JP2007190492A - Method and apparatus for treating nitrogen-containing wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain treated water of high purity by further highly removing nitrate or nitrous nitrogen remaining in denitrified treated water due to ANAMMOX microorganisms. <P>SOLUTION: In this treatment method of nitrogen-containing wastewater, the nitrogen-containing wastewater is subjected to denitrification treatment with ANAMMOX microorganisms being autrophic denitrifying microorganisms using ammonia nitrogen as an electron donor and nitrous nitrogen as an electron receptor. Thereafter, nitrate nitrogen produced as a byproduct by ANAMMOX reaction or remaining nitrous nitrogen is subjected to denitrification treatment. This treated water is circulated to a denitrification treatment process due to ANAMMOX microorganisms. The pH of the obtained treated water is adjusted to 8.8-9.4 to enhance denitrification efficiency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for treating nitrogen-containing wastewater, and in particular, an autotrophic denitrifying microorganism using nitrogen in nitrogen-containing wastewater, ammonia nitrogen as an electron donor, and nitrite nitrogen as an electron acceptor. The present invention relates to a method and an apparatus for performing denitrification treatment by the action of an autotrophic denitrification microorganism using hydrogen gas as an electron donor, nitrite nitrogen and / or nitrate nitrogen as an electron acceptor after denitrification treatment by action.

  Ammonia nitrogen contained in wastewater is one of the causative substances of eutrophication in rivers, lakes and oceans, and it is necessary to remove it efficiently in the wastewater treatment process. In general, ammonia nitrogen in wastewater is oxidized by ammonia oxidizing bacteria to nitrite nitrogen, and nitrifying nitrogen is oxidized to nitrate nitrogen by nitrite oxidizing bacteria. Nitrite nitrogen and nitrate nitrogen are denitrified bacteria, which are heterotrophic bacteria, and are converted into nitrogen gas through a two-stage biological reaction with a denitrification process that decomposes organic matter into nitrogen gas using an electron donor. Disassembled.

  However, such a conventional nitrification denitrification method requires a large amount of organic matter such as methanol as an electron donor in the denitrification step, and also requires a large amount of oxygen in the nitrification step, so that the running cost is high. is there.

On the other hand, in recent years, using an autotrophic denitrifying microorganism (autotrophic bacterium) using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, ammonia nitrogen and nitrite nitrogen A method of denitrifying by reacting was proposed. If this method is used, it is not necessary to add an organic substance, so that the cost can be reduced as compared with a method using heterotrophic denitrifying bacteria. Moreover, since the yield of autotrophic microorganisms is low and the amount of sludge generated is significantly less than that of heterotrophic microorganisms, the amount of surplus sludge generated can be suppressed. Furthermore, there is also a feature that the generation of N ₂ O observed by the conventional nitrification denitrification method does not occur and the burden on the environment can be reduced.

  A biodenitrification process using this autotrophic denitrifying microorganism (hereinafter sometimes referred to as “ANAMMOX microorganism”) is described in Strous, M, et al., Appl. Microbiol. Biotechnol., 50, p.589- 596 (1998), it is considered that ammonia nitrogen and about 1.3 times the amount of nitrite nitrogen react and are decomposed into nitrogen gas in the following reaction. This biological denitrification reaction is generally called the ANAMOX reaction.

  However, in the ANAMMOX reaction, most of nitrogen is converted into nitrogen gas, while 0.26 mol of nitrate nitrogen is by-produced with respect to 1 mol of ammonia nitrogen in the raw water. This nitrate nitrogen is considered to be a reaction product during cell synthesis of autotrophic bacteria, but if the nitrogen concentration in the raw water is high due to the byproduct of this nitrate nitrogen, the nitrate in the treated water The nitrogen concentration will exceed the wastewater standard value. Further, when the raw water contains an amount of nitrite nitrogen that is larger than the reaction equivalent to ammonia nitrogen, the nitrite nitrogen remains in the treated water.

  Japanese Patent Application Laid-Open No. 2002-361285 describes a method of denitrifying remaining nitrate nitrogen and nitrite nitrogen by heterotrophic denitrification microorganisms after denitrification treatment by ANAMOX microorganisms. However, denitrification treatment by heterotrophic denitrification microorganisms requires the addition of organic substances such as methanol, ethanol, and acetic acid as hydrogen donors, and combining such treatments does not require the addition of organic substances. The advantage of utilizing the reaction is impaired. In addition, since the heterotrophic denitrification tank is provided in the subsequent stage, there is a disadvantage that the apparatus configuration becomes complicated.

  In addition, for example, Japanese Laid-Open Patent Publication No. 57-201594 has proposed a method of performing denitrification treatment using an autotrophic denitrifying microorganism using hydrogen gas instead of an organic substance as an electron donor. For example, the denitrification treatment can be performed without adding an organic substance. Further, in this method, in order to increase the utilization efficiency of hydrogen gas and reduce the processing cost, hydrogen gas is supplied into the water to be treated through the gas permeable membrane, and adheres to and propagates on the surface of the membrane to be treated. Japanese Patent No. 2901323 proposes a method for performing an efficient denitrification treatment using autotrophic denitrification microorganisms.

  However, this method requires a step of dissolving hydrogen gas, and therefore the processing speed is slow, and since a compressor is used for dissolving hydrogen gas, the electricity cost is high, and a large amount of expensive hydrogen gas is used. The cost is high and the degree of danger is high.

In the past, there was no proposal to combine the ANAMOX reaction with the denitrification treatment by an autotrophic denitrification microorganism using hydrogen gas as an electron donor. Further, in that case, the apparatus configuration was simplified and the denitrification treatment was performed. No consideration has been given to improving efficiency.
JP 2002-361285 A JP-A-57-201594 Japanese Patent No. 2901323 Strous, M, et al., Appl. Microbiol. Biotechnol., 50, p.589-596 (1998)

  The present invention has been made in view of the above-described conventional situation, and further removes nitrate nitrogen and nitrite nitrogen remaining in denitrification treated water by the ANAMMOX microorganism to obtain high-quality treated water. It aims at providing the processing method and processing equipment of nitrogen content drainage.

  Another object of the present invention is to provide a nitrogen-containing wastewater treatment method and a treatment apparatus that remarkably increase the treatment efficiency in the denitrification treatment using the ANAMOX microorganisms.

  The present invention also eliminates the complexity of the device configuration due to the denitrification treatment of the denitrification water by the ANAMOX microorganisms, and the nitrogen-containing wastewater treatment method that performs efficient denitrification treatment with a simple device and operation And it aims at providing a processing device.

  The method for treating nitrogen-containing wastewater of the present invention (Claim 1) is the nitrogen-containing wastewater treatment method for biologically denitrifying wastewater containing nitrogen, wherein ammonia nitrogen is used as an electron donor and nitrite nitrogen is used. A first autotrophic denitrification step for denitrification treatment by the action of an autotrophic denitrifying microorganism as an electron acceptor, and hydrogen gas as an electron donor for the treated water of the first autotrophic denitrification step, A second autotrophic denitrification step for denitrification by the action of an autotrophic denitrifying microorganism using nitrite nitrogen and / or nitrate nitrogen as an electron acceptor; and the second autotrophic denitrification step And a treated water circulation step for returning the treated water to the first autotrophic denitrification step.

  A method for treating nitrogen-containing wastewater according to claim 2 is the method according to claim 1, wherein a part of the treated water in the first autotrophic denitrification step is discharged out of the system as biological denitrification treated water, and the remainder Is fed to the second autotrophic denitrification step.

  The nitrogen-containing wastewater treatment method according to claim 3 is the hydrogen gas supply step according to claim 1 or 2, wherein the second autotrophic denitrification step is a step of bringing the water to be treated and hydrogen gas into contact with each other through a membrane. It is characterized by including.

  The method for treating nitrogen-containing wastewater according to claim 4 is characterized in that, in claim 3, microbial reaction is performed on the treated water side of the membrane by attaching and growing microorganisms on the treated water side surface of the membrane. To do.

  The nitrogen-containing wastewater treatment method according to claim 5 is the method according to any one of claims 1 to 4, wherein the second autotrophic denitrification step is performed in the second autotrophic denitrification step or preceding stage. It has the pH adjustment process of adjusting pH so that pH of treated water may be 8.8-9.4.

  The nitrogen-containing wastewater treatment method according to claim 6 is the method according to any one of claims 1 to 5, wherein the pH of the water introduced into the first autotrophic denitrification step is 6.5 to 8.0. It has the pH adjustment process which adjusts pH so that it may become.

  The nitrogen-containing wastewater treatment method according to claim 7 is the method according to any one of claims 1 to 6, wherein a ratio of nitrite nitrogen to ammonia nitrogen in the nitrogen-containing wastewater is 1.3 mol times or less. It is characterized by.

  The nitrogen-containing wastewater treatment apparatus according to the present invention (invention 8) is a nitrogen-containing wastewater treatment apparatus for biologically denitrifying wastewater containing nitrogen, wherein ammonia nitrogen is used as an electron donor and nitrite nitrogen is used. A first autotrophic denitrification means for denitrification by the action of an autotrophic denitrifying microorganism as an electron acceptor, hydrogen gas as an electron donor, nitrite nitrogen and / or nitrate nitrogen as an electron acceptor A second autotrophic denitrification means for performing a denitrification process by the action of the autotrophic denitrifying microorganism, and treated water of the second autotrophic denitrification means is the first autotrophic denitrification means. And a treated water circulation means for returning to the waste water.

  The nitrogen-containing wastewater treatment apparatus according to claim 9 is the apparatus according to claim 8, wherein a part of the treated water of the first autotrophic denitrification means is discharged out of the system as biological denitrification treated water; And means for feeding the remainder to the second autotrophic denitrification means.

  The nitrogen-containing wastewater treatment apparatus according to claim 10 is the hydrogen gas supply means according to claim 8 or 9, wherein the second autotrophic denitrification means contacts the water to be treated and hydrogen gas through a membrane. It is characterized by including.

  The nitrogen-containing wastewater treatment apparatus according to claim 11 is characterized in that, in claim 10, a microorganism reaction is carried out on the treated water side of the membrane by attaching and growing microorganisms on the treated water side surface of the membrane. To do.

  The apparatus for treating nitrogen-containing wastewater according to claim 12 is the apparatus according to any one of claims 8 to 11, wherein the second autotrophic denitrification means or the preceding stage has the second autotrophic denitrification means. It has a pH adjusting means for adjusting pH so that the pH of the treated water is 8.8 to 9.4.

  The nitrogen-containing wastewater treatment apparatus according to claim 13 is characterized in that in any one of claims 8 to 12, the pH of the water introduced into the first autotrophic denitrification means is 6.5 to 8.0. It has the pH adjustment means which adjusts pH so that it may become.

  The apparatus for treating nitrogen-containing wastewater according to claim 14 is the apparatus according to any one of claims 8 to 13, wherein the ratio of nitrite nitrogen to ammonia nitrogen in the nitrogen-containing wastewater is 1.3 mol times or less. It is characterized by.

  The nitrogen-containing wastewater treatment apparatus according to claim 15 has a circulation tank into which treated water of the first autotrophic denitrification means is introduced according to any one of claims 8 to 14, and the circulation tank The second autotrophic denitrification means is provided inside.

  The apparatus for treating nitrogen-containing wastewater according to claim 16 is the apparatus according to claim 15, wherein the circulation tank introduces raw water introduction part into which the nitrogen-containing wastewater is introduced and treated water from the first autotrophic denitrification means. Treated water introduction part, and a denitrification treatment part for holding the second autotrophic denitrification means provided between the raw water introduction part and the treated water introduction part, and the treated water introduction Water through the denitrification treatment unit to the raw water introduction unit, means for supplying the raw water introduction unit water to the first autotrophic denitrification means, and the treated water And means for discharging the water in the introduction section out of the system as biological denitrification treated water.

  A nitrogen-containing wastewater treatment apparatus according to claim 17 is the treatment apparatus according to claim 16, wherein the treatment apparatus is disposed between the raw water introduction unit and the denitrification treatment unit and between the treated water introduction unit and the denitrification treatment unit. A partition wall having a lower end separated from the bottom surface of the circulation tank is provided, and a partition wall having an upper end submerged below the water surface is provided on the other side.

  According to the present invention, the treated water obtained by the denitrification treatment by the ANAMOX microorganisms (hereinafter sometimes referred to as “ANAMMOX treated water”), hydrogen gas as the electron donor, nitrite nitrogen and / or Denitrifying treatment with autotrophic denitrifying microorganisms (hereinafter sometimes referred to as “hydrogen-oxidizing microorganisms”) using nitrate nitrogen as an electron acceptor, and further treating the treated water (hereinafter referred to as “hydrogen-reducing treated water”) By denitrifying with ANAMMOX microorganisms, high-quality treated water can be obtained by highly removing nitrate nitrogen and by-product nitrite nitrogen that remain as a by-product in the ANAMMOX reaction without adding organic matter. Can be obtained.

  That is, as described above, the denitrification treatment by the ANAMOX microorganism has a drawback that nitrate nitrogen and nitrite nitrogen remain in the ANAMOX treated water.

  Biological denitrification means for nitrate nitrogen include a method in which organic substances such as methanol, ethanol and acetic acid are added as a reducing agent (electron donor) and biologically denitrified by heterotrophic denitrifying microorganisms. This method has the disadvantage that microorganisms that use these organic substances as a carbon source grow and generate excess sludge. In addition, when combined with denitrification treatment by the ANAMMOX reaction, the bacterial flora in the reaction vessel is significantly changed. There is a risk that residual organic matter in the denitrified water becomes an obstacle to the denitrification treatment. On the other hand, in the case of denitrification treatment using hydrogen gas as an electron donor, since hydrogen oxidation microorganisms that use hydrogen gas are the main components, generation of excess sludge and contamination of treated water can be significantly suppressed. Disadvantages include low processing speed, high electricity bill, high cost and high risk due to the large amount of expensive hydrogen gas used.

  In order to solve these problems, in the present invention, a second denitrification treatment by a hydrogen oxidation microorganism is provided as a post-treatment of the first denitrification treatment by the ANAMOX microorganism, and the ANAMOX treated water by the first denitrification treatment is provided. Nitrate nitrogen contained in water is reduced to nitrite nitrogen by the second denitrification treatment, and the nitrite nitrogen produced by the denitrification treatment by the hydrogen-oxidizing microorganism is converted to ammonia in the first denitrification treatment by the ANAMOX microorganism. By performing denitrification treatment by reaction with nitrogen, treated water having an extremely low nitrogen concentration is obtained.

  As described above, the denitrification treatment with heterotrophic denitrification microorganisms has the disadvantage that excessive sludge is generated, and when combined with the denitrification treatment by the ANAMOX reaction, drastically changes the flora in the reaction tank. There is a risk that residual organic matter in the denitrification water will inhibit the denitrification treatment. On the other hand, in the case of denitrification treatment using hydrogen gas as an electron donor, hydrogen oxidation microorganisms that use hydrogen gas are the main components, so excessive sludge generation and contamination of treated water can be greatly suppressed. Since it can be suitably used as a denitrification treatment in a denitrification treatment system by a treatment microorganism, the apparatus configuration can be simplified by being easily incorporated into the ANAMMOX reaction system.

  When the denitrification process using hydrogen-oxidizing microorganisms is performed independently as in the past, the problems of the processing speed, cost, and safety were large as described above. However, in the present invention, the nitrogen concentration is greatly reduced in the first denitrification process. In addition to applying the second denitrification treatment by hydrogen-oxidizing microorganisms to the treated ANAMMOX water, as described later, in this second denitrification treatment, nitrate nitrogen is simply reduced to nitrite nitrogen. For this reason, the hydrogen gas and electric power required for the second denitrification treatment are greatly reduced as compared with the prior art, and the problem of the denitrification treatment by the hydrogen-oxidizing microorganism is greatly improved.

  In the present invention, it is preferable that a part of the ANAMMOX treated water is discharged out of the system as a biological denitrification treated water, and the remaining part is subjected to a second denitrification treatment. Nitrogen is changed to nitrite nitrogen by hydrogen oxidation microorganisms, and nitrite nitrogen in this hydrogen reduction treated water is further removed by ANAMMOX microorganisms, and water with a sufficiently reduced nitrogen concentration can be taken out as treated water (claim) Item 2, 9).

  In the present invention, in the denitrification treatment by the hydrogen-oxidizing microorganism, the ANAMOX treated water and the hydrogen gas are brought into contact with each other through the membrane, and the hydrogen gas is permeated through the membrane to be supplied into the ANAMMOX treated water. Gas can be supplied (claims 3 and 10). At this time, by attaching and growing hydrogen-oxidizing microorganisms on the treated water side of the membrane, efficient denitrification treatment can be performed on the membrane surface on the treated water side (claims 4 and 11).

  Further, the denitrification treatment by the hydrogen-oxidizing microorganism can be performed under such conditions that the pH of the treated water is 8.8 to 9.4, thereby increasing the conversion rate from nitrate nitrogen to nitrite nitrogen. Therefore, it is preferable to adjust the pH of the treated water so that the pH of the treated water is 8.8 to 9.4 in the denitrification treatment step using hydrogen-oxidizing microorganisms or in the preceding stage (claims 5 and 12).

  In other words, the denitrification treatment by hydrogen-oxidizing microorganisms reduces nitrate nitrogen to nitrogen through nitrite nitrogen, but in order to reduce nitrate nitrogen to nitrogen, nitrite nitrogen is changed to nitrogen. In order to reduce, it is necessary to add extra hydrogen, the overall processing efficiency is very poor, and the cost of hydrogen gas is high. On the other hand, if this denitrification treatment is performed under conditions such that the pH of the treated water is 8.8 to 9.4, the denitrification reaction by the hydrogen-oxidizing microorganism can be stopped at the nitrite nitrogen stage. In addition, the processing efficiency is remarkably increased and the amount of hydrogen gas used can be reduced. Thus, the nitrite nitrogen generated by the denitrification treatment by the hydrogen oxidation microorganism can be used for the denitrification treatment of ammonia nitrogen by the ANAMMOX reaction. The denitrification treatment by the hydrogen oxidation microorganism and the denitrification treatment by the ANAMMOX microorganism The effect by combining these can be obtained effectively.

  In the present invention, even when the reduction of nitrate nitrogen by hydrogen-oxidizing microorganisms is stopped with nitrite nitrogen, denitrification of some nitrite nitrogen in the ANAMOX treated water to nitrogen gas is performed. This process can be said to be a denitrification process because denitrification of some nitrate nitrogen to nitrogen gas can also occur.

  Further, in the present invention, the pH-reduced hydrogen reduction treated water is supplied to the ANAMMOX reaction together with the raw water, so that the pH of the water used for the first denitrification treatment is 6.5 to 8.0. It is preferable to adjust the pH so that the ANAMMOX reaction efficiency is improved (claims 6 and 13).

  Thus, in the present invention in which nitrite nitrogen in the hydrogen reduction treated water is subjected to the ANAMOX reaction, the ratio of nitrite nitrogen to ammonia nitrogen in the raw water subjected to the first denitrification treatment is 1.3. It is preferable that the amount of ammonia nitrogen is less than the molar ratio and more than the above-mentioned ANAMMOX reaction equivalent, whereby nitrite nitrogen in the hydrogen reduction treated water can be highly denitrified by the ANAMMOX reaction. , 14).

  It is preferable that the nitrogen-containing wastewater treatment apparatus of the present invention has a circulation tank into which ANAMOX treated water is introduced, and a second autotrophic denitrification means is provided in the circulation tank. ) In particular, this circulation tank is provided with a raw water introduction section into which raw water is introduced, a treated water introduction section into which ANAMOX treated water is introduced, and a second provided between the raw water introduction section and the treated water introduction section. A denitrification treatment unit holding an autotrophic denitrification means, and water can be circulated from the treated water introduction unit through the denitrification treatment unit to the raw water introduction unit. It is preferable to have means for feeding to the autotrophic denitrification means, and means for discharging the water in the treated water introduction part out of the system as biological denitrification treated water (Claim 16). , Between the raw water introduction part and the denitrification treatment part in the circulation tank, and the treated water introduction part It is preferable that a partition wall whose lower end is separated from the bottom surface of the circulation tank is provided on one side with the processing unit, and a partition wall whose upper end is submerged below the water surface is provided on the other side. .

  Such a nitrogen-containing wastewater treatment apparatus can provide a simple and compact apparatus that combines a denitrification process with an ANAMOX microorganism and a denitrification process with a hydrogen oxidation microorganism.

Embodiments of a method for treating nitrogen-containing wastewater and a treatment apparatus according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a system diagram showing an embodiment of a nitrogen-containing wastewater treatment apparatus of the present invention.

  In FIG. 1, a dispersion member 2 for dispersing and introducing water into the tank is provided at the bottom of the ANAMOX reaction tank 1, and a gas-solid-liquid separation member 3 is provided at the top.

  An ANAMOX granule sludge bed is formed in the lower part of the reaction tank 1, and the gas-solid-liquid separation member 3 is arranged above the interface of the sludge bed.

  The gas-solid-liquid separating member 3 includes a cylindrical body 3a whose vertical direction is the cylindrical axis direction, and a taper member 3b disposed below the cylindrical body 3a. The cylindrical body 3a may be any of a cylindrical shape, a rectangular cylindrical shape, an elliptical cylindrical shape, etc., but is preferably a cylindrical shape. The taper member 3b is for preventing the gas rising from below from flowing into the cylindrical body 3a in a short circuit.

  The taper member 3b is formed as a Jinkasa-shaped spindle whose upper surface has a downward slope toward the outer periphery so that sludge to be deposited on the upper surface slides sideways. The taper member 3b has a size that projects outward from the cylindrical body 3a in plan view. A predetermined gap is provided between the lower end of the cylindrical body 3a and the tapered member 3b so that water flows into the cylindrical body 3a. The taper member 3b is connected and supported to the cylindrical body 3a via a rod-like member or the like.

  A pipe 13 for taking out AMAMOX treated water, which will be described later, is extended to the cylinder 3a or inward thereof so as to take out water from the cylinder 3a.

  The gas rising in the reaction tank 1 rises between the outer periphery of the taper member 3b and the inner periphery of the tank 1, and further rises between the cylindrical body 3a and the inner periphery of the tank 1, reaching the water surface. , Leave in the atmosphere.

  Part of the sludge that has risen in the reaction tank 1 hits the taper member 3b and falls. Some sludge enters between the tapered member 3b and the cylindrical body 3a and enters the cylindrical body 3a, but almost no air bubbles flow into the cylindrical body 3a, and the water rises gently. Sludge settles in the cylindrical body 3a, slides down the upper surface of the taper member 3b, and settles down from the outer peripheral edge of the taper member 3b to the reaction tank 1.

  In this way, water from which the gas and sludge have been separated is taken out to the pipe 13.

  The ANAMMO treated water taken out from the ANAMOX reaction tank 1 through the pipe 13 is introduced into the circulation tank 20. The circulation tank 20 has a raw water chamber (raw water) by a partition plate 21 whose lower end is separated from the bottom of the water tank and whose upper end is located above the water surface, and a partition plate 22 which is erected from the bottom of the tank and whose upper end is submerged below the water surface. It is divided into an introduction section 23, a denitrification chamber (denitrification processing section) 24, and a treated water chamber (treated water introduction / discharge section) 25.

  The raw water is introduced from the upper part of the raw water chamber 23 of the circulation tank 22 through the raw water introduction pipe 11 and supplied to the dispersion member 2 from the lower part of the raw water chamber 23 through the pipe 12. The pipe 12 is provided with a pH meter 4A, and the pH of the water in the pipe 12, that is, the water supplied to the ANAMOX reaction tank 1 is measured. Based on the measurement result, the raw water chamber 23 of the circulation tank 20 is measured. An acid / alkali addition means 5 </ b> A for adding acid or alkali from the pipe 16 is provided.

  The ANAMOX treated water from the pipe 13 is introduced into the lower part of the treatment chamber 25 and taken out of the system through the water collecting member 26 and the pipe 14 near the water surface.

  A membrane element 10 is provided in the denitrification chamber 24 of the circulation tank 20, and a pipe 15 for supplying hydrogen gas is connected to the membrane element 10. Further, a pH meter 4B for measuring the pH of the hydrogen reduction treated water flowing into the raw water chamber 23 from the lower part of the partition plate 21 of the circulation tank 20, and a pipe 17 at the upper part of the membrane element 10 based on the measurement result of the pH meter 4B. An acid / alkali addition means 5B for adding more acid or alkali is provided.

  The raw water treatment procedure by the treatment apparatus of FIG. 1 is as follows.

  The raw water (nitrite-type nitrification water containing ammonia nitrogen and nitrite nitrogen) passes through the raw water chamber 23 of the circulation tank 20 and the pipe 12 from the pipe 11, and the dispersion member at the lower part of the ANAMOX reaction tank 1 together with the hydrogen reduction treated water. 2 is fed into the reaction tank 1 and denitrified by the ANAMOX microorganism while ascending in the ANAMMOX reaction tank 1. That is, these are removed by the reaction of ammonia nitrogen and nitrite nitrogen in the raw water to produce nitrate nitrogen. The water to be treated with ANAMMOX introduced into the reaction tank 1 is adjusted to a pH suitable for the later-described ANAMMOX reaction by adding acid or alkali from the acid / alkali addition means 5A as necessary.

  The ANAMMOX treated water flows into the cylinder 3a, is introduced from the pipe 13 into the treated water chamber 25 of the circulation tank 20, rises in the treated water chamber 25, a part is discharged out of the system from the pipe 14, and the remainder is It goes around the upper end of the partition plate 22 and flows into the denitrification chamber 24.

  The ANAMOX treated water that has flowed into the denitrification chamber 24 is adjusted to a pH suitable for the hydrogen reduction treatment described later with acid or alkali from the pipe 17 and supplied from the pipe 15 while flowing down the denitrification chamber 24. In the presence of hydrogen gas, nitrate nitrogen produced as a by-product in the ANAMMOX reaction is reduced to nitrite nitrogen by the hydrogen-oxidizing microorganisms attached and grown on the membrane surface of the membrane element 10. This hydrogen-reduced water flows around the lower end of the partition plate 21 and flows into the raw water chamber 23, and is sent to the ANAMMOX reaction tank 1 through the pipe 12 together with the raw water.

In such a nitrogen-containing wastewater treatment apparatus, the acid / alkali addition means 5B is controlled so that the pH of the hydrogen reduction treated water sent to the raw water chamber 23 is 8.8 to 9.4, as described above. In addition, the reduction by hydrogen oxidation microorganisms can be stopped with nitrite nitrogen and efficient treatment can be performed. If the pH is less than 8.8, nitrate nitrogen is reduced to nitrogen gas, which is not preferable, and if it exceeds 9.4, the hydrogen reduction treatment does not proceed. In addition, since nitrate pH is reduced by reduction by hydrogen-oxidizing microorganisms, the pH of the treated water rises. For this pH adjustment, an acid such as sulfuric acid or hydrochloric acid is used.
Further, when the pH does not rise sufficiently in the hydrogen reduction treatment due to the buffer capacity of the waste water, an alkali such as sodium hydroxide or sodium carbonate is added.

  In addition, the raw water usually has a pH of about 6.5 to 8.0. When such raw water is mixed with hydrogen-reduced water having a pH of 8.8 to 9.4, the pH increases, but this is suitable for the ANAMOX reaction. Since the pH is about 6.5 to 8.0, it is preferable to add acid such as sulfuric acid and hydrochloric acid by controlling the acid addition means 5A so as to reach such pH.

  In the present invention, it is preferable that the entire amount of the hydrogen reduction treated water is subjected to the ANAMOX reaction, and the ratio of the water discharged out of the system and the water subjected to the hydrogen reduction treatment out of the system is out of the system. If there is a large amount of discharged water, the treatment efficiency will improve, but the quality of the treated water will tend to decrease. Conversely, if the proportion of water used for hydrogen reduction treatment is large, the quality of the treated water will improve, but the treatment efficiency will decrease. Therefore, this ratio is appropriately determined in consideration of the required quality of the treated water and the treatment efficiency. In normal cases, 40 to 60% of the ANAMOX treated water is discharged out of the system, and the remainder is reduced with hydrogen. It is preferable to use for.

In addition, FIG. 1 shows an example of an embodiment of a treatment apparatus for nitrogen-containing wastewater of the present invention, and the present invention is not limited to what is shown in the drawings unless it exceeds the gist. As shown in FIG. 1, the present invention can be carried out without providing a new reaction tank by immersing a membrane element for supplying hydrogen gas into an existing treated water tank or an ANAMOX reaction tank, which is preferable.
In this case, it is desirable to provide the membrane element in an area where the biological sludge and the treated water are almost completely separated. Therefore, if there is a treated water tank, the membrane element should be immersed in the treated water tank as shown in FIG. Is preferred.

  In the present invention, the gas permeable membrane of the membrane element immersed in the water tank as the hydrogen gas supply means includes a microfiltration (MF) membrane, an ultrafiltration (UF) membrane, a nanofiltration (NF) membrane, and other Examples of the type include a hollow fiber membrane and a flat membrane. The supply pressure of hydrogen gas is appropriately determined according to the amount of nitrogen to be denitrified for the water to be treated.

In the present invention, wastewater to be treated contains nitrogen, and examples thereof include the following.
(1) Nitrite-type nitrification water in which ammonia nitrogen is partially converted to nitrite nitrogen by nitrite-type nitrification
(2) Water containing ammonia nitrogen and water containing nitrite nitrogen (nitrite-type nitrification water in which almost all nitrite nitrogen contained in water containing ammonia nitrogen is converted to nitrite nitrogen) Mixed water with

  The water containing ammonia nitrogen may contain organic matter and organic nitrogen, but these are preferably decomposed to ammonia nitrogen before denitrification. The raw water may contain an inorganic substance. In general, wastewater containing ammonia nitrogen, organic nitrogen and organic matter such as sewage, human waste, anaerobic digestion and desorption liquid is often treated. In this case, these are treated aerobically or anaerobically. Then, after decomposing organic substances and decomposing organic nitrogen into ammoniacal nitrogen, it is preferable to perform nitrite-type nitrification as necessary and then subject to denitrification treatment according to the present invention.

The ratio of ammonia nitrogen and nitrite nitrogen in the waste water subjected to the denitrification treatment according to the present invention is adjusted so that the amount of ammonia nitrogen is slightly higher than the ANAMMOX reaction equivalent, for example, nitrite to ammonia nitrogen It is preferable that the wastewater has a nitrogen ratio of 1.3 mol times or less, preferably 1.2 to 1.3 mol times, and in such a wastewater, nitrate nitrogen produced by the ANAMOX reaction is converted into a hydrogen-oxidizing microorganism. It is possible to reduce ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen to extremely low concentrations by reducing them to nitrite nitrogen and treating them again with the ANAMOX reaction.
In the present invention, the autotrophic microorganism may be any chemical autotrophic bacterium capable of growing heterotrophically or may be an absolute chemical autotrophic bacterium that cannot use organic matter.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
Using the apparatus shown in FIG. 1, microbial treatment was performed using the following water quality nitrite type nitrification water as raw water.
(Raw water quality)
NH ₄ -N: 250 mg / L
NO ₂ -N: 310mg / L
NO ₃ -N: 0 mg / L
pH: 7.0

The volume of the ANAMOX reaction tank 1 is 25 L, the volume of the circulation tank 20 is 5 L, and a hydrophilic hollow fiber membrane element (“8258A” manufactured by Kuraray Co., Ltd., membrane surface area 12 m ² ) 10 is immersed in the circulation tank 20. Hydrogen gas was supplied at a supply pressure of 0.10 MPa.

The flow rate of the raw water was set to 7.3 L / hr, and the circulating water volume between the ANAMOX reaction tank 1 and the circulation tank 20 was set to 7.3 L / hr. Moreover, the acid for pH adjustment was added to the circulation tank 20 so that the measured pH value of pH meter 4A, 4B might become a value shown in Table 1.
The quality of treated water in each part was examined, and the results are shown in Table 1.

Comparative Example 1
In Example 1, the raw water NO ₂ —N was set to 330 mg / L and hydrogen gas was not supplied to the membrane element. The treatment was performed in the same manner, the quality of the treated water in each part was examined, and the results are shown in Table 1. It was.

Comparative Example 2
In Example 1, the raw water NO ₂ —N is set to 330 mg / L, and an acid for pH adjustment is added to the circulation tank 20 so that the measured pH values of the pH meters 4A and 4B are the values shown in Table 1. Otherwise, the treatment was performed in the same manner, and the quality of the treated water in each part was examined. The results are shown in Table 1.

Comparative Example 3
In Example 1, the treatment was performed in the same manner except that an acid for pH adjustment was added to the circulation tank 20 so that the measured pH values of the pH meters 4A and 4B would be the values shown in Table 1, and the treated water of each part was treated. The water quality was examined and the results are shown in Table 1.

  As is clear from Table 1, nitrate nitrogen produced as a by-product in the ANAMMOX reaction and residual nitrite nitrogen can be obtained by combining denitrification treatment with ANAMMOX microorganisms and denitrification treatment with hydrogen oxidation microorganisms and circulating the treated water. It can be seen that high-quality treated water can be obtained by removing the water at a high level.

In Comparative Example 1, since the hydrogen reduction treatment is not performed, there is a problem that a large amount of nitrate nitrogen is contained in the treated water. In Comparative Example 2 where the pH of the hydrogen reduction treated water was 8.0, nitrate nitrogen was reduced to nitrogen gas by the hydrogen reduction treatment (as a result, the NO ₂ -N of the hydrogen reduction treated water was very high). The quality of treated water is good, but there is a problem that the amount of hydrogen gas used is large. In Comparative Example 3 in which the pH of the hydrogen-reduced treated water is 9.6, there is a problem in that the reduction of nitrate nitrogen in the hydrogen-reducing treatment is insufficient, and good treated water quality cannot be obtained.

In Example 1, the concentration of raw water NO ₂ -N was lower than that of Comparative Examples 1 and 2 because NO ₃ -N produced by the ANAMOX reaction was converted to NO ₂ -N by hydrogen reduction treatment. _{Since 2-} N is subjected to the ANAMOX reaction together with the raw water, the concentration of the raw water NO ₂ -N is adjusted in consideration of this amount.

It is a systematic diagram which shows embodiment of the processing apparatus of the nitrogen-containing waste_water | drain of this invention.

Explanation of symbols

1 ANAMOX reaction tank 10 Membrane element 20 Circulation tank

Claims (17)

In the method of treating nitrogen-containing wastewater, which biologically denitrifies wastewater containing nitrogen,
A first autotrophic denitrification step of denitrifying by the action of an autotrophic denitrifying microorganism using ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor;
The treated water of the first autotrophic denitrification step is denitrified by the action of an autotrophic denitrifying microorganism using hydrogen gas as an electron donor and nitrite nitrogen and / or nitrate nitrogen as an electron acceptor. A second autotrophic denitrification step;
A method for treating nitrogen-containing wastewater, comprising: a treated water circulation step for returning treated water of the second autotrophic denitrification step to the first autotrophic denitrification step.   In Claim 1, while discharging a part of treated water of said 1st autotrophic denitrification process out of the system as biological denitrification process water, the remainder is said 2nd autotrophic denitrification process. A method for treating nitrogen-containing wastewater, characterized by being fed.   3. The treatment of nitrogen-containing wastewater according to claim 1, wherein the second autotrophic denitrification step includes a hydrogen gas supply step in which water to be treated and hydrogen gas are brought into contact with each other through a membrane. Method.   4. The method for treating nitrogen-containing wastewater according to claim 3, wherein a microorganism reaction is carried out on the treated water side of the membrane by causing microorganisms to adhere to and propagate on the treated water side surface of the membrane.   The pH of the treated water in the second autotrophic denitrification step or the preceding stage thereof in any one of claims 1 to 4 is 8.8 to 9.4. A method for treating nitrogen-containing wastewater, comprising a pH adjustment step of adjusting pH so as to become.   6. The method according to claim 1, further comprising a pH adjustment step of adjusting the pH of water introduced into the first autotrophic denitrification step to be 6.5 to 8.0. A method for treating nitrogen-containing wastewater.   The method for treating nitrogen-containing wastewater according to any one of claims 1 to 6, wherein a ratio of nitrite nitrogen to ammonia nitrogen in the nitrogen-containing wastewater is 1.3 mol times or less. In a nitrogen-containing wastewater treatment apparatus for biologically denitrifying wastewater containing nitrogen,
A first autotrophic denitrification means for denitrification by the action of an autotrophic denitrifying microorganism using ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor;
A second autotrophic denitrification means for performing denitrification treatment by the action of an autotrophic denitrifying microorganism using hydrogen gas as an electron donor, nitrite nitrogen and / or nitrate nitrogen as an electron acceptor,
A treatment apparatus for treating nitrogen-containing wastewater, comprising treated water circulation means for returning treated water of the second autotrophic denitrification means to the first autotrophic denitrification means.   The means for discharging a part of the treated water of the first autotrophic denitrification means as biological denitrification treated water as the biological denitrification treated water according to claim 8, and the rest as the second autotrophic denitrification means And a nitrogen-containing wastewater treatment apparatus.   10. The treatment of nitrogen-containing wastewater according to claim 8, wherein the second autotrophic denitrification means includes hydrogen gas supply means for bringing the water to be treated and hydrogen gas into contact with each other through a membrane. apparatus.   11. The apparatus for treating nitrogen-containing wastewater according to claim 10, wherein microorganisms are reacted on the treated water side of the membrane by attaching and growing microorganisms on the treated water side surface of the membrane.   The pH of the treated water of the second autotrophic denitrification means or the preceding stage thereof according to any one of claims 8 to 11 is 8.8 to 9.4. A treatment apparatus for nitrogen-containing wastewater, characterized by comprising pH adjusting means for adjusting pH so as to become.   13. The method according to claim 8, further comprising pH adjusting means for adjusting pH so that the pH of water introduced into the first autotrophic denitrification means is 6.5 to 8.0. An apparatus for treating nitrogen-containing wastewater.   The processing apparatus for nitrogen-containing wastewater according to any one of claims 8 to 13, wherein a ratio of nitrite nitrogen to ammonia nitrogen in the nitrogen-containing wastewater is 1.3 mol times or less.   15. The method according to claim 8, further comprising a circulation tank into which treated water of the first autotrophic denitrification means is introduced, wherein the second autotrophic denitrification means is provided in the circulation tank. An apparatus for treating wastewater containing nitrogen, wherein: In Claim 15, the circulation tank, raw water introduction part into which the nitrogen-containing wastewater is introduced,
A treated water introduction part into which treated water of the first autotrophic denitrification means is introduced;
A denitrification treatment unit holding the second autotrophic denitrification means provided between the raw water introduction unit and the treated water introduction unit,
Water can be circulated from the treated water introduction part to the raw water introduction part via the denitrification treatment part,
Means for feeding the raw water introduction section water to the first autotrophic denitrification means;
A treatment apparatus for nitrogen-containing wastewater, characterized by comprising means for discharging water from the treated water introduction section as biological denitrification treated water to the outside of the system.   In Claim 16, the partition wall in which the lower end was separated from the bottom of the circulation tank between the raw water introduction part and the denitrification treatment part and between the treatment water introduction part and the denitrification treatment part. An apparatus for treating nitrogen-containing wastewater, wherein a partition wall having an upper end submerged below the water surface is provided on the other side.

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