JP4038367B2 - Membrane separation activated sludge treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a membrane separation activated sludge treatment method, and a continuous sludge layer adhering to the membrane surface of a membrane filter membrane is not affected by the action of air diffused from a diffuser installed in a biological reaction tank. In particular, the present invention relates to a membrane separation activated sludge treatment method that can be efficiently removed over the entire membrane membrane.
[0002]
[Prior art]
As is well known, membrane-separated activated sludge treatment consists of biological treatment (active sludge treatment) that decomposes organic matter in water to be treated by aerobic microorganisms in activated sludge and solid-liquid separation treatment by membrane module in the biological reaction tank. The membrane permeated water that has been permeated through the membrane module is taken out as a treated water by suction with a pump provided outside the biological reaction tank.
[0003]
FIG. 7 is an explanatory view of the configuration of a conventional membrane separation activated sludge treatment apparatus. In FIG. 7, reference numeral 51 denotes a biological reaction tank. Inside the biological reaction tank 51, water to be treated (a mixed solution of raw water and sludge reactants from the adjustment tank, which is a so-called activated sludge). A plurality of plate-like membrane modules 52 that are stored and arranged opposite to each other with a predetermined interval, and a diffuser that is located below these plate-like membrane modules 52 and has air holes that eject coarse bubbles. An air device (aeration tube) 56 is immersed and installed. A membrane separation unit 53 is constituted by a plurality of flat membrane modules 52 arranged to face each other at a predetermined interval. The diffuser (diffuser pipe) 56 is connected to a blower 57 outside the biological reaction tank 51.
[0004]
The flat membrane module 52 includes, for example, spacers 52b and 52b (for example, honeycomb net spacers) for securing membrane permeate flow channels on both surfaces of a plate-like support 52a as shown in FIG. ) To attach substantially square filtration membrane bodies 52c and 52c made of nonwoven fabric, and the peripheral edge portions of the filtration membrane bodies 52c and 52c are fixed by attachment frames 52d and 52d. As the filter membrane bodies 52c and 52c, a nonwoven fabric made of a polymer material such as polyester or polypropylene is used. In the flat membrane module 52, the membrane permeated water that has passed through the filtration membrane bodies 52c, 52c is taken out as treated water through a module branch pipe 54 provided at the upper end of the flat membrane module 52. A suction pump 58 is installed outside the biological reaction tank 51, and the module branch pipe 54 of each flat membrane module 52 constituting the membrane separation unit 53 passes through the collecting pipe 55 in the middle of the pipeline. The suction pump 58 is connected to a treated water extraction flow path 59 provided with the suction pump 58.
[0005]
The membrane-separated activated sludge treatment apparatus configured as described above performs the treatment by the flat membrane module 52 while purifying the water to be treated by supplying oxygen to the aerobic microorganisms with the air diffused from the air diffuser 56. Membrane separation activated sludge treatment is performed in which water is solid-liquid separated and filtered, and membrane permeated water that has permeated through the membrane module 52 is treated as treated water and led out of the biological reaction tank 51 by the suction pump 58.
[0006]
In this conventional membrane separation activated sludge treatment apparatus, the diffused air diffused from the diffuser 56 is used to promote the activity of aerobic microorganisms, and adheres to the membrane surfaces of the filtration membrane bodies 52c and 52c. The sludge layer (organic polymer substances and solids in activated sludge) is removed. That is, the coarse bubbles that diverge from the diffuser 56 disposed below the flat membrane module 52 and rise and the upward flow generated thereby shear the membrane surfaces of the filtration membrane bodies 52c and 52c of the flat membrane module 52. A force is applied to remove the sludge layer adhering to the membrane surfaces of the filtration membrane bodies 52c, 52c.
[0007]
[Problems to be solved by the invention]
However, in the conventional membrane separation activated sludge treatment device described above, when the air is diffused by the air diffuser, the air diffuser that generates coarse bubbles with priority on the effect of removing the sludge layer is used. Compared with a device equipped with an air diffuser for fine bubbles, the size of the air supply system is increased and a large aeration power is required.
[0008]
Also, when removing the sludge layer adhering to the membrane surface of the filtration membrane body, in the gas-liquid two-phase flow consisting of rising bubbles and the water flow generated thereby, the bubble passage path is uniformly formed over the entire area between the flat membrane modules. Difficult to do. Further, in the conventional membrane separation activated sludge treatment apparatus, in order to generate an upward flow due to the diffusion of the air diffuser, a region where the downward flow flows outside the membrane separation unit containing a plurality of flat membrane modules. It is necessary to secure enough. The area required for the downward flow to occupy the installation area (bottom area) of the biological reaction tank is about three times the installation area of the membrane separation unit. For this reason, the membrane separation unit can be installed only in a portion of about 25% of the installation area of the biological reaction tank, and the activated sludge treatment capacity per installation area of the biological reaction tank is low.
[0009]
This invention is made | formed in view of such a situation, Comprising: The objective of this invention is not based on the effect | action of the air diffused from the diffuser installed in the biological reaction tank, and the membrane filter membrane An object of the present invention is to provide a membrane separation activated sludge treatment method capable of removing a sludge layer adhering to a membrane surface of a body continuously and efficiently over the entire filtration membrane body.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that the water to be treated is filtered by the membrane membrane of the membrane module immersed in the biological reaction tank, and the membrane permeated water that has passed through the membrane module is treated. In the membrane-separated activated sludge treatment method in which water is taken out as a water by a pump provided outside the biological reaction tank, the membrane module has a bag shape that shrinks and expands by changing its volume in synchronization with suction and discharge of the pump. Using a bag-like membrane module having a filtration membrane body, when sucking by a pump, the membrane permeated water that has permeated the bag-like membrane module is drawn into the pump, and when discharged by the pump, the membrane permeated water in the pump is drained. A membrane separation activated sludge treatment method, wherein the membrane permeated water is returned to the bag-like membrane module while being taken out as treated water.
[0011]
The invention according to claim 2 is the membrane separation activated sludge treatment method according to claim 1, wherein the bag-like membrane module which is immersed and installed in a plurality of stages in the depth direction in the biological reaction tank is provided at each stage. The pumps for the bag-like membrane module are operated in parallel with their phases shifted.
[0012]
According to the membrane separation activated sludge treatment method of the present invention, the membrane permeated water that has passed through the bag-like membrane module is drawn into the pump when sucked by the pump, and the membrane permeated water in the pump is discharged when discharged by the pump. Among them, a part of the specified amount is taken out as treated water, while the rest is returned to the bag-like membrane module, so that the bag-like filtration membrane body of the bag-like membrane module sucks The volume changes and contracts / expands in synchronization with the suction / discharge of the pump that repeats and discharges. As the pump used in the membrane separation activated sludge treatment method according to the present invention, a positive displacement pump such as a reciprocating crank pump is suitable.
[0013]
Accompanying such shrinkage and expansion of the bag-like filtration membrane body, an inertial force acts on the membrane surface of the bag-like filtration membrane body to shake off the attached sludge layer. In addition, with the shrinkage and expansion of the bag-shaped filtration membrane body, a flow of water to be treated is generated between the opposed and adjacent bag-like membrane modules (see FIG. 4), and the membrane surface of the bag-like filtration membrane body. The shearing force due to the generated water to be treated acts on the. In this way, the bag-like membrane member of the bag-like membrane module contracts and expands in synchronism with the suction and discharge of the pump, and the inertial force accompanying the contraction and expansion of the bag-like membrane member The sludge layer adhering to the membrane surface of the bag-like filtration membrane body is continuously removed efficiently over the entire filtration membrane body by the shearing force caused by the generated flow and without the action of air diffused from the diffuser. Can be removed. The suction / discharge cycle of the positive displacement pump (the frequency of the piston that reciprocates the positive displacement pump) is set to, for example, about 0.25 Hz.
[0014]
Further, with respect to the bag-like membrane module that is immersed in a plurality of stages in the depth direction in the biological reaction tank, for example, the upper stage, the middle stage, and the lower stage, the pumps for each stage of the bag-like membrane module are mutually phased, for example, 120 ° By shifting in parallel and shifting, it is possible to generate a flow that rises in order from the lower bag-like membrane module to the upper bag-like membrane module (see FIG. 6). It is possible to prevent a decrease in biological treatment capacity caused by
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of an apparatus (membrane separation activated sludge treatment apparatus) for carrying out a membrane separation activated sludge treatment method according to an embodiment of the present invention.
[0016]
In FIG. 1, reference numeral 1 denotes a biological reaction tank. In the biological reaction tank 1, water to be treated (mixed solution of raw water and sludge-like reactant from the adjustment tank) is stored and at a predetermined interval. And a plurality of bag-like membrane modules 2 which will be described later, and a microbubble diffuser (spreader) which is located below these bag-like membrane modules 2 and has aeration holes for ejecting microbubbles. The trachea) 6 is installed by immersion. A membrane separation unit 3 is constituted by the plurality of bag-like membrane modules 2. The fine bubble diffuser 6 is connected to a blower 7 outside the biological reaction tank 1.
[0017]
The module branch pipes 4 connected to the respective bag-like membrane modules 2 are connected to the collecting pipes 5 respectively. A reciprocating crank pump (hereinafter simply referred to as a reciprocating pump) 9, a check valve 8, and a flow control valve 10, which are one of positive displacement pumps, are installed outside the biological reaction tank 1. 5, a treated water outlet passage 11 having a reciprocating pump 9, a check valve 8, and a flow rate adjusting valve 10 provided in this order is provided. Further, a membrane permeated water return channel 12 is provided for branching from the pump discharge port side of the reciprocating pump 9 and returning to the collecting pipe 5.
[0018]
FIG. 2 is a front view showing an example of the bag-like membrane module 2, and FIG. 3 is a diagram schematically showing an enlarged cross section taken along the line AA of FIG.
[0019]
The bag-like membrane module 2 is formed by forming a bag-like filtration membrane body 23 on a substantially square support frame 21. As shown in FIGS. 2 and 3, filtration membrane bodies 24, 24 that can be displaced by attachment frames 22, 22 are attached to both surfaces of a substantially square support frame 21. The filtration membrane bodies 24, 24 are attached to substantially square linear frames (wire frames) 24c, 24c in a state where substantially square filtration membranes 24a, 24a made of non-woven fabric are tensioned, and the linear frames 24c, 24c. Further, a volume-changing non-permeable membrane 24b, 24b having a substantially square wide frame shape is attached to the periphery thereof. A bag-like filtration membrane body 23 is formed by attaching the pair of displaceable filtration membrane bodies 24, 24 to the support frame 21. In this case, the bag-shaped filtration membrane 23 changes its volume in synchronism with the suction / discharge of the reciprocating pump 9, and the volume-variable non-permeable membranes 24b, 24b of the bag-like filtration membrane 23 are contracted / expanded. However, it is fixed to the support frame 21 with a slack. The membrane permeated water that has passed through the bag-like filtration membrane body 23 is taken out via the module branch pipe 4 provided on the upper portion of the support frame 21.
[0020]
As the filtration membranes 24a and 24a, a nonwoven fabric made of a polymer material such as polyester or polypropylene and having an aperture of 0.1 to 1 μm is suitable. The variable volume non-permeable membranes 24b, 24b are preferably made of a polymer material such as polyester or polypropylene, and the linear frames 24c, 24c are preferably made of stainless steel. .
[0021]
Next, a membrane separation activated sludge treatment method performed using the apparatus will be described. Here, the frequency of the reciprocating piston of the reciprocating pump 9 is set to, for example, 0.25 Hz (rotation speed: 15 rpm), and the flow rate adjusting valve 10 is, for example, per 1 m ² of the filtration membrane area of the bag-like membrane module 2. It is set to extract 0.6m ³ / m ² · day of treated water. When the reciprocating pump 9 is operated, at the time of suction by the pump 9, the bag-like filtration membrane body 23 of each bag-like membrane module 2 changes in volume and contracts into a concave lens shape in cross section (shown by an imaginary line in FIG. 1). In addition, the membrane permeated water that has passed through each of the bag-like membrane modules 2 is drawn into the reciprocating pump 9.
[0022]
Next, at the time of discharge by the reciprocating pump 9, a part of the membrane permeated water in the reciprocating pump 9 is taken out as treated water through the flow rate adjusting valve 10 having the flow rate set. Meanwhile, at the same time, the remaining most of the remaining amount is returned to each bag-like membrane module 2 via the membrane permeate return channel 12, and the bag-like filtration membrane body 23 of each bag-like membrane module 2 has a volume. It changes and expands into a cross-sectional convex lens shape (shown by a solid line in FIG. 1). In this way, the bag-like filtration membrane body 23 of the bag-like membrane module 2 takes out a predetermined amount of treated water in synchronization with the suction / discharge of the reciprocating pump 9 that repeats suction and discharge. The volume changes and contracts and expands.
[0023]
As a result, as shown in FIG. 4, the attached sludge layer is shaken off on the membrane surface of the bag-like filtration membrane body 23 as the bag-like filtration membrane body 23 (bag-like membrane module 2) contracts and expands. Inertia acts to eliminate it. In addition, a flow of water to be treated is generated between adjacent bag-like membrane modules 2, and a shearing force due to the flow of the water to be treated acts on the membrane surface of the bag-like filtration membrane body 23. That is, in the process from the inflated state to the contraction, a downward flow and an upward flow toward the center part between the bag-like membrane modules 2 occur, and conversely, in the process from the contracted state to the expansion, from the center part between the bag-like membrane modules 2. Ascending and descending flows are generated. The inertial force is maximized when the bag-shaped filtration membrane body 23 is expanded most and contracted (top dead center and bottom dead center of the reciprocating pump 9). On the other hand, as shown in FIG. 4, the shear force becomes maximum when the phase is shifted by 90 °. As a result, a substantially equal sludge layer removing effect can be obtained in any of the suction and discharge phases of the reciprocating pump 9. In this way, the bag-like filtration membrane body 23 of each bag-like membrane module 2 contracts and expands as a whole in synchronism with the suction and discharge of the reciprocating pump 9, and the inertial force associated therewith is generated. The sludge layer adhering to the membrane surface of the bag-like filtration membrane body 23 is continuously spread over the entire filtration membrane body due to the shearing force caused by the flow, and not by the action of air diffused from the aeration device 6 unlike the prior art. It can be removed efficiently.
[0024]
Thereby, the maintenance operation | work which stops the driving | operation of an apparatus and scrapes off the sludge layer of a film | membrane surface can be reduced compared with the past. Moreover, since the sludge layer on the membrane surface is not removed by the action of air diffused from the diffuser 6 installed in the biological reaction tank 1, it is only necessary to diffuse the oxygen for supplying microorganisms. Therefore, the air supply system can be downsized compared to the conventional system to reduce the aeration power, and unlike the conventional system, a region where the downward flow flows outside the membrane separation unit in order to generate an upward flow due to aeration. Since it is not necessary to secure enough, the bag-like membrane module 2 (membrane separation unit 3) can be installed over almost the entire installation area of the biological reaction tank 1, and activated sludge per installation area of the biological reaction tank 1 The throughput can be increased.
[0025]
FIG. 5 is a structural explanatory view showing an example of an apparatus (membrane separation activated sludge treatment apparatus) for carrying out a membrane separation activated sludge treatment method according to another embodiment of the present invention. The difference from FIG. 1 is that the membrane separation units 103A to 103C each having a plurality of bag-like membrane modules are immersed and installed in the biological reaction tank 101 in the depth direction over the upper stage, the middle stage, and the lower stage, The reciprocating pumps 109A to 109C for the membrane separation units 103A to 103C are operated in parallel with their phases sequentially shifted by 120 °.
[0026]
As shown in FIG. 5, an aeration device for fine bubbles (aeration tube) 106 is immersed in a biological reaction tank 101 in which water to be treated is stored. The fine bubble diffuser 106 is connected to a blower 107 outside the biological reaction tank 101. Further, a plurality of bag-like membrane modules 102A constituting the upper membrane separation unit 103A are immersed in the upper part of the biological reaction tank 101. The configuration of the bag-like membrane module 102A is the same as that of the bag-like membrane module 2 of FIG. 1, and the description thereof is omitted. A module branch pipe 104A connected to each bag-like membrane module 102A is connected to a collecting pipe 105A. The bioreactor 101 has the same configuration as the apparatus shown in FIG. 1, and a reciprocating pump 109A, a check valve 108A, and a flow rate adjusting valve 110A are provided in this order starting from the collecting pipe 105A. A treated water outlet channel 111A is provided. Further, a membrane permeated water return channel 112A is provided to branch from the pump discharge port side of the reciprocating pump 109A and return to the collecting pipe 105A.
[0027]
Further, below the upper membrane separation unit 103A, a plurality of bag-like membrane modules 102B constituting the membrane separation unit 103B located in the middle are immersed. The configuration of the bag-like membrane module 102B is the same as that of the bag-like membrane module 2 of FIG. The bag-like membrane module 102B has the same configuration as the apparatus shown in FIG. 1, and includes a module branch pipe 104B, a collecting pipe 105B, a reciprocating pump 109B, a check valve 108B, a flow rate adjustment valve 110B, and a treated water take-out. A channel 111B and a membrane permeated water return channel 112B are provided.
[0028]
Further, below the middle membrane separation unit 103B, a plurality of bag-like membrane modules 102C constituting the membrane separation unit 103C located at the lower level are immersed and installed. The configuration of the bag-like membrane module 102C is the same as that of the bag-like membrane module 2 of FIG. The bag-like membrane module 102C has the same configuration as the apparatus shown in FIG. 1, and includes a module branch pipe 104C, a collecting pipe 105C, a reciprocating pump 109C, a check valve 108C, a flow rate adjustment valve 110C, and a treated water take-out. A channel 111C and a membrane permeated water return channel 112C are provided.
[0029]
The reciprocating pumps 109A to 109C are operated in parallel with a phase difference of 120 ° in crank angle.
[0030]
In such an apparatus configuration, when the reciprocating pumps 109A to 109C are operated in parallel with a phase difference of 120 °, the bag-like membrane modules 102A to 102C of each stage are determined with a phase difference of 120 °. While taking out an amount of treated water, the bag-like filtration membranes of the bag-like membrane modules 102A to 102C change in volume and contract and expand in synchronization with the suction and discharge of the reciprocating pumps 109A to 109C.
[0031]
Therefore, the sludge layer adhering to the membrane surface of the bag-like filtration membrane body of each of the bag-like membrane modules 102A to 102C is continuously removed over the entire filtration membrane body without being influenced by the air diffused from the air diffuser 106. Can be removed well. Furthermore, in this embodiment, three reciprocating pumps 109A to 109C with respect to the three-stage bag-like membrane modules 102A to 102C are operated in parallel with a phase shifted by 120 °, so that the three stages are arranged as shown in FIG. With respect to the formed bag-like membrane modules 102A to 102C, it is possible to cause a flow that rises in order from the lower bag-like membrane module to the upper bag-like membrane module as the phase advances by 120 °. Thereby, sedimentation of microorganisms can be prevented, and a decrease in biological treatment ability by microorganisms can be prevented.
[0032]
【The invention's effect】
As described above, according to the membrane separation activated sludge treatment method of the first aspect of the present invention, the bag-like membrane module having the bag-like filtration membrane body that changes in volume and contracts / expands in synchronization with the suction / discharge of the pump. The membrane permeated water that has passed through the bag-like membrane module is drawn into the pump when sucked by the pump, and a part of the membrane permeated water in the pump is taken out as treated water when discharged by the pump. On the other hand, since the rest other than that is returned to the bag-shaped membrane module, the membrane of the bag-shaped filtration membrane body is not affected by the action of air diffused from the air diffuser installed in the biological reaction tank. The sludge layer adhering to the surface can be continuously removed efficiently over the entire filtration membrane body. Thereby, the maintenance operation | work which stops the driving | operation of an apparatus and scrapes off the sludge layer of a film | membrane surface can be reduced compared with the past. In addition, since it is only necessary to diffuse air to supply oxygen to microorganisms, it is possible to reduce the aeration power by reducing the size of the air supply system equipment compared to the conventional method, and unlike the conventional method, the upward flow caused by aeration is reduced. Since it is not necessary to secure a sufficient area for the downward flow to flow outside the membrane separation unit in order to generate the bioreactor, the bag-like membrane module can be installed over almost the entire area of the bioreactor. The amount of activated sludge treatment per installation area can be increased.
[0033]
According to the membrane-separated activated sludge treatment method of the invention of claim 2, in addition to the above-described effect, the bag-like membrane module of each stage is provided for the bag-like membrane module that is immersed in a plurality of stages in the depth direction in the biological reaction tank. By operating the pumps for the modules out of phase in parallel, it is possible to generate an upward flow from the lower bag-like membrane module to the upper bag-like membrane module, thereby preventing sedimentation of microorganisms. , It is possible to prevent a decrease in biological treatment capacity due to microorganisms.
[Brief description of the drawings]
FIG. 1 is a configuration explanatory view showing an example of an apparatus for carrying out a membrane separation activated sludge treatment method according to an embodiment of the present invention.
2 is a front view showing an example of the bag-like membrane module in FIG. 1. FIG.
FIG. 3 is a diagram schematically showing an enlarged cross section taken along line AA in FIG. 2;
FIG. 4 is a diagram for explaining an inertial force accompanying shrinkage / expansion of a bag-like filtration membrane body (bag-like membrane module) and a shearing force caused by the flow of water to be treated.
FIG. 5 is an explanatory diagram showing an example of an apparatus for carrying out a membrane separation activated sludge treatment method according to another embodiment of the present invention.
FIG. 6 is a view for explaining the operation of the membrane separation activated sludge treatment method of the present invention carried out using the apparatus of FIG.
FIG. 7 is a configuration explanatory view of a conventional membrane separation activated sludge treatment apparatus.
8 is a schematic cross-sectional view showing the configuration of the flat membrane module in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,101 ... Biological reaction tank 2,102A-102C ... Bag-shaped membrane module 21 ... Support frame 22 ... Mounting frame 23 ... Bag-shaped filtration membrane body 24 ... Filtration membrane body 24a ... Filtration membrane 24b ... Non-permeable for variable volume Membrane 24c ... Linear frame 3,103A-103C ... Membrane separation unit 4,104A-104C ... Module branch pipe 5,105A-105C ... Collecting pipe 6,106 ... Air diffuser for fine bubbles 7,107 ... Blower 8,108A ... 108C ... Check valve 9, 109A to 109C ... Reciprocating crank pump 10, 110A to 110C ... Flow rate adjustment valve 11, 111A to 111C ... Process water take-out flow path 12, 112A to 112C ... Membrane permeated water return flow path

Claims (2)

The water to be treated is filtered by the membrane membrane of the membrane module immersed in the biological reaction tank, and the membrane permeated water permeated through the membrane module is taken out as treated water by a pump provided outside the biological reaction tank. In the membrane separation activated sludge treatment method as described above, the membrane module is a bag-like membrane module having a bag-like filtration membrane body whose volume is changed and contracted / expanded in synchronization with the suction / discharge of the pump. Sometimes, the membrane permeated water that has passed through the bag-like membrane module is drawn into the pump, and when discharged by the pump, the membrane permeated water in the pump is taken out as treated water, and a part of the membrane permeated water is A membrane separation activated sludge treatment method characterized by returning to a bag-like membrane module. 2. The bag-like membrane module immersed in a plurality of stages in the depth direction in the biological reaction tank is operated in parallel with the pumps for the bag-like membrane modules at each stage shifted in phase. Membrane separation activated sludge treatment method.

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