JP4380290B2 - Nitrogen-containing organic wastewater treatment method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for treating nitrogen-containing organic wastewater, and more particularly to a treatment method and apparatus for aerobically treating nitrogen-containing organic wastewater such as human waste to remove organic substances and perform nitrification denitrification. is there.

  As a treatment method and apparatus for nitrogen-containing organic wastewater such as human waste, nitrogen-containing organic wastewater is mixed with nitrification liquid in a primary denitrification tank to biologically denitrify, decompose organic matter, and nitrify in a primary nitrification tank. A part of the nitrification liquid is returned to the primary denitrification tank, and the remainder is introduced into the secondary denitrification tank for denitrification, re-aerated in the re-aeration tank, and then separated by precipitation in the settling tank, and a part of the sludge is removed. A method and an apparatus for returning to the first denitrification tank are well known (for example, Patent Document 1). Further, in the above processing method and apparatus, a method of installing a membrane separation device for membrane separation in an aerated state instead of a precipitation tank and applying membrane separation for separation of sludge and treated water is well known (for example, Patent Documents). 2).

  FIG. 2 is a flowchart showing a conventional nitrogen-containing organic wastewater treatment method and apparatus to which these are applied. The primary denitrification tank 1 constituting the processing apparatus 10 includes a plurality of stages of a first denitrification tank 1a, a second denitrification tank 1b, a third denitrification tank 1c, and a fourth denitrification tank 1d, and the primary nitrification tank 2 has a plurality of stages. The first nitrification tank 2a, the second nitrification tank 2b, the third nitrification tank 2c, and the fourth nitrification tank 2d are arranged alternately, followed by the secondary denitrification tank 3, the re-aeration tank 4, and the membrane separation tank 5. The pump pit 6 is arranged, and the whole communicates with the series so that the liquid flows from the primary denitrification tank 1a side to the pump pit 6 side.

The raw water channel 11 branches into branch channels 11a, 11b, 11c, and 11d, and communicates with the first denitrification tank 1a, the second denitrification tank 1b, the third denitrification tank 1c, and the fourth denitrification tank 1d, respectively. The air supply path 12 is branched into branch paths 12a, 12b, 12c, 12d, and 12e, and the first nitrification tank 2a, the second nitrification tank 2b, the third nitrification tank 2c, the fourth nitrification tank 2d, and the re-aeration tank 4 respectively. The air diffusers 7a, 7b, 7c, 7d, and 7e provided at the lower part of the air diffuser are communicated. The secondary denitrification tank 3 does not communicate with the raw water channel 11 but communicates with the substrate supply channel 13.

  A membrane module 8 is disposed in the membrane separation tank 5, and an air supply path 14 communicates with an air diffuser 7f provided below the membrane module 8. In the membrane module 8, the concentrated liquid chamber 8b and the permeated liquid chamber 8c are partitioned by the separation membrane 8a, the concentrated liquid chamber 8b communicates with the membrane separation tank 5, and the permeated liquid chamber 8c communicates with the treatment water channel 15 having the pump P1. is doing. A nitrification liquid circulation path 16 having a pump P2 communicates with the first denitrification tank 1a of the primary denitrification tank 1 from the fourth nitrification tank 2d at the final stage of the primary nitrification tank 2. The first return passage 17 having the pump P3 from the pump pit 6 communicates with the first denitrification tank 1a of the primary denitrification tank 1, and the surplus sludge passage 18 having the pump P4 communicates from the pump pit 6 outside the system. .

  In the treatment apparatus 10, raw water (nitrogen-containing organic waste water) is distributed from the raw water channel 11 to the branch channels 11 a, 11 b, 11 c, and 11 d, and the first denitrification tank 1 a, second denitrification tank 1 b, and third respectively. The denitrification tank 1c and the fourth denitrification tank 1d are supplied, and the air is distributed from the air supply path 12 to the branch paths 12a, 12b, 12c, 12d, and 12e, and the first nitrification tank 2a, the second nitrification tank 2b, Aeration is performed by supplying to the aeration devices 7a, 7b, 7c, 7d, and 7e provided at the lower part of the third nitrification tank 2c, the fourth nitrification tank 2d, and the re-aeration tank 4. Then, the nitrification liquid is circulated from the fourth nitrification tank 2d at the final stage of the primary nitrification tank 2 from the nitrification liquid circulation path 16 to the first denitrification tank 1a of the primary denitrification tank 1 by the pump P2, and is concentrated in the pump pit 6. Is returned to the first denitrification tank 1a of the primary denitrification tank 1 from the first return path 17 by the pump P3 and processed.

  In the first denitrification tank 1a, nitrogen-containing organic wastewater is mixed with the circulating nitrification liquid and the return sludge and kept in an anaerobic state to reduce nitric acid or nitrite nitrogen to nitrogen gas by the action of denitrifying bacteria, and biological desorption. Nitrogen is performed, and at the same time, organic matter in the raw water is decomposed as a substrate, and primary denitrification is performed. The denitrification liquid in the first denitrification tank 1a enters the first nitrification tank 2a, decomposes residual organic substances by aeration, and nitrifies ammoniacal nitrogen in the raw water into nitric acid or nitrite nitrogen by the action of nitrifying bacteria. The nitrification liquid in the first nitrification tank 2a enters the second denitrification tank 1b and is similarly denitrified, and then sequentially the second nitrification tank 2b, the third denitrification tank 1c, the third nitrification tank 2c, the fourth denitrification tank 1d and the first 4 Enters nitrification tank 2d and undergoes nitrification or denitrification.

Thus, primary denitrification is performed in the first denitrification tank 1a, the second denitrification tank 1b, the third denitrification tank 1c, and the fourth denitrification tank 1d of the plurality of stages of the primary denitrification tank 1, and the primary nitrification tank 2 Primary nitrification is performed in the first nitrification tank 2a, the second nitrification tank 2b, the third nitrification tank 2c, and the fourth nitrification tank 2d. Most of the primary nitrification liquid in the fourth nitrification tank 2d circulates as a circulation nitrification liquid to the first denitrification tank 1a, but a part enters the secondary denitrification tank 3 where nitrogen-containing organic waste water is mixed. The remaining nitric acid or nitrite nitrogen is removed by mixing with a substrate substantially free of nitrogen such as methanol supplied from the substrate supply path 13 to perform secondary denitrification. Is called. The secondary denitrification liquid in the secondary denitrification tank 3 enters the re-aeration tank 4, where the remaining organic matter is decomposed by re-aeration.

  Thus, by repeating primary denitrification, primary nitrification, secondary denitrification, and re-aeration alternately, organic substances and ammoniacal nitrogen contained in raw water (nitrogen-containing organic waste water) are removed. Conventionally, in Patent Document 1, for example, the re-aeration liquid in the re-aeration tank 4 is precipitated and separated in the precipitation tank, and a part of the separated sludge is returned to the first denitrification tank 1a, but in order to increase the concentration of the separated sludge, For example, in Patent Document 2, instead of a precipitation tank, a membrane separation device that separates membranes in an aerated state is installed, and membrane separation is applied to separation of sludge and treated water. FIG. 2 shows such a treatment device. ing.

  That is, in FIG. 2, the re-aeration liquid in the re-aeration tank 4 is introduced into the membrane separation tank 5, and air is supplied from the air supply path 14 to the air diffuser 7f to aerate the re-aeration liquid of the secondary denitrification liquid. In the state, membrane separation is performed by the membrane module 8. In the membrane module 8, the re-aerated liquid containing sludge is membrane-separated by the separation membrane 8a, and the permeate that has permeated through the separation membrane 8a is taken out from the permeate chamber 8c through the treatment water channel 15 as treatment water by the pump P1. The concentrated liquid in the concentrated liquid chamber 8b is dispersed in the membrane separation tank 5 while being prevented from adhering to the separation membrane 8a by aeration by the air diffuser 7f. The concentrated liquid in the membrane separation tank 5 enters the pump pit 6, and a part of the concentrated liquid is returned to the first denitrification tank 1 a of the primary denitrification tank 1 through the first return path 17 by the pump P 3 and returned to the other. A part is discharged out of the system through the excess sludge passage 18 by the pump P4 as excess sludge.

In the treatment as described above, even if nitrogen is almost completely removed in the secondary denitrification tank 3, nitrogen may be detected in the treated water (permeated liquid of the separation membrane 8a). For example, when a precipitation tank is used as the solid-liquid separation tank, the TN of the treated water (separated liquid) can be lowered by selecting the solid-liquid separation conditions, but when the membrane separation tank 5 is used, It is difficult to lower the TN of water, and it is difficult to stably maintain the TN of treated water at, for example, 10 mg / L or less. When the cause was investigated, by aeration in the membrane separation tank 5, the nitrogen component was eluted in the concentrate by decomposition or metabolism of organic nitrogen compounds in the sludge, and this was nitrified to NO _x -N and treated. Presumed to be mixed in water.

In order to prevent the increase in the TN of the treated water, the decomposition can be advanced as much as possible by increasing the amount of oxygen supplied to the nitrification tank. However, if the amount of oxygen supplied is increased, there are obstacles such as foaming. Can't get enough effect. In addition, by increasing the amount of returned sludge, the MLSS of the membrane separation tank can be reduced, or the residence time of the sludge in the membrane separation tank can be shortened to reduce the generation of NO _x -N. When the excess sludge is extracted from the tank and dehydrated, the decrease in the sludge concentration deteriorates the dehydration effect.

In Patent Document 1, since non-diluted human waste is subjected to primary denitrification and nitrification, and then diluted with water to perform secondary denitrification, in order to obtain a sludge concentration necessary for secondary denitrification and re-aeration, precipitation is performed. Part of the separated sludge in the tank is returned to the secondary denitrification tank, but here it is precipitation separation, so whether TN of treated water increases due to decomposition or metabolism of organic nitrogen compounds in the sludge It is unclear, and it has not been clarified whether TN of treated water is lowered by returning a part of the separated sludge to the secondary denitrification tank.
Japanese Patent Publication No. 1-16559 JP-A-11-28468

  The subject of the present invention is a simple configuration and operation without causing foaming in the nitrification tank or deterioration of the dehydration effect in nitrification denitrification treatment in which membrane separation in an aerated state is applied to separation of sludge and treated water. It is intended to provide a method and apparatus for treating nitrogen-containing organic waste water that can reduce the nitrogen concentration in treated water and obtain good treated water.

The present invention is the following nitrogen-containing organic wastewater treatment method and apparatus.
(1) A primary denitrification step in which nitrogen-containing organic wastewater is mixed with nitrification liquid to biologically denitrify and decompose organic matter;
A primary nitrification step of bionitrating the primary denitrification solution;
A secondary denitrification step in which the primary nitrification solution is mixed with a substrate substantially free of nitrogen to biodenitrify;
A re-aeration process for re-aeration of the secondary denitrification liquid;
A membrane separation step of separating the re-aerated liquid in an aerated state;
A first return step for returning a part of the concentrate of the membrane separation step to the primary denitrification step;
A second returning step of returning the other part of the concentrate of the membrane separation process in the secondary denitrification step seen including,
The primary denitrification process and the primary nitrification process are performed in multiple steps alternately. Nitrogen-containing organic wastewater treatment method, which is a nitrification process (However, in the secondary denitrification process, nitrogen organic wastewater is mixed. Except how to do that.)
(2) A primary denitrification tank that mixes nitrogen-containing organic wastewater with nitrification liquid to biologically denitrify and decompose organic matter;
A primary nitrification tank for bionitrating the primary denitrification liquid;
A secondary denitrification tank for biological denitrification by mixing the primary nitrification solution with a substrate substantially free of nitrogen,
A re-aeration tank for re-aeration of the secondary denitrification liquid;
A membrane separation tank for separating a re-aerated liquid in an aerated state;
A first return path for returning a part of the concentrate in the membrane separation tank to the primary denitrification tank;
A second return path for returning a portion of the other of the concentrate of the membrane separation tank to the secondary denitrification seen including,
The primary denitrification tank and the primary nitrification tank are a step denitrification tank and a nitrification tank, each of which comprises a plurality of stages. A treatment apparatus for nitrogen-containing organic wastewater (however, a device for mixing nitrogen organic wastewater in the secondary denitrification tank) except for.).

  The nitrogen-containing organic waste water to be treated in the present invention is waste water containing nitrogen and organic matter, and may contain other elements and inorganic matter. Nitrogen includes ammonia nitrogen, nitric acid or nitrite nitrogen, organic nitrogen, etc., and most nitrogen-containing organic wastewater contains ammonia nitrogen and organic nitrogen. Such nitrogen-containing organic wastewater includes sewage, industrial wastewater, food wastewater, human waste and the like.

In the method for treating nitrogen-containing organic waste water according to the present invention, the nitrogen-containing organic waste water is mixed with a nitrification liquid in the primary denitrification step to biologically denitrify and decompose organic matter, and in the primary nitrification step, the primary denitrification step is performed. The liquid is biologically nitrified without mixing nitrogen-containing organic wastewater in the secondary denitrification process, and the primary nitrification liquid is mixed with a substrate that does not substantially contain nitrogen for biological denitrification. The secondary denitrification liquid is subjected to membrane separation in the aerated state, a part of the concentrated liquid in the membrane separation process is returned to the primary denitrification process in the first return process, and the concentrated liquid in the membrane separation process is returned in the second return process. The other part is returned to the secondary denitrification process to treat nitrogen-containing organic wastewater. In the case where foaming occurs due to aeration, it is preferable to dilute the water to be treated in advance and perform the treatment without diluting in the middle.

By employing a plurality of steps performed steps denitrification and step nitrification step alternating primary denitrification step and the primary nitrification step Waso respectively process, it is possible to process the waste water containing efficiently nitrogen and organic preferred. In this case, raw water (nitrogen-containing organic wastewater) is dispensed into the primary denitrification process at each stage to perform denitrification, and the denitrification liquid is sent to the primary nitrification process at the next stage for nitrification. It is preferable that the nitrification liquid on the final floor is sent to the primary denitrification process at the next stage and circulated to the primary denitrification process at the first stage. A re-aeration process is provided between the secondary denitrification process and the membrane separation process to re-aerate the secondary denitrification liquid. In the membrane separation step, the re-aerated liquid is maintained in the aerated state to perform membrane separation . The concentrated liquid in the membrane separation process is partially returned to the primary denitrification process in the first return process, and the other part is returned to the secondary denitrification process in the second return process. Part of it can be discharged out of the system as excess sludge.

A treatment apparatus for use in the above-described method for treating nitrogen-containing organic wastewater comprises a primary denitrification tank that mixes nitrogen-containing organic wastewater with a nitrification liquid for biological denitrification and decomposes organic matter, and primary denitrification liquid. A primary nitrification tank for biological nitrification, a secondary denitrification tank for biological denitrification by mixing the primary nitrification liquid with a substrate substantially free of nitrogen, and a re-aeration tank for re-aeration of the secondary denitrification liquid A membrane separation tank for membrane separation of the re-aerated liquid in an aerated state, a first return path for returning a part of the concentrated liquid in the membrane separation tank to the primary denitrification tank, and another concentrated liquid in the membrane separation tank And a second return path for returning the part to the secondary denitrification tank.

In the above processing apparatus, a primary denitrification tank and the primary nitrification reactor is a combination of the respective steps denitrification tank and nitrification tank to perform multiple steps alternately. In this case, raw water (nitrogen-containing organic waste water) is dispensed into the primary denitrification tank at each stage for denitrification, and the denitrification liquid is sent to the primary nitrification tank at the next stage for nitrification. It is preferable that the nitrification liquid on the final floor is sent to the primary denitrification tank of the stage and is circulated to the primary denitrification tank of the first stage. Also between the secondary denitrification tank and the membrane separation tank, re-aeration tank is provided to re-aeration secondary denitrified liquid. When returning the concentrated liquid (return sludge) of the membrane separation tank to a primary denitrification tank comprising a plurality of tanks, it is preferable to connect the first return path to the first primary denitrification tank.

  As the separation membrane used in the membrane separation tank, a permeable membrane such as an MF membrane or a UF membrane usually used for solid-liquid separation is used. Examples of the separation membrane include a flat membrane, a tubular membrane, and a hollow fiber membrane. Such a separation membrane is preferably used as a membrane module in which the concentrate chamber and the permeate chamber are partitioned by the separation membrane. As such a membrane module, a pressure type, immersion type or the like is used depending on installation conditions. The concentrated liquid in the membrane separation tank may be returned from the membrane separation tank to the primary denitrification tank and / or the secondary denitrification tank. Alternatively, a pump pit may be provided and returned from the pump pit. The return means may use a dedicated pump or the like, or may branch from the return sludge path or the excess sludge path. The surplus sludge path is provided so as to draw surplus sludge from the membrane separation tank or pump pit and send it to the sludge treatment.

In the nitrogen-containing organic wastewater treatment method of the present invention, primary denitrification, primary nitrification, secondary denitrification, and re-aeration are performed in the same manner as in the conventional nitrification denitrification method. As a nitrification denitrification method, a standard denitrification method, a high load treatment method, a septic tank compatible method, or the like can be adopted . Membrane separation of the re- aerated liquid in the aerated state is the same as the conventional nitrification denitrification method that employs membrane separation, but denitrification is performed by circulating the concentrated liquid from the membrane separation process to the secondary denitrification process. Thus, the nitrogen concentration of the treated water can be reduced. Since the MLSS of the concentrate is increased by performing membrane separation in the membrane separation tank, a part of the concentrate is returned to the primary denitrification step as return sludge, and the remainder is dehydrated as excess sludge.

  In order to efficiently perform the dehydration treatment, it is preferable to perform the membrane separation while maintaining the concentrated liquid in the membrane separation step at a high concentration. If such a concentrated solution is simply put in a membrane separation tank and separated into membranes, it becomes anaerobic and organic substances are eluted, the quality of treated water deteriorates, and sludge adheres to the membrane surface and membrane separation efficiency decreases. In order to prevent this, membrane separation is performed in an aerated state. In general, it is considered that maintaining an aerobic state by aeration will decompose organic substances and improve the quality of treated water.

  However, if the aeration of the concentrated liquid is continued in a state where the sludge concentration is high, for example, 10,000 to 20,000 mg / L as MLSS, nitrogen components are contained in the concentrated liquid due to decomposition or metabolism of organic nitrogen compounds contained in the sludge. It is estimated that it will be nitrified to nitric acid or nitrite nitrogen, and even if nitrogen is almost completely removed in the secondary denitrification process, nitrogen is detected in the concentrate and this nitrogen component is treated. It may be mixed with water (permeated liquid of the separation membrane) to deteriorate the quality of treated water.

Conveniently, the nitrogen in the concentrate is converted to nitric acid or nitrite nitrogen by aeration, so that a part of the concentrate can be denitrified by circulating it in the secondary denitrification process, and the nitrogen concentration of not lower reaerated liquid circulated to the membrane separation process, it is possible to reduce the nitrogen concentration in the concentrate. Thus, in order to efficiently perform the dehydration treatment, even if the membrane separation is carried out while maintaining the concentrated liquid in the membrane separation step at a high concentration, the nitrogen concentration in the concentrated liquid is kept low and the nitrogen concentration in the treated water is lowered. can do.

  For this reason, it is not necessary to increase the oxygen supply amount of the nitrification tank or to lower the MLSS of the membrane separation tank, and neither the foaming in the nitrification tank nor the dehydration effect is deteriorated. The return rate of the concentrate to the secondary denitrification step can be changed depending on the nitrogen concentration of the concentrate in the membrane separation tank. In this case, if the return rate of the concentrate is selected so that the nitrogen concentration of the concentrate (treated water) is maintained at, for example, 3 to 7 mg / L, the treated water having the nitrogen concentration can be obtained. Substrate substantially free of nitrogen, such as methanol, required for denitrification of the concentrate can be accommodated by increasing the amount of substrate supplied to the secondary denitrification step. There is no need to dilute with water in the secondary denitrification step in which the concentrate is returned or in the steps before and after.

According to the present invention, as the primary denitrification process and the primary nitrification process, step denitrification and nitrification processes that alternately perform a plurality of stages are adopted, and the nitrogen-containing organic waste water is used as the nitrification liquid in the primary denitrification process. Without mixing and biological denitrification, organic matter is decomposed, the primary denitrification liquid is bionitrated in the primary nitrification process, and the primary nitrification liquid is not mixed with nitrogen-containing organic wastewater in the secondary denitrification process. Biological denitrification by mixing with a substrate substantially free of nitrogen, re-aeration of the secondary denitrification liquid in the re-aeration process , membrane separation of the re-aeration liquid in the aerated state in the membrane separation process, and first return In the process, a part of the concentrated liquid in the membrane separation process is returned to the primary denitrification process, and in the second return process, another part of the concentrated liquid in the membrane separation process is returned to the secondary denitrification process. Therefore, even in nitrification denitrification treatment that applies membrane separation in the aerated state for separation of sludge and treated water, Without causing such foaming or the dewatering effect deterioration of a bath, by lowering the nitrogen concentration in the treated water with a simple structure and operation, it is possible to obtain satisfactory treated water.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing a method and apparatus for treating nitrogen-containing organic wastewater according to an embodiment of the present invention. Since the processing apparatus 10 in FIG. 1 is configured in substantially the same manner as the processing apparatus 10 in FIG. 2, the same or corresponding parts are denoted by the same reference numerals and description thereof is omitted. The processing apparatus 10 in FIG. 1 differs from the processing apparatus 10 in FIG. 2 in that a second return path 21 having a pump P5 communicates with the secondary denitrification tank 3 from the lower part of the membrane separation tank 5.

  The processing method of nitrogen-containing organic waste water by the processing apparatus 10 of FIG. 1 is performed in substantially the same manner as the processing method of nitrogen-containing organic waste water by the processing apparatus 10 of FIG. That is, primary denitrification in the primary denitrification tank 1, primary nitrification in the primary nitrification tank 2, secondary denitrification in the secondary denitrification tank 3, re-aeration in the re-aeration tank 4, membrane separation in the membrane separation tank 5, and nitrification The circulation of the nitrification liquid from the liquid circulation path 16, the return of a part of the concentrated liquid from the first return path 17, the discharge of the excess sludge from the excess sludge path 18, and the like are performed in substantially the same manner as in FIG.

  In the processing method of nitrogen-containing organic wastewater by the processing apparatus 10 of FIG. 1, another part of the concentrated liquid in the membrane separation process in the membrane separation tank 5 is transferred from the second return path 21 to 2 in the secondary denitrification tank 3. By returning to the next denitrification step and performing denitrification, the nitrogen concentration of the treated water can be lowered. In the membrane separation process, the concentrated solution in the membrane separation tank 5 is maintained at a high concentration to perform membrane separation. When such a concentrated solution is separated into a membrane in an aerated state, it is contained in sludge as described above. It is presumed that the nitrogen component is eluted into the concentrate by decomposition or metabolism of the organic nitrogen compound, and this is presumed to be nitrified into nitric acid or nitrite nitrogen, and the nitrogen concentration in the concentrate increases.

  Since nitrogen in the concentrate is converted to nitric acid or nitrite nitrogen by aeration, when a part of the concentrate is returned to the secondary denitrification tank 3, it flows from the fourth nitrification tank 2d of the primary denitrification tank 1 It can be denitrified by biological denitrification along with the next nitrification solution. The substrate substantially free of nitrogen such as methanol required here can be dealt with by increasing the amount of substrate supplied from the substrate supply path 13. By denitrifying the concentrated liquid to be returned in this way, the denitrified liquid having a low nitrogen concentration is re-aerated in the re-aeration tank 4, and the re-aerated liquid having a low nitrogen concentration is circulated to the membrane separation tank 5. The nitrogen concentration inside can be kept low. For this reason, even if MLSS of the concentrate of the membrane separation tank 5 is maintained at a high concentration and membrane separation is performed, the nitrogen concentration in the concentrate can be kept low and the nitrogen concentration of the treated water can be lowered.

  In the above-described treatment, it is not necessary to increase the oxygen supply amount in the primary nitrification tank 2, the re-aeration tank 4, the membrane separation tank 5, and the like, so that foaming failure and other adverse effects are not exerted on the nitrification denitrification treatment. Moreover, since it is not necessary to lower MLSS of the membrane separation tank 5, the dehydration effect is not deteriorated. For this reason, the nitrogen concentration in the treated water can be lowered by a simple configuration and operation, and good treated water can be obtained.

In Figure 1, in order to perform aeration at different conditions re aeration tank 4 and the membrane separation tank 5, it intends rows aeration re aeration tank 4 is provided separately from the membrane separation tank 5. Although the pump pit 6 can be omitted, it is preferable to provide the pump pit 6 to return the concentrated liquid in order to prevent fluctuations in the liquid level of the membrane separation tank 5 due to the return of the concentrated liquid. In this case, a part of the concentrated liquid can be circulated from the pump pit 6 to the secondary denitrification tank 3, and a part of the concentrated liquid is passed from the first return path 17 through the branch path (not shown). It may be circulated.

Comparative Example 1:
In the treatment apparatus 10 of FIG. 2, diluted urine obtained by diluting raw urine 1.3 times with diluted water (BOD 5100 mg / L, NH ₄ -N: 530 mg / L, NO _x -N: 0 mg / as nitrogen-containing organic waste water). L, TN: 1000 mg / L) is used as raw water, the raw water is supplied at 100 KL / D to perform biological nitrification denitrification, and membrane membrane 8 is subjected to membrane separation using a flat membrane immersion module. The treatment was performed without returning the concentrated liquid in the membrane separation tank 5 to the secondary denitrification tank 3. The circulation rate of the primary nitrification liquid was 360 m ³ / day, and the amount of sludge returned to the first denitrification tank was 270 m ³ / day.

Example 1:
1, the biological nitrification denitrification process and the membrane separation process are performed in the same manner as in Comparative Example 1, and the circulation rate of the primary nitrification liquid is 360 m ³ / day, and the return amount of the concentrated liquid to the first denitrification tank Was 97 m ³ / day, and the amount of the concentrated liquid returned to the secondary denitrification tank ³ was 480 m ³ / D.

Table 1 shows the water quality of each step of Comparative Example 1 and Example 1. From the results shown in Table 1, it can be seen that high-quality treated water having a low total nitrogen concentration can be obtained by returning a part of the concentrated liquid in the membrane separation tank 5 to the secondary denitrification tank 3 for treatment.

  Nitrogen-containing organic wastewater such as human waste is aerobically treated to remove organic substances and to be used in a treatment method and apparatus for performing nitrification denitrification.

It is a flowchart which shows the processing method and apparatus of the nitrogen-containing organic waste_water | drain by embodiment of this invention. It is a flowchart which shows the processing method and apparatus of the conventional nitrogen-containing organic waste_water | drain.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Primary denitrification tank 1a 1st denitrification tank 1b 2nd denitrification tank 1c 3rd denitrification tank 1d 4th denitrification tank 2 Primary nitrification tank 2a 1st nitrification tank 2b 2nd nitrification tank 2c 3rd nitrification tank 2d 4th nitrification tank 3 Secondary denitrification tank 4 Re-aeration tank 5 Membrane separation tank 6 Pump pit 7a, 7b ... Aeration device 8 Membrane module 8a Separation membrane 8b Concentrated liquid chamber 8c Permeate chamber 10 Treatment device 11 Raw water channels 11a, 11b, 11c 11d Branch path 12, 14 Air supply path 12a, 12b, 12c, 12d, 12e Branch path 13 Substrate supply path 15 Treatment water path 16 Nitrification liquid circulation path 17 First return path 18 Surplus sludge path 21 Second return path P1 , P2 ... Pump

Claims (2)

A primary denitrification step in which nitrogen-containing organic wastewater is mixed with a nitrification solution to biologically denitrify and decompose organic matter;
A primary nitrification step of bionitrating the primary denitrification solution;
A secondary denitrification step in which the primary nitrification solution is mixed with a substrate substantially free of nitrogen to biodenitrify;
A re-aeration process for re-aeration of the secondary denitrification liquid;
A membrane separation step of separating the re-aerated liquid in an aerated state;
A first return step for returning a part of the concentrate of the membrane separation step to the primary denitrification step;
A second returning step of returning the other part of the concentrate of the membrane separation process in the secondary denitrification step seen including,
The primary denitrification process and the primary nitrification process are performed in multiple steps alternately. Nitrogen-containing organic wastewater treatment method, which is a nitrification process (However, in the secondary denitrification process, nitrogen organic wastewater is mixed. Except how to do that.) A primary denitrification tank that mixes nitrogen-containing organic wastewater with a nitrification solution for biological denitrification and decomposes organic matter;
A primary nitrification tank for bionitrating the primary denitrification liquid;
A secondary denitrification tank for biological denitrification by mixing the primary nitrification solution with a substrate substantially free of nitrogen,
A re-aeration tank for re-aeration of the secondary denitrification liquid;
A membrane separation tank for separating a re-aerated liquid in an aerated state;
A first return path for returning a part of the concentrate in the membrane separation tank to the primary denitrification tank;
A second return path for returning a portion of the other of the concentrate of the membrane separation tank to the secondary denitrification seen including,
The primary denitrification tank and the primary nitrification tank are stepped denitrification tanks and nitrification tanks that are alternately operated in multiple stages. A nitrogen organic wastewater treatment device (however, in the secondary denitrification tank, a device that mixes nitrogen organic wastewater is used. except.).

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