A low-carbon and high-efficiency denitrification method

Abstract

The invention discloses a low-carbon and high-efficiency denitrification method. The DO concentration value of a rapid mixer is controlled within a range of 0.5 mg / L to 1 mg / L, the DO concentration value of a denitrification reaction zone is controlled within a range of 0.1 mg / L to 0.2 mg / L; the DO concentration value of an anaerobic ammonium oxidation reaction zone is controlled within a range of 0 mg / L to 0.05 mg / L, the sludge return ratio is controlled within a range of 30% to 60%, and the internal reflux ratio is controlled within a range of 150% to 200%. By strictly controlling the DO concentration value, the DO concentration value is controlled within an optimal effective value, a nitrite nitrogen environment is continuously and stably created, and a prerequisite is provided for subsequent anaerobic ammonium oxidizing bacteria to obtain nitrite nitrogen as a stable reaction substrate. Repeated periodic reflux cycles are set, and the denitrification reaction efficiency is multiplied. Under low carbon-nitrogen ratio conditions, anaerobic ammonium oxidation coordinated denitrification is achieved, the abundance of functional bacteria is increased, 80% of organic carbon sources can be saved, and sludge production and greenhouse gas emissions are thereby reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and more particularly to a low-carbon and high-efficiency denitrification method. Background Art

[0002] Adding external carbon sources also increases carbon dioxide emissions. As the global greenhouse effect intensifies, reducing emissions of greenhouse gases like carbon dioxide is also a must. Therefore, new low-carbon, efficient, and sustainable wastewater treatment technologies are urgently needed.

[0003] In the early 1990s, Mulder, van de Graaf, and others in the Netherlands discovered the anaerobic ammonium oxidation process and isolated a new type of microorganism—anaerobic ammonium oxidizer. This discovery not only provided new insights into the natural nitrogen cycle but also signaled a fundamental shift in microbial nitrogen metabolism. This spurred the development of biological wastewater denitrification technologies and ushered in a new era of research into novel processes, exemplified by Anammox.

[0004] Anaerobic ammonium oxidation (Anammox), also known as anaerobic ammonium oxidizing bacteria, is an autotrophic bacterium. Under anoxic or anaerobic environment, anaerobic ammonium oxidizing organisms use ammonia and nitrite as electron donors for inorganic carbon fixation and receptors for anaerobic ammonium oxidation reactions, respectively, to produce colorless, odorless, stable nitrogen (N2) and nitrate. The stoichiometric equation is NH4 + +1.32NO2 - +0.066HCO3 - +0.13H + →

[0005] 1.02N2+0.26NO3 - +0.066CH2O 0.5 N 0.15 +2.03H2O, this equation also includes catabolic and anabolic reactions.

[0006] In recent years, although there have been fruitful research results on the growth and metabolic characteristics of anaerobic ammonium oxidizing bacteria and process development and application, the actual application of anaerobic ammonium oxidizing technology still faces long-term bottlenecks, such as:

[0007] ①It is difficult to stably obtain the reaction matrix nitrite nitrogen (NO2 - );

[0008] ② The anaerobic ammonium oxidizing bacteria group is unstable due to the lack of environment and inorganic carbon source, and needs to be inoculated regularly;

[0009] ③ Total nitrogen after anaerobic ammonium oxidation reaction (mainly nitrate nitrogen NO3 -) increases, resulting in excessively high total nitrogen in the total drainage and inability to obtain high-quality recycled water, etc.

[0010] Therefore, how to solve the problems of excessive total nitrogen in sewage effluent and high energy consumption of sewage denitrification aeration has become a technical problem that needs to be broken through urgently. Summary of the Invention

[0011] In order to overcome the deficiencies of the prior art, the present invention provides a low-carbon and high-efficiency denitrification method to solve the problem of excessively high total nitrogen in sewage effluent, thereby achieving efficient treatment of municipal sewage while improving the quality of recycled water.

[0012] The technical solution of the present invention is as follows: A low-carbon and high-efficiency denitrification method comprises the following steps:

[0013] S1. Municipal sewage flows through the collection pipe and then enters the screen well, where the coarse suspended solids are removed by the screen machine;

[0014] S2, the regulating tank regulates the water volume and homogenizes the water quality of municipal sewage to obtain neutralized sewage;

[0015] S3. The neutralized sewage is transported to the rapid mixer through a submersible lift pump, and then the neutralized sewage enters the nitrite nitrogen stabilization acquisition zone, denitrification reaction zone and anaerobic ammonium oxidation reaction zone of the circulating anaerobic ammonium oxidation bioreactor in sequence. A small amount of excess sludge treated by the circulating anaerobic ammonium oxidation bioreactor is returned to the rapid mixer through the internal reflux pipeline, and PAC reagent is added at the same time. After mixing in the rapid mixer, it enters the circulating anaerobic ammonium oxidation bioreactor and circulates repeatedly to oxidize NH4 to N2 until the ammonia nitrogen mass concentration is less than 1.3 mg / L. Among them, the DO concentration value of the rapid mixer is controlled at 0.5 mg / L to 1 mg / L, the DO concentration value of the denitrification reaction zone is controlled at 0.1 mg / L to 0.2 mg / L, and the DO concentration value of the anaerobic ammonium oxidation reaction zone is controlled at 0 mg / L to 0.05 mg / L. The sludge return ratio is controlled at 30% to 60%, and the internal reflux ratio is controlled at 150% to 200%;

[0016] S4. The sewage in step S3 is passed into the MBR membrane tank. The MBR membrane tank is used to achieve solid-liquid separation of mud and water. The sludge mixed liquid is returned to the rapid mixer through the sludge return pipeline, and the regenerated water enters the reuse water tank.

[0017] It is worth noting that the external reflow ratio is also called the sludge reflow ratio. The corresponding internal reflow ratio is the nitrification liquid reflow ratio. The sludge reflow ratio is defined as the ratio of the sludge reflow volume to the aeration tank inlet volume.

[0018] Furthermore, in step S3, the following steps are included:

[0019] S31, a small amount of excess sludge is quickly mixed in the rapid mixer and then enters the nitrite nitrogen stable acquisition area, where high concentrations of NO3- The forward reaction, the chemical reaction formula of the nitrite nitrogen stable acquisition zone is:

[0020] NH4++2O2→NO2 - +2H2O

[0021] NH3+1.5O2→NO2 - +2H + +H2O

[0022]

[0023] The concentration of nitrite nitrogen NO2- is increased through the nitrite nitrogen stable acquisition zone, and then the next nitrogen removal treatment cycle is entered;

[0024] S32. The effluent from step S31 enters the denitrification reaction zone, where NO3- is reduced to NO2- by denitrification, and then NO2- is reduced to nitrogen gas by denitrification; thereafter, the effluent enters the anaerobic ammonium oxidation reaction zone, where anaerobic ammonium oxidizing bacteria are used to oxidize NH4 to N2 using NO2- as an electron acceptor. The chemical reaction formulas for the denitrification reaction zone and the anaerobic ammonium oxidation reaction zone are:

[0025]

[0026] NH4 + +1.5NO3 - →0.5N2+2H2O

[0027] NH4 + +1.5NO2 - +0.5H2O→0.5N2+2H + +2H2O.

[0028] Furthermore, an inlet water quality detection pipeline is provided at the rear end of the screen machine; the inlet water quality detection pipeline is connected to the inlet water quality detection system, and the inlet water quality detection system transmits the collected COD, BOD, ammonia nitrogen, total phosphorus and total nitrogen data to the PLC intelligent control system through the network cable, and monitors the inlet carbon-nitrogen ratio in real time through the AI ​​program.

[0029] Furthermore, a float level gauge is provided inside the regulating tank, a submersible lifting pump is provided at the end of the regulating tank to connect to a lifting pipeline, an electromagnetic flow meter is provided on the lifting pipeline, and the float level gauge transmits the liquid level signal to the PLC intelligent control system through a signal line.

[0030] Furthermore, a DO sensor and a PH sensor are provided in the rapid mixer, and the DO sensor and the PH sensor transmit the collected DO and PH data to the PLC intelligent control system through a data transmission line via a multi-parameter online detector; the rapid mixer is connected to the carbon source dosing device and the PAC dosing device respectively through dosing pipelines.

[0031] Furthermore, a membrane assembly is provided inside the MBR membrane pool, and an aeration device is provided at the lower end of the membrane assembly. The aeration device is connected to the fan through an aeration pipeline, and the upper end of the membrane assembly is connected to the water inlet end of the water production pump and the water outlet end of the backwash pump through a water production pipeline. The water outlet of the water production pump is connected to the reuse water tank, and the water inlet end of the backwash pump is connected to the reuse water tank through the backwash pipeline; a sludge return pump is provided at the bottom end of the MBR membrane pool, and the sludge return pump is connected to the rapid mixer through the sludge return pipeline, and an electromagnetic flowmeter is provided on the sludge return pipeline; a sludge discharge pipeline is provided at the bottom of the MBR membrane pool to connect to the regulating tank.

[0032] Furthermore, an effluent water quality detection pipeline is provided at the end of the reuse water pool; the effluent water quality detection pipeline is connected to the effluent water quality detection system, and the effluent water quality detection system transmits the collected COD, BOD, ammonia nitrogen, total phosphorus and total nitrogen data to the PLC intelligent control system through the data transmission line, and monitors the effluent water quality in real time through the program.

[0033] Furthermore, the PLC intelligent control system includes an AI computing power module, which reads real-time data on DO concentration and pH concentration, compares and calculates the real-time collected DO concentration value with the set limit, controls the increase / decrease of the sludge return pump operating frequency, adjusts the return ratio value, and controls the DO concentration of the rapid mixer to remain at 1 mg / L.

[0034] Furthermore, a circulation flow propeller is provided inside the nitrite nitrogen stabilization acquisition zone and the denitrification reaction zone, and an internal reflux pump is provided at the end of the anaerobic ammonia oxidation reaction zone. The internal reflux pump is connected to the rapid mixer through an internal reflux pipeline, and an electromagnetic flowmeter is provided on the internal reflux pipeline.

[0035] Furthermore, the bottoms of the nitrite nitrogen stabilization acquisition zone, the denitrification reaction zone and the anaerobic ammonia oxidation reaction zone are all provided with venting and sludge discharge pipelines connected to the regulating tank.

[0036] The present invention according to the above scheme has the following beneficial effects:

[0037] (1) The present invention provides a low-carbon and high-efficiency denitrification method, wherein the DO concentration value of the rapid mixer is controlled at 0.5 mg / L to 1 mg / L, the DO concentration value of the denitrification reaction zone is controlled at 0.1 mg / L to 0.2 mg / L; the DO concentration value of the anaerobic ammonia oxidation reaction zone is controlled at 0 mg / L to 0.05 mg / L, the sludge return ratio is controlled at 30% to 60%, and the internal reflux ratio is controlled at 150% to 200%. By strictly controlling the DO concentration value, the DO concentration value is controlled within the most suitable effective value, and the DO concentration value is continuously and stably controlled. It creates a nitrite nitrogen environment, which provides the prerequisite for the subsequent anaerobic ammonia-oxidizing bacteria to obtain stable reaction substrate nitrite nitrogen. It sets up repeated periodic reflux cycles, which increases the denitrification reaction efficiency by several times, realizes anaerobic ammonia-oxidation coordinated denitrification under low carbon-nitrogen ratio conditions, increases the abundance of functional bacteria, and can save 80% of organic carbon sources, thereby reducing sludge production and greenhouse gas emissions. Moreover, it can make the effluent water quality stable and meet the standards and better than the national Class A standard and the "Water Quality of Urban Miscellaneous Water for Urban Wastewater Recycling" standard.

[0038] (2) The present invention provides a low-carbon and high-efficiency denitrification method, which uses PLC intelligent control technology equipped with an AI computing power module to efficiently, scientifically and in real time calculate the oxygen demand and internal and external reflux ratio of the nitrite nitrogen stable acquisition zone at the front end of the circulating anaerobic ammonia oxidation bioreactor, so that the operation of the biological system and the effluent water quality are more stable. At the same time, the application of PLC intelligent control technology equipped with an AI computing power module is more in line with the operation of the biochemical system, reduces the intensity of manual operation, and improves the efficiency and effect of sewage treatment, thereby achieving the goal of energy saving and consumption reduction, and realizing a high degree of consistency between intelligence and water resource recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 Schematic diagram of the structure of a low-carbon and high-efficiency denitrification system in an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of a dissolved oxygen value collection and control system in an embodiment of the present invention;

[0042] Figure 3 Schematic diagram of the water outlet total nitrogen data acquisition and control system in an embodiment of the present invention;

[0043] Figure 4 Schematic diagram of the carbon-nitrogen ratio collection, analysis and control system in an embodiment of the present invention.

[0044] In the figure, 1, grid well; 2, regulating tank; 3, rapid mixer;

[0045] 4. Circulating anaerobic ammonium oxidation bioreactor; 401. Nitrite nitrogen stabilization acquisition zone; 402. Denitrification reaction zone; 403. Anaerobic ammonium oxidation reaction zone;

[0046] 5. MBR membrane pool; 6. Recycled water pool;

[0047] 7. PLC intelligent control system; 701. Computer terminal; 702. Mobile phone APP terminal; 703. Inlet water quality detection system, 704. Outlet water quality detection system; 705. Data transmission line;

[0048] 11. Screen machine; 12. Float level gauge; 13. Submersible lift pump; 14. Electromagnetic flowmeter; 15. Carbon source dosing device; 16. PAC dosing device; 17. pH sensor; 18. Multi-parameter online detector; 19. Circulating flow propeller; 20. Internal reflux pump; 21. Fan; 22. Membrane module; 23. Aeration device; 24. Sludge return pump; 25. Water production pump; 26. Backwash pump;

[0049] 30. Lifting pipeline; 31. Internal return pipeline; 32. Sludge return pipeline; 33. Water production pipeline; 34. Backwash pipeline; 35. Sludge discharge pipeline; 36. Influent water quality testing pipeline; 37. Dosing pipeline; 38. Aeration pipeline; 39. Outfluent water quality testing pipeline. DETAILED DESCRIPTION

[0050] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments.

[0051] In order to better understand the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments:

[0052] See also Figures 1 to 4 This embodiment provides a high-efficiency denitrification system for low-carbon source municipal sewage. According to the flow direction of municipal sewage from the water inlet end to the water outlet end, a screen well 1, a regulating tank 2, a rapid mixer 3, a circulating anaerobic ammonium oxidation bioreactor 4, an MBR membrane tank 5, and a reuse water tank 6 are sequentially arranged. Among them, the screen well 1 and the regulating tank 2 are an integrated structure. The regulating tank 2 is connected to the rapid mixer 3 through a submersible lifting pump 13. The outlet of the rapid mixer 3 is connected to the circulating anaerobic ammonium oxidation bioreactor 4 through a pipeline. The end outlet of the circulating anaerobic ammonium oxidation bioreactor 4 is connected to the MBR membrane tank 5 through a pipeline. The MBR membrane tank 5 and the reuse water tank 6 are a connected structure.

[0053] In this embodiment, a screen machine 11 is provided inside the screen well 1, and an inlet water quality detection pipeline 36 is provided at the rear end of the screen machine 11; the inlet water quality detection pipeline 36 is connected to the inlet water quality detection system 703, and the inlet water quality detection system 703 transmits the collected COD (chemical oxygen demand, which refers to the amount of oxidant consumed when a certain strong oxidant is used to treat a water sample under certain conditions), BOD (BOD is the amount of oxygen used when biologically decompose organic matter, used to indicate the concentration of organic matter in wastewater), ammonia nitrogen, total phosphorus, and total nitrogen data to the PLC intelligent control system 7 through a network cable, and monitors the inlet carbon-nitrogen ratio in real time through an AI program; a float level gauge 12 is provided inside the regulating tank 2, and a submersible lifting pump 13 is provided at the end of the regulating tank 2 to connect to the lifting pipeline 30, and an electromagnetic flowmeter 14 is provided on the lifting pipeline 30, and the float level gauge 12 transmits the liquid level signal to the PLC intelligent control system 7 through a signal line.

[0054] In this embodiment, a DO sensor and a pH sensor 17 are provided in the rapid mixer 3. The DO sensor and the pH sensor 17 transmit the collected DO and pH data to the PLC intelligent control system 7 through the data transmission line 705 via the multi-parameter online detector 18; the rapid mixer 3 is connected to the carbon source dosing device 15 and the PAC dosing device 16 respectively through the dosing pipeline 37.

[0055] In this embodiment, the circulating anaerobic ammonium oxidation bioreactor 4 is divided into three reaction zones according to the reaction stage, namely the nitrite nitrogen stable acquisition zone 401, the denitrification reaction zone 402 and the anaerobic ammonium oxidation reaction zone 403; the nitrite nitrogen stable acquisition zone 401 and the denitrification reaction zone 102 are both provided with a circulating flow pusher 19, and the end of the anaerobic ammonium oxidation reaction zone 403 is provided with an internal reflux pump 20, and the internal reflux pump 20 is connected to the rapid mixer 3 through the internal reflux pipeline 31, and the internal reflux pipeline 31 is provided with an electromagnetic flowmeter 14; the bottom of the nitrite nitrogen stable acquisition zone 401, the denitrification reaction zone 402 and the anaerobic ammonium oxidation reaction zone 403 are all provided with a venting and sludge discharge pipeline 35 connected to the regulating tank 2.

[0056] In this embodiment, a membrane assembly 22 is provided inside the MBR membrane pool 5, and an aeration device 23 is provided at the lower end of the membrane assembly. The aeration device 23 is connected to the fan 21 through an aeration pipeline 38, and the upper end of the membrane assembly 22 is connected to the water inlet end of the water production pump 25 and the water outlet end of the backwash pump 26 through a water production pipeline 33, wherein the water outlet of the water production pump 25 is connected to the reuse water pool 6, and the water inlet end of the backwash pump 26 is connected to the reuse water pool 6 through a backwash pipeline 34; a sludge return pump 24 is provided at the bottom of the end of the MBR membrane pool 5, and the sludge return pump 24 is connected to the rapid mixer 3 through a sludge return pipeline 32, and an electromagnetic flowmeter 14 is provided on the sludge return pipeline 32; a sludge discharge pipeline 35 is provided at the bottom of the MBR membrane pool 5 to connect to the regulating tank 2.

[0057] In this embodiment, an outlet water quality detection pipeline 39 is provided at the end of the reuse water pool 6; the outlet water quality detection pipeline 39 is connected to the outlet water quality detection system 704, and the outlet water quality detection system 704 transmits the collected COD, BOD, ammonia nitrogen, total phosphorus, and total nitrogen data to the PLC intelligent control system 7 through the data transmission line 705, and monitors the outlet water quality in real time through the program.

[0058] Specifically, during the continuous operation stage, the screen machine 11, submersible lift pump 13, circulating flow propeller 19, fan 21, water production pump 25, backwash pump 26, and PAC dosing device 16 are all connected to the power input end of the PLC intelligent control system 7, and the start and stop of the equipment can be automatically controlled through the program.

[0059] During the continuous operation stage, the AI ​​computing module in the PLC intelligent control system 7 reads the real-time data of DO concentration and pH concentration, compares and calculates the real-time collected DO concentration value with the set limit, controls the increase or decrease of the operating frequency of the sludge return pump 24, adjusts the value of the return ratio, and controls the DO concentration of the rapid mixer 3 to remain at 1 mg / L.

[0060] During the continuous operation phase, the AI ​​computing module in the PLC intelligent control system 7 reads the real-time data of the total nitrogen concentration in the effluent and the carbon-nitrogen ratio in the inlet water, and intelligently controls the operation time of the carbon source dosing device 15 based on the comparison and calculation of the real-time collected total nitrogen concentration value in the effluent and the carbon-nitrogen ratio in the inlet water with the set limit value;

[0061] During the continuous operation phase, the electromagnetic flowmeter 14 transmits the flow signal to the PLC intelligent control system 7 via the signal line;

[0062] In this embodiment, the PLC intelligent control system 7 includes modules such as a PLC logic control cabinet, a 4G network Internet of Things transmission gateway, a fault sensor, a status sensor, and an artificial intelligence program, thereby realizing remote control of the computer terminal 701 and the mobile phone APP terminal 702.

[0063] In this embodiment, a high-efficiency denitrification system for low-carbon source municipal sewage uses a PLC intelligent control system 7 to control the DO concentration value. The specific control steps are as follows:

[0064] The DO monitor, serving as a monitoring base point, transmits data to the DO analyzer for analysis to determine the actual DO value. The DO analyzer transmits the 4-20mA current signal via a shielded signal cable to the PLC-AI module for reception. The PLC uses a PID control algorithm to convert the analog quantity into a digital quantity, which is displayed on the control terminal. An AI artificial intelligence algorithm is set up in the PLC program. Based on the program's calculation results, the AO module converts the PLC's digital quantity into a 4-20mA current signal to control the frequency converter. By changing the PLC's digital quantity, the analog quantity is changed, achieving variable speed control of the sludge return pump and the return ratio. Ultimately, when the DO value is low, the sludge return pump's return ratio is intelligently adjusted to increase, and when the DO value is high, the sludge return pump's return ratio is intelligently adjusted to decrease, keeping the DO value stable and effective within the set value range.

[0065] In this embodiment, a high-efficiency denitrification system for low-carbon source municipal sewage uses a PLC intelligent control system 7 to control the carbon source dosing pump. The specific control steps are as follows:

[0066] The online effluent total nitrogen detection system performs total nitrogen detection and analysis based on the set time to determine the actual effluent total nitrogen value. The online effluent water quality analyzer transmits a 4-20mA current signal to the PLC-AI module via a shielded signal line. The PLC converts the analog value into a digital value through a PID control algorithm and displays it on the control terminal. An AI artificial intelligence algorithm is set in the PLC program, which changes the PLC's digital value based on the program's calculation results. The DO switch output module sends a pulse signal to control the operation and stop of the carbon source dosing pump. Ultimately, when the effluent total nitrogen value is lower than the analog value, the intelligent control carbon source dosing pump stops. When the effluent total nitrogen value is higher, the intelligent control carbon source dosing pump starts, keeping the effluent total nitrogen value stable and effectively within the set value range.

[0067] In this embodiment, a high-efficiency denitrification system for low-carbon source municipal sewage uses a PLC intelligent control system 7 to control the carbon-nitrogen-phosphorus ratio of the influent. The specific control steps are as follows:

[0068] The inlet water online detection system detects and analyzes the total nitrogen, BOD, and total phosphorus concentrations based on set time intervals to determine the actual inlet water total nitrogen, BOD, and total phosphorus concentrations. The inlet water online water quality analyzer transmits a 4-20 mA current signal to the PLC-AI module via a shielded signal cable. The PLC converts the analog value into a digital value using a PID control algorithm and displays it on the control terminal. An AI artificial intelligence algorithm is set in the PLC program. Based on the program's calculation results, the AO module converts the PLC's digital value into a 4-20 mA current signal to control the carbon source dosing pump motor. By changing the PLC's digital value, the analog value is changed, achieving variable speed control of the carbon source dosing pump motor to control the dosing amount. Ultimately, when the program calculates a low carbon-nitrogen-phosphorus ratio, the carbon source dosing pump intelligently increases the dosing amount, and when the carbon-nitrogen-phosphorus ratio is high, the carbon source dosing pump intelligently decreases the dosing amount, ensuring that the carbon-nitrogen-phosphorus ratio remains stable and effective within the set value range.

[0069] On the other hand, the present invention provides a method for low-carbon and high-efficiency denitrification, which is characterized by the following steps:

[0070] Step S1: Municipal sewage is collected through the collection pipe network and enters the screen well 1, where coarse suspended solids are removed by the screen machine 11;

[0071] Step S2: The sewage from step S1 above then enters the sewage regulating tank 2 for further water volume regulation and water quality homogenization to obtain neutralized sewage;

[0072] In step S3 and step S2 above, the sewage in the regulating tank is lifted by the submersible lifting pump 13 and enters the rapid mixer 3, and then enters the circulating anaerobic ammonium oxidation bioreactor 4. The end of the circulating anaerobic ammonium oxidation bioreactor 4 is refluxed to the rapid mixer 3 through anaerobism, and PAC agent is added at the same time. After mixing in the rapid mixer 3, it enters the circulating anaerobic ammonium oxidation bioreactor 4. The functional bacteria in the circulating anaerobic ammonium oxidation bioreactor 4 repeatedly react in multiple cycles, so that carbon and nitrogen in the sewage are synergistically degraded through multiple biochemical reactions. At the same time, the dense biological filler inside the circulating anaerobic ammonium oxidation bioreactor 4 is conducive to the coexistence and reproduction of multifunctional bacteria, thereby increasing the abundance of functional bacteria, rapidly enriching the anaerobic ammonium oxidation bacteria and denitrifying bacteria in the system, reducing the loss of bacteria, and solving the problem that anaerobic ammonium oxidation bacteria are sensitive to external environmental factors and difficult to retain. The anaerobic ammonium oxidation bacteria fully utilize the carbon dioxide formed by organic matter in the raw water in the anaerobic ammonium oxidation reaction zone as an inorganic carbon source for effective reproduction, thereby reducing the addition of external carbon source.

[0073] In step S4, the wastewater from step S3 flows by gravity into the MBR membrane tank 5. The filtration of the MBR membrane tank 5 achieves solid-liquid separation, thereby removing organic matter and achieving nitrogen and phosphorus removal. The remaining sludge mixture is returned to the rapid mixer 3 via the sludge return pump 24 and the sludge return line 32. This ensures that the DO in the returned sludge-water mixture is at an optimal value, ensuring a stable supply of nitrite nitrogen, the reaction substrate required for the anaerobic ammonium oxidation reaction. The resulting high-quality regenerated water enters the reuse water tank 6, which can be used for road washing, landscaping, toilet flushing, and other purposes.

[0074] According to the present invention of the above scheme, step S3 specifically includes:

[0075] Step S31, the circulating anaerobic ammonium oxidation bioreactor 4 is divided into three reaction zones according to the reaction stage, namely the nitrite nitrogen stable acquisition zone 401, the denitrification reaction zone 402, and the anaerobic ammonium oxidation reaction zone 403; the rapid mixer 3 receives the anaerobic return of the anaerobic ammonium oxidation reaction zone 403 and the small amount of residual sludge mixed liquid of the MBR membrane tank 5, and after rapid mixing in the rapid mixer 3, it enters the nitrite nitrogen stable acquisition zone 401 multifunctional bacterial community reaction, and the high concentration of NO3 - inhibition The forward reaction further increases the nitrite nitrogen NO2 - The concentration of nitrite nitrogen continuously and stably creates an environment for the formation of nitrite nitrogen, which provides a stable reaction matrix of nitrite nitrogen (NO2 - ); the chemical reaction formula of nitrite nitrogen stable acquisition zone 401 is:

[0076] NH4++2O2→NO2 - +2H2O

[0077] NH3+1.5O2→NO2 - +2H + +H2O

[0078]

[0079] Step S32: The effluent from step S32 enters the denitrification reaction zone 402, where only NO3 - Reduction to NO2 - , shortening the nitrogen conversion pathway. By directly converting NO2 - Reduced to nitrogen, and enters the anaerobic ammonium oxidation reaction zone 403 at the same time. The anaerobic ammonium oxidation reaction zone 403 uses anaerobic ammonium oxidizing bacteria to convert NO2 - As an electron acceptor, NH4 is oxidized to N2. Anaerobic ammonia-oxidizing bacteria fully utilize the CO2 produced by the digestion of a small amount of organic matter in the sewage as an inorganic carbon source, without the need for aeration and external carbon source.

[0080] The chemical reaction formulas of the denitrification reaction zone 402 and the anaerobic ammonium oxidation reaction zone 403 are:

[0081]

[0082] NH4 + +1.5NO3 - →0.5N2+2H2O

[0083] NH4 + +1.5NO2 - +0.5H2O→0.5N2+2H + +2H2O

[0084] During biological denitrification, NO3 - N is converted to NO2 - N and NO2 - The process of converting N to N2 requires 40% and 60% electron donors respectively. In the denitrification process, the electron donor required by heterotrophic denitrifying bacteria is an organic carbon source. For low COD / N wastewater, especially urban sewage, the lack of organic carbon source will hinder the complete removal of nitrogen oxides. In a high COD / N environment, NO2 - Nitrogen tends to be reduced by heterotrophic denitrifying bacteria and inhibit the Anammox reaction. Under low COD / N conditions, NO2 - N to NO3 - N is more susceptible to the lack of carbon sources, which inhibits its reduction rate, making NO2 - The accumulation rate of N is high. Therefore, in this embodiment, COD / N is set to 3.5. Of course, the lower the COD / N, the better. After research, it was found that the optimal range of COD / N is 2.0 to 3.5. The inventors found that when COD / N is lower than 2.0, it will seriously limit the NO2 - The generation efficiency of N.

[0085] In step S3, the DO concentration value of the rapid mixer 3 is controlled at 0.5 mg / L to 1 mg / L, and the DO concentration value of the denitrification reaction zone 402 is controlled at 0.1 mg / L to 0.2 mg / L;

[0086] In step S31, the sludge return ratio is controlled at 30% to 60%, the internal return ratio is 150% to 200%, and the optimal return ratio is calculated by the AI ​​computing module based on the actual influent.

[0087] In this embodiment, the pH of the denitrification reaction zone 402 is 9.0. The inventors found that under the alkaline condition of pH = 9.0, a higher NO2 -Accumulation. After analysis, it was found that the pH of municipal sewage is 7.0-8.0. When it is in an alkaline environment of pH=9.0, the activity of denitrifying microorganisms in the sludge may be inhibited in a short time. As the pH increases, NO2 - The maximum conversion rate showed a significant upward trend, from 36.6% at pH = 6.0 to 67.4% at pH = 9.0, which was mainly due to the NO3 - Reductase and NO2 - There are differences in the relative activities of reductases. Under alkaline conditions, the activities of both enzymes will be inhibited, but NO2 - The reductase activity was more strongly inhibited.

[0088] Please refer to Table 1 and Table 2. A low-carbon and high-efficiency denitrification method in this embodiment is practiced in a municipal domestic sewage treatment plant in a town in Gansu. The COD concentration of the influent raw water is 120-150 mg / L, the ammonia nitrogen concentration is 25-40 mg / L, and the total nitrogen concentration is 35-50 mg / L. The average influent concentrations of COD, ammonia nitrogen, and total nitrogen are 135 mg / L, 32.5 mg / L, and 42.5 mg / L, respectively.

[0089] Table 1 Ammonia nitrogen detection data at different points 15 days after the system meets the standards and operates stably

[0090]

[0091] Table 2 Total nitrogen detection data at different points after the system meets the standards and operates stably for 15 days

[0092]

[0093] As can be seen from the table above, by adopting the process mentioned in the present invention, the DO concentration value of the rapid mixer is controlled at 0.5mg / L~1mg / L, the DO concentration value of the denitrification reaction zone is controlled at 0.1mg / L~0.2mg / L; the DO concentration value of the anaerobic ammonia oxidation reaction zone is 0mg / L~0.05mg / L, the sludge return ratio is 50%, and the internal return ratio is 180%, the ammonia nitrogen removal rate can be 94%~98%, and the stable average ammonia nitrogen removal rate is 9 6%, and the average effluent ammonia nitrogen concentration was 1.3 mg / L; the total nitrogen removal rate was 88% to 92%, the stable average total nitrogen removal rate was 90%, and the average effluent total nitrogen concentration was 4.25 mg / L; the effluent COD concentration was stably maintained at 30 mg / L, with an average of 25 mg / L, which proved that the process mentioned in the present invention has a stable effluent water quality that meets the standard and is better than the national Class A standard and the "Water Quality of Urban Miscellaneous Water for Urban Wastewater Recycling" standard.

[0094] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

[0095] The above is an exemplary description of the patent of the present invention in conjunction with the accompanying drawings. It is obvious that the implementation of the patent of the present invention is not limited to the above-mentioned method. As long as various improvements are made by adopting the method concept and technical solution of the patent of the present invention, or the concept and technical solution of the patent of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A low-carbon and high-efficiency denitrification method, characterized in that: The following steps are involved: S1. Municipal sewage flows through the collection pipe and then enters the screen well, where the coarse suspended solids are removed by the screen machine; S2, the regulating tank regulates the water volume and homogenizes the water quality of municipal sewage to obtain neutralized sewage; S3. The neutralized sewage is transported to the rapid mixer through a submersible lift pump, and then the neutralized sewage enters the nitrite nitrogen stabilization acquisition zone, denitrification reaction zone and anaerobic ammonium oxidation reaction zone of the circulating anaerobic ammonium oxidation bioreactor in sequence. A small amount of excess sludge treated by the circulating anaerobic ammonium oxidation bioreactor is returned to the rapid mixer through the internal reflux pipeline, and PAC reagent is added at the same time. After mixing in the rapid mixer, it enters the circulating anaerobic ammonium oxidation bioreactor and circulates repeatedly to oxidize NH4 to N2 until the ammonia nitrogen mass concentration is less than 1.3 mg / L. Among them, the DO concentration value of the rapid mixer is controlled at 1 mg / L, the DO concentration value of the denitrification reaction zone is controlled at 0.1 mg / L~0.2 mg / L, and the DO concentration value of the anaerobic ammonium oxidation reaction zone is controlled at 0 mg / L~0.05 mg / L. The sludge return ratio is controlled at 30%~60%, and the internal reflux ratio is controlled at 150%~200%; S4. The sewage in step S3 is passed into the MBR membrane tank, which is used to achieve solid-liquid separation of mud and water. The sludge mixture is returned to the rapid mixer through the sludge return pipeline, and the regenerated water enters the reuse water tank; The rapid mixer is equipped with a DO sensor and a PH sensor. The DO sensor and the PH sensor transmit the collected DO and PH data to the PLC intelligent control system through a data transmission line via a multi-parameter online detector. The rapid mixer is connected to the carbon source dosing device and the PAC dosing device through dosing pipelines. An outlet water quality detection pipeline is installed at the end of the reuse water pool; the outlet water quality detection pipeline is connected to the outlet water quality detection system, which transmits the collected COD, BOD, ammonia nitrogen, total phosphorus and total nitrogen data to the PLC intelligent control system through the data transmission line, and monitors the outlet water quality in real time through the program; The PLC intelligent control system includes an AI computing module, which reads real-time data on DO and pH concentrations. Based on the real-time DO concentration values, the module compares and calculates them with the set limits. This module controls the frequency of the sludge return pump, adjusts the return ratio, and maintains the DO concentration of the rapid mixer at 1 mg / L. Circulating flow propellers are installed inside the nitrite nitrogen stabilization acquisition zone and the denitrification reaction zone. An internal reflux pump is installed at the end of the anaerobic ammonia oxidation reaction zone. The internal reflux pump is connected to the rapid mixer through an internal reflux pipeline, and an electromagnetic flowmeter is installed on the internal reflux pipeline.

2. A low-carbon and high-efficiency denitrification method according to claim 1, characterized in that: An inlet water quality detection pipeline is installed at the rear end of the screen machine, which is connected to the inlet water quality detection system. The inlet water quality detection system transmits the collected COD, BOD, ammonia nitrogen, total phosphorus and total nitrogen data to the PLC intelligent control system through the network cable, and monitors the inlet carbon-nitrogen ratio in real time through the AI ​​program.

3. A low-carbon and high-efficiency denitrification method according to claim 2, characterized in that: A float level gauge is installed inside the regulating tank. A submersible lifting pump is installed at the end of the regulating tank to connect to the lifting pipeline. An electromagnetic flow meter is installed on the lifting pipeline. The float level gauge transmits the liquid level signal to the PLC intelligent control system through the signal line.

4. A low-carbon and high-efficiency denitrification method according to claim 1, characterized in that: A membrane assembly is provided inside the MBR membrane pool. An aeration device is provided at the lower end of the membrane assembly. The aeration device is connected to the fan through an aeration pipeline. The upper end of the membrane assembly is connected to the water inlet of the water production pump and the water outlet of the backwash pump through the water production pipeline. The water outlet of the water production pump is connected to the reuse water pool, and the water inlet of the backwash pump is connected to the reuse water pool through the backwash pipeline. A sludge return pump is provided at the bottom of the end of the MBR membrane pool. The sludge return pump is connected to the rapid mixer through the sludge return pipeline, and an electromagnetic flowmeter is provided on the sludge return pipeline. A sludge discharge pipeline is provided at the bottom of the MBR membrane pool to connect to the regulating tank.

5. The low-carbon and high-efficiency denitrification method according to claim 1, wherein: The bottom of the nitrite nitrogen stable acquisition area, the denitrification reaction area and the anaerobic ammonium oxidation reaction area are all equipped with venting and sludge discharge pipelines connected to the regulating tank.

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