JP6919413B2 - Ammonia nitrogen-containing wastewater denitrification treatment method and denitrification treatment equipment - Google Patents

Description

The present invention is a batch (SBR) one-tank ANAMMOX process for ammonia nitrogen-containing wastewater, especially high pH or high inorganic carbon dioxide concentration wastewater containing ammoniacal nitrogen, such as dehydrated filtrates of methane fermentation digestive juices and chemical plants. The present invention relates to a denitrification treatment method and a denitrification treatment apparatus for ammoniacal nitrogen-containing wastewater, which reduces the amount of a pH adjuster used when treating wastewater and the like.
Here, the one-tank type ANAMMOX process is a wastewater treatment process in which ammonia nitrogen is nitrited by a mixed sludge of ammonia-oxidizing bacteria and ANAMMOX bacteria and denitrification by the ANAMMOX reaction is performed in the same tank to remove nitrogen. Point to.

As a denitrification process for ammoniacal nitrogen-containing wastewater, ammonia nitrogen and nitrite are used by using ANAMMOX bacteria, which are independent nutrient microorganisms that use ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor. The ANAMMOX process, which reacts with nitrogen to denitrify, is known.

Conventionally, the wastewater treatment process using the ANAMMOX reaction has been carried out in a two-tank type in which a nitrite type nitrification tank and an ANAMMOX denitrification tank are provided and the treatment is performed in the order of nitriteization → ANAMMOX reaction, but in recent years, ammonia oxidation has been carried out. A one-tank type ANAMMOX process has been developed in which nitrite formation and ANAMMOX reaction are carried out in one tank using sludge in which bacteria and ANAMMOX bacteria coexist (Patent Document 1).

The one-tank type ANAMMOX process can be processed in both batch type (SBR) (Patent Document 2) and continuous type (Patent Document 3) reaction tanks, but a solid-liquid separation device is not required and the device structure is simple. The SBR type reaction tank is often used.

The SBR type reaction tank is a reaction tank that operates as follows.
1. 1. Raw water is put into the reaction tank.
2. By aerating the inside of the reaction vessel, the one-tank type ANAMMOX reaction is allowed to proceed, and ammoniacal nitrogen is converted into nitrogen gas and removed from the water.
3. 3. Stop aeration and let stand to settle sludge containing ammonia-oxidizing bacteria and ANAMMOX bacteria.
4. Discharge the supernatant water as treated water.
5. The new raw water is put into the reaction tank again, and operations 2 to 4 are repeated.

It is known that the activity of ANAMMOX bacteria decreases in a high pH region exceeding pH 8.3 as compared with the activity in the case of pH 6.7 to 8.3 (Non-Patent Document 1). It is necessary to adjust the pH of ANAMMOX bacteria to, for example, about 7 to 8 so as not to reduce the activity of the ANAMMOX bacteria.
However, when the pH of the raw water is high, the pH of the liquid in the tank rises when the raw water is charged into the reaction tank.

Therefore, in Patent Document 2, in the SBR type reaction vessel shown in FIG. 3, the pH is adjusted by adding an acid to the raw water according to the following procedure.
(1) Raw water is introduced into the reaction tank 1 from the raw water introduction path L1 by the pump P1.
(2) Air is introduced into the reaction vessel 1 from the air introduction path L4 as an oxygen-containing gas to simultaneously proceed with nitrite formation and the ANAMMOX reaction.
(3) At this time, the pump P2 is controlled so that the pH of the reaction solution becomes 7 to 8 according to the pH of the pH measuring device, and sodium carbonate is injected as a pH adjuster from the drug introduction path L2.
(4) After the reaction is completed, the aeration is stopped and the mixture is allowed to stand to precipitate sludge containing ammonia-oxidizing bacteria and ANAMMOX bacteria.
(5) The supernatant water is discharged as treated water from the treated water outlet path 3 by the pump P3.
(6) New raw water is put into the reaction tank 1 again, and the above steps (2) to (5) are repeated.
In FIG. 3, 3 is a reaction solution 3 in which biological sludge 2 containing ANAMMOX bacteria and ammonia-oxidizing bacteria is dispersed, 4 is an air diffuser, 5 is a take-out unit, and 6 is a control device. The dissolved oxygen concentration in the reaction vessel 1 is measured by the dissolved oxygen concentration measuring device DO, and the measured value of the dissolved oxygen concentration measuring device DO and the measured value of the pH measuring device pH are input to the control device 6.

Special Table 2001-506535 Gazette Japanese Patent No. 5347221 Japanese Unexamined Patent Publication No. 2010-22193

Wastewater Engineering 5th Edition

When the pH is adjusted by adding a pH adjuster (for example, sodium carbonate) as in Patent Document 2 in order to prevent the pH of the liquid in the tank from rising due to raw water, it is necessary to add a pH adjuster and the ANAMMOX reaction. Inorganic carbon (IC) required _{for the vitrification reaction volatilizes as CO 2} gas at the dissociation equilibrium, and the amount of IC added to the ANAMMOX reaction tank increases to compensate for this.
Further, even if the pH of the raw water is 8.3 or less, the pH of the raw water containing a high concentration of inorganic carbon (IC) may increase due to carbonic acid stripping due to aeration. Face to face.

When the pH of the raw water is high or when the raw water contains a large amount of IC, the pH of the solution in the reaction vessel may rise, but simply adding a pH adjuster to adjust the pH is not possible. Not desirable.

In the present invention, when treating high pH or high IC concentration ammonia nitrogen-containing wastewater by the SBR type one-tank type ANAMMOX process, the pH of the reaction tank rises at the time of introduction of raw water, and the activity of ANAMMOX bacteria decreases. An object of the present invention is to provide a technique for preventing a decrease in the nitrogen removal rate without using a pH adjuster or after reducing the amount of the pH adjuster used.

As a result of repeated studies to solve the above problems, the present inventors conducted aeration at the time of introducing raw water into the ANAMMOX reaction tank to promote nitrite formation and ANAMMOX reaction even at the time of introducing raw water to produce ammoniacal nitrogen. It has been found that the pH increase due to the inflow of high-pH raw water can be suppressed by removing the pH and lowering the pH by removing the ammoniacal nitrogen.
That is, the gist of the present invention is as follows.

[1] A method of denitrifying in a batch manner using a reaction tank containing a mixed sludge of ammonia-oxidizing bacteria and ANAMMOX bacteria using ammonia nitrogen-containing wastewater as raw water, in the step of introducing raw water into the reaction tank. A method for denitrifying ammonia-based nitrogen-containing wastewater, which comprises performing an aeration step at the same time.

[2] In [1], the ratio of the time of the raw water introduction process (hereinafter referred to as "raw water introduction time") to the time of the aeration process (hereinafter referred to as "aeration time") (percentage of raw water introduction time / aeration time). ) Is 40 to 100%, which is a method for denitrifying ammonia nitrogen-containing wastewater.

[3] In [1], the pH in the reaction vessel is measured, and when the pH measurement value exceeds 8.3, the introduction of the raw water is stopped, and the wastewater containing ammoniacal nitrogen is removed. Nitrogen treatment method.

[4] The method for denitrifying ammonia-based nitrogen-containing wastewater according to any one of [1] to [3], wherein the pH of the raw water exceeds 8.3 and is 10 or less.

[5] The method for denitrifying ammonia-based nitrogen-containing wastewater according to any one of [1] to [4], wherein the raw water has an inorganic carbonic acid concentration of 150 to 3,000 mg / L.

[6] The method for denitrifying ammonia nitrogen-containing wastewater according to any one of [1] to [5], wherein the raw water is a dehydrated filtrate of an anaerobic digestive juice.

[7] A denitrification treatment device for performing the denitrification treatment method for ammoniacal nitrogen-containing wastewater according to [1], [2], [5] or [6], which comprises ammonia-oxidizing bacteria and ANAMMOX bacteria. A reaction tank containing mixed sludge, a raw water introduction means for introducing ammonia nitrogen-containing wastewater into the reaction tank as raw water, a treated water discharge means for discharging denitrifying treated water from the reaction tank, and a inside of the reaction tank. It is a batch type one-tank type ANAMMOX reactor having an aeration means for aeration of the reaction solution, an operation of the raw water introduction means, and a control means for controlling the operation of the raw water introduction means, and the control means is the raw water introduction. A denitrification treatment device for ammoniacal nitrogen-containing wastewater, which is a means for controlling aeration in the reaction vessel by the aeration means when the raw water is introduced by the means.

[8] A denitrification treatment apparatus for performing the denitrification treatment method for ammonia-containing nitrogen-containing wastewater according to [3] or [4], and a reaction tank containing a mixed sludge of ammonia-oxidizing bacteria and ANAMMOX bacteria. , A raw water introduction means for introducing ammonia nitrogen-containing wastewater into the reaction tank as raw water, a treated water discharge means for discharging denitrifying treated water from the reaction tank, and an aeration means for aerating the reaction liquid in the reaction tank. A batch-type one-tank type ANMOMOX reactor having a pH measuring means for measuring the pH of the liquid in the reaction vessel, an operation of the raw water introduction means, and a control means for controlling the operation of the aeration means. The control means controls the aeration of the inside of the reaction vessel by the aeration means when the raw water is introduced by the raw water introduction means, and when the measured value of the pH measuring means exceeds 8.3, the control means is by the raw water introduction means. A denitrification treatment device for ammoniacal nitrogen-containing wastewater, which is characterized by controlling the introduction of raw water.

According to the present invention, when treating effluent containing ammoniacal nitrogen with high pH or high IC concentration by the SBR type one-tank type ANAMMOX process, a pH adjuster is not used or the amount used is reduced. The pH of the solution in the reaction vessel at the time of introduction of raw water can be maintained within a range in which the activity of the ANAMMOX reaction does not decrease, and the denitrification treatment by the ANAMMOX reaction can be performed stably and efficiently.

It is a system diagram of the SBR type one-tank type ANAMMOX reaction tank which explains an example of the raw water introduction and aeration control method by this invention. It is a system diagram of the SBR type one-tank type ANAMMOX reaction tank which explains another example of the raw water introduction and aeration control method by this invention. It is a system diagram which shows the general SBR type one-tank type ANAMMOX reaction tank.

Embodiments of the present invention will be described in detail below.

In the present invention, aeration is performed in parallel when introducing raw water into the SBR type one-tank type ANAMMOX reaction tank, and when introducing raw water into the reaction tank, nitrification of ammoniacal nitrogen and ANAMMOX of nitrite nitrogen and ammoniacal nitrogen are performed. Proceed with denitrification by reaction.

The mechanism of action of the present invention for aeration when introducing raw water into the reaction vessel is as follows.
The reaction formulas of the nitrite formation of ammoniacal nitrogen and the ANAMMOX reaction are as shown in the following formulas 1 and 2. The one-tank type ANAMMOX reaction that summarizes the formulas 1 and 2 is as shown in the following formula 3, and in the one-tank type ANAMMOX reaction, the pH decreases as the ammoniacal nitrogen is removed. According to the present invention, aeration is started at the same time as the introduction of the raw water is started, and the raw water is introduced slowly (at a low flow rate over time), so that the pH increase due to the introduction of the raw water is offset by the pH decrease due to the removal of ammoniacal nitrogen. As a result, it is possible to maintain the pH of the liquid in the tank in the pH range (pH 6.7 to 8.3) that does not inhibit the ANAMMOX bacteria.
<Nitriteization of ammoniacal nitrogen>
1.0NH ₄ ⁺ + _{1.5O 2} → 1.0NO ₂ + H ₂ O + ^{2.0H +} Equation 1
<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 ^- Equation 2
<Denitrification reaction by one-tank type ANAMMOX reaction>
1.0NH ₄ ⁺ + 0.65O ₂ →
^{_{0.44N 2 + 0.11NO 3 - + 1.14H}} + + 1.43H 2 O Formula 3

Conventionally, in the SBR type one-tank type ANAMMOX process, raw water is not introduced into the reaction tank at a low flow rate over a long period of time while aerating the reaction tank. That is, after the reaction is completed, the aeration is stopped and allowed to stand, the sludge is settled, and the supernatant water is discharged as treated water. When the water level inside reaches a predetermined position, the introduction of raw water is usually stopped, and then aeration is started to carry out the reaction. In this way, conventionally, introducing raw water in a short time while aeration is stopped is intended to maintain a high reaction rate of ammonia-oxidizing bacteria and ANAMMOX bacteria by maintaining a high concentration of ammoniacal nitrogen in the reaction vessel. This is because it is common, and in the conventional SBR type one-tank type ANAMMOX process, there was no idea that aeration was performed in parallel with the introduction of raw water.

The present invention is suitably applied to the case where the wastewater containing ammoniacal nitrogen having a high pH or a high IC concentration, which tends to cause the pH of the liquid in the tank to rise due to the introduction of the raw water, is treated as the raw water by the SBR type one-tank type ANAMMOX process. NS.

In the present invention, the ammoniacal nitrogen-containing wastewater to be treated may be a liquid containing ammoniacal nitrogen or organic nitrogen that can be denitrified by contacting with sludge containing ammonia-oxidizing bacteria and ANAMMOX bacteria. A high effect can be obtained in wastewater containing a high concentration of ammoniacal nitrogen and exceeding pH 8.3 or wastewater having a high IC concentration.

The pH of the ammoniacal nitrogen-containing wastewater to be treated in the present invention is preferably more than 8.3 and 10 or less. In many cases, stable treatment is possible without applying the present invention if the raw water has a pH of 8.3 or less, and if the raw water has a high pH exceeding 10 pH, the pH is sufficient even if the present invention is applied. It may not be possible to obtain the lowering effect. For the same reason, the IC concentration of the ammoniacal nitrogen-containing wastewater targeted in the present invention is preferably 150 to 3,000 mg / L.
Further, the ammoniacal nitrogen concentration of the ammoniacal nitrogen-containing wastewater to be treated in the present invention is preferably 200 to 7000 mg / L.
Specific examples of such wastewater include dehydrated filtrates of anaerobic digestive juice (methane fermentation digestive liquid), wastewater from various chemical factories, and the like. The water quality of the dehydrated filtrate of the anaerobic digestive juice is usually 500 to 7,000 mg / L for ammonia nitrogen, 7.7 to 9.2 for pH, and 1,000 to 3,000 mg / L for IC concentration. ..

The ammonia-oxidizing bacteria used for nitrite formation of ammoniacal nitrogen in the present invention are bacteria conventionally used for nitrite formation of ammoniacal nitrogen, and nitrite by oxidizing ammoniacal nitrogen under aerobic conditions. It is a bacterium that converts to sex nitrogen. Such nitrite bacteria can be generated by maintaining the liquid to be treated containing ammoniacal nitrogen under aerobic conditions, but the sludge collected from the nitrite step of organic wastewater treatment can be used as it is or as it is. It can be used by adhering to a biological reaction member.

The ANAMMOX bacterium used for denitrification in the present invention is a bacterium belonging to Planctomycetes, which is a denitrifying bacterium that reacts ammoniacal nitrogen and nitrite nitrogen in an anaerobic atmosphere and directly converts them into nitrogen gas. Unlike the heterotrophic denitrifying bacterium used for conventional denitrification, such ANAMMOX bacterium is an autotrophic bacterium. Does not require the addition of nutrient sources. Further, since ANAMMOX bacteria react ammonia nitrogen and nitrite nitrogen and directly convert them into nitrogen gas, ammonia nitrogen and nitrite nitrogen can be removed at the same time, and harmful by-products are not produced. Such ANAMMOX bacteria can be generated by anaerobic reaction of a liquid to be treated containing ammoniacal nitrogen and nitrite nitrogen to denitrify, but sludge collected from the denitrification step of the nitrogen-containing liquid. Can be used as it is or attached to a biological reaction member.

The mixed sludge of ammonia-oxidizing bacteria and ANAMMOX bacteria used in the present invention is a mixed sludge containing such ammonia-oxidizing bacteria and ANAMMOX bacteria. These bacteria may be contained in the sludge in a random mixed state in the mixed sludge, but biological sludge configured so that the surface of the ANAMMOX bacteria is covered with ammonia-oxidizing bacteria is preferable, and the biological sludge is particularly carried inside the carrier. Biological sludge formed so that the surface of the ANAMMOX bacterium is covered with the ammonia-oxidizing bacterium is preferable. Such sludge is formed by allowing a carrier to be present in the reaction solution and continuing the treatment. When biological sludge adheres to such a carrier, the surface side becomes aerobic, so that ammonia-oxidizing bacteria predominate, and the inside becomes anaerobic, so that ANAMMOX bacteria predominate, and the biological sludge having the above constitution is likely to be formed. Instead of the carrier, biological sludge formed so that the surface of the ANAMMOX granule obtained by self-granulating the ANAMMOX bacteria is covered with the ammonia-oxidizing bacteria may be used.

As the oxygen-containing gas used for aeration in the present invention, an oxygen-containing gas can be used without limitation. Air is preferable as the oxygen-containing gas, but other gases can also be used.

For example, when the present invention is carried out in the SBR type reaction vessel shown in FIG. 3, the procedure can be as follows.
(1) The introduction of raw water containing ammoniacal nitrogen into the reaction tank 1 is started by the operation of the pump P1, and the aeration device 4 is operated to operate the air introduction path L4 to the reaction tank 1 of air (oxygen-containing gas). By aerating the inside of the tank by starting the introduction of raw water, the introduction of raw water and the denitrification reaction proceed at the same time. The raw water introduction time is preferably 40 to 100% of the aeration time. Alternatively, while measuring the pH in the tank instead of controlling the time, introduce the raw water until the pH reaches 8.3 when the pH in the tank falls below 8.3, and introduce the raw water when the pH exceeds 8.3. It is also possible to repeat the operation of stopping and only aerating, and restarting the introduction of raw water when the pH becomes 8.3 or less due to the aeration of the liquid in the tank.
(2) After the reaction is completed, the aeration is stopped and the mixture is allowed to stand to precipitate sludge containing ammonia-oxidizing bacteria and ANAMMOX bacteria.
(3) The supernatant water is discharged as treated water from the treated water outlet L3 by the pump P3.
(4) Aeration is performed while introducing new raw water into the reaction tank 1 again, and the above steps (1) to (3) are repeated.

The method of introducing raw water and controlling aeration according to the present invention will be described below with reference to FIGS. 1 and 2. In FIGS. 1 and 2, members having the same functions as those in FIG. 3 are designated by the same reference numerals. Further, in FIGS. 1 and 2, the dissolved oxygen concentration measuring device DO and the control device 6 thereof in FIG. 3 are not shown.

FIG. 1 shows an SBR type one-tank type ANAMMOX reaction tank 1 that performs a raw water introduction step and an aeration step by time control, and a pump P1 is operated by a control device 10 to introduce raw water into the reaction tank 1 and blower B. By operating and aerating with air, the raw water introduction process and the aeration process are performed at the same time.

In this method, the ratio (raw water introduction time / aeration time percentage) between the raw water introduction process time (raw water introduction time) and the aeration process time (aeration time) is 40 to 100%, particularly 50 to 100%. It is preferable to control the raw water introduction time and the aeration time. That is, the introduction of raw water and aeration may be started at the same time, and when the water level in the reaction vessel reaches a predetermined position, the introduction of raw water and aeration may be terminated at the same time to end the reaction (raw water introduction time / aeration time ratio). 100%), raw water introduction and aeration were started at the same time, raw water introduction and aeration were performed for a predetermined time, and when the water level in the reaction tank reached a predetermined position, raw water introduction was stopped, and then only aeration was performed. The post-reaction may be terminated.

In this time-controlled method, the introduction of raw water is stopped when the water level in the reaction vessel 1 rises to a predetermined position using a water level sensor, a flow meter, a timer, etc. (not shown), and then further if necessary. After the aeration is continued, the aeration is stopped and the sludge sedimentation step and the treated water discharge step are performed.

In both this control method and the following control methods, in order to achieve a high nitrogen removal rate, it is preferable to secure a sufficient aeration time (reaction time), and the raw water state, reaction tank specifications, and tank liquid. Although it depends on the amount, the aeration time is preferably 2 hours or more, for example, 4 to 16 hours.

In this case, if the pH of the liquid in the tank measured by the pH measuring device pH exceeds the preferable pH range (6.7 to 8.3), the pump P2 is operated to adjust the pH from the drug introduction path L2. An agent (acid or alkali) may be added.

In FIG. 2, the pH of the liquid in the reaction vessel 1 is measured by the pH of the pH measuring device, and the raw water introduction step and the aeration step are controlled based on the pH measurement value. The introduction step and the aeration step are started at the same time, the pH of the liquid in the reaction vessel 1 is measured, and after the pH measurement value becomes 8.3 or less by the introduction and aeration of raw water, the water level provided in the reaction vessel 1 is provided. When the sensor LS detects that the water level has reached a predetermined level, the introduction of raw water is stopped. At that time, by the control device 10 to which the pH measurement value is input, if the pH measurement value exceeds 8.3, the introduction of raw water is temporarily stopped, only aeration is performed, and the pH becomes 8.3 or less due to the aeration. When it becomes, the introduction of raw water is restarted. Intermittent introduction is performed until the specified water level is reached. After that, if necessary, the aeration is further continued, the aeration is stopped, the reaction is terminated, and the sludge precipitation step and the treated water discharge step are performed.

In this way, by performing aeration in parallel with the introduction of raw water into the reaction vessel, it is not necessary to add a chemical for pH adjustment, or the amount of the chemical added is significantly reduced as compared with the conventional method. , The pH rise of the solution in the reaction tank at the time of introduction of raw water is suppressed and the pH range is controlled to be suitable for the ANAMMOX reaction, and stable and efficient denitrification treatment can be performed.

Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
Ammonia nitrogen: 900 mg / L, IC: 350 mg / L, pH: 9.0 synthetic wastewater was prepared. As the one-tank type ANAMMOX reaction tank, a laboratory test apparatus having a reaction tank volume of 4 L was used. As the seed sludge, one-tank type ANAMMOX sludge cultivated in synthetic wastewater was added so that the settling volume was 30% of the tank volume. The water temperature was 32 ° C. The amount of exchanged water per batch was set to 0.8 L, and the batch cycle was set to an aeration step of 6 hr, a sludge settling step of 3 min, and a treated water discharge step of 10 min. The raw water introduction process was started at the same time as the start of the aeration process, and the introduction time was set to 2.4 hr (40% of the aeration process). The results are shown in Table 1.

In this example, although the pH of the liquid in the tank increased from the start of introducing the raw water, the maximum pH remained at 8.2, and after the completion of the raw water introduction process, the ammoniacal nitrogen was removed by the one-tank type ANAMMOX reaction to remove the pH of the liquid in the tank. The pH gradually decreased to 7.1 at the end of the reaction. At this time, the nitrogen removal rate was 87%, and the treated water had an ammoniacal nitrogen concentration of 1 mg / L or less, a nitrite nitrogen concentration of 5.2 mg / L, and a nitrate nitrogen concentration of 113 mg / L. It was considered that ammoniacal nitrogen was removed by the type ANAMMOX reaction.

[Comparative Example 1]
It was carried out in the same manner as in Example 1 except that aeration was not performed when the raw water was introduced. The results are shown in Table 1.

In this comparative example, the pH of the solution in the reaction vessel increased to 9.0 in the raw water introduction step. Although the pH gradually decreased in the aeration step, the pH at the end of the aeration step was 8.4, in which the activity of ANAMMOX bacteria decreased. The treated water had an ammoniacal nitrogen concentration of 88 mg-N / L, a nitrite nitrogen concentration of 279 mg / L, a nitrate nitrogen concentration of 47 mg / L, and a nitrogen removal rate of 54%. In addition, nitrite nitrogen, which has a strong inhibitory effect on ANAMMOX bacteria, was accumulated in a high concentration in the reaction vessel.

<Result>
When the pH of the raw water is high, aeration at the time of introduction of the raw water prevents treatment failure due to inactivation or inhibition of ANAMMOX bacteria due to the pH exceeding 8.3 during the aeration process, and stably removes 80% or more of nitrogen. You can get the rate.

[Examples 2-1 to 3 and Comparative Examples 2-1 to 3]
In Example 1, the conditions of synthetic wastewater were changed to ammoniacal nitrogen: 1,800 mg / L, IC: 1,200 mg / L, pH: 9.0, and the raw water introduction time was changed as shown in Table 2 to introduce raw water. The time / aeration time ratio was varied in the range of 10-100%.
The pH of the liquid in the tank and the nitrogen removal rate during the aeration step (reaction step) at this time were as shown in Table 2.

As shown in Table 2, when the raw water introduction time / aeration time ratio was 10 to 30%, the nitrogen removal rate decreased to 34 to 67%.
When the IC in the raw water is high, the pH decrease due to the reaction cannot catch up with the pH increase due to the introduction of the raw water, and the pH of the solution in the tank exceeds 8.3. It is estimated that more than 50 mg-N / L of nitrogen was accumulated and the ANAMMOX bacteria were inhibited by nitrite nitrogen.
On the other hand, when the raw water introduction time / aeration time ratio is 40% or more and the raw water is introduced at a low flow rate, the pH of the liquid in the tank is stably 8.3 or less, and the nitrogen removal rate is as high as 80 to 89%. was gotten.

<Result>
When the raw water IC is high, the raw water is introduced at a low flow rate over time so that the raw water introduction time / aeration time ratio is 40% or more, so that the pH during the aeration process does not exceed 8.3. By preventing the inactivation and inhibition of ANAMMOX bacteria, it is possible to stably obtain a nitrogen removal rate of 80% or more.

[Examples 3-1 to 3, Comparative Examples 3-1 to 3]
In Example 1, the conditions of synthetic wastewater were changed to ammoniacal nitrogen: 1,800 mg / L, IC: 150 mg / L, pH: 10, and the raw water introduction time was changed as shown in Table 3, and the raw water introduction time / aeration time ratio. Was changed in the range of 10 to 100%.
The pH of the liquid in the tank and the nitrogen removal rate during the aeration step (reaction step) at this time were as shown in Table 3.

As shown in Table 3, when the pH of the raw water was higher, the nitrogen removal rate was 28% or less when the raw water introduction time / aeration time ratio was 10 to 30%. In particular, when it was 10 to 20%, the pH of the liquid in the tank during the aeration step exceeded 9, so it is estimated that the activity of nitrifying bacteria in addition to ANAMMOX bacteria also decreased. Since the pH was high, stripping of ammonia occurred, and it was difficult to measure the nitrogen removal rate by biological treatment.
On the other hand, when the raw water introduction time / aeration time ratio is 40% or more and the raw water is introduced at a low flow rate, the pH of the liquid in the tank is stably 8.3 or less, and the nitrogen removal rate is as high as 80 to 89%. was gotten.

<Result>
When the pH of the raw water is higher, the pH at the initial stage of the aeration process does not exceed 8.3 by introducing the raw water at a low flow rate over time so that the raw water introduction time / aeration time ratio becomes 40% or more. , It is possible to stably obtain a nitrogen removal rate of 80% or more by preventing volatilization due to ammonia stripping and inactivation of ANAMMOX bacteria.

1 Reaction tank 2 Mixed sludge 3 Reaction solution 4 Air diffuser L1 Raw water introduction path L2 Chemical introduction path L3 Treated water extraction path L4 Air introduction path 10 Control device

Claims (5)

This is a method of batch denitrification using a reaction tank containing mixed sludge of ammonia-oxidizing bacteria and ANAMMOX bacteria using ammonia nitrogen-containing wastewater as raw water, and the aeration step is performed in the raw water introduction step into the reaction tank. There rows simultaneously, and measuring the pH of the reaction tank, denitrification method ammonium nitrogen-containing waste water, characterized in that stopping the introduction of the raw water when the pH measured value exceeds 8.3. Oite to claim 1, denitrification method ammonium nitrogen-containing waste water, wherein the pH of the raw water is not more than 10 greater than 8.3. The method for denitrifying ammonia-based nitrogen-containing wastewater according to claim 1 or 2 , wherein the raw water has an inorganic carbonic acid concentration of 150 to 3,000 mg / L. The method for denitrifying ammonia-based nitrogen-containing wastewater according to any one of claims 1 to 3 , wherein the raw water is a dehydrated filtrate of an anaerobic digestive juice. A denitrification treatment apparatus for performing the denitrification treatment method for ammoniacal nitrogen-containing wastewater according to claim 1 or 2.
A reaction tank containing mixed sludge of ammonia-oxidizing bacteria and ANAMMOX bacteria,
Raw water introduction means for introducing ammonia nitrogen-containing wastewater as raw water into the reaction vessel,
A treated water discharge means for discharging denitrified treated water from the reaction tank,
Aeration means for aerating the reaction solution in the reaction vessel and
A pH measuring means for measuring the pH of the liquid in the reaction vessel,
It is a batch type one-tank type ANAMMOX reaction device having an operation of the raw water introduction means and a control means for controlling the operation of the aeration means.
The control means controls the aeration of the inside of the reaction vessel by the aeration means when the raw water is introduced by the raw water introduction means, and when the measured value of the pH measuring means exceeds 8.3, the raw water introduction means. A denitrification treatment device for ammonia nitrogen-containing wastewater, which is characterized by controlling the introduction of raw water by the water.

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