JPWO2011148949A1 - Biological nitrogen removal method using anaerobic ammonia oxidation reaction - Google Patents

Abstract

Nitrite-type nitrifying bacteria contributing to nitrite-type nitrification reaction and anaerobic ammonia-oxidation contributing to anaerobic ammonia oxidation reaction in treated water containing dissolved nitrogen flowing into the reaction tank under aerobic conditions Two dominant species with bacteria, or nitrous acid-type nitrifying bacteria that contribute to nitrite-type nitrification reaction, anaerobic bacteria that decomposes soluble nitrogen other than ammonia to ammonia and anaerobic ammonia oxidation reaction Anaerobic ammonia-oxidizing bacteria, anaerobic ammonia-oxidizing reaction is used to denitrify water to be treated by flowing a carrier carrying a microbial membrane containing three dominant species on the surface, anaerobic It is a biological nitrogen removal method using ammonia oxidation reaction. In the biological nitrogen removal method, the amount of nitrite produced by the nitrite-type nitrification reaction of the nitrite-type nitrifying bacteria is adjusted so that the water to be treated becomes alkaline in the reaction tank. The carrier input rate is adjusted so that the nitric acid type nitrification reaction is suppressed.

Description

  The present invention relates to a biological nitrogen removal method using an anaerobic ammonia oxidation reaction for water to be treated containing soluble nitrogen such as ammoniacal nitrogen, and more specifically, water to be treated to be treated. The present invention relates to a biological nitrogen removal method capable of denitrification at a practical level while relaxing restrictions on the ammoniacal nitrogen concentration, water temperature in the reaction tank, and DO value.

  2. Description of the Related Art Conventionally, a technique for denitrifying using microbial bacteria has been used for water to be treated containing ammoniacal nitrogen, for example, sewage. This biological nitrogen removal technology converts ammonia nitrogen in water to be treated into nitrogen gas through a two-stage biological reaction, nitrification and denitrification, and discharges it out of the system. In the nitrification process, ammonia nitrogen is removed. Is oxidized to nitrite nitrogen using oxygen by an ammonia-oxidizing bacterium under aerobic conditions, and then the nitrite nitrogen is oxidized to nitrate nitrogen by a nitrite-oxidizing bacterium. Nitrate nitrogen and nitrate nitrogen are converted into nitrogen gas by denitrifying bacteria under anoxic conditions while using organic substances as electron donors.

  However, such biological nitrogen removal technology requires a large amount of oxygen in the nitrification step, while a large amount of organic substances such as methanol must be added in the denitrification step, which generally increases the running cost. Met. As a new biological nitrogen removal technique that solves such technical problems, a biological nitrogen removal method and a biological nitrogen removal apparatus using an anaerobic ammonia oxidation reaction are used. Here, the anaerobic ammonia oxidation reaction is a biological reaction using anaerobic ammonia oxidizing bacteria. Under anaerobic conditions, anaerobic ammonia oxidizing bacteria convert ammonia nitrogen to an electron donor and nitrite nitrogen to electrons. This is a group of denitrifying microorganisms that can react with each other as an acceptor to generate nitrogen gas, and are denitrifying microorganisms that do not require the addition of organic substances during denitrification.

  An example of a biological nitrogen removal method and a biological nitrogen removal apparatus using such anaerobic ammonia oxidation reaction is disclosed in Patent Document 1. This biological nitrogen removal method and biological nitrogen removal apparatus are generally composed of a partial nitrification tank, a pH adjustment tank, and a denitrification tank from the upstream side to the downstream side of the water to be treated. More specifically, the partial nitrification tank aerates the ammonia nitrogen-containing liquid in the presence of ammonia oxidizing bacteria, oxidizes a part of the ammonia nitrogen component to nitrite nitrogen, and the denitrification tank is anaerobic. In the presence of ammonia-oxidizing bacteria, nitrite nitrogen and ammonia nitrogen in the treated water in the partial nitrification tank are reacted to convert them into nitrogen gas, and the pH adjustment tank uses the treated water in the denitrification tank partially. The pH is adjusted by circulation to a nitritation tank. According to the biological nitrogen removing method and the biological nitrogen removing apparatus having such a configuration, aeration power for nitrification can be reduced, organic substances such as methanol need not be added, and the amount of generated sludge can be reduced. Is possible.

  However, in such a biological nitrogen removal method and biological nitrogen removal apparatus, a partial nitrification tank, a pH adjustment tank, and a denitrification tank are separately provided, and in each of the partial nitrification tank and the denitrification tank, partial nitrification is performed. Since it is necessary to adjust the pH value required for the reaction and the pH value required for the denitrification reaction, the equipment cost is high as a biological nitrogen removal device, and the biological nitrogen removal method is a simple method. I couldn't say.

  For example, Non-Patent Document 1 discloses a biological nitrogen removal apparatus and biological nitrogen removal method using an anaerobic ammonia oxidation reaction that solves such technical problems. This biological nitrogen removal apparatus uses a partial nitrification tank and a denitrification tank as a single tank, and in this single tank, a partial nitrification reaction and a denitrification reaction are not required without adjusting the pH value. In order to remove nitrogen. More specifically, in a single tank into which water to be treated is introduced, nitrite-type nitrifying bacteria contributing to nitrite-type nitrification reaction are predominated as an anaerobic ammonia-oxidizing bacteria. A nitrous acid type is added under aerobic conditions by introducing a carrier carrying a two-layer microbial membrane, which is present inside as a seed, on the surface, and flowing the carrier in water to be treated containing ammoniacal nitrogen. Mainly under anaerobic conditions in which ammonia nitrogen is partially oxidized to nitrite nitrogen by nitrifying bacteria and then blocked from oxygen in the treated water by the presence of nitrite nitrifying bacteria. Nitrogenous nitrogen and ammoniacal nitrogen are reacted by anaerobic ammonia oxidizing bacteria present in the inner layer of the microbial membrane, and converted into nitrogen gas for denitrification. According to the biological nitrogen removal apparatus and biological nitrogen removal method utilizing such anaerobic ammonia oxidation reaction, the cost can be reduced by simplifying the equipment, and the adjustment of the pH value is not required. A simplified nitrogen removal method can also be achieved.

  However, the biological nitrogen removal method using the anaerobic ammonia oxidation reaction has the following technical problems. In other words, due to restrictions on the ammonia nitrogen concentration of the water to be treated, the water temperature in the reaction tank, and the DO value, biological nitrogen removal is unconditionally performed if the water to be treated contains ammoniacal nitrogen. It is not that you can do.

More specifically, according to the biological nitrogen removal method using the conventional anaerobic ammonia oxidation reaction, denitrification is performed on the water to be treated containing ammonia nitrogen using the following reaction process. Can do.
(1) Nitrite-type nitrification reaction: NH ₄ ⁺ + 1.5O ₂ → NO ₂ ⁻ + H ₂ O + 2H ⁺
(2) Anaerobic ammonia oxidation reaction: 0.75NH ₄ ⁺ + NO ₂ ⁻ → 0.77N ₂ +0.19 NO ₃ ⁻ + 1.5H ₂ O + 0.10H ⁻

  More specifically, in the treated water containing ammonia nitrogen under aerobic conditions, nitrite type nitrifying bacteria that contribute to nitrite type nitrification reaction are dominant species and contribute to anaerobic ammonia oxidation reaction An anaerobic ammonia-oxidizing bacterium that predominates is placed in a form surrounded by the nitrite-type nitrifying bacterium, and a carrier carrying two layers of microbial membranes on the surface is disposed on the inside, thereby predominating species Nitrite is produced by causing a nitrite-type nitrification reaction (1) by the nitrite-type nitrifying bacteria present on the outside. Next, anaerobic conditions were satisfied by being present in the inner layer of the microbial membrane in a form surrounded by nitrite-type nitrifying bacteria based on the ammoniacal nitrogen in the treated water and the generated nitrite nitrogen. In the state, the anaerobic ammonia oxidizing bacterium, which is the reaction of (2), is caused by the anaerobic ammonia oxidizing bacteria to generate nitrogen.

However, during the process of denitrification using such anaerobic ammonia oxidation reaction, nitric acid is further oxidized by nitric acid-type nitrifying bacteria as shown in the following reaction formula to produce nitric acid. Will be.
(3) Nitric acid type nitrification reaction: NO ₂ ⁻ + 0.5O ₂ → NO ₃ ⁻ + H ₂ O + 2H ⁺
Therefore, in order to implement a biological nitrogen removal method using an anaerobic ammonia oxidation reaction at a practical level, while increasing the amount of nitrous acid produced by the nitrite type nitrification reaction (1), It is necessary to secure ammonia nitrogen and nitrite nitrogen necessary for the anaerobic ammonia oxidation reaction (2) by inhibiting the nitrate nitrification reaction (3).

  In this regard, as the parameter factors that affect the nitrite-type nitrification reaction and the nitrate-type nitrification reaction, the ammoniacal nitrogen concentration of the water to be treated, the water temperature in the tank, and the DO value can be considered.

  FIGS. 13 to 15 show the temperature of treated water, DO (dissolved oxygen amount) in treated water, and the treated water in relation to the growth rate or reaction rate of nitrite-type nitrifying bacteria and nitrate-type nitrifying bacteria, respectively. It is the graph which showed typically the influence which ammonia nitrogen concentration gives. As shown in FIG. 13, the higher the temperature of the water to be treated, the higher the growth rate of the nitrite type nitrifying bacteria compared to the nitrate type nitrifying bacteria. Therefore, the temperature of the water to be treated is preferably high. Further, as shown in FIG. 14, the lower the DO (dissolved oxygen amount) in the water to be treated, the lower the reaction rate of nitrate nitrifying bacteria compared to the nitrite type nitrifying bacteria. As long as the aerobic condition is satisfied, it is preferably low. Furthermore, as shown in FIG. 15, the higher the ammonia nitrogen concentration in the treated water, the lower the reaction rate of the nitrate nitrifying bacteria compared with the nitrite type nitrifying bacteria. Is preferably high.

  As described above, in order to suppress the nitric acid-type nitrification reaction (3) while increasing the amount of nitrous acid produced by the nitrite-type nitrification reaction (1), conventionally, If the water to be treated contains ammoniacal nitrogen, it is unconditionally removed at a practical level using an anaerobic ammonia oxidation reaction. Nitrogen was not possible, for example, wastewater with high ammoniacal nitrogen concentration at high temperatures such as industrial wastewater and return sludge water, and municipal wastewater and domestic wastewater were treated with ammoniacal nitrogen at lower temperatures. Since the concentration was lower, it was difficult to apply as it was.

JP 2006-88092 A

Joumal of Zhejiang University SCIENCE B, 2008, pp 416-426, “Anaerobic ammonium oxidation for treatment of ammonium-rich wastewaters”

  In view of the above technical problems, the problem of the present invention is to ease the denitrification process while relaxing the restrictions on the ammonia nitrogen concentration of the water to be treated, the water temperature in the reaction tank, and the DO value. Another object of the present invention is to provide a biological nitrogen removal method utilizing an anaerobic ammonia oxidation reaction that can ensure a practical level of denitrification efficiency.

  In order to achieve the above object, the present invention provides the following biological nitrogen removal method.

[1] Nitrite-type nitrifying bacteria that contribute to the nitrite-type nitrification reaction and anaerobic ammonia-oxidation reaction in the treated water containing dissolved nitrogen that has flowed into the reaction tank under aerobic conditions Two dominant species with oxidative ammonia-oxidizing bacteria, or nitrous acid-type nitrifying bacteria that contribute to nitrite-type nitrification reaction and aerobic bacteria that decompose soluble nitrogen other than ammonia into ammonia and anaerobic ammonia oxidation reaction Denitrification from treated water using anaerobic ammonia oxidation reaction by flowing a carrier carrying a microbial membrane containing three dominant species with contributing anaerobic ammonia oxidizing bacteria on the surface A biological nitrogen removal method utilizing an anaerobic ammonia oxidation reaction, wherein the water to be treated is adjusted to be alkaline in the reaction tank, and the nitrite type nitrification of the nitrite type nitrifying bacterium Sub-by reaction Biology using anaerobic ammonia oxidation reaction, which adjusts the carrier input rate (total surface area of the carrier per unit volume of the reaction tank) so that the amount of acid produced is at a level that inhibits the nitric acid-type nitrification reaction Nitrogen removal method.

[2] The biological nitrogen removal method using an anaerobic ammonia oxidation reaction according to [1], wherein the pH of the water to be treated is adjusted to 7.3 to 8.5 in the reaction tank.

[3] The anaerobic ammonia oxidation reaction according to [1] or [2], wherein the carrier input rate is adjusted so that the inflow soluble nitrogen load is 2.5 to 11.5 g / m ² carrier / day. Biological nitrogen removal method using

[4] The biological nitrogen removal method using an anaerobic ammonia oxidation reaction according to [1] or [2], wherein the carrier input rate is adjusted to 4 to 55 m ² / m ³ .

[5] Measure the ammonia nitrogen (NH ₄ -N) concentration, nitrite nitrogen (NO ₂ -N) concentration and nitrate nitrogen (NO ₃ -N) concentration of the water to be treated flowing out of the reaction tank, Combinations of the following (a), (b) and (c), the following (a) and (c), the following (b) and (c), the following (d) alone and the following (e) Denitrification from the water to be treated using an anaerobic ammonia oxidation reaction while adjusting the amount of aeration in the reaction tank using any means selected from the group consisting of a single group [1] to The biological nitrogen removal method using the anaerobic ammonia oxidation reaction according to any one of [4].
(A) When the NO ₃ —N concentration exceeds a certain set value, the aeration amount is decreased.
(B) The amount of aeration is reduced when the NO ₂ —N concentration exceeds a certain set value.
(C) When the NH ₄ —N concentration exceeds a certain set value, the aeration amount is increased.
(D) The aeration amount is decreased when the NO ₃ —N concentration becomes a certain set value or more, and the aeration amount is increased when the NO ₃ —N concentration becomes a certain set value or less.
(E) The amount of aeration is decreased when the NO ₂ —N concentration becomes a certain set value or more, and the amount of aeration is increased when the NO ₂ —N concentration becomes a certain set value or less.

[6] Nitrite-type nitrifying bacteria that contribute to nitrite-type nitrification reaction and anaerobic ammonia-oxidation reaction in treated water containing dissolved nitrogen that has flowed into the reaction tank under aerobic conditions Two dominant species with oxidative ammonia-oxidizing bacteria, or nitrous acid-type nitrifying bacteria that contribute to nitrite-type nitrification reaction and aerobic bacteria that decompose soluble nitrogen other than ammonia into ammonia and anaerobic ammonia oxidation reaction Denitrification from treated water using anaerobic ammonia oxidation reaction by flowing a carrier carrying a microbial membrane containing three dominant species with contributing anaerobic ammonia oxidizing bacteria on the surface A biological nitrogen removal method utilizing an anaerobic ammonia oxidation reaction, wherein the inside of the reaction tank is on the downstream side where the treated water flows out from the upstream side where the treated water flows in Toward The partition is divided into a plurality of partitions by partition walls that do not completely block the flow of water, and the nitrite type of the nitrite type nitrifying bacterium is adjusted in such a state that the treated water becomes alkaline in each partition An anaerobic ammonia oxidation reaction that adjusts the carrier input rate (total surface area of the carrier per unit volume of the reaction tank) so that the amount of nitrous acid produced by the nitrification reaction is at a level that inhibits the nitric acid-type nitrification reaction. Biological nitrogen removal method used.

[7] The biological nitrogen removal method using an anaerobic ammonia oxidation reaction according to [6], wherein the pH of the water to be treated is adjusted to 7.3 to 8.5 in each compartment.

[8] The carrier input rate is adjusted so that the inflow soluble nitrogen load is 2.5 to 11.5 g / m ² carrier / day in each of the compartments, according to [6] or [7]. Biological nitrogen removal method using anaerobic ammonia oxidation reaction.

[9] The biological nitrogen removal method using an anaerobic ammonia oxidation reaction according to [6] or [7], wherein the carrier input rate is adjusted to ⁴ to 55 m ² / m ³ in each of the compartments.

[10] Ammonia nitrogen (NH ₄ -N) concentration, nitrite nitrogen (NO ₂ -N) concentration and nitrate nitrogen (NO ₃ -N) concentration of water to be treated in each compartment are measured, In the partition upstream of any partition among the partitions partitioning each partition, the following combinations (a), (b) and (c), combinations (a) and (c) below, The aeration amount is adjusted using any means selected from the group consisting of the combination of b) and (c), the following (d) alone and the following (e) alone, In the compartment, the following combinations (f), (g) and (h), the following (f) and (h), the following (g) and (h), the following (i) alone and (J) Adjusting the amount of aeration using any means selected from the group consisting of the following The biological nitrogen removal method using an anaerobic ammonia oxidation reaction according to any one of [6] to [9], wherein denitrification is performed from water to be treated using an anaerobic ammonia oxidation reaction.
(A) When the NO ₃ —N concentration exceeds a certain set value, the aeration amount is decreased.
(B) The amount of aeration is reduced when the NO ₂ —N concentration exceeds a certain set value.
(C) When the NH ₄ —N concentration exceeds a certain set value, the aeration amount is increased.
(D) The aeration amount is decreased when the NO ₃ —N concentration becomes a certain set value or more, and the aeration amount is increased when the NO ₃ —N concentration becomes a certain set value or less.
(E) The amount of aeration is decreased when the NO ₂ —N concentration becomes a certain set value or more, and the amount of aeration is increased when the NO ₂ —N concentration becomes a certain set value or less.
(F) Aeration is stopped when the NO ₃ —N concentration exceeds a certain set value.
(G) Aeration is stopped when the NO ₂ —N concentration exceeds a certain set value.
(H) Aeration is started when the NH ₄ —N concentration exceeds a certain set value.
(I) Aeration is stopped when the NO ₃ —N concentration becomes a certain set value or more, and aeration is started when the NO ₃ —N concentration becomes a certain set value or less.
(J) Aeration is stopped when the NO ₂ —N concentration becomes a certain set value or more, and aeration is started when the NO ₂ —N concentration becomes a certain set value or less.

[11] The carrier is an aerobic bacterium that decomposes nitrous acid type nitrifying bacteria that contribute to nitrite type nitrification reaction, or decomposes soluble nitrogen other than ammonia into ammonia, and nitrite type that contributes to nitrite type nitrification reaction Two layers of microbial membranes with nitrifying bacteria as the dominant species, and anaerobic ammonia oxidizing bacteria that contribute to the anaerobic ammonia oxidation reaction as the dominant species, surrounded by the nitrite-type nitrifying bacteria, inside The biological nitrogen removal method using the anaerobic ammonia oxidation reaction according to any one of [1] to [10], wherein is supported on a surface portion.

[12] Any one of [1] to [11], wherein denitrification is performed from the treated water using an anaerobic ammonia oxidation reaction in a state where the ORP (redox potential) of the treated water is −150 mV or less. A biological nitrogen removal method using the anaerobic ammonia oxidation reaction described in 1.

[13] The anaerobic ammonia oxidation reaction according to any one of [1] to [12], wherein denitrification is performed from the treated water using an anaerobic ammonia oxidation reaction without causing activated sludge to flow into the reaction tank. Biological nitrogen removal method using

[14] Utilizing the anaerobic ammonia oxidation reaction according to any one of [1] to [13], wherein the water to be treated containing soluble nitrogen is waste water having a normal temperature and a soluble nitrogen concentration of 50 mg / L or less. Biological nitrogen removal method.

  According to the present invention, after adjusting the water to be treated in the reaction tank to be alkaline, the ammonia nitrogen concentration of the water to be treated, which is to be treated, by appropriately adjusting the carrier charging rate in the water to be treated, While relaxing the restrictions on the water temperature and DO value in the reaction vessel, a practical denitrification effect can be obtained by utilizing an anaerobic ammonia oxidation reaction.

It is the schematic which shows an example of the water treatment system for enforcing the biological nitrogen removal method which concerns on this invention. It is the schematic around the reaction tank which concerns on embodiment of this invention. It is a cross-sectional schematic diagram which shows an example of the support | carrier used within the reaction tank which concerns on embodiment of this invention. It is a partial cross-sectional schematic diagram which shows another example of the support | carrier used in the reaction tank which concerns on embodiment of this invention. It is a partial cross-sectional schematic diagram which shows another example of the support | carrier used in the reaction tank which concerns on embodiment of this invention. It is a partial cross-sectional schematic diagram which shows another example of the support | carrier used in the reaction tank which concerns on embodiment of this invention. In Example 1 of this invention, it is a graph which shows the time change of each soluble nitrogen concentration of reaction tank inflow water, and soluble nitrogen concentration of reaction tank outflow water. In Example 2 of the present invention, when the carrier input ratio of 90m ² carriers total surface area / ^{m 3} tank volume, ionic nitrogen concentration, a graph showing the _NO X -N concentration and _NH 4 -N concentration each time change is there. In Example 2 of the present invention, when the carrier input ratio is 30 m ² support the total surface area / ^{m 3} tank volume, ionic nitrogen concentration, a graph showing the _NO X -N concentration and _NH 4 -N concentration each time change is there. In Example 2 of the present invention, showing when the carrier input ratio of 7.5 m ² support the total surface area / ^{m 3} tank volume, ionic nitrogen concentration, the _NO X -N concentration and _NH 4 -N concentration each time change It is a graph. In Example 3 of the present invention, is a graph showing when activated sludge concentration of the water to be treated is 16mgSS / L, ionic nitrogen concentration, the _NO X -N concentration and _NH 4 -N concentration each time change. In Example 3 of the present invention, is a graph showing when activated sludge concentration of the water to be treated is 1620mgSS / L, ionic nitrogen concentration, the _NO X -N concentration and _NH 4 -N concentration each time change. It is a graph which shows how the growth rate of each nitrite type nitrifying bacteria and nitrate type nitrifying bacteria changes with water temperature. It is a graph which shows how the reaction rate of each nitrite type nitrifying bacteria and nitrate type nitrifying bacteria changes with DO values. It is a graph which shows how the reaction rate of each nitrite type nitrifying bacteria and nitrate type nitrifying bacteria changes with ammonia nitrogen concentration. It is a graph which shows how the growth rate of each nitrite type nitrifying bacteria and nitrate type nitrifying bacteria changes with pH values. It is a schematic diagram showing the distribution of ammonia nitrogen concentration, nitrite nitrogen concentration, and nitrate nitrogen concentration in the thickness direction of the carrier along with the change in DO value. In the case of the prior art in which nitrification is performed by ammonia oxidizing bacteria and nitrite oxidizing bacteria Indicates. It is a schematic diagram showing the distribution of ammonia nitrogen concentration, nitrite nitrogen concentration, and nitrate nitrogen concentration in the thickness direction of the carrier together with changes in DO value, and is a conventional technique for denitrification by ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria This case is shown. It is a schematic diagram showing the distribution of ammonia nitrogen concentration, nitrite nitrogen concentration and nitrate nitrogen concentration in the thickness direction of the carrier together with the change of DO value, and the present invention denitrifies by ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria This case is shown. Soluble nitrogen removal rate, NO 2 _-N product concentration and NO 3 _-N product concentration is a graph showing how the changes by the ratio of DO on solubility nitrogen load. Soluble nitrogen removal rate, NO 2 _-N product concentration and NO 3 _-N product concentration is a graph showing how the changes by the ratio of DO on solubility total organic carbon load. It is the schematic which shows an example of the adjustment method of the aeration amount in a reaction tank. It is the schematic which shows another example of the adjustment method of the aeration amount in a reaction tank. It is the schematic which shows an example of the adjustment method of ORP of to-be-processed water. Soluble nitrogen removal rate and NO 3 _-N product concentration is a graph showing how the varying the flows solubility nitrogen load. In case the inflow solubility nitrogen load is relatively low, NO 3 _-N product concentration is a graph showing how the varying the flows solubility nitrogen load. It is a graph which shows how a soluble nitrogen removal rate changes with the oxidation-reduction potential of reaction tank inflow water. FIG. 3 is a flow chart when nitrogen removal is performed by the biological nitrogen removal method of the present invention, and soluble organic matter and phosphorus are removed using activated sludge.

  Hereinafter, the present invention will be described based on specific embodiments, but the present invention should not be construed as being limited thereto, and based on the knowledge of those skilled in the art without departing from the scope of the present invention. Various changes, modifications, and improvements can be added.

  In the biological nitrogen removal method according to the present invention, the reaction in the above (3) is carried out by adjusting the carrier input rate in the treated water in a state where the treated water is adjusted to be alkaline in the reaction tank. Necessary for the anaerobic ammonia oxidation reaction (2) by increasing the amount of nitrous acid produced by the nitrite nitrification reaction (1) as the nitric acid nitrification reaction is suppressed. Secures ammonia nitrogen and nitrite nitrogen.

  FIG. 16 is a graph schematically showing the influence of the pH of the water to be treated on the growth rates of nitrite-type nitrifying bacteria and nitrate-type nitrifying bacteria. As shown in FIG. 16, the higher the pH of the water to be treated, the lower the growth rate of nitrate-type nitrifying bacteria compared to nitrite-type nitrifying bacteria. Therefore, the nitrate-type nitrifying reaction (3) is suppressed. Therefore, it is preferable that the pH of the water to be treated is higher. In addition, when the present inventors repeatedly examined a biological nitrogen removal method using an anaerobic ammonia oxidation reaction, when the water to be treated is alkaline, the anaerobic ammonia oxidation reaction of (2) occurs. It was found that the removal rate of soluble nitrogen was improved. Based on these findings, the biological nitrogen removal method according to the present invention performs biological nitrogen removal using an anaerobic ammonia oxidation reaction in a state where the water to be treated is adjusted to be alkaline in the reaction tank. Do.

  As a method for adjusting the water to be treated to be alkaline in the reaction tank, a method of adding an alkali agent to the water to be treated can be suitably employed. Although the kind of alkaline agent to be used is not particularly limited, for example, sodium carbonate, sodium hydrogen carbonate, sodium hydroxide, calcium hydroxide (slaked lime) and the like can be suitably used.

  In addition, as specific pH of the to-be-processed water in a reaction tank, 7.3-8.5 are preferable. When the pH of the water to be treated becomes 7.3 or more, the effect of improving the removal rate of soluble nitrogen becomes remarkable, and an apparently high removal rate of soluble nitrogen is obtained as compared with the case where the water to be treated is acidic or neutral. It is done. In addition, when the pH of the water to be treated is up to 8.5, the removal rate of soluble nitrogen increases as the pH increases. However, when the pH exceeds 8.5, the removal rate of soluble nitrogen reaches a peak. . Therefore, by reducing the pH to 8.5 or less, wasteful consumption of the alkaline agent can be suppressed and the running cost can be reduced.

  In the biological nitrogen removal method according to the present invention, after the water to be treated is adjusted to be alkaline in the reaction tank as described above, the carrier is determined based on the dissolved nitrogen concentration in the water to be treated. Adjust the input rate. Here, the carrier charging rate is the total surface area of the carrier per unit volume of the reaction tank. For example, the carrier input rate is reduced when the concentration of soluble nitrogen in the water to be treated is low. Next, the carrier is caused to flow so as to be uniformly distributed in the reaction vessel. Thereby, it is possible to ensure the ammonia load per unit time and the surface area of the support uniformly throughout the entire reaction tank. In such a state, the nitrite type nitrification bacteria contained as one of the dominant species in the microbial membrane supported on the surface of each carrier cause a nitrite type nitrification reaction. Decreasing the rate increases the ammonia load per unit surface area of the carrier, and as a result, the number of nitrite type nitrifying bacteria per unit surface area of the carrier due to the growth of nitrite type nitrifying bacteria that contribute to the nitrite type nitrifying reaction. Increases, the microbial membrane thickness increases, and the removal rate of ammonia nitrogen per surface area of the carrier increases.

  By adjusting the carrier input rate in this way, the film thickness of the microbial membrane containing nitrite type nitrifying bacteria as one of the dominant species increases, and the amount of nitrite produced by the nitrite type nitrification reaction increases. When the amount of nitrous acid produced by the reaction reaches a level that inhibits the nitric acid-type nitrification reaction, the nitrous acid required for the anaerobic ammonia oxidation reaction can be secured without being converted to nitric acid. It becomes possible. As a result, the removal rate of nitrogen per unit surface area of the carrier increases, and it is possible to ensure a nitrogen removal rate commensurate with the transfer rate of ammonium ions from the liquid phase to the microbial membrane. As described above, it is necessary to employ a carrier that can support the microbial membrane even when the thickness of the microbial membrane increases.

  The above points will be described in more detail with reference to FIGS. 17A to 17C. FIGS. 17A to 17C show how the ammonia nitrogen concentration, nitrite nitrogen concentration, nitrate nitrogen concentration and nitrogen gas concentration change along with the DO value at the surface of the carrier toward the inside of the carrier. FIG. 17A schematically shows an initial biological nitrogen removal technique that requires a large amount of oxygen, FIG. 17B shows a conventional biological nitrogen removal technique that utilizes an anaerobic ammonia oxidation reaction, and FIG. FIG. 17C shows a biological nitrogen removal technique using an anaerobic ammonia oxidation reaction according to the present invention. In each figure, the horizontal length of the rectangular portion means the film thickness of the microbial membrane supported on the surface portion of the carrier, and the left side in the drawing is the surface portion of the microbial membrane. Further, the vertical length of the rectangular portion indicates the ammonia nitrogen concentration, the nitrite nitrogen concentration, the nitrate nitrogen concentration, and the nitrogen concentration. For example, in FIG. The position where the ammonia nitrogen concentration is maximum but the DO value and ammonia nitrogen concentration decrease and the nitrite nitrogen concentration increases and the DO value becomes zero toward the inner side of the film (right side in the drawing). , The concentration of nitrite nitrogen is higher than the concentration of ammonia nitrogen, and further toward the inside of the membrane, the concentration of nitrate nitrogen and nitrogen increases, while the concentration of ammonia nitrogen and nitrite nitrogen decreases. doing.

  17A to 17C, in FIG. 17A, the nitrate nitrogen concentration starts to increase from the surface of the microbial membrane, and after the ammonia nitrogen concentration becomes zero, the nitrate nitrogen concentration occupies the whole. In contrast, in FIGS. 17B and 17C, at the position where the DO value becomes zero, the nitrite nitrogen concentration and the ammonia nitrogen concentration are secured, thereby causing an anaerobic ammonia oxidation reaction under anaerobic conditions. The nitrogen concentration increases with the nitrate nitrogen concentration. In FIG. 17B and FIG. 17C, if the nitrite nitrogen concentration and the ammonia nitrogen concentration at the position where the DO value is zero are compared, it is caused by the difference in the film thickness of the microbial membrane due to the adjustment of the carrier input rate. Thus, the nitrite nitrogen concentration is higher in FIG. 17C where the thickness of the microbial membrane is thicker, thereby suppressing the subsequent nitric acid-type nitrification reaction.

  As described above, conventionally, the ammonia nitrogen concentration of the water to be treated, the water temperature in the reaction tank, and the DO value for the promotion of the nitrite type nitrification reaction and the suppression of the nitrate type nitrification reaction In the present invention, by utilizing the fact that the production of nitrous acid contributes to the inhibition of the nitric acid type nitrification reaction, the nitrite type nitrification reaction is promoted and the nitric acid type is adjusted. In order to achieve suppression of nitrification reaction at the same time, by promoting nitrite type nitrification reaction at a level that causes suppression of nitrate type nitrification reaction, the concentration of ammonia nitrogen in the water to be treated, It is possible to obtain a practically high denitrification effect by utilizing an anaerobic ammonia oxidation reaction while relaxing the restrictions on the water temperature and DO value.

FIG. 1 is a schematic view showing an example of a water treatment system for carrying out the biological nitrogen removal method according to the present invention. As shown in FIG. 1, the water treatment system 10 includes a first precipitation tank 12, a reaction tank 14, a mixing tank 16, and a second precipitation from the upstream side to the downstream side of the water to be treated. The tank 18, the pH meter 34, the DO meter 20, and the PO ₄ meter 22, the alkaline agent injection pump 36, and the flocculant injection pump 24 are roughly configured.

  The water to be treated that can be treated in the present invention is a nitrogen-containing liquid containing soluble nitrogen, and may contain ammonia nitrogen, nitrite nitrogen, organic nitrogen, and other nitrogen, Sewage, human waste, food wastewater, factory wastewater, and other industrial wastewater. The present invention enables denitrification at a practical level using an anaerobic ammonia oxidation reaction while relaxing restrictions on the ammonia nitrogen concentration of the water to be treated, the water temperature in the reaction tank, and the DO value. For example, the present invention is also applicable to municipal sewage and domestic wastewater having a low nitrogen concentration at room temperature and a soluble nitrogen concentration of 50 mg / L or less.

  The first settling tank 12 is provided for precipitating and removing solids from the water to be treated which has flowed into the tank, and the supernatant liquid in the tank is connected to the downstream reaction tank 14 through a connecting pipe. It is made to flow into. The sludge accumulated at the bottom of the first sedimentation tank 12 is periodically removed from the first sedimentation tank 12, sent to a sludge treatment facility, and disposed of as it is.

  The reaction tank 14 is a single tank, and has three compartments 15a, 15b, 15c from the upstream side into which the water to be treated flows from the upstream side into which the water to be treated flows out to the downstream side from which the water to be treated flows out. It is divided into. The partition wall 30 is provided so as not to completely block the flow of the water to be treated by providing a gap between its lower end and the bottom surface of the reaction tank 14. The compartments communicate with each other, and the water to be treated that has flowed into the reaction tank 14 sequentially flows between the compartments from the upstream compartment to the downstream compartment. In the present invention, as in the example of FIG. 1, it is not essential that the inside of the reaction vessel 14 is partitioned into a plurality of compartments by the partition wall 30, and a reaction vessel without such a partition may be used. Is possible. Further, when the inside of the reaction vessel 14 is partitioned into a plurality of partitions by the partition wall 30, the number of the partitions is not limited to three as in the example of FIG. 1, but may be two or four or more. May be. Conventionally, a nitrification tank that performs a nitrite-type nitrification reaction and an anaerobic ammonia oxidation tank that performs an anaerobic ammonia oxidation reaction are provided separately. In the nitrification tank, ammonia nitrogen in the treated water under aerobic conditions Nitrification process to oxidize nitrite nitrogen to the nitrite nitrogen by the action of ammonia oxidizing bacteria. On the other hand, in the nitrification tank, nitrite nitrogen is used as an electron acceptor, and remaining ammonia nitrogen is used as an electron donor. In this case, the water treatment system 10 performs these aerobic nitrification steps and anaerobic ammonia oxidation reaction steps in a single tank. It is what I did.

  More specifically, in the reaction tank 14, a carrier 26 that carries bacteria is introduced, and an aeration device is installed. With respect to the water to be treated fed from the first sedimentation tank 12 through the pipe, While supplying oxygen with an air diffuser, the to-be-processed water is stirred, The carrier 26 which carries a microbe in the to-be-processed water is made to flow, and it is made to distribute uniformly in to-be-processed water.

  As shown in FIG. 3, the carrier 26 is a granular resin carrier, and the size and shape of the carrier 26 are arbitrary as long as the carrier 26 can retain bacteria even when the carrier 26 flows in the water to be treated. is there. For example, it may be a cylindrical shape, a spherical shape, or the like with an outer dimension of about several millimeters. In the example of FIG. 3, the nitrite type nitrification zone on the surface of the carrier 26 is mainly loaded with nitrite type nitrification bacteria, and the anaerobic ammonia oxidation reaction zone is loaded with mainly anaerobic ammonia oxidation bacteria. Yes. In addition to the nitrite-type nitrifying bacteria, an aerobic bacterium that decomposes soluble nitrogen other than ammonia to form ammonia may be supported in the nitrite-type nitrification zone. More specifically, the carrier 26 is aerobic bacteria that decompose nitrite-type nitrifying bacteria that contribute to the nitrite-type nitrification reaction, or decompose dissolved nitrogen other than ammonia into ammonia and nitrous acid-type nitrifying reactions that contribute to the nitrite-type nitrification reaction. Two layers of nitrate-type nitrifying bacteria exist on the outside as the dominant species, and anaerobic ammonia-oxidizing bacteria that contribute to the anaerobic ammonia oxidation reaction in a form surrounded by the nitrite-type nitrifying bacteria on the inside as the dominant species A microbial membrane is supported on the surface. As a result, in the carrier 26 in the water to be treated, nitrite nitrifying bacteria located on the outer side as the dominant species are set to an aerobic condition, and anaerobic ammonia oxidizing bacteria located on the inner side are nitrite type nitrifying bacteria. The anaerobic condition is ensured in a form surrounded by. In the case where an aerobic bacterium that decomposes soluble nitrogen other than ammonia into ammonia in addition to nitrite type nitrifying bacteria is supported on the outer layer of the two-layer microbial membrane, soluble nitrogen other than ammonia is supported. After being decomposed into ammonia by the aerobic bacterium, it is subjected to a nitrite type nitrification reaction by a nitrite type nitrifying bacterium.

  Microbial membrane contributes to two dominant species, nitrite type nitrifying bacteria contributing to nitrite type nitrification reaction and anaerobic ammonia oxidizing bacteria contributing to anaerobic ammonia oxidation reaction, or nitrite type nitrification reaction If it contains three dominant species of nitrite-type nitrifying bacteria, anaerobic bacteria that decomposes soluble nitrogen other than ammonia to ammonia and anaerobic ammonia oxidizing bacteria that contribute to anaerobic ammonia oxidation reaction The form is not limited to the one having a two-layer structure as shown in FIG. For example, as shown in FIG. 4, nitrite-type nitrifying bacteria 72 and anaerobic ammonia-oxidizing bacteria 74 may exist in the microbial film in a mixed state on the surface portion of the carrier 26. Further, as shown in FIG. 5, when the surface of the carrier 26 has fine irregularities, the anaerobic ammonia oxidizing bacteria 74 are mainly present in the recesses where the anaerobic conditions are easily obtained, and the aerobic conditions are obtained. The easy convex portion may be in a state where nitrite-type nitrifying bacteria 72 are mainly present. Furthermore, as shown in FIG. 6, the nitrite-type nitrifying bacterium 72 is present in an exposed state on the surface portion of the carrier 26 so that the aerobic condition can be easily obtained, and the anaerobic ammonia-oxidizing bacterium 74 is anaerobic condition. May be present in a state of being covered with another bacterium (for example, BOD-oxidizing bacterium) 76 so as to be easily obtained.

  Examples of the nitrite type nitrifying bacteria that contribute to the nitrite type nitrification reaction include bacteria belonging to the genus Nitrosomonas. Examples of aerobic bacteria which decompose soluble nitrogen other than ammonia into ammonia include bacteria belonging to the genus Bacillus.

  As described below, the material of the carrier 26 has strength characteristics that can withstand the shearing force acting on the surface portion of each carrier 26 due to the strong stirring force by the air diffuser, and to be processed. While each carrier 26 flows in water, it is necessary to have water absorbency or hydrophilicity capable of holding nitrite type nitrifying bacteria and anaerobic ammonia oxidizing bacteria on the surface portion. In particular, in the present invention, the charge rate is adjusted according to the dissolved nitrogen concentration, thereby including nitrite-type nitrifying bacteria present on the surface of the carrier 26 as one of the dominant species. When the thickness of the microbial membrane is increased, it is necessary to have a characteristic capable of retaining nitrite-type nitrifying bacteria and anaerobic ammonia oxidizing bacteria even when the thickness of the microbial membrane is increased.

  In this respect, the material of the carrier 26 is, for example, a foamable water-absorbing polyurethane, and has a relatively high concentration mainly of TPU (thermoplastic polyurethane resin), which is a hydrophilic resin, and has strength characteristics. In order to ensure the above, it is preferable to add a crosslinking agent which is a hydrophobic prepolymer.

  Two dominant species, nitrite type nitrifying bacteria contributing to nitrite type nitrification reaction and anaerobic ammonia oxidizing bacteria contributing to anaerobic ammonia oxidation reaction, or nitrite type nitrifying bacteria contributing to nitrite type nitrification reaction A microbe membrane containing three dominant species, an aerobic bacterium that decomposes soluble nitrogen other than ammonia and ammonia and anaerobic ammonia oxidizing bacteria that contribute to the anaerobic ammonia oxidation reaction, is supported on the surface of the carrier For example, after a small amount of sludge containing these bacteria adheres to the surface of the carrier, the carrier is put into a tank containing water containing soluble nitrogen such as sewage and left for several days. Then, it is sufficient to grow the bacteria. When supporting the microbial membrane by such a method, the nitrite type nitrifying bacteria and aerobic bacteria grow under aerobic conditions, and the anaerobic ammonia oxidizing bacteria grow under anaerobic conditions. Even if the operation is not performed, the outer layer of the microbial membrane is dominated by the nitrite-type nitrifying bacteria and aerobic bacteria, and the inner layer is dominated by anaerobic ammonia-oxidizing bacteria.

  The air diffuser is not a diffuser as conventionally used, but an air diffuser having a function of dissolving oxygen in the water to be treated and a stirring function of flowing the water to be treated together with the carrier 26 in the water to be treated. Preferably there is. In this respect, for example, the draft tube aerator 28 is suitable. FIG. 2 shows one of the compartments of the reaction vessel 14 divided into three by the partition wall 30 in FIG. As shown in FIGS. 1 and 2, the draft tube aerator 28 is known. As a basic configuration, the draft tube aerator 28 includes a shaft 42 provided with an impeller 40 at a lower end, a drive device 44 coupled to the shaft 42, and A diffuser pipe 46 positioned immediately below the impeller 40, a blower 32 communicating with the diffuser pipe 46, a draft tube 48 having a diameter substantially the same as the diameter of the impeller 40 and extending downward from the impeller 40; The shaft 42 is rotated by the drive device 44 and the water to be treated is stirred by the impeller 40, and air is sent from the blower 32 to the water to be treated through the air diffuser 46, and the water to be treated and bubbles are sent to the bottom of the tank by the draft tube 48. In addition to increasing the stirring power at the bottom, the oxygen dissolution efficiency is increased. The blower 32 is connected to the DO meter 20 and adjusts the amount of air (aeration amount) sent from the blower 32 according to the DO value in the treated water measured by the DO meter 20, and thus the DO value in the treated water. Is set to an appropriate value.

FIG. 18 shows that the removal rate of soluble nitrogen, the NO ₂ -N production concentration, and the NO ₃ -N production concentration in the treated water denitrified by the biological nitrogen removal method of the present invention are different in DO against the soluble nitrogen load. It is a graph which shows how it changes with ratios. As shown in this graph, if the ratio of DO to soluble nitrogen load is too low, the nitrite type nitrifying bacteria contained in the microbial membrane cannot secure sufficient oxygen, so the amount of nitrite produced by the nitrite type nitrification reaction Becomes insufficient, and only a low soluble nitrogen removal rate can be obtained. On the other hand, if the ratio of DO to soluble nitrogen load is too high, nitrous acid produced by nitrite-type nitrification reaction is further oxidized by nitric acid-type nitrification reaction due to excess oxygen, and nitric acid is produced, and microorganisms Since oxygen reaches the anaerobic ammonia oxidizing bacteria contained in the membrane and the anaerobic conditions cannot be sufficiently satisfied, the anaerobic ammonia oxidation reaction is not promoted and only a low soluble nitrogen removal rate can be obtained.

As described above, DO must be supplied without excess or deficiency with respect to the amount necessary for the nitrogen removal reaction. However, DO is consumed not only by the nitrogen removal reaction but also by organic substances in the water to be treated. It is difficult to adjust the amount of aeration to an appropriate value based only on the load. FIG. 19 shows that the removal rate of soluble nitrogen, the NO ₂ -N production concentration and the NO ₃ -N production concentration in the treated water denitrified by the biological nitrogen removal method of the present invention with respect to the soluble total organic carbon load. It is a graph which shows how it changes with the ratio of DO. As shown in this graph, when the ratio of DO to the soluble total organic carbon load is low, it becomes difficult to secure the amount of DO necessary for the nitrogen removal reaction due to the consumption of DO by organic matter, and only a low soluble nitrogen removal rate is obtained. I can't get it.

Considering these points, it is more preferable to adjust the aeration amount in the reaction tank 14 by a method as shown in FIG. That is, on the downstream side of the reaction tank 14, an NH ₄ -N meter 50 that measures ammonia nitrogen (NH ₄ -N) concentration, and a NO ₂ -N meter 52 that measures nitrite nitrogen (NO ₂ -N) concentration. The NO ₃ -N meter 54 for measuring nitrate nitrogen (NO ₃ -N) concentration is provided, and the NH ₄ -N concentration, the NO ₂ -N concentration, and the NO ₃ -N concentration of the water to be treated flowing out from the reaction tank 14 are provided. Concentration was measured, and the following (a), (b) and (c) combinations, the following (a) and (c) combinations, the following (b) and (c) combinations, and the following (d) alone It is preferable to adjust the amount of aeration (the amount of air supplied to the diffuser 56) in the reaction tank 14 using any means selected from the group consisting of the following (e) alone.
(A) When the NO ₃ —N concentration exceeds a certain set value, the aeration amount is decreased.
(B) The amount of aeration is reduced when the NO ₂ —N concentration exceeds a certain set value.
(C) When the NH ₄ —N concentration exceeds a certain set value, the aeration amount is increased.
(D) The aeration amount is decreased when the NO ₃ —N concentration becomes a certain set value or more, and the aeration amount is increased when the NO ₃ —N concentration becomes a certain set value or less.
(E) The amount of aeration is decreased when the NO ₂ —N concentration becomes a certain set value or more, and the amount of aeration is increased when the NO ₂ —N concentration becomes a certain set value or less.

In addition, as shown in FIG. 21, the inside of the reaction tank 14 completely distribute | circulates to-be-processed water toward the downstream side from which the to-be-processed water flows out from the upstream side into which to-be-processed water flows in. When partitioned into a plurality of sections 15a, 15b, and 15c by partition walls 30a and 30b that are not shut off, an NH ₄ -N meter 50 that measures NH ₄ -N concentration and a NO ₂ -N concentration are measured in each section. A NO ₂ -N meter 52 that performs measurement, and a NO ₃ -N meter 54 that measures the NO ₃ -N concentration are provided, and the NH ₄ -N concentration, the NO ₂ -N concentration, and the NO ₃ -N concentration of the water to be treated in each compartment. In the partition 15a on the upstream side of any partition wall 30a among the partition walls 30a and 30b that measure the concentration and partition each partition, a combination of the following (a), (b), and (c), the following (a) And a combination of (c) and a combination of (b) and (c) below The aeration amount (the amount of air supplied to the air diffuser 56) is adjusted using any means selected from the group consisting of the following (d) alone and the following (e) alone, and from the above-mentioned arbitrary partition wall 30a In the downstream sections 15b and 15c, a combination of the following (f), (g), and (h), a combination of the following (f) and (h), a combination of the following (g) and (h), It is preferable to adjust the amount of aeration (the amount of air supplied to the diffuser 56) using any means selected from the group consisting of the following (i) alone and the following (j) alone.
(A) When the NO ₃ —N concentration exceeds a certain set value, the aeration amount is decreased.
(B) The amount of aeration is reduced when the NO ₂ —N concentration exceeds a certain set value.
(C) When the NH ₄ —N concentration exceeds a certain set value, the aeration amount is increased.
(D) The aeration amount is decreased when the NO ₃ —N concentration becomes a certain set value or more, and the aeration amount is increased when the NO ₃ —N concentration becomes a certain set value or less.
(E) The amount of aeration is decreased when the NO ₂ —N concentration becomes a certain set value or more, and the amount of aeration is increased when the NO ₂ —N concentration becomes a certain set value or less.
(F) Aeration is stopped when the NO ₃ —N concentration exceeds a certain set value.
(G) Aeration is stopped when the NO ₂ —N concentration exceeds a certain set value.
(H) Aeration is started when the NH ₄ —N concentration exceeds a certain set value.
(I) Aeration is stopped when the NO ₃ —N concentration becomes a certain set value or more, and aeration is started when the NO ₃ —N concentration becomes a certain set value or less.
(J) Aeration is stopped when the NO ₂ —N concentration becomes a certain set value or more, and aeration is started when the NO ₂ —N concentration becomes a certain set value or less.

  By adjusting the amount of aeration by such a method, excessive aeration is suppressed and insufficient aeration is suppressed. As described above, in the case where the inside of the reaction tank 14 is partitioned into a plurality of compartments, in the compartments 15b and 15c on the downstream side of the arbitrary partition wall 30a, the aeration (aeration device) is not an increase / decrease in the amount of aeration. (Air supply to 56) The adjustment (on-off control) by stopping and starting itself is that the consumption of DO by the organic matter in the water to be treated is almost completed in the upstream section 15a, and the downstream section In 15b and 15c, it is not necessary to consider much the consumption of DO due to organic substances, so adjustment by simple on-off control is easier than increase / decrease in the amount of aeration.

  As shown in FIG. 1, a pH meter 34 is installed in the reaction tank 14. Thereby, the pH of the water to be treated in the reaction tank 14 is measured, and an alkali agent, for example, sodium carbonate, for adjusting the pH of the water to be treated is driven in accordance with the pH, and the alkali agent injection pump 36 is driven. Thus, the water to be treated is supplied into the water to be treated in the reaction tank 14 and adjusted so that the water to be treated is alkaline (preferably, pH 7.3 to 8.5) so that an anaerobic ammonia reaction is likely to occur.

As shown in FIG. 1, a mixing tank 16 is connected to the downstream side of the reaction tank 14 via a pipe with a PO ₄ meter 22 attached in the middle, and a motor-driven stirring device is provided in the mixing tank 16. is set up. Thereby, the PO ₄ concentration of the treated water treated with the nitrite type nitrifying bacteria and the anaerobic ammonia oxidizing bacteria in the reaction tank 14 is measured by the PO ₄ meter, and the solid organic matter and the PO ₄ concentration are measured according to the PO ₄ concentration. A flocculant for agglomerating phosphorus, such as polyaluminum chloride (PAC), is supplied into the water to be treated in the mixing tank 16 by driving the flocculant injection pump 24 and is treated by the stirring device. The water is stirred to remove solid organic substances and / or phosphorus in the water to be treated until a predetermined concentration is reached.

A second settling tank 18 is provided downstream of the mixing tank 16 via a pipe, and solid organic substances and / or phosphorus aggregated by the coagulant in the mixing tank 16 is precipitated in the second settling tank 18. I am doing so. The precipitated phosphorus is periodically withdrawn from the bottom of the second settling tank 18 and sent to a sludge treatment facility for disposal. On the other hand, the supernatant liquid in the second sedimentation tank 18 is sent out of the system as treated water after denitrification and phosphorus removal. The PO ₄ meter 22, the flocculant injection pump 24, and the mixing tank 16 may be installed on the upstream side of the first settling tank 12. In this case, a flocculant is added to the water to be treated before being biologically nitrogen-removed in the reaction tank 14, and the flocculant is agglomerated in the first settling tank 12 installed on the upstream side of the reaction tank 14. Solid organic substances and / or phosphorus aggregated by the agent precipitate, and in the second sedimentation tank 18 installed on the downstream side of the reaction tank 14, the solids contained in the treated water that has been denitrified and phosphorus-removed are precipitated. become.

  About the water treatment system 10 which has the above structure, the effect | action is demonstrated in detail below. First, water to be treated is supplied to the first settling tank 12. In the 1st sedimentation tank 12, the foreign material in to-be-processed water precipitates, On the other hand, the supernatant liquid in the 1st sedimentation tank 12 is sent to the reaction tank 14 through piping. In addition, the sludge which settled on the bottom in the 1st sedimentation tank 12 is suitably extracted, sent to a sludge treatment facility, and is disposed.

  Next, the water to be treated is removed in the reaction tank 14 by the biological nitrogen removal method of the present invention. More specifically, the pH of the water to be treated that has flowed into the reaction vessel 14 is measured by a pH meter 34, and an alkali agent such as sodium carbonate is added to the alkali agent injection pump 36 according to the pH. It is supplied to the water to be treated by driving, and the water to be treated is adjusted to be alkaline (preferably, pH 7.3 to 8.5). Thus, by adjusting the water to be treated to be alkaline, an anaerobic ammonia reaction is likely to occur, and as a result, a high soluble nitrogen removal rate can be obtained. The reaction tank 14 has a plurality of partition walls 30 that do not completely block the flow of the treated water from the upstream side where the treated water flows into the downstream side where the treated water flows out. When partitioned into compartments 15a, 15b, 15c, as shown in FIG. 21, a pH meter 34 and an alkaline agent injection pump 36 are installed in each compartment, and the water to be treated is alkaline ( Preferably, the pH is adjusted to be 7.3 to 8.5).

  Further, the water to be treated is agitated by a draft tube aerator 28, and a plurality of carriers 26 having nitrite-type nitrifying bacteria and anaerobic ammonia-oxidizing bacteria supported on the surface portion are indicated by arrows in FIG. The water to be treated flows uniformly, and air is fed into the water to be treated by the draft tube aerator 28. At that time, the concentration of dissolved oxygen in the water to be treated is measured by the DO meter 20, thereby controlling the blower 32 of the draft tube aerator 28 so that a predetermined aerobic condition is created in the water to be treated. Further, based on the soluble nitrogen concentration of the water to be treated that has flowed into the reaction tank 14, the carrier loading rate of the carrier 26 to be poured into the water to be treated is previously adjusted.

  More specifically, the carrier charging rate is defined as the surface area of the carrier 26 per unit volume of the reaction tank 14, and by increasing or decreasing the number of carriers 26 charged into the reaction tank 14, such a carrier charging rate. Can be adjusted. In such a state, first, the water to be treated that has flowed into the reaction vessel 14 is nitrite-type nitrifying bacteria, which is one of the dominant species contained in the microbial film supported on the surface of each carrier 26, Under aerobic conditions, a nitrite-type nitrification reaction occurs and ammonia nitrogen is converted to nitrite nitrogen. At this time, by adjusting the carrier input rate in advance, for example, by reducing the carrier input rate, the thickness of the microbial membrane containing nitrite type nitrifying bacteria as one of the dominant species through nitrite type nitrification reaction Can be increased.

  Thereby, the removal rate of the soluble nitrogen per unit surface area of the carrier 26 is increased, the nitrite type nitrification reaction is further promoted, and nitrous acid is generated. In this case, the generation of nitrous acid occurs at a level that inhibits the nitric acid-type nitrification reaction, so that nitrous acid is generated, but the generated nitrous acid is not converted into nitric acid, and an anaerobic ammonia oxidation reaction It is possible to secure the nitrite nitrogen necessary for the production. As described above, the amount of nitrous acid produced by the nitrite-type nitrification reaction is increased to a level that inhibits the nitrate-type nitrification reaction by adjusting the carrier input rate in the water to be treated. Ammonia nitrogen and nitrite nitrogen necessary for the oxidation reaction are secured. The reaction tank 14 has a plurality of partition walls 30 that do not completely block the flow of the treated water from the upstream side where the treated water flows into the downstream side where the treated water flows out. When the compartments 15a, 15b and 15c are partitioned, the adjustment of the carrier charging rate as described above is performed for each compartment.

  Subsequently, anaerobic ammonia oxidation reaction occurs under pseudo-anaerobic conditions by anaerobic ammonia oxidizing bacteria, which is one of the dominant species contained in the microbial film supported on the surface of each carrier 26, Ammonia nitrogen and nitrite nitrogen are converted to nitrogen. Here, as described above, since the water to be treated is adjusted to be alkaline so that an anaerobic ammonia oxidation reaction easily occurs, a high denitrification effect is obtained by the anaerobic ammonia oxidation reaction.

Next, the water to be treated is sent to the mixing tank 16 through a pipe. At that time, by controlling the flocculant injection pump 24 based on the PO ₄ concentration measured by the PO ₄ meter, the amount of the flocculant supplied into the mixing tank 16 is adjusted, and the water to be treated is stirred. PO ₄ is aggregated by the flocculant. Next, the water to be treated is sent to the second settling tank 18 through a pipe, where the aggregated solid organic matter and / or phosphorus is precipitated, and the precipitated sludge is sent to a sludge treatment facility for disposal. The supernatant liquid that has been subjected to biological nitrogen removal and phosphorus removal treatment in the second sedimentation tank 18 is reused or disposed of separately as treated water. Thus, the water treatment by the water treatment system 10 according to the present invention is completed. In addition, the main water treatment may be performed by continuously injecting water to be treated, or in some cases by batch treatment.

  According to the water treatment system 10 having the above configuration, it is possible to reduce the amount of oxygen necessary to denitrify the water to be treated by performing denitrification using an anaerobic ammonia oxidation reaction. At the same time, no activated sludge is used for denitrification, and a carrier carrying bacteria is used instead of activated sludge, so that no facility for returning activated sludge to the reaction tank is required, and at the same time, When the solid organic matter inevitably mixed is decomposed, oxygen is not consumed, and in general, the amount of oxygen required for water treatment of water to be treated containing soluble nitrogen such as ammoniacal nitrogen is dramatically reduced. Is possible.

In carrying out the biological nitrogen removal method of the present invention, it is preferable to adjust the carrier input rate so that the inflow soluble nitrogen load is 2.5 to 11.5 g / m ² carrier / day. The reaction tank 14 has a plurality of partition walls 30 that do not completely block the flow of the treated water from the upstream side where the treated water flows into the downstream side where the treated water flows out. When the compartments 15a, 15b, and 15c are partitioned, it is preferable to adjust the carrier charging rate so that the inflowing soluble nitrogen load is within the above range in each compartment. FIG. 23 is a graph showing how the dissolved nitrogen removal rate and the NO ₃ —N production concentration change depending on the inflowing soluble nitrogen load, and FIG. 24 shows the case where the inflowing soluble nitrogen load is relatively low. in, NO 3 _-N product concentration is a graph showing how the varying the flows solubility nitrogen load. As shown in these graphs, when the inflowing soluble nitrogen load is in the range of 2.5 to 11.5 g / m ² carrier / day, the dissolving nitrogen removal rate increases almost linearly, and the dissolving nitrogen removal rate ( The slope of the straight line in the graph is maximized. If the inflow soluble nitrogen load is less than 2.5 g / m ² carrier / day, the NO ₃ —N production concentration is high, so it is considered difficult to inhibit the nitric acid-type nitrification reaction, and 11.5 g / m ² carrier Beyond / day, the soluble nitrogen removal rate begins to decline.

As a specific carrier loading rate, it is preferable to adjust to ⁴ to 55 m ² / m ^3, and if adjusted to such a range, the amount of nitrous acid produced by the nitrite type nitrification reaction is adjusted to the nitrate type nitrification reaction. Can be raised to such a level that it can be suppressed, and a high removal rate of soluble nitrogen can be obtained. The reaction tank 14 has a plurality of partition walls 30 that do not completely block the flow of the treated water from the upstream side where the treated water flows into the downstream side where the treated water flows out. When the compartments 15a, 15b and 15c are partitioned, it is preferable to adjust the carrier charging rate within the above-mentioned range. Moreover, it is preferable to implement this invention, stirring a to-be-processed water so that the maximum flow rate of the to-be-processed water in a reaction tank may be 0.7 m / sec or more. As a result of such stirring, the flow rate of the water to be treated with respect to the surface of the carrier increases. As a result, the amount of nitrous acid produced by the nitrite-type nitrification reaction can be increased to a level that inhibits the nitrate-type nitrification reaction, and high dissolution Nitrogen removal rate is obtained.

  In addition, the biological nitrogen removal method of the present invention is preferably performed in a state where the ORP (oxidation-reduction potential) of the water to be treated is −150 mV or less, and more preferably in the state of −300 mV or less. . FIG. 25 is a graph showing how the soluble nitrogen removal rate changes depending on the redox potential of the inflow water in the reaction vessel. As shown in this graph, when the oxidation-reduction potential of the inflow water of the reaction vessel is −150 mV or less, particularly −300 mV or less, a high removal rate of soluble nitrogen is obtained. The rate drops.

  As a method for reducing the ORP when the ORP of the water to be treated is high, a method of injecting a reducing agent into the water to be treated can be mentioned. For example, as shown in FIG. 22, an ORP adjustment tank 57 is provided in the upstream (upstream side) of the reaction tank 14, and the ORP water to be treated flowing into the ORP adjustment tank 57 is measured by an ORP meter 58. The amount of the reducing agent injected into the ORP adjustment tank 57 is adjusted by controlling the reducing agent injection pump 60 so as to have a predetermined value. Thus, the water to be treated whose ORP is adjusted to a predetermined value by the injection of the reducing agent flows into the reaction tank 14 at the subsequent stage (downstream side). As the reducing agent, sludge generated in a water treatment process such as drawn sludge in the first settling tank may be used, or industrially produced chemicals may be used. As the chemical, it is preferable to use a chemical that is not easily oxidized by the organic matter contained in the water to be treated. For example, sodium sulfide can be suitably used.

  Nitrogen removal can be carried out by the biological nitrogen removal method of the present invention, and soluble organic matter and phosphorus can be removed by using activated sludge. Nitrogen removal by the nitrogen removal method is preferably carried out without allowing activated sludge to flow into the reaction tank. If activated sludge flows into the reaction tank, the reaction by the bacteria in the biological nitrogen removal method of the present invention may be inhibited. FIG. 26 is a flowchart in the case where nitrogen removal is performed by the biological nitrogen removal method of the present invention, and soluble organic matter and phosphorus are removed using activated sludge. As described above, the anaerobic tank 62 is installed on the upstream side of the first precipitation tank 12, the aerobic tank 64 is installed between the reaction tank 14 and the second precipitation tank 18, and the reaction tank from the first precipitation tank 12 is used. By providing a bypass path 66 that leads to the aerobic tank 64 without passing through 14 and a return path 68 that returns from the second sedimentation tank 18 to the anaerobic tank 62, the activated sludge can be discharged without flowing the activated sludge into the reaction tank 14. It can be used to remove soluble organic matter and phosphorus.

  Specifically, first, in the anaerobic tank 62, the soluble organic matter in the water to be treated is removed by activated sludge. Thereafter, the water to be treated in the anaerobic tank 62 flows into the first settling tank 12 along with the activated sludge, and the activated sludge and the solid organic matter settle and separate in the first settling tank 12. And the supernatant liquid which does not contain activated sludge and solid organic matter flows into the reaction tank 14, and after nitrogen is removed by the biological nitrogen removal method of the present invention in the reaction tank 14, it enters the aerobic tank 64. Inflow. On the other hand, the activated sludge settled and separated in the first settling tank 12 flows into the aerobic tank 64 through the bypass 66 without flowing into the reaction tank 14. The activated sludge that has flowed into the aerobic tank 64 in this way ingests and accumulates phosphorus contained in the water to be treated after nitrogen removal that has also flowed into the aerobic tank 64. Next, the water to be treated from which phosphorus has been removed by ingesting phosphorus into the activated sludge moves to the second settling tank 18 together with the activated sludge that has accumulated phosphorus, and the activated sludge and other water in the second settling tank 18 Solids separate by settling. The activated sludge and the supernatant liquid not containing solids (treated water from which nitrogen, phosphorus, and soluble organic substances have been removed) are sent out of the system, while the activated sludge separated and separated is a part of it. Is discharged to the outside of the system as excess sludge, and the remainder is returned to the anaerobic tank 62 through the return path 68 while accumulating phosphorus. The activated sludge thus returned to the anaerobic tank 62 releases phosphorus accumulated in the anaerobic tank 62 and removes soluble organic substances in the water to be treated again. In addition, in the process in which activated sludge moves from the aerobic tank 64 to the second sedimentation tank 18, a flocculant may be added to the activated sludge so as to aggregate phosphorus.

  In this way, by operating the activated sludge so that it circulates bypassing the reaction tank 14, the nitrogen removal of the water to be treated flows into the reaction tank 14 by the biological nitrogen removal method of the present invention. It can be said that the removal of soluble organic matter and phosphorus is performed using activated sludge. In addition, when the anaerobic tank 62 exists on the upstream side of the reaction tank 14 as described above, the anaerobic tank 62 functions to lower the ORP of the water to be treated, and thus, without adding a reducing agent as described above, ORP of to-be-processed water can be reduced to a suitable range, and a running cost falls compared with the case where a reducing agent is added.

  The embodiments of the present invention have been described in detail above, but various modifications or changes can be made by those skilled in the art without departing from the scope of the present invention. For example, in this embodiment, the carrier charging rate is adjusted by adjusting the number of carriers charged into the reaction tank. However, the present invention is not limited to this. For example, the surface shape of the carrier is changed. The carrier loading rate may be adjusted by changing the surface area of the carrier. In the present embodiment, the case where the inside of a single reaction vessel is partitioned by a partition has been described. However, the present invention is not limited thereto. For example, the inside of the reaction vessel may be a single space without partitioning by a partition. Good. Moreover, although this embodiment demonstrated the case where each tank of a water treatment system was connected through piping, it is not limited to it, For example, you may employ | adopt an overflow system without using piping. Furthermore, in the present embodiment, the case where a draft tube aerator is employed as the agitation device has been described. However, the present invention is not limited thereto, and other agitation devices may be used as long as the necessary agitation force for the water to be treated is obtained. . Furthermore, in the present embodiment, the case where the carrier is made of polyurethane resin has been described. However, the present invention is not limited thereto, and the amount of nitrite produced by the nitrite-type nitrification reaction of the nitrite-type nitrifying bacterium is nitrate-type nitrification. Even if the nitrite-type nitrifying bacteria grow and the thickness of the microbial membrane increases as the reaction is suppressed, the carrier has water-absorbing characteristics and / or hydrophilic characteristics capable of supporting the microbial membrane, and the carrier is treated water. Other types of resins may be used as long as they have strength characteristics that can withstand the shearing force acting on the carrier by flowing in the substrate.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

[Example 1]
In the water treatment system shown in FIG. 1, six reaction tanks 14 are provided in parallel, and the water to be treated is branched from the first settling tank 12 into the six reaction tanks (reaction tanks No. 1 to 6). The water treatment by the biological nitrogen removal method using the anaerobic ammonia oxidation reaction was continuously performed for 7 days from February 11 to February 18, 2010. The dissolved nitrogen concentration of the water to be treated before flowing into the reaction tank and the dissolved nitrogen concentration of the treated water flowing out of the reaction tank after being treated in each reaction tank were measured.

  Of the six reaction vessels, reaction vessel No. 1 is set so that the pH of the water to be treated in the tank is adjusted to 6.8. 2 was set so that the pH of the water to be treated in the tank was adjusted to 7.0. 3 is set so that the pH of the water to be treated in the tank is adjusted to 7.3. 4 is set so that the pH of the water to be treated in the tank is adjusted to 7.8. 5 is set so that the pH of the water to be treated in the tank is adjusted to 8.5. 6 was set so that the pH of the water to be treated in the tank was adjusted to 8.9.

In addition, as processing conditions common to all reaction tanks, a cylindrical (φ4.0 mm × L4.3 mm) polyurethane resin carrier is used as the carrier, and nitrite-type nitrifying bacteria are dominant species as an anaerobic outside. Two-layer microbial membranes, each presenting in a form surrounded by the nitrite-type nitrifying bacteria, were supported as a dominant species of oxidizing ammonia-oxidizing bacteria. The carrier input rate was 15 m ² total carrier surface area / m ³ tank volume. As the water to be treated, sewage having a water temperature of 15 to 29 ° C. and a DO value of 0.5 mg O ₂ / L was used.

  The measurement results of the soluble nitrogen concentration are as shown in FIG. 7, and the soluble nitrogen concentration of the treated water flowing out from any reaction tank is also the soluble nitrogen concentration of the treated water before treatment flowing into each reaction tank. Although it is lower, the reaction tank No. set so that the pH of the water to be treated in the tank was adjusted to 6.8 (acidic) and 7.0 (neutral), respectively. Compared with the dissolved nitrogen concentration of the treated water flowing out from 1 and 2, the pH of the treated water in the tank was adjusted to 7.3, 7.8, 8.5, and 8.9 (all alkaline), respectively. Reaction tank No. set to Since the dissolved nitrogen concentration of the treated water flowing out from 3 to 6 is lower, it can be seen that the dissolved nitrogen removal rate is improved by making the treated water alkaline. Moreover, reaction tank No. set so that the pH of the to-be-processed water in a tank might be adjusted to 8.5. No. 5 was set so that the dissolved nitrogen concentration of the treated water flowing out of the tank 5 and the pH of the treated water in the tank were adjusted to 8.9. Since the dissolved nitrogen concentration of the treated water flowing out from No. 6 is almost the same, it can be seen that when the pH of the treated water exceeds 8.5, the effect of improving the dissolved nitrogen removal rate reaches its peak.

[Example 2]
In order to confirm the influence of the carrier loading rate on the nitrogen removal rate, a small amount of the carrier used for the continuous treatment in Example 1 was taken out, and the sewage in the actual sewage treatment plant was accommodated as treated water. The sample was placed in a beaker and the following experiment (batch test) was performed. The experimental conditions are as follows.

(Common conditions)
(1) Water to be treated: Precipitated supernatant of sewage treatment plant aeration tank mixture (2) Amount of water: 300 mL (beaker)
(3) DO supply method: aeration and stirring

(Experimental conditions)
(A) In Example 1, the carrier input rate is 15 m ^{2 The} total surface area of the carrier / m ^{3 The} volume of the used carrier is taken out, and the carrier input rate is 90 m ² with respect to 300 mL of water to be treated. The surface area / m ³ tank volume was added, and the mixture was sufficiently stirred (FIG. 8).
(B) In Example 1, the carrier loading rate is 15 m ² Total surface area of the carrier / m ^{3 The} volume of the used carrier is taken out, and the carrier loading rate is 30 m ² with respect to 300 mL of water to be treated. The surface area / m ³ tank volume was added, and the mixture was sufficiently stirred (FIG. 9).
(C) Carrier loading rate in Example 1 15 m ² Carrier total surface area / m ³ Carrier volume is taken out, and the carrier loading rate is 7.5 m ² with respect to 300 mL of water to be treated. The total surface area of the carrier / m ^{3 was} added to the tank volume, and the mixture was sufficiently stirred (FIG. 10).

The experimental results under each experimental condition are shown in FIGS. 8 to 10, [NO _X -N] is the sum of [NO ₃ -N] (nitrate nitrogen concentration) and [NO ₂ -N] (nitrite nitrogen concentration), and ionic nitrogen is The sum of [NH ₄ -N] (ammonia nitrogen concentration) and [NO _x -N], the NH ₄ -N decrease rate (mgN / L / hr) is ([NH ₄ -N] (at 0 hour) + [NH ₄ -N] (after 4 hours) / 4, NH ₄ -N reduction rate (mgN / m ² support surface area / hr) is NH ₄ -N reduction rate / support surface area, ionic nitrogen reduction rate (MgN / L / hr) is (ionic nitrogen (at 0 hours) + ionic nitrogen (after 4 hours)) / 4, ionic nitrogen reduction rate (mgN / m ² carrier surface area / hr) is ion Nitrogen reduction rate / surface area. 8 to 10, the lower the carrier input rate, the lower the ionic nitrogen reduction rate (mgN / L / hr) or (mgN / m ² carrier surface area / hr) and the NH ₄ -N reduction rate (mgN / L / hr) or (mgN / m ² support surface area / hr) increases, while the NO _X -N increase rate (mgN / L / hr) or (mgN / m ² support surface area / hr) decreases I understand. Here, the NH ₄ —N reduction rate can be regarded as a nitrification rate, and the ionic nitrogen reduction rate can be regarded as an anaerobic ammonia oxidation rate.

Therefore, the following knowledge was obtained by the above experiment.
(1) There is a causal relationship between the carrier input rate and the nitrification rate defined as the ammonia nitrogen reduction rate, and the higher the carrier input rate, the lower the nitrification rate.
(2) There is a causal relationship between the carrier input rate and the nitrite type nitrification reaction. The lower the carrier input rate, the more the nitrite type nitrification reaction is promoted. Nitrogen is produced.
(3) There is a causal relationship between the carrier input rate and the anaerobic ammonia oxidation reaction, and the lower the carrier input rate, the more the anaerobic ammonia oxidation reaction is promoted.

  From the above, the present inventors have confirmed that the carrier loading rate can affect the promotion of nitrite type nitrification reaction, inhibition of nitrate type nitrification reaction, and promotion of anaerobic ammonia oxidation reaction.

[Example 3]
In order to confirm the influence of the presence of activated sludge on the anaerobic ammonia oxidation reaction, a small amount of the carrier used for the continuous treatment in Example 1 is taken out, and it is treated with the liquid to be treated and activated with little activated sludge. The following experiments (batch test) were performed by putting them into beakers each containing a liquid to be treated containing a relatively high concentration of sludge. The experimental conditions are as follows.

(Common conditions)
(1) Carrier loading rate: 50 m ² Carrier total surface area / m ³ Water volume (2) Water volume: 300 mL (beaker)
(3) DO supply method: aeration and stirring

(Experimental conditions)
(A) The carrier used in Example 1 was taken out at a rate of 15 m ² total surface area of the carrier / m ³ tank volume, and the carrier was removed from the treated water (active sludge mixed) having an activated sludge concentration of 16 mg SS / L. The solution was added to the liquid precipitation supernatant) and sufficiently stirred (FIG. 11).
(B) Carrier used in Example 1 15 m ² Total surface area of the carrier / m ³ Tank volume is taken out, and the carrier is treated water with activated sludge concentration of 1620 mg SS / L (mixed activated sludge). The mixture was sufficiently stirred (FIG. 12).

The experimental results under each experimental condition are shown in FIG. 11 and FIG. 11 and 12, [NO _X -N] is the sum of [NO ₃ -N] (nitrate nitrogen concentration) and [NO ₂ -N] (nitrite nitrogen concentration), and ionic nitrogen is It is the sum of [NH ₄ —N] (ammonia nitrogen concentration) and [NO _X —N]. When FIG. 11 and FIG. 12 are compared, when the liquid to be treated contains almost no activated sludge, the ionic nitrogen concentration significantly decreases with time, but the liquid to be treated has a relatively high concentration of activated sludge. When it contains, it turns out that the ionic nitrogen concentration has hardly changed. In addition, when the liquid to be treated contains almost no activated sludge, the concentration of ammonia nitrogen decreases with the passage of time, but [NO _X -N] is sufficient to balance the decrease in concentration due to nitrification of ammonia nitrogen. There is no rise. On the other hand, when the liquid to be treated contains activated sludge at a relatively high concentration, the ammonia nitrogen concentration decreases with time, and [NO _X -N] is just enough to balance the decrease in concentration due to nitrification of ammonia nitrogen. The rise is seen.

  According to this experiment, when the liquid to be treated contains almost no activated sludge, the anaerobic ammonia oxidation reaction by the anaerobic ammonia oxidizing bacteria on the carrier proceeds sufficiently, and the removal of soluble nitrogen is performed with high efficiency. However, when the liquid to be treated contains activated sludge at a relatively high concentration, nitrite nitrogen is converted to nitrate nitrogen by activated sludge rather than anaerobic ammonia oxidation reaction by anaerobic ammonia oxidizing bacteria on the carrier. It was preferentially used in the oxidation reaction, and it was found that soluble nitrogen was not removed.

  From the above, in carrying out the biological nitrogen removal method of the present invention, in the liquid to be treated, the carrier and the activated sludge are not allowed to coexist, that is, the activated sludge is not used, and the microbial membrane containing the predetermined bacteria is supported. It was confirmed that nitrogen removal was preferably performed using only the carrier.

  According to the present invention, using the fact that the production of nitrous acid contributes to the inhibition of the nitric acid type nitrification reaction, in order to simultaneously achieve the promotion of the nitrite type nitrification reaction and the suppression of the nitric acid type nitrification reaction, By accelerating the nitrite type nitrification reaction at a level that suppresses the type nitrification reaction, while relaxing the restrictions on the ammonia nitrogen concentration of the water to be treated, the water temperature in the reaction tank, and the DO value, In terms of enabling denitrification at a practical level using an anaerobic ammonia oxidation reaction, a relatively low concentration of ammonia nitrogen such as municipal sewage or domestic wastewater is used as the water to be treated. It can be applied as is to room temperature wastewater, and is industrially useful.

10: water treatment system, 12: first settling tank, 14: reaction vessel, 15a, 15b, 15c: compartment, 16: mixing vessel, 18: second sedimentation tank, 20: DO meter 22: PO ₄ meters, 24 : Flocculant injection pump, 26: carrier, 27: surface portion, 28: draft tube aerator, 30, 30a, 30b: partition wall, 32: blower, 34: pH meter, 36: alkaline agent injection pump, 40: impeller, 42 : Shaft, 44: drive device, 46: air diffuser, 48: draft tube, 50: NH ₄ -N meter, 52: NO ₂ -N meter, 54: NO ₃ -N meter, 56: air diffuser, 57: ORP adjustment tank, 58: ORP meter, 60: reducing agent injection pump, 62: anaerobic tank, 64: aerobic tank, 66: bypass path, 68: return path, 72: nitrite type nitrifying bacteria, 74: anaerobic ammonia Oxidizing bacteria, 76: other bacteria .

Claims (14)

Nitrite-type nitrifying bacteria contributing to nitrite-type nitrification reaction and anaerobic ammonia-oxidation contributing to anaerobic ammonia oxidation reaction in treated water containing dissolved nitrogen flowing into the reaction tank under aerobic conditions Two dominant species with bacteria, or nitrous acid nitrifying bacteria that contribute to nitrite type nitrification reaction, anaerobic bacteria that decomposes soluble nitrogen other than ammonia to ammonia and anaerobic ammonia oxidation reaction Anaerobic ammonia-oxidizing bacteria, anaerobic ammonia oxidation reaction is used to denitrify water to be treated by flowing a carrier carrying a microbial membrane containing three dominant species on the surface. A biological nitrogen removal method using ammonia oxidation reaction,
In a state in which the water to be treated is adjusted to be alkaline in the reaction tank, the amount of nitrous acid produced by the nitrite nitrification reaction of the nitrite nitrifier is such a level that the nitrate nitrification reaction is suppressed. A biological nitrogen removal method using an anaerobic ammonia oxidation reaction in which the carrier input rate (the total surface area of the carrier per unit volume of the reaction tank) is adjusted so that   The biological nitrogen removal method using an anaerobic ammonia oxidation reaction according to claim 1, wherein the pH of the water to be treated is adjusted to 7.3 to 8.5 in the reaction tank. The biology using the anaerobic ammonia oxidation reaction according to claim 1 or 2, wherein the carrier input rate is adjusted so that the inflow soluble nitrogen load is 2.5 to 11.5 g / m ² carrier / day. Nitrogen removal method. The biological nitrogen removal method using the anaerobic ammonia oxidation reaction according to claim 1 or 2, wherein the carrier input rate is adjusted to ⁴ to 55 m ² / m ³ . The ammonia nitrogen (NH ₄ -N) concentration, nitrite nitrogen (NO ₂ -N) concentration, and nitrate nitrogen (NO ₃ -N) concentration of the water to be treated flowing out of the reaction tank were measured, and the following (a ), (B) and (c), the following (a) and (c), the following (b) and (c), the following (d) alone and the following (e) alone. The denitrification from the water to be treated is performed using an anaerobic ammonia oxidation reaction while adjusting the amount of aeration in the reaction tank using any means selected from the group. A biological nitrogen removal method using the anaerobic ammonia oxidation reaction according to claim 1.
(A) When the NO ₃ —N concentration exceeds a certain set value, the aeration amount is decreased.
(B) The amount of aeration is reduced when the NO ₂ —N concentration exceeds a certain set value.
(C) When the NH ₄ —N concentration exceeds a certain set value, the aeration amount is increased.
(D) The aeration amount is decreased when the NO ₃ —N concentration becomes a certain set value or more, and the aeration amount is increased when the NO ₃ —N concentration becomes a certain set value or less.
(E) The amount of aeration is decreased when the NO ₂ —N concentration becomes a certain set value or more, and the amount of aeration is increased when the NO ₂ —N concentration becomes a certain set value or less. Nitrite-type nitrifying bacteria contributing to nitrite-type nitrification reaction and anaerobic ammonia-oxidation contributing to anaerobic ammonia oxidation reaction in treated water containing dissolved nitrogen flowing into the reaction tank under aerobic conditions Two dominant species with bacteria, or nitrous acid nitrifying bacteria that contribute to nitrite type nitrification reaction, anaerobic bacteria that decomposes soluble nitrogen other than ammonia to ammonia and anaerobic ammonia oxidation reaction Anaerobic ammonia-oxidizing bacteria, anaerobic ammonia oxidation reaction is used to denitrify water to be treated by flowing a carrier carrying a microbial membrane containing three dominant species on the surface. A biological nitrogen removal method using ammonia oxidation reaction,
The inside of the reaction tank has a plurality of partition walls that do not completely block the flow of the treated water from the upstream side where the treated water flows into the downstream side where the treated water flows out. Divided into compartments,
In a state where the water to be treated is adjusted to be alkaline in each compartment, the amount of nitrous acid produced by the nitrite-type nitrification reaction of the nitrite-type nitrifying bacteria is such a level as to inhibit the nitrate-type nitrification reaction A biological nitrogen removal method using an anaerobic ammonia oxidation reaction in which the carrier input rate (the total surface area of the carrier per unit volume of the reaction tank) is adjusted so that   The biological nitrogen removal method using anaerobic ammonia oxidation reaction according to claim 6, wherein the pH of the water to be treated is adjusted to 7.3 to 8.5 in each of the compartments. The anaerobic ammonia oxidation according to claim 6 or 7, wherein the carrier charging rate is adjusted so that the inflow soluble nitrogen load is 2.5 to 11.5 g / m ² carrier / day in each of the compartments. Biological nitrogen removal method using reaction. The biological nitrogen removal method using an anaerobic ammonia oxidation reaction according to claim 6 or 7, wherein a carrier input rate is adjusted to ⁴ to 55 m ² / m ³ in each compartment. Ammonia nitrogen (NH ₄ -N) concentration, nitrite nitrogen (NO ₂ -N) concentration and nitrate nitrogen (NO ₃ -N) concentration of water to be treated in each compartment are measured, and between the compartments In the partition upstream of any partition of the partition walls, the following combinations (a), (b) and (c), combinations (a) and (c), and (b) In combination with (c), the aeration amount is adjusted using any means selected from the group consisting of the following (d) alone and the following (e) alone. , Combinations of (f), (g) and (h) below, combinations of (f) and (h) below, combinations of (g) and (h) below, (i) alone and below (j ) Adjust the amount of aeration using any means selected from the group consisting of only Performs denitrification from treated water by utilizing the anaerobic ammonium oxidation, biological nitrogen removal method utilizing anaerobic ammonium oxidation according to any one of claims 6-9.
(A) When the NO ₃ —N concentration exceeds a certain set value, the aeration amount is decreased.
(B) The amount of aeration is reduced when the NO ₂ —N concentration exceeds a certain set value.
(C) When the NH ₄ —N concentration exceeds a certain set value, the aeration amount is increased.
(D) The aeration amount is decreased when the NO ₃ —N concentration becomes a certain set value or more, and the aeration amount is increased when the NO ₃ —N concentration becomes a certain set value or less.
(E) The amount of aeration is decreased when the NO ₂ —N concentration becomes a certain set value or more, and the amount of aeration is increased when the NO ₂ —N concentration becomes a certain set value or less.
(F) Aeration is stopped when the NO ₃ —N concentration exceeds a certain set value.
(G) Aeration is stopped when the NO ₂ —N concentration exceeds a certain set value.
(H) Aeration is started when the NH ₄ —N concentration exceeds a certain set value.
(I) Aeration is stopped when the NO ₃ —N concentration becomes a certain set value or more, and aeration is started when the NO ₃ —N concentration becomes a certain set value or less.
(J) Aeration is stopped when the NO ₂ —N concentration becomes a certain set value or more, and aeration is started when the NO ₂ —N concentration becomes a certain set value or less.   The carrier comprises a nitrite-type nitrifying bacteria that contributes to a nitrite-type nitrification reaction, or an aerobic bacterium that decomposes soluble nitrogen other than ammonia into ammonia and a nitrite-type nitrifying bacteria that contributes to a nitrite-type nitrification reaction Two layers of microbial membranes are present on the outside as the dominant species, and anaerobic ammonia-oxidizing bacteria that contribute to the anaerobic ammonia oxidation reaction are present inside the nitrite-type nitrifying bacteria as the dominant species. The biological nitrogen removal method using the anaerobic ammonia oxidation reaction as described in any one of Claims 1-10 which is made to carry | support to.   The denitrification is performed from the water to be treated using an anaerobic ammonia oxidation reaction in a state where the ORP (redox potential) of the water to be treated is set to -150 mV or less. Biological nitrogen removal method using anaerobic ammonia oxidation reaction.   The biological nitrogen using the anaerobic ammonia oxidation reaction according to any one of claims 1 to 12, wherein denitrification is performed from the treated water using an anaerobic ammonia oxidation reaction without using activated sludge. Removal method.   The biological water using the anaerobic ammonia oxidation reaction according to any one of claims 1 to 13, wherein the water to be treated containing soluble nitrogen is waste water at room temperature and having a soluble nitrogen concentration of 50 mg / L or less. Nitrogen removal method.

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