A short-cut nitrification-denitrification coupled micro-aerobic biochemical treatment method based on MABR

Abstract

This invention relates to a short-cut nitrification-denitrification coupled with microaerobic biological treatment method based on MABR, belonging to the field of water treatment technology. The invention mainly consists of a two-stage MABR-PN / DN tank, a two-stage MABR microaerobic tank, a sedimentation tank, an air supply system, and a monitoring system. The MABR-PN / DN tank and the MABR microaerobic tank are respectively implanted with MABR membrane tanks. Wastewater is sequentially processed through the first-stage MABR-PN / DN tank, the first-stage MABR microaerobic tank, the second-stage MABR-PN / DN tank, the second-stage MABR microaerobic tank, and the sedimentation tank. The air supply system is separately set up, supplying air to the MABR-PN / DN tank and the MABR microaerobic tank through pipelines. This invention establishes a short-cut nitrification-denitrification and low-aerobic nitrification-denitrification process using a microbial membrane grown on the outer surface of the MABR membrane filaments as a carrier. Simultaneously, it utilizes the two-stage MABR-PN / DN tank and the two-stage MABR microaerobic tank, eliminating the need for an internal reflux system for nitrified liquid to remove nitrogen, thus improving the effluent indicators of urban wastewater treatment plants. This invention has advantages such as good pollutant removal effect, saving external carbon source addition, saving land, short treatment cycle, low energy consumption, and reduced sludge production.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to a short-cut nitrification-denitrification coupled microaerobic biochemical treatment method based on MABR. Background Technology

[0002] Urban wastewater treatment plants are a crucial link in the end-of-pipe control of water pollution and the long-term maintenance of a clean water environment. The core treatment structure in a wastewater treatment plant is the biological treatment unit. In order to better control pollutants and reduce pollution to the water environment, stricter requirements have been put forward for the effluent quality indicators of urban wastewater treatment plants, especially for nitrogen. The requirements for nitrogen effluent are becoming increasingly stringent. In order to improve denitrification efficiency, external carbon sources need to be consumed, which increases costs and sludge production, adding a burden to subsequent treatment processes.

[0003] Currently, with the continuous development of urbanization and the improvement of people's living standards, the urban population and water consumption are gradually increasing, and the sewage discharge in urban areas is also increasing day by day. In order to better control pollutants and reduce the pollution to the water environment, stricter requirements for the discharge water quality indicators of urban sewage treatment plants have been put forward. However, the influent concentration has shown a phenomenon of low carbon and high nitrogen, which belongs to sewage treatment with a low carbon-to-nitrogen ratio (C / N < 4). For sewage with a low carbon-to-nitrogen ratio, traditional AAO, MBR, MBBR and other processes generally have the following problems: (1) the need to add external carbon sources such as sodium acetate, which results in high operating costs and is prone to secondary pollution; (2) high energy consumption of aeration in the aerobic stage; (3) denitrification is easily affected by dissolved oxygen shock, resulting in poor system stability; (4) large sludge production and high subsequent treatment costs.

[0004] MABR has advantages such as "no-bubble aeration, oxygen mass transfer efficiency ≥60%, and special biofilm structure", but existing applications are mostly limited to single aerobic or simultaneous nitrification-denitrification (SND) level. It does not provide a complete process system and usage method for the parameter control, rapid system start-up and long-term stable operation after the coupling of PN / DN and micro-aerobic phase of MABR technology. Summary of the Invention

[0005] This invention provides a two-stage coupled process of "MABR-PN / DN + MABR micro-aerobic", which combines the synchronous nitrification and denitrification of MABR with the nitrification effect of MABR technology under micro-aerobic environment, and achieves efficient nitrogen removal under low carbon conditions by properly controlling parameters.

[0006] The specific technical solution is as follows:

[0007] The short-cut nitrification-denitrification coupled microaerobic biochemical treatment method based on MABR is characterized by the following specific steps:

[0008] S1 System Construction: The system mainly consists of two-stage MABR-PN / DN tanks, two-stage MABR micro-aerobic tanks, a sedimentation tank, an air supply system, and a monitoring system. MABR membrane tanks are implanted in the MABR-PN / DN tanks and the MABR micro-aerobic tanks respectively. Wastewater is sequentially passed through the first-stage MABR-PN / DN tank, the first-stage MABR micro-aerobic tank, the second-stage MABR-PN / DN tank, the second-stage MABR micro-aerobic tank, and the sedimentation tank. The air supply system is set up separately and supplies air to the MABR-PN / DN tanks and the MABR micro-aerobic tanks through pipelines.

[0009] S2 Biofilm Initiation: Simultaneous inoculation of the two-stage MABR-PN / DN tank and the two-stage MABR micro-aerobic tank using mixed sludge from the aerobic section and sedimentation tank of the wastewater treatment plant; activating the air supply system, intermittently introducing water, and adjusting the air supply rate, dissolved oxygen (DO), and hydraulic retention time in stages; when NO2... - When the -N accumulation rate reaches 80% and remains so for more than 3 days, the MABR-PN / DN tank is considered to have successfully formed a biofilm; when the effluent COD is ≤50mg / L and remains so for more than 3 days, the MABR micro-aerobic tank is considered to have successfully formed a biofilm.

[0010] S3 operating parameter adjustment: After successful biofilm formation, operate the system. The effluent water quality TN≤10mg / L and COD≤30mg / L meets the discharge standards. Adjust the air supply pressure and air supply flow rate to shorten the hydraulic retention time under the condition of meeting the effluent water quality requirements. The total hydraulic retention time is controlled within 15 hours for stable operation.

[0011] The indicators monitored by the monitoring system in step S1 include DO, ORP, NH3-N, and NO2. - -N, NO3 - -N, COD;

[0012] In step S1, the gas supply system mainly includes gas supply equipment, gas supply pipelines, and valves, which supply gas to the first-stage MABR-PN / DN tank, the second-stage MABR-PN / DN tank, the first-stage MABR micro-aerobic tank, and the second-stage MABR micro-aerobic tank, respectively. Each gas supply pipeline is equipped with a valve for control.

[0013] In step S2, the mixed sludge is made by mixing aerobic activated sludge (3.5 g / L - 5 g / L) with sedimentation tank sludge, and the concentration of the mixed sludge is controlled not to exceed 7 g / L.

[0014] The S2 step is divided into two stages: Stage 1: Air supply pressure 10-40 kPa; DO concentration of 0.4-0.5 mg / L in Stage 1 and Stage 2 MABR-PN / DN tanks; DO concentration of 0.5-1.0 mg / L in Stage 1 and Stage 2 MABR microaerobic tanks; hydraulic retention times of 4-5 h and 8-10 h for each stage of MABR-PN / DN tank and each stage of MABR microaerobic tank, respectively; operating time 2-3 days. Stage 2: Air supply pressure 10-25 kPa; DO concentration of 0.2-0.3 mg / L in Stage 1 MABR-PN / DN tank and 0.3-0.5 mg / L in Stage 2 MABR-PN / DN tank; DO concentration of 0.5-0.8 mg / L in Stage 1 MABR microaerobic tank. In the third stage, the air supply pressure is 10-25 kPa. The DO concentration in the first-stage MABR-PN / DN tank is 0.2-0.3 mg / L, and the DO concentration in the second-stage MABR-PN / DN tank is 0.25-0.45 mg / L. The DO concentration in the first-stage MABR-PN / DN tank is 0.5-0.8 mg / L, and the DO concentration in the second-stage MABR-PN / DN tank is 0.6-1.0 mg / L. The hydraulic retention times in the first-stage MABR-PN / DN tank and the second-stage MABR-PN / DN tank are 2-3 hours and 4-7 hours, respectively. The operating time is more than 7 days.

[0015] Furthermore, the MABR membrane box mainly consists of MABR membrane modules, membrane frames, gas supply connection pipes, exhaust gas collection and release pipes, and valves.

[0016] Furthermore, the ORP in each MABR-PN / DN pool is controlled at -80 to -20mV.

[0017] Furthermore, the ORP in each stage of the MABR micro-aerobic tank is controlled at +50~+150mV.

[0018] In some embodiments, when the water temperature is below 15°C, the total hydraulic retention time is extended by 15%-25%, and the DO of each MABR-PN / DN tank and each MABR micro-aerobic tank is increased by 10%-20%.

[0019] In some embodiments, when the COD concentration in the influent is ≤150mg / L and the ammonia nitrogen concentration is ≥50mg / L, the DO concentration in the first-stage MABR-PN / DN tank is increased to 0.35mg / L for operation.

[0020] In some embodiments, the sedimentation tank is equipped with a sludge return system, and the sludge return ratio is controlled between 0 and 50%.

[0021] This invention discloses a short-cut nitrification-denitrification coupled with microaerobic biological treatment method based on MABR, which is a highly efficient nitrogen removal method for low C / N wastewater. The method involves implanting a MABR membrane tank into a PN / DN tank and a microaerobic tank, using a microbial membrane grown on the outer surface of the MABR membrane filaments as a carrier to establish short-cut nitrification-denitrification and low-aerobic nitrification-denitrification processes. Simultaneously utilizing two stages of MABR-PN / DN tanks and two stages of MABR microaerobic tanks, without the need for an internal nitrification liquor recirculation system, nitrogen removal is improved under the same C / N ratio conditions, significantly saving carbon sources, reducing energy consumption, and decreasing sludge production; thus improving the effluent quality of urban wastewater treatment plants. This invention offers advantages such as good pollutant removal effect, saving on external carbon source addition, saving land area, short treatment cycle, low energy consumption, and reduced sludge production. Detailed Implementation

[0022] The present invention will be further described in conjunction with the embodiments.

[0023] Example 1: Wastewater treatment plant in a certain town with a treatment capacity of 2500m³ 3 / d, the influent C / N ratio is 2.8-3.5, and the effluent requirements are: the main water quality indicators meet the Class IV standard of the "Surface Water Environmental Quality Standard", of which COD≤30mg / L, ammonia nitrogen≤1.5mg / L, and total nitrogen≤10mg / L.

[0024] The specific steps of the short-cut nitrification-denitrification coupled microaerobic biochemical treatment method based on MABR are as follows:

[0025] S1 System Construction: The system mainly consists of two-stage MABR-PN / DN tanks, two-stage MABR micro-aerobic tanks, a sedimentation tank, an air supply system, and a monitoring system. MABR membrane tanks are implanted in the MABR-PN / DN tanks and the MABR micro-aerobic tanks, respectively. Wastewater is sequentially fed into the first-stage MABR-PN / DN tank, the first-stage MABR micro-aerobic tank, the second-stage MABR-PN / DN tank, the second-stage MABR micro-aerobic tank, and the sedimentation tank. The air supply system is set up separately and mainly includes air supply equipment, air supply pipelines, and valves, supplying gas to the first-stage MABR-PN / DN tank, the second-stage MABR-PN / DN tank, the first-stage MABR micro-aerobic tank, and the second-stage MABR micro-aerobic tank. Each air supply pipeline is equipped with a valve for control. The monitoring system monitors indicators including DO, ORP, NH3-N, and NO2. - -N, NO3 - -N, COD;

[0026] S2 Biofilm Initiation: Simultaneous inoculation of the two-stage MABR-PN / DN tank and the two-stage MABR micro-aerobic tank using mixed sludge from the aerobic section and sedimentation tank of the wastewater treatment plant, with a mixed sludge concentration of approximately 6.5 g / L; the air supply system is activated, water is intermittently introduced, and biofilm formation is carried out in stages.

[0027] In the first stage, the gas supply pressure is 10-40 kPa. The DO in the first-stage MABR-PN / DN tank and the second-stage MABR-PN / DN tank is 0.4-0.5 mg / L, such as 0.4, 0.45, 0.5 mg / L, etc. The DO in the first-stage MABR microaerobic tank and the second-stage MABR microaerobic tank is 0.5-1.0 mg / L, such as 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 mg / L, etc. The hydraulic retention time of each stage of MABR-PN / DN tank and each stage of MABR microaerobic tank is 4-5 h and 8-10 h, respectively, such as 4 h / 10 h (DO of MABR-PN / DN tank / DO of MABR microaerobic tank), 5 h / 10 h, 5 h / 9 h, 4 h / 9 h, 5 h / 8 h, etc. The running time is 2-3 days.

[0028] In the second stage, the gas supply pressure is 10-25 kPa, the DO in the first-stage MABR-PN / DN tank is 0.2-0.3 mg / L and the DO in the second-stage MABR-PN / DN tank is 0.3-0.5 mg / L, the DO in the first-stage MABR micro-aerobic tank is 0.5-0.8 mg / L and the DO in the second-stage MABR micro-aerobic tank is 0.6-1.0 mg / L, the hydraulic retention time of each stage of MABR-PN / DN tank and each stage of MABR micro-aerobic tank is 3-4 h and 4-8 h respectively, and the running time is 3-5 days.

[0029] In the third stage, the gas supply pressure is 10-25 kPa, the DO in the first-stage MABR-PN / DN tank is 0.2-0.3 mg / L and the DO in the second-stage MABR-PN / DN tank is 0.25-0.45 mg / L, the DO in the first-stage MABR micro-aerobic tank is 0.5-0.8 mg / L and the DO in the second-stage MABR micro-aerobic tank is 0.6-1.0 mg / L, the hydraulic retention time of each stage of MABR-PN / DN tank and each stage of MABR micro-aerobic tank is 2-3 h and 4-7 h respectively, and the running time is more than 7 days.

[0030] In the later stages of the third phase of operation, when NO2 - When the -N accumulation rate reaches 80% and remains so for 3 days or more, the MABR-PN / DN tank is considered to have successfully formed a biofilm; when the effluent COD is ≤50mg / L and remains so for 3 days or more, the MABR micro-aerobic tank is considered to have successfully formed a biofilm.

[0031] S3 operating parameter adjustment: After successful biofilm formation, operate the system. The effluent water quality should meet the discharge standards with TN≤10mg / L and COD≤30mg / L. Adjust the air supply pressure and flow rate to shorten the hydraulic retention time under the condition of meeting the effluent water quality requirements. The total hydraulic retention time should be controlled within 15 hours for stable operation.

[0032] In the above scheme, the MABR membrane boxes implanted in each stage of MABR-PN / DN tank and each stage of MABR micro-aerobic tank are mainly composed of MABR membrane modules, membrane frames, gas supply connection pipes, exhaust gas collection and release pipes, and valves; among them, 8 sets of MABR membrane boxes are put into the first stage MABR-PN / DN tank and 6 sets into the second stage MABR-PN / DN tank, respectively, and 10 sets of MABR membrane boxes are put into the first stage MABR micro-aerobic tank and 12 sets into the second stage MABR micro-aerobic tank, respectively.

[0033] The ORP in each MABR-PN / DN tank is controlled at -80~-20mV, and the ORP in each MABR micro-aerobic tank is controlled at +50~+150mV.

[0034] In the later stage of stable operation, the hydraulic retention time of each MABR-PN / DN tank and each MABR micro-aerobic tank was gradually shortened. The hydraulic retention time of the first-stage MABR-PN / DN tank and the second-stage MABR-PN / DN tank was shortened to 2h and 1.5h, respectively. The hydraulic retention time of the first-stage MABR micro-aerobic tank and the second-stage MABR micro-aerobic tank was shortened to 5.5h and 4h, respectively. The effluent quality met the requirements of TN≤10mg / L and COD≤30mg / L.

[0035] Example 2: During winter operation as in Example 1, with water temperature between 12℃ and 15℃, the total hydraulic retention time is extended by 15%-25%, for example, 15%, 20%, and 25%. The dissolved oxygen (DO) in each MABR-PN / DN tank and each MABR microaerobic tank is increased by 10%-20%, for example, 10%, 15%, and 20%. In the later stages of stable operation, the optimal operating conditions are: the hydraulic retention times in the first and second stage MABR-PN / DN tanks are extended to 2.5 hours and 1.8 hours, respectively; the hydraulic retention times in the first and second stage MABR microaerobic tanks are extended to 6.5 hours and 4.5 hours, respectively; simultaneously, a sludge return system for the sedimentation tank is added, with the sludge return ratio controlled at 30%-50%.

[0036] Example 3: During the operation of Example 1, when the influent C / N ratio is 2.8-3.0, and the COD ≤ 150 mg / L and the ammonia nitrogen concentration ≥ 50 mg / L, the impact on the wastewater treatment system is relatively large. In addition to implementing the method in Example 1, the DO of the first-stage MABR-PN / DN tank can be increased to 0.35 mg / L. At the same time, a sludge return system for the sedimentation tank is added, and the sludge return ratio is controlled at 30%-50%.

[0037] According to some embodiments of the present invention, after debugging, it was found that this system does not require the return of nitrified liquor from the MABR micro aerobic tank to the MABR-PN / DN tank. When the water temperature is below 15℃, the total hydraulic retention time is extended by 15%-25%, and the DO of each stage of MABR-PN / DN tank and each stage of MABR micro aerobic tank is increased by 10%-20% respectively. The sedimentation tank is equipped with a sludge return system, and the sludge return ratio is controlled at 0-50%. As for total phosphorus, according to the design requirements, a deep treatment unit is added to the subsequent process to remove phosphorus.

[0038] Based on the above embodiments, the optimal effluent quality reaches TN of 8.7 mg / L, COD of 24.6 mg / L, and NH3-N of 0.88 mg / L, and the effluent can be discharged into surface water bodies.

[0039] The MABR short-cut nitrification-denitrification coupled MABR micro-aerobic biochemical treatment method of the present invention has the following advantages:

[0040] (1) Under low C / N conditions, zero or minimal addition of external carbon sources can be achieved to increase the total nitrogen removal rate;

[0041] (2) Due to the high oxygen utilization rate and significantly reduced aeration volume of MABR technology, the biochemical treatment unit saves more than 40% of electricity;

[0042] (3) The coupled process has a short biological chain, and the sludge production of MABR technology is greatly reduced. For the same flow rate of treated water, the sludge production can be reduced by more than 30%.

[0043] (4) The MABR membrane box is directly placed into the tank, and no additional land is required in the renovation project. The newly built tank has a relatively small volume and has the advantage of small land area.

[0044] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A short-cut nitrification-denitrification coupled microaerobic biochemical treatment method based on MABR, characterized in that: The specific steps are as follows: S1 System Construction: The system mainly consists of two-stage MABR-PN / DN tanks, two-stage MABR micro-aerobic tanks, a sedimentation tank, an air supply system, and a monitoring system. MABR membrane tanks are implanted in the MABR-PN / DN tanks and the MABR micro-aerobic tanks respectively. Wastewater is sequentially passed through the first-stage MABR-PN / DN tank, the first-stage MABR micro-aerobic tank, the second-stage MABR-PN / DN tank, the second-stage MABR micro-aerobic tank, and the sedimentation tank. The air supply system is set up separately and supplies air to the MABR-PN / DN tanks and the MABR micro-aerobic tanks through pipelines. S2 Biofilm Initiation: Simultaneous inoculation of the two-stage MABR-PN / DN tank and the two-stage MABR micro-aerobic tank using mixed sludge from the aerobic section and sedimentation tank of the wastewater treatment plant; activating the air supply system, intermittently introducing water, and adjusting the air supply rate, dissolved oxygen (DO), and hydraulic retention time in stages; when NO2... - When the -N accumulation rate reaches 80% and remains so for more than 3 days, the MABR-PN / DN tank is considered to have successfully formed a biofilm; when the effluent COD is ≤50mg / L and remains so for more than 3 days, the MABR micro-aerobic tank is considered to have successfully formed a biofilm. S3 operating parameter adjustment: After successful biofilm formation, operate the system. The effluent water quality TN≤10mg / L and COD≤30mg / L meets the discharge standards. Adjust the air supply pressure and air supply flow rate to shorten the hydraulic retention time under the condition of meeting the effluent water quality requirements. The total hydraulic retention time is controlled within 15 hours for stable operation. The indicators monitored by the monitoring system in step S1 include DO, ORP, NH3-N, and NO2. - -N, NO3 - -N, COD; In step S1, the gas supply system mainly includes gas supply equipment, gas supply pipelines, and valves, which supply gas to the first-stage MABR-PN / DN tank, the second-stage MABR-PN / DN tank, the first-stage MABR micro-aerobic tank, and the second-stage MABR micro-aerobic tank, respectively. Each gas supply pipeline is equipped with a valve for control. In step S2, the mixed sludge is made by mixing aerobic activated sludge (3.5 g / L - 5 g / L) with sedimentation tank sludge, and the concentration of the mixed sludge is controlled not to exceed 7 g / L. The S2 step is divided into two stages: Stage 1: Air supply pressure 10-40 kPa; DO concentration of 0.4-0.5 mg / L in Stage 1 and Stage 2 MABR-PN / DN tanks; DO concentration of 0.5-1.0 mg / L in Stage 1 and Stage 2 MABR microaerobic tanks; hydraulic retention times of 4-5 h and 8-10 h for each stage of MABR-PN / DN tank and each stage of MABR microaerobic tank, respectively; operating time 2-3 days. Stage 2: Air supply pressure 10-25 kPa; DO concentration of 0.2-0.3 mg / L in Stage 1 MABR-PN / DN tank and 0.3-0.5 mg / L in Stage 2 MABR-PN / DN tank; DO concentration of 0.5-0.8 mg / L in Stage 1 MABR microaerobic tank. In the third stage, the air supply pressure is 10-25 kPa. The DO concentration in the first-stage MABR-PN / DN tank is 0.2-0.3 mg / L, and the DO concentration in the second-stage MABR-PN / DN tank is 0.25-0.45 mg / L. The DO concentration in the first-stage MABR-PN / DN tank is 0.5-0.8 mg / L, and the DO concentration in the second-stage MABR-PN / DN tank is 0.6-1.0 mg / L. The hydraulic retention times in the first-stage MABR-PN / DN tank and the second-stage MABR-PN / DN tank are 2-3 hours and 4-7 hours, respectively. The operating time is more than 7 days.

2. The method for short-cut nitrification-denitrification coupled with microaerobic biochemical treatment based on MABR according to claim 1, characterized in that: The MABR membrane box mainly consists of MABR membrane modules, membrane frame, gas supply connection pipe, exhaust gas collection and release pipe, and valves.

3. The method for short-cut nitrification-denitrification coupled with microaerobic biochemical treatment based on MABR according to claim 1, characterized in that: The ORP in each MABR-PN / DN pool is controlled at -80 to -20mV.

4. The method for short-cut nitrification-denitrification coupled with microaerobic biochemical treatment based on MABR according to claim 1, characterized in that: The ORP in each stage of the MABR micro-aerobic tank is controlled at +50~+150mV.

5. The method for short-cut nitrification-denitrification coupled with microaerobic biochemical treatment based on MABR according to claim 1, characterized in that: When the water temperature is below 15℃, the total hydraulic retention time is extended by 15%-25%, and the DO of each MABR-PN / DN tank and each MABR micro-aerobic tank is increased by 10%-20%.

6. The method for short-cut nitrification-denitrification coupled with microaerobic biochemical treatment based on MABR according to claim 1, characterized in that: When the influent COD concentration is ≤150mg / L and the ammonia nitrogen concentration is ≥50mg / L, the DO concentration of the first-stage MABR-PN / DN tank is increased to 0.35mg / L for operation.

7. The method for short-cut nitrification-denitrification coupled with microaerobic biochemical treatment based on MABR according to claim 1, characterized in that: The sedimentation tank is equipped with a sludge return system, and the sludge return ratio is controlled between 0-50%.