Method and system for removing nitrogen from ammonia-containing water to be treated.

Abstract

The present invention provides a method and system for stably treating water containing ammonia nitrogen in the low concentration range to an even lower concentration. [Solution] Ammonia nitrogen (NH4 + -N) A method for removing nitrogen from ammonia-containing water to be treated, in which the concentration is 100 mg / L or less, using an Anammox process system which includes a reaction vessel containing ammonia-oxidizing bacteria and Anammox bacteria and aerating the water to be treated by introducing the water to be treated into the reaction vessel, wherein the pH in the reaction vessel is 7.0 to 9.0 and NH4 is below 10.0 mg / L + A method for obtaining treated water with -N concentration, and an Anammox process system for carrying out the method.

Description

[Technical Field]

[0001] This disclosure relates to a method and system for treating ammonia-containing water to remove nitrogen. [Background technology]

[0002] From the perspective of impacts on ecosystems and health, excessive nitrogen content in wastewater is undesirable, and wastewater standards for nitrogen concentration have been established. More specifically, the nitrogen concentration referred to here is the concentration of nitrogen compounds, and ammonia in particular is the main nitrogen compound that accounts for the majority of the nitrogen content in typical influent water of wastewater treatment facilities. For example, dewatered sewage sludge filtrate typically contains 500-1000 mg-N / L of nitrogen compounds, while wastewater from semiconductor manufacturing processes, precious metals industries, and chemical industries may contain 50-100 mg-N / L of nitrogen compounds.

[0003] A method for removing nitrogen from ammonia-containing water to be treated using microorganisms contained in (or collected from) sludge, wastewater, etc., that is, a treatment method for removing nitrogen compounds from water to be treated, involves first removing ammonia (NH4 + ) to nitric acid (NO3 - After oxidation (nitrification) to nitric acid (NO3 - The nitrification-denitrification method is used, which reduces (denitrifies) ammonia to nitrogen gas (N2). However, this method has disadvantages, such as requiring high aeration power to supply oxygen for oxidizing ammonia because it is necessary to oxidize the entire amount of ammonia to be removed to nitric acid, and requiring the addition of organic chemicals such as methanol to promote the denitrification reaction.

[0004] As an alternative to nitrification-denitrification method for treating ammonia-containing water, (1) ammonia (NH4) in the water to be treated. + Approximately half of ) is nitrite (NO2 - (2) an ammonia oxidation reaction (nitrite-type nitrification reaction) that oxidizes to nitrite (NO2) under anaerobic conditions - ) and ammonia (NH4 +Development of anammox process technology that utilizes a combination of the above reaction to convert into nitrogen gas (N₂) via anammox reaction has been carried out. Anammox is originally a term referring to Anaerobic Ammonium Oxidation under anaerobic conditions, and the chemosynthetic autotrophic bacteria responsible for the anammox reaction are called anammox bacteria. Among anammox processes that treat ammonia-containing water using the anammox reaction, the method combining the above (1) nitritation reaction and (2) anammox reaction is particularly called Partial nitritation-anammox (PNA). In PNA, approximately half of the ammonia to be removed can be directly converted into nitrogen gas without going through nitrite or nitrate, so the amount of aeration and the use of chemicals can be reduced. In addition, compared with the conventional nitrification-denitrification method, the amount of excess sludge generated can also be significantly reduced (for example, by 80% or more), and its practical application is being promoted as an energy-saving treatment process.

[0005] Conventionally, in the PNA-type anammox process, the reaction (1) and reaction (2) described above are carried out in two separate reaction tanks. Particularly, in reaction (1), in order to oxidize approximately half of the ammonia in raw water into nitrite, it was necessary to accurately adjust the oxidation amount or nitrification rate using an ammonia concentration meter or the like (see, for example, Patent Documents 1 to 3). However, in recent years, development of a single-tank PNA anammox process (in this specification, the notation PNA is omitted and it is also simply referred to as "single-tank") that performs reactions (1) and (2) in the same reaction tank has been progressing, and it has attracted attention as a simpler method. In the single-tank system, the transfer of water to be treated from the first tank with adjusted nitrification rate to the second tank is eliminated, and space saving can also be achieved compared with the two-tank PNA system (the notation PNA is omitted and it is also simply referred to as "two-tank") for ammonia removal.

[0006] However, in the single-tank anammox process, there is a third reaction that hinders the process combining the above reactions (1) and (2), that is, (3) nitrite (NO₂ - ) into nitric acid (NO₃ -The nitrite oxidation reaction, in which ammonia is oxidized, is likely to occur, and establishing a technology to suppress this third reaction is a challenge. Nitrite-oxidizing bacteria can inevitably be present in sludge, wastewater, etc. In other words, the single-tank Anammox method is responsible for ammonia oxidation by ammonia-oxidizing bacteria (AOB) and NH4 + and NO2 - This process is carried out by Anammox bacteria (AXB) which convert nitrite (NO2) into nitrogen gas. - Nitrate NO3 - Nitrite-oxidizing bacteria (NOBs) that oxidize to NO2 should be used in the Anammox reaction. - Because it consumes nitrogen, it is an inhibitor that significantly reduces the nitrogen removal rate. Therefore, suppressing NOB activity is an important challenge.

[0007] Patent Document 4 describes a wastewater treatment method using a single-tank anammox process, which controls the dissolved oxygen concentration of the wastewater in the reaction tank to 0.5 mg / L or more and 4.0 mg / L or less, and controls the ammonia concentration of the wastewater in the reaction tank or the treated water discharged from the reaction tank to 10 mg-N / L or more and 500 mg-N / L or less.

[0008] In the example described in Patent Document 4, wastewater with a nitrogen concentration of 500-1000 mg-N / L, or 500-1000 milligrams per liter, was used as the wastewater subject to treatment. NOB is NH4 remaining in the reaction vessel. + This is why the invention described in Patent Document 4, although a technology aimed at nitrogen removal treatment, maintained the ammonia concentration of the treated water (water after treatment) or the water in the reaction vessel in a relatively high range of 10 mg / L to 500 mg / L, thereby enabling stable nitrogen removal treatment. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2010-017639 [Patent Document 2] Japanese Patent Publication No. 2010-137152 [Patent Document 3] Japanese Patent Publication No. 2019-202244 [Patent Document 4] Japanese Patent Publication No. 2023-023108 [Overview of the project]

[0010] However, if treated water is discharged into a river, for example, it may be preferable to reduce the ammonia nitrogen level to less than 10 mg / L, and the prior art may be unsuitable if the treatment is to reduce it to, for example, 9.5 mg / L or less. Nitrogen in effluent water is ammonia nitrogen (NH4 + -N), nitrate nitrogen (NO3 - -N), Nitrite nitrogen (NO2) - Since it is evaluated based on the total nitrogen concentration which may include -N, even considering the wastewater standards for nitrogen concentration, NH4 + A lower concentration of -N is desirable.

[0011] This disclosure provides a method and system for stably treating water to be treated, which originally has a low nitrogen concentration, particularly an ammonia nitrogen concentration, to an even lower concentration.

[0012] This disclosure includes at least the following embodiments: [1] Ammonia nitrogen (NH4) + -N) A method for removing nitrogen from ammonia-containing water to be treated, wherein the concentration is 100 mg / L or less. An Anammox process system is used, which includes a reaction vessel containing ammonia-oxidizing bacteria and Anammox bacteria and aerating the reaction vessel, and the water to be treated is introduced into the reaction vessel to perform nitrogen removal treatment on the water to be treated. Here, the pH inside the reaction vessel is set to 7.0-9.0. NH4 below 10.0 mg / L + A method for obtaining treated water with N concentration. [2] The nitrogen load of the reaction vessel is set to 0.05-1.0 kg-N / m³. 3 Maintain / day The water temperature in the reaction vessel is set to 20-40°C. The method according to [1], wherein the dissolved oxygen concentration in the reaction vessel is controlled to 0.1 to 3.0 mg / L. [3] The aforementioned Anammox process system is NH4 of the water to be treated before being introduced into the reaction vessel + -N concentration (A) and NO3 - -Means for measuring the N concentration (B), NH4 in the treated water after nitrogen removal treatment in the aforementioned reaction tank + -N concentration (C) and NO3 ― - Means for measuring the N concentration (D) The method includes the following formula: F = α(AC) - (DB) When the control value F calculated based on is a negative value, the dissolved oxygen concentration in the reaction vessel is reduced, NH4 + The method according to [1] or [2], wherein one or more controls are performed by increasing the -N concentration and / or increasing the pH, where α is a value in the range of 0.07 to 0.15. [4] The Anammox process system further includes an anaerobic tank upstream of the reaction tank that does not supply oxygen, and the water to be treated is denitrified by denitrifying bacteria in the anaerobic tank to produce NO3 - The method according to any one of [1] to [3], wherein the N concentration is reduced before being introduced into the reaction vessel. [5] An Anammox process system for performing nitrogen removal treatment on water to be treated by the method described in any one of [1] to [4], A reaction vessel having an inlet and an outlet, A blower configured to aerate the water remaining in the reaction vessel, Ammonia-oxidizing bacteria and Anammox bacteria contained in the reaction vessel, A pH measuring device configured to measure the pH inside a reaction vessel, NH4 of the water to be treated before being introduced into the reaction tank + -N concentration (A) and NO3- A first ammonia concentration measuring device and a first nitrate concentration measuring device configured to measure the -N concentration (B), respectively. NH4 in the treated water after nitrogen removal treatment in the aforementioned reaction tank + -N concentration (C) and NO3 ― A second ammonia concentration measuring device and a second nitrate concentration measuring device configured to measure the -N concentration (D), respectively. A system that includes this. [6] The system further includes a control device, the control device receiving measurement data from the first ammonia concentration measuring device and the first nitrate concentration measuring device and the second ammonia concentration measuring device and the second nitrate concentration measuring device to calculate the control value F, and when F is a negative value, the system is configured to (a) send a command to the blower to reduce the aeration rate, (b) send a command to a valve attached to the inlet to increase the inflow rate of the water to be treated into the reaction tank, or (c) do both, as described in [5]. [7] The system according to [6], wherein the reaction vessel is equipped with an alkaline chemical supply device for adjusting the pH inside the reaction vessel, and the control device is configured to raise the pH inside the reaction vessel by sending a command to the alkaline chemical supply device to add an alkaline chemical to the reaction vessel when F is a negative value, in addition to or instead of any of (a) to (c) above. [8] The Anammox process system further includes an anaerobic tank upstream of the reaction tank that does not supply oxygen, and the water to be treated is denitrified by denitrifying bacteria in the anaerobic tank to produce NO3 - The system according to any one of [5] to [7], wherein the N concentration is reduced before being introduced into the reactor. [9] An Anammox process system for performing nitrogen removal treatment on water to be treated by the method described in any one of [1] to [4], A reaction vessel having an inlet and an outlet, A blower configured to aerate the water remaining in the reaction vessel, Ammonia-oxidizing bacteria and Anammox bacteria contained in the reaction vessel, A pH measuring device configured to measure the pH inside a reaction vessel, NH4 of the water to be treated before being introduced into the reaction tank + an ammonia concentration measuring device configured to measure the -N concentration (A), NH4 in the treated water after nitrogen removal treatment in the aforementioned reaction tank + - An ammonia concentration measuring device configured to measure N concentration (C) It includes, and further, An anaerobic tank that does not supply oxygen is included upstream of the reaction tank, and the water to be treated is denitrified by denitrifying bacteria in the anaerobic tank to remove NO3 - -N is introduced into the reaction vessel after its concentration has been reduced. system. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 shows experimental results demonstrating that nitrogen can be stably removed from water containing ammonia nitrogen at low concentrations using a single-tank Anammox process, reducing the concentration to even lower levels. [Figure 2] Figure 2 shows an overview of a single-tank anammox process system according to one embodiment. [Figure 3] Figure 3 shows an overview of a single-tank anammox process system according to another embodiment. [Modes for carrying out the invention]

[0014] In this disclosure, unless otherwise clearly inconsistent with the context, raw water before nitrogen removal treatment by the Anammox process is referred to as treated water, and water after nitrogen removal treatment by the Anammox process is referred to as treated water. Treated water may be, for example, industrial wastewater, and may also be water from which ammonia nitrogen has been removed to a relatively low concentration range by conventional nitrogen removal treatment.

[0015] Embodiments of this disclosure describe ammonia nitrogen (NH4 + -N) A method for removing nitrogen from ammonia-containing water to be treated, wherein the N concentration is 100 mg / L or less, and an Anammox process system, i.e., a single-tank Anammox process system, is used, which includes a reaction tank containing ammonia-oxidizing bacteria (AOB) and Anammox bacteria (AXB) and aerating, and the water to be treated is introduced into the reaction tank to remove nitrogen from the water to be treated, wherein the pH in the reaction tank is 7.0 to 9.0 and the NH4 concentration is below 10.0 mg / L. + This provides a method for obtaining treated water with an N concentration.

[0016] The anammox process generally refers to the process of ammonia (NH4) + ) and nitrite (NO2 - This refers to nitrogen removal treatment using Anammox bacteria, which react with ) to convert into nitrogen gas (N2), and as is clear from the context, this disclosure specifically refers to ammonia-oxidizing bacteria (NH4 + NO2 -PNA (Partial nitritation-anammox) refers to the use of ammonia-oxidizing bacteria in combination with anammox bacteria. PNA-type anammox processes, more typically two-tank PNA-type anammox processes, have been conventionally performed, and ammonia-oxidizing bacteria and anammox bacteria are available to those skilled in the art. In this disclosure, "single-tank" with respect to an anammox process or system means that the treatment with AOB and the treatment with AXB are carried out in the same reaction vessel (if they are carried out in separate vessels, it is called a two-tank system), and the possibility that the system may include other vessels (e.g., anaerobic vessels described later) is not ruled out. These different types of bacteria are preferably housed in the reaction vessel separately or mixed and attached to a carrier. As will be understood by those skilled in the art, attachment to a carrier can prevent these useful bacteria themselves from flowing out of the reaction vessel. The carrier may be, for example, a water-insoluble natural polymer or a synthetic polymer such as polyvinyl alcohol (PVA). For example, it is preferable to include PVA carriers with AOB bacteria attached and PVA carriers with AXB bacteria attached in such quantities that they constitute 5-40% by volume or 7-30% by volume of water in the reaction vessel, respectively.

[0017] The reaction vessel has an inlet from which the water to be treated can be introduced into the reaction vessel. Preferably, the inlet is accompanied by a valve configured to adjust the inflow rate of the water to be treated into the reaction vessel. The water to be treated introduced into the reaction vessel undergoes nitrogen removal treatment there by the activity of AOB and AXB, more specifically, it undergoes treatment to reduce the ammonia nitrogen concentration. The water that has undergone treatment in the reaction vessel, i.e., the treated water, can be discharged out of the reaction vessel through an outlet of the reaction vessel. The Anammox process in this embodiment is preferably carried out in a continuous manner in which the inflow and outflow of liquid into the reaction vessel occur continuously, but it can also be carried out in a batch manner.

[0018] Specific methods and means for aerating the water stagnating in the tank are known to those skilled in the art; for example, aeration can be performed by placing a diffuser plate connected to a blower at the bottom of the tank. It is understood to those skilled in the art that the dissolved oxygen concentration can be increased by increasing the amount of aeration in the reaction tank. When the amount of aeration is relatively increased, the activity of AOB increases and the NH4 in the treated water increases. + -N concentration can be reduced, but undesirable NOB activity may also increase. Therefore, relatively reducing the aeration rate is necessary to suppress NOB and, consequently, excess NO3 in the treated water. - This can serve as a control mechanism to suppress concentration and optimize the single-tank anammox process.

[0019] This embodiment describes ammonia nitrogen (NH4) in a relatively low concentration range of 100 mg / L or less. + The present invention is characterized by performing nitrogen removal treatment using a single-tank anammox process with water to be treated that contains NH4 (-N). Embodiments of this disclosure provide a method and means for stably performing nitrogen removal treatment on water to be treated that contains ammonia in such a low concentration range. + -N concentration may be, for example, less than 100 mg / L, 95 mg / L or less, 90 mg / L or less, 70 mg / L or less, or 50 mg / L or less. NH4 in the treated water. + -The N concentration may be, for example, 1 mg / L or more, greater than 1 mg / L, 5 mg / L or more, 10 mg / L or more, or greater than 10 mg / L, and could be, for example, 12 mg / L or more.

[0020] In the nitrogen removal treatment of this embodiment, the pH in the reaction vessel is controlled within the range of 7.0 to 9.0. A pH of 8.5 or lower is preferable for better AXB activity. Selecting specific methods and means for changing the pH is within the scope of the skill of those skilled in the art. For example, the pH can be lowered or raised by adding acidic chemicals such as hydrochloric acid or alkaline chemicals such as sodium hydroxide contained in a chemical tank to the reaction vessel. In this disclosure, the term "ammonia" refers to NH4 unless contrary to the context. +In other words, it refers to ammonium ions. NH3 in its unionized state is specifically called FA (free ammonia). Increasing the pH of the reaction vessel increases the proportion of FA, but FA is NH4 + It was found that the single-tank Anammox process tends to have stronger activity in suppressing NOB than the other method. Therefore, relatively increasing the pH suppresses NOB and, consequently, excess NO3 in the treated water. - This can serve as a control mechanism to suppress concentration and optimize the single-tank anammox process.

[0021] In one embodiment, NH4 of the treated water after nitrogen removal treatment in the reaction vessel + -N concentration can be below 10.0 mg / L. NH4 in treated water. + -N concentration can be controlled by adjusting the aeration rate in the reaction vessel and / or the inflow rate of the water to be treated introduced into the reaction vessel, as described above. Since this is before treatment, NH4 + -By relatively increasing the inflow rate of the treated water, whose N concentration has not yet decreased, the equilibrium in the reaction vessel shifts, and the NH4 in the treated water... + -N concentration can be increased. NH4 below 100 mg / L + For water with a concentration of -N, a single-tank Anammox process is used to obtain NH4 + It was found that treated water with a -N concentration below 10.0 mg / L could be obtained, and that nitrogen can be stably removed from treated water in such a relatively low ammonia concentration range. + -The N concentration may be, for example, 9.8 mg / L or less or 9.5 mg / L or less, and it is also possible to set it to 5.0 mg / L or less. NH4 in treated water + -N concentration is typically 1.0 mg / L or higher. NH4 in treated water. + -N concentration is preferably measured after the treated water is discharged from the reaction vessel via the outlet. However, since a large amount of treated water remains in the reaction vessel compared to the incoming treated water and becomes substantially homogenized, the NH4 concentration of the treated water is less likely to be measured. + -It is also possible to measure the nitrogen concentration inside the reaction vessel.

[0022] In one embodiment, to ensure more stable nitrogen removal, the nitrogen load of the reaction vessel is set to 0.05-1.0 kg-N / m³ 3 It is preferable to maintain it at / day. Nitrogen load is NH4 + Those skilled in the art will understand that this can be controlled by adjusting the inflow rate (or inflow velocity) and / or the hydraulic retention time (HRT). The nitrogen load is 0.7 kg-N / m³. 3 / day or less, 0.5kg-N / m 3 / day or less, 0.5kg-N / m 3 Less than / day, or 0.48 kg-N / m 3 It may be less than / day. The nitrogen load should be 0.1 kg-N / m³. 3 / day or more or 0.2 kg-N / m 3 It may be more than / day. In addition or alternatively, the water temperature of the reaction vessel is preferably 20 to 40°C, and more preferably 25 to 35°C. In addition or alternatively, the dissolved oxygen concentration of the reaction vessel is preferably controlled to 0.1 to 3.0 mg / L, and may be 0.5 to 2.5 mg / L. HRT may be, for example, 1 to 24 hours.

[0023] Figure 1 shows an example of the results of nitrogen removal treatment of treated water using a single-tank anammox process according to an embodiment of the present disclosure. The horizontal axis represents the number of days elapsed during continuous treatment, and the vertical axis represents the concentration of ammonia nitrogen. Inf. (white circles) represent the inflow water into the reaction tank, i.e., the treated water, and Eff. (black circles) represent the discharged water, i.e., the treated water. In this example, the treated water has a concentration of 40 mg / L of NH4. + The synthetic wastewater had a nitrogen concentration, and a continuous nitrogen removal treatment method was performed by passing it through a reaction tank. The reaction tank was filled so that PVA carriers coated with AOB contained in activated sludge and PVA carriers coated with AXB contained in Anammox accumulated sludge each accounted for 10% of the volume of water in the tank. The water temperature was 30°C, pH = 8.0 ± 0.2, HRT was 2h, and the nitrogen load was 0.48 kg-N / m³. 3The result was / d. The dissolved oxygen concentration in the reaction vessel was controlled within the range of 0.1 to 3.0 mg / L. As illustrated in the figure, stable treated water quality was obtained. In this example, the NH4 of the treated water + -N concentrations ranged from 3.3 to 9.7 mg / L. Thus, using the single-tank Anammox process, the treated water containing ammonia in the low concentration range was further reduced to NH4. + It was revealed that nitrogen can be removed to a level below -N 10.0 mg / L.

[0024] In treated water with high ammonia nitrogen concentrations, such as typical sewage sludge filtrate, ammonia nitrogen accounts for the majority of the nitrogen components, making NO3 a minor component. - Without considering other factors, the ammoniacal nitrogen concentration can be treated as an approximation of the total nitrogen concentration. However, the inventors recognized that when attempting to remove nitrogen from water that already has a low nitrogen concentration to an even lower level, the presence of nitrate nitrogen in the water becomes a significant factor. The Anammox reactor is not suitable for removing nitrate nitrogen. The presence of nitrate nitrogen in the water to be treated hinders the thoroughness of nitrogen removal by the single-tank Anammox process and can also be a barrier or complicating factor in attempts to optimize the single-tank Anammox process from a chemical and analytical standpoint. For example, NH4 in the water to be treated + -N concentration is 500 mg / L, and NO3 is produced during the ammonia removal reaction and discharged into the treated water. - -N concentration is around several tens of mg / L, and separately, the raw water originally contains about 2 mg / L of nitrate (NO3 - Assuming that it contains NO3 (-N) and that it is also released as is, the NO3 in the treated water - - The error in the N concentration is less than 5%. However, for example, NH4 + -Considering nitrogen removal treatment of ammonia-low content treated water with a N concentration of 40 mg / L, the nitrate (NO3) originally present in the raw water at a concentration of 2 mg / L - -N) represents such a large portion of the nitrogen in the treated water that it can no longer be considered a mere error.

[0025] In embodiments of this disclosure, a single-tank anammox process system preferably includes an anaerobic tank upstream of the reaction tank where the anammox reaction occurs, which is not supplied with oxygen. An anaerobic tank is a tank that operates under conditions without oxygen supply, and can also be called an oxygen-free tank. When the water to be treated is introduced into the anaerobic tank, nitrate (and nitrite) in the water can be removed by the action of denitrifying bacteria under anaerobic conditions, as is known to those skilled in the art, and more specifically, it can be reduced to nitrogen molecules. Nitrate is not the only substance that can be removed in the anaerobic tank. The water to be treated often contains organic matter, including nitrogen-containing organic compounds, which may interfere with the anammox process, and the anaerobic tank is preferable because it can also remove these organic substances. In this embodiment, the water to be treated is introduced into this anaerobic tank and NO3 is released into the anaerobic tank. - -N concentration is reduced before being sent to the reaction vessel and introduced. This configuration allows for more precise nitrogen removal treatment of low-concentration ammonia-containing water to be treated using a single-tank anammox process, and facilitates monitoring and control of the anammox process.

[0026] In a preferred embodiment of the method for removing nitrogen from the water to be treated as described above, the Anammox process system removes NH4 from the water to be treated before it is introduced into the reaction vessel. + -N concentration (A) and NO3 - -Means for measuring the N concentration (B), and NH4 in the treated water after nitrogen removal treatment in the reaction vessel. + -N concentration (C) and NO3 ― - The method includes means for measuring the N concentration (D). This method is expressed by the following formula: F = α(AC) - (DB) When the control value F calculated based on is a negative value, the dissolved oxygen concentration in the reaction vessel is reduced, NH4 + Further features may include controlling one or more of the following: increasing the -N concentration and increasing the pH, where α is a value in the range of 0.07 to 0.15. α may also be 0.09 to 0.13 or 0.10 to 0.12, and is particularly preferably 0.11.

[0027] The ideal equation for the anammox reaction is as follows. 1 NH4 + + 1.32 NO2 - + 0.066 HCO3 - + 0.13 H + → 1.02 N2+ 0.26 NO3 - + 0.066 CH2O 0.5 N 0.15 + 2.03 H2O That is, ideally, a total of 2.32 moles of nitrogen, which is the combination of 1 mole of ammonia and 1.32 moles of nitrite nitrified from 1.32 moles of ammonia by AOB, is converted, and most of it is removed as nitrogen gas, but it can be understood that 0.26 moles of nitric acid is produced as a by-product. α corresponds to the production ratio of nitric acid to the amount of ammonia consumed, and is 0.112 based on the above ideal equation.

[0028] For example, the above control procedure may be performed when F is a negative value and the absolute value thereof exceeds a predetermined threshold. The lower the threshold is set, the stricter the control of the single-tank anammox process becomes. Although it depends on the ammonia content of the water to be treated and the measurement unit, for example NH4 + -N concentration and NO3 - When the -N concentration is measured in mg / L units, the threshold may be a value between 0.1 and 10.0, and may also be a value between 0.1 and 5.0.

[0029] NH4 + -N concentration and NO3 - Means for measuring -N concentration are respectively known to those skilled in the art for NH4 + -N concentration measuring device and NO3 --N concentration measuring devices (these are also called ammonia concentration measuring devices and nitrate concentration measuring devices, respectively), including cases where the ammonia concentration measuring device and the nitrate concentration measuring device are provided as a single device, as well as cases where the ammonia concentration measuring device and the nitrate concentration measuring device are provided as separate devices. The means for measuring A and the means for measuring B (or means for measuring both A and B) are preferably provided at the inlet of the reaction vessel. The means for measuring C and the means for measuring D (or means for measuring both C and D) are preferably provided at the outlet of the reaction vessel, but it is substantially possible to provide them inside the reaction vessel and perform the measurements there, for example, they can be installed in a position closer to the outlet than the inlet inside the reaction vessel.

[0030] To reduce the dissolved oxygen concentration, NH4 + Increasing the -N concentration and increasing the pH both have the effect of suppressing NOB, and therefore NO3 in treated water - -It has the effect of suppressing an excessive rise in N concentration and controls the optimization of the single-tank anammox process. By using the value of F, which takes into account the nitrate concentration that may originally be present in the treated water, as an indicator, the control accuracy of nitrogen removal treatment of treated water containing relatively low concentrations of ammonia in a single-tank anammox process can be significantly improved, and a stable treatment achievement can be obtained. This embodiment is even more accurate and effective when combined with the anaerobic tank described above. However, in embodiments including an anaerobic tank, since nitrate is sufficiently removed in the anaerobic tank and the impact on anammox process monitoring is small, it is possible to omit the measurement of nitrate nitrogen concentration (B) in the treated water, and in this case, the following formula can be used instead of the F value: F'=α(AC)―(D) It is also possible to perform the control described herein based on the F' value calculated based on the above.

[0031] In some respects, this disclosure provides an Anammox process system for performing nitrogen removal treatment on water to be treated by the methods described above, particularly the methods of embodiments that use the F value as a control indicator. Since this system is configured to perform the above methods, it should be understood that the matters described herein regarding embodiments of the methods can be incorporated as system-specific features, and conversely, the matters described regarding embodiments of the systems can be incorporated as method-specific features.

[0032] Referring to Figure 2, the Anammox process system 100 of this embodiment comprises a reaction tank 10, which has an inlet 11 into which water to be treated Inf. is introduced and an outlet 12 into which treated water Eff., which has undergone nitrogen removal treatment, is discharged. The system 100 includes a blower 20 configured to aerate the water remaining in the reaction tank 10. In this example, oxygen-containing gas (e.g., air) from the blower 20 is sent to an exhaust section 21, which is a diffuser plate located at the bottom of the reaction tank 10, and released into the water, supplying oxygen to the microorganisms in the reaction tank 10. Ammonia-oxidizing bacteria and Anammox bacteria are contained in the reaction tank 10 so as to be in contact with the introduced water to be treated. In this example, a carrier 13 to which ammonia-oxidizing bacteria (e.g., sludge containing them) is attached and a carrier 14 to which Anammox bacteria (e.g., sludge containing them) is attached are contained in the reaction tank 10. The reaction vessel 10 may be equipped with an alkaline chemical supply device 15 and an acidic chemical supply device 16 for adjusting the pH of the water in the reaction vessel (not shown). The reaction vessel 10 may also be equipped with a stirrer for stirring the water in the reaction vessel (not shown).

[0033] At the inlet 11 of the reaction tank, NH4 of the water to be treated before it is introduced into the reaction tank 10 + -A first ammonia concentration measuring device 31 configured to measure the NO3 concentration (A) of the water to be treated, and NO3 - A first nitrate concentration measuring device 32 is provided, configured to measure the -N concentration (B). Meanwhile, near the outlet 12 of the reaction tank 10 in the figure, NH4 in the treated water after nitrogen removal treatment in the reaction tank 10 is provided.+ - A second ammonia concentration measuring device 33 and NO3 configured to measure N concentration (C) ― A second nitrate concentration measuring device 34 is provided, configured to measure the -N concentration (D). Since a large amount of treated water remains in the reaction vessel compared to the incoming treated water and is substantially homogenized, the second measuring devices 33 and 34 are installed inside the reaction vessel 10 instead of being installed at the outlet 12 in this example. Devices that can switch between measuring ammonia concentration and nitrate concentration are commercially available, and therefore, references to the first ammonia concentration measuring device and the first nitrate concentration measuring device also include cases where both are provided as a single device. The same applies to the second measuring devices 33 and 34. The reaction vessel 10 is equipped with a pH measuring device 35 configured to measure the pH of the water in the reaction vessel. The reaction vessel 10 further has an oxygen concentration measuring device 36 configured to measure the dissolved oxygen concentration of the water in the reaction vessel.

[0034] The measurement data obtained by the measuring devices 31-36 are configured to be transmitted to the system's control device 40. The control device 40, which includes a computer processor, is further configured to send command signals to the blower 20. The control device 40 is also configured, although not explicitly shown in the figure, to send command signals to the valve 11a attached to the inlet 11 in order to adjust the inflow rate of the water to be treated into the reaction tank 10. The transmission of data or signals may be done through wiring connecting the devices or wirelessly. The control device 40 calculates the control value F described above based on the measurement data obtained from the measuring devices 31-34. When F is a negative value, more specifically, for example, when F is a negative value and its absolute value exceeds a predetermined threshold, the control device 40 either (a) sends a command to the blower 20 to reduce the amount of aeration into the reaction tank 10, (b) sends a command to the valve 11a to increase the inflow rate of the water to be treated into the reaction tank 10, or (c) does both. In addition to or instead of any of (a) to (c), the control device 40 may be configured to (d) increase the pH inside the reaction vessel by sending a command to an alkaline chemical supply device 15 (not shown) to add an alkaline chemical into the reaction vessel 10.

[0035] Figure 2 shows an automated system in which the control device 40 calculates the control value F and automatically performs one of the controls (A) to (D). However, it is also possible to manually control one of the controls (A) to (D) without using the control device.

[0036] The Anammox process system 101 shown in Figure 3 has a configuration common to the system 100 shown in Figure 2, except that it is equipped with an anaerobic tank 50 upstream of the reaction tank 10. Oxygen is not supplied to the anaerobic tank 50, and a carrier 51 to which denitrifying bacteria (and sludge containing them) are attached is contained within the tank. The anaerobic tank 50 is connected to the reaction tank 10 via piping 52 (which may include one or more of the following: valves, pumps, nitrate concentration measuring devices, flow meters, etc., as needed). This piping 52 may be connected to the inlet 11 of the reaction tank 10, or it may be integrated with or identical to the inlet 11. The water to be treated (Inf.) is first introduced into the anaerobic tank 50, where it remains and undergoes reduction of nitrate nitrogen and organic matter by anaerobic bacteria, and then it is sent to the reaction tank 10. The system 101 may also be equipped with a liquid transfer pipe 53 and an associated liquid transfer device 54 (not shown) for returning water from the reaction tank 10 to the anaerobic tank 50. The control device 40 can send a command to the liquid transfer device 54 to transfer liquid from the reaction tank 10 to the anaerobic tank 50 when the measured value of the nitrate concentration measuring device 34 exceeds a predetermined threshold, or when the absolute value of the calculated control value F or F' exceeds a predetermined threshold.

Claims

1. Ammonia nitrogen (NH ４ ＋ -N) A method for removing nitrogen from ammonia-containing water to be treated, wherein the concentration is 100 mg / L or less, An Anammox process system is used, which includes a reaction vessel containing ammonia-oxidizing bacteria and Anammox bacteria and aerating the reaction vessel, and the water to be treated is introduced into the reaction vessel to perform nitrogen removal treatment on the water to be treated. Here, the pH inside the reaction vessel is set to 7.0 to 9.

0. NH below 10.0 mg / L ４ ＋ A method for obtaining treated water with -N concentration.

2. The nitrogen load of the reaction vessel is set to 0.05 to 1.0 kg-N / m ３ Maintain / day, The water temperature in the reaction vessel is set to 20 to 40°C. The method according to claim 1, wherein the dissolved oxygen concentration in the reaction vessel is controlled to 0.1 to 3.0 mg / L.

3. The aforementioned Anammox process system is The NH of the water to be treated before being introduced into the reaction tank ４ ＋ -N concentration (A) and NO ３ － -N concentration (B) measuring means; After nitrogen removal treatment of the treated water in the aforementioned reaction tank, NH ４ ＋ -N concentration (C) and NO ３ ― - Means for measuring the N concentration (D) The method includes the following formula: F=α(A-C)-(D-B) When the control value F calculated based on is a negative value, the dissolved oxygen concentration in the reaction vessel is reduced, NH ４ ＋ The method according to claim 1, wherein one or more of the following controls are performed: increasing the -N concentration and increasing the pH, where α is a value in the range of 0.07 to 0.

15.

4. The Anammox process system further includes an anaerobic tank upstream of the reaction tank that does not supply oxygen, and the water to be treated is subjected to NO by denitrifying bacteria in the anaerobic tank. ３ － The method according to any one of claims 1 to 3, wherein the -N concentration is reduced before being introduced into the reaction vessel.

5. An Anammox process system for performing nitrogen removal treatment on water to be treated by the method described in claim 3, A reaction vessel having an inlet and an outlet, A blower configured to aerate the water remaining in the reaction vessel, Ammonia-oxidizing bacteria and Anammox bacteria contained in the reaction vessel, A pH measuring device configured to measure the pH inside a reaction vessel NH of the water to be treated before being introduced into the reaction tank ４ ＋ -N concentration (A) and NO ３ － A first ammonia concentration measuring device and a first nitrate concentration measuring device configured to measure the -N concentration (B), After nitrogen removal treatment of the treated water in the aforementioned reaction tank, NH ４ ＋ -N concentration (C) and NO ３ ― A second ammonia concentration measuring device and a second nitrate concentration measuring device configured to measure the -N concentration (D), respectively. A system that includes this.

6. The system according to claim 5, further comprising a control device, the control device receiving measurement data from the first ammonia concentration measuring device and the first nitrate concentration measuring device and the second ammonia concentration measuring device and the second nitrate concentration measuring device to calculate the control value F, and when F is a negative value, the control device is configured to (a) send a command to the blower to reduce the aeration rate, (b) send a command to a valve attached to the inlet to increase the inflow rate of the water to be treated into the reaction tank, or (c) do both.

7. The system according to claim 6, wherein the reaction vessel is equipped with an alkaline chemical supply device for adjusting the pH inside the reaction vessel, and the control device is configured to raise the pH inside the reaction vessel by sending a command to the alkaline chemical supply device to add an alkaline chemical to the reaction vessel when F is a negative value, in addition to or instead of any of (a) to (c) above.

8. The Anammox process system further includes an anaerobic tank upstream of the reaction tank that does not supply oxygen, and the water to be treated is subjected to NO by denitrifying bacteria in the anaerobic tank. ３ － The system according to any one of claims 5 to 7, wherein the N concentration is reduced before being introduced into the reaction vessel.

9. An Anammox process system for performing nitrogen removal treatment on water to be treated by the method of claim 1 or 2, A reaction vessel having an inlet and an outlet, A blower configured to aerate the water remaining in the reaction vessel, Ammonia-oxidizing bacteria and Anammox bacteria contained in the reaction vessel, A pH measuring device configured to measure the pH inside a reaction vessel NH of the water to be treated before being introduced into the reaction tank ４ ＋ - An ammonia concentration measuring device configured to measure the concentration of N (A), After nitrogen removal treatment of the treated water in the aforementioned reaction tank, NH ４ ＋ - An ammonia concentration measuring device configured to measure the N concentration (C) and It includes, and further, An anaerobic tank that does not supply oxygen is included upstream of the reaction tank, and the water to be treated is denitrified by denitrifying bacteria in the anaerobic tank to remove NO. ３ － -N concentration is reduced and then introduced into the reaction vessel. system.

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