JP5456238B2 - Membrane separator - Google Patents

Description

The present invention relates to a membrane separation apparatus.

  2. Description of the Related Art Conventionally, a membrane separation activated sludge method in which a biological reaction tank that performs biological treatment using microorganisms and a membrane separation device that is a physicochemical treatment is combined is known. In the membrane separation apparatus of this membrane separation activated sludge method, it is common to immerse a membrane filtration unit having a plurality of filtration functions such as a hollow fiber membrane and a flat membrane in a biological reaction tank. The treated water is obtained by separating impurities represented by activated sludge in the biological reaction tank with a membrane by suction filtration that operates a suction pump connected to the membrane filtration unit. When such a submerged membrane filtration unit is used, there is a so-called membrane fouling in which suspended substances and dissolved substances contained in activated sludge are deposited / adsorbed on the membrane surface during suction to reduce the water permeability of the membrane. It is known to progress over time. Therefore, an operation that suppresses the progress of membrane fouling is usually performed by disposing an air diffuser below the membrane filtration unit, performing air scrubbing (bubbling) cleaning of the membrane with bubbles released from the air diffuser. (For example, refer to Patent Document 1).

By the way, in the above-mentioned membrane separation device, when the suction filtration by the suction pump is always performed, the tendency of the progress of the membrane fouling to be increased is observed, and as a result, complicated membrane cleaning using a chemical solution must be performed frequently. Don't be. Therefore, when performing suction filtration with a membrane separator as shown in FIG. 4, intermittent operation is performed in which the operation and stop of the suction pump are repeated every predetermined time. In this operation, it is known that when the suction pump is stopped, the membrane is cleaned by air scrubbing, so that the progress of membrane fouling can be suppressed (for example, see Non-Patent Document 1).
JP 2004-305895 A Yamamoto et al., Direct solid-liquid separation using hollow fiber membrane in an activated sludge aeration tank, Water Science and Technology, Vol.21, pp.43-53, 1989.

  However, if such intermittent operation of the suction pump is frequently performed, a large load is applied to the seal member, the motor, and the like constituting the suction pump, particularly at the time of starting. For this reason, if the operation that frequently repeats the operation / stop of the large-sized suction pump is performed, there is a possibility that the suction pump may break down.

Therefore, in the present invention, as much as possible reduce the number of starts of the suction while the suction pump was maintained in the stopped state for each predetermined time in suction filtration by membrane separation device, a membrane separation equipment capable of reducing the failure frequency of the suction pump It is to provide.

In order to solve the above problems, the invention described in claim 1 is directed to a separation tank (for example, a membrane filtration unit in the embodiment) in a water tank (for example, an aeration tank 5 in the embodiment) filled with a liquid to be treated. 8) is immersed, and the liquid to be treated is solid-liquid separated by sucking the liquid to be treated with a suction pump (for example, the suction pump Pv in the embodiment) connected to the separation membrane, and treated water is obtained. In the obtained membrane separation device, a circulation line (for example, the circulation line 13 in the embodiment) for returning the treated water discharged from the outlet side line of the suction pump to the inlet side line of the suction pump is provided. A valve body that switches the supply of treated water from the separation membrane to the suction pump and the supply of treated water from the circulation pipe to the inlet side pipe, and a valve body that switches between discharge and circulation to the outlet side pipe (for example, an embodiment) Three-way valve 14 in Characterized in that a 15).
According to a second aspect of the present invention, in the first aspect of the present invention, the supply of the treated water from the separation membrane to the suction pump and the treated water supply from the circulation line provided in the inlet side pipe are switched. Both the valve body and the valve body provided in the outlet side pipe and switching between discharge and circulation are three-way valves.

According to a third aspect of the invention, the separation membrane is immersed in a water tank filled with the treatment liquid, and the treatment liquid is fixed by sucking the treatment liquid with a suction pump connected to the separation membrane. In a membrane separation apparatus for obtaining treated water by liquid separation, a circulation pipe that connects a treated water tank for storing treated water and an inlet-side pipe of the suction pump is provided, and the inlet-side pipe is separated into the suction pump. A valve body is provided for switching between the treated water supply from the membrane and the treated water supply from the circulation pipe .

The invention described in claim 4 is the invention described in claim 3, wherein the supply of treated water from the separation membrane to the suction pump and the supply of treated water from the circulation pipe are provided in the inlet side pipe. The switching valve body is a three-way valve.
The invention described in claim 5 is the invention described in any one of claims 1 to 4, characterized in that the amount of treated water by the separation membrane is 1000 m ³ / day or more.

  According to the present invention, the treated water discharged from the suction pump is intermittently returned to the inlet side of the suction pump, so that the treated water circulates between the inlet side and the outlet side of the suction pump. Suction filtration by the separation membrane can be stopped only while the treated water is circulating. Therefore, the suction filtration by the separation membrane can be stopped while maintaining the state in which the suction pump is operated. As a result, the suction pump is not frequently started during operation, and the load on the suction pump can be greatly reduced, so that the failure frequency of the suction pump can be greatly reduced.

  Furthermore, according to the present invention, a valve body provided in the inlet side and outlet side pipes of the suction pump, and a valve body provided in the outlet side pipe line for shutting off the pipe connected to the separation membrane in the inlet pipe line. By switching control of each, the treated water discharged from the suction pump to the outlet side pipe is returned to the inlet side pipe through the circulation pipe, and the suction pump, outlet side pipe, circulation pipe and inlet Since the liquid can be fed in the order of the side pipe lines, the suction filtration by the separation membrane can be stopped without stopping the suction pump. Accordingly, since the suction pump is not frequently started during operation, the load on the suction pump can be greatly reduced, and the failure frequency of the suction pump can be greatly reduced.

In particular, when the amount of water treated by the separation membrane is relatively large, such as 1000 m ³ / day or more, a large suction pump is required, and the suction pump is started from a stopped state to return to steady operation. Although it took time to do so, the suction pump was not stopped, so it was possible to quickly return to the suction filtration at a steady flow rate from the suction filtration stopped state, rather than starting and stopping the suction pump. The efficiency of the processing system can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, the code | symbol 1 has shown the membrane separation activated sludge processing apparatus. This membrane separation activated sludge treatment device 1 is a device that discharges pollutants contained in industrial wastewater, domestic wastewater, etc. as treated water by biological treatment (details will be described later) and solid-liquid separation by membrane, and has a capacity of 1000 m ³ / It is possible to perform processing for more than a day. The membrane separation activated sludge treatment apparatus 1 includes a raw water adjustment tank 2 for storing raw water, and the raw water is sequentially fed from the outside of the membrane separation activated sludge treatment apparatus 1 to the raw water adjustment tank 2. . The raw water adjustment tank 2 can adjust the amount of raw water sent to the membrane-separated activated sludge treatment apparatus 1, and is composed of a liquid level measuring instrument (not shown) for the level of the raw water.

  In addition, an oxygen-free tank 4 is connected to the raw water adjustment tank 2 via a pipe 3, and the raw water stored in the raw water adjustment tank 2 in the middle of the pipe 3 is sent to the oxygen-free tank 4. One liquid feed pump P1 and a fine screen s for removing a relatively large solid content in the raw water are interposed. That is, based on the measurement result of the liquid level measuring instrument described above, the liquid level of the raw water adjustment tank 2 is adjusted within a predetermined range by intermittently operating the first liquid feed pump P1 provided in the pipe 3. It is supposed to be. And the raw | natural water sent with the said 1st liquid feeding pump P1 will be introduce | transduced into the anoxic tank 4 after passing the fine screen s.

  The anoxic tank 4 is a tank that performs a so-called denitrification reaction for removing nitrogen contained in the raw water. The anaerobic tank 4 is connected to the aeration tank 5 through two paths, and the raw water can be circulated between the anoxic tank 4 and the aeration tank 5 through the two paths. Here, a stirrer M driven by a motor or the like is provided in the anoxic tank 4, and the sludge concentration in the anoxic tank 4 is reduced by this stirrer M so as not to mix oxygen in the atmosphere as much as possible. Stir as much as possible in the depth direction.

  A second liquid feed pump P2 is provided in the middle of the path for returning the raw water from the aeration tank 5 to the anoxic tank 4, and there is no activated sludge in the aeration tank 5 by the second liquid feed pump P2. The solution is sent to the oxygen tank 4. The activated sludge sent from the raw water adjustment tank 2 or the aeration tank 5 to the oxygen-free tank 4 overflows from the oxygen-free tank 4 and the overflowed activated sludge flows into the aeration tank 5. .

  The aeration tank 5 is a tank in which the pollutant present in the activated sludge is rendered harmless by a biological reaction using oxygen, and so-called air is fed into the activated sludge to bring the activated sludge into contact with oxygen in the air. It is configured to do aeration. More specifically, an air diffuser 6 for supplying air into the activated sludge is installed inside the aeration tank 5, and the air diffuser 6 from the blower (B) 7 provided outside the tank. The air sent to is turned into bubbles from the air diffuser 6 and supplied into the activated sludge.

  Further, the aeration tank 5 is immersed in a membrane filtration unit 8 that separates activated sludge and treated water into solid and liquid by a membrane (not shown). The membrane outlet side of the membrane filtration unit 8 is connected to a suction line 9 in which a suction pump Pv is inserted. The membrane filtration unit 8 activates activated sludge and treated water by operating the suction pump Pv. The activated sludge stays in the aeration tank 5 and only the treated water is sent to the treated water tank 10 through the suction line 9.

  Also, the aeration tank 5 is a sludge storage tank (not shown) for storing the solid content of activated sludge grown by aeration, which has settled to the bottom of the tank by its own weight, with the third liquid feeding pump P3. Connected). A part of the activated sludge inside the aeration tank 5 is returned to the anoxic tank 4 by the second liquid feeding pump P2.

  The membrane filtration unit 8 described above includes, for example, a hollow fiber membrane module 11 in which a plurality of hollow fiber membrane elements (not shown) in which the length direction of the hollow fiber membrane is arranged in the vertical direction are supported and fixed in parallel. The air diffuser 12 is disposed below the hollow fiber membrane module 11 at a predetermined interval and cleans the membrane of the hollow fiber membrane module 11 by air scrubbing.

  The air blower 7 that supplies air to the aeration tank 5 is connected to the air diffuser 12, and the air scrubbing is performed by releasing the air supplied from the blower 7 from the air diffuser 12. Is called. The membrane is cleaned by air scrubbing by peeling due to the upward flow generated by the bubbles released from the air diffuser 12 rising in the activated sludge, and by the elastic force acting when the bubbles contact the membrane. The hollow fiber membrane element constituting the hollow fiber membrane module 11 has a hollow fiber membrane sheet in which a plurality of porous hollow fiber membranes are arranged in parallel and the open end of the hollow fiber membrane sheet is treated with water such as urethane resin. It is supported in communication with the take-out pipe and fixedly supported by the filtered water take-out pipe and the lower frame.

Next, the process by the membrane separation activated sludge treatment apparatus 1 will be specifically described.
The raw water introduced into the raw water adjustment tank 2 is biologically rendered harmless by activated sludge in the anoxic tank 4 and the aeration tank 5. Nitrogen is removed by a so-called nitrification denitrification reaction by circulating sludge between the anoxic tank 4 and the aeration tank 5. Organic substances typified by biochemical oxygen demand (BOD) are mainly air released from the air diffuser 6 which is an aeration apparatus disposed in the aeration tank 5 and the air diffuser 12 of the membrane filtration unit 8. And aerobically oxidatively decomposed.

  Moreover, some organic nitrogen compounds present in the wastewater are assimilated into bacteria as a nutrient source. Furthermore, inorganic nitrogen compounds are oxidized to nitrous acid and nitric acid by autotrophic ammonia-oxidizing bacteria and nitrite-oxidizing bacteria under aerobic conditions with a high dissolved oxygen concentration. On the other hand, under oxygen-free and anaerobic conditions without oxygen, denitrifying bacteria use nitric acid instead of oxygen to breathe, and in this process, nitrogen gas is released into the atmosphere. This oxidation-reduction reaction of nitrogen is referred to as the nitrification denitrification reaction.

  The circulation of activated sludge between the anaerobic tank 4 and the aeration tank 5 is not necessarily limited from which tank the liquid is fed using the pump, but in this embodiment, the second liquid feed pump P2 is used. The liquid is fed from the aeration tank 5 to the anaerobic tank 4, overflows from the anoxic tank 4 and flows into the aeration tank 5.

  The flow of the activated sludge in the aeration tank 5 is mainly caused by the rising of bubbles from the air diffuser 12 in the aerated portion by the membrane filtration unit 8 and the activated sludge is lowered in the portion not aerated. As a result, the whole is uniformly stirred.

  By the way, in the membrane separation activated sludge treatment apparatus 1, when the membrane filtration unit 8 performs membrane scrubbing by air scrubbing, it is preferable to stop the suction of the liquid to be treated in order to suppress the progress of membrane fouling. . On the other hand, if the ON / OFF of the suction pump Pv is frequently repeated, a load is applied to the suction pump Pv, causing a failure of the suction pump. Therefore, in this embodiment, the suction of the liquid to be processed in the aeration tank 5 through the membrane filtration unit 8 is stopped without repeating the ON / OFF of the suction pump Pv. Details will be described below.

  The suction pipe 9 of the membrane separation activated sludge treatment apparatus 1 described above is the inlet side of the suction pump Pv inserted in the suction pipe 9, that is, the inlet side suction pipe connecting the suction pump Pv and the membrane filtration unit 8. 9 a and the outlet side of the suction pump Pv, that is, the outlet side suction pipe 9 b that connects the suction pump Pv and the treated water tank 10. The suction line 9 is connected to a circulation line 13 that branches from the outlet side suction pipe 9b and joins the inlet side suction pipe 9a. Further, the circulation line 13 and the inlet side suction pipe 9a are connected. A three-way valve 14 is provided at the joining portion. Further, a valve 15 is provided between the circulation line and the outlet side suction pipe 9b.

The three-way valve 14 and the valve 15 are so-called electromagnetic valve bodies. The three-way valve 14 has a valve position A for holding a flow path (indicated by an arrow A in the figure) from the membrane filtration unit 8 to the suction pump Pv based on a control command from the control unit 20, and a suction pump from the circulation line 13. A valve position B that holds a flow path to Pv (indicated by an arrow B in the figure) is configured to be switchable.
The valve 15 is controlled to open and close based on a control command from the control unit 20.

  The control unit 20 includes an input result to an operation unit (not shown) connected to the control unit 20, a detection result of various sensors (not shown) such as a level meter for measuring the liquid level, and a memory or the like in advance. The first liquid pump P1, the second liquid pump P2, the agitator M, the blower 7, the third liquid pump P3, the suction pump Pv, the three-way valve 14 and the The operation of the valve 15 and the like is controlled. In particular, the three-way valve 14 and the valve 15 are set to perform switching of the valve position and control of opening and closing every predetermined time, that is, intermittently. In addition, the said operation part is provided on the control box which is not shown in figure, for example.

Next, a control example of the suction pump Pv, the three-way valve 14 and the valve 15 by the control unit 20 will be described based on the timing chart of FIG.
First, when a starting operation is performed at time t0, the control unit 20 controls the suction pump Pv to be ON, and at the same time holds the three-way valve 14 at the valve position A that serves as a flow path from the membrane filtration unit 8 to the suction pump Pv. At the same time, the valve 15 is opened. At this time, the flow rate of the processing water that is suction filtered from the aeration tank 5 through the membrane filtration unit 8, that is, the processing flow rate becomes the predetermined flow rate a. The predetermined flow rate a is a flow rate set in advance in consideration of the performance of the suction pump Pv, the membrane area of the membrane filtration unit 8, the inner diameter of the suction conduit 9, and the like.

  At time t1 when a predetermined time has elapsed from time t0, the three-way valve 14 is switched from the valve position A to the valve position B and the valve 15 is closed. At this time, the ON state of the suction pump Pv is kept, and the treated water is circulated through the circulation line 13. More specifically, the treated water discharged by the suction pump Pv returns to the inlet side of the suction pump Pv via the circulation line 13, and is again sucked by the suction pump Pv and discharged to the outlet side. Here, the treated water returned to the inlet side of the suction pump Pv by the circulation line 13 does not flow into the membrane filtration unit 8 side, and when the three-way valve 14 reaches the valve position B, the suction filtration is stopped. The processing flow rate becomes zero.

  Next, at time t2 when a predetermined time has elapsed from time t1, the three-way valve 14 is returned from the valve position B to the valve position A and the valve 15 is opened. Then, the suction filtration is resumed, the processing flow rate returns from 0 to the predetermined flow rate a again, and this state is maintained for a predetermined time. Thereafter, similarly to time t1, at time t3, the three-way valve 14 is switched again from the valve position A to the valve position B and the valve 15 is closed to stop the suction filtration. Further, after a predetermined time, similarly to the time t2, At time t4, the three-way valve 14 is switched from the valve position B to the valve position A, and the valve 15 is opened to resume suction filtration. Thereafter, the controller 20 intermittently repeats switching of the positions A and B of the three-way valve and the opening and closing of the valve 15 every predetermined time, in the same manner as in the above processing.

  Here, the time from the time t0 to the time t1 when the position A of the three-way valve and the opening of the valve 15 are maintained and the time from the time t2 to the time t3 are set to the same time, and similarly the three-way valve The time from the time t1 to the time t2 when the position B and the valve 15 are kept closed and the time from the time t3 to the time t4 are also set to the same time. The time for maintaining the position A of the three-way valve and the opening of the valve 15 is set sufficiently longer than the time for maintaining the position B of the three-way valve and the closing of the valve 15. That is, the control unit 20 returns the treated water discharged from the suction pump Pv intermittently from the position A of the three-way valve performing the suction filtration and the opening of the valve 15 to the input side of the suction pump Pv and stops the suction filtration. The three-way valve position B and the valve 15 are closed.

  Therefore, according to the above-described embodiment, the treated water discharged from the suction pump Pv is intermittently returned to the input side of the suction pump Pv, so that the inlet side and the outlet side of the suction pump Pv are intermittently provided. , The suction filtration by the membrane filtration unit 8 can be stopped only while the treated water is circulating. As a result, the membrane filtration unit 8 can be stopped without stopping the suction pump Pv. Can be stopped, the frequency of starting the suction pump Pv can be suppressed to reduce the load on the suction pump Pv, and the failure frequency of the suction pump can be greatly reduced.

In particular, when the amount of treated water in the membrane separation activated sludge treatment apparatus 1 is 1000 m ³ / day or more, it is possible to quickly switch by opening and closing the three-way valve 14 and the valve 15 without stopping the suction pump Pv. Efficiency can be improved.

  By the way, in embodiment mentioned above, although it comprised so that the circulation line 13 might branch from the exit side suction line 9b, as shown in FIG. 3, as shown in FIG. 3, the edge part of the circulation line 13a is comprised. The opening may be arranged in the treated water tank 10.

  Further, as another aspect of this modified example, as shown in FIG. 5, the outlet end of the circulation pipe 13 b is branched and connected to the outlet pipe 18 that discharges the treated water from the treated water tank 10, and the outlet pipe The valve 16 is provided in the discharge pipe 18 on the discharge side of the branch point between the pipe 18 and the circulation pipe 13b, the valve 17 is provided in the circulation pipe 13b, and the valves 16 and 17 are opened and closed to control the discharge (valve 16 may be switched between opening (opening 16 and closing valve 17) and circulation (closing valve 16 and opening valve 17). In the modification shown in FIGS. 3 and 5 and other aspects of this modification, the same reference numerals are given to the same aspects as those in the above-described embodiment, and the description thereof is omitted.

  With this configuration, the treated water discharged from the suction pump Pv can be returned to the inlet side of the suction pump Pv, and suction filtration can be performed without stopping the suction pump Pv, as in the above-described embodiment. Can be stopped.

  In the above-described embodiment and its modifications, the single membrane separation unit 8 is connected to the set of suction lines 9, the suction pump Pv, and the circulation lines 13, 13. A plurality of membrane separation units 8 may be connected by branching from the middle of the inlet side suction pipe 9 a of the suction pipe 9.

It is a schematic block diagram of the membrane separation activated sludge processing apparatus in embodiment of this invention. It is a timing chart which shows ON / OFF of the suction pump in embodiment of this invention, the amount of treated water, and the valve position of a three-way valve, respectively. It is a schematic block diagram of the membrane separation activated sludge processing apparatus of the modification of embodiment of this invention. 3 is a timing chart corresponding to FIG. 2 in a conventional membrane separation activated sludge treatment apparatus. It is a schematic block diagram of the membrane separation activated sludge processing apparatus in the other aspect of embodiment of this invention.

Explanation of symbols

5 Aeration tank (treatment tank)
8 Membrane filtration unit (separation membrane)
9 Suction line (pipe)
9a Inlet side suction piping (inlet side pipe line)
9b Outlet side suction piping (outlet side suction pipe)
13 Circulation line 14 Three-way valve (valve)
15 Valve (Valve)
Pv suction pump

Claims (5)

A membrane in which a separation membrane is immersed in a water tank filled with the liquid to be treated, and the liquid to be treated is solid-liquid separated by sucking the liquid to be treated with a suction pump connected to the separation membrane to obtain treated water In the separation device,
Providing a circulation line for returning the treated water discharged from the outlet side line of the suction pump to the inlet side line of the suction pump;
The inlet side pipe line is provided with a valve body for switching the treated water supply from the separation membrane to the suction pump and the treated water supply from the circulation pipe line, and the valve body for switching the discharge and circulation to the outlet side pipe line. Membrane separator.   A valve body that is provided in the inlet side pipe and switches between supply of treated water from the separation membrane to the suction pump and treated water from the circulation pipe, and discharge and circulation provided in the outlet side pipe. The membrane separator according to claim 1, wherein each of the switching valve bodies is a three-way valve. A membrane in which a separation membrane is immersed in a water tank filled with the liquid to be treated, and the liquid to be treated is solid-liquid separated by sucking the liquid to be treated with a suction pump connected to the separation membrane to obtain treated water In the separation device,
A circulation pipe connecting the treated water tank for storing treated water and the inlet side pipe of the suction pump is provided, and the inlet side pipe is supplied with treated water from the separation membrane to the suction pump and from the circulation pipe. A membrane separation apparatus provided with a valve body that switches between treated water supply . The membrane separator according to claim 3, wherein the valve body provided in the inlet side pipe and switching between the treated water supply from the separation membrane to the suction pump and the treated water supply from the circulation pipe is a three-way valve. The membrane separation apparatus according to any one of claims 1 to 4, wherein the amount of treated water by the separation membrane is 1000 m ³ / day or more.

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