JP2016055230A - Wastewater treatment apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wastewater treatment apparatus and a method that can improve the quality of treated water by reducing the concentration of nitrogen components remaining after anaerobic ammonia oxidation reaction in the biological treatment of wastewater using anaerobic ammonia oxidation reaction.SOLUTION: A wastewater treatment apparatus includes: a nitrite-type nitrification reaction tank 10 in which a part of ammonia nitrogen contained in wastewater is converted into nitrite nitrogen by nitrite-type nitrification reaction; an anaerobic ammonia oxidation reaction tank 20 in which the rest of the ammonia nitrogen and the nitrite nitrogen are converted into molecular nitrogen and nitrate nitrogen by anaerobic ammonia oxidation reaction; and an autotrophic denitrification reaction tank 30 in which the nitrite nitrogen remaining after the anaerobic ammonia oxidation reaction and the nitrate nitrogen are converted into molecular nitrogen by autotrophic denitrification reaction to perform nitrogen removal treatment.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wastewater treatment apparatus and a wastewater treatment method. Specifically, the present invention relates to a wastewater treatment apparatus and a wastewater treatment method for biologically removing nitrogen from wastewater containing nitrogen using an anaerobic ammonia oxidation reaction.

  Nitrogen-containing wastewater containing various inorganic nitrogen and organic nitrogen causes eutrophication of closed water areas and contributes to water pollution. Therefore, biological treatment is performed to convert nitrogen components such as ammonia contained in sewage and various industrial effluents and other nitrogen-containing effluents into nitrogen gas (molecular nitrogen) and remove them by the action of microorganisms. It has been broken.

  As a method for biologically treating nitrogen-containing wastewater, a nitrification / denitrification treatment combining a nitrification reaction and a denitrification reaction has been the mainstream. Nitrification denitrification treatment is an anaerobic nitrification reaction that oxidizes ammonia nitrogen and nitrite nitrogen contained in nitrogen-containing wastewater to nitrate nitrogen and performs anaerobic denitrification reaction. Is a wastewater treatment method in which nitrogen removal treatment is performed by reducing nitrate nitrogen to molecular nitrogen.

  In general, the denitrification reaction in the nitrification denitrification treatment is performed using heterotrophic denitrification bacteria. Therefore, in the denitrification reaction treatment, it may be necessary to add an organic substance such as methanol as a carbon source. In the nitrification reaction, sufficient aeration must be performed to completely oxidize ammonia nitrogen or nitrite nitrogen to nitrate nitrogen. For these reasons, the conventional nitrification / denitrification treatment requires a large amount of chemical cost and power cost, and is a wastewater treatment method with high operation cost.

In recent years, instead of such a combination of a nitrification reaction and a denitrification reaction, development of a wastewater treatment method using an anaerobic ammonia oxidation (ANAMMOX) reaction has been promoted. The anaerobic ammonia oxidation reaction is a method of co-denitrifying ammonia nitrogen and nitrite nitrogen as shown in the following formula 1, using ammonium ions as electron donors and nitrite ions as electron acceptors.
NH ₄ ⁺ +1.32 NO ₂ ⁻ + 0.066HCO ₃ ⁻ + 0.13H ⁺
→ 1.02N ₂ + 0.26NO ₃ ⁻ + 0.066CH ₂ O _0.5 N _0.15 + 2.03H ₂ O (Formula 1)

  In the wastewater treatment method using anaerobic ammonia oxidation reaction, the anaerobic ammonia-oxidizing bacteria group responsible for nitrogen removal is responsible for the nitrogen removal treatment, so unlike conventional nitrification denitrification treatment, organic substances are used as carbon sources. There is an advantage that it is not necessary to add. Moreover, since it is not necessary to nitrite-nitrogen-oxidize nitrite nitrogen to nitrate nitrogen, it also has the advantage that the power cost related to aeration of waste water can be reduced. In addition, the anaerobic ammonia-oxidizing bacteria group is advantageous in that the reaction tank can be miniaturized because it exhibits a high denitrification rate and a small amount of sludge. Therefore, a wastewater treatment method using an anaerobic ammonia oxidation reaction is expected as a technique that specializes in removing nitrogen components and realizes a wastewater treatment with higher exclusiveness than the conventional nitrification denitrification treatment.

  In the anaerobic ammonia oxidation reaction, as shown in the above formula 1, ammonium ions and nitrite ions, which are reaction substrates, react at a ratio of about 1: 1.32. Usually, most of the nitrogen components in the nitrogen-containing wastewater to be treated exist as ammonia nitrogen, and the ratio of nitrite nitrogen is low, so in biological treatment using anaerobic ammonia oxidation reaction, In general, a nitrite type nitrification reaction treatment is performed in which a part of ammonia nitrogen is partially oxidized (nitrite type nitrification) to nitrite nitrogen in advance.

  The nitrifying bacteria responsible for the nitrite-type nitrification reaction are ammonia oxidizing bacteria (AOB) that oxidizes ammonia nitrogen to nitrite nitrogen and nitrite that oxidizes nitrite nitrogen to nitrate nitrogen. It is a hybrid with oxidizing bacteria (NOB), and under normal processing conditions, the reaction may proceed to complete oxidation that produces nitrate nitrogen. Therefore, in the nitrite-type nitrification treatment, in order to adjust the ammonium ion and nitrite ions in the wastewater to an appropriate ratio, the dissolved oxygen concentration, water temperature, pH, nitrogen component concentration, etc. in the wastewater are appropriately managed. The driving | operation which suppresses the activity of nitrate oxidation bacteria is performed.

  As a wastewater treatment method using anaerobic ammonia oxidation reaction, in addition to a method of performing nitrite-type nitrification reaction treatment and anaerobic ammonia oxidation reaction treatment in separate reaction tanks, one-stage reaction tank Development of methods to do this is also underway. For example, Patent Document 1 discloses a first step of generating a solution having an oxidation product of ammonia by nitrifying wastewater containing ammonia by adding oxygen using a nitrifying microorganism, and an oxidation product together with ammonia. A second step of converting to nitrogen via a denitrifying microorganism, and using a waste water containing bicarbonate from which air for supplying bicarbonate is substantially removed, aeration is controlled in the first step Thus, the pH value is maintained at 7.2 or less, a part of ammonia present in the waste water is converted into nitrite to produce a solution containing nitrite, and the produced nitrite is denitrified in the second step. Discloses a method for treating wastewater containing ammonia, characterized in that it is used as an oxidant of the remaining ammonia. Then, the first and second steps are simultaneously performed in a single bioreactor, the nitrifying microorganisms and the denitrifying microorganisms are present in the solid phase in the bioreactor, and the nitrifying microorganisms are substantially aerobic outside the solid phase. The denitrifying microorganisms are present in the anaerobic part substantially inside the solid phase and oxygen is supplied in an amount corresponding to the ammonia concentration in the bioreactor to limit the first step. Yes.

  Further, Non-Patent Document 1 discloses a CANON (Completely Autotrophic Nitrogen Removal Over Nitrite) method in which wastewater treatment is performed in a single tank type reaction tank using an anaerobic ammonia oxidation reaction, which is accompanied by a change in ammonium ion concentration. It is described that the variation of each bacterial group was analyzed.

Special table 2001-506535 gazette

KA Third, O. Sliekers, JG Kuenen, MSM Jetten, The CANON System (Completely Autotrophic Nitrogen-removal Over Nitrite) under Ammonium Limitation: Interaction and Competition between Three Groups of Bacteria, Syst.Appl.Microbiol., 24 (4), p588-596 (2001)

  In biological treatment using an anaerobic ammonia oxidation reaction, as shown in the above formula 1, nitrate ions are theoretically generated at a rate of about 11% in terms of nitrogen without being subjected to nitrogen removal treatment. Inevitably remains in the treated water. Therefore, when the nitrogen component concentration of the wastewater to be treated is high, the amount of nitrate ions remaining in the treated water cannot be ignored, and there is a problem that it is difficult to ensure the required treated water quality.

  Also, the nitrifying bacteria used for nitrite type nitrification treatment and the anaerobic ammonia oxidizing bacteria responsible for the anaerobic ammonia oxidation reaction have a very slow growth rate, ensuring retention time, and outflow of cells outside the reaction tank. Since there is a high demand for prevention of microorganisms, a form of microbial immobilization is often used. Therefore, the contact between each reaction substrate and each bacterial group tends to be poor due to the form of the immobilization carrier, the structure of the fixed bed, and the like. If the reaction rate decreases due to poor contact, the nitrite type nitrification reaction does not produce enough nitrite ions as a reaction substrate for the anaerobic ammonia oxidation reaction, and some ammonium ions are nitrite ions. In the anaerobic ammonia oxidation reaction, the entire amount of the reaction substrate cannot be sufficiently reacted, and ammonium ions and nitrite ions remain in the treated water as they are. The quality of treated water will deteriorate.

  Thus, in biological treatment using an anaerobic ammonia oxidation reaction, there is a practical limit to the removal of nitrogen components, and it is difficult to obtain a good quality of treated water above a certain level. In particular, in the case of applying SBR (sequencing batch reactor) treatment or continuous treatment of wastewater, the influence of a decrease in reaction rate due to poor contact becomes more prominent, and is described in Patent Document 1 and Non-Patent Document 1. In such a process using a single tank type reaction tank, it is assumed that the reaction rate of the substrate decreases during the process, so that an unreacted nitrogen component tends to remain and the quality of the treated water is reduced. There is a risk that it will be more difficult to secure.

  Therefore, the present invention provides a wastewater treatment apparatus capable of reducing the concentration of nitrogen components remaining after anaerobic ammonia oxidation reaction and improving the quality of treated water in biological treatment of wastewater utilizing anaerobic ammonia oxidation reaction. An object is to provide a wastewater treatment method.

  In order to solve the above problems, a wastewater treatment apparatus according to the present invention is a wastewater treatment apparatus for biologically removing nitrogen from wastewater containing ammonia nitrogen using an anaerobic ammonia oxidation reaction. Part of the ammonia nitrogen contained in the nitrite is converted to nitrite nitrogen by a nitrite-type nitrification reaction, and the remainder of the ammonia nitrogen and the nitrite nitrogen are converted to molecular nitrogen by an anaerobic ammonia oxidation reaction. Converting to nitrate nitrogen, converting the nitrite nitrogen remaining after the anaerobic ammonia oxidation reaction and the nitrate nitrogen to molecular nitrogen by an autotrophic denitrification reaction and removing nitrogen It is characterized by.

  Further, the wastewater treatment method according to the present invention is a wastewater treatment method for biologically nitrogen removal treatment of wastewater containing ammonia nitrogen using an anaerobic ammonia oxidation reaction, wherein the ammonia state contained in the wastewater A nitrite-type nitrification reaction step for converting a part of nitrogen into nitrite-type nitrogen by nitrite-type nitrification reaction, the rest of the ammonia nitrogen and the nitrite-type nitrogen are converted into molecular nitrogen by anaerobic ammonia oxidation reaction And anaerobic ammonia oxidation process to convert to nitrate nitrogen, nitrite nitrogen remaining after anaerobic ammonia oxidation reaction and nitrate nitrogen are converted to molecular nitrogen by autotrophic denitrification reaction It includes an autotrophic denitrification reaction step.

  According to the present invention, in biological wastewater treatment of nitrogen-containing wastewater using anaerobic ammonia oxidation reaction, wastewater that can reduce the concentration of nitrogen components remaining after anaerobic ammonia oxidation reaction and improve the quality of treated water A treatment apparatus and a waste water treatment method can be provided. In particular, it is possible to provide a wastewater treatment apparatus and a wastewater treatment method capable of improving the quality of treated water without adding an organic substance as a carbon source and having a lower operating cost.

It is a figure which shows schematic structure of the waste water treatment equipment which concerns on 1st Embodiment of this invention. It is a figure which shows schematic structure of the waste water treatment equipment which concerns on 2nd Embodiment of this invention. It is a figure which shows schematic structure of the waste water treatment equipment which concerns on 3rd Embodiment of this invention. It is a figure which shows the nitrogen concentration of the waste_water | drain processed by the waste water treatment method which concerns on Example 1 of this invention. It is a figure which shows the nitrogen concentration of the waste_water | drain processed by the waste water treatment method which concerns on Example 2 of this invention.

[First Embodiment]
First, the waste water treatment apparatus and waste water treatment method according to the first embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the common part in each figure, and description about the overlapping part is abbreviate | omitted.

  FIG. 1 is a diagram showing a schematic configuration of a wastewater treatment apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, the waste water treatment apparatus 1 according to the first embodiment includes a nitrite type nitrification reaction tank 10, an anaerobic ammonia oxidation reaction tank 20, and an autotrophic denitrification reaction tank 30 in this order. With a typical arrangement. The wastewater treatment apparatus 1 according to the first embodiment is a wastewater treatment apparatus that biologically removes nitrogen-containing wastewater (drainage) containing ammonia nitrogen using an anaerobic ammonia oxidation reaction. The wastewater treatment apparatus 1 is characterized in that treated water that has been subjected to nitrogen removal treatment by an anaerobic ammonia oxidation reaction is further subjected to nitrogen removal treatment by being subjected to an autotrophic denitrification reaction. Have. In the present specification, the autotrophic denitrification reaction means a denitrification reaction performed by autotrophic bacteria under the condition that no organic substance as a carbon source exists.

  In the wastewater treatment apparatus 1, wastewater as treated water is sequentially introduced into each reaction tank of the nitrite type nitrification reaction tank 10, the anaerobic ammonia oxidation reaction tank 20, and the autotrophic denitrification reaction tank 30, and each reaction Biological treatment with microorganisms is performed under reaction conditions controlled for each tank. That is, the wastewater treatment apparatus 1 is a wastewater treatment method (first embodiment) for sequentially performing each step of a nitrite type nitrification reaction step, an anaerobic ammonia oxidation step, and an autotrophic denitrification reaction step in each separate reaction tank. The wastewater treatment method according to (2) is an apparatus that is suitably performed. Each of these reaction tanks may be either a tank type or a tank type, and any operation method of an SBR treatment type reaction tank and a continuous treatment type reaction tank may be employed.

  The nitrogen-containing wastewater (drainage) to be treated in the wastewater treatment apparatus 1 is first introduced into the nitrite type nitrification reaction tank 10. The wastewater to be treated can be introduced into the nitrite type nitrification reaction tank 10 from a drainage tank or the like temporarily storing wastewater by a drainage pump 8 with an appropriate amount of water according to the nitrogen load. The wastewater to be treated may contain nitrite nitrogen or nitrate nitrogen in addition to ammonia nitrogen, but wastewater having a low BOD or C / N ratio (carbon mass / nitrogen mass ratio) is biological. It is preferable in that the treatment can be stabilized and a high nitrogen removal rate can be realized. Specifically, as such wastewater, for example, activated sludge dewatered filtrate obtained by dehydrating activated sludge treated water generated in sewage treatment facilities, livestock wastewater treatment facilities, food wastewater treatment facilities, semiconductor factories, chemical factories, plating, etc. Business wastewater with high nitrogen concentration generated in factories and paint factories can be mentioned.

The nitrite type nitrification reaction tank 10 is subjected to a nitrite type nitrification reaction process (nitrite type nitrification reaction step) in which a part of ammonia nitrogen contained in the waste water is converted into nitrite nitrogen by a nitrite type nitrification reaction. It is a reaction tank. In this nitrite-type nitrification reaction treatment, wastewater provided for anaerobic ammonia oxidation reaction treatment is obtained by partially oxidizing part of ammonium ions contained in the wastewater to nitrite ions in advance by nitrite-type nitrification reaction. The ratio of ammonium ions to nitrite ions is set to a ratio of reaction substrate suitable for anaerobic ammonia oxidation reaction treatment. The nitrite type nitrification reaction is expressed as the following formula 2.
NH ₄ ⁺ + 1.5O ₂ → NO ₂ ⁻ + 2H ⁺ + H ₂ O (Formula 2)

  The nitrite type nitrification reaction tank 10 holds a group of nitrifying bacteria responsible for the nitrite type nitrification reaction. In FIG. 1, the nitrifying bacteria group is immobilized on the floating immobilization carrier 110 and held in the form of a fluidized bed. However, the nitrifying bacteria group may be in either an immobilized form or an unfixed form. It is. Further, the immobilization may be performed by either entrapping immobilization or adhesion immobilization, and may be in any form of fluidized bed or fixed bed. However, since the growth rate of the nitrifying bacteria group is slow, the immobilized form is preferable from the viewpoint of securing the residence time and preventing the bacterial cell from flowing out of the reaction tank. The immobilization carrier can have an appropriate shape such as a spherical shape, a cylindrical shape, a cubic shape, and a rectangular parallelepiped shape, and may be non-porous or porous such as a sponge shape. The fixed bed may be either a stationary filter medium or a rocking filter medium.

  As shown in FIG. 1, the nitrite-type nitrification reaction tank 10 is provided with an air diffuser 12 that diffuses air into drainage and a blower 13 that supplies air to the diffuser 12. The blower 13 feeds air to the diffuser tube 12, and the diffuser tube 12 diffuses air into the waste water, whereby the waste water of the nitrite type nitrification reaction tank 10 is aerated and the dissolved oxygen concentration is increased. ing. By controlling the concentration of dissolved oxygen in the waste water within a predetermined concentration range that is a microaerobic condition, it is possible to perform a nitrite-type nitrification reaction that is limited to partial oxidation from ammonia nitrogen to nitrite nitrogen.

  In addition, as shown in FIG. 1, the nitrite type nitrification reaction tank 10 has a chemical injection tank 15 for storing a pH adjusting agent, and a chemical injection for supplying the pH adjusting agent stored in the chemical injection tank 15 to drainage. A pump 16 can be installed. As the pH adjuster, an alkali hydroxide such as sodium hydroxide, an alkali carbonate such as sodium carbonate, or an alkali bicarbonate such as sodium bicarbonate is used. A preferred pH adjuster is an alkali carbonate or an alkali bicarbonate. By supplying such alkali to the wastewater, the alkalinity consumed by the nitrite-type nitrification reaction can be recovered, and the pH of the wastewater is a neutral to weak alkali region suitable for the nitrite-type nitrification reaction. Can be maintained.

  In the nitrite type nitrification treatment, the pH of the waste water is maintained in a region near weak alkali, and the waste water is treated under a microaerobic condition. Usually, the nitrifying bacteria used in the nitrite type nitrification reactor 10 are ammonia oxidizing bacteria that oxidize ammonia nitrogen to nitrite nitrogen, and nitrite oxidizing bacteria that oxidize nitrite nitrogen to nitrate nitrogen. It takes the form of anaerobic sludge. Therefore, in the nitrite-type nitrification reaction treatment, in order to set the ratio of ammonium ions and nitrite ions in the wastewater to a predetermined ratio, the nitrite nitrogen produced by partial oxidation of ammonia nitrogen is reduced to nitrate nitrogen. What is necessary is just to perform control which suppresses the activity of nitrite oxidation bacteria according to the nitrogen component density | concentration and water temperature of waste water so that it may not be completely oxidized. Specifically, the pH of the wastewater is adjusted to be at least pH 6 or more and pH 9 or less, preferably pH 7 or more and pH 8.2 or less, and the dissolved oxygen concentration in the waste water depends on the form of microorganism immobilization, but preferably It is limited to a microaerobic condition of about 5.0 mg / L or less, more preferably about 4.0 mg / L or less.

  The nitrite type nitrification treatment is usually performed with a residence time such that the ratio of ammonium ions to nitrite ions in the wastewater is approximately 1: 1.32 required for the anaerobic ammonia oxidation reaction. The treated water subjected to the nitric acid type nitrification reaction treatment is introduced into the anaerobic ammonia oxidation reaction tank 20. Instead of such a method, it is also possible to use a method of bypassing the nitrite type nitrification reaction tank 10 for a part of the waste water. Specifically, a part of the wastewater to be treated is bypassed by the nitrite type nitrification reaction tank 10 and passed without being subjected to the nitrite type nitrification reaction treatment, while the rest of the wastewater is subsidized. The partial oxidation up to the nitrite nitrogen introduced into the nitrate nitrification reaction tank 10 is performed, for example, with respect to the total amount of ammonia nitrogen introduced, and then the nitrite nitrification reaction tank 10 is bypassed. The waste water and the waste water subjected to the nitrite type nitrification reaction treatment in the nitrite type nitrification reaction tank 10 may be remixed and then transferred to the anaerobic ammonia oxidation reaction tank 20. That is, it is possible to adjust the ratio of ammonium ions and nitrite ions transferred to the anaerobic ammonia oxidation reaction tank 20 to a ratio suitable for the anaerobic ammonia oxidation reaction treatment by the mixing ratio of the waste water at this time. .

  The anaerobic ammonia oxidation reaction tank 20 includes the remaining ammonia nitrogen that has not been converted to nitrite nitrogen in the nitrite type nitrification reaction, and nitrous acid produced by the nitrite type nitrification reaction, among the ammonia nitrogen contained in the waste water. It is a reaction tank in which an anaerobic ammonia oxidation reaction treatment (anaerobic ammonia oxidation reaction step) is performed in which the nitrogen is converted into molecular nitrogen and nitrate nitrogen by an anaerobic ammonia oxidation reaction. In this anaerobic ammonia oxidation reaction treatment, ammonium ions not oxidized in the nitrite type nitrification reaction are used as electron donors, and nitrite ions generated by partial oxidation of ammonium ions by the nitrite type nitrification reaction are used as electron acceptors. The nitrogen component contained in the waste water is converted into molecular nitrogen by the biological reaction represented by the above-described formula 1 to remove nitrogen. A part of the nitrogen component is converted into nitric acid (nitrate ions) and remains in the treated water together with unreacted ammonium ions and nitrite ions.

  The anaerobic ammonia oxidation reaction tank 20 holds anaerobic ammonia oxidizing bacteria group responsible for the anaerobic ammonia oxidation reaction. In FIG. 1, the anaerobic ammonia-oxidizing bacteria group is immobilized and held on the floating immobilization carrier 120. However, the anaerobic ammonia-oxidizing bacteria group can be in either an immobilized form or a non-immobilized form. . Further, the immobilization may be any of entrapping immobilization, adhesion immobilization, and self-granulation, and may be in any form of fluidized bed and fixed bed. However, from the viewpoint of securing the residence time and preventing the bacterial cell from flowing out of the reaction tank, a fixed form is preferable. The form of the immobilization carrier and the immobilization bed is the same as that of the immobilization carrier 110.

  As shown in FIG. 1, the anaerobic ammonia oxidation reaction tank 20 is provided with a stirring means 24 for stirring the waste water. The waste water that is subjected to the anaerobic ammonia oxidation reaction treatment is made uniform by the stirring means 24, and the uneven distribution of the waste water such as pH gradient is eliminated, so that the nitrogen removal rate is further increased. The agitation method is not limited to mechanical agitation, and may be a circulation agitation method using drainage or a diffused agitation method using oxygen-free gas. For example, the anaerobic ammonia oxidation reaction tank 20 is a gas lift type reaction tank in which the floating carrier is agitated by upward flow, an upward flow sludge bed type reaction tank in which anaerobic sludge is self-granulated by upward flow, etc. It is good.

  In addition, as shown in FIG. 1, the anaerobic ammonia oxidation reaction tank 20 supplies a chemical injection tank 25 for storing a pH adjusting agent and a pH adjusting agent stored in the chemical injection tank 25 to the water to be treated. A chemical injection pump 26 can be installed. As the pH adjuster, any of acids not containing non-reducing sulfur such as hydrochloric acid and sulfuric acid, and acids containing reducing sulfur such as hydrogen sulfide aqueous solution and sulfur dioxide aqueous solution can be used. By supplying acid to the wastewater as a pH adjuster, hydrogen ions consumed by the anaerobic ammonia oxidation reaction can be replenished, and the pH of the wastewater can be adjusted from neutral to weak alkali suitable for anaerobic ammonia oxidation reaction. It is possible to maintain in the area. Moreover, it becomes possible to raise the reductive sulfur compound density | concentration of the waste_water | drain which will be introduce | transduced into the autotrophic denitrification reaction tank 30 by supplying the acid containing reducible sulfur to waste_water | drain as a pH adjuster. Therefore, the drug cost related to the autotrophic denitrification treatment can be reduced.

  In the anaerobic ammonia oxidation reaction treatment, the pH of the waste water is maintained in a neutral to weak alkaline region, the dissolved oxygen concentration is restricted, and nitrite nitrogen that inhibits the anaerobic ammonia oxidation reaction is preferably 250 mg / L. Processing is limited to the following range. Specifically, the pH of the wastewater is adjusted to at least pH 6.5 or more and pH 9 or less, preferably pH 7.5 or more and pH 8.5 or less, more preferably pH 7.8 or more and pH 8.2 or less. The dissolved oxygen concentration in the wastewater is preferably less than 1.0 mg / L, although it depends on the form of microorganism immobilization. For example, it is reduced by aeration of low oxygen concentration gas such as nitrogen gas or addition of a reducing agent such as sodium sulfide. Is possible. When a reducing sulfur compound is used as the reducing agent, even if a part of the reducing sulfur compound flows out of the anaerobic ammonia oxidation reaction tank 20 without being reacted, it is introduced into the autotrophic denitrification reaction tank 30. Therefore, it is possible to reduce the cost of chemicals related to autotrophic denitrification treatment. Such gas aeration and addition of a reducing agent may be performed by providing an adjustment tank between the nitrite type nitrification reaction tank 10 and the anaerobic ammonia oxidation reaction tank 20, or an anaerobic ammonia oxidation reaction tank. 20 may be performed.

  The anaerobic ammonia oxidation reaction treatment is usually an anaerobic ammonia oxidation reaction treatment in which the residence time is such that the ammonium ions and nitrite ions contained in the wastewater react sufficiently and the consumption of ammonium ions is in a substantially steady state. The treated water is introduced into the autotrophic denitrification reaction tank 30. This treated water contains nitrate ions that are by-produced in the anaerobic ammonia oxidation reaction, and nitrite ions that have not been converted to molecular nitrogen in the anaerobic ammonia oxidation reaction may remain. Nitrite ions and nitrate ions can be removed in the autotrophic denitrification reaction tank 30.

  The autotrophic denitrification reaction tank 30 includes nitrite nitrogen contained in the waste water, nitrite nitrogen remaining after the anaerobic ammonia oxidation reaction, and nitrate nitrogen generated by the anaerobic ammonia oxidation reaction, This is a reaction tank in which an autotrophic denitrification reaction process (autotrophic denitrification reaction step) for converting to molecular nitrogen by autotrophic denitrification is performed. In other words, in autotrophic denitrification treatment, nitrite ions remaining in wastewater and nitrate ions generated by anaerobic ammonia oxidation reaction are reduced to molecular nitrogen by autotrophic denitrification. Thus, the wastewater is secondarily removed with nitrogen in addition to the anaerobic ammonia oxidation reaction.

  The autotrophic denitrification reaction tank 30 holds autotrophic denitrification bacteria that are responsible for autotrophic denitrification. In FIG. 1, the autotrophic denitrifying bacteria group is immobilized on a floating immobilization support 130 and held in the form of a fluidized bed. It is also possible to do. Further, the immobilization may be any of entrapping immobilization, adhesion immobilization, and self-granulation, and may be in any form of fluidized bed and fixed bed. However, from the viewpoint of securing the residence time and preventing the bacterial cell from flowing out of the reaction tank, a fixed form is preferable. The form of the immobilization carrier and the immobilization bed is the same as that of the immobilization carrier 110.

  The autotrophic denitrifying bacteria group has, for example, a composition containing autotrophic sulfur denitrifying bacteria and takes the form of anaerobic sludge. Sulfur denitrifying bacteria are facultatively autotrophic bacteria or obligately chemoautotrophic bacteria, and reduce reductive sulfur compounds using nitrite nitrogen and nitrate nitrogen as electron acceptors under anoxic conditions Sulfur-oxidizing bacteria that can oxidize can be used. That is, by supplying a reducing sulfur compound as an electron donor to such a sulfur denitrifying bacterium, it is possible to reduce nitrite nitrogen and nitrate nitrogen to molecular nitrogen and perform nitrogen removal treatment. The autotrophic denitrifying bacteria group uses an inorganic substance instead of an organic substance as a carbon source, and therefore has an advantage that wastewater treatment can be performed without supplying an organic substance such as methanol. Specifically, as the sulfur denitrifying bacteria, anaerobic sludge containing Thiobacillus denitrificans, Thiomicrospira denitrificans, Paracoccus denitrificans and the like can be obtained by habituation using a reducing sulfur compound.

  As shown in FIG. 1, the autotrophic denitrification reaction tank 30 is provided with a stirring means 34 for stirring the water to be treated. The agitation means 34 makes the waste water subjected to the autotrophic denitrification reaction uniform. The agitation method is not limited to mechanical agitation, and may be a circulation agitation method using drainage or a diffused agitation method using oxygen-free gas. For example, the autotrophic denitrification reaction tank 30 may be an upward flow sludge bed type reaction tank that self-granulates anaerobic sludge by an upward flow.

  In addition, as shown in FIG. 1, the autotrophic denitrification reaction tank 30 has a chemical injection tank 35 for storing a pH adjusting agent, and a chemical for supplying the pH adjusting agent stored in the chemical injection tank 35 to waste water. An injection pump 36 can be installed. As the pH adjuster, an alkali hydroxide such as sodium hydroxide, an alkali carbonate such as sodium carbonate, an alkali bicarbonate such as sodium bicarbonate, or the like can be used. A preferred pH adjuster is an alkali carbonate or alkali bicarbonate that can be used as an inorganic carbon source. By supplying alkali to the wastewater as a pH adjusting agent, it is possible to maintain the pH of the wastewater that has decreased with the production of sulfuric acid or the like in a neutral region suitable for the autotrophic denitrification reaction.

  The autotrophic denitrification reaction tank 30 is provided with sulfur supply means for supplying a reducing sulfur compound that serves as an electron donor for autotrophic denitrification reaction to waste water. In FIG. 1, the sulfur supply means includes a sulfur supply tank 37 that stores the reducing sulfur compound, and a sulfur supply pump 38 that supplies the reducing sulfur compound stored in the sulfur supply tank 37 to the waste water. The reducing sulfur compound is supplied from outside the reaction vessel. When the reducing sulfur compound is supplied to the wastewater and the dissolved oxygen concentration in the autotrophic denitrification reactor 30 is lowered, the autotrophic denitrifying bacteria group uses the reducing sulfur compound as an electron donor, In order to reduce nitrite nitrogen and nitrate nitrogen remaining in water to molecular nitrogen, the concentration of nitrogen components remaining in the treated water is further reduced, and the treated water quality is further improved than after anaerobic ammonia oxidation reaction treatment. It is possible to improve.

  As the reducing sulfur compounds, the elemental sulfur (elemental sulfur), sulfides such as sodium sulfide and potassium sulfide, sulfites such as sodium sulfite and calcium sulfite, which can be used as substrates by autotrophic denitrifying bacteria, Various reducing compounds such as hyposulfites such as sodium hyposulfite and thiosulfates such as sodium thiosulfate can be used. Such a reducing sulfur compound may be supplied in any form of a powdery body, a granular body, and a solution according to the kind.

  In addition, the sulfur supply means, instead of supplying the reducing sulfur compound from the outside of the reaction tank, immerses the sulfur-containing solid body containing the reducing sulfur compound in the reaction tank and puts the reducing sulfur compound in the waste water. It can also be set as the form which supplies directly. As the sulfur-containing solid body, a sulfur-containing material that is a solid molded product or a natural sulfur mineral can be used. Specific examples of the sulfur-containing material include a molded product obtained by mixing a powdery reductive sulfur compound and other binder compound and molding the mixture into an appropriate shape, for example, powdered elemental sulfur. A molded product obtained by mixing and calcium carbonate and compression-molding into a pellet can be suitably used. Since the charges of sulfate ions generated by oxidation of the reducing sulfur compound can be neutralized by calcium ions, it is possible to further stabilize the waste water treatment. Moreover, as sulfur mineral, specifically, natural sulfur, sulfide mineral or the like can be used. Such a sulfur-containing solid body can be used as a fixed bed for adhering and immobilizing autotrophic denitrifying bacteria, and also has an advantage that the management of chemical injection of reducing sulfur compounds is omitted.

  In the autotrophic denitrification treatment, the pH of the wastewater is maintained in a neutral region, and the dissolved oxygen concentration is limited. Specifically, the pH of the waste water is adjusted to pH 6 or more and pH 9 or less, preferably pH 7 or more and pH 8 or less. The dissolved oxygen concentration in the waste water is preferably adjusted to 1.0 mg / L or less, more preferably 0.3 mg / L or less. In the form in which the reducing sulfur compound is supplied from the outside of the reaction tank to the wastewater by the sulfur supply means, the reducing sulfur compound may be supplied periodically at regular time intervals, and the concentration of the nitrogen component in the wastewater is measured. Alternatively, it may be performed irregularly so that an appropriate amount is supplied according to the level of nitrogen component concentration. In addition, the supply amount of the reducing sulfur compound can be set to an appropriate amount such as, for example, an amount that becomes a reaction equivalent with respect to nitrate nitrogen and an amount that stabilizes the pH of the waste water. Then, the treated water subjected to the autotrophic denitrification reaction process is drained from the waste water treatment apparatus 1 to the outside.

  According to the waste water treatment apparatus or the waste water treatment method according to the first embodiment described above, the autotrophic denitrification reaction treatment is performed after the anaerobic ammonia oxidation reaction treatment, thereby performing the nitrogen removal treatment by the anaerobic ammonia oxidation reaction. Residual nitrite ions and nitrate ions can be removed as a secondary nitrogen treatment, so the concentration of the nitrogen component in the treated water is further reduced, compared to treatment using only the anaerobic ammonia oxidation reaction treatment. Water quality can be improved. Normally, when nitrogen removal treatment is performed by heterotrophic denitrification reaction with heterotrophic bacteria, it is necessary to supply organic matter such as methanol, which is approximately three times the nitrogen treatment amount. In the nitrogen reaction treatment, autotrophic denitrifying bacteria are used, so that it is not necessary to supply an organic substance as an electron donor, and it is possible to keep drug costs and BOD low. In addition, the autotrophic denitrifying bacteria group has less sludge production than the heterotrophic bacteria, so the surplus despite the addition of a reaction tank to perform secondary nitrogen removal treatment. The amount of sludge does not increase greatly, and the amount of waste and operating costs can be reduced.

  In the wastewater treatment apparatus or wastewater treatment method according to the first embodiment, a reaction tank in which a nitrite-type nitrification reaction is performed, a reaction tank in which an anaerobic ammonia oxidation reaction is performed, and an autotrophic denitrification reaction are performed. Since each reaction tank is a separate reaction tank, each biological treatment can be managed individually against fluctuations in the water temperature and nitrogen load of the wastewater, and it is easy to stabilize the wastewater treatment. There are advantages. Furthermore, even when the nitrite type nitrification treatment or anaerobic ammonia oxidation reaction treatment becomes unstable due to fluctuations in the temperature of the waste water or nitrogen load, the nitrite state depends on the operating conditions of the autotrophic denitrification reaction treatment. Nitrogen and nitrate nitrogen can be reliably removed.

[Modification]
In addition, the waste water treatment apparatus 1 according to the first embodiment described above, instead of the one-pass configuration illustrated in FIG. 1, may include an outlet of the autotrophic denitrification reactor 30 and an inlet of the anaerobic ammonia oxidation reactor 20, or The circulation path is formed by connecting the outlet of the autotrophic denitrification reaction tank 30 and the adjustment tank provided between the nitrite type nitrification reaction tank 10 and the anaerobic ammonia oxidation reaction tank 20 with a return pipe. In addition, a part of the treated water in the autotrophic denitrification reaction tank 30 may be returned to the anaerobic ammonia oxidation reaction tank 20. Thus, the nitrogen load with respect to the anaerobic ammonia oxidation reaction tank 20 can be adjusted suitably by performing the operation | movement which returns the treated water in the autotrophic denitrification reaction tank 30. FIG. Moreover, since the excess of the reducing sulfur compound supplied in the autotrophic denitrification reaction tank 30 can be returned together with the wastewater having a low dissolved oxygen concentration, the wastewater introduced into the anaerobic ammonia oxidation reaction tank 20 can be returned. The dissolved oxygen concentration can also be reduced efficiently. Along with the return of treated water in the autotrophic denitrification reaction tank 30, a process to remove ammonia nitrogen more reliably by performing an operation in which the production of nitrite ions is slightly increased in the nitrite type nitrification reaction treatment. It is also possible to do this.

[Second Embodiment]
Next, a wastewater treatment apparatus and a wastewater treatment method according to a second embodiment of the present invention will be described.

  FIG. 2 is a diagram showing a schematic configuration of a wastewater treatment apparatus according to the second embodiment of the present invention.

  As shown in FIG. 2, the waste water treatment apparatus 2 according to the second embodiment includes a single tank type anaerobic ammonia oxidation reaction tank 40 and an autotrophic denitrification reaction tank 30 arranged in series in this order. Yes. The wastewater treatment apparatus 2 according to the second embodiment is a wastewater treatment apparatus that biologically removes nitrogen-containing wastewater containing ammonia nitrogen using an anaerobic ammonia oxidation reaction, and is a nitrite type nitrification reaction The reaction tank in which the reaction is carried out and the reaction tank in which the anaerobic ammonia oxidation reaction is carried out are integrated into a reaction tank (single tank type anaerobic ammonia oxidation reaction tank 40), while an autotrophic denitrification reaction is carried out. The reaction tank is configured as a separate reaction tank (autotrophic denitrification reaction tank 30).

  In the waste water treatment apparatus 2, waste water as treated water is sequentially introduced into each reaction tank of the single tank type anaerobic ammonia oxidation reaction tank 40 and the autotrophic denitrification reaction tank 30, and is managed for each reaction tank. Biological treatment with microorganisms is carried out under the reaction conditions. That is, the waste water treatment apparatus 2 is a waste water treatment method in which each process of the single tank type anaerobic ammonia oxidation process and the autotrophic denitrification reaction process is sequentially performed in each separate reaction tank (the waste water treatment method according to the second embodiment). Is an apparatus that is suitably performed. Each of these reaction tanks may be either a tank type or a tank type, and any operation method of an SBR treatment type reaction tank and a continuous treatment type reaction tank may be employed.

  The single tank type anaerobic ammonia oxidation reaction tank 40 converts a part of ammonia nitrogen contained in the wastewater into nitrite nitrogen by a nitrite type nitrification reaction, and among the ammonia nitrogen contained in the wastewater, nitrous acid. Of the rest of ammonia nitrogen that was not converted to nitrite nitrogen in the nitrification reaction and the nitrite nitrogen produced by the nitrite nitrification reaction into molecular nitrogen and nitrate nitrogen by anaerobic ammonia oxidation reaction It is a reaction tank in which a single tank type anaerobic ammonia oxidation reaction treatment (single tank type anaerobic ammonia oxidation reaction process) is performed. The single tank type anaerobic ammonia oxidation reaction treatment includes, for example, a method in which biological treatment by anaerobic ammonia oxidizing bacteria group is performed under aeration restricted to a low oxygen concentration (CANON method), a biological treatment by nitrifying bacteria group A method in which treatment is performed under the condition of low oxygen concentration (OLAND method), a method in which anaerobic ammonia-oxidizing bacteria are immobilized inside an immobilization carrier, and nitrifying bacteria are adhered to the surface of the immobilization carrier It can be performed using an appropriate operation method such as (SNAP method).

  The single tank type anaerobic ammonia oxidation reaction tank 40 holds a nitrifying bacteria group involved in the nitrite type nitrification reaction and an anaerobic ammonia oxidizing bacteria group involved in the anaerobic ammonia oxidation reaction. In FIG. 2, the nitrifying bacteria group and the anaerobic ammonia oxidizing bacteria group are immobilized on the floating immobilization carrier 140 and held in the form of a fluidized bed. Any of immobilization may be used, and either a fluidized bed or a fixed bed may be employed. However, since it is difficult to maintain the symbiosis between the nitrifying bacteria group and the anaerobic ammonia oxidizing bacteria group, it is preferable to take the acclimatization period and fix them. The form of the immobilization carrier and the immobilization bed is the same as that of the immobilization carrier 110, but in the case of the SNAP method, a porous and three-dimensional shape carrier is preferable.

  As shown in FIG. 2, the single tank type anaerobic ammonia oxidation reaction tank 40 is provided with a diffuser pipe 42 that diffuses air into the waste water and a blower 43 that feeds air into the diffuser pipe 42. The single tank type anaerobic ammonia oxidation reaction tank 40 may be a vertical cylindrical tank type reaction tank, and a gas lift type reaction tank may be provided by disposing an aeration tube 42 at the bottom. By using a gas lift type reaction vessel, the gas-liquid mass transfer of oxygen becomes a rate-determining step, and the process can be prevented from becoming unstable.

  In addition, as shown in FIG. 2, the single tank type anaerobic ammonia oxidation reaction tank 40 supplies a chemical injection tank 45 storing a pH adjusting agent and a pH adjusting agent stored in the chemical injection tank 45 to the drainage. A chemical injection pump 46 can be installed. Examples of pH adjusters include alkali hydroxides such as sodium hydroxide, alkali carbonates such as sodium carbonate, alkali bicarbonates such as sodium bicarbonate, and acids that do not contain non-reducing sulfur such as hydrochloric acid and sulfuric acid. Alternatively, an acid containing reducing sulfur such as an aqueous hydrogen sulfide solution or an aqueous sulfur dioxide solution is used. By supplying alkali or acid to the wastewater, it is possible to maintain the pH of the wastewater in a region near a weak alkali suitable for the single tank type anaerobic ammonia oxidation reaction. Moreover, it becomes possible to raise the reductive sulfur compound density | concentration of the waste_water | drain which will be introduce | transduced into the autotrophic denitrification reaction tank 30 by supplying the acid containing reducible sulfur to waste_water | drain as a pH adjuster. Therefore, the drug cost related to the autotrophic denitrification treatment can be reduced.

  In the single tank type anaerobic ammonia oxidation reaction treatment, the pH of the waste water is maintained in a region near weak alkali, and the treatment is performed while limiting the dissolved oxygen concentration. Specifically, the pH of the waste water is adjusted to be pH 7.5 or more and pH 9 or less, preferably pH 7.5 or more and pH 8 or less. The concentration of dissolved oxygen in the wastewater is measured by measuring the concentration of ammonia nitrogen contained in the wastewater, and at least 4.0 mg / L or less, while suppressing nitrite oxidation, depending on the nitrogen load and nitrogen removal rate The mold nitrification reaction and the anaerobic ammonia oxidation reaction may be controlled.

  Single tank type anaerobic ammonia oxidation reaction treatment is usually a residence time in which the ammonium ions and nitrite ions contained in the waste water react sufficiently and the consumption of ammonium ions becomes a substantially steady state. After the basic ammonia oxidation reaction treatment, the treated water is introduced into the autotrophic denitrification reaction tank 30. This wastewater contains nitrate ions by-produced in the anaerobic ammonia oxidation reaction, as well as two ammonium ions and nitrite ions that were not converted to nitrogen gas and nitrate ions in the single tank anaerobic ammonia oxidation reaction. Although a large amount may remain as compared with the tank type, nitrite ions and nitrate ions can be removed by the autotrophic denitrification reaction tank 30.

  The autotrophic denitrification reaction tank 30 is the same as that provided in the wastewater treatment apparatus 1 according to the first embodiment, among the nitrite nitrogen contained in the wastewater, the nitrous acid remaining after the anaerobic ammonia oxidation reaction. An autotrophic denitrification process (autotrophic denitrification process) is performed to convert nitrate nitrogen and nitrate nitrogen produced by anaerobic ammonia oxidation reaction to molecular nitrogen by autotrophic denitrification. It is a reaction tank. Autotrophic denitrification treatment usually has a residence time that allows sufficient denitrification of nitrite ions and nitrate ions contained in the wastewater. Waste water is discharged from the processing apparatus 2 to the outside.

  According to the waste water treatment apparatus or the waste water treatment method according to the second embodiment described above, the autotrophic denitrification reaction treatment is performed after the single tank type anaerobic ammonia oxidation reaction treatment. Since the remaining nitrite ions and nitrate ions can be secondarily removed after the removal treatment, the concentration of the nitrogen component in the treated water is further reduced and only the anaerobic ammonia oxidation reaction treatment is performed. Compared with, the quality of treated water can be improved. In addition, in the autotrophic denitrification reaction treatment, since autotrophic denitrifying bacteria are used, it is not necessary to supply an organic substance as an electron donor, and the drug cost and BOD can be kept low. Moreover, although a reaction tank is added to perform a secondary nitrogen removal process, the amount of surplus sludge does not increase greatly, and the amount of waste and operating costs can be suppressed.

  In the waste water treatment apparatus or waste water treatment method according to the first embodiment, the reaction tank in which the nitrite-type nitrification reaction is performed and the reaction tank in which the anaerobic ammonia oxidation reaction are performed are integrated reaction tanks. The processing apparatus can be reduced in size. On the other hand, since the reaction tank in which the autotrophic denitrification reaction is performed is a separate reaction tank, the nitrogen component remaining in the one-tank type anaerobic ammonia oxidation reaction treatment can be reliably removed with nitrogen. Is possible. That is, even when the one-tank type anaerobic ammonia oxidation reaction treatment becomes unstable, nitrite nitrogen and nitrate nitrogen can be reliably removed depending on the operating conditions of the autotrophic denitrification reaction treatment. In addition, it is not always necessary to strictly control the single tank type anaerobic ammonia oxidation reaction, and it is possible to operate with a wide range so that the ratio of ammonium ion to nitrite ion becomes excessive. become.

[Third Embodiment]
Next, a waste water treatment apparatus and a waste water treatment method according to a third embodiment of the present invention will be described.

  FIG. 3 is a diagram showing a schematic configuration of a waste water treatment apparatus according to the third embodiment of the present invention.

  As shown in FIG. 3, the waste water treatment apparatus 3 according to the third embodiment includes a denitrification reaction tank (single tank type denitrification reaction tank) 50 as a single tank type reaction tank that performs biological treatment. Yes. The wastewater treatment apparatus 3 according to the third embodiment is a wastewater treatment apparatus that biologically removes nitrogen-containing wastewater containing ammonia nitrogen using an anaerobic ammonia oxidation reaction, and is a nitrite type nitrification reaction And a reaction tank in which an anaerobic ammonia oxidation reaction is performed and a reaction tank in which an autotrophic denitrification reaction is performed are integrated into a single reaction tank (single tank denitrification reaction tank 50). Have.

  The waste water treatment apparatus 3 is an apparatus in which a waste water treatment method (a waste water treatment method according to the third embodiment) in which a single tank type denitrification reaction step is performed in a single tank reaction tank is suitably performed. This reaction tank may be either a tank type or a tank type, and any operation method of an SBR treatment type reaction tank and a continuous treatment type reaction tank may be employed.

  The single tank type denitrification reaction tank 50 converts a part of ammonia nitrogen contained in the wastewater into nitrite nitrogen by a nitrite type nitrification reaction, and among the ammonia nitrogen contained in the wastewater, nitrite type nitrification. The remainder of the ammonia nitrogen that was not converted to nitrite nitrogen in the reaction and the nitrite nitrogen produced by the nitrite type nitrification reaction are converted into molecular nitrogen and nitrate nitrogen by the anaerobic ammonia oxidation reaction, In addition, among the nitrite nitrogen contained in the wastewater, the nitrite nitrogen remaining after the anaerobic ammonia oxidation reaction and the nitrate nitrogen produced by the anaerobic ammonia oxidation reaction are separated by an autotrophic denitrification reaction. It is a reaction tank in which a single tank type denitrification reaction process (single tank type denitrification reaction step) for conversion into molecular nitrogen is performed.

  In the single tank type denitrification reaction tank 50, the nitrifying bacteria group involved in the nitrite type nitrification reaction, the anaerobic ammonia oxidizing bacteria group involved in the anaerobic ammonia oxidation reaction, and the autotrophic process involved in the autotrophic denitrification reaction are included. Sexual denitrifying bacteria are retained. In FIG. 3, the nitrifying bacteria group, the anaerobic ammonia oxidizing bacteria group, and the autotrophic denitrifying bacteria group are immobilized on the floating immobilization carrier 150 and held in the form of a fluidized bed. The formation may be performed by either entrapping immobilization or adhesion immobilization, and may be in any form of a fluidized bed and a fixed bed. However, since it is difficult to maintain the symbiosis between the nitrifying bacteria group and the anaerobic ammonia oxidizing bacteria group, it is preferable to take the acclimatization period and fix them. The form of the immobilization carrier and the immobilization bed is the same as that of the immobilization carrier 110, but in the case of the SNAP method, a porous and three-dimensional shape carrier is preferable.

  As shown in FIG. 3, the single tank type denitrification reaction tank 50 is provided with a diffuser pipe 52 that diffuses air into the drainage and a blower 53 that sends air to the diffuser pipe 52. The single tank type denitrification reaction tank 50 may be a vertical cylindrical tank type reaction tank, and may be a gas lift type reaction tank by disposing an aeration tube 52 at the bottom. By using a gas lift type reaction vessel, the gas-liquid mass transfer of oxygen becomes a rate-determining step, and the process can be prevented from becoming unstable.

  Further, as shown in FIG. 3, the single tank type denitrification reaction tank 50 includes a chemical injection tank 55 that stores a pH adjusting agent, and a chemical that supplies the pH adjusting agent stored in the chemical injection tank 55 to waste water. An injection pump 56 can be installed. Examples of pH adjusters include alkali hydroxides such as sodium hydroxide, alkali carbonates such as sodium carbonate, alkali bicarbonates such as sodium bicarbonate, and acids that do not contain non-reducing sulfur such as hydrochloric acid and sulfuric acid. Alternatively, an acid containing reducing sulfur such as an aqueous hydrogen sulfide solution or an aqueous sulfur dioxide solution is used. By supplying alkali or acid to the wastewater, it is possible to maintain the pH of the wastewater in a region near a weak alkali suitable for the single tank type anaerobic ammonia oxidation reaction. Further, by supplying an acid containing reductive sulfur as a pH adjuster to the wastewater, it is possible to increase the concentration of the reducible sulfur compound in the wastewater, so that the chemical cost can be reduced.

  The single tank type denitrification reaction tank 50 is provided with sulfur supply means for supplying a reducing sulfur compound that serves as an electron donor for the autotrophic denitrification reaction to the waste water. In FIG. 3, the sulfur supply means includes a sulfur supply tank 57 that stores the reducing sulfur compound, and a sulfur supply pump 58 that supplies the reducing sulfur compound stored in the sulfur supply tank 57 to the waste water. The reducing sulfur compound is supplied from outside the reaction vessel. About the form of a sulfur supply means, the thing similar in the waste water treatment apparatus 1 is applicable. In place of the sulfur supply tank 57 and the sulfur supply pump 58 in FIG. 3, a mode in which the sulfur-containing solid body is immersed in wastewater and the autotrophic denitrifying bacteria are attached and fixed to the sulfur-containing solid body is operated. It can also be taken. This makes it possible to stably maintain the activity particularly by the autotrophic denitrifying bacteria group. At this time, the gas lift pipe shape may be formed by a sulfur-containing solid body so that a circulation flow is easily formed.

  In the single tank type denitrification treatment, the pH of the waste water is maintained in a region near weak alkali, and the treatment is performed while limiting the dissolved oxygen concentration. Specifically, the pH of the waste water is adjusted to be pH 7.5 or more and pH 9 or less, preferably pH 7.5 or more and pH 8 or less. The concentration of dissolved oxygen in the wastewater is measured by measuring the concentration of ammonia nitrogen contained in the wastewater, and at least 4.0 mg / L or less, while suppressing nitrite oxidation, depending on the nitrogen load and nitrogen removal rate The mold nitrification reaction and the anaerobic ammonia oxidation reaction may be controlled. Although depending on the form of immobilization of microorganisms, from the viewpoint of ensuring a nitrogen removal rate by autotrophic denitrification, the dissolved oxygen concentration is preferably limited to a range of 1.0 mg / L or less. More preferably, it is limited to a range of 5 mg / L or less. Single-tank denitrification treatment is usually treated with a single-tank denitrification reaction treated with a residence time that can sufficiently denitrify nitrate ions contained in the wastewater by supplying a reducing sulfur compound. Is drained from the waste water treatment device 3 to the outside.

  According to the waste water treatment apparatus or the waste water treatment method according to the third embodiment described above, in the single tank type denitrification reaction treatment, the nitrite ions and nitrate ions remaining after the nitrogen removal treatment by the anaerobic ammonia oxidation reaction are secondary. Therefore, the concentration of the nitrogen component of the treated water can be further reduced, and the quality of the treated water can be improved as compared with the treatment of only the anaerobic ammonia oxidation reaction treatment. In the single tank type denitrification reaction treatment, since an autotrophic denitrifying bacterium group is used, it is not necessary to supply an organic substance as an electron donor, and the drug cost and BOD can be kept low. In addition, since the autotrophic denitrifying bacteria group has a small amount of sludge generation, the amount of waste and the operation cost can be suppressed.

  Moreover, in the waste water treatment apparatus or waste water treatment method according to the third embodiment, the reaction tank in which the nitrite type nitrification reaction is performed, the reaction tank in which the anaerobic ammonia oxidation reaction is performed, and the reaction in which the autotrophic denitrification reaction is performed. Since the tank is an integral reaction tank, the wastewater treatment apparatus can be further downsized. In the single tank type denitrification reaction, the nitrite ion concentration and the nitrate ion concentration can be controlled by the aeration amount and the sulfur supply amount. Therefore, it is not always necessary to strictly control the nitrite type nitrification reaction, and the nitrite type nitrification reaction can be operated with a width so that the ratio of ammonium ion to nitrite ion becomes excessive, or nitrite oxidation reaction It is also possible to drive while mitigating the suppression.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using the Example of this invention, the technical scope of this invention is not limited to this.

[Example 1]
As Example 1, wastewater containing ammonia nitrogen and nitrite nitrogen was subjected to an anaerobic ammonia oxidation reaction treatment and then subjected to an autotrophic denitrification reaction treatment, and the treated water quality was evaluated. In addition, this Example 1 simulates the waste water treatment apparatus and waste water treatment method which concern on 1st Embodiment shown in FIG.

  The anaerobic ammonia oxidation reaction treatment tank contains ammonium ions and nitrite ions as nitrogen components, the ammonium ion concentration is 155 mg-N / L, the nitrite ion concentration is 202 mg-N / L, and the water temperature is 30. Anaerobic ammonia oxidation reaction treatment was performed by passing waste water (raw water) at a temperature of ° C. Subsequently, the treated water after the anaerobic ammonia oxidation reaction treatment was passed through an autotrophic denitrification reaction tank. In an autotrophic denitrification reaction tank, a reducing sulfur compound with an S / N ratio of 1 or more times is added to the wastewater, and the pH of the wastewater is adjusted to be near neutral, and the autotrophic denitrification tank is used. Reaction treatment was performed. And the nitrogen concentration was measured about the treated water obtained by the continuous process by these anaerobic ammonia oxidation reaction process and autotrophic denitrification reaction process.

  FIG. 4 is a view showing the nitrogen concentration of wastewater treated by the wastewater treatment method according to Example 1 of the present invention.

  In FIG. 4, the vertical axis represents the concentration of each nitrogen component contained in the waste water (nitrogen concentration (mg-N / L)). In FIG. 4, the nitrogen concentration of the waste water before treatment (raw water) and the nitrogen concentration of the control waste water (Comparative Example 1) that was not subjected to the autotrophic denitrification treatment after the anaerobic ammonia oxidation reaction treatment are shown. It also shows.

  As shown in FIG. 4, in Comparative Example 1, by performing anaerobic ammonia oxidation reaction treatment, the ammonium ion concentration was 4 mg-N / L, the nitrite ion concentration was 3 mg-N / L, and the nitrate ion concentration was 40 mg- N / L treated water is obtained, and it can be seen that a part of the nitrite ions and a large amount of by-produced nitrate ions remain in the treated water. On the other hand, in Example 1, by further performing an autotrophic denitrification reaction treatment after the anaerobic ammonia oxidation reaction treatment, the ammonium ion concentration is 4 mg-N / L and the nitrite ion concentration is approximately 0 mg-N. / L, treated water having a nitrate ion concentration of 6 mg-N / L is obtained. In this way, by performing secondary nitrogen removal treatment using autotrophic denitrifying bacteria, nitrite ions and nitrate ions remain substantially free of nitrogen components remaining after anaerobic ammonia oxidation reaction treatment. A high nitrogen removal rate of removing about 80% is achieved, and it can be confirmed that a high level of treated water quality can be realized.

[Example 2]
As Example 2, wastewater containing ammonia nitrogen and nitrate nitrogen was subjected to a single tank type anaerobic ammonia oxidation reaction treatment, and then subjected to an autotrophic denitrification reaction treatment, and the quality of the treated water was evaluated. In addition, this Example 2 simulates the waste water treatment apparatus and waste water treatment method which concern on 2nd Embodiment shown in FIG.

  The single tank type anaerobic ammonia oxidation reaction treatment tank contains ammonium ions and nitrate ions as nitrogen components, the ammonium ion concentration is 16 mg-N / L, the nitrate ion concentration is 3 mg-N / L, and the water temperature is Waste water (raw water) at 20 ° C. was passed through to perform a single tank type anaerobic ammonia oxidation reaction treatment. Subsequently, the treated water after the single tank type anaerobic ammonia oxidation reaction treatment was passed through the autotrophic denitrification reaction tank. In an autotrophic denitrification reaction tank, a reducing sulfur compound with an S / N ratio of 1 or more times is added to the wastewater, and the pH of the wastewater is adjusted to be near neutral, and the autotrophic denitrification tank is used. Reaction treatment was performed. And the nitrogen concentration was measured about the treated water obtained by the continuous process by these single tank type anaerobic ammonia oxidation reaction process and autotrophic denitrification reaction process.

  FIG. 5 is a diagram showing the nitrogen concentration of wastewater treated by the wastewater treatment method according to Example 2 of the present invention.

  In FIG. 5, the vertical axis represents the concentration of each nitrogen component (nitrogen concentration (mg-N / L)) contained in the waste water. FIG. 5 shows the nitrogen concentration of the waste water (raw water) before the treatment and the nitrogen concentration of the control waste water (Comparative Example 2) that was not subjected to the autotrophic denitrification treatment after the anaerobic ammonia oxidation reaction treatment. It also shows.

  As shown in FIG. 5, in Comparative Example 2, by performing a single tank type anaerobic ammonia oxidation reaction treatment, the ammonium ion concentration was 2 mg-N / L, the nitrite ion concentration was 2 mg-N / L, and the nitrate ion concentration. 4 mg-N / L of treated water is obtained, and it can be seen that ammonia ions and nitrite ions partially remain in the treated water, and a large amount of nitrate ions remain. On the other hand, in Example 2, by further performing an autotrophic denitrification treatment after the single tank type anaerobic ammonia oxidation reaction treatment, the ammonium ion concentration was 2 mg-N / L, and the nitrite ion concentration was substantially reduced. Treated water having 0 mg-N / L and a nitrate ion concentration of approximately 0 mg-N / L is obtained. In this way, by performing secondary nitrogen removal treatment using autotrophic denitrifying bacteria, nitrite ions and nitrate ions remain substantially free of nitrogen components remaining after anaerobic ammonia oxidation reaction treatment. A high nitrogen removal rate of removing about 75% is achieved, and it can be confirmed that a high level of treated water quality can be realized.

DESCRIPTION OF SYMBOLS 1 Waste water treatment equipment 2 Waste water treatment equipment 3 Waste water treatment equipment 8 Raw water pump 10 Nitrite type nitrification reaction tank 12 Aeration pipe 13 Blower 15 Chemical injection tank 16 Chemical injection pump 20 Anaerobic ammonia tank 24 Stirring means 25 Chemical injection tank 26 Chemical injection Pump 30 Autotrophic denitrification tank 34 Stirring means 35 Chemical injection tank 36 Chemical injection pump 37 Sulfur supply tank 38 Sulfur supply pump 40 Single tank anaerobic ammonia oxidation reaction tank 42 Aeration pipe 43 Blower 45 Chemical injection tank 46 Chemical injection pump 50 Single tank type denitrification reaction tank 52 Aeration pipe 53 Blower 55 Chemical injection tank 56 Chemical injection pump 57 Sulfur supply tank 58 Sulfur supply pump 110 Immobilization carrier 120 Immobilization carrier 130 Immobilization carrier 140 Immobilization carrier 150 Immobilization carrier

Claims (6)

A wastewater treatment apparatus for biologically nitrogen removal treatment of wastewater containing ammonia nitrogen using anaerobic ammonia oxidation reaction,
A part of the ammonia nitrogen contained in the waste water is converted into nitrite nitrogen by a nitrite type nitrification reaction,
The remaining ammonia nitrogen and the nitrite nitrogen are converted into molecular nitrogen and nitrate nitrogen by an anaerobic ammonia oxidation reaction,
A wastewater treatment apparatus characterized in that nitrite nitrogen remaining after an anaerobic ammonia oxidation reaction and the nitrate nitrogen are converted to molecular nitrogen by an autotrophic denitrification reaction to remove nitrogen. A part of ammonia nitrogen contained in the waste water, a nitrite type nitrification reaction tank for converting into nitrite nitrogen by a nitrite type nitrification reaction;
An anaerobic ammonia oxidation reaction tank for converting the remainder of the ammonia nitrogen and the nitrite nitrogen into molecular nitrogen and nitrate nitrogen by an anaerobic ammonia oxidation reaction;
An autotrophic denitrification reactor that converts nitrite nitrogen remaining after the anaerobic ammonia oxidation reaction and the nitrate nitrogen to molecular nitrogen by autotrophic denitrification;
The wastewater treatment apparatus according to claim 1, comprising: A part of the ammonia nitrogen contained in the waste water is converted into nitrite nitrogen by a nitrite type nitrification reaction,
A single tank anaerobic ammonia oxidation reaction tank for converting the remainder of the ammonia nitrogen and the nitrite nitrogen into molecular nitrogen and nitrate nitrogen by an anaerobic ammonia oxidation reaction;
An autotrophic denitrification reactor that converts nitrite nitrogen remaining after the anaerobic ammonia oxidation reaction and the nitrate nitrogen to molecular nitrogen by autotrophic denitrification;
The waste water treatment apparatus according to claim 1, comprising: A part of the ammonia nitrogen contained in the waste water is converted into nitrite nitrogen by a nitrite type nitrification reaction,
Converting the remainder of the ammonia nitrogen and the nitrite nitrogen into molecular nitrogen and nitrate nitrogen by an anaerobic ammonia oxidation reaction; and
Provide a denitrification reaction tank that converts the nitrite nitrogen remaining after the anaerobic ammonia oxidation reaction and the nitrate nitrogen into molecular nitrogen by autotrophic denitrification as a single tank reaction tank The wastewater treatment apparatus according to claim 1.   A sulfur supply means for supplying a reducing sulfur compound that acts as an electron donor for the autotrophic denitrification reaction is installed in a reaction tank in which the autotrophic denitrification reaction is performed. The waste water treatment apparatus according to any one of claims 2 to 4. A wastewater treatment method for biologically nitrogen removal treatment of wastewater containing ammonia nitrogen using anaerobic ammonia oxidation reaction,
A nitrite type nitrification reaction step for converting a part of ammonia nitrogen contained in the waste water into nitrite nitrogen by a nitrite type nitrification reaction,
Anaerobic ammonia oxidation step of converting the remainder of the ammonia nitrogen and the nitrite nitrogen into molecular nitrogen and nitrate nitrogen by an anaerobic ammonia oxidation reaction;
It includes an autotrophic denitrification reaction step of converting nitrite nitrogen remaining after anaerobic ammonia oxidation reaction and the nitrate nitrogen into molecular nitrogen by autotrophic denitrification. Wastewater treatment method.

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