JP7195968B2 - Method for operating organic wastewater treatment equipment and organic wastewater treatment equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of operating an organic wastewater treatment apparatus and an organic wastewater treatment apparatus.

The combined sewage treatment system, which is often used in urban areas, transports both rainwater and sewage through a shared sewer system. An activated sludge process (UCT method or A2O method) equipped with a biological treatment tank equipped with a tank and an aerobic tank in which an anaerobic-anoxic-aerobic process is performed, and a final sedimentation tank for precipitating and separating activated sludge from the treated water after biological treatment. was installed with organic wastewater treatment equipment.

In conventional organic wastewater treatment equipment, when a large amount of sewage that exceeds the treatment capacity of the biological treatment tank and final sedimentation tank flows in at one time during rainy weather, the wastewater that has settled and removed the solid content in the primary sedimentation tank is used for subsequent biological treatment. It was operated for simple discharge without treatment in the tank.

Patent Document 1 discloses an organic wastewater treatment system that employs a membrane bioreactor (MBR) method, in which organic sewage with a high nitrogen concentration is biologically treated in a reaction tank equipped with an immersion membrane separator. is disclosed.

By using an immersion type membrane separation device instead of the conventional final sedimentation tank, the organic wastewater treatment device can improve the quality of the treated water regardless of whether it is sunny or rainy, and furthermore, the equipment can be improved. It is attracting attention as an organic wastewater treatment system that can be miniaturized.

In Patent Document 2, a primary sedimentation tank, a reaction tank, a final sedimentation tank, a first flow path that connects the primary sedimentation tank and the reaction tank, and a second flow path that connects the reaction tank and the final sedimentation tank A wastewater treatment system comprising a plurality of reaction trains containing L, wastewater is supplied to the reaction tank through the first channel, and wastewater exceeding the processing capacity of the reaction tank is supplied to the final sedimentation tank through the second channel. A wastewater treatment system is disclosed.

Japanese Patent Application Laid-Open No. 2001-62481 JP 2011-147868 A

By the way, the membrane separation activated sludge method has an upper limit on the amount of filtered water per unit area of the membrane, so if the facility is designed so that the entire amount can be filtered according to the peak of the flow rate, such as during rainy weather, excessive capital investment will be required. As a result, there is a problem that the cost-effectiveness is low.

In such a case, as shown in FIG. 9, an organic wastewater treatment apparatus employing a membrane separation activated sludge method and an organic wastewater treatment apparatus employing the above-described conventional activated sludge method are mixed. If the wastewater treatment equipment is configured and the conventional organic wastewater treatment equipment is operated when the inflow of wastewater increases to treat the peak flow rate of the inflow wastewater, organic wastewater using the membrane separation activated sludge method can be Although the facility capacity of the wastewater treatment equipment can be suppressed, there are the following problems.

In other words, since the conventional activated sludge method is inferior to the membrane separation activated sludge method in treated water quality, it is desirable to treat only with the membrane separation activated sludge method in normal times, but the conventional method can be used in a short time during a specific period such as rainy weather. Since it is not possible to start up an organic wastewater treatment system that employs the activated sludge method for treatment, the organic wastewater treatment system that employs the membrane separation activated sludge method and the organic wastewater treatment system that employs the conventional method are always installed in parallel. Therefore, it was complicated to determine the amount of inflow wastewater to be distributed to each system.

In the conventional method, solid-liquid separation is generally performed in a sedimentation tank, and in order to achieve good solid-liquid separation, it is necessary to suppress the MLSS concentration in the sedimentation tank to 3000 mg/L or less. Therefore, even if the sludge from the aerobic tank adopting the membrane separation activated sludge method, which has a MLSS concentration of 8000 to 10000 mg / L, which is higher than the conventional method, is led to the sedimentation tank, solid-liquid separation cannot be performed well. There was also a problem that the sludge flowed out to the treated water side.

Therefore, in order to reduce the MLSS concentration and secure the solid-liquid separation performance in the sedimentation tank while adopting the membrane separation activated sludge method, as described in Patent Document 2, a carrier is added to maintain the treatment capacity. However, there is a problem that the screen for preventing the carrier from flowing out to the sedimentation tank is clogged with the carrier when the flow rate increases.

In addition, when the existing organic wastewater treatment system adopting the conventional method is rebuilt into a new organic wastewater treatment system adopting the membrane separation activated sludge method using the civil engineering framework, the membrane separation activated sludge method is unnecessary. Although it is desired to effectively utilize the civil engineering framework of the final sedimentation tank, generally the water depth of the final sedimentation tank is relatively shallow and the tank shape is vertically long, so the membrane separator is placed submerged. It was difficult to use as a reaction tank for MBR, and even if it was used, it was not possible to increase the amount of treated water so much.

In view of the above-mentioned problems, the object of the present invention is to suppress the facility capacity of an organic wastewater treatment apparatus that employs a membrane separation activated sludge method, regardless of fluctuations in the amount of inflow of organic wastewater and the treatment load. Another object of the present invention is to provide a method for operating an organic wastewater treatment apparatus and an organic wastewater treatment apparatus capable of discharging treated water that has been thoroughly treated.

In order to achieve the above object, the first characteristic configuration of the method for operating an organic wastewater treatment apparatus according to the present invention is an organic A method of operating a wastewater treatment apparatus, wherein organic wastewater is supplied to the anoxic tank, and a mixture of organic wastewater and activated sludge is circulated between the anoxic tank and the first aerobic tank. While performing nitrification and denitrification treatment, the membrane permeated liquid from the membrane separation device arranged in the first aerobic tank is taken out as treated water, and the mixed liquid is sent from the anoxic tank to the second aerobic tank. Further, the liquid mixture is sent from the second aerobic tank to the sedimentation tank, and the solid-liquid separation liquid from the sedimentation tank is taken out as treated water.

The organic wastewater supplied to the anoxic tank is circulated together with the activated sludge to the first aerobic tank in which the membrane separator is arranged, and is subjected to nitrification and denitrification treatment, and the liquid mixture is separated from the membrane separator. is taken out as treated water. Further, part of the mixed liquid is sent from the anoxic tank to the second aerobic tank, where it undergoes initial adsorption treatment, and the mixed liquid sent to the sedimentation tank is subjected to solid-liquid separation in the sedimentation tank. The supernatant is taken out as treated water. By adjusting the MLSS concentrations in the first aerobic tank and the second aerobic tank individually via the anoxic tank, the MLSS concentration in the first aerobic tank is adjusted to a high level suitable for membrane separation, while the second favorable In the gas tank, the MLSS concentration can be adjusted to a low level suitable for solid-liquid separation in the sedimentation tank.

The initial adsorption is a phenomenon in which fine particles and soluble organic matter in organic wastewater are physically adsorbed on the surface of the activated sludge by sticky gelatin substances secreted by aerobic microorganisms in the activated sludge. It refers to a biosorption phenomenon in which microorganisms are quickly taken in, and BOD is greatly reduced in several tens of minutes after activated sludge and organic wastewater come into contact with each other.

In this way, by combining solid-liquid separation based on membranes and solid-liquid separation based on conventional sedimentation tanks, it is possible to reduce the number of installed membrane separation devices required when all the amount is treated by MBR, and it is economical. The organic waste water treatment equipment enables efficient purification treatment.

The second characteristic configuration is a method of operating an organic wastewater treatment apparatus comprising an anoxic tank, a first aerobic tank, a second aerobic tank, a mixing tank, and a sedimentation tank, wherein the organic wastewater is mixed with the tank, and while circulating the mixture of organic wastewater and activated sludge between the mixing tank and the anoxic tank, the organic wastewater is circulated between the anoxic tank and the first aerobic tank. and activated sludge are circulated to carry out nitrification and denitrification treatment, and the membrane permeated liquid from the membrane separation device arranged in the first aerobic tank is taken out as treated water from the mixing tank. 2, the mixed liquid is sent to the aerobic tank, the mixed liquid is sent from the second aerobic tank to the sedimentation tank, and the solid-liquid separation liquid from the sedimentation tank is taken out as treated water.

The organic wastewater supplied to the mixing tank is sent to the first aerobic tank in which the membrane separation device is arranged together with the activated sludge through the anoxic tank, and the Nitrification and denitrification treatment is carried out by circulating at , and the liquid portion of the mixed liquid is taken out as treated water from the membrane separator. Further, a part of the mixed liquid is sent from the mixing tank to the second aerobic tank and subjected to initial adsorption treatment in the second aerobic tank. is taken out as treated water. By individually adjusting the MLSS concentrations in the first aerobic tank and the second aerobic tank via the mixing tank, the MLSS concentration in the first aerobic tank is adjusted to a high level suitable for membrane separation, while the second aerobic tank In the tank, the MLSS concentration can be adjusted to a low level suitable for solid-liquid separation in the sedimentation tank. can be recovered, and a decrease in pH in the first aerobic tank where nitrification treatment is performed can be avoided without affecting the second aerobic tank.

The third characteristic configuration is a method of operating an organic wastewater treatment apparatus comprising an anoxic tank, a first aerobic tank, a combined tank, and a sedimentation tank, wherein organic wastewater is supplied to the anoxic tank, A membrane separator disposed in the first aerobic tank while performing nitrification and denitrification by circulating a mixture of organic wastewater and activated sludge between the anoxic tank and the first aerobic tank. The membrane-permeated liquid from the A first operating state in which a solid-liquid separated liquid from the sedimentation tank is taken out as treated water, and a mixed liquid is circulated between the anoxic tank and the first aerobic tank while the anoxic tank and the anoxic treatment are performed. A second operating state in which the mixed liquid is circulated between the combined liquid and the aerobic tank to perform nitrification and denitrification treatment, and the membrane permeated liquid from the membrane separation device disposed exclusively in the first aerobic tank is taken out as treated water. and is provided.

When the amount of organic waste water is sufficient, it is treated in the first operating state in which the combined tank functions as an aerobic tank, and the organic waste water supplied to the anoxic tank is treated together with the activated sludge in the first membrane separation device. Nitrification and denitrification treatment is performed by circulating between the aerobic tanks, and the liquid portion of the mixed liquid is taken out as treated water from the membrane separator. Further, part of the mixed liquid is sent from the anoxic tank to the dual-purpose tank and subjected to initial adsorption treatment as aerobic treatment. taken out. When the amount of organic wastewater is small, the combined liquid is treated in the second operating state in which the combined tank functions as an anoxic tank, and the mixture is circulated between the anoxic tank, the first aerobic tank, and the combined tank performing the anoxic treatment. While the nitrification and denitrification treatment is being carried out, the membrane permeated liquid from the membrane separator arranged exclusively in the first aerobic tank is taken out as treated water.

The fourth characteristic configuration is, in addition to any one of the first to third characteristic configurations described above, in that the sludge in the sedimentation tank is returned to the first aerobic tank.

By returning the sludge from the sedimentation tank to the first aerobic tank, it is possible to avoid a decrease in the MLSS concentration in the first aerobic tank in which the membrane separation device is installed. Since the sedimented and separated sludge is in a state where BOD is adsorbed, the initial adsorption performance is lost. Decomposition of the BOD produced is accelerated, and the initial adsorption performance of the sludge is recovered.

The fifth characteristic configuration is, in addition to any one of the first to third characteristic configurations described above, in that the sludge in the sedimentation tank is returned to the anoxic tank.

The BOD remaining in the sedimentation sludge returned to the anoxic tank is effectively used as an organic source for denitrification, and the sludge is transferred to the first aerobic tank and aerobicly treated in a low-load state. The initial adsorption performance of sludge is recovered.

The sixth characteristic configuration is, in addition to any one of the above-described first to fifth characteristic configurations, during the transfer of the mixed liquid from the second aerobic tank or the dual-use tank to the sedimentation tank or the sedimentation tank The point is that a flocculant is added to the

By adding a coagulant to the sedimentation tank or during the transfer of the mixed liquid from the second aerobic tank or the above-mentioned dual-use tank to the sedimentation tank, the COD and dephosphorization effects on the treated water and the sedimentation separation effect of the sludge can be enhanced. can.

The first characteristic configuration of the organic wastewater treatment apparatus according to the present invention comprises an anoxic tank for denitrification, a first aerobic tank for nitrification, provided with a membrane separator for extracting treated water as a membrane permeate, A second aerobic tank for performing initial adsorption treatment, a sedimentation tank, a raw water supply route for supplying organic wastewater to the anoxic tank, and organic wastewater and activated sludge from the anoxic tank to the first aerobic tank. a first mixed solution route for sending the mixed solution, a first circulation route for circulating the mixed solution from the first aerobic tank to the anoxic tank, and a mixed solution sent from the second aerobic tank to the sedimentation tank It is provided with a second liquid mixture path and a third liquid mixture path for sending the liquid mixture from the anoxic tank to the second aerobic tank.

The second characteristic configuration includes an anoxic tank for denitrification treatment, a first aerobic tank for nitrification treatment equipped with a membrane separation device for taking out treated water as a membrane permeate, and a second aerobic tank for initial adsorption treatment. An air tank, a mixing tank, a sedimentation tank, a raw water supply path for supplying organic wastewater to the mixing tank, and a mixed solution of organic wastewater and activated sludge from the first aerobic tank to the anoxic tank. a first circulation path for circulation, a second circulation path for circulating the mixed liquid from the anoxic tank to the mixing tank, and a second mixed liquid path for sending the mixed liquid from the second aerobic tank to the sedimentation tank; and a fourth mixed solution path for sending the mixed solution from the mixing tank to the second aerobic tank.

The third characteristic configuration includes an anoxic tank for denitrification, a first aerobic tank equipped with a membrane separation device for taking out treated water as a membrane permeated liquid, and performing nitrification, a dual-purpose tank, a sedimentation tank, a raw water supply path for supplying organic wastewater to the anoxic tank; a first mixed solution path for sending a mixed solution of organic wastewater and activated sludge from the anoxic tank to the first aerobic tank; A second mixed solution route for sending the mixed solution to the sedimentation tank, a third mixed solution route for sending the mixed solution from the anoxic tank to the combined tank, and a circulation of the mixed solution from the first aerobic tank to the anoxic tank and a third circulation path for circulating the mixed solution from the anoxic tank to the combined tank, the third circulation path is opened, and the combined tank is used as the second aerobic tank. It is characterized in that it can be switched between a first operating state in which it functions and a second operating state in which the third circulation path is closed and the combined tank functions as a second anoxic tank.

The fourth characteristic configuration is, in addition to any one of the first to third characteristic configurations described above, the first aerobic tank is arranged in the upper space via the first partition wall, and the non-aerobic tank is arranged in the lower space. It is in the point where the oxygen tank is arranged.

By arranging the first aerobic tank in the upper space of the site where the anoxic tank is arranged, the space utilization rate is increased, and the site of the organic wastewater treatment apparatus can be efficiently utilized.

The fifth characteristic configuration is that, in addition to the above-described fourth characteristic configuration, the sedimentation tank is arranged in the lower space of the anoxic tank via a second partition wall.

Furthermore, space utilization can be increased.

The sixth characteristic configuration is that, in addition to any one of the first to fifth characteristic configurations, a sludge return path is provided for returning the sludge from the sedimentation tank to the first aerobic tank.

As described above, according to the present invention, regardless of fluctuations in the amount of inflow of organic wastewater and the treatment load, the organic wastewater treatment apparatus adopting the membrane separation activated sludge method can be appropriately treated while suppressing the facility capacity. It is now possible to provide an operating method of an organic wastewater treatment apparatus and an organic wastewater treatment apparatus capable of discharging the treated water treated by the method.

Explanatory drawing of the overall configuration of the organic wastewater treatment apparatus according to the present invention Explanatory drawing of the organic wastewater treatment apparatus according to the first embodiment Explanatory drawing of the organic wastewater treatment apparatus according to the second embodiment Explanatory drawing of the organic wastewater treatment device showing another aspect of the second embodiment Explanatory drawing of the organic wastewater treatment apparatus according to the third embodiment Explanatory drawing of the organic wastewater treatment apparatus according to the fourth embodiment Explanatory drawing of the organic wastewater treatment apparatus according to the fifth embodiment Explanatory drawing of the organic wastewater treatment apparatus according to the sixth embodiment (a) is an explanatory diagram of an organic wastewater treatment apparatus according to a seventh embodiment, and (b) is an explanatory diagram of a circulating MBR. Explanatory diagram of the operation method of conventional organic wastewater treatment equipment

Hereinafter, a method for operating an organic wastewater treatment apparatus and an organic wastewater treatment apparatus according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, an organic wastewater treatment device 100 is a device for introducing organic wastewater such as sewage as raw water, purifying it by biological treatment, and discharging it into a river or the like. It is equipped with 6 systems of biological treatment tanks 20, 40, 50 employing MBR, a final sedimentation tank 70, a disinfection tank 90, and the like.

The post-sedimentation water from the five primary sedimentation tanks 10 is sent to the screen wells 11 equipped with a screen mechanism to remove contaminants, and then evenly sent to the biological treatment tanks 20, 40, 50 filled with activated sludge. be done. The biological treatment tanks 20, 40, 50 of each system are configured to use both MBR and the conventional activated sludge method.

[First embodiment]
FIG. 2 shows the configuration of one system of the biological treatment tank shown in FIG.
The organic wastewater treatment apparatus 100 includes a primary sedimentation tank 10, an anoxic tank 40 for denitrification, and a membrane separator 30 for taking out treated water as a membrane permeate, and a first aerobic tank 20 for nitrification. , a second aerobic tank 50 for initial adsorption treatment, and a final sedimentation tank 70 .

A final sedimentation tank 70 functions as the sedimentation tank 70 of the present invention, and the sedimentation tank 70 is equipped with an inclined plate 71 for improving the sedimentation efficiency. Further, the anoxic tank 40 is provided with a stirring mechanism for stirring the activated sludge and the organic waste water in the tank, and the second aerobic tank 50 is provided with an air diffuser for aerobic treatment. ing. 2, the screen well shown in FIG. 1 is omitted. The sedimentation tank 70 shown in Figs. 3 to 6 and Figs. 8 to 9, which will be described later, is also provided with an inclined plate 71 in order to improve the sedimentation efficiency.

A raw water supply route 1 for supplying organic waste water, which is water after sedimentation, to the anoxic tank 40, and a first mixed solution route for sending a mixed solution of organic waste water and activated sludge from the anoxic tank 40 to the first aerobic tank 20. 2, a first circulation route 3 for circulating the mixed solution from the first aerobic tank 20 to the anoxic tank, a second mixed solution route 4 for sending the mixed solution from the second aerobic tank 50 to the sedimentation tank 70, A third mixed solution route 5 for sending the mixed solution from the oxygen tank 40 to the second aerobic tank and a sludge return route 6 for returning the sludge from the sedimentation tank 70 to the first aerobic tank 20 are provided.

In the organic wastewater treatment apparatus 100, organic wastewater is supplied to the anoxic tank 40, and a mixture of organic wastewater and activated sludge is circulated between the anoxic tank 40 and the first aerobic tank 20. While performing the nitrification and denitrification treatment, the membrane permeated liquid from the membrane separation device 30 arranged in the first aerobic tank 20 is taken out as treated water, and the mixed liquid is sent from the anoxic tank 40 to the second aerobic tank 50. Further, the mixed liquid is sent from the second aerobic tank 50 to the sedimentation tank 70, and the solid-liquid separation liquid from the sedimentation tank 70 is taken out as treated water.

The organic wastewater supplied to the anoxic tank 40 is circulated together with the activated sludge through the first liquid mixture path 2 and the first circulation path 3 between the first aerobic tank 20 in which the membrane separation device 30 is arranged. As a result, ammonium nitrogen is nitrified to nitrate nitrogen in the first aerobic tank 20, and denitrification treatment is performed in which the nitrate nitrogen is reduced to nitrogen in the anoxic tank 40. A liquid component of the mixed liquid is taken out as treated water.

Further, part of the mixed liquid is sent from the anoxic tank 40 to the second aerobic tank 50 and is subjected to initial adsorption treatment in the second aerobic tank 50, and the mixed liquid sent to the sedimentation tank 70 is After solid-liquid separation, the supernatant is taken out as treated water.

The initial adsorption is a phenomenon in which fine particles and soluble organic matter in organic wastewater are physically adsorbed on the surface of the activated sludge by sticky gelatin substances secreted by aerobic microorganisms in the activated sludge. BOD is rapidly absorbed by microorganisms, and BOD is greatly reduced in several tens of minutes after the activated sludge and organic wastewater come into contact with each other.

The sludge interface of the sedimentation tank 70 is monitored with a sludge interface meter, and if there is a concern that solid-liquid separation will be hindered due to the rise of the sludge interface, the flow rate of the membrane filtration device 30 is increased to allow the flow to the sedimentation tank 70. It is controlled to suppress the amount of water distributed. The outflow of sludge from the sedimentation tank 70 is prevented, and the treated water quality is kept good. In this way, by utilizing the solid-liquid separation by the sedimentation tank 70, the high-flux operation time of the membrane filtration device 30 can be shortened, the clogging speed of the membrane can be suppressed, and the frequency of chemical cleaning can be reduced.

By individually adjusting the MLSS concentrations of the first aerobic tank 20 and the second aerobic tank 50 via the anoxic tank 40, the first aerobic tank 20 is adjusted to a high MLSS concentration suitable for membrane separation. , the second aerobic tank 50 can be adjusted to a low MLSS concentration suitable for solid-liquid separation in the sedimentation tank.

In this embodiment, the amount of treated water in the first aerobic tank 20 is set to 0.5 Q with respect to the inflow amount of organic wastewater, which is raw water, 1 Q, and the amount of return from the sedimentation tank 70 to the first aerobic tank 20 is set to 0.5Q, and the circulation amount from the first aerobic tank 20 to the anoxic tank 40 is set to 0.4Q, so that the MLSS concentration in the first aerobic tank 20 is 10,000 mg / L, The MLSS concentration in the oxygen tank 40 is adjusted to 3,000 mg/L, and the MLSS concentration in the second aerobic tank 50 is adjusted to 3,000 mg/L to ensure solid-liquid separation performance in the sedimentation tank 70 .

As a result, the amount of water required for membrane filtration by the membrane separation device 30 can be reduced, and the number of membrane separation devices 30 can be reduced, resulting in a cost reduction effect. In addition, the difficultly decomposed soluble COD that accumulates in the sludge during the low water temperature period, which is a problem when the MBR is operated alone, flows out from the sedimentation tank 70 as treated water, thereby improving the membrane filtration performance of the sludge. can be raised.

Note that the MLSS concentration in each tank described above is an example, and is not limited to this value. In addition, the amount of water to be treated in the second aerobic tank 50 can basically be determined according to circumstances, and detailed control of the flow rate is not required. The labor for maintenance and management is reduced compared to the organic wastewater treatment equipment mixed with the separated activated sludge method.

Furthermore, when the existing organic wastewater treatment device 100 is remodeled into an MBR, there may be spatial restrictions on the installation of the membrane separation device 30 due to the influence of beams, Y walls, etc. provided in the existing structural frame. . In such a case, the treatment capacity can be increased compared to treating the entire amount of organic wastewater with MBR.

By the way, since the treated water discharged from the second aerobic tank 50 through the sedimentation tank 70 is not expected to denitrify, the treated water to be membrane-filtered by the membrane separator 30 must be sufficiently denitrified. There is In order for the water to be treated to be circulated between the anoxic tank 40 and the first aerobic tank 20 and membrane-filtered by the membrane separator 30 to be satisfactorily denitrified, a sufficient amount of BOD is required. necessary. However, when the BOD concentration of the organic wastewater is relatively low with respect to the nitrogen concentration (theoretically, BOD/N≤2.86), sufficient denitrification treatment cannot be performed.

In such a case, instead of the sludge return route 6 for returning the sludge in the sedimentation tank 70 to the first aerobic tank 20, a sludge return route 6A for returning the sludge in the sedimentation tank 70 to the anoxic tank 40 should be provided. is preferred (indicated by a dashed line in FIG. 2).

The BOD remaining in the sedimentation sludge returned to the anoxic tank 40 is effectively used as an organic source for denitrification, and the sludge is transferred to the first aerobic tank 20 and aerobicly treated in a low-load state. As a result, the sludge whose initial adsorption performance has been recovered is supplied to the second aerobic tank 50 . As a result, even when the BOD concentration is relatively low with respect to the nitrogen concentration, it is possible to reduce the nitrogen concentration of the discharged treated water.

[Second embodiment]
FIG. 3 shows the configuration of one system of the biological treatment tank shown in FIG. FIG. 3 shows the flow rate of each part based on the inflow amount Q of the organic waste water.
The organic wastewater treatment apparatus 100 includes a primary sedimentation tank 10, an anoxic tank 40 for denitrification, and a membrane separator 30 for taking out treated water as a membrane permeate, and a first aerobic tank 20 for nitrification. , a second aerobic tank 50 for initial adsorption treatment, a mixing tank 60 and a final sedimentation tank (sedimentation tank) 70 .

A raw water supply route 1 that supplies organic wastewater to the mixing tank 60, an eighth mixing route 9 that sends a mixed liquid of organic wastewater and activated sludge from the mixing tank 60 to the anoxic tank 40, A first mixed solution path 2 for sending a mixed solution of organic wastewater and activated sludge to the aerobic tank 20, and a second route for circulating the mixed solution of organic wastewater and activated sludge from the first aerobic tank 20 to the anoxic tank 40. 1 circulation path 3, a second circulation path 7 that circulates the mixture from the anoxic tank 40 to the mixing tank 60, a second mixture path 4 that sends the mixture from the second aerobic tank 50 to the sedimentation tank 70, A fourth mixed solution route 8 for sending the mixed solution from the mixing tank 60 to the second aerobic tank and a sludge return route 6 for returning the sludge from the sedimentation tank 70 to the first aerobic tank 20 are provided.

In the organic wastewater treatment apparatus 100, organic wastewater is supplied to the mixing tank 60, and a mixture of organic wastewater and activated sludge is produced between the mixing tank 60, the anoxic tank 40, and the first aerobic tank 20. While performing nitrification and denitrification treatment by circulating, the membrane permeated liquid from the membrane separation device 30 arranged in the first aerobic tank 20 is taken out as treated water, and the mixed liquid is transferred from the mixing tank 60 to the second aerobic tank 50. and the mixed liquid from the second aerobic tank 50 to the sedimentation tank 70, and the solid-liquid separated liquid from the sedimentation tank 70 is taken out as treated water.

The organic wastewater supplied to the mixing tank 60 is sent together with the activated sludge through the anoxic tank 40 to the first aerobic tank 20 in which the membrane separation device 30 is arranged. Nitrification and denitrification treatment is performed by circulating between the aerobic tanks 20, and the liquid portion of the mixed liquid is taken out from the membrane separator 30 as treated water.

Further, part of the mixed liquid is sent from the mixing tank 60 to the second aerobic tank 50 and subjected to initial adsorption treatment in the second aerobic tank 50, and the mixed liquid sent to the sedimentation tank 70 is solidified in the sedimentation tank 70. After liquid separation, the supernatant is taken out as treated water.

In the first embodiment described above, in order to adjust the MLSS concentration in the second aerobic tank 50 to a value suitable for solid-liquid separation by the sedimentation tank 70, the As a result of limiting the amount of sludge to be drawn, sufficient alkalinity recovery is not achieved and the pH value of the first aerobic tank 20 where the nitrification process is carried out is lowered.

However, in the second embodiment, since the mixing tank 60 is provided, even if the amount of mixed liquid circulated from the first aerobic tank 20 to the anoxic tank 40 is increased, the second aerobic tank 50 is affected. (without increasing the MLSS concentration), it is possible to avoid an abnormal decrease in pH in the first aerobic tank 20.

In this embodiment, the amount of treated water in the first aerobic tank 20 is set to 0.6Q with respect to the inflow of organic wastewater, which is raw water, 1Q, and the amount of return from the sedimentation tank 70 to the first aerobic tank 20 is set to 0.2Q, the circulation amount from the first aerobic tank 20 to the anaerobic tank 40 is set to 2Q, and the circulation amount from the anaerobic tank 40 to the mixing tank 60 is set to 0.35Q , Adjust the MLSS concentration of the first aerobic tank 20 to 10,000 mg / L, the MLSS concentration of the anoxic tank 40 to 7,800 mg / L, and the MLSS concentration of the second aerobic tank 50 to 2,000 mg / L, Solid-liquid separation performance in the sedimentation tank 70 is ensured.

As in the first embodiment, instead of the sludge return route 6 for returning the sludge in the sedimentation tank 70 to the first aerobic tank 20, a sludge return route 6A for returning the sludge in the sedimentation tank 70 to the anoxic tank 40 is provided. It is preferable to have it (indicated by a dashed line in FIG. 3).

The BOD remaining in the sedimentation sludge returned to the anoxic tank 40 is effectively used as an organic source for denitrification, and the sludge is transferred to the first aerobic tank 20 and aerobicly treated in a low-load state. As a result, the sludge whose initial adsorption performance has been recovered is supplied to the second aerobic tank 50 .

FIG. 4 shows an organic wastewater treatment apparatus 100 capable of avoiding an abnormal decrease in pH in the first aerobic tank 20 without providing the mixing tank 60 . The difference from the organic waste water treatment apparatus 100 shown in FIG.

As the mixing mechanism 41, an air lift pump provided with the first liquid mixture path 2 and the third liquid mixture path 5 is used. Air bubbles are supplied from the end of the inverted U-shaped air supply pipe to generate an upward flow of activated sludge, the activated sludge and organic wastewater are mixed inside the air supply pipe, and connected to the inverted U-shaped air supply pipe. The mixed liquid is sent to the first aerobic tank 20 by the liquid-sending pipe functioning as the first mixed-solution path 2, and the liquid-sending pipe connected to the inverted U-shaped air supply pipe and functioning as the third mixed-solution path 5. is configured to directly feed the mixed liquid to the second aerobic tank 50. Then, by setting the circulation amount of the mixed solution from the first aerobic tank 20 to the anoxic tank 40 via the first circulation path 3 to 2Q, the alkalinity accompanying the denitrification reaction is recovered, and the first Abnormal pH drop in the aerobic tank 20 is avoided.

As in the first embodiment, instead of the sludge return route 6 for returning the sludge in the sedimentation tank 70 to the first aerobic tank 20, a sludge return route 6A for returning the sludge in the sedimentation tank 70 to the anoxic tank 40 is provided. It is preferable to have it (indicated by a dashed line in FIG. 4).

The BOD remaining in the sedimentation sludge returned to the anoxic tank 40 is effectively used as an organic source for denitrification, and the sludge is transferred to the first aerobic tank 20 and aerobicly treated in a low-load state. As a result, the sludge whose initial adsorption performance has been recovered is supplied to the second aerobic tank 50 .

[Third Embodiment]
5(a) and 5(b) show the configuration of one system of the biological treatment tank shown in FIG. FIGS. 5(a) and 5(b) show the flow rate of each part based on the inflow amount Q of the organic waste water.
The organic wastewater treatment apparatus 100 includes a primary sedimentation tank 10, an anoxic tank 40 for denitrification, and a membrane separator 30 for taking out treated water as a membrane permeate, and a first aerobic tank 20 for nitrification. , a dual-use tank 50 whose function can be switched as a second aerobic tank or a second anoxic tank for performing the above-mentioned initial adsorption treatment, and a final sedimentation tank (sedimentation tank) 70 are provided.

Furthermore, a raw water supply route 1 that supplies organic wastewater to the anoxic tank 40, a first mixed solution route 2 that sends a mixed solution of organic wastewater and activated sludge from the anoxic tank 40 to the first aerobic tank 20, A second mixed solution route 4 for sending the mixed solution from the dual-use tank 50 to the sedimentation tank 70, a third mixed solution route 5 for sending the mixed solution from the anoxic tank 40 to the dual-purpose tank 50, and an oxygen-free from the first aerobic tank 20 A first circulation path 3 that circulates the mixed liquid to the tank 40, a third circulation path 31 that circulates the mixed liquid from the anoxic tank 40 to the combined tank 50, and the sludge of the sedimentation tank 70 is returned to the first aerobic tank 20. It has a sludge return route 6 to do.

Then, the third circulation path 31 is closed and the combined tank 50 functions as a second aerobic tank for performing the initial adsorption treatment in a first operating state, and the third circulation path 31 is opened to turn the combined tank 50 into the second aerobic tank. It is configured to be switchable to a second operating state in which it functions as 2 anoxic tanks.

In the organic wastewater treatment apparatus 100, as shown in FIG. 5A, organic wastewater is supplied to the anoxic tank 40, and the organic wastewater and While performing nitrification and denitrification treatment by circulating the mixed liquid with activated sludge, the membrane permeated liquid from the membrane separation device 30 arranged in the first aerobic tank 20 is taken out as treated water, and the oxygen-free tank 40 and a first operating state in which the mixed liquid is sent to the dual-purpose tank 50 for gas treatment, the mixed liquid is further sent from the dual-purpose tank 50 to the sedimentation tank 70, and the solid-liquid separated liquid from the sedimentation tank 70 is taken out as treated water. As shown in FIG. 5(b), the mixture is circulated between the anoxic tank 40, the first aerobic tank 20, and the combined tank 50 for anoxic treatment to perform nitrification and denitrification treatment, while A second operating state is provided in which the membrane permeated liquid from the membrane separation device 30 arranged in the first aerobic tank 20 is taken out as treated water, and the operation is performed so as to switch between the first operating state and the second operating state.

When the amount of organic wastewater is sufficient, the organic wastewater supplied to the anoxic tank 40 is treated in the first operating state in which the combined tank 50 functions as a second aerobic tank for initial adsorption treatment, and the organic wastewater supplied to the anoxic tank 40 is activated. The sludge is circulated with the first aerobic tank 20 in which the membrane separator 30 is arranged to undergo nitrification and denitrification, and the liquid component of the mixed liquid is taken out from the membrane separator 30 as treated water.

Further, part of the mixed liquid is sent from the anoxic tank 40 to the dual-use tank 50 and subjected to initial adsorption treatment as aerobic treatment, and the mixed liquid sent to the sedimentation tank is subjected to solid-liquid separation in the sedimentation tank to treat the supernatant. extracted as water.

When the amount of organic waste water is small, the combined tank 50 is treated in the second operating state functioning as the second anaerobic tank, and the anaerobic tank 40, the first aerobic tank 20, and the combined tank 50 performing the anaerobic treatment are treated. While the mixed solution is circulated between the tanks to perform nitrification and denitrification, the membrane permeated liquid from the membrane separator 30 arranged exclusively in the first aerobic tank 20 is taken out as treated water. Therefore, no treated water is taken out from the sedimentation tank 70 in the second operating state.

In the first operating state, as in the first embodiment, the sludge in the sedimentation tank 70 is returned to the anoxic tank 40 instead of the sludge return route 6 for returning the sludge in the sedimentation tank 70 to the first aerobic tank 20. It is preferable to provide a sludge return route 6A (indicated by a dashed line in FIG. 5(a)).

The BOD remaining in the sedimentation sludge returned to the anoxic tank 40 is effectively used as an organic source for denitrification, and the sludge is transferred to the first aerobic tank 20 and aerobicly treated in a low-load state. As a result, the sludge whose initial adsorption performance has been recovered is supplied to the second aerobic tank 50 .

[Other embodiments]
In each of the above-described embodiments, it is preferable to include a flocculant addition device 80 that adds a flocculant to the sedimentation tank 70 or during transfer of the mixed liquid from the second aerobic tank 50 or the dual-use tank 50 to the sedimentation tank 70. By adding a flocculant, the COD and phosphorus removal effect on the treated water and the sludge sedimentation separation effect can be enhanced.

As shown in FIG. 6, with respect to the above-described first embodiment, the first aerobic tank 20 is arranged in the upper space via the first partition wall 24, and the organic tank 40 is arranged in the lower space. Alternatively, the toxic wastewater treatment device 100 may be constructed. By arranging the first aerobic tank 20 in the upper space of the site where the anoxic tank 40 is arranged, the space utilization rate is increased, and the site of the organic wastewater treatment apparatus can be efficiently utilized. A similar configuration can also be employed in the second or third embodiment described above. In the second embodiment, the anaerobic tank 40 and the mixing tank 60 are arranged in the space below the first aerobic tank 20, or only the anaerobic tank 40 is arranged in the space below the first aerobic tank 20. can be done.

As in the first embodiment, instead of the sludge return route 6 for returning the sludge in the sedimentation tank 70 to the first aerobic tank 20, a sludge return route 6A for returning the sludge in the sedimentation tank 70 to the anoxic tank 40 is provided. It is preferable to have it (indicated by a dashed line in FIG. 6).

The BOD remaining in the sedimentation sludge returned to the anoxic tank 40 is effectively used as an organic source for denitrification, and the sludge is transferred to the first aerobic tank 20 and aerobicly treated in a low-load state. As a result, the sludge whose initial adsorption performance has been recovered is supplied to the second aerobic tank 50 .

Still another organic wastewater treatment device 100 is shown in FIG. In addition to the above-described configuration of FIG. rate can be increased. In this case, it is preferable to arrange the second aerobic tank 50 beside the first aerobic tank 20 and the anoxic tank 40 which are installed in the upper space via the second partition wall 26 .

As in the first embodiment, instead of the sludge return route 6 for returning the sludge in the sedimentation tank 70 to the first aerobic tank 20, a sludge return route 6A for returning the sludge in the sedimentation tank 70 to the anoxic tank 40 is provided. It is preferable to have it (indicated by a dashed line in FIG. 7).

The BOD remaining in the sedimentation sludge returned to the anoxic tank 40 is effectively used as an organic source for denitrification, and the sludge is transferred to the first aerobic tank 20 and aerobicly treated in a low-load state. As a result, the sludge whose initial adsorption performance has been recovered is supplied to the second aerobic tank 50 .

FIG. 8 shows the organic wastewater treatment apparatus 100 shown in FIG. The organic waste water treatment apparatus 100 is shown in which the circulation flow rate from the first aerobic tank 20 to the anoxic tank 40 is set to 7Q so as to be.

Still another organic wastewater treatment apparatus 100 is shown in FIG. 9(a). As shown in FIG. 8, in order to achieve a TN removal rate of 90%, it is necessary to set the circulation flow rate from the first aerobic tank 20 to the anoxic tank 40 to a large value of 7Q. By adopting a circulation type MBR instead of the pair of the first aerobic tank 20 and the anoxic tank 40 and providing a sludge transport route for returning the sludge of the sedimentation tank 70 to each anoxic tank 40, the circulation flow rate can be suppressed. can.

As shown in FIG. 9(b), in the circulating MBR, a plurality of pairs of biological treatment units each including a first aerobic tank 20 and an anoxic tank 40 are connected in series in the sludge transfer direction. , the sludge is returned from the first aerobic tank 20 positioned most downstream to the anoxic tank 40 positioned most upstream.

The organic wastewater supplied to the mixing tank 60 from the raw water supply route 1 is supplied to each anoxic tank 40 together with the activated sludge through the eighth mixed solution route 9, and the mixed solution is supplied through the first mixed solution route 2 to each After being supplied from the anaerobic tank 40 to the first aerobic tank 20 on the downstream side and subjected to aerobic treatment, each first aerobic tank 20 or each anaerobic tank 40 on the downstream side through the second mixed liquid path 3 , denitrification treatment, and further circulated from each anoxic tank 40 to the mixing tank 60 via the sixth mixed solution path 7 .

Such an organic wastewater treatment apparatus 100 is applied to a treatment plant where nitrogen concentration regulation of treated water is relatively loose, for example, TN<10 mg/L.

The above-described embodiment is one aspect of the present invention, and the present invention is not limited by the description, and the specific configuration of each part can be appropriately changed and designed within the scope of the effects of the present invention. Needless to say.

1: raw water supply route 2: first mixed solution route 3: first circulation route
4: Second liquid mixture path 5: Third liquid mixture path 6, 6A: Sludge return path 7: Second circulation path
8: Fourth Mixed Solution Path 9: Eighth Mixed Solution Path 10: Primary Sedimentation Tank 20: Aerobic Tank, First Aerobic Tank 30: Membrane Separator
31: Third circulation route
40: Anoxic tank 50: Combined tank, second aerobic tank 60: Mixing tank 70: Sedimentation tank (final sedimentation tank)
71: Inclined plate
80: Flocculant addition means 90: Disinfection tank 100: Organic waste water treatment device

Claims (12)

A method of operating an organic wastewater treatment apparatus comprising an anoxic tank, a first aerobic tank, a second aerobic tank and a sedimentation tank, comprising:
Organic wastewater is supplied to the anoxic tank, and a mixed solution of organic wastewater and activated sludge is circulated between the anoxic tank and the first aerobic tank to perform nitrification and denitrification treatment. While taking out the membrane permeated liquid from the membrane separation device arranged in the first aerobic tank as treated water,
The mixed liquid is sent from the anoxic tank to the second aerobic tank, and the mixed liquid is sent from the second aerobic tank to the sedimentation tank, and the solid-liquid separation liquid from the sedimentation tank is treated water. A method of operating an organic wastewater treatment system, characterized in that the water is taken out as A method of operating an organic wastewater treatment apparatus comprising an anoxic tank, a first aerobic tank, a second aerobic tank, a mixing tank and a sedimentation tank, comprising:
While supplying organic wastewater to the mixing tank and circulating a mixed liquid of organic wastewater and activated sludge between the mixing tank and the anoxic tank, the anoxic tank and the first aerobic tank While performing nitrification and denitrification treatment by circulating a mixed liquid of organic wastewater and activated sludge between the
The mixed liquid is sent from the mixing tank to the second aerobic tank, the mixed liquid is further sent from the second aerobic tank to the sedimentation tank, and the solid-liquid separated liquid from the sedimentation tank is used as treated water. A method for operating an organic wastewater treatment system, characterized by removing the water. A method of operating an organic wastewater treatment apparatus comprising an anoxic tank, a first aerobic tank, a combined tank and a sedimentation tank, comprising:
Organic wastewater is supplied to the anoxic tank, and a mixed solution of organic wastewater and activated sludge is circulated between the anoxic tank and the first aerobic tank to perform nitrification and denitrification treatment. The membrane permeated liquid from the membrane separation device arranged in the first aerobic tank is taken out as treated water, and the mixed liquid is sent from the anoxic tank to the combined tank for aerobic treatment, and further from the combined tank. a first operating state in which the liquid mixture is sent to the sedimentation tank and the solid-liquid separation liquid from the sedimentation tank is taken out as treated water;
While circulating the mixed solution between the anoxic tank and the first aerobic tank, the mixed solution is circulated between the anoxic tank and the combined tank for performing the anoxic treatment to perform nitrification and denitrification treatment. a second operating state in which the membrane permeated liquid from the membrane separation device arranged in the first aerobic tank is exclusively taken out as treated water while performing
A method of operating an organic wastewater treatment system, comprising: 4. The method of operating an organic wastewater treatment apparatus according to any one of claims 1 to 3, wherein sludge in said sedimentation tank is returned to said first aerobic tank. 4. The method of operating an organic wastewater treatment system according to any one of claims 1 to 3, wherein the sludge in said sedimentation tank is returned to said anoxic tank. 6. The organic organic material according to any one of claims 1 to 5, wherein a flocculant is added to the sedimentation tank or during transfer of the mixed liquid from the second aerobic tank or the combined tank to the sedimentation tank. A method of operating a wastewater treatment system. An anoxic tank for denitrification, a first aerobic tank for nitrification, equipped with a membrane separator for extracting treated water as membrane permeate, a second aerobic tank for initial adsorption, a sedimentation tank, a raw water supply path for supplying organic wastewater to the anoxic tank; a first mixed solution path for sending a mixture of organic wastewater and activated sludge from the anoxic tank to the first aerobic tank; a first circulation route for circulating the mixed solution from the air tank to the anoxic tank; a second mixed solution route for sending the mixed solution from the second aerobic tank to the sedimentation tank; and a third liquid mixture path for sending the liquid mixture to the gas tank. An anoxic tank for denitrification, a first aerobic tank for nitrification provided with a membrane separator for taking out treated water as membrane permeate, a second aerobic tank for initial adsorption, a mixing tank, a sedimentation tank, a raw water supply route for supplying organic wastewater to the mixing tank, a first circulation route for circulating a mixture of organic wastewater and activated sludge from the first aerobic tank to the anoxic tank; a second circulation route for circulating the mixed solution from the anoxic tank to the mixing tank; a second mixed solution route for sending the mixed solution from the second aerobic tank to the sedimentation tank; and a fourth liquid mixture path for sending the liquid mixture to the gas tank. An anoxic tank for denitrification, a first aerobic tank for nitrification, equipped with a membrane separation device for taking out treated water as a membrane permeate, a combined tank, a sedimentation tank, and organic wastewater to the anoxic tank. a first mixed solution route for sending a mixed solution of organic wastewater and activated sludge from the anoxic tank to the first aerobic tank; and a mixed solution for sending the mixed solution from the combined tank to the sedimentation tank. a second mixed solution route, a third mixed solution route for sending the mixed solution from the anoxic tank to the combined tank, a first circulation route for circulating the mixed solution from the first aerobic tank to the anoxic tank, a third circulation path for circulating the mixed liquid from the anoxic tank to the dual-purpose tank;
A first operating state in which the third circulation path is opened and the combined tank functions as a second aerobic tank, and the third circulation path is closed and the combined tank functions as a second anoxic tank. An organic wastewater treatment apparatus characterized by being configured to be switchable to and from a second operating state. 10. The organic wastewater treatment apparatus according to any one of claims 7 to 9, wherein said first aerobic tank is arranged in an upper space via a first partition wall, and said anoxic tank is arranged in a lower space. 11. The organic wastewater treatment apparatus according to claim 10, wherein said sedimentation tank is arranged in a space below said anoxic tank via a second partition wall. 12. The organic wastewater treatment apparatus according to any one of claims 7 to 11, further comprising a sludge return route for returning sludge from said sedimentation tank to said first aerobic tank.

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