Wastewater treatment system and wastewater treatment method

Abstract

The present application provides a wastewater treatment system and a wastewater treatment method, the system comprising: a membrane aerated biofilm reactor, a secondary sedimentation tank and an anaerobic ammonium oxidation reactor connected in sequence through pipelines; an inlet pipeline connected to the water inlet of the membrane aerated biofilm reactor, used to guide the wastewater to be treated into the membrane aerated biofilm reactor for treatment; an outlet pipeline connected to the water outlet of the anaerobic ammonium oxidation reactor, used to discharge the treated wastewater out of the system; a nitrification liquid reflux pipeline connected to the outlet pipeline and the membrane aerated biofilm reactor, used to reflux part of the outlet water of the outlet pipeline to the membrane aerated biofilm reactor. The membrane aerated biofilm reactor is used to couple the short-range nitrification reaction and the short-range denitrification reaction in the same reactor to achieve continuous and large-scale accumulation of nitrite, and can also remove a small amount of nitric nitrogen produced by the anaerobic ammonium oxidation reaction itself.

Description

Technical Field

[0001] The present application relates to the technical field of wastewater treatment, and in particular to a wastewater treatment system and a wastewater treatment method. Background Art

[0002] Nitrogen pollution is one of the most significant issues in current wastewater treatment, and therefore wastewater treatment technology for total nitrogen removal has long been a research hotspot within the industry. Among wastewater treatment technologies for total nitrogen removal, biological denitrification offers unique advantages in terms of treatment costs and reaction pathways. Anaerobic ammonium oxidation (ANAMMOX) denitrification, due to its unique biological denitrification reaction pathway, reduces aeration energy consumption compared to traditional biological denitrification processes and eliminates the need for additional carbon sources, significantly reducing treatment costs and making it the most efficient biological denitrification process currently available.

[0003] A common challenge in treating high-concentration ammonia-nitrogen wastewater using anaerobic ammonium oxidation (ANAMMOX) denitrification technology is achieving efficient nitrite accumulation to ensure the smooth and continuous operation of the ANAMMOX process. Another challenge is how to cost-effectively manage the small amount of nitrate nitrogen (also known as nitrate nitrogen or nitrate nitrogen) produced by the ANAMMOX reaction itself. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a wastewater treatment system and a wastewater treatment method.

[0005] Based on the above objectives, the first aspect of the present application provides a wastewater treatment system, characterized by comprising:

[0006] a membrane aeration biofilm reactor, a secondary sedimentation tank and an anaerobic ammonium oxidation reactor connected in sequence through pipelines;

[0007] a water inlet pipe connected to the water inlet of the membrane aeration biofilm reactor, for guiding the wastewater to be treated into the membrane aeration biofilm reactor for treatment;

[0008] An outlet pipe connected to the water outlet of the anaerobic ammonium oxidation reactor is used to discharge the treated wastewater out of the system;

[0009] connecting the outlet pipe and the nitrification liquid return pipe of the membrane aeration biofilm reactor to return part of the outlet water of the outlet pipe to the membrane aeration biofilm reactor;

[0010] In which, the membrane aeration reactor is provided with an aeration membrane connected to an external aeration device. The outer wall of the aeration membrane is loaded with a biofilm. Along the direction from the aeration membrane toward the biofilm, the biofilm includes an aerobic layer, a transition layer and an anoxic layer in sequence. The aerobic layer is used for a short-range nitrification reaction, the transition layer is used to remove part of the organic matter in the wastewater to be treated, and the anoxic layer is used for a short-range denitrification reaction.

[0011] Optionally, it also includes:

[0012] a segmented water inlet pipe connecting the water inlet pipe and the anaerobic ammonium oxidation reactor, for diverting part of the wastewater to be treated into the anaerobic ammonium oxidation reactor;

[0013] A sludge return pipe connecting the secondary sedimentation tank and the membrane aeration biofilm reactor is used to return the sludge separated in the secondary sedimentation tank to the membrane aeration biofilm reactor.

[0014] Based on the same inventive concept, the second aspect of the present application provides a wastewater treatment method, which is applied to a wastewater treatment system according to any one of the first aspects above, comprising:

[0015] Obtaining the organic matter concentration and ammonia nitrogen concentration in the wastewater to be treated in the water inlet pipe;

[0016] In response to determining that the organic matter concentration meets the first condition, the wastewater to be treated is directed into the membrane aerated biofilm reactor through the water inlet pipe for treatment;

[0017] The first condition is: 1≤C SCOD / (0.11C 氨氮 -C 标 )≤5;

[0018] Among them, C SCOD is the concentration of organic matter in the wastewater to be treated, C 氨氮 is the ammonia nitrogen concentration in the wastewater to be treated, C 标 It is the safe total nitrogen concentration in the outlet water of the outlet pipe.

[0019] Optionally, it also includes:

[0020] Obtain the concentrations of nitrite nitrogen, ammonia nitrogen and nitrate nitrogen in the effluent of the membrane aeration biofilm reactor;

[0021] In response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than a first threshold value, and the nitrate nitrogen concentration is less than a second threshold value, increasing the air intake of the external aeration device until a first stopping condition is met;

[0022] The first stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold, the nitrate nitrogen concentration is greater than or equal to the second threshold, or the intake volume is greater than a preset maximum intake threshold.

[0023] Optionally, in response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than a first threshold value, and the nitrate nitrogen concentration is greater than a second threshold value, adding a nitrifying bacteria inhibitor into the membrane aerated biofilm reactor and increasing the air intake of the external aeration device until a second stop condition is met;

[0024] The first stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold, the nitrate nitrogen concentration is greater than or equal to the second threshold, or the intake volume is greater than a preset maximum intake threshold.

[0025] Optionally, the second threshold is 0.05-0.3C 标 , the C 标 It is the safe total nitrogen concentration in the outlet water of the outlet pipe.

[0026] Optionally, in response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is greater than a first threshold, reducing the air intake of the external aeration device until a second stopping condition is met;

[0027] The second stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to a first threshold or the intake air volume is less than a preset minimum intake air threshold.

[0028] Optionally, after reducing the air intake of the external aeration device until a second stopping condition is met, the method further includes:

[0029] In response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is greater than a first threshold, connecting and opening a segmented water inlet pipe, directing a portion of the wastewater to be treated into the anaerobic ammonium oxidation reactor through the segmented water inlet pipe, and closing the segmented water inlet pipe when a third stop condition is met;

[0030] The third stopping condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to a first threshold.

[0031] Optionally, the flow rate of the segmented water inlet pipe is calculated by the following formula: Q 分 =0.76Q*C 亚硝 / C 氨氮 ;

[0032] Among them, Q 分 is the flow rate of the segmented water inlet pipe, Q is the total effluent flow rate of the membrane aeration biofilm reactor, C 亚硝 is the nitrite nitrogen concentration in the effluent of the membrane aeration biofilm reactor, C 氨氮 is the ammonia nitrogen concentration in the wastewater to be treated.

[0033] Optionally, the method further includes: obtaining a total influent flow rate entering the anaerobic ammonium oxidation reactor, and adjusting a nitrification liquid reflux rate in the nitrification liquid reflux pipe based on the total influent flow rate so that the nitrification liquid reflux rate satisfies a condition:

[0034] n1=(0.11C 氨氮 -C 标 ) / C 标 ,

[0035] Wherein, n1 is the nitration liquid reflux ratio, that is, the ratio of the nitration liquid reflux flow to the total influent flow, C 氨氮 is the ammonia nitrogen concentration of the wastewater to be treated, C 标 It is the safe total nitrogen concentration in the outlet water of the outlet pipe.

[0036] From the above, it can be seen that the wastewater treatment system and wastewater treatment method provided by the present application divert the wastewater to be treated to the membrane aeration biofilm reactor through the water inlet pipe, so that the wastewater to be treated can undergo a short-term nitrification reaction in the aerobic layer of the biofilm to remove part of the ammonia nitrogen in the wastewater to be treated, and the transition layer can also remove part of the organic matter in the wastewater to be treated, and the anoxic layer is used to undergo a short-term denitrification reaction to remove nitrate nitrogen from part of the effluent flowing back to the membrane aeration biofilm reactor. In this way, the system can couple the short-term nitrification reaction and the short-term denitrification reaction in the same reactor through the membrane aeration biofilm reactor to achieve continuous and large-scale accumulation of nitrite, and can also remove the small amount of nitrate nitrogen produced by the anaerobic ammonia oxidation reaction itself by returning the nitrified liquid to the membrane aeration biofilm reactor, without the need to add post-treatment equipment for nitrate nitrogen, saving treatment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in this application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are merely embodiments of this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] Figure 1 This is a schematic structural diagram of a wastewater treatment system according to an embodiment of the present application;

[0039] Figure 2 This is a schematic cross-sectional view of a membrane aeration biofilm reactor according to an embodiment of the present application;

[0040] Figure 3 This is a schematic diagram of the distribution of various substances in the membrane aeration biofilm reactor of an embodiment of the present application. In the figure, DO is dissolved oxygen and SCOD is organic matter.

[0041] In the figure, 1. Membrane aeration biofilm reactor; 11. Aeration membrane; 12. Biofilm; 121. Aerobic layer; 122. Transition layer; 123. Anoxic layer; 2. Secondary sedimentation tank; 3. Anaerobic ammonium oxidation reactor; 4. Outlet pipe; 5. Nitration liquid return pipe; 6. Sludge return pipe; 7. Inlet pipe; 8. Segmented inlet pipe. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments.

[0043] It should be noted that, unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods described, unless otherwise specified, are all conventional methods.

[0044] Nitrogen pollution is one of the most significant issues in current wastewater treatment, and therefore wastewater treatment technology for total nitrogen removal has long been a research hotspot within the industry. Among wastewater treatment technologies for total nitrogen removal, biological denitrification offers unique advantages in terms of treatment costs and reaction pathways. Anaerobic ammonium oxidation (ANAMMOX) denitrification, due to its unique biological denitrification reaction pathway, reduces aeration energy consumption compared to traditional biological denitrification processes and eliminates the need for additional carbon sources, significantly reducing treatment costs and making it the most efficient biological denitrification process currently available.

[0045] When using anaerobic ammonium oxidation (ANAMMOX) denitrification technology to treat high-concentration ammonia nitrogen wastewater, a common difficulty is how to achieve nitrite accumulation. Nitrite is an intermediate product of nitrogen in microbial chemical reactions and is also the substrate of ANAMMOX reactions. Therefore, related technologies use microbial chemical reactions (i.e., biological denitrification technology) to accumulate nitrite.

[0046] Biological denitrification technology is essentially a microbial chemical reaction that occurs under the catalysis of multiple biological enzymes. It requires the synergistic action of specific functional bacteria. The functional microorganisms involved mainly include ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB), denitrifying bacteria (DB) and anaerobic ammonia oxidizing bacteria (AnAOB).

[0047] Anaerobic ammonium oxidation (ANAMMOX) denitrification is a short-term nitrification reaction or a short-term denitrification reaction to achieve the accumulation of nitrite. The accumulated nitrite serves as the substrate for the ANAMMOX reaction to proceed smoothly. Specifically, the accumulation of nitrite can be achieved through a short-term nitrification reaction of ammonia nitrogen to provide substrate conditions for the ANAMMOX reaction (i.e., short-term nitrification-ANAMMOX, referred to as "PN / A"). This includes a one-stage process in which short-term nitrification and ANAMMOX are achieved in one reactor, and also includes a two-stage process in which short-term nitrification and ANAMMOX are run in different reactors. The accumulation of nitrite can also be achieved through a short-term denitrification reaction of nitrate nitrogen (i.e., short-term denitrification-ANAMMOX, referred to as "PD / A").

[0048] However, current treatment technologies can only achieve nitrite accumulation through short-term nitrification or short-term denitrification in a single reactor, or through short-term nitrification and short-term denitrification in two reactors. However, using only short-term nitrification or short-term denitrification to achieve nitrite accumulation does not simultaneously remove ammonia nitrogen and nitrate nitrogen. If two reactors are used to perform short-term nitrification and short-term denitrification reactions respectively, the treatment cost will be greatly increased and it will not be conducive to the continuous accumulation of nitrite.

[0049] In addition, when anaerobic ammonium oxidation reaction uses nitrite as the substrate for denitrification reaction, a small amount of nitrate nitrogen will inevitably be produced. When the total nitrogen concentration of the influent is high, this part of nitrate nitrogen needs to be further removed, which increases the treatment cost.

[0050] Based on this, the inventors thought that if the short-range nitrification reaction and the short-range denitrification reaction could be coupled in the same reactor, then it would be possible to achieve a continuous and large-scale accumulation of nitrite, which would be beneficial to the subsequent anaerobic ammonium oxidation reaction, and the nitrate nitrogen could be returned to the short-range denitrification reaction to remove the nitrate nitrogen in the effluent of the anaerobic ammonium oxidation reaction, without the need for additional treatment of the nitrate nitrogen in the effluent, thereby reducing treatment costs.

[0051] However, this method has the following problems: the AOB bacteria of the short-term nitrification reaction and the DB bacteria of the short-term denitrification reaction have different response requirements for the microbial environment (such as dissolved oxygen and organic matter, etc.). AOB bacteria are aerobic autotrophic bacteria, and DB bacteria are anoxic heterotrophic bacteria. Therefore, it is very difficult to achieve different microbial environments in the same reactor and fix the corresponding functional bacterial communities under the corresponding microbial environments.

[0052] Based on this, see Figure 1 and Figure 2 As shown, the present application provides a wastewater treatment system, comprising:

[0053] A membrane aeration biofilm reactor 1, a secondary sedimentation tank 2, and an anaerobic ammonium oxidation reactor 3 are sequentially connected by pipelines;

[0054] a water inlet pipe 7 connected to the water inlet of the membrane aeration biofilm reactor 1, for draining the wastewater to be treated into the membrane aeration biofilm reactor 1 for treatment;

[0055] An outlet pipe 4 connected to the outlet of the anaerobic ammonium oxidation reactor 3 is used to discharge the treated wastewater out of the system;

[0056] a nitrification liquid return pipe 5 connecting the outlet pipe 4 and the membrane aeration biofilm reactor 1 to return part of the outlet water of the outlet pipe 4 to the membrane aeration biofilm reactor 1;

[0057] In which, the membrane aeration reactor is provided with an aeration membrane 11 connected to an external aeration device. The outer wall of the aeration membrane 11 is loaded with a biofilm 12. Along the direction from the aeration membrane 11 toward the biofilm 12, the biofilm 12 sequentially includes an aerobic layer 121, a transition layer 122 and an anoxic layer 123. The aerobic layer 121 is used for a short-range nitrification reaction, the transition layer 122 is used to remove part of the organic matter in the wastewater to be treated, and the anoxic layer 123 is used for a short-range denitrification reaction.

[0058] Specifically, the membrane aeration biofilm reactor 1 has an air inlet connected to an external aeration device for receiving air from the external aeration device. The membrane aeration biofilm reactor 1 is also called MABR (Membrane Aeration Bioreactor), which is an advanced biological treatment device with high efficiency and energy saving.

[0059] The external aeration device can be used to provide the gas required by the membrane aerated biofilm reactor 1. This gas can be pure oxygen, air, or a gas containing a specific oxygen content. For example, in this embodiment, the gas can be air to reduce costs. Specifically, the external aeration device can be a fan that directly draws air and supplies it to the membrane aerated biofilm reactor 1.

[0060] like Figure 2 and Figure 3 The membrane aeration biofilm reactor 1 uses the air or oxygen in the hollow breathable membrane (i.e. the aeration membrane 11) to supply oxygen to the biofilm 12 growing on the surface of the aeration membrane 11. Figure 3 The reverse transfer of the liquid phase body (shown) forms different oxygen and organic matter concentration distributions in the biofilm 12 and the aeration membrane 11, allowing microorganisms with different living habits to coexist.

[0061] For example, the aeration membrane 11 can be a hollow fiber membrane, which serves as a medium for oxygenating the water and also as a carrier for the biofilm 12. The hollow fiber membrane allows oxygen to pass smoothly. Oxygen is pumped through the inner wall of the hollow fiber membrane to supply oxygen to the biofilm 12, forming an oxygen concentration gradient vertically from the inside to the outside of the membrane. This is converted into functional zones with different dissolved oxygen (DO) concentrations, allowing oxygen and pollutants to be transferred and consumed in opposite directions on the inside and outside of the biofilm 12, thereby forming a bubble-free oxygenation method and the unique layered structure of the biofilm 12.

[0062] like Figure 2 and Figure 3 As shown, along the direction from the aeration membrane 11 toward the biological membrane 12, the biological membrane 12 includes an aerobic layer 121, a transition layer 122 and an anoxic layer 123 in sequence.

[0063] The aerobic layer 121 is located near the aeration membrane 11. Therefore, the oxygen concentration in the aerobic layer 121 is the highest and the organic matter concentration is the lowest, providing a suitable living environment for aerobic autotrophic bacteria (such as AOB bacteria that perform short-term nitrification). Therefore, the wastewater entering the membrane aerated biofilm reactor 1 undergoes short-term nitrification, producing nitrite nitrogen (also known as nitrite nitrogen or nitrite).

[0064] Transition layer 122 is located between aerobic layer 121 and anoxic layer 123. As a result, the oxygen and organic matter concentrations in transition layer 122 are at a transitional stage, providing a suitable living environment for aerobic heterotrophic bacteria (e.g., organic matter-degrading bacteria). Therefore, in transition layer 122, some organic matter in the wastewater to be treated can be removed by the organic matter-degrading bacteria and a small amount of oxygen. Transition layer 122 also serves as a transition layer, preventing competition between bacteria in aerobic layer 121 and anoxic layer 123.

[0065] The anoxic layer 123 is located close to the main liquid phase, resulting in the lowest dissolved oxygen concentration and higher organic matter concentration in the anoxic layer 123, providing a suitable living environment for anoxic heterotrophic bacteria (such as DB bacteria in short-range denitrification reactions). Therefore, the nitrate-nitrogen in the effluent that flows back from the effluent pipe 4 to the membrane aerated biofilm reactor 1 can undergo a short-range denitrification reaction together with the organic matter in the anoxic layer 123. This can remove the small amount of nitrate-nitrogen produced by the anaerobic ammonium oxidation reaction itself by returning the nitrified liquid to the membrane aerated biofilm reactor 1, eliminating the need for additional post-treatment equipment for nitrate-nitrogen, saving treatment costs, and also removing organic matter from the wastewater to be treated.

[0066] During specific implementation, the wastewater to be treated is led into the membrane aeration biofilm reactor 1 through the water inlet pipe 7 for treatment. The wastewater to be treated undergoes a short-range nitrification reaction in the aerobic layer 121 of the membrane aeration biofilm reactor 1 to remove part of the ammonia nitrogen, and part of the organic matter is removed in the transition layer 122. Then, the wastewater treated by the membrane aeration biofilm reactor 1 enters the secondary sedimentation tank 2.

[0067] The secondary sedimentation tank 2 is used to achieve mud-water separation. The wastewater treated by the membrane aeration biofilm reactor 1 enters the secondary sedimentation tank 2. After the mud-water separation in the secondary sedimentation tank 2, the separated wastewater enters the anaerobic ammonium oxidation reactor 3 for further treatment.

[0068] In the anaerobic ammonium oxidation reactor 3, the ammonia nitrogen in the wastewater to be treated and the nitrite nitrogen accumulated in the membrane aeration biofilm reactor 1 through the short-cut nitrification reaction and the short-cut denitrification reaction are anaerobic ammonium oxidized by the action of anaerobic ammonium oxidizing bacteria to generate nitrogen gas and nitric nitrogen to remove the ammonia nitrogen in the wastewater.

[0069] Part of the wastewater treated by the anaerobic ammonium oxidation reactor 3 is directly discharged from the system through the outlet pipe 4, while the other part of the wastewater is returned to the membrane aerated biofilm reactor 1 through the nitrification liquid return pipe 5. The returned wastewater contains a small amount of nitrate nitrogen generated by the anaerobic ammonium oxidation reaction. This part of the nitrate nitrogen can undergo a short-range denitrification reaction with the organic matter in the anoxic layer 123, which can not only remove this part of the nitrate nitrogen, but also generate nitrite nitrogen.

[0070] In the present application, the wastewater to be treated is drained to the membrane aerated biofilm reactor 1 through the water inlet pipe 7, so that the wastewater to be treated can undergo a short-term nitrification reaction in the aerobic layer 121 of the biofilm 12 to remove part of the ammonia nitrogen in the wastewater to be treated, and the transition layer 122 can also remove part of the organic matter in the wastewater to be treated, and the anoxic layer 123 is used to undergo a short-term denitrification reaction to remove nitrate nitrogen in part of the effluent returned to the membrane aerated biofilm reactor 1. In this way, the system solves the problem that the AOB bacteria of the short-term nitrification reaction and the DB bacteria of the short-term denitrification cannot coexist in the same reactor through the membrane aerated biofilm reactor 1, and realizes the coupling of the short-term nitrification reaction and the short-term denitrification reaction in the same reactor, thereby realizing the continuous and large-scale accumulation of nitrite, ensuring the smooth and stable progress of the subsequent anaerobic ammonia oxidation reaction, and at the same time, the small amount of nitrate nitrogen produced by the anaerobic ammonia oxidation reaction itself can be removed by returning the nitrified liquid to the membrane aerated biofilm reactor 1, without the need to add post-treatment equipment for nitrate nitrogen, saving treatment costs.

[0071] In some embodiments, the wastewater treatment system further comprises:

[0072] a segmented water inlet pipe 8 connecting the water inlet pipe 7 and the anaerobic ammonium oxidation reactor 3, for diverting part of the wastewater to be treated into the anaerobic ammonium oxidation reactor 3;

[0073] The sludge return pipe 6 connecting the secondary sedimentation tank 2 and the membrane aeration biofilm reactor 1 is used to return the sludge separated in the secondary sedimentation tank 2 to the membrane aeration biofilm reactor 1 .

[0074] Specifically, the sludge separated in the secondary sedimentation tank 2 is returned to the membrane aeration biofilm reactor 1 through the sludge return pipe 6 .

[0075] A valve is provided on the segmented water inlet pipe 8. When it is necessary to directly drain part of the wastewater to be treated into the anaerobic ammonium oxidation reactor 3, the valve on the segmented water inlet pipe 8 is opened to allow part of the wastewater to be treated to enter the anaerobic ammonium oxidation reactor 3 through the segmented water inlet pipe 8 to adjust the ammonia nitrogen concentration and nitrite nitrogen concentration of the wastewater entering the anaerobic ammonium oxidation reactor 3.

[0076] In some embodiments, the system further comprises a nitrite nitrogen detection device, an ammonia nitrogen detection device and a nitrate nitrogen detection device provided at the outlet of the secondary sedimentation tank 2 for detecting the nitrite nitrogen concentration, ammonia nitrogen concentration and nitrate nitrogen concentration in the outlet water of the membrane aeration bioreactor.

[0077] In some embodiments, the system further comprises a dissolved oxygen testing device disposed in the membrane aeration biofilm reactor 1 for testing the dissolved oxygen in the water in the membrane aeration biofilm reactor 1 .

[0078] In some embodiments, the system further includes sensors disposed at the air inlet and outlet ends of the aeration membrane 11 for detecting gas flow, pressure, oxygen content, and the like.

[0079] The present application also provides a wastewater treatment method, which is applied to the wastewater treatment system described in any of the above embodiments, comprising:

[0080] Obtaining the organic matter concentration and ammonia nitrogen concentration in the wastewater to be treated in the water inlet pipe 7;

[0081] In response to determining that the organic matter concentration meets the first condition, the wastewater to be treated is led into the membrane aerated biofilm reactor 1 through the water inlet pipe 7 for treatment;

[0082] The first condition is: 1≤C SCOD / (0.11C 氨氮 -C 标 )≤5;

[0083] Among them, C SCOD is the concentration of organic matter in the wastewater to be treated, C 氨氮 is the ammonia nitrogen concentration in the wastewater to be treated, C标 It is the safe total nitrogen concentration in the outlet water of outlet pipe 4.

[0084] Specifically, denitrification reaction requires organic matter as an electron donor, and organic matter provides a carbon source for the short-range denitrification of nitric nitrogen, and the organic matter concentration is very important. If the organic matter concentration is too high or too low, it will have an adverse effect. When the organic matter concentration is too high, the nitrite nitrogen produced by short-range nitrification or short-range denitrification will directly complete the complete denitrification reaction with the organic matter, and cannot stay in the half-way reaction state, that is, it cannot stay in the state of generating nitrite nitrogen, which causes the nitrite nitrogen produced by short-range nitrification or short-range denitrification to be removed, and then causes the subsequent anaerobic ammonia oxidation reaction to be unable to proceed smoothly. The organic matter concentration is too low to achieve the removal of nitric nitrogen in the reflux liquid. Therefore, suitable organic matter concentration is a key factor in the wastewater treatment method of the present application.

[0085] In this application, after numerous experimental verifications, when the organic matter concentration meets the first condition, the organic matter concentration is appropriate at this time, which can not only remove most of the nitrate nitrogen in the reflux liquid, but also ensure that the organic matter will not reduce the nitrite nitrogen produced by short-range nitrification or short-range denitrification, thereby ensuring the smooth progress of the subsequent anaerobic ammonia oxidation reaction.

[0086] The first condition is: 1≤C SCOD / (0.11C 氨氮 -C 标 )≤5. Among them, C 标 is the safe total nitrogen concentration in the outlet water of the outlet pipe 4, and the safe total nitrogen concentration may be a concentration that meets the emission standards.

[0087] Among them, C SCOD 、C 氨氮 and C 标 The unit can be mg / L.

[0088] When C SCOD / (0.11C 氨氮 -C 标 )<1, the organic matter concentration is too low to remove nitric nitrogen from the reflux liquid; when C SCOD / (0.11C 氨氮 -C 标 )>5, the organic matter concentration is too high, heterotrophic bacteria multiply, and nitrite nitrogen is removed by short-range denitrification, and the system will not be able to maintain balance.

[0089] Preferably, 2≤C SCOD / (0.11C 氨氮 -C 标 )≤3, when C SCODWhen the concentration meets this condition, the organic matter concentration is in the optimal range, which can not only remove most or even all of the nitrate nitrogen in the reflux liquid, but also ensure that the organic matter will not reduce the nitrite nitrogen produced by short-range nitrification or short-range denitrification, thereby ensuring the smooth progress of the subsequent anaerobic ammonium oxidation reaction.

[0090] For example, C SCOD / (0.11C 氨氮 -C 标 ) can specifically be 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.

[0091] In some embodiments, the wastewater treatment method further comprises:

[0092] Obtaining the nitrite nitrogen concentration, ammonia nitrogen concentration, and nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1;

[0093] In response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than a first threshold value, and the nitrate nitrogen concentration is less than a second threshold value, increasing the air intake of the external aeration device until a first stopping condition is met;

[0094] The first stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold, the nitrate nitrogen concentration is greater than or equal to the second threshold, or the intake volume is greater than a preset maximum intake threshold.

[0095] Specifically, after the effluent from the membrane aerated biofilm reactor 1 is separated in the secondary sedimentation tank 2, it enters the anaerobic ammonium oxidation reactor 3 directly. Therefore, the concentrations of nitrite and ammonia in the effluent from the membrane aerated biofilm reactor 1 must be regulated to meet the conditions for the anaerobic ammonium oxidation reaction. Furthermore, to prevent nitrite from being fully nitrified and converted into nitrate, the nitrate concentration in the effluent from the membrane aerated biofilm reactor 1 must be controlled.

[0096] Therefore, when the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than the first threshold value, and the nitrate nitrogen concentration is less than the second threshold value, it means that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is small at this time, which does not meet the conditions for the subsequent anaerobic ammonium oxidation reaction, and the ammonia nitrogen concentration is not too large, which will not cause the full nitrification of nitrite nitrogen. Therefore, at this time, the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration can be increased by increasing the nitrite nitrogen concentration and reducing the ammonia nitrogen concentration to meet the conditions for the anaerobic ammonium oxidation reaction.

[0097] Therefore, at this time, the air intake of the external aeration device is increased, thereby increasing the amount of oxygen entering the membrane aeration biofilm reactor 1. By increasing the oxygen content, the short-range nitrification reaction is promoted, the content of nitrite nitrogen is increased and the content of ammonia nitrogen is reduced, and the ratio of nitrite nitrogen concentration to ammonia nitrogen concentration can be increased to meet the conditions for anaerobic ammonia oxidation reaction.

[0098] For example, when the external aeration device is a fan, the air intake volume can be increased by increasing the frequency of the fan.

[0099] When a first stopping condition is met, the increase in the air intake volume of the external aeration device is stopped. The first stopping condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold, the nitrate nitrogen concentration is greater than or equal to the second threshold, or the air intake volume is greater than a preset maximum air intake threshold.

[0100] Specifically, the first threshold is a preferred ratio of the anaerobic ammonium oxidation reaction obtained through theoretical calculation. Exemplarily, the first threshold may be 1.2 to 1.4. Preferably, the first threshold may be 1.31.

[0101] When the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold value, it means that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 has reached the optimal ratio for the anaerobic ammonium oxidation reaction, and is suitable for directly flowing into the anaerobic ammonium oxidation reactor 3 for reaction. At this time, the increase in the air intake of the external aeration device can be stopped.

[0102] The second threshold value is a preset suitable nitrate-nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1. When the nitrate-nitrogen concentration is greater than or equal to the second threshold value, it indicates that the nitrate-nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1 is too high, and there is a risk that nitrite nitrogen may undergo full nitrification and be converted into nitrate nitrogen. In this case, increasing the air intake of the external aeration device should be stopped, otherwise it will cause nitrite nitrogen loss, which is not conducive to the subsequent anaerobic ammonium oxidation reaction.

[0103] The preset maximum air intake threshold is the maximum air intake value of the preset external aeration device. When the air intake volume is greater than the preset maximum air intake threshold, it means that the air intake volume has reached the maximum air intake value of the external aeration device. If the air intake volume continues to increase, there will be safety hazards. Therefore, at this time, the air intake volume of the external aeration device should be stopped to ensure safety.

[0104] In some embodiments, in response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than a first threshold value, and the nitrate nitrogen concentration is greater than a second threshold value, a nitrifying bacteria inhibitor is added to the membrane aerated biofilm reactor 1, and the air intake of the external aeration device is increased until a first stop condition is met;

[0105] The first stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold, the nitrate nitrogen concentration is greater than or equal to the second threshold, or the intake volume is greater than a preset maximum intake threshold.

[0106] Specifically, when the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than a first threshold value, and the nitrate nitrogen concentration is greater than a second threshold value, it means that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is small at this time, which does not meet the conditions for the subsequent anaerobic ammonium oxidation reaction, and the ammonia nitrogen concentration is too high, which may cause the full nitrification of nitrite nitrogen. Therefore, it is necessary to inhibit the conversion of nitrite nitrogen into nitrate nitrogen at this time, and to increase the ratio of nitrite nitrogen concentration to the ammonia nitrogen concentration to meet the conditions for the anaerobic ammonium oxidation reaction.

[0107] Therefore, a nitrifying bacteria inhibitor is added to the membrane aerated biofilm reactor 1 to reduce the nitrate nitrogen content and inhibit the conversion of nitrite nitrogen into nitrate nitrogen. At the same time, the air intake of the external aeration device is increased, thereby increasing the amount of oxygen entering the membrane aerated biofilm reactor 1. By increasing the oxygen content, the short-range nitrification reaction is promoted, the nitrite nitrogen content is increased, and the ammonia nitrogen content is reduced. In turn, the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration can be increased to meet the conditions for the anaerobic ammonium oxidation reaction.

[0108] When a first stopping condition is met, increasing the air intake of the external aeration device is stopped, and adding the nitrifying bacteria inhibitor is stopped. The first stopping condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold, the nitrate nitrogen concentration is equal to the second threshold, or the air intake is greater than a preset maximum air intake threshold.

[0109] It is worth noting that after adding the nitrifying bacteria inhibitor, the nitrate nitrogen content in the effluent will decrease. However, once the nitrate nitrogen concentration is greater than or equal to the second threshold, it means that the nitrate nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1 is still too high, and there is a risk that nitrite nitrogen will undergo full nitrification and be converted into nitrate nitrogen. At this time, the increase in the air intake of the external aeration device should be stopped, otherwise it will cause nitrite nitrogen loss, which is not conducive to the subsequent anaerobic ammonium oxidation reaction.

[0110] In some embodiments, the second threshold is 0.05-0.3C 标 , the C 标 It is the safe total nitrogen concentration in the outlet water of the outlet pipe 4.

[0111] Specifically, when the second threshold is 0.05-0.3C 标 When the second threshold is less than 0.05C, the nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is appropriate, which can prevent nitrite nitrogen from being directly oxidized to nitrate nitrogen. 标When the nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is appropriate, it is possible to avoid the direct oxidation of nitrite to nitrate nitrogen. However, if the nitrate nitrogen concentration is to be controlled to such a low level, it is necessary to strictly control the short-cut denitrification reaction in the membrane aeration biofilm reactor 1, so that the short-cut denitrification reaction must consume almost all the nitrate nitrogen, which is not conducive to the actual process control. When the second threshold is greater than 0.3C 标 When the nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is too high, nitrite nitrogen may be directly oxidized to nitrate nitrogen, which is not conducive to the subsequent anaerobic ammonium oxidation reaction.

[0112] For example, the second threshold may be 0.05C 标 , 0.1C 标 , 0.15C 标 , 0.2C 标 , 0.25C 标 , 0.3C 标 wait.

[0113] In some embodiments, in response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is greater than a first threshold, the air intake of the external aeration device is reduced until a second stopping condition is met;

[0114] The second stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to a first threshold or the intake air volume is less than a preset minimum intake air threshold.

[0115] Specifically, when the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is greater than the first threshold, it means that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is too large, which is not conducive to the subsequent anaerobic ammonium oxidation reaction. At this time, the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration should be reduced.

[0116] At this time, the air intake of the external aeration device is reduced to reduce the amount of oxygen entering the membrane aeration biofilm reactor 1. By reducing the oxygen content, the short-range nitrification reaction is reduced, the content of nitrite nitrogen is reduced, and the ratio of nitrite nitrogen concentration to ammonia nitrogen concentration can be reduced to meet the conditions of anaerobic ammonia oxidation reaction.

[0117] When a second stopping condition is met, the reduction of the air intake of the external aeration device is stopped. The second stopping condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to a first threshold or the air intake is less than a preset minimum air intake threshold.

[0118] When the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold value, it means that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 has reached the optimal ratio for the anaerobic ammonium oxidation reaction, and is suitable for directly flowing into the anaerobic ammonium oxidation reactor 3 for reaction. At this time, the reduction of the air intake of the external aeration device can be stopped.

[0119] The preset minimum air intake threshold is the preset minimum air intake value of the external aeration device. When the air intake volume is less than the preset maximum air intake threshold, it means that the air intake volume has reached the minimum air intake value of the external aeration device. If the air intake volume continues to be reduced, aeration will not be able to be carried out effectively. Therefore, the reduction of the air intake volume of the external aeration device should be stopped at this time.

[0120] In some embodiments, after reducing the air intake of the external aeration device until the second stopping condition is met, the method further includes:

[0121] In response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is greater than a first threshold, connecting and opening the segmented water inlet pipe 8, and directing part of the wastewater to be treated into the anaerobic ammonia oxidation reactor 3 through the segmented water inlet pipe 8, until the segmented water inlet pipe 8 is closed when a third stop condition is met;

[0122] The third stopping condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to a first threshold.

[0123] Specifically, after reducing the air intake of the external aeration device until the second stop condition is met, if the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration remains greater than the first threshold, it indicates that even after reducing the air intake, the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration cannot be reduced to the first threshold. In this case, since the air intake cannot be further reduced, the nitrite nitrogen concentration cannot be further reduced. The only way to reduce the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is to increase the ammonia nitrogen concentration.

[0124] Therefore, at this time, the segmented water inlet pipe 8 is connected and opened, and part of the wastewater to be treated is drained into the anaerobic ammonium oxidation reactor 3 through the segmented water inlet pipe 8 to increase the ammonia nitrogen concentration in the wastewater entering the anaerobic ammonium oxidation reactor 3, thereby reducing the ratio of nitrite nitrogen concentration to the ammonia nitrogen concentration.

[0125] When a third stopping condition is met, the segmented water inlet pipe 8 is closed. The third stopping condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to a first threshold.

[0126] When the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold value, it means that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 has reached the optimal ratio for the anaerobic ammonium oxidation reaction, and is suitable for directly flowing into the anaerobic ammonium oxidation reactor 3 for reaction. At this time, the segmented water inlet pipe 8 can be closed, and there is no need to continue to increase the ammonia nitrogen concentration in the wastewater entering the anaerobic ammonium oxidation reactor 3.

[0127] In the present application, the nitrite nitrogen concentration, ammonia nitrogen concentration and nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 are monitored, and the aeration volume (i.e., the air intake volume of the external aeration device) is regulated based on the different conditions of the nitrite nitrogen concentration, ammonia nitrogen concentration and nitrate nitrogen concentration, and then the nitrite nitrogen concentration, ammonia nitrogen concentration and nitrate nitrogen concentration are regulated to ensure that the nitrite nitrogen concentration and ammonia nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 meet the conditions of the anaerobic ammonium oxidation reaction and the nitrate nitrogen concentration is appropriate, thereby preventing the nitrite nitrogen from being fully nitrified and converted into nitrate nitrogen, and ensuring the smooth and stable progress of the anaerobic ammonium oxidation reaction.

[0128] In some embodiments, the flow rate of the segmented water inlet pipe 8 is calculated by the following formula: Q 分 =0.76Q*C 亚硝 / C 氨氮 ;

[0129] Among them, Q 分 is the flow rate of the segmented water inlet pipe 8, Q is the total effluent flow rate of the membrane aeration biofilm reactor 1, and C 亚硝 is the nitrite nitrogen concentration in the effluent of membrane aeration biofilm reactor 1, C 氨氮 is the ammonia nitrogen concentration in the wastewater to be treated.

[0130] Specifically, based on the total effluent flow Q of the membrane aeration biofilm reactor 1, the nitrite nitrogen concentration C in the effluent of the membrane aeration biofilm reactor 1 亚硝 and the ammonia nitrogen concentration C in the wastewater to be treated 氨氮 To determine the flow rate of the segmented water inlet pipe 8, so that after the wastewater entering the anaerobic ammonium oxidation reactor 3 from the segmented water inlet pipe 8 and the wastewater entering the anaerobic ammonium oxidation reactor 3 from the membrane aeration biofilm reactor 1 are mixed in the anaerobic ammonium oxidation reactor 3, the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration can be equal to the first threshold value, which meets the optimal reaction conditions of the anaerobic ammonium oxidation reaction, so as to ensure the smooth and stable progress of the anaerobic ammonium oxidation reaction.

[0131] In some embodiments, since the nitrite nitrogen concentration, ammonia nitrogen concentration, and nitrate nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1 may vary slightly at different times, the nitrite nitrogen concentration, ammonia nitrogen concentration, and nitrate nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1 described herein may be the concentration at a specific moment or the average concentration over a specific time period. For example, the nitrite nitrogen concentration, ammonia nitrogen concentration, and nitrate nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1 may be the concentration at a specific moment or the average concentration over a specific time period.

[0132] In some embodiments, all concentrations involved in this application may be the concentration at a certain moment or the average concentration within a certain time period.

[0133] In some embodiments, the wastewater treatment method further comprises: obtaining the total influent flow rate entering the anaerobic ammonium oxidation reactor 3, and adjusting the nitrification liquid reflux rate in the nitrification liquid reflux pipe 5 based on the total influent flow rate so that the nitrification liquid reflux rate satisfies the condition: n1=(0.11C 氨氮 -C 标 ) / C 标 , where n1 is the nitration liquid reflux ratio, i.e. the ratio of the nitration liquid reflux flow to the total influent flow, C 氨氮 is the ammonia nitrogen concentration of the wastewater to be treated, C 标 It is the safe total nitrogen concentration in the outlet water of outlet pipe 4.

[0134] Specifically, since a small amount of nitrate nitrogen will be produced during the anaerobic ammonium oxidation reaction process, the residual nitrate nitrogen will increase the concentration of total nitrogen. Therefore, the nitrification liquid is refluxed through the nitrification liquid reflux pipe 5, and the produced nitrate nitrogen is refluxed to the membrane aerated biofilm reactor 1, so that a short-range denitrification reaction occurs in the membrane aerated biofilm reactor 1 to remove this part of the nitrate nitrogen.

[0135] Based on the total influent flow, the nitrification liquid reflux flow rate in the nitrification liquid reflux pipe 5 is adjusted so that the nitrification liquid reflux flow rate satisfies the condition: n1=(0.11C 氨氮 -C 标 ) / C 标 When the reflux rate of the nitrification liquid meets this condition, the reflux ratio of the nitrification liquid is moderate, which can ensure the effective removal of nitric nitrogen while not damaging the environment in the membrane aeration biofilm reactor 1. When the reflux ratio of the nitrification liquid reflux pipe 5 is too low, the total nitrogen content of the effluent from the outlet pipe 4 will exceed the standard, making the final effluent water quality of the system fail to meet the discharge standard; when the reflux ratio is too high, on the one hand, it will carry more dissolved oxygen, which is easy to damage the environment in the membrane aeration biofilm reactor 1, and the denitrification efficiency will be difficult to be effectively improved.

[0136] The technical effects of the present application are further illustrated below through specific examples and comparative examples.

[0137] Example 1

[0138] Organic matter concentration C in a certain industrial wastewater to be treated SCOD is 1000mg / L, ammonia nitrogen concentration C 氨氮 1000mg / L, nitrate nitrogen concentration <20mg / L, the final treated effluent requires a total nitrogen concentration of C 标 Less than or equal to 70mg / L.

[0139] First, calculate whether the organic matter content in the wastewater to be treated meets the first condition.

[0140] C SCOD / (0.11C 氨氮 -C 标 )=1000 / (0.11*1000-70)=25>5, indicating that the organic matter content in the wastewater to be treated does not meet the first condition and is not suitable for directly entering the membrane aeration biofilm reactor 1 for treatment.

[0141] Therefore, it is necessary to set up an organic matter removal facility at the front end of the membrane aeration biofilm reactor 1. In this embodiment, the organic matter removal facility can be a high-load aeration tank, which uses aerobic bacteria to perform biological oxidation to remove organic matter in the influent.

[0142] Control the appropriate residence time and aeration volume, and control the BCOD concentration in the effluent of the high-load aeration tank at 80 / L to make C SCOD / (0.11C 氨氮 -C 标 In this embodiment, the residence time is controlled to be 12 to 30 hours, and the load can be 0.5 to 6 kg BOD / m 3 d.

[0143] Since the organic matter concentration in the wastewater after treatment in the high-load aeration tank meets the first condition, this wastewater is fed into the membrane aeration reactor and mixed with the returning nitrification solution to form the influent. A portion of the ammonia nitrogen in the influent undergoes a short-term nitrification reaction in the aerobic layer 121 of the membrane aerated biofilm reactor 1, converting it to nitrite nitrogen. Nitrate nitrogen in the returning nitrification solution undergoes a short-term denitrification reaction in the anoxic layer 123 of the membrane aerated biofilm reactor 1, using the remaining organic matter in the water as a carbon source, converting nitrate nitrogen to nitrite nitrogen.

[0144] Then, the concentration of nitrite nitrogen, ammonia nitrogen and nitrate nitrogen in the effluent of the membrane aeration biofilm reactor 1 is obtained. When the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than 1.31 (i.e., the first threshold value), and the nitrate nitrogen concentration is less than 0.2C 标(i.e. the second threshold), the air intake of the external aeration device is increased until the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to 1.31 and the nitrate nitrogen concentration is greater than or equal to 0.2C 标 Or stop when the intake air volume is greater than a preset maximum intake air threshold.

[0145] When the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than 1.31, and the nitrate nitrogen concentration is greater than 0.2C 标 , then add a nitrifying bacteria inhibitor into the membrane aeration biofilm reactor 1 and increase the air intake of the external aeration device until the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to 1.31 and the nitrate nitrogen concentration is greater than or equal to 0.2C 标 Or stop when the intake air volume is greater than a preset maximum intake air threshold.

[0146] When the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is greater than 1.31, the air intake of the external aeration device is reduced until the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to 1.31 or the air intake is less than a preset minimum air intake threshold.

[0147] After reducing the air intake of the external aeration device, if the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is still greater than 1.31, the segmented water inlet pipe 8 is connected and opened, and part of the wastewater to be treated is led into the anaerobic ammonium oxidation reactor 3 through the segmented water inlet pipe 8 until the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to 1.31. The flow rate of the segmented water inlet pipe 8 is calculated by the following formula: Q 分 =0.76Q*C 亚硝 / C 氨氮 .

[0148] After the above-mentioned control steps, it is ensured that the ratio of the nitrite nitrogen concentration of the wastewater entering the anaerobic ammonium oxidation reactor 3 to the ammonia nitrogen concentration is equal to 1.31. At this time, nitrite nitrogen and ammonia nitrogen react in the anaerobic ammonium oxidation reactor 3 to generate nitrate nitrogen and nitrogen gas to achieve the removal of ammonia nitrogen.

[0149] The total nitrogen concentration of the effluent treated in the anaerobic ammonium oxidation reactor 3 is monitored. When the total nitrogen concentration meets the requirements, the treated effluent is directly discharged; when the total nitrogen concentration does not meet the requirements, the effluent is returned to the membrane aerated biofilm reactor 1 through the nitrification liquid return pipe 5. The nitrification liquid return flow rate in the nitrification liquid return pipe 5 is adjusted based on the total influent flow rate so that the nitrification liquid return flow rate meets the condition: n1 = (0.11C 氨氮 -C 标 ) / C 标 , in order to control the appropriate reflux ratio and ensure that nitric nitrogen can be converted.

[0150] Monitor the effluent nitrate nitrogen concentration, effluent ammonia nitrogen concentration and effluent total nitrogen concentration in the effluent flowing out of the effluent pipe.

[0151] Example 2

[0152] The difference from Example 1 is that the BCOD concentration in the effluent of the high-load aeration tank is controlled at 120 mg / L to make C SCOD / (0.11C 氨氮 -C 标 )=3.

[0153] Example 3

[0154] The difference from Example 1 is that the BCOD concentration in the effluent of the high-load aeration tank is controlled at 40 mg / L to make C SCOD / (0.11C 氨氮 -C 标 )=1.

[0155] Example 4

[0156] The difference from Example 1 is that the BCOD concentration in the effluent of the high-load aeration tank is controlled at 200 mg / L to make C SCOD / (0.11C 氨氮 -C 标 )=5.

[0157] Example 5

[0158] The difference from Example 1 is that the nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is controlled to be 0.1C 标 .

[0159] Example 6

[0160] The difference from Example 1 is that the nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is controlled to be 0.3C 标 .

[0161] Example 7

[0162] The difference from Example 1 is that the ratio of the nitrite nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 to the ammonia nitrogen concentration is controlled to be 1.

[0163] Example 8

[0164] The difference from Example 1 is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is controlled to be 1.4.

[0165] Example 9

[0166] The difference from Example 1 is that the nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is controlled to be 0.05C标 .

[0167] Comparative Example 1

[0168] The difference from Example 1 is that the BCOD concentration in the effluent of the high-load aeration tank is controlled at 20 mg / L to make C SCOD / (0.11C 氨氮 -C 标 )=0.5.

[0169] Comparative Example 2

[0170] The difference from Example 1 is that the BCOD concentration in the effluent of the high-load aeration tank is controlled at 240 mg / L to make C SCOD / (0.11C 氨氮 -C 标 )=6.

[0171] Comparative Example 3

[0172] The difference from Example 1 is that the nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is controlled to be 0.35C 标 .

[0173] Comparative Example 4

[0174] The difference from Example 1 is that the ratio of the nitrite nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 to the ammonia nitrogen concentration is controlled to be 0.9.

[0175] Comparative Example 5

[0176] The difference from Example 1 is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration in the effluent of the membrane aeration biofilm reactor 1 is controlled to be 1.5.

[0177] Table 1 Test data list of embodiments and comparative examples

[0178]

[0179] It is worth noting that the total nitrogen concentration in the effluent is the sum of the effluent nitrate nitrogen concentration, the effluent ammonia nitrogen concentration, the effluent organic nitrogen concentration, and the effluent nitrite nitrogen concentration. In specific implementation, as long as the total nitrogen concentration in the effluent meets the standard, it will be sufficient.

[0180] As shown in Table 1 above, in Examples 1 to 9, the organic matter concentration in the wastewater to be treated entering the membrane aeration biofilm reactor was controlled to make C SCOD / (0.11C 氨氮 -C 标) is within an appropriate range, and the ratio of nitrite nitrogen concentration to ammonia nitrogen concentration and nitrate nitrogen concentration in the effluent of the membrane aeration biofilm reactor is controlled, creating good conditions for the back-end anaerobic ammonia oxidation reaction, greatly improving the treatment efficiency of ammonia nitrogen, reducing the ammonia nitrogen content in the effluent, and the nitrate nitrogen concentration in the effluent has basically not increased, without the need to add post-treatment equipment for nitrate nitrogen.

[0181] In Example 3, compared with Example 1 and Example 2, due to insufficient carbon source in Example 3, the denitrification reaction is not sufficient, so that the nitrate nitrogen generated by the anaerobic ammonium oxidation reaction cannot be effectively removed, so the nitrate nitrogen concentration in the effluent is slightly higher than that in the influent, but the total nitrogen concentration still meets the standard.

[0182] In Example 6, compared with Example 1, the nitrate nitrogen concentration in the effluent of the membrane aerated biofilm reactor increases, and nitrate nitrogen continues to be generated in the subsequent anaerobic ammonia oxidation reaction, so that the final effluent nitrate nitrogen concentration is higher than that in the influent, but the total nitrogen concentration still meets the standard.

[0183] In Comparative Example 1, due to C SCOD / (0.11C 氨氮 -C 标 ) is too small, the organic matter concentration is too low, and the nitrate nitrogen in the reflux liquid cannot be effectively removed, resulting in a significant increase in the nitrate nitrogen concentration in the effluent.

[0184] In Comparative Example 2, due to C SCOD / (0.11C 氨氮 -C 标 ) is too large, the organic matter concentration is too high, heterotrophic bacteria multiply, and nitrite nitrogen is removed by short-range denitrification, so that anaerobic ammonia oxidation cannot continue smoothly and ammonia nitrogen cannot be removed efficiently, which ultimately leads to a high ammonia nitrogen concentration in the effluent.

[0185] In Comparative Example 3, since the nitrate nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1 is too high, nitrite nitrogen is directly oxidized to nitrate nitrogen, which is not conducive to the subsequent anaerobic ammonium oxidation reaction and causes the nitrate nitrogen concentration in the effluent to be too high.

[0186] In Comparative Example 4, since the ratio of the nitrite nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1 to the ammonia nitrogen concentration is too small, the nitrite nitrogen concentration is too low, which is not conducive to the subsequent anaerobic ammonium oxidation reaction, resulting in a low ammonia nitrogen removal rate and a high ammonia nitrogen content in the final effluent.

[0187] In Comparative Example 5, since the ratio of the nitrite nitrogen concentration in the effluent of the membrane aerated biofilm reactor 1 to the ammonia nitrogen concentration is too large, the nitrite nitrogen concentration is too high, so that the final effluent contains a portion of nitrite nitrogen, which ultimately leads to a high total nitrogen content in the effluent.

[0188] To sum up, the wastewater treatment system and wastewater treatment method provided by the present application divert the wastewater to be treated to the membrane aeration biofilm reactor through the water inlet pipe, so that the wastewater to be treated can undergo a short-term nitrification reaction in the aerobic layer of the biofilm to remove part of the ammonia nitrogen in the wastewater to be treated, and the transition layer can also remove part of the organic matter in the wastewater to be treated, and the anoxic layer is used to undergo a short-term denitrification reaction to remove nitrate nitrogen in part of the effluent returned to the membrane aeration biofilm reactor. In this way, the system can couple the short-term nitrification reaction and the short-term denitrification reaction in the same reactor through the membrane aeration biofilm reactor to achieve continuous and large-scale accumulation of nitrite, and can also remove the small amount of nitrate nitrogen produced by the anaerobic ammonia oxidation reaction itself by returning the nitrified liquid to the membrane aeration biofilm reactor, without the need to add post-treatment equipment for nitrate nitrogen, saving treatment costs.

[0189] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. Within the scope of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present disclosure as described above, which are not provided in detail for the sake of simplicity.

[0190] The embodiments of the present disclosure are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A wastewater treatment method, applied to a wastewater treatment system, characterized in that: The wastewater treatment system comprises: A membrane aeration biofilm reactor, a secondary sedimentation tank and an anaerobic ammonium oxidation reactor connected in sequence through pipelines; A water inlet pipe connected to the water inlet of the membrane aerated biofilm reactor, used for guiding the wastewater to be treated into the membrane aerated biofilm reactor for treatment; A water outlet pipe connected to the water outlet of the anaerobic ammonium oxidation reactor, used to discharge the treated wastewater out of the system; A nitrification liquid return pipe connecting the outlet pipe and the membrane aerated biofilm reactor is used to return part of the outlet water of the outlet pipe to the membrane aerated biofilm reactor; The membrane aeration reactor is provided with an aeration membrane connected to an external aeration device, and the outer wall of the aeration membrane is loaded with a biofilm. Along the direction from the aeration membrane to the biofilm, the biofilm includes an aerobic layer, a transition layer and an anoxic layer in sequence. The aerobic layer is used for a short-range nitrification reaction, the transition layer is used for removing part of the organic matter in the wastewater to be treated, and the anoxic layer is used for a short-range denitrification reaction. The method comprises: Obtaining the organic matter concentration and ammonia nitrogen concentration in the wastewater to be treated in the water inlet pipe; In response to determining that the organic matter concentration meets the first condition, the wastewater to be treated is directed into the membrane aerated biofilm reactor through the water inlet pipe for treatment; The first condition is: 1≤C SCOD / (0.11C 氨氮 -C 标 )≤5, Among them, C SCOD is the concentration of organic matter in the wastewater to be treated, C 氨氮 is the ammonia nitrogen concentration in the wastewater to be treated, C 标 It is the safe total nitrogen concentration in the outlet water of the outlet pipe.

2. The method according to claim 1, characterized in that The wastewater treatment system also includes: A segmented water inlet pipe connected to the water inlet pipe of the anaerobic ammonium oxidation reactor is used to guide part of the wastewater to be treated into the anaerobic ammonium oxidation reactor; The sludge return pipeline connecting the secondary sedimentation tank and the membrane aerated biofilm reactor is used to return the sludge separated in the secondary sedimentation tank to the membrane aerated biofilm reactor.

3. The method according to claim 1, characterized in that Also includes: Obtaining the concentrations of nitrite nitrogen, ammonia nitrogen and nitrate nitrogen in the effluent of the membrane aerated biofilm reactor; In response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than a first threshold value, and the nitrate nitrogen concentration is less than a second threshold value, increasing the air intake of the external aeration device until a first stop condition is met; Among them, the first stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold, the nitrate nitrogen concentration is greater than or equal to the second threshold, or the intake volume is greater than a preset maximum intake threshold.

4. The method according to claim 3, characterized in that In response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is less than a first threshold value, and the nitrate nitrogen concentration is greater than a second threshold value, adding a nitrifying bacteria inhibitor into the membrane aerated biofilm reactor, and increasing the air intake of the external aeration device until a first stop condition is met; Among them, the first stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to the first threshold, the nitrate nitrogen concentration is greater than or equal to the second threshold, or the intake volume is greater than a preset maximum intake threshold.

5. The method according to claim 3, characterized in that: The second threshold is 0.05-0.3C 标 , the C 标 It is the safe total nitrogen concentration in the outlet water of the outlet pipe.

6. The method according to claim 3, characterized in that In response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is greater than a first threshold, reducing the air intake of the external aeration device until a second stop condition is met; The second stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to a first threshold or the intake air volume is less than a preset minimum intake air threshold.

7. The method according to claim 6, characterized in that After reducing the air intake of the external aeration device until the second stopping condition is met, the method further includes: In response to determining that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is greater than a first threshold, connecting and opening a segmented water inlet pipe, directing part of the wastewater to be treated into the anaerobic ammonia oxidation reactor through the segmented water inlet pipe, and closing the segmented water inlet pipe when a third stop condition is met; The third stop condition is that the ratio of the nitrite nitrogen concentration to the ammonia nitrogen concentration is equal to a first threshold.

8. The method according to claim 2, characterized in that: The flow rate of the segmented water inlet pipeline is calculated by the following formula: Q 分 =0.76Q*C 亚硝 / C 氨氮 ; Among them, Q 分 is the flow rate of the segmented water inlet pipeline, Q is the total effluent flow rate of the membrane aerated biofilm reactor, C 亚硝 is the nitrite nitrogen concentration in the effluent of the membrane aerated biofilm reactor, C 氨氮 is the ammonia nitrogen concentration in the wastewater to be treated.

9. The method according to claim 1, characterized in that: Also includes: The total influent flow rate entering the anaerobic ammonium oxidation reactor is obtained, and the nitrification liquid reflux rate in the nitrification liquid reflux pipeline is adjusted based on the total influent flow rate so that the nitrification liquid reflux rate satisfies the condition: n1=(0.11C 氨氮 -C 标 ) / C 标 , Wherein, n1 is the nitration liquid reflux ratio, that is, the ratio of the nitration liquid reflux flow to the total influent flow, C 氨氮 is the ammonia nitrogen concentration in the wastewater to be treated, C 标 It is the safe total nitrogen concentration in the outlet water of the outlet pipe.

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