the ratio between the equivalent diameter de of the carrier and the channel width W) can be graphed as shown in FIG. FIG. 4 is a graph showing the relationship between the specific flow velocity difference and the size ratio. The vertical axis in the figure represents the specific flow velocity difference, and the horizontal axis represents the size ratio (ratio of the length of one side of the carrier to the channel width).

Here, this specific flow velocity difference is maximized at the next size ratio by differentiating Equation 10.

  As shown in FIG. 4, the relationship between the specific flow velocity difference and the size ratio (carrier / channel width) is expressed as a downwardly convex parabola, and when the size ratio is about 0.71, the ratio is The flow velocity difference is the largest. While the drag that the carrier receives from the fluid is maximized, the work that the carrier brings to the fluid is maximized due to the law of action and reaction, and the effect of the fluid turbulence near the carrier is also maximized. Therefore, the induction of vortices and turbulence is maximized, and the shear force of the fluid necessary for cleaning the membrane surface can be maximized.

  Next, the size ratio that gives the appropriate size of the carrier to the width of the intermembrane flow path will be examined. When the diameter size of the carrier is smaller than half the width of the intermembrane channel, two or more carriers can pass between the membranes simultaneously. At this time, depending on the orientation of the polyhedral carrier, there is a possibility that at least two carriers cross-link and remain blocked in the intermembrane flow path. Therefore, the lower limit value of the carrier size ratio is desirably 0.5 or more. The specific flow rate difference when the size ratio is 0.5 is -0.19. As shown in FIG. 4, the relationship between the specific flow velocity difference and the size ratio is expressed in a downwardly convex parabola with the size ratio of 0.71 as the lowest point, and the size ratio ranges from 0.5 to 0.71. Then, the specific flow velocity difference becomes large. On the other hand, when the size ratio exceeds 0.71 and further exceeds 0.9, the absolute value becomes smaller than the specific flow velocity difference (−0.19) when the size ratio is 0.5, and the flow velocity difference is reduced. It becomes difficult to obtain the effect of turbulence. Therefore, the upper limit value of the size ratio is desirably 0.9 or less.

From the above, the range of the size ratio can be expressed as Equation 12.
Regarding the diameter d of the carrier, the range of Expression 13 is considered to be effective based on Expression 1.

Next, a flat membrane filtration method using the flat membrane filtration device having the above configuration will be described below.
Water to be treated such as sewage and industrial wastewater is introduced into the treatment tank 12. In addition, you may comprise so that to-be-processed water may perform the pre-process which removes a large sized contaminant in the pre-treatment tank 56 previously.

The carrier is added to the water to be treated in advance and introduced into the water to be treated. Or you may make it add a support | carrier to the to-be-processed water in a processing tank.
In the treatment tank 12, air is diffused by the air diffuser 30 attached below the membrane module 24.

  FIG. 5 is an explanatory diagram of the upward flow of the intermembrane flow path. As shown, the water to be treated introduced into the intermembrane flow path from below the membrane module 24 rises between the membranes together with the carrier by the upward flow of the diffused air. The carrier of the present embodiment is capable of flowing in the treatment tank 12 in an upward flow, has a density higher than that of water, and is a polyhedron. It moves at a slower flow than the upward flow. For this reason, in the horizontal width direction of the intermembrane flow path, the carrier existing around the casing is difficult to move to the central portion, and is present in a substantially uniform state in a dispersed state. Therefore, it is possible to move upward while being dispersed in the lateral width direction while moving from the inlet portion to the upper outlet portion where there is a diffuser for the intermembrane flow path.

  The carrier functions as a rectifier that moves while dispersing the intermembrane flow path, and thereby can flatten the gas-liquid two-phase flow velocity distribution in which a portion having a high flow velocity is generated at the center of the flow channel. Therefore, a shearing force based on the speed difference is generated on the film surface, so that the entire film surface can be evenly cleaned, and the cleaning effect can be improved with a normal amount of air diffused.

  In addition, the turbulence generated around the bubbles induces a shearing force and contributes to the membrane surface cleaning, and the density is higher than that of water, and turbulence due to fluid vortices and separation occurs around the polyhedral carrier. As a result, shearing force induced by these disturbances is also generated. Therefore, the location where shearing force is generated increases, and the effect of cleaning the membrane surface can be enhanced as compared with the conventional flat membrane type filtration device.

  In the membrane unit 20 immersed in the treatment tank 12, the filtration pump 58 is moved so that the filtered liquid (treated water) separated into solid and liquid passes through the membrane surface of the membrane element 22 and is connected to the outside through a pipe. To be discharged.

  FIG. 7 is an explanatory view of a modification of the flat membrane filtration device of the present invention. FIG. 8 is an explanatory diagram of the upward flow of the flat membrane filtration device of the modification. As shown in the figure, the modified flat membrane filtration apparatus 100 has a plurality of membrane modules 24a, 24b, and 24c stacked in multiple stages in the vertical direction in the treatment tank. Other configurations are the same as those of the apparatus shown in FIG. 1, and the same reference numerals are given and detailed description thereof is omitted. Even in the flat membrane filtration device 100 of such a modification, as shown in FIG. 8, the carrier that is substantially uniform in the horizontal width direction of the intermembrane flow path is maintained as it is in the lower membrane module 24c. In this state, they are sequentially supplied to the upper membrane modules 24b and 24a. For this reason, the difference in flow velocity distribution that has been noticeably generated in the uppermost membrane module 24a is eliminated, and the membrane surfaces in the entire range of the membrane modules 24a, 24b, and 24c can be evenly cleaned.

  The flat membrane filtration device and the flat membrane filtration method of the present invention can be widely applied in various membrane treatment fields in which solid-liquid separation using a flat membrane element is performed in addition to a membrane separation activated sludge device.

DESCRIPTION OF SYMBOLS 10,100 ......... Flat membrane filtration apparatus, 12 ......... Treatment tank, 20 ......... Membrane unit, 22 ......... Membrane element, 24 ......... Membrane module, 26 ......... Case, 28 ......... Piping 30 ......... Air diffuser, 40 ......... Carrier, 50 ......... Wastewater treatment system, 52 ......... Raw water piping, 54 ......... Raw water pump, 56 ......... Pretreatment tank, 58 ......... Filtration Pump, 200 ......... Membrane element, 202 ......... Membrane module, 204 ......... Air diffuser, 205 ...... Bubble, 206 ......... Side, 207 ......... Case.

Claims (5)

A membrane module in which side surfaces of a plurality of flat membranes arranged in parallel in a treatment tank for treatment water are surrounded by a casing is immersed, and an upward flow of the treatment water is generated between the membranes of the plurality of flat membranes. In a flat membrane filtration device for liquid separation,
It is possible to flow in the treatment tank by the upward flow, a carrier having a density higher than that of water is added to the treatment tank ,
The specific flow rate difference (F (de / W)), which is the speed difference between the carrier and the multiphase fluid, and the ratio of the equivalent diameter de of the carrier and the channel width W between the flat membranes are expressed by the following equation:
The flat membrane filtration device according to claim 1, wherein a ratio of the length of one side to the channel width between the flat membranes is 0.5 to 0.9 . A treatment tank for water to be treated;
A membrane module in which side surfaces of a plurality of flat membranes arranged in parallel in the treatment tank are surrounded by a casing;
Aeration means for aspirating the flow path between the flat membranes to generate an upward flow of the treated water;
A carrier capable of flowing in the treatment tank by the upward flow and having a density higher than that of water;
Bei to give a,
The specific flow rate difference (F (de / W)), which is the speed difference between the carrier and the multiphase fluid, and the ratio of the equivalent diameter de of the carrier and the channel width W between the flat membranes are expressed by the following equation:
The flat membrane filtration device according to claim 1, wherein a ratio of the length of one side to the channel width between the flat membranes is 0.5 to 0.9 .   The flat membrane filtration device according to claim 1, wherein the carrier is a polyhedron. The flat membrane filtration device according to any one of claims 1 to 3 , wherein the membrane modules are stacked in multiple stages in a vertical direction in the processing tank. A membrane module in which side surfaces of a plurality of flat membranes arranged in parallel in a treatment tank for treatment water are surrounded by a casing is immersed, and an upward flow of the treatment water is generated between the membranes of the plurality of flat membranes. In the flat membrane filtration method for liquid separation,
A carrier having a speed difference due to the upward flow with respect to the water to be treated is added to the treatment tank,
The specific flow rate difference (F (de / W)) and the ratio of the equivalent diameter de of the carrier and the flow path width W between the flat membranes are expressed by the following equation:
The carrier has a ratio of the length of one side to the channel width between the flat membranes of 0.5 or more and 0.9 or less, and the water to be treated is solid-liquid while dispersing the carrier in the channel between the membranes. A flat membrane filtration method characterized by separating.