JP2010194481A - Sewage treatment apparatus and operation method of sewage treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sewage treatment apparatus which keeps DO of a membrane separation tank a suitable value, controls generation of a causative agent of membrane fouling, and further maintains denitrification reaction in an anaerobic tank and phosphorous release reaction in an aerobic tank a good state. <P>SOLUTION: The sewage treatment apparatus includes an aerobic tank 3 which has an air diffuser 5 and aerobically treats a water to be treated by a microorganism, a membrane separation tank 4 which is arranged in the latter step of the aerobic tank 3 and has a membrane separation apparatus 6 for solid-liquid separating the water to be treated, and a first circulation passage 8 for making the water to be treated in the membrane separation tank 4 circulate to the aerobic tank 3, wherein the sewage treatment apparatus includes a first measuring apparatus 20 for measuring an indicator of the aerobic treatment in the membrane separation tank 4, and a first control apparatus 21 which adjusts a circulation amount of the water to be treated through the first circulation passage 8 based on a measured value by the first measuring apparatus 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a membrane separation in which an aerobic tank provided with an air diffuser and aerobically treating water to be treated with microorganisms, and a membrane separation device disposed at a subsequent stage of the aerobic tank and separating the water to be treated solid-liquid The present invention relates to a sewage treatment apparatus including a tank and a first circulation path for circulating water to be treated in the membrane separation tank to the aerobic tank, and an operation method thereof.

  In Patent Document 1, as shown in FIG. 6, sewage is treated as an anaerobic tank, an anaerobic tank, an aerobic tank, a separation membrane as a sewage treatment apparatus that removes nitrogen, phosphorus, and the like in sewage using activated sludge. A wastewater treatment device that passes water in the order of the membrane separation tank in which the water is immersed, returns a part of the treated water of the membrane separation tank to the anaerobic tank, and returns a part of the treated water of the anoxic tank to the anaerobic tank. Proposed.

  The sewage is anaerobically treated in an anaerobic tank, the BOD component is taken into the microorganism, and the phosphorus compound is hydrolyzed to release phosphorus as normal phosphoric acid. In the anaerobic tank to which the water to be treated in the anaerobic tank is transferred, denitrification treatment, that is, reduction treatment of nitrate ions and nitrite ions to nitrogen gas is performed. Furthermore, aerobic treatment is performed in the aerobic tank to which the water to be treated in the anoxic tank has been transferred, nitrification of ammonia and uptake of normal phosphoric acid are performed by the microorganisms, and the water to be treated is transferred through the separation membrane.

  Since the water to be treated containing activated sludge is returned from the aerobic tank to the anaerobic tank, and the water to be treated is returned from the anaerobic tank to the anaerobic tank, it is denitrified in the anaerobic tank and is treated with nitric acid. The non-nitrogen and nitrite nitrogen-free treated water in which oxygen is consumed is returned to the anaerobic tank, and NO-free and oxygen-free conditions, which are phosphorus release conditions in the anaerobic tank, are maintained.

  That is, in the anaerobic tank, the phosphorus compound is efficiently released as normal phosphoric acid, and the released normal phosphoric acid is taken into the activated sludge more than released in the anaerobic tank in the subsequent aerobic tank. It becomes possible to remove phosphorus highly. The activated sludge is discharged out of the treatment system as excess sludge.

  The membrane separation device immersed in the membrane separation tank is equipped with an aeration device for cleaning the membrane surface below, but the amount of oxygen supplied from the aeration device is the activated sludge that stays in the membrane separation tank. When it is less than the amount of oxygen consumed by endogenous respiration, the dissolved oxygen concentration (DO: Dissolved Oxygen) in the membrane separation tank does not increase. Moreover, when DO runs short, what is necessary is just to increase DO supply amount from an aerobic tank to a membrane separation tank by increasing the amount of aeration of a previous aerobic tank.

JP 2001-314890 A

  However, if the DO in the membrane separation tank is too high, self-disassembly of activated sludge occurs, causing the cause of membrane fouling. When the amount of sludge circulation is increased, the residence time in the oxygen-free tank cannot be secured, and there is a possibility that the denitrification reaction may be impaired.

  Patent Document 1 also proposes an apparatus in which a membrane separation device is installed in an aerobic tank. According to this method, it is possible to appropriately adjust the DO of the aerobic tank, and thus it is possible to suppress the occurrence of a membrane fouling-causing substance. However, since the activated sludge concentration in the aerobic tank is higher than the method of installing the membrane separation apparatus in the membrane separation tank, the oxygen transfer supply performance of the aeration apparatus is reduced, and the amount of aeration required for aerobic treatment is reduced. There are increasing problems.

  The object of the present invention is to reduce the amount of air diffused in the aerobic tank while keeping the DO in the membrane separation tank at an appropriate value and suppressing the generation of causative substances of the membrane fouling in view of the above-mentioned problems, Is to provide a sewage treatment apparatus capable of maintaining a denitrification reaction in an anaerobic tank and a phosphorus release reaction in an anaerobic tank in an excellent state and an operation method thereof.

  In order to achieve the above-described object, the characteristic configuration of the sewage treatment apparatus according to the present invention is, as described in claim 1, comprising an aeration device and an aerobic tank for aerobically treating treated water with microorganisms. A membrane separation tank disposed downstream of the aerobic tank and provided with a membrane separation device for solid-liquid separation of the treated water; and a first for circulating the treated water in the membrane separation tank to the aerobic tank A sewage treatment apparatus comprising a circulation path of the first measurement device for measuring an aerobic treatment index in the membrane separation tank, and the first measurement device based on the measurement value by the first measurement device, It is in the point provided with the 1st control apparatus which adjusts the circulation amount of to-be-processed water via one circulation path.

  According to the above-described configuration, since the index of the aerobic treatment in the membrane separation tank is obtained by the first measuring device, the first control device can be removed from the membrane separation tank via the first circulation path according to the state. The amount of treated water to be circulated to the aerobic tank is adjusted to an appropriate value.

  For example, if the amount of treated water circulating through the first circulation path is increased in accordance with the rise in DO in the membrane separation tank, the amount of sludge inflow from the aerobic tank having a lower DO than the membrane separation tank is increased. In addition, the DO of the membrane separation tank decreases. Furthermore, the residence time of the sludge in the aerobic tank is shortened, the unnitrified ammonia flowing into the membrane separation tank is increased, and oxygen is consumed in the nitrification of ammonia in the membrane separation tank. The abnormal rise of DO can be effectively suppressed, and generation of substances causing membrane fouling due to self-decomposition of activated sludge can be suppressed.

  Conversely, when the DO in the membrane separation tank becomes low and the circulation rate of the treated water through the first circulation path is reduced, the inflow of sludge from the aerobic tank with a lower DO than the membrane separation tank is reduced. The DO can be adjusted to an appropriate value by the oxygen supplied from the aeration apparatus provided in the membrane separation tank.

  As described in claim 2, the second characteristic configuration includes at least one of dissolved oxygen concentration, redox potential, and nitrate nitrogen concentration by the first measuring device in addition to the first characteristic configuration described above. When one index is measured and the measured value becomes larger than a preset reference value, the first control device adjusts so as to increase the circulation amount of the water to be treated.

  The aerobic treatment index in the membrane separation tank is an index capable of evaluating the degree of aerobic treatment in the membrane separation tank, that is, the nitrification of ammonia and the uptake of orthophosphoric acid by microorganisms. Any one of oxygen concentration, oxidation-reduction potential, and nitrate nitrogen concentration may be measured. When the measured value becomes larger than a preset reference value, the first control device adjusts the amount of treated water to increase.

  When the oxidation-reduction potential (ORP) is high, it can be determined that the treated water is in a highly oxidized state of DO, and even when the nitrate nitrogen concentration is high, the nitrification reaction is significant due to the high DO. It can be judged.

  In the third feature configuration, as described in claim 3, in addition to the first feature configuration described above, at least one index of pH and ammoniacal nitrogen concentration is measured by the first measurement device. When the measured value becomes smaller than a preset reference value, the first control device adjusts so as to increase the circulation amount of the water to be treated.

  Further, at least one of pH and ammonia nitrogen concentration may be measured as an aerobic treatment index in the membrane separation tank. When the pH value becomes small or the ammoniacal nitrogen concentration becomes low, it can be determined that the nitrification reaction is proceeding under high DO. Therefore, when the measured value becomes smaller than the preset reference value, the first control device Thus, the amount of water to be treated is adjusted so as to increase.

  In the fourth feature configuration, in addition to any one of the first to third feature configurations described above, the second feature configuration measures an aerobic treatment index in the aerobic tank. And a second control device for adjusting the dissolved oxygen concentration based on the measurement value obtained by the second measurement device.

  The aerobic treatment index in the aerobic tank varies depending on the amount of treated water circulating through the first circulation path, but the second measurement device measured the aerobic treatment index in the aerobic tank. Based on this, the amount of air diffused or the oxygen transfer efficiency of the air diffuser is adjusted by the second control device, and can be adjusted to an appropriate value. As a result, the aerobic treatment index of the membrane separation tank can be adjusted more quickly. For example, if the DO in the aerobic tank rises from an appropriate value, the aeration apparatus can be adjusted so that the amount of air diffused is reduced or the oxygen transfer efficiency is reduced, so that the inside of the aerobic tank is reduced. The DO can be reduced.

  In addition to any one of the first to fourth characteristic configurations described above, the fifth characteristic configuration is an anaerobic tank in which phosphorus is released from microorganisms before the aerobic tank. And a second circulation path that circulates the water to be treated in the membrane separation tank to the oxygen-free tank, and the anaerobic water to be treated in the oxygen-free tank. It is in the point provided with the channel which transfers to a tank.

  Circulating sludge from a membrane separation tank having a high DO to an oxygen-free tank will cause problems in the denitrification / dephosphorization treatment. However, according to any one of the first to fourth features described above, the DO of the membrane separation tank Is adjusted to an appropriate value, so if the sludge in the membrane separation tank in which DO is suppressed is circulated to the oxygen-free tank, the efficiency of the denitrification process in the oxygen-free tank will increase and the denitrification process will be sufficient. The efficiency of dephosphorization treatment in the anaerobic tank is also increased by flowing the sludge in the anaerobic tank, that is, the sludge without nitrate nitrogen, into the anaerobic tank. Accordingly, a stable denitrification / dephosphorization process is performed.

  In addition to any one of the first to fourth characteristic configurations described above, the sixth characteristic configuration is an anaerobic tank that releases phosphorus from microorganisms in the front stage of the aerobic tank. And an oxygen-free tank that is denitrified by microorganisms in this order, a second circulation path that circulates the water to be treated in the membrane separation tank to the oxygen-free tank, and the water to be treated in the oxygen-free tank Is provided with a third circulation path for circulating the gas to the anaerobic tank.

  In addition to any one of the first to fourth characteristic configurations described above, the seventh characteristic configuration is an anaerobic tank that releases phosphorus from microorganisms in the previous stage of the aerobic tank. And an oxygen-free tank for denitrification treatment with microorganisms in this order, a second circulation path for circulating the water to be treated in the membrane separation tank to the oxygen-free tank, and the water to be treated in the membrane separation tank Is provided with a third circulation path for circulating the gas to the anaerobic tank.

  The characteristic configuration of the operation method of the sewage treatment apparatus according to the present invention includes an aerobic tank provided with an air diffuser and an aerobic treatment of water to be treated by microorganisms, as described in claim 8, and a stage subsequent to the aerobic tank. Operation of a sewage treatment apparatus provided with a membrane separation tank in which a membrane separation apparatus is disposed for separating the treated water into solid and liquid, and a circulation path for circulating the treated water in the membrane separation tank to the aerobic tank A method is to measure an aerobic treatment index in the membrane separation tank and adjust a circulation amount of the circulation path based on a measured value.

  As described above, according to the present invention, the DO in the membrane separation tank is maintained at an appropriate value, the generation of the causative substance of the membrane fouling is suppressed, and further, the denitrification reaction in the oxygen-free tank and the anaerobic tank are performed. It is now possible to provide a sewage treatment apparatus capable of maintaining a good phosphorus release reaction and its operating method.

  Furthermore, since excess oxygen in the membrane separation tank can be effectively used in the aerobic tank, the amount of air diffused in the aerobic tank can be reduced.

1st explanatory drawing of the sewage treatment apparatus by this invention 2nd explanatory drawing of the sewage treatment apparatus by this invention 3rd explanatory drawing of the sewage treatment apparatus by this invention 4th explanatory drawing of the sewage treatment apparatus by this invention 5th explanatory drawing of the sewage treatment apparatus by this invention Explanatory drawing of conventional sewage treatment equipment

Hereinafter, embodiments of a sewage treatment apparatus and an operation method thereof according to the present invention will be described.
As shown in FIG. 1, the sewage treatment apparatus includes an anaerobic tank 1 into which raw water, which is untreated water to be treated, an anaerobic tank 2 adjacent to the downstream side of the anaerobic tank 1, and a downstream of the anoxic tank 2. The aerobic tank 3 adjacent to the side and the membrane separation tank 4 adjacent to the downstream side of the aerobic tank 3 are separated from each other by a partition wall.

  In the anaerobic tank 1, anaerobic treatment is performed by microorganisms under anaerobic conditions, and BOD components contained in the raw water are taken into the microorganisms, and phosphorus compounds are hydrolyzed to release phosphorus as normal phosphoric acid into the liquid.

  In the anaerobic tank 2, anaerobic treatment is performed by microorganisms under anaerobic conditions, and nitrate ions and nitrite ions are reduced to nitrogen gas, that is, denitrification treatment is performed.

  In the aerobic tank 3, an air diffuser 5 is installed at the bottom, and ammonium ions derived from human waste contained in the water to be treated are oxidized by microorganisms under aerobic conditions and converted into nitrous acid and nitric acid. A nitrification treatment is performed, and an aerobic treatment is performed in which normal phosphoric acid in the water to be treated is taken into sludge and accumulated as polyphosphoric acid.

  The membrane separation tank 4 is provided with a membrane separation device 6 for solid-liquid separation of the water to be treated. Solid matter such as activated sludge is separated from the water to be treated by the membrane separation device 6, and a water tank (not shown) in the subsequent stage is separated. Are discharged. As a separation membrane used in the membrane separation device 6, an ultrafiltration membrane, a microfiltration membrane, or the like is employed. As the form of the membrane, a hollow fiber membrane, a flat membrane, a tubular membrane or the like is adopted.

  An aeration device 7 for cleaning the membrane surface of the membrane separation device 6 is disposed below the membrane separation device 6. In the membrane separation tank 4, nitrification treatment is performed with activated sludge under aerobic conditions with oxygen supplied from the aeration device 7.

  Furthermore, a first circulation path 8 for circulating the treated water in the membrane separation tank 4 to the aerobic tank 3 is provided, and a second circulation for circulating the treated water in the membrane separation tank 4 to the anoxic tank 2. A path 9 and a third circulation path 10 for circulating the water to be treated in the anoxic tank 2 to the anaerobic tank 1 are provided.

  The water to be treated biologically treated in each of the treatment tanks 1, 2, 3 is transferred to the downstream side through an opening formed in the lower part of the partition wall, or is transferred to the downstream side after overflowing the partition wall.

  With such a configuration, nitrate ions and nitrite ions contained in the water to be treated by nitrification treatment are circulated to the anoxic tank 2 through the second circulation path 9, and denitrification treatment is performed. Microorganisms in the membrane separation tank 4 that have taken in phosphorus are circulated to the anaerobic tank 1 through the second and third circulation paths 10, and phosphorus is discharged into the liquid as normal phosphoric acid. Moreover, the activated sludge of the membrane separation tank 4 is discharged as excess sludge.

  The membrane separation tank 4 includes a first measurement device 20 that measures a dissolved oxygen concentration (hereinafter referred to as “DO”) as an index of aerobic treatment in the tank, and a measurement value obtained by the first measurement device 20. Based on this, a first control device 21 that adjusts the circulation amount of the water to be treated via the first circulation path 8 is provided.

  The first measuring device 20 adjusts the amount of water to be treated to be circulated through the first circulation path 8 to increase when the DO becomes larger than a preset reference value, and the dissolved oxygen concentration is higher than the reference value. Control to make it smaller. Specifically, the rotation speed of the pump provided in the membrane separation tank 4 is adjusted to adjust the circulation amount of the water to be treated via the circulation path 8, or the circulation path 8 is maintained by keeping the rotation speed of the pump constant. The amount of circulation is adjusted by adjusting the opening of the valve 24 provided in the above.

  For example, when the circulation amount of the water to be treated through the first circulation path 8 is increased in accordance with the rise of DO in the membrane separation tank, the inflow of sludge from the aerobic tank 3 having a lower DO than the membrane separation tank 4 The amount increases and the DO of the membrane separation tank 4 decreases. Furthermore, the residence time of the sludge in the aerobic tank 3 is shortened, the amount of untreated organic matter flowing into the membrane separation tank 4 is increased, and oxygen is consumed in the decomposition of the organic matter in the membrane separation tank 4, An abnormal increase in DO in the membrane separation tank 4 can be effectively suppressed, and generation of substances causing membrane fouling due to self-decomposition of activated sludge is suppressed.

  Conversely, when the DO in the membrane separation tank 4 becomes low and the circulation amount of the water to be treated through the first circulation path 8 is reduced, the inflow of sludge from the aerobic tank 3 having a lower DO than the membrane separation tank 4 The amount is decreased, and DO is adjusted to an appropriate value by oxygen supplied from the aeration apparatus 7 provided in the membrane separation tank 4.

  The aerobic tank 3 includes a second measuring device 22 that measures the dissolved oxygen concentration as an index of the aerobic treatment in the tank, and a measurement value of the aeration device 5 based on a measurement value obtained by the second measuring device 22. A second control device 23 for adjusting the amount of diffused air is provided.

  If the DO is higher than the predetermined target range, the second control device 23 reduces the amount of air diffused by the air diffuser 5 by decreasing the rotational speed of the air supply pump AP, and the DO is lower than the predetermined target range. If it is lower, the rotational speed of the air supply pump AP is increased and the amount of air diffused by the air diffuser 5 is increased and adjusted so that the dissolved oxygen concentration falls within a predetermined target range. Instead of adjusting the rotation of the air supply pump AP, the valve 25 indicated by the broken line in FIG. 1 provided for the connection between the air supply pump AP and the air diffuser 5 may be adjusted.

  The DO in the aerobic tank 3 varies depending on the circulation amount of the treated water through the first circulation path 8, but based on the result of measuring the DO in the aerobic tank by the second measuring device 22, the second The control device 23 adjusts the amount of air diffused in the air diffuser 5 and adjusts it to an appropriate DO. As a result, the DO of the membrane separation tank 4 is also adjusted more quickly. For example, if the DO in the aerobic tank 3 rises from an appropriate value, the air diffuser 5 is adjusted so that the amount of air diffused is reduced, and the DO in the aerobic tank 3 is lowered.

  The first measuring device 20 and the second measuring device 22 are not limited to a measuring device that measures DO as an index for aerobic treatment, and any one index of oxidation-reduction potential and nitrate nitrogen concentration is measured. It can consist of possible measuring instruments.

  In this case, when the measured value becomes larger than a preset reference value, the first control device 21 adjusts the amount of treated water to increase, and the second control device 23 adjusts the amount of air diffused to decrease. Is done.

  Further, the first measuring device 20 and the second measuring device 22 can be configured by a measuring instrument capable of measuring any one of pH and ammoniacal nitrogen concentration as an aerobic treatment index.

  In this case, when the measured value becomes smaller than a preset reference value, the first control device 21 adjusts the amount of treated water to increase, and the second control device 23 adjusts the amount of air diffused to decrease. Is done.

  The first measuring device 20 and the second measuring device 22 can also control a plurality of the above-described DO, redox potential, nitrate nitrogen concentration, pH, and ammoniacal nitrogen as an aerobic treatment index.

  In this way, the second measuring device 22 includes the aeration device 5 and the aerobic tank 3 that aerobically treats the water to be treated with microorganisms, and is disposed in the subsequent stage of the aerobic tank 3 to separate the water to be treated. A sewage treatment apparatus comprising a membrane separation tank 4 having a first measuring device 20 and a circulation path 8 for circulating the water to be treated in the membrane separation tank 4 to the aerobic tank 3. The operation method of the sewage treatment apparatus is measured, in which an aerobic treatment index in the membrane separation tank 4 is measured and the circulation amount of the circulation path 8 is adjusted based on the measured value.

  The circulation amount can be controlled by a method of controlling aerobic processing by setting a plurality of stages according to the aerobic processing and by PID control such as proportional control.

  The second control device 23 that adjusts the dissolved oxygen concentration is not limited to the device that adjusts the amount of air diffused by the air diffuser 5, but may be one that adjusts the oxygen transfer efficiency in the aerobic tank 3. . For example, as shown in FIG. 2, the configuration is such that the posture of the regulating plate is adjusted by an actuator such as a motor so that the ascending route of the diffused air in the aerobic tank 3 is restricted by the regulating plate or the like. There may be. If the passage of rising bubbles is restricted to limit the chance of contact with the water to be treated, the same effect as reducing the amount of air diffused can be obtained.

  As a method of adjusting the oxygen transfer efficiency, a fine bubble diffuser and a coarse bubble diffuser with different bubble diameters are installed in the aerobic tank 3, and the diffuser to be diffused is switched or the ratio of the blowout amount is adjusted. There is a way to do it. Also, the installation height of the diffuser can be adjusted, and the oxygen transfer efficiency can be adjusted by moving the diffuser up and down. When an underwater aeration device is used as an aeration device, it is possible to adjust the oxygen transfer efficiency by attaching a rotary stirring blade to the air blowing part of the aeration device and adjusting the stirring intensity by changing the rotation speed. is there.

  As a result, good anaerobic treatment is performed by the water to be treated having a low DO circulating through the second circulation path 9 and the third circulation path 10.

Hereinafter, another embodiment will be described.
In the embodiment described above, the second circulation path 9 that circulates the water to be treated in the membrane separation tank 4 to the anoxic tank 2 and the third circulation path that circulates the water to be treated in the anoxic tank 2 to the anaerobic tank 1. Although the example provided with the circulation path 10 was demonstrated, as shown in FIG. 3, the 2nd circulation path 9 which circulates the to-be-processed water in the membrane separation tank 4 to the anoxic tank 2, and the inside of the membrane separation tank 4 You may provide the 3rd circulation path 11 which circulates to-be-processed water to the anaerobic tank 1. FIG.

  In addition, as shown in FIG. 4, an anaerobic tank 2 that is denitrified by microorganisms and an anaerobic tank 1 that releases phosphorus from the microorganisms are arranged in this order in the preceding stage of the aerobic tank 3. You may provide the 2nd circulation path 12 which circulates to-be-processed water to the anaerobic tank 2, and the flow path which transfers the to-be-processed water in the anoxic tank 2 to the anaerobic tank 1. FIG. In this case, raw water flows into the anoxic tank 2 and the anaerobic tank 1.

  Further, as shown in FIG. 5, the first circulation path 8 or the first circulation path 8 and the second circulation path 9 are arranged with a vertical pipe line 30 installed so that one end faces the bottom of the membrane separation tank 4. Then, one end of a circulation path composed of a horizontal pipe 31 arranged so as to extend from the vertical pipe 30 in the horizontal direction is supplied with an air supply pump 32 to supply water to be treated to the aerobic tank 3 and You may comprise with the air lift pump which sends water to the anoxic tank 2. FIG.

  In the embodiment described above, in the aerobic tank 3, the second control device 23 that adjusts the amount of air diffused by the air diffuser 5 based on the measurement values obtained by the second measurement device 22 and the second measurement device 22. However, even if the second measuring device 22 and the second control device 23 are not provided, the DO of the membrane separation tank 4 can be adjusted.

  The first measuring device 20 does not need to be installed in the membrane separation tank 4 and can be installed in the first circulation path 8 or the membrane permeate pipe.

  In the above-described embodiment, the sewage treatment apparatus in which activated sludge is circulated and supplied to the treatment tanks 1, 2, 3, and 4 has been described. However, the present invention replaces the activated sludge with each treatment tank 1, 2, 3, and 4. The present invention can also be applied to a sewage treatment apparatus in which a carrier for supporting microorganisms 4 is installed.

  Each of the above-described embodiments is an example of the present invention, and the present invention is not limited by the description. The specific configuration of each part can be appropriately changed and designed within the range where the effects of the present invention are exhibited. Needless to say.

1: Anaerobic tank 2: Anoxic tank 3: Aerobic tank 4: Membrane separation tank 6: Membrane separation device 8: First circulation path (first circulation path)
9, 12: Second circuit (second circuit)
10, 11: Third circuit 20: First measurement device 21: First control device 22: Second measurement device 23: Second control device

Claims (8)

An aerobic tank equipped with an air diffuser and aerobically treating the treated water with microorganisms; a membrane separation tank disposed at a subsequent stage of the aerobic tank and provided with a membrane separation device for separating the treated water into solid and liquid; and A sewage treatment apparatus comprising a first circulation path for circulating the treated water in the membrane separation tank to the aerobic tank,
Based on the first measurement device that measures the aerobic treatment index in the membrane separation tank, and the measurement value by the first measurement device, the circulation amount of the water to be treated through the first circulation path A sewage treatment apparatus comprising a first control device for adjustment.   When at least one of the indicators of dissolved oxygen concentration, redox potential, and nitrate nitrogen concentration is measured by the first measuring device and the measured value becomes larger than a preset reference value, the first control device It adjusts so that the circulation amount of to-be-processed water may be increased, The sewage treatment apparatus of Claim 1 characterized by the above-mentioned.   When at least one index of pH and ammonia nitrogen concentration is measured by the first measuring device and the measured value is smaller than a preset reference value, the first control device is configured to circulate the amount of water to be treated. The sewage treatment apparatus according to claim 1, wherein the sewage treatment apparatus is adjusted so as to increase.   A second measuring device that measures an aerobic treatment index in the aerobic tank, and a second control device that adjusts the dissolved oxygen concentration based on a measurement value obtained by the second measuring device. The sewage treatment apparatus according to any one of claims 1 to 3.   An anaerobic tank for releasing phosphorus from microorganisms and an anaerobic tank for denitrification treatment with microorganisms are provided in the front stage of the aerobic tank, and a second water for circulating the treated water in the membrane separation tank to the anoxic tank. The sewage treatment apparatus according to any one of claims 1 to 4, further comprising a circulation path and a flow path for transferring the water to be treated in the anaerobic tank to the anaerobic tank.   An anaerobic tank for releasing phosphorus from microorganisms and an anaerobic tank for denitrification treatment by microorganisms are provided in this order in front of the aerobic tank, and the water to be treated in the membrane separation tank is circulated to the anoxic tank. The sewage treatment according to any one of claims 1 to 4, further comprising a second circulation path and a third circulation path for circulating the water to be treated in the oxygen-free tank to the anaerobic tank. apparatus.   An anaerobic tank for releasing phosphorus from microorganisms and an anaerobic tank for denitrification treatment by microorganisms are provided in this order in front of the aerobic tank, and the water to be treated in the membrane separation tank is circulated to the anoxic tank. The sewage treatment according to any one of claims 1 to 4, further comprising a second circulation path and a third circulation path for circulating the water to be treated in the membrane separation tank to the anaerobic tank. apparatus. An aerobic tank equipped with an air diffuser and aerobically treating the treated water with microorganisms; a membrane separation tank disposed at a subsequent stage of the aerobic tank and provided with a membrane separation device for separating the treated water into solid and liquid; and A method for operating a sewage treatment apparatus comprising a circulation path for circulating water to be treated in a membrane separation tank to the aerobic tank,
A method for operating a sewage treatment apparatus, comprising measuring an aerobic treatment index in the membrane separation tank and adjusting a circulation amount of the circulation path based on a measured value.

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