JP2008168219A - Membrane separation type activated sludge treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane separation type activated sludge treatment apparatus reduced in load to a membrane separation unit while suppressing increase of the number of parts. <P>SOLUTION: The membrane separation type activated sludge treatment apparatus is provided with the membrane separation unit separating solid from liquid of raw water when sending out raw water in an aeration tank 4, an air diffuser 15 discharging air supplied from a blower 20 driven by a motor 24 as bubbles into the raw water to clean the membrane surface of the membrane separation unit 5, and a current sensor 32 detecting the load of the motor 24. When the load of the motor 24 is determined lower than a given load based on a detection result of the current sensor 32, sending of the raw water is stopped. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a membrane separation activated sludge treatment apparatus.

  2. Description of the Related Art Conventionally, a membrane separation activated sludge treatment apparatus that performs water treatment such as sewerage treatment or industrial wastewater treatment is known. In this membrane separation activated sludge treatment apparatus, treated water is obtained by immersing a membrane separation unit having a plurality of filters such as hollow fiber membranes in the treatment tank, and separating and removing impurities in the raw water in the treatment tank via the membrane separation unit. Is led out of the treatment tank via the treated water lead-out pipeline. In addition, when this membrane separation unit is used, so-called membrane fouling such as clogging of suspended substances or organic substances contained in the raw water adhering to the temporary side of the filter occurs. Air is sent to the diffuser below the unit, and the film is bubble-washed by fine bubbles released from the diffuser.

  In general, a blower composed of a fan and a motor sends air to the diffuser in the processing tank to release air bubbles. For example, for some reason, the motor load increases and the drive current increases. In such an abnormal state, it is determined that the bubbling cleaning cannot be normally performed, and the pump connected to the membrane separation unit is stopped along with the driving of the motor. However, for example, if the fan belt that transmits the driving force from the blower motor to the fan comes off or breaks and the motor power is not transmitted to the fan, the motor continues to rotate normally, but air is sent to the diffuser. It disappears and bubbling cleaning is not performed. For this reason, if the treated water continues to flow through the treated water outlet conduit, fouling of the membrane proceeds and there is a possibility that the burden on the membrane separation unit increases.

Therefore, in recent years, in order to reduce the burden on the membrane separation unit, a pressure receiving part that operates the valve body in the opening direction in response to the pressure on the discharge side of the blower is provided in the treated water outlet pipe, There has been proposed a membrane separation activated sludge treatment apparatus that opens a valve body and allows treated water to flow through a treated water outlet pipe only when a predetermined pressure is applied to the pressure receiving portion (for example, Patent Document 1). reference).
JP 2004-305895 A

  However, in the above-described membrane separation activated sludge treatment apparatus, it is necessary to provide a pipe branching from the discharge side of the blower to the pressure receiving part provided in the treated water outlet pipe. There is a problem that it becomes complicated.

  Therefore, the present invention provides a membrane separation activated sludge treatment apparatus capable of reducing the burden on the membrane separation unit while suppressing an increase in the number of parts.

  In order to solve the above-mentioned problem, the invention described in claim 1 performs solid-liquid separation of the raw water when the raw water in the treatment tank (for example, the aeration tank 4 in the embodiment) is sent out of the tank. Supplying from air supply means (for example, the blower 20 in the embodiment) including a membrane separation means (for example, the membrane filtration unit 5 in the embodiment) and using a motor (for example, the motor 24 in the embodiment) as a drive source In the membrane separation activated sludge treatment apparatus provided with aeration means (for example, aeration generation apparatus 15 in the embodiment) for discharging the air to be discharged as bubbles in the raw water and cleaning the membrane surface of the membrane separation means, Load detecting means for detecting the load of the motor (for example, the current sensor 32 in the embodiment) is provided, and the load of the motor is lower than a predetermined load based on the detection result of the load detecting means. If it is determined that, characterized in that stopping the transmission of the raw water.

  The invention described in claim 2 includes a current sensor (for example, the current sensor 32 in the embodiment) that detects a current value of the motor, and determines a load of the motor based on a detection result of the current sensor. It is characterized by.

  According to the first aspect of the present invention, since the load detection means can detect a decrease in the motor load, when the motor load becomes lower than a predetermined load, the load detection means is connected to the motor of the air supply means. For example, since it can be determined that the fan belt is in an abnormal state where it is detached or broken, it is possible to stop the raw water in the treatment tank from being fed out of the tank. Therefore, it is possible to prevent the raw water from being sent out without the membrane being cleaned by the air diffuser, and membrane separation while reducing the number of parts as compared with the case of adding a pipeline as in the past. There is an effect that the fouling progress of the means can be suppressed.

  According to the second aspect of the present invention, the current value of the motor can be detected by the current sensor, and the load of the motor can be determined based on the detection result of the current sensor. An abnormal state of the fan belt can be detected by effectively using a current sensor provided in the motor for monitoring. Therefore, there is an effect that it is possible to detect a decrease in motor load without increasing the number of parts.

Hereinafter, an example of a membrane separation activated sludge treatment apparatus in an embodiment of the present invention will be described based on the drawings.
As shown in FIG. 1, the membrane separation activated sludge treatment apparatus of this embodiment includes a fine screen 1 that removes a relatively large solid content in the waste water, and the waste water that has passed through the fine screen 1. Is introduced into the raw water adjustment tank 2.

  The raw water adjustment tank 2 stores the wastewater that has passed through the fine screen 1, and the drainage liquid level can be measured by a liquid level measuring instrument (not shown). Based on this measurement result, the liquid level height in the raw water adjustment tank 2 is adjusted within a predetermined range by intermittently operating the first liquid feed pump P1 provided in the outlet pipe of the raw water adjustment tank 2. It is configured.

  In addition, an oxygen-free tank 3 is connected to the raw water adjustment tank 2 through an outlet pipe. The oxygen-free tank 3 performs a so-called denitrification reaction, and the raw water in the oxygen-free tank 3 can be circulated with an aeration tank (treatment tank) 4 that performs an oxidation reaction by aeration. Yes. Here, the raw water sent from the raw water adjustment tank 2 to the anoxic tank 3 by the first liquid feed pump P 1 overflows from the anoxic tank 3, and the overflowed raw water flows into the aeration tank 4.

  In the aeration tank 4, a large number of membrane filtration units (membrane separation means) 5 are immersed, and the membrane filtration unit 5 separates solid and liquid into solids such as suspended substances and organic substances contained in raw water and treated water. . A pipe line 22a is connected to each of the membrane filtration units 5, and the pipe lines 22a are connected to the suction pipe line 22 in which a suction pump Pv is interposed, respectively, and the suction pump (P) Pv is operated for suction. By doing so, raw water is separated into activated sludge and treated water by the membrane filtration unit 5. Note that an opening / closing valve 23 is interposed in each pipe line 22a.

  In addition, a sludge storage tank 7 is connected to the aeration tank 4. The sludge storage tank 7 is configured to store a solid content of sludge that has been aerated in the aeration tank 4 and has grown to its bottom by its own weight. Furthermore, the aeration tank 4 is connected to a treated water tank 8 for temporarily storing treated water obtained by solid-liquid separation in the membrane filtration unit 5, and the treated water stored in the treated water tank 8 is stored in the aerated tank 4. The water is appropriately drained through the outlet pipe. A part of the sludge in the aeration tank 4 is returned to the anoxic tank 3 by the second liquid feed pump P2 and circulated.

  The membrane filtration unit 5 includes a hollow fiber membrane module 9 in which a plurality of hollow fiber membrane elements (not shown) arranged in parallel in the vertical direction in the length direction of the hollow fiber membrane are supported and fixed, and the hollow fiber An aeration generating device (aeration means) 15 is disposed below the membrane module 9 at a required interval and cleans the membrane of the hollow fiber membrane module 9 by air scrubbing (or bubbling). The hollow fiber membrane element constituting the hollow fiber membrane module 9 has a treated water take-off pipe through a potting material at the upper end opening end of a hollow fiber membrane sheet in which a large number of porous hollow fiber membranes are arranged in parallel. And fixedly supported by a filtered water discharge pipe and a lower frame.

  According to this membrane separation activated sludge treatment apparatus, raw water is biologically purified by activated sludge in the anoxic tank 3 and the aeration tank 4. Nitrogen is removed by a so-called nitrification denitrification reaction by circulating sludge between the anoxic tank 3 and the aeration tank 4. The organic matter converted into the biochemical oxygen demand (BOD) is aerobic by the air discharged from the diffuser generator 15 of the membrane filtration unit 5 which is mainly an aeration apparatus disposed in the aeration tank 4. It is oxidized and decomposed. The removal of phosphorus is performed by being taken into the body of the microorganism as polyphosphoric acid by the action of microorganisms (phosphorus-accumulating bacteria) in the sludge. This microorganism takes up phosphorus in an aerobic state and releases phosphorus stored in the body in an anaerobic state. When phosphorus-accumulating bacteria are repeatedly exposed to anaerobic and aerobic conditions, they absorb more phosphorus than the amount of phosphorus released in anaerobic conditions.

  In addition, some of the nitrogen compounds such as biological excrement and carcasses are assimilated into plants and bacteria as fertilizer. Some of these nitrogen compounds are oxidized to nitrous acid and nitric acid by autotrophic ammonia recently and independent nitrite-oxidizing bacteria under aerobic conditions rich in oxygen. On the other hand, under anaerobic conditions without oxygen, microorganisms called denitrifying bacteria produce nitrous acid from nitric acid instead of oxygen, and further reduce to dinitrogen monoxide and nitrogen gas. This reduction reaction is referred to as the nitrification denitrification reaction.

  The circulation of sludge between the anaerobic tank 3 and the aeration tank 4 is not necessarily limited from which tank the liquid is fed using the pump, but normally the aeration tank using the second liquid feeding pump P2. The liquid is fed from 4 to the anaerobic tank 3 and is allowed to flow from the anoxic tank 3 into the aeration tank 4 by overflow. Here, the dissolved organic matter concentration (hereinafter referred to as DOC) in the portion where the circulating fluid from the aeration tank 4 enters the anoxic tank 3 is 0.2 mg / L or less, and the portion where the circulating fluid is taken out from the aeration tank 4 It is preferable that the DOC is at least one of 0.5 mg / L or less because of stabilization. In addition, the measurement of DOC can be measured using the normal DO meter by the diaphragm electrode method.

  In order to set the DOC of the portion 6 where the circulating fluid from the aeration tank 4 is taken out to 0.5 mg / L or less, the portion where the sludge is taken out from the aeration tank 4 to the anoxic tank 3 can be a sludge retention part. preferable. The sludge retention part means a part that is not easily affected by sludge flow caused by aeration. For example, if a space is provided between the membrane filtration unit 5 and the bottom of the aeration tank 4, the sludge present in the lower part of the membrane filtration unit 5 is not well agitated and becomes a staying portion.

  Therefore, as shown in FIG. 1, the DOC of the portion 6 where the circulating fluid is extracted from the aeration tank 4 can be reduced to 0.5 mg / L or less by removing the sludge from below the position of the membrane filtration unit 5. . When a plurality of membrane filtration units 5 are arranged in parallel in the aeration tank 4, the portion 6 from which the circulating fluid is taken out is located below the air diffuser 15. Further, it is preferable that the part from which the sludge is taken out from the membrane filtration unit 5 is separated downward by 20 cm or more, more preferably 30 cm or more.

  The flow of sludge in the aeration tank 4 is mainly due to the rise of air bubbles from the air outlet at the aeration part by the membrane filtration unit 5, and the sludge descends at the part not aerated. Thereby, the whole is stirred. At this time, if the oxygen utilization rate of the sludge in the aeration tank 4 is kept high, oxygen is rapidly consumed in the non-aerated area, so that it is easy to form a part where the dissolved oxygen in the aeration tank 4 becomes low. Become. Here, the oxygen utilization rate of the sludge in the aeration tank 4 refers to the oxygen utilization rate of the sludge taken from the aerated portion of the aeration tank 4, and the measuring method is a sewer test method (1997, corporation). It can be determined according to the Japan Sewerage Association.

  Incidentally, as shown in FIG. 2, a blower (B; air supply means) 20 is connected to an air diffuser 15 of the membrane filtration unit 5 immersed in the aeration tank 4 through an air supply pipe 18. . The blower 20 includes a fan (F) 21 that sends out air and a motor (M) 24 that drives the fan 21. More specifically, the fan belt 27 is wound around the pulley 25 provided at the shaft end of the driven shaft 21 a of the fan 21 and the pulley 26 provided at the shaft end of the drive shaft 24 a of the motor 24. The rotation of the drive shaft 24 a of the motor 24 is transmitted to the driven shaft 21 a of the fan 21 via the fan belt 27. The motor 24 is connected to a driver (D) 31 that receives a control command from the control unit 30 and controls the driving current of the motor 24, and the motor 24 is connected between the motor 24 and the driver 31. A current sensor (A; load detecting means) 32 for detecting the drive current is interposed. For convenience of illustration, the on-off valves 19 and 23 are omitted in FIG.

  The control unit 30 controls ON / OFF of the suction pump Pv connected to the outlet side of the membrane filtration unit 5 based on the detection result of the current sensor 32. More specifically, the control unit 30 detects the suction pump Pv when the load of the motor 24 decreases and the driving current of the motor 24 decreases to a predetermined value (for example, about 4 A) or less as a result of detection by the current sensor 32. Is set to stop suction of treated water. The predetermined value of the drive current is an appropriate current value that can determine a decrease in the drive current accompanying a decrease in the load on the motor 24 without hunting.

Next, the operation of the membrane separation activated sludge treatment apparatus in the above embodiment will be described.
First, when there is a start operation from the operator, the control unit 30 outputs a drive command for the motor 24 to the driver 31 of the blower 20, and as a result, the blower 20 and the suction pump Pv are started. Then, the driver 31 starts energizing the motor 24, and the drive shaft 24a of the motor 24 to which power is supplied starts to rotate. Then, the rotation of the motor 24 is transmitted to the fan 21 through the pulley 26, the fan belt 27, and the pulley 25, and air is supplied to the diffuser generator 15. Here, when air is supplied to the air diffuser 15, fine bubbles are released into the aeration tank 4 from a plurality of holes (not shown) of the air diffuser 15, and these air bubbles are subjected to membrane filtration. The outer surface of this hollow fiber membrane element is bubble-washed by raising while contacting the surface of the hollow fiber membrane element constituting the hollow fiber membrane module of unit 5.

  Further, the control unit 30 controls the suction pump Pv to be ON substantially simultaneously with the start of the blower 20. Then, the raw water in the aeration tank 4 is suction filtered by the membrane filtration unit 5, and the suction-filtered treated water is discharged to the treated water tank 8 arranged outside the aeration tank 4.

  On the other hand, the control unit 30 constantly monitors the detection result of the current sensor 32, and when the drive current of the motor 24 becomes a predetermined value or less based on the detection result of the current sensor 32, the power source of the suction pump Pv Is controlled to be turned off. Here, as a case where the drive current of the motor 24 becomes a predetermined value or less, for example, the fan belt 27 is broken due to deterioration over time, or the fan belt 27 is dropped from the pulleys 25 and 26 for some reason, and the motor 24 rotates. May not be transmitted to the fan 21, or the air supply pipe 18 may drop or break.

  More specifically, as shown in FIG. 3, when the fan belt 27 is in a normal state and the rotation of the motor 24 is transmitted to the fan 21 (the region on the left side of the arrow in FIG. 3), Since 21 is a load, the current (vertical axis in FIG. 3) detected by the current sensor 32 is a relatively high value (for example, about 10 A). On the other hand, for example, when the fan belt 27 is detached at the timing of the arrow in FIG. 3, the fan 21 serving as the load of the motor 24 is disconnected from the motor 24 and the load of the motor 24 is suddenly reduced. It will be. As the load decreases, the power consumption of the motor 24, that is, the drive current is significantly reduced (for example, up to about 3A), and the current sensor 32 detects the decrease in current. Then, the control unit 30 that has received the detection result of the current sensor 32 determines that some abnormality has occurred in the fan belt 27 and the load on the motor 24 has decreased because the drive current has dropped below a predetermined value. The suction pump Pv is stopped and controlled.

  Therefore, according to the above-described embodiment, since the load of the motor 24 can be detected by the current sensor 32, the fan belt 27 is reduced when the load of the motor 24 becomes lower than a predetermined load. Therefore, it is possible to stop the suction of the raw water in the aeration tank 4 by the suction pump Pv, and as a result, the bubbling cleaning by the air diffuser 15 can be performed. Since it is possible to prevent the suction pump Pv from continuing to be driven in a state where it is not performed, it is possible to suppress the progress of fouling of the membrane while reducing the number of parts compared to the case where the number of pipes is increased as in the prior art. . As a result, the lifetime of the film can be extended.

The present invention is not limited to the above embodiment, and for example, the fan belt 27 may be replaced with a chain and the pulleys 25 and 26 may be replaced with sprockets.
Moreover, although the said embodiment demonstrated the case where the several membrane filtration unit 5 was immersed in the aeration tank 4, what is necessary is just the aeration tank 4 in which the at least 1 membrane filtration unit 5 was immersed.

In the above embodiment, the case where the suction pump Pv is turned off when it is determined that the load of the motor 24 is reduced has been described. However, all the pumps, that is, the first liquid feeding pump P1 in the above embodiment, are described. The second liquid feed pump P2 may all be controlled to stop. Furthermore, although the case where the suction pump Pv is stopped has been described, the open / close valve 23 provided in the branch conduit 22 may be closed to stop the discharge of raw water from the aeration tank 4.
Moreover, although the process in the case of circulating raw | natural water between the aeration tank 4 and the anaerobic tank 3 was demonstrated, it is applicable if it has an aerobic processing tank in which a membrane filtration unit is immersed. it can.

It is the schematic which shows the system configuration | structure of the membrane separation activated sludge processing apparatus in embodiment of this invention. It is explanatory drawing of the aeration tank in embodiment of this invention. It is a graph which shows the change of the drive current by the load fluctuation | variation of the motor in embodiment of this invention.

Explanation of symbols

4 Aeration tank (treatment tank)
5 Membrane filtration unit (membrane separation means)
15 Air diffuser (air diffuser)
20 Blower (Air supply means)
24 motor 32 current sensor (load detection means)
Pv suction pump

Claims (2)

A membrane separation means for performing solid-liquid separation of the raw water when the raw water in the treatment tank is sent out of the tank, and air supplied from an air supply means using a motor as a drive source is released as bubbles into the raw water. In the membrane separation activated sludge treatment apparatus provided with aeration means for cleaning the membrane surface of the membrane separation means,
Load detecting means for detecting the load of the motor is provided, and when the load of the motor is determined to be lower than a predetermined load based on the detection result of the load detecting means, the sending of the raw water is stopped. A membrane separation activated sludge treatment apparatus characterized by   The load detecting means is a current sensor that detects a driving current of the motor, and stops sending the raw water when it is determined that the driving current is lower than a predetermined current value based on a detection result of the current sensor. The membrane separation activated sludge treatment apparatus according to claim 1, wherein

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