Improved AOA device and method for low-carbon advanced denitrification of municipal sewage

Abstract

The present application relates to a kind of for urban sewage low-carbon deep denitrification improved AOA device and utilize the composition to sludge deep dewatering method.The device described in the present application is sequentially connected to be provided with water inlet tank, anaerobic tank, the aerobic tank with MABR membrane module, anoxic tank and secondary sedimentation tank, the present application is provided with the aerobic tank with MABR membrane module, and it is more easy to realize partial nitrification of ammonia nitrogen for processing urban sewage, and the remaining ammonia nitrogen can be used for anaerobic ammonia oxidation.In addition, under low DO concentration, compared with the aerobic tank in the prior art, the N2O generated by the MABR membrane module provided in the present application will be lower, by utilizing internal carbon source PHA and glycogen for short-term denitrification to generate nitrite nitrogen for anaerobic ammonia oxidation bacteria to utilize, for mainstream urban sewage anaerobic ammonia oxidation denitrification provides a new way.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an improved AOA (A-MABR-A) device and method for low-carbon deep denitrification of urban wastewater. Background Technology

[0002] With rapid social development and improved living standards, nitrogen (N) pollution has become an increasingly serious environmental problem in aquatic ecosystems, with urban sewage being a significant source. Nitrification-denitrification is the most common method for treating nitrogen pollutants in wastewater; that is, under aeration conditions, nitrifying bacteria convert NH4+ into nitrogen. + -N is oxidized to NO2 - -N and NO3 - -N, and then NO2 produced under the action of heterotrophic denitrifying bacteria. - -N and NO3 - -N is converted to N2. Nitrification requires a large amount of aeration energy, while denitrification not only requires the addition of large amounts of organic matter, but also results in the rapid growth of heterotrophic bacteria, leading to the generation of large amounts of excess sludge. Aeration energy consumption, organic matter addition, and sludge disposal all increase the cost of wastewater treatment.

[0003] The AOA (Anaerobic-Aerobic-Anoxic) process refers to a process in which microorganisms convert organic matter into internal carbon sources, such as polyhydroxyalkanoates (PHAs), in the anaerobic stage; nitrification in the aerobic stage converts ammonia nitrogen into nitrate nitrogen or nitrite nitrogen; and finally, in the anoxic stage, microorganisms utilize the PHA or glycogen stored in the anaerobic stage and the glycogen (Gly) stored in the anoxic stage to achieve endogenous denitrification.

[0004] MABR (Membrane Aeration Biofilm Reactor) is a novel wastewater treatment process that combines gas separation membrane technology with biofilm technology. In the MABR process, the hollow fiber aeration membrane serves as a carrier for microbial growth and attachment, supplying oxygen to the biofilm through bubble-free aeration. Oxygen diffuses into the biofilm under pressure differential, while the biofilm maintains full contact with pollutants in the water. Since oxygen and pollutants are transported in opposite directions, a unique stratified structure forms within the biofilm: an inner and an outer layer. Compared to ammonia nitrogen, organic matter is a large molecule with slower mass transfer, resulting in the highest oxygen concentration and lowest organic matter concentration in the inner layer of the biofilm. This favors the growth of nitrifying bacteria. NO2 produced in the inner layer of the biofilm... - -N and NO3 --N diffuses into the outer layer of the biofilm, resulting in a low oxygen concentration and high organic matter concentration, which is conducive to the growth of heterotrophic denitrifying bacteria. Compared to mechanical aeration and blower aeration, the MABR process is a bubble-free aeration method with low mass transfer resistance and high transfer efficiency. The biofilm structure formed by heterogeneous mass transfer in the MABR process helps to achieve simultaneous nitrification, reducing the cost of organic matter addition and sludge disposal in wastewater treatment plants; in addition, bubble-free aeration can reduce the aeration energy consumption of wastewater treatment plants. Therefore, in terms of energy saving and consumption reduction, the MABR process has great application potential in wastewater treatment plants. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides an improved AOA (A-MABR-A) device and method for low-carbon deep nitrogen removal from urban wastewater. The method of this invention involves adding a MABR module to an aerobic tank and, by adjusting the reaction time, sludge return ratio, MABR aeration flow rate, and scrubbing intensity at each stage of the anaerobic-MABR-anoxic phase, achieving synergistic nitrogen removal through MABR nitrification and endogenous short-cut denitrification and anaerobic ammonia oxidation in the anoxic phase.

[0006] The technical solution adopted in this invention is as follows:

[0007] The first aspect of the present invention provides an improved AOA device for low-carbon deep denitrification of urban sewage, the structure of which includes an inlet tank, an anaerobic tank, an aerobic tank equipped with a membrane module, and a secondary sedimentation tank connected in sequence, wherein the membrane module is a MABR membrane module.

[0008] A second aspect of the present invention provides a method for low-carbon deep denitrification of urban wastewater using the improved AOA device, specifically comprising the following steps:

[0009] (1) Inoculate the nitrification-denitrification activated sludge into the device, start the aerobic tank aeration device, maintain the dissolved oxygen concentration in the aerobic tank at 2.0±0.5 mg / L, and restore the activity of the sludge when the effluent ammonia nitrogen is less than 5 mg / L and the effluent total nitrogen is less than 15 mg / L.

[0010] After the sludge activity is restored, keep the aeration device in the aerobic tank in the closed state, turn on the process blower of the membrane module, and monitor the change of ammonia nitrogen concentration in the aerobic tank in real time. When the ammonia nitrogen concentration is significantly increased, it indicates that the MABR module has successfully attached the membrane.

[0011] (2) The secondary sedimentation tank, the first return pipeline, and the anaerobic tank form the first sludge return, and the secondary sedimentation tank, the second return pipeline, and the anoxic tank form the second sludge return; partial nitrification in the aerobic tank is achieved by adjusting the aeration flow rate and scrubbing intensity of the MABR components and the flow rate of the first sludge return. "Partial nitrification" means that part of the ammonia nitrogen in the influent is oxidized into nitrite nitrogen or nitrate nitrogen, and the remainder still exists in the form of ammonia nitrogen; the flow rate of the second sludge return is adjusted to achieve endogenous short-cut denitrification in the anoxic tank. When nitrite nitrogen accumulates, it indicates that "endogenous short-cut denitrification" has been achieved; the realization of partial nitrification and endogenous short-cut denitrification can provide reaction substrates for the anaerobic ammonia oxidation process.

[0012] Among them, the regulation strategy for "partial nitration" is as follows:

[0013] Aeration flow rate: It is adjusted according to the nitrification effect (60% of ammonia nitrogen is oxidized) and the pre- and post-membrane pressure of the MABR module. For example, the pre-membrane pressure of the OxyFAS membrane module should not exceed 40 kPa and the post-membrane pressure should not exceed 30 kPa.

[0014] Scrubbing intensity: When the denitrification and oxygen transfer effects of the membrane module are poor, the scrubbing fan flow rate and scrubbing time can be appropriately increased to improve the scrubbing intensity;

[0015] First sludge return: Reducing the first sludge return flow can increase the ammonia nitrogen concentration in the MABR tank and is also beneficial for partial nitrification.

[0016] Endogenous short-range denitrification regulation strategy:

[0017] Secondary sludge return: If the nitrate nitrogen concentration in the anoxic tank is high, the secondary sludge return flow rate can be increased to improve the effect of endogenous denitrification.

[0018] (3) After step (2) is completed, anaerobic ammonia oxidation sludge is inoculated into the reaction device and mixed with the nitrification-denitrification activated sludge mentioned in step (1) to achieve stable operation of the system with partial nitrification-endogenous short-range denitrification-anaerobic ammonia oxidation coupled and synergistic deep denitrification.

[0019] The inventors of this application have discovered through long-term research that the essence of low-carbon deep denitrification of urban wastewater lies in the optimized enrichment of polyphosphate-accumulating bacteria, polysaccharide-accumulating bacteria, nitrifying bacteria, denitrifying bacteria, and anaerobic ammonia oxidizing bacteria within the system. Low-carbon denitrification of urban wastewater can be achieved using an AOA coupled with a MABR process. Generally, the DO concentration in a MABR process is below 0.5 mg / L, having minimal impact on the anoxic zone. After wastewater enters the MABR, ammonia nitrogen is oxidized to nitrate nitrogen. The MABR effluent includes both ammonia nitrogen and nitrate nitrogen. When these enter the anoxic zone, an internal carbon source can be used to convert nitrate nitrogen into nitrite nitrogen. Subsequently, ammonia nitrogen and the generated nitrite nitrogen are converted into N2 under the action of anaerobic ammonia oxidizing bacteria. Anaerobic ammonia oxidation is a process that uses nitrite as an electron acceptor and ammonia nitrogen as an electron donor, simultaneously converting nitrite and ammonia nitrogen into nitrogen gas under anaerobic conditions. The improved AOA device for low-carbon deep denitrification of urban wastewater described in this invention achieves the goal of low-carbon deep denitrification of urban wastewater through the synergistic effect of partial nitrification, endogenous short-cut denitrification, and anaerobic ammonia oxidation.

[0020] The present invention has the following beneficial effects:

[0021] (1) This invention provides an improved AOA device for low-carbon deep denitrification of urban wastewater, which is sequentially connected as follows: an inlet tank, an anaerobic tank, an aerobic tank equipped with a membrane module, an anoxic tank, and a secondary sedimentation tank. The membrane module is a MABR membrane module. The MABR membrane module of this invention aerates through membrane fibers, resulting in a very low dissolved oxygen (DO) concentration. Therefore, compared with the aerobic tanks in the prior art, the aerobic tank equipped with the MABR membrane module can more easily achieve partial nitrification of ammonia nitrogen in urban wastewater, and the remaining ammonia nitrogen can be used for anaerobic ammonia oxidation. In addition, at low DO concentrations, the N2O generated by the MABR membrane module of this invention is lower than that of the aerobic tanks in the prior art, because the MABR membrane module is more conducive to simultaneous nitrification and denitrification to reduce N2O to N2. Furthermore, this invention provides a new approach for anaerobic ammonia oxidation denitrification of mainstream urban wastewater by utilizing internal carbon sources PHA and glycogen for short-cut denitrification to generate nitrite nitrogen for use by anaerobic ammonia oxidizing bacteria.

[0022] (2) The method of low-carbon deep denitrification of urban sewage using the modified AOA device described in this invention saves energy. The aeration of the MABR membrane module is a bubble-free aeration, with low oxygen mass transfer resistance and high transfer efficiency, thus effectively saving energy. The method described in this invention uses an internal carbon source for denitrification, effectively saving carbon source. The method described in this invention only requires placing the MABR membrane module in the aerobic tank on the basis of the original AOA process, without increasing the land area. The method described in this invention can realize the synergistic deep denitrification of urban sewage by nitrification, endogenous denitrification and anaerobic ammonia oxidation. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The diagram shows a schematic of the improved AOA device for low-carbon deep denitrification of urban sewage as described in this invention.

[0025] Figure 2 The image shows the effect of using the method described in this invention for low-carbon deep denitrification of urban wastewater.

[0026] In the diagram: 1-Inlet tank, 2-Inlet pump, 3-Inlet pipe, 4-Anaerobic tank, 5-Activated sludge, 6-Aerobic tank with added membrane module, 7-Anoxic tank, 8-Outlet pipe, 9-Secondary sedimentation tank, 10-Agitator, 11-Blower, 12-Aeration disc, 13-Membrane module, 14-Membrane module process blower, 15-Membrane module scrubbing blower, 16-First sludge return, 17-Second sludge return. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Example 1

[0029] This embodiment provides an improved AOA device for low-carbon deep denitrification of urban sewage. Its structure includes an inlet tank 1, an anaerobic tank 4, an aerobic tank 6 equipped with a membrane module, an anoxic tank 7, and a secondary sedimentation tank 9 connected in sequence. The membrane module is a MABR membrane module 13.

[0030] The inlet tank 1 is equipped with an inlet pump 2, and the inlet tank 1 is connected to the anaerobic tank 4 via an inlet pipe 3. The anaerobic tank 4 is equipped with a stirring paddle 10.

[0031] The anoxic tank and the secondary sedimentation tank are connected by an outlet pipe 8. The anaerobic tank 4 and the anoxic tank 7 are mixed with activated sludge 5 by a stirring device - stirring paddle 10. The aerobic tank 6 is aerated by a blower 11 and an aeration disc 12. The MABR membrane module 13 is aerated by a membrane module process blower 14. The MABR membrane module 13 is wiped by a membrane module scrubbing blower 15.

[0032] After the activated sludge reacts in the anaerobic tank 4, aerobic tank 6 and anoxic tank 7, it enters the secondary sedimentation tank 9 through the effluent pipe 8 for sludge-water separation. The sludge produced in the secondary sedimentation tank 9 enters the anaerobic tank 4 through the first sludge return 16, and the sludge produced in the secondary sedimentation tank 9 enters the anoxic tank 7 through the second sludge return 17.

[0033] Example 2

[0034] This embodiment provides a method for low-carbon deep denitrification of urban wastewater based on the improved AOA device, using actual urban wastewater as the experimental subject: NH4 + -N=25~45 mg / L, COD=120~260 mg / L, pH=7.3-7.8, MABR tank sludge concentration maintained at 3000 mg / L, specific operation includes the following steps:

[0035] (1) Inoculate the nitrification-denitrification activated sludge into the device, start the aerobic tank aeration device, maintain the dissolved oxygen concentration in the aerobic tank at 2.0±0.5 mg / L, and restore the activity of the sludge when the effluent ammonia nitrogen is less than 5 mg / L and the effluent total nitrogen is less than 15 mg / L.

[0036] After the sludge activity is restored, keep the aeration device in the aerobic tank in the closed state, turn on the process blower of the membrane module, and monitor the change of ammonia nitrogen concentration in the aerobic tank in real time. When the ammonia nitrogen concentration is significantly increased, it indicates that the MABR module has successfully attached the membrane.

[0037] (2) The secondary sedimentation tank, the first return pipeline, and the anaerobic tank form the first sludge return, and the secondary sedimentation tank, the second return pipeline, and the anoxic tank form the second sludge return; by adjusting the aeration flow rate and scrubbing intensity of the MABR components and the flow rate of the first sludge return, partial nitrification in the aerobic tank is achieved ("partial nitrification" means that part of the ammonia nitrogen in the influent is oxidized into nitrite nitrogen or nitrate nitrogen, and the remainder still exists in the form of ammonia nitrogen), and the flow rate of the second sludge return is adjusted to achieve endogenous short-cut denitrification in the anoxic tank (when there is accumulation of nitrite nitrogen, it indicates that "endogenous short-cut denitrification" has been achieved). The realization of partial nitrification and endogenous short-cut denitrification can provide reaction substrates for the anaerobic ammonia oxidation process.

[0038] Among them, the regulation strategy for "partial nitration" is as follows:

[0039] Aeration flow rate: It is adjusted according to the nitrification effect (60% of ammonia nitrogen is oxidized) and the pre- and post-membrane pressure of the MABR module. For example, the pre-membrane pressure of the OxyFAS membrane module should not exceed 40 kPa and the post-membrane pressure should not exceed 30 kPa.

[0040] Scrubbing intensity: When the denitrification and oxygen transfer effects of the membrane module are poor, the scrubbing fan flow rate and scrubbing time can be appropriately increased to improve the scrubbing intensity;

[0041] First sludge return: Reducing the first sludge return flow can increase the ammonia nitrogen concentration in the MABR tank and is also beneficial for partial nitrification.

[0042] Endogenous short-range denitrification regulation strategy:

[0043] Secondary sludge return: If the nitrate nitrogen concentration in the anoxic tank is high, the secondary sludge return flow rate can be increased to improve the effect of endogenous denitrification.

[0044] (3) After step (2) is completed, anaerobic ammonia oxidation sludge is inoculated into the reaction device and mixed with the nitrification-denitrification activated sludge described in step (1) to achieve stable operation of the system with partial nitrification-endogenous short-range denitrification-anaerobic ammonia oxidation coupled and synergistic deep denitrification.

[0045] Experimental Example

[0046] The results of low-carbon deep denitrification of urban wastewater using the method described in Example 2 of this invention are as follows: Figure 2 As shown. From Figure 2 It can be seen that the improved AOA method for low-carbon deep denitrification of urban sewage described in this invention has the effect of low-carbon denitrification. Specifically, in stage I, ammonia nitrogen is partially nitrified to produce nitrate nitrogen; in stage II, nitrite nitrogen gradually accumulates under the action of endogenous denitrification; and in stage III, total nitrogen is removed after the addition of anaerobic ammonia oxidation sludge. Therefore, the improved AOA device and method for low-carbon deep denitrification of urban sewage described in this invention achieves low-carbon denitrification of urban sewage without the addition of a carbon source.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for low-carbon deep denitrification of urban wastewater using a modified AOA device, comprising the following steps: (1) Place the nitrification-denitrification activated sludge in the device, start the device, maintain the dissolved oxygen concentration in the aerobic tank at 2.0±0.5 mg / L, and the activity of the sludge is restored; The aerobic tank is equipped with a MABR membrane module. The aeration device in the aerobic tank is kept in the closed state. The process blower of the membrane module is turned on, and the change of ammonia nitrogen concentration in the aerobic tank is monitored in real time. When the ammonia nitrogen concentration increases significantly, it indicates that the MABR module has successfully attached the membrane. (2) The secondary sedimentation tank, the first return pipeline, and the anaerobic tank form the first sludge return, and the secondary sedimentation tank, the second return pipeline, and the anoxic tank form the second sludge return; Partial nitrification in the aerobic tank is achieved by adjusting the aeration flow rate and scrubbing intensity of the MABR components, HRT, and the flow rate of the first sludge return. By regulating the flow rate of the second sludge return and the HRT, endogenous short-cut denitrification is achieved in the anoxic tank, providing reaction substrates for the subsequent anaerobic ammonium oxidation process; (3) After step (2) is completed, the anaerobic ammonia oxidation sludge is inoculated into the device and mixed with the nitrification-denitrification activated sludge described in step (1) to achieve stable operation of the system with partial nitrification-endogenous short-range denitrification-anaerobic ammonia oxidation coupled and synergistic deep denitrification.

2. The method for low-carbon deep denitrification of urban wastewater using a modified AOA device according to claim 1, characterized in that, The anaerobic and anoxic tanks are equipped with stirring devices.

3. The method for low-carbon deep denitrification of urban wastewater using a modified AOA device according to any one of claims 1-2, characterized in that, The aerobic tank is also equipped with a blower, an aeration device, a membrane module process blower, and a membrane module scrubbing blower.

4. The method for low-carbon deep denitrification of urban wastewater using a modified AOA device according to claim 3, characterized in that, The aeration device is located at the bottom of the aerobic tank.

5. The method for low-carbon deep denitrification of urban wastewater using a modified AOA device according to claim 3, characterized in that, The aeration device is an aeration disc.

6. The method for low-carbon deep denitrification of urban wastewater using a modified AOA device according to claim 1, characterized in that, In step (1), the sludge activity is restored when the effluent ammonia nitrogen is less than 5 mg / L and the effluent total nitrogen is less than 15 mg / L.

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