JP6880894B2 - Wastewater treatment method with ANAMMOX process - Google Patents

Description

The present invention relates to a method for biologically treating nitrogen-containing organic wastewater, and particularly to a wastewater treatment method having an ANAMMOX process.

In the ANAMMOX process, ANAMMOX bacteria, which are autotrophic microorganisms that use ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, are used to react ammoniacal nitrogen with nitrite nitrogen for denitrification. To do. In the ANAMMOX reaction, as shown in Formula 1, ammoniacal nitrogen and nitrite nitrogen react at a ratio of 1: 1.32. Therefore, the nitrogen treatment technique using the ANAMMOX reaction oxidizes about half of the ammoniacal nitrogen in the water to be treated to nitrite nitrogen and subject it to the ANAMMOX reaction.
1.0NH ₄ ⁺ + 1.32NO ₂ ⁻ + 0.066HCO ₃ ⁻ → 1.02N ₂ + 0.26NO ₃ ⁻ + 0.066CH ₂ O _0.5 N _0.15 + 2.03H ₂ O + 0.13OH ⁻ … (1)

The ANAMMOX process includes a two-tank type ANAMMOX process in which the nitrite nitrification treatment and the ANAMMOX treatment are performed in separate tanks, and a one-tank type ANAMMOX process in which the nitrite-type nitrification treatment and the ANAMMOX treatment are simultaneously performed in the same tank.

In any ANAMMOX process, the nitrite nitrogen concentration in the ANAMMOX reaction vessel is usually maintained at a low concentration (100 mg-N / L or less) due to the consumption of ANAMMOX bacteria, but fluctuations in operating conditions (water temperature, pH). , Nitrogen concentration, Ammonia nitrogen in the inflow water of the ANAMMOX tank: Nitrite nitrogen ratio, etc.) When the activity of ANAMMOX bacteria decreases, nitrite nitrogen cannot be consumed in the ANAMMOX reaction, and the nitrite in the tank becomes nitrite. Nitrogen concentration may be high.

While nitrite nitrogen is a substrate for ANAMMOX bacteria, it is known to inhibit the activity of ANAMMOX bacteria, and when the concentration of nitrite nitrogen in the tank increases, the inhibition reduces the activity of ANAMMOX bacteria. In addition, a vicious cycle occurs in which the concentration of nitrite nitrogen increases. Therefore, when nitrite nitrogen accumulates in the ANAMMOX reaction tank, it is desirable to promptly reduce the nitrite nitrogen concentration in the tank.

For this purpose, for example, it is conceivable to supply raw water to the ANAMMOX reaction tank to dilute the liquid in the reaction tank to reduce the concentration of nitrite nitrogen in the reaction tank. However, in this way, wastewater unsuitable for discharge, which contains a high concentration of nitrite nitrogen, is generated from the reaction vessel.

Therefore, when the nitrite nitrogen concentration in the ANAMMOX tank becomes high, when taking measures to reduce the nitrite nitrogen concentration in the reaction tank, the nitrite nitrogen accumulated in the reaction tank is used. It is necessary to remove it without discharging it to the outside of the system.

In addition, Japanese Patent Application Laid-Open No. 2003-39092 describes that there is a problem of inactivation of ANAMMOX bacteria due to high concentration of nitrite in the two-step treatment of batch type nitrite formation → ANAMMOX denitrification.

Further, regarding the solution of the problem of inactivation of ANAMMOX bacteria, JP-A-2003-24984 and JP-A-2003-47990 describe that the decrease in activity and the decrease in treatment efficiency are detected to control the flow rate of raw water, and JP-A-2003- 33791 describes that the activity is restored by adding hydrazine when the activity is decreased or deactivated, and Japanese Patent Application Laid-Open No. 2006-122839 describes that the circulation ratio is adjusted by the amount of nitrogen gas generated or when the predetermined value is exceeded. It is stated to sound an alarm.

Japanese Unexamined Patent Publication No. 2003-39092 JP-A-2003-24984 Japanese Unexamined Patent Publication No. 2003-47990 Japanese Unexamined Patent Publication No. 2003-333791 Japanese Unexamined Patent Publication No. 2006-122839

The present invention is a biological treatment method having an ANAMMOX process for treating nitrogen-containing organic wastewater, when the nitrite nitrogen concentration in the ANAMMOX reaction vessel becomes high, the nitrite in the reaction vessel. It is an object of the present invention to provide a wastewater treatment method having an ANAMMOX process capable of rapidly lowering the nitrogen concentration and treating nitrite nitrogen without discharging it from the system.

The gist of the present invention is as follows.

[1] A step of methane fermentation treatment of raw water in a methane fermentation tank, and a nitrite-type nitrification treatment and an ANAMMOX treatment by introducing the digested liquid from the methane fermentation tank into the ANAMMOX reaction tank and aerating the reaction tank. In a wastewater treatment method having an ANAMMOX process having a step performed in-house, when the nitrite nitrogen concentration in the ANAMMOX reaction tank or its index value becomes higher than a predetermined value, the aeration is stopped and the ANAMMOX is stopped. A sedimentation step of precipitating granules or carriers in the reaction vessel, and then a return step of returning the nitrite nitrogen-containing water of the ANAMMOX reaction vessel to the methane fermentation vessel or its upstream side with the aeration stopped. A wastewater treatment method comprising an ANAMMOX process, characterized in that

[2] In [1], the ANAMMOX reaction tank is a continuous reaction tank to which digestive juice is continuously supplied, and in the sedimentation step, the outflow of treated water from the ANAMMOX reaction tank is stopped. At the same time, the supply of the digestive juice to the ANAMMOX reaction tank was stopped, and in the return step, the supply of the digestive juice was restarted with the outflow of the treated water stopped, and after the return step, aeration was performed in the ANAMMOX reaction tank. A wastewater treatment method comprising an ANAMMOX process, which comprises a step of returning the nitrite nitrogen-containing water of the reaction tank to the methane fermentation tank or the upstream side thereof.

[3] In [1], the ANAMMOX reaction tank is a batch type reaction tank in which digestive juice is supplied in a batch manner, and after the return step, the reaction tank is exposed to air in the ANAMMOX reaction tank. A wastewater treatment method having an ANAMMOX process, which comprises a step of returning nitrite nitrogen-containing water to the methane fermenter or the upstream side thereof and introducing a digestive solution from the methane fermentation tank into the ANAMMOX reaction tank. ..

[4] A step of methane fermentation treatment of raw water in a methane fermentation tank, a step of introducing nitrite-type nitrification liquid from the methane fermentation tank into a nitrite-type nitrification tank, and aeration to perform nitrite-type nitrification treatment. In a wastewater treatment method having an ANAMMOX process including a step of introducing a treatment liquid of a nitrate nitrification tank into an ANAMMOX reaction tank to perform the ANAMMOX treatment, the nitrite nitrogen concentration in the ANAMMOX reaction tank or its index value is a predetermined value. If it becomes higher than, a sedimentation step of stopping the aeration and precipitating the granule or carrier in the nitrite nitrification tank, and then nitrite nitrogen in the ANAMMOX reaction tank with the aeration stopped. A wastewater treatment method comprising an ANAMMOX process, which comprises a return step of returning the contained water to the methane fermenter or the upstream side thereof.

[5] In [4], the ANAMMOX reaction tank is a continuous reaction tank to which digestive juice is continuously supplied, and in the sedimentation step, the outflow of treated water from the ANAMMOX reaction tank is stopped. At the same time, the introduction of the digestive juice into the nitrite-type nitrification tank and the discharge of the treatment liquid from the nitrite-type nitrification tank were stopped, and in the return process, the outflow of the treatment water from the ANAMMOX reaction tank was stopped. The introduction of the digestive juice into the nitrite-type nitrification tank and the discharge of the treatment liquid from the nitrite-type nitrification tank are resumed, and after the return step, the nitrite property of the reaction tank is performed while aeration is performed in the nitrite-type nitrification tank. A wastewater treatment method comprising an ANAMMOX process, which comprises a step of returning nitrogen-containing water to the methane fermenter or the upstream side thereof.

When nitrite nitrogen accumulates in the ANAMMOX reaction vessel, the concentration of nitrite nitrogen, which strongly inhibits ANAMMOX bacteria, can be rapidly reduced, and the ANAMMOX activity can be rapidly restored. In addition, the dependent vegetative bacteria in the methane fermenter consume the BOD of the raw material to denitrify the nitrite nitrogen, so that the nitrite nitrogen becomes nitrogen gas and is removed from the liquid. Not discharged to the outside.

It is a block diagram explaining the wastewater treatment method which has the ANAMMOX process which concerns on embodiment. It is a block diagram explaining the wastewater treatment method which has the ANAMMOX process which concerns on embodiment. It is a block diagram explaining the wastewater treatment method which has the ANAMMOX process which concerns on embodiment. It is a block diagram explaining the wastewater treatment method which has the ANAMMOX process which concerns on embodiment. It is a block diagram explaining the wastewater treatment method which has the ANAMMOX process which concerns on embodiment.

In the present invention, in the treatment method by the two-tank type ANAMMOX process (methane fermentation tank → nitrite type nitrification tank → ANAMMOX reaction tank) or the one-tank type ANAMMOX process (methane fermentation tank → nitrite type nitrification / ANAMMOX reaction tank), ANAMMOX. When the nitrite nitrogen concentration in the reaction tank and the corresponding index value (nitrogen gas generation amount, etc.) exceed the predetermined value, the nitrite nitrogen-containing water in the ANAMMOX reaction tank or the nitrite-type nitrification / ANAMMOX reaction tank. Is returned to the methane fermenter or the upstream side thereof, and the water to be treated is introduced into the ANAMMOX reaction tank.

At that time, the aeration of the nitrite-type nitrification tank or the nitrite-type nitrification / ANAMMOX reaction tank is stopped to reduce the concentration of nitrite nitrogen.

As a result, when nitrite nitrogen accumulates in the ANAMMOX reaction vessel, the concentration of nitrite nitrogen, which strongly inhibits ANAMMOX bacteria, can be rapidly reduced, and the ANAMMOX activity can be rapidly restored. In addition, the dependent vegetative bacteria in the methane fermenter consume the BOD of the raw material to denitrify the nitrite nitrogen, so that the nitrite nitrogen becomes nitrogen gas and is removed from the liquid. Not discharged to the outside.

In one example of the present invention, it is determined that nitrite nitrogen has accumulated when the nitrite nitrogen concentration exceeds a predetermined value of 20 mg-N / L or more. This predetermined value is 20 mg-N / L or more, particularly 20 to 400 mg-N / L, preferably 50 to 200 mg-N / L, and more preferably 100 to 150 mg-N / L. Good.

In one aspect of the present invention, a bypass line for liquid circulation is provided in the ANAMMOX tank and the methane fermentation tank for returning the nitrite nitrogen-containing water. This line is not used during normal operation. When a high concentration of nitrite nitrogen accumulates in the ANAMMOX tank, aeration is stopped and granules or carriers to which ANAMMOX bacteria and ammonia-oxidizing bacteria are attached are precipitated. After that, the water to be treated in the ANAMMOX process (dehydrated filtrate in the embodiment described later) is passed through the tank to bring the nitrite concentration to about 0 to 100 mg-N / L, preferably about 20 to 50 mg-N / L. Dilute to the specified value (however, the value is lower than the predetermined value). At this time, the amount of water flow is set to LV that does not exceed the sedimentation rate of the granule or the carrier in order to avoid the outflow of the ANAMMOX granule or the carrier. Alternatively, the granule or carrier is separated using a separation means such as a screen.

Water containing nitrite nitrogen is returned to the methane fermentation tank as diluted water to be introduced into the anaerobic digestion process by a circulation line or directly. This water contains nitrite nitrogen, but when it is added to the anaerobic digestion process, heterotrophic denitrification occurs using organic matter derived from the raw material as an electron donor, and nitrite nitrogen is reduced to nitrogen gas. , Removed from the liquid.

Hereinafter, embodiments of the wastewater treatment method of the present invention will be described in detail with reference to the drawings.

1 and 2 are block diagrams showing an embodiment of a processing method by a one-tank type ANAMMOX process, FIG. 1 shows a continuous process, and FIG. 2 shows a batch process.

In both FIGS. 1 and 2, the raw water (BOD and nitrogen-containing wastewater, raw materials and diluted water in the case of organic waste) is first introduced into the anaerobic methane fermentation tank 1 and methane fermentation under anaerobic conditions. It is processed. As the treatment tank of the anaerobic methane fermentation tank 1, any type can be adopted as long as it can perform anaerobic methane fermentation. For example, a floating type (suspension type) anaerobic treatment tank, a fixed bed type anaerobic treatment tank, an upward flow type sludge blanket type anaerobic treatment tank, etc. can be used, and acid fermentation and methane fermentation can be performed in one tank. It may be a one-tank type in which these are carried out, or a two-tank type in which these are carried out in separate tanks.

In the anaerobic methane fermentation tank 1, the BOD component in the raw water is anaerobic methane fermentation treatment to remove about 80 to 90% of the BOD component, and biogas containing methane gas and carbon dioxide gas is generated. The biogas generated in the anaerobic methane fermentation tank 1 is recovered by a recovery system (not shown). The treated water from the methane fermentation tank 1 is dehydrated by the dehydrator 2 and separated into dehydrated sludge (or concentrated liquid) and liquid (filtrate). As the dehydrator 2, a centrifugal dehydrator, a screw press dehydrator, or the like can be used.

The dehydrated filtrate of the anaerobic digestive juice generally has an ammoniacal nitrogen concentration of 500 to 7,000 mg / L, a pH of 7.7 to 9.2, and an IC of 1,000 to 3,000 mg / L.

This dehydrated filtrate is sent to the ANAMMOX reaction tank 3 and denitrified by the ANAMMOX process. The ANAMMOX reaction tank 3 is filled with a granule or a carrier to which ANAMMOX bacteria and ammonia-oxidizing bacteria are attached. Further, the reaction vessel 3 is provided with an aeration device 3a for oxidizing a part of ammoniacal nitrogen to nitrite nitrogen.

[In the case of one-tank type ANAMMOX process (continuous type) (Fig. 1)]
FIG. 1A shows a one-tank continuous ANAMMOX process under normal conditions. The raw water is continuously supplied to the methane fermentation tank 1, the treated water in the methane fermentation tank is continuously supplied to the dehydrator 2, the dehydration filtrate is continuously supplied to the reaction tank 3, and the treated water is continuously treated water. It is taken out from the take-out pipe (treated water discharge line) 4.

When the concentration of nitrite nitrogen in the reaction tank 3 exceeds a predetermined value, the discharge of treated water from the reaction tank 3 (water flow through the pipe 4) is stopped as shown in FIG. 1 (b), and the water flow to the reaction tank 3 is stopped. The supply of the dehydrated filtrate is stopped, the aeration by the aeration device 3a is stopped, and the granule or the carrier to which the ANAMMOX bacteria and the ammonia-oxidizing bacteria are attached is precipitated. Although not shown, a dehydration filtrate storage tank is usually provided in front of the reaction tank, and the dehydration filtrate that is not supplied to the reaction tank can be stored in the sedimentation step.

Then, as shown in FIG. 1 (c), the supply of the dehydrated filtrate of the reaction tank is restarted, and the return of the nitrite nitrogen-containing water in the reaction tank 3 to the methane fermentation tank 1 is started by the circulation line 5. At this time, the supply of raw water to the methane fermentation tank 1 continues. As a result, the production of nitrite nitrogen in the reaction vessel 3 is stopped. Further, when the produced nitrite nitrogen is returned to the methane fermentation tank 1 in the reaction tank 3, it is denitrified by the denitrifying bacteria and discharged as nitrogen gas. As a result, the nitrite nitrogen in the system gradually decreases. However, since raw water is continuously supplied, ammoniacal nitrogen derived from raw water is gradually accumulated in the system.

The step of FIG. 1 (c) is continued until the nitrite nitrogen concentration in the reaction vessel 3 becomes a specified value (100 mg-N / L in this example) or less. This specified value is selected from the range of 0 to 100 mg-N / L, preferably 20 to 50 mg-N / L (however, a value lower than a predetermined value). The same applies to the following other embodiments.

In the settling process and the return process, the discharge of treated water from the reaction tank is stopped, but since the supply of raw water to the methane fermentation tank continues, the amount of water in the system increases over time, but this increased. Minutes can be temporarily stored in the dehydration filtrate storage tank. However, if the capacity of the dehydration filtrate storage tank is small or the amount of raw water supplied is large, it is necessary to limit or stop the amount of raw water supplied.

When the concentration of nitrite nitrogen in the reaction tank 3 becomes equal to or lower than the specified value, aeration is restarted in a state where the return from the reaction tank 3 to the methane fermentation tank 1 is continued as shown in FIG. 1 (d). As a result, the ammoniacal nitrogen is gradually oxidized to nitrite nitrogen, the ANAMMOX reaction starts to proceed from the ammoniacal nitrogen and the nitrite nitrogen, and the ammoniacal nitrogen concentration in the system gradually decreases.

When the ammoniacal nitrogen concentration drops below a predetermined value, the water flow in the circulation line 5 is stopped, the water flow in the treated water discharge line (pipe 4) is restarted, and the normal operation shown in FIG. 1 (a) is restarted. To do.

[In the case of one-tank type ANAMMOX process (batch type) (Fig. 2)]
FIGS. 2 (a) to 2 (c) show a one-tank type batch type ANAMMOX process under a normal state.

The treatment liquid subjected to the methane fermentation treatment in the methane fermentation tank 1 is dehydrated in a batch type by the dehydrator 2, and the dehydrated filtrate is introduced into the reaction tank 3 in a batch type (transfer step of FIG. 2A). ). After the transfer is completed, aeration is performed in the reaction vessel 3 as shown in FIG. 2 (b), and the ANAMMOX reaction proceeds. After the nitrogen concentration drops below a predetermined value, the treated water is taken out as shown in FIG. 2 (c). After that, the process returns to the transfer step of (a), and each step of (a) → (b) → (c) is repeated.

When the concentration of nitrite nitrogen in the reaction vessel 3 exceeds a predetermined value in the step of FIG. 2 (b) of one cycle of batch operation, aeration is stopped as shown in FIG. 2 (d), and ANAMMOX bacteria and ammonia are used. Precipitate granules or carriers to which oxidizing bacteria are attached. Next, as shown in FIG. 2 (e), water flow through the circulation line 5 (return of nitrite nitrogen-containing water in the reaction tank 3 to the methane fermentation tank 1) is started, and the dehydrator 2 is started from the methane fermentation tank 1. The filtrate is sent to the reaction vessel 3 via the above. The supply of raw water to the methane fermenter 1 will continue.

As a result, the production of nitrite nitrogen in the reaction vessel 3 is stopped. Further, the nitrite nitrogen generated in the reaction tank 3 is returned to the methane fermentation tank 1, denitrified, and discharged as nitrogen gas. Therefore, the concentration of nitrite nitrogen in the system gradually decreases. However, the ammoniacal nitrogen derived from the raw material gradually accumulates in the system.

In the step of FIG. 2 (e), the nitrite nitrogen concentration in the reaction vessel 3 is equal to or less than the specified value (100 mg-N / L or less in this example), preferably 20 to 50 mg-N / L (however, a predetermined value). Continue until lower value).

When the concentration of nitrite nitrogen in the reaction tank 3 becomes less than the specified value, the return from the reaction tank 3 to the methane fermentation tank 1 is stopped, and the return from the methane fermentation tank 1 to the reaction tank 3 via the dehydrator 2 is stopped. The introduction of the filtrate from the above is stopped, and the aeration of the reaction vessel 3 is restarted as shown in FIG. 2 (b). As a result, nitrite nitrogen is gradually generated from the ammoniacal nitrogen in the reaction vessel 3, the ANAMMOX reaction starts to proceed from the ammoniacal nitrogen and the nitrite nitrogen, and the ammoniacal nitrogen concentration gradually decreases.

When the ammoniacal nitrogen concentration in the reaction vessel 3 drops to a predetermined value or less, it is determined that the treatment is completed, and the process proceeds to the treated water extraction step (FIG. 2C). After that, the normal process of FIG. 2A → (b) → (c) is repeated.

[In the case of a two-tank type ANAMMOX process (continuous type) (Fig. 3)]
FIG. 3A shows a two-tank continuous ANAMMOX process under normal conditions. In this process, the reaction water (digestion liquid) from the methane fermentation tank 1 is dehydrated by the dehydrator 2, the filtrate is continuously introduced into the nitrite nitrification tank 7, aerated by the aeration device 7a, and nitrite nitrification. Is done. In order to perform stable nitrite-type nitrification, it is preferable to adjust the amount of aeration by the aeration tank 7a so that the DO concentration in the nitrite-type nitrification tank 7 is 0.5 to 4 mg / L.

The nitrifying solution from the nitrite-type nitrification tank 7 is continuously introduced into the reaction tank 3 and denitrified by the action of ANAMMOX bacteria that perform a denitrification reaction using ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. It is nitrified. In order to reduce residual nitrogen by efficiently reacting ammoniacal nitrogen and nitrite nitrogen in the denitrification treatment with this ANAMMOX bacterium, the nitrifying solution from the nitrite type nitrification tank 7 is composed of ammoniacal nitrogen: nitrite. Nitrite nitrogen = 1: 1.32 to 1.4 mol ratio nitrification solution is preferable.

The treated water from the reaction tank 3 is taken out through the pipe 4.

In the process of FIG. 3 (a), when the concentration of nitrite nitrogen in the reaction vessel 3 exceeds a predetermined value, the discharge of treated water from the reaction vessel 3 is stopped and nitrite is stopped as shown in FIG. 3 (b). The supply of the dehydrated filtrate to the nitrification tank is stopped, the discharge of the nitrification liquid from the nitrite nitrification tank is stopped, the aeration of the nitrite nitrification tank 7 is stopped, and the adherent carrier of ammonia-oxidizing bacteria is precipitated. Then, as shown in FIG. 3 (c), the introduction of the dehydration filtrate into the nitrite-type nitrification tank 7 and the introduction of ammonia and nitrite nitrogen-containing water from the nitrite-type nitrification tank 7 into the reaction tank 3 were resumed. , The water flow of the circulation line 5 from the reaction tank 3 to the methane fermentation tank 1 is started. At this time, the supply of raw water to the methane fermentation tank 1 continues.

As a result, the production of nitrite nitrogen in the nitrite-type nitrification tank 7 is stopped, and the nitrite nitrogen produced in the nitrite-type nitrification tank 7 passes through the reaction tank 3 and the circulation line 5 to the methane fermentation tank. It is returned to 1 and denitrified and discharged as nitrogen gas. As a result, the concentration of nitrite nitrogen in the system gradually decreases. However, ammoniacal nitrogen derived from raw water is accumulated in the system. The step of FIG. 3 (c) is continued until the nitrite nitrogen becomes a specified value or less (for example, 100 mg-N / L or less), preferably 20 to 50 mg-N / L (however, a value lower than a predetermined value). ..

When the nitrite nitrogen concentration in the reaction tank 3 becomes less than the specified value, as shown in FIG. 3D, the nitrite type nitrification tank 7 is continuously returned from the reaction tank 3 to the methane fermentation tank 1. Resume aeration. As a result, the nitrite nitrogen concentration in the reaction vessel 3 gradually increases, the ANAMMOX reaction begins to proceed, and the ammoniacal nitrogen concentration gradually decreases.

When the ammoniacal nitrogen concentration drops below a predetermined value, the water flow through the circulation line 5 is stopped, the treated water is restarted from the pipe 4, and the normal operation shown in FIG. 3A is restarted.

[Another aspect]
In the above description, the water circulated from the reaction tank 3 by the circulation line 5 is directly supplied to the methane fermentation tank 1, but at least a part of it is anaerobic digested as shown in FIG. 4, for example. It may be supplied to the diluted water line of the raw material waste. In this case, the supply of diluted water is stopped when the circulation operation is started. In any case, heterotrophic denitrification occurs using the organic matter as the raw material as an electron donor, and nitrite nitrogen is removed. Although FIG. 4 shows a one-tank type, it may be a two-tank type.

In the above description, when the nitrite nitrogen concentration in the reaction tank 3 exceeds a predetermined value, the nitrite nitrogen-containing water is returned from the reaction tank 3, but the treated water line (pipe 4) The nitrite nitrogen-containing water may be returned from. Further, as shown in FIG. 5, when the treated water tank 9 that receives the treated water from the reaction tank 3 is installed, the nitrite nitrogen-containing water in the reaction tank 3 is returned via the treated water tank 9. It may be. FIG. 5 shows a one-tank type, but the same applies to a two-tank type.

[Experimental Example 1]
Using an SBR reaction tank having a tank volume of 4 L, 1.0 L (SV25%) of the enrichment-cultured one-tank type ANAMMOX granule was charged, and the one-tank type ANAMMOX apparatus was started up.

As the raw water, synthetic wastewater having a BOD concentration of 360 mg / L and an ammoniacal nitrogen concentration of 2,000 mg / L prepared by using sodium acetate as a BOD component and ammonium sulfate as an ammoniacal nitrogen component was used.

The water temperature in the tank was set to 32 ° C., and the pH was adjusted to 7.7 using a pH adjuster (sodium carbonate aqueous solution, 80 g / L).

The operation of the SBR reaction tank was such that the amount of exchanged water per batch was 0.8 L, the inflow step was 10 min, the aeration step was 6 hours, the settling step was 3 min, and the discharge step was 10 min. The aeration in the tank was carried out in the range of 0 to 2.0 L / min, and the DO was controlled using a mass flow controller so as to be 0.5 mg / L.

When the operation was performed under these conditions, ammonia nitrogen 1 to 3 mg / L, nitrite nitrogen 4 to 12 mg / L, and nitrate nitrogen 180 to 210 mg / L were removed, and the nitrogen load was 1.5 kg-N / m ^3. / D, nitrogen removal rate was 1.3 kg-N / m ³ / d. From here, the aeration amount was fixed at 4 L / min for only one batch, and the operation was performed to accumulate nitrite nitrogen in the tank. As a result, 360 mg / L of nitrite nitrogen was accumulated in the tank. Here, the operation of the apparatus was temporarily stopped, and after the granule was completely settled, raw water was sent to bring the nitrite nitrogen concentration in the tank to 90 mg / L. After that, as a result of restarting the operation of the device, ^{it was confirmed that the nitrogen load was 1.5 kg-N / m 3} / d and the nitrogen removal rate was 1.3 kg-N / m ³ / d, and the activity recovered quickly. Was done.

[Experimental Example 2]
The removal of nitrite nitrogen in the methane fermentation tank was confirmed by a batch test in which raw water containing methane fermentation sludge and nitrite nitrogen was mixed.

350 mL (TS43,000 mg / L) of methane fermentation sludge and 50 mL of 0.3M phosphate buffer (pH 7.5) are mixed in a vial and stirred with a stirrer installed in an incubator at 35 ° C. to generate methane gas. Was measured.

After confirming that gas generation due to substrate carry-in from sludge was eliminated, 50 mL of a mixture of sodium acetate and nitrite nitrogen was added (final concentration CODcr 3,000 mg / L, nitrite nitrogen concentration 150 mg / L) ( System 1). Similarly, a system containing only acetic acid containing no nitrite nitrogen was prepared as a blank (system 2), and the amount of methane gas generated was compared.

In system 1, after the reaction for 5 days, the concentration of nitrite nitrogen in the tank was measured and found to be 1 mg / L or less, and substantially all of the nitrite nitrogen was removed. Since the amount of methane gas generated was 340 mL in system 1 and 330 mL in system 2, no inhibition of methane-producing bacteria by nitrite nitrogen was confirmed.

[Experimental Example 3]
In the same procedure as in Experimental Example 1, a one-tank type ANAMMOX device was started up, and nitrite nitrogen was accumulated in the tank. When 320 mg / L of nitrite was accumulated in the tank and the nitrite concentration in the tank was not diluted and returned to the original operating conditions, the treated water was sub-treated due to the inhibition of ANAMMOX bacteria by nitrite. Since the nitrate nitrogen concentration increased with each batch and the nitrite concentration in the tank reached 1,300 mg / L, it was confirmed that the ANAMMOX activity did not recover.

1 Methane fermenter 2 Dehydrator 3 ANAMMOX reaction tank 3a Aeration device 5 Circulation line 7 Nitrite nitrification tank 7a Aeration device

Claims (5)

A step of methane fermentation treatment of raw water in a methane fermentation tank and a nitrite-type nitrification treatment and an ANAMMOX treatment by introducing the digested liquid from the methane fermentation tank into an ANAMMOX reaction tank and aerating the raw water in the reaction tank. In a wastewater treatment method having an ANAMMOX process with steps to be performed
When the nitrite nitrogen concentration in the ANAMMOX reaction vessel or its index value becomes higher than the predetermined value,
A sedimentation step of stopping the aeration and sedimenting the granule or carrier in the ANAMMOX reaction vessel.
Next, a wastewater treatment method having an ANAMMOX process, which comprises a return step of returning the nitrite nitrogen-containing water of the ANAMMOX reaction tank to the methane fermentation tank or the upstream side thereof with the aeration stopped. In claim 1, the ANAMMOX reaction tank is a continuous reaction tank to which digestive juice is continuously supplied.
In the sedimentation step, the outflow of the treated water from the ANAMMOX reaction tank is stopped, and the supply of the digestive juice to the ANAMMOX reaction tank is stopped.
In the return process, the supply of digestive juice was restarted while the outflow of treated water was stopped.
Wastewater treatment having an ANAMMOX process, which comprises returning the nitrite nitrogen-containing water in the reaction tank to the methane fermentation tank or the upstream side thereof while aerating in the ANAMMOX reaction tank after the return step. Method. In claim 1, the ANAMMOX reaction tank is a batch type reaction tank in which digestive juice is supplied in a batch manner.
After the return step, while aerating in the ANAMMOX reaction tank, the nitrite nitrogen-containing water in the reaction tank is returned to the methane fermentation tank or the upstream side thereof, and the digested liquid from the methane fermentation tank is returned to the ANAMMOX. A wastewater treatment method comprising an ANAMMOX process, which comprises performing a step of introducing into a reaction vessel. A step of methane fermentation treatment of raw water in a methane fermentation tank, a step of introducing nitrite-type nitrification liquid from the methane fermentation tank into a nitrite-type nitrification tank, and performing nitrite-type nitrification treatment by aeration, and nitrite-type nitrification In a wastewater treatment method having an ANAMMOX process, which comprises a step of introducing the treatment liquid in the tank into an ANAMMOX reaction tank and performing the ANAMMOX treatment.
When the nitrite nitrogen concentration in the ANAMMOX reaction vessel or its index value becomes higher than the predetermined value,
A sedimentation step of stopping the aeration and precipitating the granule or carrier in the nitrite nitrification tank.
Next, a wastewater treatment method having an ANAMMOX process, which comprises a return step of returning the nitrite nitrogen-containing water of the ANAMMOX reaction tank to the methane fermentation tank or the upstream side thereof with the aeration stopped. In claim 4, the ANAMMOX reaction vessel is a continuous reaction vessel to which digestive juice is continuously supplied.
In the sedimentation step, the outflow of the treated water from the ANAMMOX reaction tank is stopped, the introduction of the digestive liquid into the nitrite-type nitrification tank and the discharge of the treatment liquid from the nitrite-type nitrification tank are stopped.
In the return process, the introduction of the digestive juice into the nitrite-type nitrification tank and the discharge of the treatment liquid from the nitrite-type nitrification tank were resumed while the outflow of the treated water from the ANAMMOX reaction tank was stopped.
The ANAMMOX process comprises a step of returning the nitrite nitrogen-containing water of the reaction tank to the methane fermentation tank or the upstream side thereof while aerating the nitrite type nitrification tank after the return step. Wastewater treatment method.

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