Method and apparatus for treating wastewater

Abstract

Methods and apparatus for treating wastewater are provided. The method comprises a step (S10) of producing primary treated water by passing wastewater containing ammonia nitrogen (NH4-N) through a first membrane coupled bioreactor, and a step (S20) of producing secondary treated water by passing the primary treated water through a second membrane coupled bioreactor, a partial region of the first membrane coupled bioreactor operates under aerobic conditions and other regions of the first membrane coupled bioreactor operate under anoxic conditions, and the second membrane coupled bioreactor operates under anoxic conditions.

Description

Technical Field

[0001] This application is based on and claims the benefit of priority under 35 USC §119 from Korean Patent Application No. 10-2023-0097035 filed on Jul. 25, 2023 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to a method and an apparatus for treating wastewater. More particularly, the present disclosure relates to a method and an apparatus for treating wastewater, by which the energy and carbon source used in wastewater treatment can be minimized, and final treated water with a low total nitrogen content can be obtained. Background Art

[0003] In the art, ammonia nitrogen (NH4-N) in sewage is oxidized to nitrite nitrogen (NO2-N) and nitrate nitrogen (NO3-N) under aerobic conditions by nitrification as shown in reaction scheme 1, which is then reduced to nitrogen gas (N2) under anoxic conditions without oxygen by the denitrification process as shown in reaction scheme 2, resulting in the removal of ammonia nitrogen from the water system. This system requires excessive aeration energy (4.57kg-O2 / kg-NH4-N) and denitrification carbon source (3-6kg-COD / kg-NO3-N), and therefore can be called an energy-consuming nitrogen treatment method.

[0004] Reaction Scheme 1

[0005] Nitrification: NH4 + →NO2 - →NO3 - (Oxygen demand: 4.57kg-O2 / kg-NH4-N)

[0006] Reaction Scheme 2

[0007] Denitrification: NO3 - →NO2 - →N2 (Organic carbon demand: 4.8kg-COD / kg-NO3-N) Summary of the invention

[0008] Technical issues

[0009] A method for treating wastewater is provided, by which the energy and carbon source used in the wastewater treatment can be minimized and final treated water with a low total nitrogen content can be obtained.

[0010] Provided is an apparatus for treating wastewater, by which energy and carbon sources used in wastewater treatment can be minimized and final treated water with a low total nitrogen content can be obtained.

[0011] Solution to the problem

[0012] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the embodiments presented in the disclosure.

[0013] According to aspects of the present disclosure, a method for treating wastewater comprises:

[0014] A step (S10) of producing primary treated water by passing the wastewater containing ammonia nitrogen (NH4-N) through a first membrane coupled bioreactor;

[0015] Part of the area of ​​the first membrane-coupled bioreactor is operated under aerobic conditions, and the other area of ​​the first membrane-coupled bioreactor is operated under anoxic conditions.

[0016] In the first membrane coupled bioreactor, oxygen-containing air may be supplied into the membrane, and the area outside the membrane may be operated under anoxic conditions.

[0017] The method may further include a step (S20) of producing secondary treated water by passing the primary treated water through a second membrane coupled bioreactor, wherein the second membrane coupled bioreactor may be operated under anoxic conditions.

[0018] In the second membrane coupled bioreactor, methane gas may be supplied into the membrane, and the area outside the membrane may be operated under anoxic conditions.

[0019] The step (S10) may include a step (S10-1) of converting ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of ammonia nitrogen (NH4-N) under aerobic conditions generated in the area outside the membrane which is the interior of the first membrane coupled bioreactor, and a step (S10-2) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) and nitrate nitrogen (NO3-N) under anoxic conditions in the first membrane coupled bioreactor.

[0020] The step (S10-1) may involve converting ammonia nitrogen (NH4-N) only into nitrite nitrogen (NO2-N), as shown in reaction scheme 3, and in this process, aeration energy may be saved:

[0021] Reaction Scheme 3

[0022] Partial nitrification: NH4 + →NO2 - (Oxygen demand: 1.9kg-O2 / kg-NH4-N).

[0023] The step (S10-2) may include an anaerobic ammonium oxidation reaction, in which ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) react with each other and are oxidized into nitrogen (N2) and nitrate nitrogen (NO3-N), as shown in Reaction Scheme 4, and in this process, compared with existing biological treatment methods, the consumed carbon source can be reduced:

[0024] Reaction Scheme 4

[0025] Anaerobic ammonium oxidation: NH4 + +NO2 - →N2 (organic carbon demand: 0kg-COD / kg-NO3-N).

[0026] The chemically equivalent overall reaction scheme of the step (S10-1) and the step (S10-2) can be shown in Reaction Scheme 5:

[0027] Reaction Scheme 5

[0028] Total chemical equivalent reaction: 1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O

[0029] In the step (S10-1), the first membrane coupled bioreactor has a hydraulic retention time of within 4 hours, and the step (S10-1) can be carried out in a state where the average oxygen partial pressure in the oxygen-containing gas inside the membrane installed in the first membrane coupled bioreactor is maintained in the range of about 17 kPa to about 23.2 kPa.

[0030] In the step (S10-1), the average oxygen partial pressure in the oxygen-containing gas can be controlled in combination with the oxygen utilization efficiency and the oxygen transfer capacity, and the dissolved oxygen concentration C in the liquid phase in equilibrium with the gas phase in the membrane can be calculated by the oxygen transfer model based on differential pressure shown in Equation 1. L To calculate the oxygen transfer capacity:

[0031] Equation 1

[0032]

[0033] Where, in equation 1,

[0034] J is the oxygen transfer capacity per second (mol / m 2 ·sec), K is the mass transfer coefficient (m 2 / sec), P 入 is the oxygen partial pressure at the inlet (Pa), P 出 is the oxygen partial pressure at the outlet (Pa), H is the Henry's law constant (Pa·m 2 / mol), and C L is the concentration of oxygen in the liquid (mol / m 3 ).

[0035] The step (S20) may include a step (S20-1) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anaerobic conditions generated in an area outside the membrane by using methane gas injected into the membrane, which is inside the second membrane coupled bioreactor, and a step (S20-2) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) under anaerobic conditions in the second membrane coupled bioreactor.

[0036] The step (S20-1) may include a DAMO reaction for converting methane gas into methanol, as shown in Reaction Scheme 6, and a reaction for converting nitrate nitrogen (NO3-N) only into nitrite nitrogen (NO2-N) by using methanol as a carbon source, as shown in Reaction Scheme 7:

[0037] Reaction Scheme 6

[0038] Methanolation: CH4 → CH3OH

[0039] Reaction Scheme 7

[0040] Partial denitrification: NO3 - →NO2 - (Organic carbon demand: 1.9kg-COD / kg-NO3-N).

[0041] The step (S20-2) may include an anaerobic ammonium oxidation reaction, in which the residual ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) react with each other and are oxidized into nitrogen (N2) and nitrate nitrogen (NO3-N), as shown in reaction scheme 8, and in this process, compared with the existing biological treatment method, the consumed carbon source can be reduced:

[0042] Reaction Scheme 8

[0043] Anaerobic ammonium oxidation: NH4 + +NO2 - →N2 (organic carbon demand: 0kg-COD / kg-NO3-N).

[0044] The chemically equivalent overall reaction scheme of process S20-1 and process S20-2 can be shown in reaction scheme 9:

[0045] Reaction Scheme 9

[0046] Total chemical equivalent reaction: 1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O.

[0047] According to another aspect of the present disclosure, a method for treating wastewater comprises:

[0048] The step (S100) of passing the wastewater containing ammonia nitrogen (NH4-N) through an activated sludge tank to produce primary treated water,

[0049] The step (S200) of passing the primary treated water through a first settling tank to produce secondary treated water and first sludge,

[0050] by passing the secondary treated water through a first two-stage membrane coupled bioreactor to produce tertiary treated water (S300),

[0051] By passing the tertiary treated water through a second settling tank to produce quaternary treated water and secondary sludge (S400),

[0052] by passing the second sludge through an anaerobic digester to produce digested sludge (S500),

[0053] By passing the digested sludge through a sludge dewatering tank to produce a first sludge water and a third sludge step (S600),

[0054] a step of producing second sludge water by passing the first sludge water through a second two-stage membrane coupled bioreactor (S700), and

[0055] A step (S800) of mixing the second sludge water with the primary treated water supplied to the step (S200).

[0056] The step (S300) may include, as a step performed in a first membrane coupled bioreactor, a step (S310) of converting ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of ammonia nitrogen (NH4-N) under aerobic conditions generated in a region outside the membrane that is inside the first membrane coupled bioreactor, and a step (S320) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) and nitrate nitrogen (NO3-N) under anoxic conditions in the first membrane coupled bioreactor, and may include, as a step performed in a second membrane coupled bioreactor, a step (S330) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions in a biofilm formed outside the membrane in the second membrane coupled bioreactor, and a step (S340) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) under anoxic conditions in the second membrane coupled bioreactor.

[0057] The step (S310) may be performed in a state in which an average oxygen partial pressure in the oxygen-containing gas inside the membrane installed in the first membrane coupled bioreactor is maintained in a range of about 17 kPa to about 23.2 kPa.

[0058] The step (S700) may include, as a step performed in a third membrane coupled bioreactor, a step (S710) of converting ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of ammonia nitrogen (NH4-N) under aerobic conditions generated in a region outside the membrane that is inside the third membrane coupled bioreactor, and a step (S720) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen and nitrate nitrogen (NO3-N) under anoxic conditions in the third membrane coupled bioreactor, and may include, as a step performed in a fourth membrane coupled bioreactor, a step (S730) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions generated in a region outside the membrane that is inside the fourth membrane coupled bioreactor, and a step (S740) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen under anoxic conditions in the fourth membrane coupled bioreactor.

[0059] The first sludge generated in the step (S200) may be supplied to the anaerobic digester in the step (S500).

[0060] A portion of the second sludge produced in the step (S400) may be returned to the first two-stage membrane coupled bioreactor in the step (S300).

[0061] According to another aspect of the present disclosure, a device for treating wastewater comprises

[0062] a first membrane coupled bioreactor configured to produce primary treated water by treating wastewater containing ammonia nitrogen (NH4-N), and

[0063] a second membrane coupled bioreactor configured to produce secondary treated water by further treating the primary treated water,

[0064] Wherein, the first membrane-coupled bioreactor is configured so that a partial area of ​​the first membrane-coupled bioreactor operates under aerobic conditions and other areas of the first membrane-coupled bioreactor operate under anoxic conditions, and the second membrane-coupled bioreactor is configured to operate under anoxic conditions.

[0065] The first membrane-coupled bioreactor can be configured to first convert the ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) under aerobic conditions by partial oxidation of the ammonia nitrogen (NH4-N), and secondly convert the ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) and nitrate nitrogen (NO3-N) under anoxic conditions.

[0066] The first membrane-coupled bioreactor may be configured such that an average oxygen partial pressure in the oxygen-containing gas inside the membrane installed therein is maintained in a range of about 17 kPa to about 23.2 kPa.

[0067] The second membrane coupled bioreactor can be configured to first convert nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anaerobic conditions, and secondly convert ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas (N2) under anaerobic conditions.

[0068] According to another aspect of the present disclosure, a device for treating wastewater comprises

[0069] An activated sludge tank configured to produce primary treated water by treating wastewater containing ammonia nitrogen (NH4-N) and having a chemical oxygen demand (COD),

[0070] a first settling tank configured to produce secondary treated water and first sludge by partially settling the primary treated water,

[0071] a first two-stage membrane-coupled bioreactor configured to produce tertiary treated water by further treating the secondary treated water,

[0072] a second settling tank configured to produce quaternary treated water and secondary sludge by partially settling the tertiary treated water,

[0073] an anaerobic digester configured to produce digested sludge by partially digesting the second sludge,

[0074] a sludge dewatering tank configured to produce first sludge water and third sludge by partially dewatering the digested sludge, and

[0075] The second two-stage membrane-coupled bioreactor is configured to produce second sludge water by further treating the first sludge water.

[0076] The apparatus may be configured to mix the second sludge water with wastewater supplied to the first settling tank.

[0077] The first two-stage membrane coupled bioreactor may include a first membrane coupled bioreactor and a second membrane coupled bioreactor connected in series with each other, the second two-stage membrane coupled bioreactor may include a third membrane coupled bioreactor and a fourth membrane coupled bioreactor connected in series with each other, each of the first membrane coupled bioreactor and the third membrane coupled bioreactor may be configured to first convert the ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) rather than nitrate nitrogen by partial oxidation of the ammonia nitrogen (NH4-N) under aerobic conditions generated in a region outside the membrane as the interior of each bioreactor (NO3-N), and secondly, converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen and nitrate nitrogen (NO3-N) under anaerobic conditions in each bioreactor, and each of the second membrane-coupled bioreactor and the fourth membrane-coupled bioreactor can be configured to first convert nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anaerobic conditions generated in an area outside the membrane which is the interior of each bioreactor, and secondly, converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) under anaerobic conditions in each bioreactor.

[0078] In the first membrane-coupled bioreactor, an average oxygen partial pressure in the oxygen-containing gas inside the membrane installed therein may be maintained in a range of about 17 kPa to about 23.2 kPa.

[0079] The apparatus may be configured such that the first sludge generated in the first settling tank is supplied to the anaerobic digestion tank.

[0080] The apparatus may be configured such that a portion of the second sludge produced in the second settling tank is returned to the first two-stage membrane-coupled bioreactor.

[0081] Advantageous Effects of the Invention

[0082] According to the method and apparatus for treating wastewater, according to the embodiments of the present disclosure, energy and carbon sources used in wastewater treatment can be minimized, and final treated water with a low total nitrogen content can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0084] Figure 1 is a schematic diagram of a method and apparatus for treating wastewater according to one embodiment;

[0085] Figure 2 is a view illustrating a mass transfer path through a membrane of a first membrane coupled bioreactor and in the vicinity of the membrane;

[0086] Figure 3 is a diagram illustrating mass transfer paths through a membrane of a first membrane-coupled bioreactor and near the membrane and reactions between substances;

[0087] Figure 4 It is explained by Figure 1 A diagram showing a membrane of a second membrane coupled bioreactor of the device and a mass transfer path near the membrane and reactions between substances;

[0088] Figure 5 is a schematic diagram of a method and apparatus for treating wastewater according to another embodiment;

[0089] Figure 6 is a graph showing simulation results showing that nitrite steadily accumulates in a bioreactor as a result of treating wastewater containing a high concentration (1,000 ppm) or more of ammonia nitrogen (NH4-N), such as landfill leachate or livestock wastewater;

[0090] Figure 7 is a graph showing simulation results showing that nitrite is unlikely to accumulate in a bioreactor as a result of treating wastewater containing ammonia nitrogen (NH4-N) at a low concentration (50 ppm or less), such as sewage; and

[0091] Figure 8 It is a diagram showing the effects of two control methods proposed for stably oxidizing NH 4 into NO 2 while suppressing the production of NO 3 when low-load NH 4 flows into the first membrane coupled bioreactor. DETAILED DESCRIPTION

[0092] Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein the same reference numerals refer to the same elements throughout the text. In this regard, embodiments of the present invention may have different forms and should not be construed as being limited to the descriptions listed herein. Therefore, embodiments are described below only by reference to the accompanying drawings to explain various aspects of this specification. As used herein, the term "and / or" includes any and all combinations of one or more related listed items. Statements such as "at least one of..." before an element list modify the entire element list, without modifying a single element in the list.

[0093] Hereinafter, a method of treating wastewater according to an embodiment of the present disclosure will be described in detail.

[0094] As used herein, "wastewater" refers to untreated wastewater (ie, raw water or influent water).

[0095] In addition, "treated water" as used herein refers to treated wastewater made smaller in amount than that of untreated wastewater by removing impurities in untreated wastewater at all stages.

[0096] In addition, "water to be treated" as used herein refers to water to be treated at a certain stage, and the water to be treated in each process has a different treatment rate.

[0097] Furthermore, the “first membrane coupled bioreactor” and the “third membrane coupled bioreactor” as used herein refer to a membrane aerated biofilm reactor (MABR).

[0098] Furthermore, as used herein, "a second membrane coupled bioreactor" and "a fourth membrane coupled bioreactor" refer to a membrane biomembrane reactor (MBfR).

[0099] Additionally, as used herein, "parts per million (ppm)" refers to mg / L (milligrams per liter).

[0100] In addition, in some embodiments, as used herein, "ammonia nitrogen (NH4-N)" refers to ammonium ions (NH4 + ) contained in nitrogen or ammonium ions themselves.

[0101] In addition, in some embodiments, as used herein, "nitrite nitrogen (NO2-N)" refers to nitrite ions (NO2 - ) contained in nitrogen or nitrite ions themselves.

[0102] In addition, in some embodiments, "nitrate nitrogen (NO3-N)" refers to nitrate ions (NO3 - ) contained in nitrogen or nitrate ions themselves.

[0103] In addition, as used herein, the "front end or front end portion" refers to a portion or end portion relatively located in the opposite direction to the wastewater flow direction, and the "rear end or rear end portion" refers to a portion or end portion relatively located in the positive direction relative to the wastewater flow direction.

[0104] Furthermore, as used herein, "film" and "membrane" have the same meaning.

[0105] According to an embodiment of the present disclosure, an apparatus and method for treating wastewater have been developed to improve the energy-consuming process represented by reaction schemes 1 and 2, which is a combination of: a partial nitritation process: the reaction shown in reaction scheme 3 is carried out under aerobic conditions to convert half of the ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N); and an anaerobic ammonia oxidation (ANAMMOX) process: the reaction shown in reaction scheme 4 is carried out to convert the remaining half of the ammonia nitrogen (NH4-N) and the nitrite nitrogen (NO2-N) produced by the partial nitritation process of ammonia nitrogen (NH4-N) into nitrogen (N2) through the reaction therebetween under anoxic conditions. In the partial nitritation process, ammonia nitrogen (NH4-N) is only partially oxidized to nitrite nitrogen (NO2-N), thereby saving up to 63% of oxygen consumption, and the denitrification process is not used, thereby removing nitrogen from the water system without an external carbon source supply.

[0106] Reaction Scheme 3

[0107] Partial nitrosation: NH4 + →NO2 - (Oxygen demand: 1.9kg-O2 / kg-NH4-N)

[0108] Reaction Scheme 4

[0109] Anaerobic ammonium oxidation: NH4 + +NO2 - →N2 (Organic carbon demand: 0kg-COD / kg-NO3-N)

[0110] Reaction Scheme 5

[0111] Total chemical equivalent reaction: 1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O

[0112] For the anaerobic ammonium oxidation reaction, nitrite oxidizing bacteria (NOB) must be inhibited so that the nitrite nitrogen (NO2-N) produced after the partial nitrite reaction is not oxidized to nitrate nitrogen (NO3-N). Such inhibition can easily occur under conditions where the incoming ammonia nitrogen concentration is high, and is therefore mainly applied to sewage / wastewater containing high concentrations of nitrogen, such as anaerobic digestion return water (see Figure 6 ). In contrast, the inventors of the present disclosure have found that it is difficult to suppress NOB when the incoming ammonia nitrogen (NH4-N) concentration is low (see Figure 7 ), and as a result of great efforts, a new method for inhibiting NOB activity even in such a case was found, thereby completing the present disclosure.

[0113] According to one embodiment of the present disclosure, the method for treating wastewater includes a step (S10) of producing primary treated water by passing wastewater containing ammonia nitrogen (NH4-N) through a first membrane coupled bioreactor; and a step (S20) of producing secondary treated water by passing the primary treated water through a second membrane coupled bioreactor.

[0114] The wastewater treated in process S10 may contain ammonia nitrogen (NH 4 —N) at a concentration of about 30 mg / L to about 50 mg / L.

[0115] Part of the first membrane coupled bioreactor may be operated under aerobic conditions, and other regions of the first membrane coupled bioreactor may be operated under anoxic conditions. In particular, step (S10) may include a step (S10-1) of converting ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) rather than nitrate nitrogen (NO3-N) by partial oxidation of ammonia nitrogen (NH4-N) under aerobic conditions, and a step (S10-2) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen and nitrate nitrogen (NO3-N) under anoxic conditions.

[0116] Furthermore, step (S10-1) may be performed in a state in which an average oxygen partial pressure inside the membrane installed in the first membrane coupled bioreactor is maintained in a range of about 17 kPa to about 23.2 kPa.

[0117] The oxygen-containing gas may be air or oxygen.

[0118] In step (S10-1), the average oxygen partial pressure in the oxygen-containing gas can be controlled by combining the oxygen utilization efficiency and the oxygen transfer capacity, and the dissolved oxygen concentration C in the liquid phase in equilibrium with the gas phase in the membrane is calculated by the differential pressure-based oxygen transfer model shown in Equation 1. L To calculate the oxygen transfer capacity:

[0119] Equation 1

[0120]

[0121] Where, in equation 1,

[0122] J is the oxygen transfer capacity per second (mol / m 2 ·sec), K is the mass transfer coefficient (m 2 / sec), P 入 is the oxygen partial pressure at the inlet (Pa), P 出 is the oxygen partial pressure at the outlet (Pa), H is the Henry's law constant (Pa·m 2 / mol), and C L is the concentration of oxygen in the liquid (mol / m 3 ).

[0123] The oxygen transfer capacity can be expressed by Equation 2.

[0124] Equation 2

[0125] Oxygen transfer capacity (mg O2 / L / hr) = K×a×(C * -C1)

[0126] In Equation 2, K is the oxygen transfer coefficient (cm / hr), a is the gas-liquid contact area per unit volume of membrane (cm 2 / cm 3 ), K×a is the volume oxygen transfer coefficient (1 / hr), C * is the dissolved oxygen concentration (mg / L) in the liquid phase in equilibrium with the gas phase in the membrane, and C1 is the dissolved oxygen concentration (mg / L) in the bulk liquid.

[0127] The oxygen-containing gas supplied to the membrane may be air, and the oxygen concentration in the air supplied to the inlet of the membrane may be 23% (= 230,000 mg / L), and the oxygen concentration in the liquid does not exceed about 8 mg / L, which is the maximum saturation concentration in water. Assuming that the oxygen concentration at the membrane outlet is 21%, according to Henry's law, the oxygen concentration in the liquid may be about 1 / 28,000 of the oxygen concentration supplied by the oxygen-containing gas, and the effect on the oxygen transfer capacity per second is insignificant.

[0128] Therefore, in Equation 1, when “p 入 / HC L " is replaced by "p 入 / H", and "p 出 / HC L " is replaced by "p 出 / H”, then equation 1 is simplified to equation 1' and equation 1".

[0129] Equation 1'

[0130]

[0131] Equation 1

[0132]

[0133] In equation 1",

[0134] M lm (p 入 ,p 出 ) refers to the logarithmic mean of the oxygen partial pressure at the inlet and the oxygen partial pressure at the outlet, which is called the average oxygen partial pressure in the oxygen-containing gas.

[0135] Therefore, the oxygen transfer capacity of the liquid supplied through the membrane can be controlled in combination with the pressure at the inlet and outlet of the membrane, as shown in Equation 1, Equation 1' and Equation 1".

[0136] The second membrane coupled bioreactor can be operated under anoxic conditions. In particular, step (S20) can include a step (S20-1) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions, and a step (S20-2) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) under anoxic conditions.

[0137] Step (S20-1) may include a DAMO reaction for converting methane gas into methanol, as shown in Reaction Scheme 6, and a reaction for converting nitrate nitrogen (NH4-N) only into nitrite nitrogen (NO2-N) by using methanol as a carbon source, as shown in Reaction Scheme 7:

[0138] Reaction Scheme 6

[0139] Methanolation: CH4 → CH3OH

[0140] Reaction Scheme 7

[0141] Partial denitrification: NO3 - →NO2 - (Organic carbon demand: 1.9kg-COD / kg-NO3-N)

[0142] Step (S20-2) may include an anaerobic ammonium oxidation reaction, in which ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) react with each other and are oxidized into nitrogen (N2) and nitrate nitrogen (NO3-N), as shown in Reaction Scheme 8, and in this process, the carbon source consumed can be reduced compared to existing biological treatment methods:

[0143] Reaction Scheme 8

[0144] Anaerobic ammonium oxidation: NH4 + +NO2 -→N2 (organic carbon demand: 0kg-COD / kg-NO3-N) The chemical equivalent overall reaction scheme of step (S20-1) and step (S20-2) is shown in reaction scheme 9:

[0145] Reaction Scheme 9

[0146] Total chemical equivalent reaction: 1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O

[0147] According to another embodiment of the present disclosure, an apparatus and method for treating wastewater include a step (S100) of passing wastewater containing ammonia nitrogen (NH4-N) through an activated sludge tank to produce primary treated water, a step (S200) of passing the primary treated water through a first settling tank to produce secondary treated water and a first sludge, a step (S300) of passing the secondary treated water through a first two-stage membrane coupled bioreactor to produce tertiary treated water, a step (S400) of passing the tertiary treated water through a second settling tank to produce quaternary treated water and a second sludge, a step (S500) of passing the second sludge through an anaerobic digester to produce digested sludge, a step (S600) of passing the digested sludge through a sludge dewatering tank to produce a first sludge water and a third sludge, a step (S700) of passing the first sludge water through a second two-stage membrane coupled bioreactor to produce a second sludge water, and a step (S800) of mixing the second sludge water with the primary treated water supplied to the step (S200).

[0148] The wastewater treated in step (S10) may contain ammonia nitrogen (NH4-N) at a concentration of about 30 mg / L to about 50 mg / L and have a chemical oxygen demand (COD) at a concentration of about 300 mg / L to 1,000 mg / L.

[0149] Step (S300) may include, as a step performed in the first membrane coupled bioreactor, a step (S310) of converting ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of ammonia nitrogen (NH4-N) under aerobic conditions, and a step (S320) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas and nitrate nitrogen (NO3-N) under anoxic conditions, and may include, as a step performed in the second membrane coupled bioreactor, a step (S330) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions, and a step (S340) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas (N2) under anoxic conditions.

[0150] The first sludge generated in step (S200) may be supplied to the anaerobic digester in step (S500).

[0151] Step (S310) may be performed in a state where the average oxygen partial pressure inside the membrane installed in the first membrane coupled bioreactor is maintained in the range of about 17 kPa to about 23.2 kPa. When the average oxygen partial pressure inside the membrane installed in the first membrane coupled bioreactor is maintained in the range of about 17 kPa to about 23.2 kPa, the concentration of dissolved oxygen diffused into the biofilm formed on the membrane surface may be adjusted to 0.5 mg / L or less.

[0152] In step (S310), the average oxygen partial pressure can be controlled by combining the oxygen utilization efficiency and the oxygen transfer capacity, which is based on the dissolved oxygen concentration (C * ) is used to calculate, as shown in Equation 1.

[0153] A portion of the second sludge produced in step (S400) may be returned to the first two-stage membrane coupled bioreactor in step (S300).

[0154] Step (S700) may include, as a step performed in a third membrane coupled bioreactor, a step (S710) of converting ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of ammonia nitrogen (NH4-N) under aerobic conditions, and a step (S720) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas and nitrate nitrogen (NO3-N) under anoxic conditions, and may include, as a step performed in a fourth membrane coupled bioreactor, a step (S730) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions, and a step (S740) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas (N2) under anoxic conditions.

[0155] Hereinafter, an apparatus for treating wastewater according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

[0156] Figure 1 is a schematic diagram of a method and apparatus 100 for treating wastewater according to an embodiment.

[0157] refer to Figure 1 According to one embodiment of the present disclosure, a device 100 includes a first membrane coupled bioreactor 110 and a second membrane coupled bioreactor 120 .

[0158] The first membrane coupled bioreactor 110 may be configured to generate primary treated water TW1 by treating wastewater WW containing ammonia nitrogen (NH4-N). In this regard, the wastewater WW may contain ammonia nitrogen (NH4-N) at a concentration of about 30 mg / L to about 50 mg / L.

[0159] The second membrane-coupled bioreactor 120 may be configured to generate secondary treated water TW2 by further treating the primary treated water TW1 .

[0160] The first membrane coupled bioreactor 110 may be configured to operate sequentially under aerobic conditions and anoxic conditions.

[0161] In the following, reference will be made to Figure 2 and 3 The configuration, operation, and effects of the first membrane-coupled bioreactor 110 are described in detail.

[0162] Figure 2 It means that the installation Figure 1 A diagram of a first membrane-coupled bioreactor 110 of the apparatus 100 and a principle of inhibiting the activity of nitrite-oxidizing bacteria by the membrane, Figure 2 is a view illustrating a mass transfer path through a membrane and near the membrane of a first membrane coupled bioreactor, and Figure 3: is a view illustrating mass transfer paths through the membrane of the first membrane coupled bioreactor and in the vicinity of the membrane and reactions between substances.

[0163] First, refer to Figure 2 The first membrane coupled bioreactor 110 is configured so that the oxygen-containing gas is supplied from the outside of the membrane to the inside through a plurality of gas inlets, and a biofilm grows on the surface of the membrane. In particular, when the oxygen-containing gas is supplied to the liquid (i.e., wastewater) through the membrane, a biofilm can be formed near the membrane surface.

[0164] In particular, refer to Figure 2 and 3 When oxygen-containing gas is supplied to the liquid (i.e., wastewater) through the membrane, ammonia oxidizing bacteria (AOB) or nitrifying bacteria form a primary biofilm (called "nitrification") close to the surface of the membrane under aerobic conditions, and anaerobic ammonia oxidizing bacteria form a secondary biofilm (called "AMX") on the outside of the membrane (i.e., the primary biofilm side) under anoxic conditions. Accordingly, nitrite ions (NO2 - ) immediately reacts with ammonium ions (NH4 + ) reacts and is converted into nitrogen (N2).

[0165] More specifically, again referring to Figure 3 The first membrane coupled bioreactor 110 first converts ammonia nitrogen (NH4-N) (i.e., ammonium ions) into nitrite nitrogen (NO2-N) (i.e., nitrite ions) instead of nitrate nitrogen (NO3-N) (i.e., nitrate ions) under aerobic conditions by partial oxidation of ammonia nitrogen (NH4-N), and secondly converts ammonia nitrogen (NH4-N) (i.e., ammonium ions) and nitrite nitrogen (NO2-N) (i.e., nitrite ions) into nitrogen gas (N2) and nitrate nitrogen (NO3-N) (i.e., nitrate ions) under anoxic conditions.

[0166] In addition, the first membrane coupled bioreactor 110 can be configured so that the average oxygen partial pressure in the membrane installed therein is maintained in the range of about 17kPa to about 23.2kPa. As described above, the growth of the biofilm on the membrane surface depends on the substrate (i.e., ammonium ion) concentration outside the membrane (i.e., the main liquid), as well as the oxygen concentration and oxygen pressure inside the membrane. In addition, the important factors inside the membrane are the flow rate of the oxygen-containing gas supplied to the membrane and the average oxygen partial pressure inside the membrane. However, when wastewater containing low concentrations of ammonia nitrogen (NH4-N) is introduced, the only way to inhibit the growth of nitrite oxidizing bacteria (NOB) is to control the dissolved oxygen concentration. In contrast, as described above, when the average oxygen partial pressure inside the membrane installed in the first membrane coupled bioreactor 110 is maintained in the range of about 17kPa to about 23.2kPa, the dissolved oxygen concentration diffused into the biofilm formed on the membrane surface can be adjusted to 0.5mg / L or less, and when using this method, the dissolved oxygen concentration diffused into the biofilm can be continuously adjusted to 0.5mg / L or less, thereby enabling continuous operation.

[0167] The average oxygen partial pressure can be controlled by combining the oxygen utilization efficiency and the oxygen transfer capacity, which is based on the dissolved oxygen concentration (C * ) is used to calculate, as shown in Equation 1.

[0168] The second membrane-coupled bioreactor 120 may be configured to operate under anoxic conditions.

[0169] In the following, reference will be made to Figure 4 The configuration, operation, and effects of the second membrane-coupled bioreactor 120 are described in detail.

[0170] Figure 4 It is explained by Figure 1 A view of a membrane installed in the second membrane coupled bioreactor 120 of the apparatus 100 and a mass transfer path near the membrane and reactions between substances.

[0171] refer to Figure 4, the second membrane coupled bioreactor 120 can be configured to first convert nitrate nitrogen (NO3-N) (i.e., nitrate ions) into nitrite nitrogen (NO2-N) (i.e., nitrite ions) in the biofilm under anaerobic conditions, and secondly convert ammonia nitrogen (NH4-N) (i.e., ammonium ions) and nitrite nitrogen (NO2-N) (i.e., nitrite ions) into nitrogen gas (N2) in the main liquid under anaerobic conditions. In particular, in the treated water TW1 discharged from the first membrane coupled bioreactor 110, there are ammonia nitrogen (NH4-N), nitrite nitrogen (NO2-N), and nitrate nitrogen (NO3-N) generated by anaerobic ammonium oxidation (ANAMMOX) reaction. In the second membrane coupled bioreactor 120, the biogas produced after anaerobic digestion is supplied to the membrane instead of the oxygen-containing gas, wherein the CH4 gas contained in the biogas is used as an electron donor. When CH4 gas penetrates into the outer surface of the membrane, the microorganisms participating in the denitrification anaerobic methane oxidation (DAMO) reaction of converting CH4 gas into methanol dominate, and form a DAMO biofilm on the surface of the membrane. The methanol converted by the microorganisms participating in the DAMO reaction can be used as a denitrification carbon source, and by utilizing this carbon source, the nitrate nitrogen (NO3-N) discharged from the first membrane coupled bioreactor 110 can be reduced to nitrite nitrogen (NO2-N) by partial denitrification. Outside the DAMO biofilm, the residual ammonia nitrogen (NH4-N) present in the main liquid and the nitrite nitrogen (NO2-N) reduced by DAMO can be used as substrates to promote the growth of anaerobic ammonia oxidation (ANAMMOX) microorganisms, thereby forming an ANAMMOX biofilm on the surface of the DAMO biofilm. Through this, all remaining nitrogen components are converted into nitrogen (N2) and removed from the water system, and the nitrogen removal rate can be maximized.

[0172] In the following, reference will be made to Figure 5 An apparatus 200 for treating wastewater according to another embodiment of the present disclosure is described in detail.

[0173] refer to Figure 5 According to another embodiment of the present disclosure, the device 200 for treating wastewater includes an activated sludge tank 210, a first sedimentation tank 220, a first two-stage membrane coupled bioreactor 230, a second sedimentation tank 240, an anaerobic digester 250, a sludge dewatering tank 260 and a second two-stage membrane coupled bioreactor 270.

[0174] The activated sludge tank 210 may be configured to produce primary treated water TW1 by treating the wastewater WW containing ammonia nitrogen (NH4-N) and having COD. The activated sludge tank 210 is used to remove COD. In this regard, the wastewater WW may contain ammonia nitrogen (NH4-N) at a concentration of about 30 mg / L to about 50 mg / L and have a COD at a concentration of about 300 mg / L to about 1,000 mg / L.

[0175] The first settling tank 220 may be configured to generate secondary treated water TW2 and first sludge SLG1 by partially settling the primary treated water TW1.

[0176] In addition, the apparatus 200 for treating wastewater may be configured such that the first sludge SLG1 generated in the first settling tank 220 is supplied to the anaerobic digestion tank 250 .

[0177] The first two-stage membrane-coupled bioreactor 230 may be configured to generate tertiary treated water TW3 by further treating the secondary treated water TW2.

[0178] The first two-stage membrane coupled bioreactor 230 may include a first membrane coupled bioreactor (not shown) and a second membrane coupled bioreactor (not shown) connected in series to each other.

[0179] The first membrane coupled bioreactor can be configured to first convert ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) under aerobic conditions by partial oxidation of ammonia nitrogen (NH4-N), and secondly convert ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen and nitrate nitrogen (NO3-N) under anoxic conditions.

[0180] The first membrane coupled bioreactor may be configured such that an average oxygen partial pressure in the membrane installed therein is maintained below 20 kPa.

[0181] The average oxygen partial pressure can be controlled by combining the oxygen utilization efficiency and the oxygen transfer capacity, which is based on the dissolved oxygen concentration (C * ) is used to calculate, as shown in Equation 1.

[0182] In addition, the first membrane coupled bioreactor may have Figure 1 The first membrane coupled bioreactor 110 provided in the apparatus 100 for treating wastewater has the same configuration, operation, and effects, and therefore a detailed description thereof is not provided herein.

[0183] The second membrane coupled bioreactor can be configured to first convert nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions, and secondly convert ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen under anoxic conditions. The second membrane coupled bioreactor can have Figure 1 The second membrane coupled bioreactor 120 provided in the apparatus 100 for treating wastewater has the same configuration, operation, and effects, and therefore a detailed description thereof is not provided herein.

[0184] The second settling tank 240 may be configured to generate quaternary treated water TW4 and second sludge SLG2 by partially settling the tertiary treated water TW3.

[0185] Furthermore, the apparatus 200 for treating wastewater may be configured such that a portion of the second sludge SLG2 generated in the second settling tank 240 is returned to the first two-stage membrane coupled bioreactor 230 .

[0186] The anaerobic digester 250 may be configured to generate digested sludge DS by partially digesting the second sludge SLG2.

[0187] The sludge dewatering tank 260 may be configured to generate first sludge water SW1 and third sludge SLG3 by partially dehydrating the digested sludge DS.

[0188] The second two-stage membrane-coupled bioreactor 270 may be configured to generate second sludge water SW2 by further treating the first sludge water SW1 .

[0189] The second two-stage membrane coupled bioreactor 270 may include a third membrane coupled bioreactor (not shown) and a fourth membrane coupled bioreactor (not shown) connected to each other in series.

[0190] The third membrane coupled bioreactor may be configured to first convert ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) rather than nitrate nitrogen (NO3-N) by partial oxidation of ammonia nitrogen (NH4-N) under aerobic conditions, and secondly convert ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) and nitrate nitrogen (NO3-N) under anoxic conditions. The third membrane coupled bioreactor may have Figure 1 The first membrane coupled bioreactor 110 provided in the apparatus 100 for treating wastewater has the same configuration, operation, and effects, and therefore a detailed description thereof is not provided herein.

[0191] The fourth membrane coupled bioreactor can be configured to first convert nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions, and secondly convert ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) under anoxic conditions. Figure 1 The second membrane coupled bioreactor 120 provided in the apparatus 100 for treating wastewater has the same configuration, operation, and effects, and therefore a detailed description thereof is not provided herein.

[0192] Hereinafter, the present disclosure will be described in further detail with reference to the following examples. However, these examples are not intended to limit the present disclosure.

[0193] Experimental Examples 1 and 2: Simulated Wastewater Treatment

[0194] The first commercially released dynamic sewage / wastewater and purified water treatment simulator GPS-X is used to simulate the treatment of wastewater containing high concentrations (1,000 ppm or more) of ammonia nitrogen (NH4-N), such as landfill leachate or livestock wastewater, and the results are used as Figure 6 In addition, the treatment of wastewater containing low concentration (50 ppm or less) of ammonia nitrogen (NH4-N), such as sewage, was simulated by using GPS-X, and the results were as follows: Figure 7 The simulation conditions are shown in Table 1. The version used in these simulations is GPS-X 8.1.0, and the model used is MANTIS2. MANTIS2 is a new integrated model that integrates the most common biological, physical, and chemical processes in sewage / wastewater treatment facilities, and is a model developed by Hydromantis, which develops GPS-X.

[0195] [Table 1]

[0196]

[0197]

[0198] refer to Figure 6 , which confirmed that when the concentration of ammonia nitrogen in wastewater is high, high concentrations of nitrite nitrogen (NO2-N) are easily accumulated due to the inhibition and flushing of nitrite-oxidizing bacteria. Figure 7 , which confirmed that when the concentration of ammonia nitrogen in wastewater is low, the inhibition on the activity of nitrite oxidizing bacteria is negligible, making it difficult for nitrite nitrogen (NO2-N) to accumulate, and most of the nitrite nitrogen (NO2-N) is converted into nitrate nitrogen.

[0199] Experimental Example 3: Simulated Wastewater Treatment

[0200] In order to meet the ammonia to nitrite production ratio, which is the condition of the anaerobic ammonium oxidation reaction, control is required to inhibit the selective growth of ammonia oxidizing bacteria (AOB), i.e., the growth of nitrite oxidizing bacteria (NOB). There are three methods to inhibit NOB: 1) high concentration of influent free ammonia (FA); 2) low concentration of dissolved oxygen (DO); and 3) short hydraulic retention time (HRT).

[0201] In the case of high ammonia treatment, the growth of NOB was suppressed by high FA concentration without any other control methods, thus enabling the production of nitrite. However, in the case of low ammonia treatment, due to the low FA concentration, the other two control methods mentioned above were required to produce nitrite.

[0202] A membrane coupled bioreactor was proposed as a device to implement these two control methods, and its feasibility was verified by simulation. The results are shown in Table 2 and Figure 8 middle.

[0203] [Table 2]

[0204]

[0205]

[0206] Referring to Table 2, the NH4, NO2, and NO3 concentrations in the effluent are the concentrations of NH4, NO2, and NO3 contained in the treated water when each case was simulated. As shown in the above table, it was confirmed that even when the concentration of the influent ammonia was low (50 mgN / L), by controlling the inlet / outlet pressure and HRT, NH4 could be stably oxidized to NO2 while suppressing the generation of NO3. Figure 8 The NH4 concentration, NO2 concentration and NO3 concentration in the effluent of Table 2 are illustrated as stacked bar graphs for each case. In particular, Figure 8 It is a diagram showing the effect of the control method (1: Long average pressure control, 2: HRT control) proposed for stably oxidizing NH4 to NO2 while suppressing the production of NO3 when low-load NH4 flows into the first membrane coupled bioreactor.

[0207] exist Figure 8 , when the incoming ammonia concentration is 40 mgN / L, Case 1 is a case in which operation is performed by controlling the HRT to 3 hr and controlling the inlet / outlet air pressure of the membrane to 160 / 150 kPa. In Case 1, the Log average pressure is a value calculated by Equation 1. Case 2 is a case in which the inlet / outlet air pressure of Case 1 is changed to 170 / 160 kPa, and Case 3 is a case in which the HRT of Case 1 is changed.

[0208] Example 1: Simulated wastewater treatment

[0209] The simulation was performed in the same manner as in Experimental Example 2, except that the dissolved oxygen concentration in the biofilm formed by diffusion on the membrane surface was adjusted to 0.5 mg / L or less by adjusting the average oxygen partial pressure inside the membrane installed in the first membrane coupled bioreactor to be maintained below 20 kPa. The results confirmed that even when the ammonia nitrogen concentration in the wastewater was low, a high concentration of nitrite nitrogen (NO2-N) could be accumulated due to the inhibition of nitrite oxidizing bacteria, which was consistent with Figure 6 is very similar to the diagram shown in .

[0210] Although the present disclosure has been described with reference to the accompanying drawings and embodiments, these embodiments are provided for illustrative purposes only, and those skilled in the art to which the present disclosure relates will appreciate that various modifications and other equivalent embodiments may be made. Therefore, the true technical scope of the present disclosure should be defined by the technical spirit of the appended claims.

[0211] It should be understood that the embodiments described herein should be considered in a descriptive sense only and not for the purpose of limitation. The description of features or aspects in each embodiment should generally be considered as other similar features or aspects that can be used in other embodiments. Although one or more embodiments are described with reference to the accompanying drawings, it will be understood by those of ordinary skill in the art that various changes in form and details can be made therein without departing from the spirit and scope of the present disclosure as defined by the following claims.

Claims

1. A method for treating wastewater, comprising: A step (S10) of producing primary treated water by passing the wastewater containing ammonia nitrogen (NH4-N) through a first membrane coupled bioreactor; in, Part of the area of ​​the first membrane-coupled bioreactor is operated under aerobic conditions, and the other area of ​​the first membrane-coupled bioreactor is operated under anoxic conditions.

2. The method according to claim 1, further comprising a step (S20) of producing secondary treated water by passing the primary treated water produced in the step (S10) through a second membrane coupled bioreactor; in, The second membrane-coupled bioreactor is operated under anoxic conditions.

3. The method according to claim 1, wherein The step (S10) includes a step (S10-1) of converting ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of ammonia nitrogen (NH4-N) under aerobic conditions, and a step (S10-2) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) and nitrate nitrogen (NO3-N) under anoxic conditions.

4. The method according to claim 3, wherein The step (S10-1) involves converting ammonia nitrogen (NH4-N) into only nitrite nitrogen (NO2-N), as shown in reaction scheme 3: Reaction Scheme 3 Partial nitrification: NH4 + →NO2 - (Oxygen demand: 1.9kg-O2 / kg-NH4-N).

5. The method according to claim 4, wherein The step (S10-2) includes an anaerobic ammonium oxidation reaction, in which ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) react with each other and are oxidized into nitrogen (N2) and nitrate nitrogen (NO3-N), as shown in reaction scheme 4: Reaction Scheme 4 Anaerobic ammonium oxidation: NH4 + +NO2 - →N2 (organic carbon demand: 0kg-COD / kg-NO3-N).

6. The method according to claim 5, wherein The chemically equivalent overall reaction scheme of the step (S10-1) and the step (S10-2) is shown in Reaction Scheme 5: Reaction Scheme 5 Total chemical equivalent reaction: 1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O.

7. The method according to claim 3, wherein In the step (S10-1), the first membrane coupled bioreactor has a hydraulic retention time of within 4 hours, and the step (S10-1) is performed in a state where the average oxygen partial pressure in the oxygen-containing gas inside the membrane installed in the first membrane coupled bioreactor is maintained in the range of about 17 kPa to about 23.2 kPa.

8. The method according to claim 7, wherein In the step (S10-1), the average oxygen partial pressure in the oxygen-containing gas is controlled by combining the oxygen utilization efficiency and the oxygen transfer capacity, and the dissolved oxygen concentration C in the liquid phase in equilibrium with the gas phase in the membrane is calculated by the oxygen transfer model based on differential pressure shown in Equation 1. L To calculate the oxygen transfer capacity: Equation 1 in, In equation 1, J is the oxygen transfer capacity per second (mol / m 2 ·sec), K is the mass transfer coefficient (m 2 / sec), P 入 is the oxygen partial pressure at the inlet (Pa), P 出 is the oxygen partial pressure at the outlet (Pa), H is the Henry's law constant (Pa·m 2 / mol), and C L is the concentration of oxygen in the liquid (mol / m 3 ).

9. The method according to claim 2, wherein The step (S20) includes a step (S20-1) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anaerobic conditions, and a step (S20-2) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) under anaerobic conditions.

10. The method according to claim 9, wherein The step (S20-1) includes: The DAMO reaction of converting methane gas into methanol is shown in Reaction Scheme 6; and the reaction of converting nitrate nitrogen (NO3-N) only into nitrite nitrogen (NO2-N) by using methanol as a carbon source is shown in Reaction Scheme 7: Reaction Scheme 6 Methanolation: CH4 → CH3OH Reaction Scheme 7 Partial denitrification: NO3 - →NO2 - (Organic carbon demand: 1.9kg-COD / kg-NO3-N).

11. The method according to claim 10, wherein The step (S20-2) includes an anaerobic ammonium oxidation reaction, in which the residual ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) react with each other and are oxidized into nitrogen (N2) and nitrate nitrogen (NO3-N), as shown in Reaction Scheme 8: Reaction Scheme 8 Anaerobic ammonium oxidation: NH4 + +NO2 - →N2 (organic carbon demand: 0kg-COD / kg-NO3-N).

12. The method according to claim 11, wherein The chemically equivalent overall reaction scheme of the step (S20-1) and the step (S20-2) is shown in Reaction Scheme 9: Reaction Scheme 9 Total chemical equivalent reaction: 1NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O.

13. A method for treating wastewater, comprising: A step (S100) of producing primary treated water by passing wastewater containing ammonia nitrogen (NH4-N) through an activated sludge tank; A step (S200) of producing secondary treated water and first sludge by passing the primary treated water through a first settling tank; a step of producing tertiary treated water by passing the secondary treated water through a first two-stage membrane coupled bioreactor (S300); A step (S400) of producing quaternary treated water and secondary sludge by passing the tertiary treated water through a second settling tank; a step of passing the second sludge through an anaerobic digester to produce digested sludge (S500); a step of producing first sludge water and third sludge by passing the digested sludge through a sludge dewatering tank (S600); a step of producing second sludge water by passing the first sludge water through a second two-stage membrane coupled bioreactor (S700); and A step (S800) of mixing the second sludge water with the primary treated water supplied to the step (S200).

14. The method according to claim 13, wherein The step (S300) includes, as a step performed in the first membrane coupled bioreactor, a step (S310) of converting the ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of the ammonia nitrogen (NH4-N) under aerobic conditions, and a step (S320) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) and nitrate nitrogen (NO3-N) under anoxic conditions, and includes, as a step performed in the second membrane coupled bioreactor, a step (S330) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions, and a step (S340) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) under anoxic conditions.

15. The method according to claim 14, wherein The step (S310) is performed in a state in which an average oxygen partial pressure in the oxygen-containing gas inside the membrane installed in the first membrane coupled bioreactor is maintained in a range of about 17 kPa to about 23.2 kPa.

16. The method according to claim 15, wherein In the step (S310), the average oxygen partial pressure in the oxygen-containing gas is controlled by combining the oxygen utilization efficiency and the oxygen transfer capacity, and the dissolved oxygen concentration C in the liquid phase in equilibrium with the gas phase in the membrane is calculated by the oxygen transfer model based on differential pressure shown in Equation 1. L To calculate the oxygen transfer capacity: Equation 1 in, In equation 1, J is the oxygen transfer capacity per second (mol / m 2 ·sec), K is the mass transfer coefficient (m 2 / sec), P 入 is the oxygen partial pressure at the inlet (Pa), P 出 is the oxygen partial pressure at the outlet (Pa), H is the Henry's law constant (Pa·m 2 / mol), and C L is the concentration of oxygen in the liquid (mol / m 3 ).

17. The method according to claim 13, wherein The step (S700) includes, as a step performed in the third membrane coupled bioreactor, a step (S710) of converting the ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of the ammonia nitrogen (NH4-N) under aerobic conditions, and a step (S720) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas and nitrate nitrogen (NO3-N) under anoxic conditions (S720), and includes, as a step performed in the fourth membrane coupled bioreactor, a step (S730) of converting nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anoxic conditions, and a step (S740) of converting ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas (N2) under anoxic conditions.

18. The method according to claim 13, wherein The first sludge produced in the step (S200) is supplied to the anaerobic digester in the step (S500).

19. The method according to claim 13, wherein A portion of the second sludge produced in the step (S400) is returned to the first two-stage membrane coupled bioreactor in the step (S300).

20. A device for treating wastewater, comprising a first membrane coupled bioreactor configured to produce primary treated water by treating wastewater containing ammonia nitrogen (NH4-N), in, Part of the area of ​​the first membrane-coupled bioreactor is operated under aerobic conditions, and the other area of ​​the first membrane-coupled bioreactor is operated under anoxic conditions.

21. The device according to claim 20, further comprising a second membrane coupled bioreactor configured to produce secondary treated water by further treating the primary treated water produced in the first membrane coupled bioreactor, in, The second membrane-coupled bioreactor is configured to operate under anoxic conditions.

22. The device according to claim 21, wherein The first membrane coupled bioreactor is configured to first convert ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) under aerobic conditions by partial oxidation of ammonia nitrogen (NH4-N), and secondly convert ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas (N2) and nitrate nitrogen (NO3-N) under anoxic conditions.

23. The device according to claim 22, wherein The first membrane-coupled bioreactor is configured such that an average oxygen partial pressure in a membrane installed therein is maintained in a range of about 17 kPa to about 23.2 kPa.

24. The device according to claim 23, wherein The average oxygen partial pressure in the oxygen-containing gas is controlled by combining the oxygen utilization efficiency and the oxygen transfer capacity, and the oxygen transfer model based on differential pressure shown in Equation 1 is used according to the dissolved oxygen concentration C in the liquid phase in equilibrium with the gas phase in the membrane. L To calculate the oxygen transfer capacity: Equation 1 in, In equation 1, J is the oxygen transfer capacity per second (mol / m 2 ·sec), K is the mass transfer coefficient (m 2 / sec), P 入 is the oxygen partial pressure at the inlet (Pa), P 出 is the oxygen partial pressure at the outlet (Pa), H is the Henry's law constant (Pa·m 2 / mol), and C L is the concentration of oxygen in the liquid (mol / m 3 ).

25. The device according to claim 24, wherein The second membrane-coupled bioreactor is configured to first convert nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anaerobic conditions, and secondly convert ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas (N2) under anaerobic conditions.

26. A device for treating wastewater, comprising: an activated sludge tank configured to produce primary treated water by treating wastewater containing ammonia nitrogen (NH4-N) and having a chemical oxygen demand (COD); a first settling tank configured to produce secondary treated water and first sludge by partially settling the primary treated water; a first two-stage membrane-coupled bioreactor configured to produce tertiary treated water by further treating the secondary treated water; a second settling tank configured to produce quaternary treated water and secondary sludge by partially settling the tertiary treated water; an anaerobic digester configured to produce digested sludge by partially digesting the second sludge; a sludge dewatering tank configured to produce first sludge water and third sludge by partially dewatering the digested sludge; as well as The second two-stage membrane-coupled bioreactor is configured to produce second sludge water by further treating the first sludge water.

27. The device according to claim 26, wherein The device is configured to mix the second sludge water with wastewater supplied to the first settling tank.

28. The device according to claim 26, wherein The first two-stage membrane coupled bioreactor comprises a first membrane coupled bioreactor and a second membrane coupled bioreactor connected in series with each other, The second two-stage membrane coupled bioreactor comprises a third membrane coupled bioreactor and a fourth membrane coupled bioreactor connected in series with each other, Each of the first membrane coupled bioreactor and the third membrane coupled bioreactor is configured to firstly convert the ammonia nitrogen (NH4-N) into nitrite nitrogen (NO2-N) instead of nitrate nitrogen (NO3-N) by partial oxidation of the ammonia nitrogen (NH4-N) under aerobic conditions, and secondly convert the ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen gas and nitrate nitrogen (NO3-N) under anoxic conditions, and Each of the second membrane coupled bioreactor and the fourth membrane coupled bioreactor is configured to first convert nitrate nitrogen (NO3-N) into nitrite nitrogen (NO2-N) under anaerobic conditions, and secondly convert ammonia nitrogen (NH4-N) and nitrite nitrogen (NO2-N) into nitrogen (N2) under anaerobic conditions.

29. The device according to claim 28, wherein The first membrane-coupled bioreactor is configured such that an average oxygen partial pressure in a membrane installed therein is maintained in a range of about 17 kPa to about 23.2 kPa.

30. The device according to claim 29, wherein The average oxygen partial pressure in the oxygen-containing gas is controlled by combining the oxygen utilization efficiency and the oxygen transfer capacity, and the oxygen transfer model based on differential pressure shown in Equation 1 is used according to the dissolved oxygen concentration C in the liquid phase in equilibrium with the gas phase in the membrane. L To calculate the oxygen transfer capacity: Equation 1 in, In equation 1, J is the oxygen transfer capacity per second (mol / m 2 ·sec), K is the mass transfer coefficient (m 2 / sec), P 入 is the oxygen partial pressure at the inlet (Pa), P 出 is the oxygen partial pressure at the outlet (Pa), H is the Henry's law constant (Pa·m 2 / mol), and C L is the concentration of oxygen in the liquid (mol / m 3 ).

31. The device of claim 26, wherein The apparatus is configured such that the first sludge produced in the first settling tank is supplied to the anaerobic digestion tank.

32. The device of claim 26, wherein The apparatus is configured so that a portion of the second sludge produced in the second settling tank is returned to the first two-stage membrane-coupled bioreactor.

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