JP2007209949A - Filtrate recovery device of solid-liquid mixed/processed liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filtrate recovery device of a solid-liquid mixed/processed liquid capable of completely suspending the flow of a liquid concurrently with the shutdown of a suction pump, as if the suction pump were installed at a position below the liquid level of an aeration tank and obtaining a cleaning effect as expected by air scrubbing. <P>SOLUTION: A membrane filtering unit 5 having an air-diffusion device 15 is dipped downward of a membrane separation module 9 inside the aeration tank 4, the solid-liquid mixed/processed liquid is solid-liquid separated by the module concurrently with air-diffusion by the diffuser 15, a filtrate is suction-recovered from the membrane separation module 9 through a suction tube of the filtrate rising upward of the liquid level of a gas-liquid mixed/processed liquid in the tank 4. The suction pump Pv connected to the suction tube is disposed outside the tank 4 and downward of the liquid level, a waste liquid tube path 26 connected to a delivery outlet of the suction pump Pv is extended by rising upward and being bent downward and has a discharge outlet that is positioned downward of the liquid level. Further, a suction/discharge means 27 is disposed at the top section of the recovery tube path. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a filtrate recovery apparatus for membrane separation of a treatment liquid in an aeration tank applied to normal wastewater treatment, water purification treatment, membrane separation activated sludge treatment, and the like, and suctioning and collecting the filtrate with a suction pump.

  A membrane separation activated sludge treatment method, which is a typical example to which the apparatus of the present invention is applied, biologically treats organic matter contained in industrial wastewater and domestic wastewater, or wastewater containing microorganisms and bacteria, for example. Thus, solid-liquid separation is performed using various types of separation membranes, and the treated water is recovered or discharged into the treated water tank. Conventional membrane separation activated sludge treatment equipment is equipped with a raw water adjustment tank, a denitrification tank and an aeration tank. In the raw water adjustment tank, the liquid level in the tank is measured by a liquid level gauge, and the liquid feed pump is driven intermittently. Thus, the liquid level in the tank is adjusted to be within a predetermined range. After the raw water sent by the liquid feed pump is introduced into the denitrification tank, the raw water overflowing from the denitrification tank is caused to flow into the adjacent aeration tank. A membrane filtration unit is immersed in this aeration tank. This membrane filtration unit separates the membrane into activated sludge contaminants and treated water, and the filtered treated water is sucked by a suction pump and collected or discharged into a treated water tank. Most of the excess sludge in the aeration tank is sent to the sludge storage tank where it is stored, dried and then incinerated. A part of the excess sludge is returned to the denitrification tank by a liquid feed pump and circulates between the denitrification tank and the aeration tank.

  A typical example of the membrane filtration unit is a hollow fiber membrane module obtained by arranging a plurality of sheet-like hollow fiber membrane elements in which a large number of porous hollow fibers are arranged in parallel on the same plane at a predetermined interval. And an air diffuser disposed below the hollow fiber membrane module. As for the said hollow fiber membrane module, the whole shape which consists of a plurality of hollow fiber membrane element has comprised the substantially rectangular parallelepiped. On the other hand, in the diffuser, a plurality of diffuser tubes each having a hole or a slit are provided in a pipe made of, for example, metal or resin, and one end of each diffuser tube is connected to the aeration blower. The air sent from the aeration blower is changed to bubbles through a diffuser and discharged into sludge. When treating domestic wastewater, industrial wastewater, etc., the organic matter is adsorbed to the aerobic microorganisms by bringing the air generated from the diffuser into contact with the organic matter in the sludge of the aeration tank in the presence of aerobic microorganisms Metabolized and biologically treated with sludge.

  The hollow fiber membrane module and the air diffuser are surrounded by a rectangular cylindrical blocking plate that opens upward and downward. This shielding plate becomes a wall part for generating a gas-liquid mixed flow by the rising of the bubbles generated from the air diffuser and guiding the flow from the upward flow to the downward flow. The gas-liquid mixed flow generated by the bubbles discharged from the diffuser does not scatter in an oblique direction, but rises straight and efficiently contacts the hollow fiber membrane module. At this time, the hollow fiber membrane is oscillated by the uniform dispersion of the gas-liquid mixed flow with respect to the membrane surface of the hollow fiber membrane module to uniformly wash the hollow fiber membrane elements. In addition, when the gas-liquid mixed flow is generated, oxygen in the air dissolves to efficiently perform the biological treatment, and the sludge is separated into pollutants and treated water by the filtration function of the hollow fiber membrane. . One end of the water collection header pipe of the membrane filtration unit is connected to a suction pump through a suction pipe, and treated water (filtered water) filtered by the membrane filtration unit is sucked through the suction pipe and processed. It is collected or released into the water tank.

  As the membrane module, in addition to a sheet-like hollow fiber membrane element having a porous hollow fiber as a constituent member, one having a filtration membrane having a plurality of fine pores is used, for example, a flat membrane type, There are various known separation membranes such as a tubular membrane type and a bag-like membrane type. Examples of the material include cellulose, polyolefin, polysulfone, PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), and ceramics. Thus, hollow fiber membrane modules using hollow fiber membrane elements are widely used because of a large filtration area.

  The average pore diameter of the micropores formed in the porous hollow fiber is generally an average pore diameter of 0.001 to 0.1 μm for a membrane called an ultrafiltration membrane, and an average pore size of 0.1 to 1 μm for a membrane generally called a microfiltration membrane. It is. For example, when used for solid-liquid separation of activated sludge, the pore diameter is preferably 0.5 μm or less, and when sterilization is required as in the case of filtration of purified water, the pore diameter is preferably 0.1 μm or less.

  On the other hand, in order to prevent early clogging of the hollow fiber membrane module, for example, as described in International Publication No. 2004/028672 pamphlet (Patent Document 1), it is discharged from an aeration diffuser. A so-called air scrubbing cleaning is performed in which a hollow fiber or a hollow fiber membrane element is swung by using a gas-liquid mixed flow generated by relatively large bubbles to separate and clean sludge substances adhering to the membrane surface. Furthermore, back washing in which filtered water is reversely passed from the hollow inside of the hollow fiber membrane to the outside of the membrane may be performed, and the filtration performance of the filtration membrane is recovered by such washing.

According to Patent Document 1, as described above, the membrane filtration unit includes a diffuser at the bottom, and at the same time as the air is discharged from the diffuser, the filtered water is sucked by the suction pump. Part of is stored in the backwash tank. After filtering for a certain period of time, scrubbing cleaning is performed using air from an aeration blower connected to a diffuser, and backwashing is performed using filtered water in a backwash tank by a backflow pump. At that time, the chemical solution in the chemical solution tank is injected into the backwash water by the chemical solution pump, and cleaning with the chemical solution is performed simultaneously with the reverse cleaning. Here, the scrubbing cleaning and the reverse cleaning may be performed simultaneously, or the scrubbing cleaning and the reverse cleaning may be performed separately. Also, for example, scrubbing cleaning, back cleaning, scrubbing cleaning, and back cleaning can be performed alternately. Furthermore, it is possible to perform either scrubbing washing or back washing.
International Publication No. 2004/028672 Pamphlet

  Incidentally, although not specifically described in Patent Document 1, a suction pipe for sucking filtrate water from each membrane filtration unit disposed in the aeration tank by a suction pump is usually a suction pump. It is installed on the ground and connected to the upper end of a branch pipe that extends vertically upward from the water collection header pipe arranged at the upper end of each membrane filtration unit, and is arranged horizontally above the liquid level in the tank. After that, it is connected to the suction pump installed on the ground outside the tank. The filtered water sucked by the suction pump is guided to the treated water tank through the recovery pipe line.

  As described above, in this type of membrane-separated activated sludge treatment, the transmembrane pressure difference generally increases due to the adhesion of pollutants, causing clogging. Therefore, in order to suppress this clogging, the suction pump is intermittently driven, and the filtration operation and the air scrubbing cleaning are alternately performed. If the suction pump is installed at a position lower than the liquid level as described above, the flow of filtered water is maintained according to the siphon principle even when the suction pump is temporarily stopped, and it does not stop completely. As a result, new contaminants continue to adhere to the membrane surface, and the increase in transmembrane pressure difference cannot be suppressed as expected, and the cleaning effect by air scrubbing cannot be expected.

  The present invention has been developed to solve such a problem. Even when the suction pump is installed at a position lower than the liquid level of the aeration tank, the liquid flow is completely stopped simultaneously with the stop of the suction pump. An object of the present invention is to provide an apparatus for collecting a filtrate of a solid / liquid mixed treatment liquid that can obtain an expected cleaning effect by air scrubbing.

  Such a problem is a basic configuration of the present invention, in which a membrane filtration unit in which an air diffuser is disposed below the membrane separation module is immersed in a treatment tank, and simultaneously with the air diffused by the air diffuser, the membrane separation module Solid-liquid separation of the solid-liquid mixed treatment liquid, and suction and recovery of the filtrate from the membrane separation module via the filtrate suction line extending above the liquid level of the gas-liquid mixed treatment liquid in the treatment tank A separation device, wherein a suction pump connected to the suction pipe is outside the processing tank and disposed below the liquid surface, and a recovery pipe connected to the discharge port of the suction pump And rising upward from the liquid level and then bending and extending downward to be connected to a drainage port located below the liquid level, and an intake / exhaust means is disposed at the top of the recovery line. Effectively by the filtrate recovery device of the solid-liquid mixed processing liquid characterized by It is determined. According to a preferred aspect of the present invention, the intake / exhaust means is a shuttle valve or a quick exhaust valve.

Effect

  As can be understood from the above configuration, the basic configuration of the present invention is that when the suction line from the membrane filtration unit to the suction pump has a so-called siphon structure, the siphon structure is further provided in the drain line on the discharge port side of the suction pump. The intake / exhaust means is provided at the top of the conduit, and the intake / exhaust means is activated when the suction pump is temporarily stopped to send the atmosphere into the conduit, causing the liquid to run out. Stop the siphon function. As a result, the suction pump is stopped and the intake air is made at the same time, the flow of the filtrate in the pipeline is completely stopped, the scrubbing cleaning effect is enhanced, and the filtration efficiency is not lowered due to the increase in transmembrane pressure difference. .

  When the filtration operation is resumed, the suction pump is activated and the intake / exhaust means is activated to discharge the air accumulated in the pipe line to the atmosphere. The exhaust by the intake / exhaust means at this time is automatically exhausted by the increased pressure because the hydraulic pressure in the drainage pipe rises by driving the suction pump. Alternatively, a pilot signal is output to the intake / exhaust means at the same time as the suction pump is started, and the exhaust is performed. Therefore, a shuttle valve or a quick exhaust valve is preferably used as the intake / exhaust means. However, in addition to these valves, a poppet check valve or the like can be used. In short, it is important that the intake / exhaust means includes a mechanism for intake and exhaust by changes in internal pressure.

Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 shows a schematic configuration of an aeration process in a membrane separation activated sludge treatment apparatus which is a typical embodiment of a solid-liquid separation apparatus for a solid-liquid mixed treatment liquid according to the present invention.

  According to the membrane separation activated sludge treatment apparatus, the raw water introduced into the raw water adjustment tank (not shown) is intermittently transferred to the denitrification tank (not shown) by a liquid feed pump (not shown) so as to maintain a predetermined liquid level range. Then, the raw water overflowing from the denitrification tank is introduced into the adjacent aeration tank 4. A large number of membrane filtration units 5 are immersed in the sludge of the aeration tank 4. The treated water membrane-separated into activated sludge and treated water by the membrane filtration unit 5 is sent to the treated water tank by the suction pump Pv and collected or discharged as it is. On the other hand, a part of the concentrated sludge composed of microorganisms which have been aerated in the aeration tank 4 and proliferated is stored in a sludge storage tank (not shown). A part of the concentrated sludge inside the aeration tank 4 is returned to the denitrification tank by a liquid feed pump (not shown) and circulated.

  FIG. 2 shows a typical example of a normal membrane filtration unit 5. As shown in the figure, the membrane filtration unit 5 includes a hollow fiber membrane module 9 which is a membrane separation module which is a membrane separation module in which a plurality of hollow fiber membrane elements 10 arranged vertically in the yarn length direction are supported and fixed in parallel. The air diffuser 15 is disposed below the hollow fiber membrane module 9 at a required interval. The hollow fiber membrane element 10 communicates and supports the upper end opening end of a membrane sheet 11 in which a large number of porous hollow fibers 10a are arranged in parallel to the filtered water discharge pipe 12 through a potting material 11a, and the lower end thereof. It is closed and fixed and supported by the lower frame 13 via the potting material 11a, and both ends of the filtered water outlet pipe 12 and the lower frame 13 are supported by a pair of vertical rods 14. A large number of hollow fiber membrane elements 10 are accommodated and supported in parallel in substantially the entire volume of a rectangular cylindrical upper wall member 20 whose upper and lower end surfaces are open with the sheet surface vertical. Here, in the hollow fiber membrane element 10, generally, as shown in FIG. 3, a large number of porous hollow fibers 10a are arranged in parallel on the same plane with the same gap.

In this embodiment, the porous hollow fiber 10a is made of PVDF (polyvinylidene fluoride) hollow hollow fiber that is hollow in the longitudinal direction along the center, and the pore diameter of the filtration hole is 0.4 μm. The effective membrane area per sheet is 25 m ² . The sheet-like hollow fiber membrane element 10 is used in 20 pieces per membrane filtration unit 5 and has a depth of 30 mm, a width of 1250 mm, and a length from the upper surface of the filtrate extraction pipe 12 to the lower surface of the lower frame 13. Is 2000 mm. The size of the single membrane filtration unit 5 including the air diffuser 15 is 1552.5 mm in depth, 1447 mm in width, and 3043.5 mm in height. The filtered water extraction pipe 12 has a length of 1280 mm, its material is ABS resin, and the vertical rod 14 is made of SUS304.

  However, the material such as the porous hollow fiber 10a, the filtrate extraction pipe 12, and the vertical rod 14, the size of the hollow fiber membrane element 10, the size of the membrane filtration unit 5, and the number of the hollow fiber membrane elements 10 per unit Etc. can be variously changed according to the application. For example, in terms of the number of the hollow fiber membrane elements 10, it can be arbitrarily set to 20, 40, 60,... According to the processing amount, or the material of the porous hollow fiber 10a can be cellulose, polyolefin, Conventionally known materials such as polysulfone-based, polyvinyl alcohol-based, polymethyl methacrylate, and polyfluorinated ethylene can be applied.

  At one end of the filtrate extraction pipe 12 of each hollow fiber membrane element 10, an outlet 12a for high-quality filtered water (treated water) filtered by each porous hollow fiber 10a is formed. In this embodiment, an L-shaped joint 12b is attached to each outlet 12a in a liquid-tight manner via a sealing material, similarly to the membrane filtration unit 5 shown in FIG. Moreover, as shown in FIG. 3, the water collection header pipe | tube 21 is installed horizontally along the edge by the side in which the said outlet 12a is formed in the upper end of the said upper wall material 20. As shown in FIG. The water collecting header pipe 21 is formed with water collecting ports 21a at positions corresponding to the plurality of outlets 12a, and an L-shaped joint 21b similar to the outlet 12a serves as a sealing material in each water collecting port 21a. It is liquid-tightly attached.

  The treated water outlet 12a of the filtered water outlet 12 and the water outlet 21a of the water header 21 are connected to each other by connecting the L-shaped joints 12b and 21b attached to each other. . At one end of the water collection header pipe 21, a water suction port 21 c connected to the suction pump Pv via the filtered water suction pipe line 22 is formed. As shown in FIG. 1, the water inlet 21 c formed for each water collection header pipe 21 and the filtered water suction pipe 22 are inserted into branch pipes 22 a branched from the filtered water suction pipe 22. It is connected via a mounted flow rate adjusting valve 23. Here, the branch line 22a rises from the water collection header pipe 21 to an upper position higher than the liquid level of the aeration tank 4, and is connected to the filtered water suction lines 22 arranged horizontally. In the present embodiment, the filtered water suction pipe 22 that is arranged horizontally and extends outside the tank is connected to a suction port of a suction pump Pv that is bent downward outside the tank and installed on the ground. Yes.

  A drain line 26 is connected to the discharge port of the suction pump Pv, and the filtered water is sent to a treated water tank (not shown) or discharged as it is. The drainage pipe 26 constitutes the most characteristic part of the present invention, and the drainage pipe 26 connected to the suction pump Pv once rises to a position higher than the liquid level of the aeration tank 4. The siphon structure is formed by bending in an inverted U shape and extending downward, and arranging the drain side end at a position lower than the liquid level. Further, a check valve which is an intake / exhaust means 27 is provided at a bent portion which is a water head (a top portion) of the drainage pipe 26. As this check valve, it is preferable to use a shuttle valve, a quick exhaust valve, a pilot operated check valve, a poppet valve or the like.

  As shown in FIG. 4, the air diffuser 15 is formed of a rectangular cylindrical body that is coupled to the lower end of the upper wall member 20 and is open at the top and bottom, and has four support columns 24 a that extend downward from the lower ends of the four corners. Is housed and fixed at the bottom of the lower wall member 24 provided with. The diffuser 15 extends horizontally in the width direction along the front-side inner wall surface of the lower wall member 24, and passes through an aeration blower B and an air main pipe 18 arranged outside as shown in FIG. The air introduction pipe 16 is a branch pipe connected to each other, and the air introduction pipe 16 is disposed at a predetermined interval in the length direction, and one end is fixed and the other end is an inner wall on the back side. And a plurality of air diffusers 17 fixed horizontally along the line. The end of the diffuser pipe 17 connected to the air inlet pipe 16 communicates with the inside of the air inlet pipe 16, and the other end of the diffuser pipe 17 is closed. The air diffuser 15 according to the present embodiment is arranged corresponding to each of the plurality of membrane filtration units 5, and the air sent from the same aeration blower B is diverted to the respective air diffusers 15. An air main pipe 18 directly connected to B is provided, and the air main pipe 18 is connected to each air diffuser 15 through an air introduction pipe 16 that is a branch pipe.

  As described above, the plurality of membrane filtration units 5 immersed in the same aeration tank 4 are connected to the same filtered water suction line 22 via each branch line 22 a and the flow rate adjusting valve 23. When the sludge treatment is continuously performed for a long period of time, clogging progresses on the surface of the membrane of the membrane filtration unit 5, so that the filtration flow rate decreases or the transmembrane pressure difference increases. In order to suppress such an increase in transmembrane pressure difference, so-called air scrubbing is performed using a gas-liquid mixed fluid of air and sludge discharged from the air diffuser 15 disposed below the hollow fiber membrane element 10. At the same time, each porous hollow fiber 10a is swung to peel off and remove the suspended substances adhering to the membrane surface, thereby performing physical cleaning. At the same time, biological treatment is performed by activating the nitrification reaction by microorganisms.

  Here, the activated sludge in the aeration tank 4 is subjected to solid-liquid separation through the hollow portion of the porous hollow fiber 10a of the membrane filtration unit 5, and the filtered water is actively sucked by an external suction pump Pv, which is not shown in the drawing. Send it to the water tank and collect it. In this operation, the suction pump Pv is driven for 6 minutes and then stopped for 1 minute. That is, the suction operation of filtered water by the suction pump Pv is intermittently performed. The driving of the aeration blower B is maintained even during the filtration operation and at the time of stopping, and air is always sent to the air diffuser 15. Therefore, the hollow fiber membrane of the hollow fiber membrane module 9 swings and adheres to the membrane surface due to the upward flow of the gas-liquid mixture with the activated sludge generated by the bubbles released from the air diffuser 15 even during the filtration operation. The sludge deposits are peeled off from the membrane surface, and so-called air scrubbing cleaning is performed. In addition, when the filtration operation is stopped, filtered water suction from the hollow fiber membrane module 9 is not performed, and only air scrubbing is performed. Since the air scrubbing at this time is not filtered and sucked by the porous hollow fiber 10a, the adhesion of sludge is reduced, so the cleaning effect is extremely high compared to the filtration operation, and the transmembrane pressure difference is reduced. Increases recovery speed.

  By the way, when the filtration operation is intermittently performed as described above, the suction line 22 has a siphon structure as in the present embodiment, and the drainage line 26 has the same height as the suction pump Pv or lower than that. Then, even if the drive of the suction pump Pv is stopped, the filtered water continues to flow according to the principle of the siphon, impairs the air scrubbing effect, and the recovery of the transmembrane pressure difference is extremely delayed. Suction may be impossible.

  On the other hand, as in the present embodiment, the drainage pipe 26 is intentionally made into a siphon structure, and an intake / exhaust means 27 is provided at the top of the drain, and the top of the head is in the atmosphere in accordance with the stop of the filtration operation. Therefore, when the suction pump Pv is stopped, the flow of the filtered water is surely stopped. Here, when the suction pump Pv is activated, the flow path of the intake / exhaust means 27 is changed from the intake side to the exhaust side based on the pressure change due to the drive of the suction pump Pv, and is accumulated in the drain line 26. Air is discharged into the atmosphere, and the drive of the suction pump Pv is maintained.

It is explanatory drawing which shows schematic structure of the filtered water collection | recovery apparatus applied to the membrane separation activated sludge process which is typical embodiment of this invention. FIG. 3 is a three-dimensional view showing the entire configuration of a normal membrane filtration unit with a part broken away. It is a perspective view which shows typically the structural example of the membrane element which is a structural member of a hollow fiber membrane module. It is a three-dimensional view of the diffuser which is one of the structural members of the membrane filtration unit.

Explanation of symbols

4 Aeration tank 5 Membrane filtration unit 9 Hollow fiber membrane module 10 Hollow fiber membrane element 10a Porous hollow fiber 11 Membrane sheet 11a Potting material 12 Filtrated water discharge pipe 12a Filtered water discharge port 12b L-shaped joint 13 Lower frame 14 Vertical rod 15 Air diffuser 16 Air introduction pipe (branch line)
17 Aeration pipe 18 Air main pipe 20 Upper wall material 21 Water collection header pipe 21a Water collection port 21b L-shaped joint 21c Water intake port 22 Suction pipe 22a Branch pipe 23 Flow rate adjusting valve 24 Lower wall material 24a Strut 26 Drainage pipe 27 Suction Exhaust means Pv Suction pump B Aeration blower

Claims (3)

A membrane filtration unit equipped with a diffuser is placed under the membrane separation module in the treatment tank, and at the same time as the diffuser by the diffuser, the solid-liquid mixed treatment liquid is separated into solid and liquid by the membrane separation module. A solid-liquid mixed treatment liquid filtrate collecting device for sucking and collecting the filtrate from the membrane separation module via a filtrate suction line rising above the liquid level of the gas-liquid mixed treatment liquid;
A suction pump connected to the suction line is located outside the treatment tank and below the liquid level;
A drainage line connected to the liquid discharge port of the suction pump rises above the liquid level and then bends and extends downward to be connected to a liquid discharge port located below the liquid level. ,
Intake and exhaust means are arranged at the top of the drainage pipe line,
An apparatus for recovering a filtrate of a solid-liquid mixed processing solution.   The filtrate recovery apparatus according to claim 1, wherein the intake / exhaust means is a shuttle valve.   The filtrate recovery apparatus according to claim 1, wherein the intake / exhaust means is a quick exhaust valve.

Images