Efficient denitrification system and method based on two-stage MABR and application

Abstract

The invention belongs to the technical field of sewage treatment, and discloses a two-stage MABR-based efficient denitrification system, method and application, the system comprises an MABR-PN / DN reactor, an MABR-PN / A reactor, a peristaltic pump, an aeration hollow fiber membrane module, a carrier, an aeration pump, a gas flowmeter, a pressure gauge and a liquid flowmeter, and the MABR-PN / DN reactor and the MABR-PN / A reactor are arranged along the vertical direction. According to the system, the series design of the MABR-PN / DN and the MABR-PN / A is utilized, the adverse effect of organic matter in sewage on anaerobic ammonia oxidation treatment of high-concentration ammonia nitrogen wastewater is reduced, nitrate nitrogen generated by the MABR-PN / A flows back to the first-stage MABR-PN / DN to achieve denitrification, the denitrification limitation of a single reactor and a single denitrification path is broken through, and the overall total nitrogen removal rate of the system is higher than 90%.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and in particular to a high-efficiency denitrification system, method and application based on a two-stage MABR. Background Technology

[0002] A membrane aerated biofilm reactor (MABR) is a novel membrane-based wastewater treatment process. It utilizes a hydrophobic hollow fiber membrane to transfer oxygen to the wastewater treatment system, while simultaneously using a biofilm formed on the membrane surface to degrade pollutants in the wastewater. Membrane aeration can release fine bubbles or even achieve aeration without bubbles, resulting in high oxygen utilization and effectively reducing aeration energy consumption in wastewater treatment processes. Because oxygen is transferred from the inside of the membrane towards the solution, the biofilm achieves a stratified structure from the inside out, with aerobic and anoxic zones. The inner aerobic zone and the outer anoxic zone respectively promote the growth of nitrifying / nitrifying bacteria and denitrifying bacteria, enabling integrated nitrification and denitrification. Chinese patent CN119118362A discloses that the electron donor and acceptor in the MABR biofilm exhibit "reverse diffusion," making it easy to control the nitrification reaction and feasible to combine it with anaerobic ammonium oxidation.

[0003] Current research combines MABR with anammox to achieve efficient nitrogen removal from low-carbon, nitrogen-containing ammonia-nitrogen wastewater. However, within a single MABR unit, the PN / A process effluent contains nitrate nitrogen, making it difficult to exceed 90% total nitrogen removal rate. When denitrifying bacteria and anammox bacteria coexist, organic matter serves as both a necessary carbon source for denitrification and inhibits the activity of anammox bacteria, making effective coordination difficult. Existing MABR systems mostly employ single-stage designs or multi-stage series designs with a single nitrogen removal mechanism, failing to fundamentally address the limitations of a single nitrogen removal mechanism and the conflicting carbon source requirements of denitrification and anammox.

[0004] While increasing the number of tanks can improve nitrogen removal efficiency, it does not achieve deep coupling between different nitrogen removal pathways (such as PN / DN and PN / A). The conflict between carbon source balance and dissolved oxygen in the nitrogen removal system still exists.

[0005] The purpose of this invention is to reduce the inhibition of carbon source on anaerobic ammonium oxidation and further remove nitrate nitrogen produced by anaerobic ammonium oxidation. The reactor mainly based on short-cut nitrification and denitrification and the reactor mainly based on short-cut nitrification and anaerobic ammonium oxidation are connected in series and reflux is set up to make the total nitrogen removal rate higher than 90%. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a highly efficient denitrification system, method and application based on a two-stage MABR.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A high-efficiency denitrification system based on a two-stage MABR, the system comprising a first-stage MABR reactor (MABR-PN / DN reactor), a second-stage MABR reactor (MABR-PN / A reactor), a first peristaltic pump, a second peristaltic pump, a third peristaltic pump, a fourth peristaltic pump, a fifth peristaltic pump, a first aeration hollow fiber membrane module, a second aeration hollow fiber membrane module, a first carrier, a second carrier, a first aeration pump, a second aeration pump, a first gas flow meter, a second gas flow meter, a first pressure gauge, a second pressure gauge, a first liquid flow meter, and a second liquid flow meter, wherein both the MABR-PN / DN reactor and the MABR-PN / A reactor are arranged vertically;

[0009] The material in the MABR-PN / DN reactor flows into the MABR-PN / A reactor through the second peristaltic pump and the first liquid flow meter. The material in the MABR-PN / A reactor flows back into the MABR-PN / DN reactor through the fourth peristaltic pump and the second liquid flow meter to form a loop. The material in the MABR-PN / DN reactor flows back into the MABR-PN / DN reactor through the first peristaltic pump. The material in the MABR-PN / A reactor flows back into the MABR-PN / A reactor through the third peristaltic pump. The product material in the MABR-PN / A reactor is discharged through the fifth peristaltic pump. The first aeration hollow fiber membrane module and the first carrier are used to filter the material in the MABR-PN / DN reactor. The second aeration hollow fiber membrane module and the second carrier are used to filter the material in the MABR-PN / A reactor. The first aeration pump, the first gas flow meter, and the first pressure gauge are used to detect the parameters of the MABR-PN / DN reactor. The second aeration pump, the second gas flow meter, and the second pressure gauge are used to detect the parameters of the MABR-PN / A reactor.

[0010] Furthermore, the MABR-PN / DN reactor is a hollow, sealed structure. A first lower air inlet is tightly connected to the bottom of the MABR-PN / DN reactor, and a first upper air outlet is tightly connected to the top. Gas can enter the first aeration hollow fiber membrane module inside the MABR-PN / DN reactor through the first lower air inlet and exit outside the MABR-PN / DN reactor through the first upper air outlet. A first water inlet, a first upper internal reflux port, and a first external reflux port are connected to the upper part of the MABR-PN / DN reactor, and a first lower internal reflux port and a first water outlet are connected to the lower part of the MABR-PN / DN reactor. The return port and the first lower internal return port are connected through the first peristaltic pump. The first aeration hollow fiber membrane module is installed inside the MABR-PN / DN reactor. The first aeration hollow fiber membrane module includes an air inlet and an air outlet. The air inlet of the first aeration hollow fiber membrane module is tightly connected to the first lower air inlet. The air outlet of the first aeration hollow fiber membrane module is tightly connected to the first upper air outlet. The first aeration hollow fiber membrane module inside the MABR-PN / DN reactor is filled with a first carrier for fixing denitrifying bacteria. The first inlet can be used to introduce wastewater to be treated. The wastewater to be treated flows into the MABR-PN / DN reactor from the first inlet and flows out of the reactor from the first outlet.

[0011] The MABR-PN / A reactor has a second lower air inlet at the bottom and a second upper air outlet at the top. The upper part of the MABR-PN / A reactor has a second water inlet and a second upper internal reflux inlet. The lower part of the MABR-PN / A reactor has a second lower internal reflux inlet, a second external reflux inlet, and a second water outlet. The second upper internal reflux inlet and the second lower internal reflux inlet are connected via a third peristaltic pump. The second aeration hollow fiber membrane module is installed inside the hollow interior of the MABR-PN / A reactor. The second aeration hollow fiber membrane module includes an air inlet and an air outlet. The air inlet of the second aeration hollow fiber membrane module is tightly connected to the second lower air inlet, and the air outlet of the second aeration hollow fiber membrane module is tightly connected to the second upper air outlet. A second carrier is filled on the second aeration hollow fiber membrane module inside the MABR-PN / A reactor to immobilize anaerobic ammonia-oxidizing bacteria. The second water outlet is connected to a fifth peristaltic pump to discharge the treated water from the reactor.

[0012] The first lower air inlet of the MABR-PN / DN reactor is also connected to a first aeration pump, a first gas flow meter, and a first pressure gauge. The first gas flow meter is used to monitor the air flow rate, and the first pressure gauge is used to monitor the aeration pressure.

[0013] The second lower air inlet of the MABR-PN / A reactor is also connected to a second aeration pump, a second gas flow meter, and a second pressure gauge. The second gas flow meter is used to monitor the air flow rate, and the second pressure gauge is used to monitor the aeration pressure.

[0014] The first outlet of the MABR-PN / DN reactor and the second inlet of the MABR-PN / A reactor are tightly connected through a second peristaltic pump and a first liquid flow meter. The second external reflux port of the MABR-PN / A reactor and the first external reflux port are tightly connected through a fourth peristaltic pump and a second liquid flow meter to achieve reflux flow control.

[0015] Furthermore, both the first aeration hollow fiber membrane module and the second aeration hollow fiber membrane module are microporous hollow fiber aeration membranes or non-porous hollow fiber aeration membranes.

[0016] Furthermore, the microporous hollow fiber aeration membrane is made of PVDF, PTFE, or PE, with a pore size of 0.01~0.2μm; the non-porous hollow fiber aeration membrane is made of non-porous silicone rubber.

[0017] Furthermore, the carrier is a sponge packing, a combination packing, or an elastic packing.

[0018] A highly efficient denitrification method utilizing the two-stage MABR-based high-efficiency denitrification system described above includes the following steps:

[0019] 1) Start-up phase

[0020] The MABR-PN / DN reactor does not have a first carrier. The first-stage MABR reactor, i.e., the MABR-PN / DN reactor, is inoculated with nitrifying sludge at a MLSS concentration of 3000-5000 mg / L. NH4Cl is then introduced to increase the NH4 content of the solution. + The nitrite concentration is 100 mg / L. The pH is adjusted to 7.5-8.0 with NaHCO3, and the dissolved oxygen is controlled at 1.0-1.2 mg / L. The hydraulic retention time is controlled by adjusting the influent flow rate, and the dissolved oxygen in the reactor is controlled by adjusting the aeration pressure. The reactor is operated until the nitrite accumulation rate in the effluent exceeds 90%, and a significant biofilm forms on the membrane surface. The sludge-water mixture is then poured out, and denitrifying sludge is inoculated with a sludge concentration (MLSS) of 3000-5000 mg / L. Simultaneously, the first carrier of the MABR-PN / DN reactor is added, with a filling rate of 15-45%. NH4Cl and glucose are introduced to increase the NH4 content in the solution. + Start-up is considered successful when the nitrogen concentration is 100 mg / L, the COD is 200 mg / L, the pH is adjusted to 7.5-8.0 with NaHCO3, the dissolved oxygen is controlled at 0.3-0.5 mg / L, and the total nitrogen removal rate is >50%.

[0021] The MABR-PN / A reactor does not use a second carrier. The second-stage MABR reactor, i.e., the MABR-PN / A reactor, is inoculated with nitrifying sludge at a MLSS concentration of 3000-5000 mg / L. NH4Cl is then introduced to increase the NH4 content of the solution. + The nitrogen (N) concentration is 100 mg / L. The pH is adjusted to 7.5–8.0 with NaHCO3, and the dissolved oxygen is controlled at 1.0–1.2 mg / L. The hydraulic retention time is controlled by adjusting the influent flow rate, and the dissolved oxygen in the reactor is controlled by adjusting the aeration pressure. The reactor is operated until the nitrite accumulation rate in the effluent exceeds 90%, and a significant biofilm forms on the membrane surface. The mud-water mixture is then poured out, and anaerobic ammonia-oxidizing bacteria with a VSS of 4000–5000 mg / L are inoculated. Simultaneously, the second carrier of the MABR-PN / A reactor is added, with a filling rate of 15–45%. NH4Cl is then introduced to increase the NH4+ concentration in the solution. + Start-up was completed when the TN removal rate was >80% for 10 consecutive days, with a TN concentration of 100 mg / L, dissolved oxygen <0.2 mg / L, temperature 30-35℃.

[0022] 2) Operational Phase

[0023] The first-stage MABR reactor, namely the MABR-PN / DN reactor, controls the dissolved oxygen at 0.3~0.5 mg / L, the hydraulic retention time at 5~10 h, and the temperature at 15~35℃.

[0024] The second-stage MABR reactor, namely the MABR-PN / A reactor, controls dissolved oxygen to <0.2 mg / L, with the same hydraulic retention time as the first-stage MABR reactor, and a temperature of 30-35℃. Every 5-15 days, a trace amount of hydroxylamine with a final concentration of 0.5 mg / L is added to promote the activity of anaerobic ammonia oxidizing bacteria.

[0025] Connect the first-stage MABR reactor and the second-stage MABR reactor, and adjust the reflux ratio to 50~150%.

[0026] Furthermore, in step 2), the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of the first-stage MABR reactor is greater than 1:1.32.

[0027] The application of the efficient denitrification method described above in the treatment of ammonia nitrogen-containing wastewater with a low carbon-to-nitrogen ratio.

[0028] The application of the high-efficiency denitrification system based on a two-stage MABR, as described above, in the treatment of ammonia nitrogen-containing wastewater with a low carbon-to-nitrogen ratio.

[0029] The advantages and positive effects of this invention are as follows:

[0030] 1. The system of this invention utilizes the series design of MABR-PN / DN and MABR-PN / A to reduce the adverse effects of organic matter in wastewater on the treatment of high-concentration ammonia nitrogen wastewater by anaerobic ammonia oxidation, and recycles the nitrate nitrogen generated by MABR-PN / A to the first-stage MABR-PN / DN to achieve denitrification, breaking through the denitrification limitations of a single reactor and a single denitrification path. The overall total nitrogen removal rate of the system is higher than 90%.

[0031] 2. The system of this invention utilizes the stratified structure of the aerobic and anoxic zones of the biofilm on the aeration membrane to achieve short-cut nitrification / denitrification and short-cut nitrification / anaerobic ammonia oxidation, thereby achieving the targeted enrichment of microbial communities. This allows aerobic and anaerobic microorganisms to coexist in the same reactor, with the substrate and product coordinating with each other, improving treatment efficiency and reducing the footprint of the device.

[0032] 3. The system of this invention utilizes the high oxygen utilization rate and precise control of aeration volume of the aeration membrane in MABR to achieve short-range nitrification control, and the nitrite accumulation rate of MABR reaches more than 90%.

[0033] 4. In the method of the present invention, the first-stage MABR reactor removes nitrate nitrogen from the reflux liquid and nitrite nitrogen produced by short-cut nitrification of ammonia nitrogen in the influent through denitrification, while removing a small amount of organic matter in the influent, thereby reducing the adverse effects of organic matter on the second-stage anaerobic ammonia oxidizing bacteria. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structural connection of the high-efficiency denitrification reactor based on a two-stage MABR in this invention.

[0035] Figure reference numerals: 1-1. MABR-PN / DN reactor, 1-2. MABR-PN / A reactor, 2-1. First inlet, 2-2. First outlet, 2-3. First upper internal reflux port, 2-4. First lower internal reflux port, 2-5. First external reflux port, 2-6. Second inlet, 2-7. Second outlet, 2-8. Second upper internal reflux port, 2-9. Second lower internal reflux port, 2-10. Second external reflux port, 3-1. First peristaltic pump, 3-2. Second peristaltic pump, 3-3. Third peristaltic pump, 3-4. Fourth peristaltic pump, 3 -5. Fifth peristaltic pump; 4-1. First aeration hollow fiber membrane module; 4-2. Second aeration hollow fiber membrane module; 5-1. First carrier; 5-2. Second carrier; 6-1. First pressure gauge; 6-2. Second pressure gauge; 7-1. First gas flow meter; 7-2. Second gas flow meter; 8-1. First aeration pump; 8-2. Second aeration pump; 9-1. First lower air inlet; 9-2. First upper air outlet; 9-3. Second lower air inlet; 9-4. Second upper air outlet; 10-1. First liquid flow meter; 10-2. Second liquid flow meter. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0037] Unless otherwise specified, all raw materials used in this invention are commercially available products. Unless otherwise specified, all methods used in this invention are conventional methods in the field. All substances used in this invention are of conventional mass. Structures, connections, etc., not described in detail in this invention can be understood as conventional techniques in the field.

[0038] A highly efficient nitrogen removal system based on a two-stage MABR, such as Figure 1 As shown, the system includes a first-stage MABR reactor, namely MABR-PN / DN reactor 1-1, a second-stage MABR reactor, namely MABR-PN / A reactor 1-2, a first peristaltic pump 3-1, a second peristaltic pump 3-2, a third peristaltic pump 3-3, a fourth peristaltic pump 3-4, a fifth peristaltic pump 3-5, a first aeration hollow fiber membrane module 4-1, a second aeration hollow fiber membrane module 4-2, a first carrier 5-1, a second carrier 5-2, a first aeration pump 8-1, a second aeration pump 8-2, a first gas flow meter 7-1, a second gas flow meter 7-2, a first pressure gauge 6-1, a second pressure gauge 6-2, a first liquid flow meter 10-1, and a second liquid flow meter 10-2. Both the MABR-PN / DN reactor and the MABR-PN / A reactor are arranged vertically.

[0039] The MABR-PN / DN reactor 1-1 is a hollow, sealed structure. A first lower air inlet 9-1 is tightly connected to the bottom of the MABR-PN / DN reactor 1-1, and a first upper air outlet 9-2 is tightly connected to the top of the MABR-PN / DN reactor 1-1. Gas can enter the first aeration hollow fiber membrane module 4-1 inside the MABR-PN / DN reactor 1-1 through the first lower air inlet 9-1 and exit outside the MABR-PN / DN reactor 1-1 through the first upper air outlet 9-2. A first water inlet 2-1, a first upper internal reflux inlet 2-3, and a first external reflux inlet 2-5 are connected to the upper part of the MABR-PN / DN reactor 1-1. A first lower internal reflux inlet 2-4 and a first water outlet 2-2 are connected to the lower part of the MABR-PN / DN reactor 1-1. The first upper internal reflux inlet 2-3 is connected to... The first lower internal return port 2-4 is connected to the first peristaltic pump 3-1 to achieve full mixing of the liquid in the reactor. The first aeration hollow fiber membrane module 4-1 is installed inside the MABR-PN / DN reactor 1-1. The first aeration hollow fiber membrane module 4-1 includes an air inlet and an air outlet. The air inlet of the first aeration hollow fiber membrane module is tightly connected to the first lower air inlet 9-1, and the air outlet of the first aeration hollow fiber membrane module is tightly connected to the first upper air outlet 9-2. The first carrier 5-1 is filled on the first aeration hollow fiber membrane module 4-1 inside the MABR-PN / DN reactor 1-1 to fix denitrifying bacteria. The first water inlet 2-1 can be used to introduce wastewater to be treated. The wastewater to be treated flows into the MABR-PN / DN reactor 1-1 from the first water inlet 2-1 and flows out of the reactor from the first water outlet 2-2.

[0040] The MABR-PN / A reactor 1-2 has a second lower air inlet 9-3 at its bottom and a second upper air outlet 9-4 at its top. The upper part of the MABR-PN / A reactor has a second water inlet 2-6 and a second upper internal reflux inlet 2-8. The lower part of the MABR-PN / A reactor 1-2 has a second lower internal reflux inlet 2-9, a second external reflux inlet 2-10, and a second water outlet 2-7. The second upper internal reflux inlet 2-8 and the second lower internal reflux inlet 2-9 are connected by a third peristaltic pump 3-3 to achieve thorough mixing of the liquid within the reactor. The second aeration hollow fiber... The second aeration hollow fiber membrane module 4-2 is installed inside the hollow cavity of the MABR-PN / A reactor 1-2. The second aeration hollow fiber membrane module 4-2 includes an air inlet and an air outlet. The air inlet of the second aeration hollow fiber membrane module is tightly connected to the second lower air inlet 9-3, and the air outlet of the second aeration hollow fiber membrane module is tightly connected to the second upper air outlet 9-4. The second carrier 5-2 is filled on the second aeration hollow fiber membrane module 4-2 inside the MABR-PN / A reactor 1-2 for fixing anaerobic ammonia oxidizing bacteria. The second water outlet 2-7 is connected to the fifth peristaltic pump 3-5 to discharge the treated water from the reactor.

[0041] The first lower air inlet 9-1 of the MABR-PN / DN reactor is also connected to the first aeration pump 8-1, the first gas flow meter 7-1, and the first pressure gauge 6-1. The first gas flow meter 7-1 is used to monitor the aeration rate, and the first pressure gauge 6-1 is used to monitor the aeration pressure, so as to achieve precise aeration and establish a short-cut nitrification process.

[0042] The second lower air inlet 9-3 of the MABR-PN / A reactor 1-2 is also connected to the second aeration pump 8-2, the second gas flow meter 7-2, and the second pressure gauge 6-2. The second gas flow meter 7-2 is used to monitor the aeration rate, and the second pressure gauge 6-2 is used to monitor the aeration pressure, so as to achieve precise aeration and establish a short-cut nitrification process.

[0043] The first outlet 2-2 of the MABR-PN / DN reactor 1-1 and the second inlet 2-6 of the MABR-PN / A reactor are tightly connected through the second peristaltic pump 3-2 and the first liquid flow meter 10-1. The second external return port 2-5 and the second external return port 2-10 of the MABR-PN / A reactor 1-2 are tightly connected through the fourth peristaltic pump 3-4 and the second liquid flow meter 10-2 to achieve return liquid flow control.

[0044] After the wastewater to be treated enters the MABR-PN / DN reactor, the first aeration pump and the first peristaltic pump are turned on to adjust the aeration rate and establish a short-cut nitrification and denitrification process, reducing the organic matter in the wastewater and controlling the ratio of ammonia nitrogen and nitrite to reduce the COD in the reactor to below 70 mg / L and the mass ratio of ammonia nitrogen to nitrite nitrogen to be greater than 1:1.32. The second peristaltic pump is turned on to allow the effluent from the MABR-PN / DN reactor to enter the MABR-PN / A reactor. The second aeration pump and the third peristaltic pump are turned on to adjust the aeration rate and establish a short-cut nitrification and anaerobic ammonium oxidation process, achieving deep denitrification of the wastewater. The fourth peristaltic pump is turned on to allow the water treated in the MABR-PN / A reactor to flow back to the MABR-PN / DN reactor. The denitrification reaction in the MABR-PN / DN reactor consumes the nitrate generated by the anaerobic ammonium oxidation reaction in the MABR-PN / A reactor. The fifth peristaltic pump is turned on to discharge the water treated in the MABR-PN / A reactor.

[0045] In this embodiment, the first aeration hollow fiber membrane module 4-1 and the second aeration hollow fiber membrane module 4-2 are both microporous hollow fiber aeration membranes or non-porous hollow fiber aeration membranes. Membrane aeration has the characteristics of high oxygen utilization rate and precise control of aeration volume, which can effectively achieve short-range nitrification control.

[0046] Preferably, the microporous hollow fiber aeration membrane is made of PVDF, PTFE, or PE, with a pore size of 0.01~0.2μm; the non-porous hollow fiber aeration membrane is made of non-porous silicone rubber.

[0047] The two-stage MABR high-efficiency denitrification system described above is applied in the treatment of ammonia nitrogen-containing wastewater with low carbon-to-nitrogen ratio.

[0048] Example 1

[0049] A high-efficiency nitrogen removal system based on a two-stage MABR, with the same structural connections as above, specifically: the first-stage MABR-PN / DN reactor has a volume of 5 L, and the first aeration hollow fiber membrane module is a microporous hollow fiber aeration membrane made of PVDF material with a pore size of 0.2 μm, and the membrane area of ​​the module is 0.3 m². 2 The first carrier is polyurethane sponge filler with a filling rate of 30%, and the volume of the MABR-PN / A reactor is 5 L. The second aeration hollow fiber membrane module is a microporous hollow fiber aeration membrane made of PVDF material with a pore size of 0.2 μm, and the membrane area of ​​the module is 0.3 m². 2 The second carrier is polyurethane sponge filler with a filling rate of 30%.

[0050] Example 2: High-efficiency denitrification method

[0051] A high-efficiency denitrification method based on a two-stage MABR is proposed. This method utilizes the high-efficiency denitrification reactor based on a two-stage MABR as described in Example 1 for denitrification, and includes the following steps:

[0052] 1) Start-up phase

[0053] The first-stage MABR-PN / DN reactor is inoculated with nitrifying sludge (MLSS 3500 mg / L), and NH4Cl is introduced. + The nitrogen concentration was 100 mg / L. The pH was adjusted to 8 with NaHCO3. The aeration flow meter and aeration pressure were adjusted to control dissolved oxygen at 1.0 mg / L. The hydraulic retention time was controlled at 18 hours. After 20 days of operation, the nitrite nitrogen to total nitrate nitrogen ratio in the effluent was higher than 90%, and a significant biofilm formed on the membrane surface. The sludge-water mixture was poured off, and denitrifying sludge (MLSS 3000 mg / L) was inoculated. Simultaneously, a polyurethane carrier was added, with a filling rate of 30%. A mixed solution of NH4Cl and glucose was introduced. + The nitrogen (TN) concentration was set at 100 mg / L, the COD at 200 mg / L, and the pH was adjusted to 8.0 with NaHCO3. The aeration flow meter and aeration pressure were adjusted to maintain dissolved oxygen at 0.5 mg / L and the hydraulic retention time at 8 hours. After 30 days, the TN removal rate reached 55%, indicating successful startup.

[0054] The second-stage MABR-PN / A reactor is inoculated with nitrifying sludge (MLSS 3500 mg / L), and NH4Cl is introduced. + The nitrogen concentration was 100 mg / L, the pH was adjusted to 8 with NaHCO3, the aeration flow meter and aeration pressure were adjusted, the dissolved oxygen was controlled at 1.0 mg / L, and the hydraulic retention time was controlled at 18 h. After 20 hours of operation, the nitrite nitrogen in the effluent accounted for more than 90% of the total nitrate nitrogen mass, and a significant biofilm formed on the membrane surface. The sludge-water mixture was poured off, and anaerobic ammonia-oxidizing bacteria (VSS 4000 mg / L) were inoculated, along with a polyurethane carrier. The filling rate was 30%, and NH4Cl and NH4 were introduced. + With a nitrogen concentration of 100 mg / L, the aeration flow meter and aeration pressure were adjusted to control dissolved oxygen at 0.1 mg / L, temperature at 32℃, and hydraulic retention time at 8 hours. After 30 days, the TN removal rate reached 82% for 10 consecutive days, indicating successful startup. A trace amount of hydroxylamine (0.5 mg / L) was added every 15 days to promote the activity of anaerobic ammonia-oxidizing bacteria.

[0055] 2) Operational Phase

[0056] The first stage MABR-PN / DN reactor: The influent is simulated high-ammonia nitrogen wastewater prepared with a mixture of NH4Cl and glucose. +The concentration of nitrogen (N) was 100 mg / L, the concentration of COD was 150 mg / L, the pH was adjusted to 8 with NaHCO3, the aeration flow meter and aeration pressure were adjusted, the dissolved oxygen was controlled to 0.5 mg / L, the hydraulic retention time was controlled to 8 h, and the temperature was 25℃.

[0057] The second-stage MABR-PN / A reactor: The influent is the effluent from the first-stage MABR-PN / DN reactor, with dissolved oxygen of 0.2 mg / L. The hydraulic retention time is 8 hours, the temperature is 32℃, and the reflux ratio is 50%.

[0058] The stable operating water quality parameters are shown in Table 1. After the first-stage MABR-PN / DN treatment, the COD of the system decreased from 150 mg / L in the influent to 60-65 mg / L. Therefore, the inhibitory effect of organic matter on the anaerobic ammonia oxidation reaction in the second-stage MABR-PN / A was significantly reduced, and the total nitrogen removal rate of the system was higher than 92%.

[0059] Table 1. Effluent quality of each stage of the two-stage MABR in Example 2

[0060]

[0061] Comparative Example 1

[0062] The ammonia-nitrogen-containing wastewater was treated using the same first-stage MABR-PN / DN reactor as in Example 2, but not in conjunction with the second-stage MABR-PN / A reactor. All other steps were the same as in Example 2.

[0063] Simulated high-ammonia nitrogen wastewater was prepared by mixing NH4Cl and glucose. + The concentration of nitrogen (N) was 100 mg / L, the COD was 150 mg / L, the pH was adjusted to 8 with NaHCO3, the dissolved oxygen was controlled to 0.5 mg / L by aeration flow rate and aeration pressure, the hydraulic retention time was 16 h, and the temperature was 25℃.

[0064] The stable operating water quality parameters are shown in Table 2. Due to the low influent carbon-to-nitrogen ratio (1.5:1), the denitrification reaction in the MABR-PN / DN reactor suffers from insufficient carbon source, resulting in a total nitrogen removal rate of only about 50%.

[0065] Table 2. Influent and effluent water quality in Comparative Example 1

[0066]

[0067] Comparative Example 2

[0068] The treatment was carried out using the same second-stage MABR-PN / A reactor as in Example 2, but not in conjunction with the first-stage MABR-PN / DN reactor. All other steps were the same as in Example 2.

[0069] Simulated high-ammonia nitrogen wastewater was prepared by mixing NH4Cl and glucose. + The concentration of nitrogen (N) was 100 mg / L, the COD was 150 mg / L, the pH was adjusted to 8 with NaHCO3, the dissolved oxygen was controlled at 0.1 mg / L by aeration flow rate and aeration pressure, the hydraulic retention time was 16 h, and the temperature was 32℃.

[0070] The stable operating water quality parameters are shown in Table 3. Due to the inhibition of the anaerobic ammonia oxidation process in the MABR-PN / A reactor by COD, the total nitrogen removal rate of the system is less than 20%.

[0071] Meanwhile, by comparing Example 2, Comparative Example 1 and Comparative Example 2, it can be seen that the first-stage MABR reactor, namely the MABR-PN / DN reactor, and the second-stage MABR reactor, namely the MABR-PN / A reactor, have a synergistic effect, which can synergistically improve the denitrification effect of the prepared high-efficiency denitrification system on ammonia nitrogen-containing wastewater.

[0072] Table 3. Influent and effluent water quality in Comparative Example 2

[0073]

[0074] Comparative Example 3

[0075] Using the same second-stage MABR-PN / A reactor as in Example 2, a two-stage series MABR-PN / A process was constructed to treat ammonia nitrogen-containing wastewater.

[0076] Simulated high-ammonia nitrogen wastewater was prepared by mixing NH4Cl and glucose. + The concentration of nitrogen (N) was 100 mg / L, the COD was 150 mg / L, the pH was adjusted to 8 with NaHCO3, the dissolved oxygen was controlled at 0.1 mg / L by aeration flow rate and aeration pressure, the single-stage hydraulic retention time was 8 h, and the temperature was 32℃.

[0077] The stable operating water quality parameters are shown in Table 4. In the two-stage MABR-PN / A system, the first-stage anaerobic ammonia oxidation was significantly inhibited by COD, with a total nitrogen removal rate of only 10%. In the second stage, the COD concentration was slightly lower than that in the first stage, and the inhibition of anaerobic ammonia oxidation also decreased. However, overall, the two-stage MABR-PN / A system in series was still significantly affected by COD, with a total nitrogen removal rate of less than 50%, lower than that of the MABR-PN / DN and MABR-PN / A series systems.

[0078] Table 4. Water quality of each effluent level in Comparative Example 3

[0079]

[0080] Meanwhile, by comparing Example 2, Comparative Example 1 and Comparative Example 2-3, it can be seen that the first-stage MABR reactor, namely the MABR-PN / DN reactor, and the second-stage MABR reactor, namely the MABR-PN / A reactor, have a synergistic effect, which can synergistically improve the denitrification effect of the prepared high-efficiency denitrification system on ammonia nitrogen-containing wastewater.

[0081] Therefore, the present invention is based on a two-stage MABR high-efficiency denitrification reactor and method, which has the characteristics of high denitrification rate, reduced aeration energy consumption and low carbon source requirement, and is suitable for the treatment of wastewater with high ammonia nitrogen and low carbon-to-nitrogen ratio.

[0082] The system of this invention utilizes the series design of MABR-PN / DN and MABR-PN / A to reduce the adverse effects of organic matter in wastewater on the treatment of high-concentration ammonia nitrogen wastewater by anaerobic ammonia oxidation. The system also achieves denitrification of the nitrate nitrogen reflux liquid generated by MABR-PN / A in the first-stage MABR-PN / DN, breaking through the denitrification limitations of a single reactor and a single denitrification path. The overall total nitrogen removal rate of the system is higher than 90%.

[0083] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A high-efficiency nitrogen removal system based on a two-stage MABR, characterized in that: The system includes a first-stage MABR reactor, namely the MABR-PN / DN reactor (1-1), a second-stage MABR reactor, namely the MABR-PN / A reactor (1-2), a first peristaltic pump (3-1), a second peristaltic pump (3-2), a third peristaltic pump (3-3), a fourth peristaltic pump (3-4), a fifth peristaltic pump (3-5), a first aeration hollow fiber membrane module (4-1), a second aeration hollow fiber membrane module (4-2), a first carrier (5-1), a second carrier (5-2), a first aeration pump (8-1), a second aeration pump (8-2), a first gas flow meter (7-1), a second gas flow meter (7-2), a first pressure gauge (6-1), a second pressure gauge (6-2), a first liquid flow meter (10-1), and a second liquid flow meter (10-2). Both the MABR-PN / DN reactor (1-1) and the MABR-PN / A reactor (1-2) are arranged vertically. The material in the MABR-PN / DN reactor (1-1) flows into the MABR-PN / A reactor (1-2) through the second peristaltic pump (3-2) and the first liquid flow meter (10-1). The material in the MABR-PN / A reactor (1-2) flows back into the MABR-PN / DN reactor (1-1) through the fourth peristaltic pump (3-4) and the second liquid flow meter (10-2), forming a loop. The material in the MABR-PN / DN reactor (1-1) flows back into the MABR-PN / DN reactor (1-1) through the first peristaltic pump (3-1). The material in the MABR-PN / A reactor (1-2) flows back into the MABR-PN / A reactor (1-2) through the third peristaltic pump (3-3). The product material in the BR-PN / A reactor (1-2) is discharged through the fifth peristaltic pump (3-5). The first aeration hollow fiber membrane module (4-1) and the first carrier (5-1) are used to filter the material in the MABR-PN / DN reactor (1-1). The second aeration hollow fiber membrane module (4-2) and the second carrier (5-2) are used to filter the material in the MABR-PN / A reactor (1-2). The first aeration pump (8-1), the first gas flow meter (7-1), and the first pressure gauge (6-1) are used to detect the parameters of the MABR-PN / DN reactor (1-1). The second aeration pump (8-2), the second gas flow meter (7-2), and the second pressure gauge (6-2) are used to detect the parameters of the MABR-PN / A reactor (1-2).

2. The high-efficiency nitrogen removal system based on a two-stage MABR according to claim 1, characterized in that: The MABR-PN / DN reactor (1-1) is a hollow, sealed structure. A first lower air inlet (9-1) is tightly connected to the bottom of the MABR-PN / DN reactor (1-1), and a first upper air outlet (9-2) is tightly connected to the top of the MABR-PN / DN reactor (1-1). Gas can enter the first aeration hollow fiber membrane module (4-1) inside the MABR-PN / DN reactor (1-1) through the first lower air inlet (9-1) and exit the MABR-PN / DN reactor (1-1) through the first upper air outlet (9-2). A first water inlet (2-1), a first upper internal reflux inlet (2-3), and a first external reflux inlet (2-5) are connected to the upper part of the MABR-PN / DN reactor (1-1). A first lower internal reflux inlet (2-4) and a first water outlet (2-2) are connected to the lower part of the MABR-PN / DN reactor (1-1). The return port (2-3) and the first lower internal return port (2-4) are connected through the first peristaltic pump (3-1). The first aeration hollow fiber membrane module (4-1) is installed inside the MABR-PN / DN reactor (1-1). The first aeration hollow fiber membrane module (4-1) includes an air inlet and an air outlet. The air inlet of the first aeration hollow fiber membrane module is tightly connected to the first lower air inlet (9-1). The air outlet of the first aeration hollow fiber membrane module is tightly connected to the first upper air outlet (9-2). The first carrier (5-1) inside the MABR-PN / DN reactor (1-1) is filled with a first carrier (5-1) for fixing denitrifying bacteria. The first inlet can be used to introduce wastewater to be treated. The wastewater to be treated flows into the MABR-PN / DN reactor (1-1) from the first inlet and flows out of the MABR-PN / DN reactor (1-1) from the first outlet (2-2). The MABR-PN / A reactor (1-2) has a second lower air inlet (9-3) at its bottom and a second upper air outlet (9-4) at its top. The upper part of the MABR-PN / A reactor (1-2) has a second water inlet (2-6) and a second upper internal reflux inlet (2-8). The lower part of the MABR-PN / A reactor (1-2) has a second lower internal reflux inlet (2-9), a second external reflux inlet (2-10), and a second water outlet (2-7). The second upper internal reflux inlet (2-8) and the second lower internal reflux inlet (2-9) are connected via a third peristaltic pump (3-3). The second aeration hollow fiber membrane module (4- 2) Installed inside the hollow interior of the MABR-PN / A reactor (1-2), the second aeration hollow fiber membrane module (4-2) includes an air inlet and an air outlet. The air inlet of the second aeration hollow fiber membrane module (4-2) is tightly connected to the second lower air inlet (9-3), and the air outlet of the second aeration hollow fiber membrane module (4-2) is tightly connected to the second upper air outlet (9-4). The second carrier (5-2) inside the MABR-PN / A reactor (1-2) is filled with a second carrier (5-2) for fixing anaerobic ammonia oxidizing bacteria. The second water outlet (2-7) is connected to the fifth peristaltic pump (3-5) to discharge the treated water from the reactor. The first lower air inlet (9-1) of the MABR-PN / DN reactor (1-1) is also connected to the first aeration pump (8-1), the first gas flow meter (7-1), and the first pressure gauge (6-1). The first gas flow meter (7-1) is used to monitor the air flow rate, and the first pressure gauge (6-1) is used to monitor the aeration pressure. The second lower air inlet (9-3) under the MABR-PN / A reactor (1-2) is also connected to the second aeration pump (8-2), the second gas flow meter (7-2), and the second pressure gauge (6-2). The second gas flow meter (7-2) is used to monitor the air flow rate, and the second pressure gauge (6-2) is used to monitor the aeration pressure. The first outlet (2-2) of the MABR-PN / DN reactor (1-1) and the second inlet (2-6) of the MABR-PN / A reactor are tightly connected through a second peristaltic pump (3-2) and a first liquid flow meter (10-1). The second external return port (2-10) of the MABR-PN / A reactor (1-2) and the first external return port (2-5) are tightly connected through a fourth peristaltic pump (3-4) and a second liquid flow meter (10-2) to achieve control of the return liquid flow rate.

3. The high-efficiency nitrogen removal system based on a two-stage MABR according to claim 1, characterized in that: The first aeration hollow fiber membrane module (4-1) and the second aeration hollow fiber membrane module (4-2) are both microporous hollow fiber aeration membranes or non-porous hollow fiber aeration membranes.

4. The high-efficiency denitrification system based on a two-stage MABR according to claim 3, characterized in that: The microporous hollow fiber aeration membrane is made of PVDF, PTFE, or PE, with a pore size of 0.01~0.2μm; the non-porous hollow fiber aeration membrane is made of non-porous silicone rubber.

5. The high-efficiency nitrogen removal system based on a two-stage MABR according to claim 1, characterized in that: Both the first carrier (5-1) and the second carrier (5-2) are sponge packing, combined packing, or elastic packing.

6. A highly efficient denitrification method utilizing a two-stage MABR-based high-efficiency denitrification system as described in any one of claims 1 to 5, characterized in that: Includes the following steps: 1) Start-up phase The MABR-PN / DN reactor (1-1) does not have a first carrier. The first-stage MABR reactor, i.e., the MABR-PN / DN reactor (1-1), is inoculated with nitrifying sludge. The sludge concentration (MLSS) is 3000-5000 mg / L. NH4Cl is introduced to make the solution NH4+. + The nitrite concentration was 100 mg / L. The pH was adjusted to 7.5-8.0 with NaHCO3, and the dissolved oxygen was controlled at 1.0-1.2 mg / L. The hydraulic retention time was controlled by adjusting the influent flow rate, and the dissolved oxygen in the reactor was controlled by adjusting the aeration pressure. The reactor was operated until the nitrite accumulation rate in the effluent exceeded 90%, and a significant biofilm formed on the membrane surface. The sludge-water mixture was then poured out, and denitrifying sludge was inoculated with a sludge concentration (MLSS) of 3000-5000 mg / L. Simultaneously, the first carrier (5-1) of the MABR-PN / DN reactor (1-1) was added, with a filling rate of 15-45%. NH4Cl and glucose were introduced to increase the NH4 content in the solution. + Start-up is considered successful when the nitrogen concentration is 100 mg / L, the COD is 200 mg / L, the pH is adjusted to 7.5-8.0 with NaHCO3, the dissolved oxygen is controlled at 0.3-0.5 mg / L, and the total nitrogen removal rate is >50%. No second carrier is used in the MABR-PN / A reactor (1-2). The second-stage MABR reactor, i.e., the MABR-PN / A reactor (1-2), is inoculated with nitrifying sludge at a MLSS concentration of 3000-5000 mg / L. NH4Cl is introduced to make the solution NH4+. + The nitrogen (N) concentration was 100 mg / L. The pH was adjusted to 7.5–8.0 with NaHCO3, and the dissolved oxygen was controlled at 1.0–1.2 mg / L. The hydraulic retention time was controlled by adjusting the influent flow rate, and the dissolved oxygen in the reactor was controlled by adjusting the aeration pressure. The reactor was operated until the nitrite accumulation rate in the effluent exceeded 90%, and a significant biofilm formed on the membrane surface. The mud-water mixture was then poured out, and anaerobic ammonia-oxidizing bacteria with a VSS of 4000–5000 mg / L were inoculated. Simultaneously, the second carrier (5-2) of the MABR-PN / A reactor was added, with a filling rate of 15–45%. NH4Cl was introduced to increase the NH4+ concentration in the solution. + Start-up was completed when the TN removal rate was >80% for 10 consecutive days, with a TN concentration of 100 mg / L, dissolved oxygen <0.2 mg / L, temperature 30-35℃. 2) Operational Phase The first-stage MABR reactor, namely the MABR-PN / DN reactor (1-1), controls the dissolved oxygen at 0.3~0.5 mg / L, the hydraulic retention time at 5~10 h, and the temperature at 15~35℃. The second-stage MABR reactor, namely the MABR-PN / A reactor (1-2), controls dissolved oxygen <0.2 mg / L, with the same hydraulic retention time as the first-stage MABR reactor, and a temperature of 30-35℃. Every 5-15 days, a trace amount of hydroxylamine with a final concentration of 0.5 mg / L is added to promote the activity of anaerobic ammonia oxidizing bacteria. Connect the first-stage MABR reactor and the second-stage MABR reactor, and adjust the reflux ratio to 50~150%.

7. The efficient denitrification method according to claim 6, characterized in that: In step 2), the mass ratio of ammonia nitrogen to nitrite nitrogen in the effluent of the first-stage MABR reactor is greater than 1:1.

32.

8. The application of the efficient denitrification method as described in claim 6 or 7 in the treatment of ammonia nitrogen-containing wastewater with a low carbon-to-nitrogen ratio.

9. The application of the high-efficiency denitrification system based on a two-stage MABR as described in any one of claims 1 to 5 in the treatment of ammonia nitrogen-containing wastewater with a low carbon-to-nitrogen ratio.

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