A municipal sewage advanced denitrification and dephosphorization process

Abstract

The application discloses a kind of municipal sewage advanced denitrification and dephosphorization process, the device of adoption relies on PLC control unit, using sub-region DO gradient control strategy, in single reactor by structural optimization precise regulation and control water anaerobic stage, aerobic-microaerophilic cycle stage and sedimentation idle and effluent stage etc., successfully enriches phosphorus bacteria, denitrifying polysaccharide bacteria and denitrifying phosphorus bacteria etc., realizes the efficient denitrification and dephosphorization of sewage.The application realizes the low energy consumption advanced denitrification and dephosphorization of municipal sewage, TN, TP removal rate is close to 100%, and sludge settling performance is excellent, sludge particle size D 50 It is 100~200µm, sludge volume index is 30~60mL / g, realizes that granular sludge and floc sludge coexist, has wide engineering application prospect.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a deep denitrification and phosphorus removal process for municipal wastewater. Background Technology

[0002] Traditional biological nitrogen removal processes typically involve nitrification and denitrification, resulting in significant energy consumption. Aeration costs account for over 60% of the total energy consumption in wastewater treatment, and the process also faces the problem of insufficient carbon sources requiring additional carbon supplementation. Endogenous denitrification nitrogen and phosphorus removal (EDPR) technology is considered a promising treatment technology in recent years. This technology can remove nitrogen and phosphorus under anoxic conditions driven by the same carbon source, while maintaining nitrogen and phosphorus levels at a low NO₂ level. x -N acts as an electron acceptor to absorb phosphorus, thereby achieving simultaneous carbon, nitrogen, and phosphorus removal. Compared to traditional treatment methods, it can significantly reduce operating costs and reduce sludge production by 50%. Therefore, EDPR technology has been widely used in municipal wastewater treatment in recent decades.

[0003] The combination of simultaneous nitrification-denitrification (SND) and enhanced biological phosphorus removal reactor (EBPR) yields the SNDPR process. This process integrates nitrogen and phosphorus removal into a single reactor, simplifying the treatment flow and potentially reducing aeration energy consumption by enriching denitrifying polyphosphate-accumulating bacteria (DPAOs), thus achieving efficient carbon source utilization. Furthermore, if the nitrification reaction is controlled at the stage where ammonia-oxidizing bacteria decompose NH4+... + Oxidized to NO2 - Direct denitrification after the nitrification stage can save 25% of aeration energy and 40% of carbon source in a short-cut nitrification-denitrification process. However, achieving a stable short-cut nitrification-denitrification process with simultaneous phosphorus removal in a single reactor still faces technical bottlenecks and challenges, such as the conflict between sludge age of nitrifying bacteria and polyphosphate-accumulating bacteria, the competition for carbon source between heterotrophic denitrifying bacteria and polyphosphate-accumulating bacteria, and the inhibitory effect of nitrification products on the anaerobic phosphorus release process. Summary of the Invention

[0004] The purpose of this invention is to provide a deep nitrogen and phosphorus removal process for municipal wastewater, addressing the problems mentioned above, such as the contradiction between the sludge age of nitrifying bacteria and polyphosphate-accumulating bacteria in a single reactor short-cut nitrification-denitrification process, competition for carbon sources between heterotrophic denitrifying bacteria and polyphosphate-accumulating bacteria, and the inhibitory effect of nitrification products on the anaerobic phosphorus release process. This invention achieves a stable, simultaneous short-cut nitrification-denitrification process by constructing a spatial distribution of reaction zone I, reaction zone II, and peripheral reaction zone III within the main reactor, combined with precise control of ammonia nitrogen conversion rate.

[0005] To achieve the above objectives, the present invention provides a device for deep nitrogen and phosphorus removal from municipal wastewater. The device includes a main reactor and an aeration unit. The main reactor is provided with a reaction zone I, a reaction zone II, and a peripheral reaction zone III surrounding the reaction zone II. Both the reaction zone II and the peripheral reaction zone III are located above the reaction zone I. The main reactor has a wastewater inlet and a circulating inlet at the bottom. The wastewater inlet is connected to the inlet pump. The clean water outlet is located at the top of reaction zone I and is connected to the outlet pump. The aeration unit includes an aeration disc located at the bottom of reaction zone II and an aeration pump connected to the aeration disc. The circulating outlet is located at the bottom of the outer reaction zone III and is connected to the circulating inlet via a circulating pump. The municipal wastewater deep nitrogen and phosphorus removal process provided by this invention mainly includes the following steps: (1) Anaerobic influent stage The inlet pump delivers the wastewater to be treated into reaction zone I of the main reactor through the sewage inlet. During the inlet process, the water flows from bottom to top and mixes thoroughly with the sludge in reaction zone I to achieve anaerobic contact. The inlet pump stops when the water level rises to the top of reaction zone II, and the circulation pump is started until the anaerobic process ends. (2) Aerobic-microaerobic cycle stage After the anaerobic process ends, the device enters continuous operation, with the aeration pump and circulation pump running continuously, and the mixed liquor forms a stable circulating flow in the reactor. Aerobic Zone: Gas is evenly distributed into the reaction zone II through the aeration discs at the bottom, forming an aerobic zone where sludge and oxygen are in full contact, achieving aerobic phosphorus uptake; Micro-oxygen zone 1: Under the action of air lift, the mixed liquor enters the peripheral reaction zone Ⅲ with the fluid movement, and the dissolved oxygen concentration naturally decreases to form micro-oxygen zone 1, realizing short-cut nitrification and denitrification; Micro-oxygen zone 2: The mixed liquor is refluxed to reaction zone 1 under the drive of the circulation pump, and the dissolved oxygen concentration is further reduced, forming micro-oxygen zone 2, which further enhances the simultaneous removal of endogenous denitrification and phosphorus; In the aerobic-microaerobic cycle stage, the aerobic and microaerobic zones and the mixed liquid dual circulation process are realized simultaneously. The dual circulation process includes the internal circulation of reaction zone II and the outer reaction zone III, as well as the external circulation of the outer reaction zone III and the reaction zone I. After the aerobic-microaerobic cycle stage is completed, the aeration pump and the circulation pump are turned off. (3) Sedimentation and effluent stage The sludge settles and concentrates in the lower part of reaction zone I under gravity, entering an idle phase to enhance the microbial starvation effect. After the idle phase ends, the effluent pump is turned on, and the treated water is discharged through the clean water outlet, and the device enters the next cycle.

[0006] The main reactor of this invention forms anaerobic-aerobic-microaerobic zones, achieving a gradient distribution of dissolved oxygen (DO) across different regions. This promotes the synergistic effects of short-cut nitrification, endogenous denitrification, and polyphosphate-accumulating bacteria and polysaccharide-accumulating bacteria, enabling various functional bacterial communities to work together and improve nitrogen and phosphorus removal efficiency. Through reactor structure optimization, this invention achieves stable, simultaneous short-cut nitrification and endogenous denitrification phosphorus removal in a single device, enriching ammonia-oxidizing bacteria, polyphosphate-accumulating bacteria, denitrifying polyphosphate-accumulating bacteria, and denitrifying polysaccharide-accumulating bacteria, while inhibiting nitrite-oxidizing bacteria. Nitrogen and phosphorus removal efficiencies can all reach 100%, achieving advanced treatment of municipal wastewater. In the anaerobic influent stage, the polyphosphate-accumulating bacteria / denitrifying polyphosphate-accumulating bacteria (PAO / DPAO, releasing intracellularly stored phosphate) and denitrifying polysaccharide bacteria (DGAO) in the main reactor utilize external organic carbon sources to synthesize and accumulate polyhydroxyalkanoates (PHA), providing an internal carbon source for subsequent denitrification and phosphorus removal. In reaction zone II (aerobic zone), sufficient contact between sludge and oxygen is ensured, promoting the conversion of NH4+ by ammonia-oxidizing bacteria (AOB). + Oxidized to NO2 - Simultaneously, PAO absorbs phosphate from the water, achieving aerobic phosphorus uptake; in reaction zone III (microaerobic zone I), due to the consumption of oxygen by microorganisms, DO gradually decreases, leaving NH4+. + Continue to oxidize to NO2 - This creates a short-cut nitrification and denitrification environment. In reaction zone I (micro-oxygen zone II), DPAO and DGAO use stored PHA as electron donors for endogenous denitrification, while DPAO further absorbs phosphate. Throughout the process, the mixed liquor continuously circulates within the reactor through spatial partitioning, completing short-cut nitrification, endogenous denitrification, and phosphorus removal along the oxygen gradient, achieving deep nitrogen and phosphorus removal.

[0007] Preferably, the device also includes a PLC control unit, and the inlet pump, outlet pump, circulation pump and aeration pump are all connected to the PLC control unit.

[0008] Preferably, the device also includes a dissolved oxygen monitoring probe and NH4. + Two dissolved oxygen monitoring probes are respectively set in reaction zone II and the outer reaction zone III, and two NH4+ probes are also present. + Sensor monitoring probes are respectively installed in reaction zone II and the outer reaction zone III. Dissolved oxygen monitoring probe and NH4... + All data monitored by the sensor probes are transmitted to the PLC control unit. The specific design of the PLC control unit can be carried out according to existing technology, and will not be elaborated here.

[0009] The aforementioned PLC control unit can adjust based on online monitoring data (dissolved oxygen monitoring probe and NH4). +The sensor monitoring probe provides feedback to automatically adjust the aeration volume (aeration pump) and hydraulic circulation (speed of inlet pump, circulation pump, and outlet pump) to optimize the nitrogen and phosphorus removal process and achieve deep nitrogen and phosphorus removal.

[0010] Preferably, in step (1), the wastewater to be treated is municipal wastewater with a COD of 200~500 mg / L and NH4+. + The concentration is 40~60 mg / L, and the total phosphorus concentration is 2~12 mg / L.

[0011] Preferably, the entire SBR cycle takes 4 to 8 hours, of which the anaerobic influent stage takes 1 to 2 hours, the aerobic-microaerobic cycle stage takes 2 to 5 hours, and the remaining time is for sedimentation, idle time, and effluent stage.

[0012] Preferably, the volume ratio of reaction zone I, reaction zone II, and peripheral reaction zone III is approximately 2:1:4, and the water displacement ratio is above 70%.

[0013] Preferably, in step (2), the dissolved oxygen concentration in reaction zone II of the aerobic zone is 2~4 mg / L, the dissolved oxygen concentration in the middle of the outer reaction zone III of micro-aerobic zone I is less than 1 mg / L, and the dissolved oxygen concentration in reaction zone I of micro-aerobic zone II is less than 0.5 mg / L.

[0014] The PLC control unit monitors and regulates NH4 levels in each zone in real time. + By precisely adjusting the aeration intensity, the DO concentration in reaction zone II is maintained at 2.0~4.0 mg / L, ensuring that the ammonia nitrogen removal rate in this zone is controlled at around 50%, thereby achieving NH4+ removal. + Short-range nitrification promotes NO2 - The accumulation of NO3 in the device - As the mixture is generated, it enters the peripheral reaction zone III, where DO rapidly decreases to below 1.0 mg / L in a micro-aerobic environment, leaving only NH4+. + Oxidation continues. Further, the mixture is circulated through a pump within reaction zone I to enhance endogenous denitrification and simultaneous nitrogen and phosphorus removal (DO ≤ 0.5 mg / L). An online monitoring unit tracks the NH4 level in the main reactor in real time. + Sensors monitor ammonia nitrogen concentration. As the reaction proceeds and the substrate concentration decreases, the PLC control unit automatically adjusts the aeration and pump speeds based on online monitoring data to optimize the nitrogen and phosphorus removal process.

[0015] In addition, during the first and second micro-oxygen phases, the dissolved oxygen concentration in the main reactor gradually decreased to below 0.5 mg / L, and NH4+... + After short-path nitration, it is converted into NO2. -Until the ammonia nitrogen concentration is close to zero, nitrite-oxidizing bacteria (NOB) are effectively inhibited, while denitrifying polysaccharide bacteria (DGAOs) utilize NO2. - Denitrification, while denitrifying polyphosphate-accumulating bacteria (DPAOs) utilize NO2 - Denitrification continues to absorb phosphates in the water, achieving simultaneous deep removal of nitrogen and phosphorus. The effluent TN and TP removal rate of this device can reach nearly 100%, realizing "dual utilization of carbon".

[0016] Preferably, in step (2), the sludge age is controlled between 25 and 30 days, and the sludge particle size D 50 The sludge volume index is 30-60 mL / g, and the sludge concentration in the main reactor is 6-10 g / L. In step (3), the TN removal rate is 94.2±3.4%, the TP removal rate is 95.6±4.3%, and the COD removal rate is higher than 95%.

[0017] Preferably, in step (2), the abundance distribution of polyphosphate-related bacteria and denitrifying polysaccharide bacteria in the sludge is relatively balanced, with denitrifying polysaccharide bacteria being the most abundant. Candidatus Competibacter and Defluviococcus The abundances of these two bacteria were 28% and 1.84%, respectively, totaling 29.84%; among polyphosphate-related bacteria, polyphosphate-accumulating bacteria... Candida Accumulibacter The abundance was 10.01%, denitrifying polyphosphate-accumulating bacteria. Tetrasphere and Dechloromonas The abundances were 2.04% and 10%, respectively, totaling 22.05%.

[0018] Therefore, the present invention employs the above-mentioned deep nitrogen and phosphorus removal process for municipal wastewater, which has the following beneficial effects: (1) This invention achieves stable synchronous short-cut nitrification, full conversion of external carbon source to internal carbon source, and internal short-cut denitrification for phosphorus removal by carrying out anaerobic / aerobic / microaerobic processes in the main reactor. It effectively inhibits the reproduction of nitrite oxidizing bacteria. During operation, flocculent sludge and granular sludge coexist, providing a good living environment for the enrichment of functional bacteria. The nitrogen and phosphorus removal efficiency is as high as 100%, achieving deep nitrogen and phosphorus removal.

[0019] (2) The deep denitrification and phosphorus removal process of wastewater in this invention is carried out in a single main reactor. This device greatly saves aeration energy consumption, saves carbon source input, and occupies a small area.

[0020] (3) The deep nitrogen and phosphorus removal process of wastewater in this invention relies on the spatial distribution of anaerobic zone, aerobic zone and two microaerobic zones in the device to operate in a coordinated manner, forming a complete and efficient treatment cycle, with each zone having a clear functional division. In the anaerobic stage, the denitrifying polyphosphate / sugar-accumulating bacteria and polyphosphate / sugar-accumulating bacteria enriched in the device will absorb external carbon sources in the wastewater and convert them into PHA. The external carbon sources are stored in the body in the form of PHA. When absorbing external carbon sources, polyphosphate-accumulating bacteria will release the polyphosphates accumulated in their bodies; in the aerobic zone, ammonia-oxidizing bacteria will convert NH4+ into NH4+. + Partially converted to NO2 - Simultaneously, polyphosphate-accumulating bacteria decompose the PHA stored within them and absorb phosphate from the wastewater using oxygen as an electron acceptor. In this area, the dissolved oxygen concentration and aeration time during the aerobic phase are strictly controlled to ensure that NH4+ in reaction zone II is within acceptable limits. + The removal rate is 50%, preventing the proliferation of nitrite-oxidizing bacteria; microaerobic stage one zone, NH4 + Further oxidized to NO2 - Polyphosphate-accumulating bacteria further absorb phosphates from the wastewater. In the peripheral reaction zone III, the mixed liquor flows under gravity. Due to the consumption of oxygen by microorganisms, dissolved oxygen (DO) gradually decreases, preventing the growth of nitrite-oxidizing bacteria. In the microaerobic stage II zone, the mixed liquor is further pumped downwards into reaction zone I, where DO further decreases to below 0.5 mg / L. Denitrifying polyphosphate / polysaccharide bacteria utilize stored PHA as an energy source for endogenous denitrification, converting accumulated NO2... - Denitrifying polyphosphate bacteria can simultaneously utilize NO2, which is reduced to N2. - As an electron acceptor, it further absorbs phosphate, exhibiting high endogenous denitrification and phosphorus uptake rates. The overall process of this invention achieves simultaneous short-cut nitrification and endogenous denitrification for phosphorus removal, with extremely high carbon source utilization, and almost complete removal of total nitrogen and total phosphorus from wastewater.

[0021] (4) The process of the present invention can form aerobic granular sludge in a short time. The coexistence of flocs and aerobic granular sludge in the device is conducive to the coexistence of multiple functional bacteria. The aerobic granular sludge forms an aerobic-anoxic-anaerobic layer along the mass transfer direction. This unique structure is conducive to the growth of denitrifying polyphosphate bacteria and ammonia-oxidizing bacteria. The pores in the particles are also conducive to the diffusion of substances into the particles, providing a good living environment for anoxic and anaerobic microorganisms.

[0022] (5) This invention uses municipal sewage as the wastewater to be treated as the influent of the main reactor. Based on the structural optimization of the device and precise DO gradient control, it achieves efficient zoning of anaerobic-aerobic-microaerobic zones, enabling the synergistic effect of various functional bacterial groups. Deep nitrogen and phosphorus removal is achieved in one main reactor. The PLC control unit precisely controls the dissolved oxygen concentration and NH4 in each zone. + The concentration is high, the operation is feasible, and the treatment effect is good, which has certain reference value for the deep treatment process of municipal sewage.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a device for deep nitrogen and phosphorus removal from municipal wastewater. In the diagram: 1. Inlet pump; 2. Wastewater inlet; 3. Circulation inlet; 4. Outlet pump; 5. Clean water outlet; 6. Circulation outlet; 7. Circulation pump; 8. Aeration disc; 9. Aeration pump; 10. PLC control unit; 11. NH4 + Sensor monitoring probe 1; 12. Dissolved oxygen monitoring probe 1; 13. NH4 + 14. Sensor monitoring probe 2; 15. Dissolved oxygen monitoring probe 2; 16. Reaction zone I; 17. Reaction zone II; 18. Peripheral reaction zone III. Detailed Implementation

[0025] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0026] Example 1 A device for deep nitrogen and phosphorus removal in municipal wastewater includes a main reactor and an aeration unit. The main reactor has a reaction zone I, a reaction zone II, and an outer reaction zone III surrounding the reaction zone II. Both the reaction zone II and the outer reaction zone III are located above the reaction zone I. The volume ratio of the reaction zone I 15, the reaction zone II 16, and the outer reaction zone III 17 is approximately 2:1:4.

[0027] This volume ratio setting is based on a comprehensive optimization design considering the metabolic characteristics of functional microbial communities, dissolved oxygen gradient distribution, and mass transfer efficiency. In the initial influent stage, reaction zone I15 is in an anaerobic state, which is conducive to PAO and DGAO absorbing external organic carbon sources to synthesize PHA, providing energy storage for subsequent endogenous denitrification. After the aeration pump and circulation pump start operating, reaction zone II16, located near the aeration disc, forms a localized hyperoxic environment, allowing AOB to absorb NH4+. + Partially converted to NO2 - This region occupies approximately 1 / 7 of the total volume, thus strictly controlling the oxygen transfer range and preventing the formation of NO3. - In the later stages of the reaction, the outer reaction zone III17 and the bottom zone I15 transform into micro-aerobic zones, forming a large-volume low-dissolved oxygen environment. This effectively inhibits NOB growth, prolongs the residence and reaction time of DPAO and DGAO, and significantly improves the efficiency of short-cut nitrification, endogenous denitrification, and phosphorus removal. If the volume distribution is unbalanced, an excessively high proportion of aerobic zones will lead to poor dissolved oxygen control, and NH4+...+ Excessively oxidized to NO3 - Insufficient anaerobic zone ratio limits PHA synthesis, thus affecting the overall nitrogen and phosphorus removal capacity of the unit.

[0028] The main reactor is equipped with a sewage inlet 2 and a circulating inlet 3 at the bottom. The sewage inlet 2 is connected to the inlet pump 1. The upper end of the reaction zone I 15 is equipped with a clean water outlet 5, which is connected to the outlet pump 4. The aeration unit includes an aeration disc 8 located at the bottom of the reaction zone II 16 and an aeration pump 9 connected to the aeration disc 8. The lower end of the peripheral reaction zone III 17 is equipped with a circulating outlet 6. The circulating inlet 3 is connected to the circulating outlet 6 through a circulating pump 7.

[0029] The device also includes a PLC control unit 10, to which the inlet pump 1, outlet pump 4, circulation pump 7, and aeration pump 9 are all connected. The device also includes an online monitoring unit, which monitors NH4. + Sensor monitoring probe 11, dissolved oxygen monitoring probe 12 and NH4 + Sensor monitoring probe 2.13, dissolved oxygen monitoring probe 2.14, NH4 + Sensor monitoring probe 11 and NH4 + Sensor monitoring probe 2 13 is respectively set in reaction zone II 16 and the outer reaction zone III 17, and dissolved oxygen monitoring probe 1 12 and dissolved oxygen monitoring probe 2 14 are respectively set in reaction zone II 16 and the outer reaction zone III 17, NH4 + Sensor monitoring probe 11, dissolved oxygen monitoring probe 12 and NH4 + Sensor monitoring probe 2 13 and dissolved oxygen monitoring probe 14 are also connected to PLC control unit 10.

[0030] Example 2 A process for deep nitrogen and phosphorus removal from municipal wastewater includes the following steps: Simulated municipal wastewater was used as the influent substrate (Table 1), and activated sludge from a municipal sludge wastewater treatment plant was used as the inoculum sludge (MLSS: 4 g / L).

[0031] Table 1 Main Components of Influent Substrate

[0032] (1) Anaerobic influent stage The inlet pump 1 slowly delivers the wastewater (municipal wastewater) to be treated into the reaction zone I 15 of the main reactor through the sewage inlet 2 at the bottom. The water flows from bottom to top and mixes thoroughly with the high-concentration sludge in the reaction zone I 15 to achieve efficient anaerobic contact. The inlet pump 1 stops when the water level rises to the top of the reaction zone II, and the circulation pump 7 is turned on until the anaerobic phase ends. The anaerobic phase lasts for 2 hours.

[0033] During this stage, polyphosphate-accumulating bacteria (PAO / DPAO, which releases intracellularly stored phosphate) and denitrifying polysaccharide bacteria (DGAO) in the main reactor utilize external organic carbon sources to synthesize and accumulate internal carbon source polyhydroxyalkanoates (PHA), providing internal carbon sources for subsequent denitrification and phosphorus removal.

[0034] (2) Aerobic-microaerobic cycle stage After anaerobic digestion, the device enters continuous operation, with aeration pump 9 and circulation pump 7 running continuously, creating a stable circulating flow of the mixed liquor within the reactor; specifically as follows: Aerobic zone: The PLC control unit 10 precisely controls the start and stop of the aeration pump 9 and the circulation pump 7. During this stage, the aeration pump 9 and the circulation pump 7 are started, and the gas is evenly distributed from the aeration disc 8 to the bottom of the reaction zone II 16. The dissolved oxygen concentration at the top of the reaction zone II 16 is not higher than 3 mg / L, ensuring that the sludge in the aerobic zone is in full contact with oxygen. The aerobic stage lasts for 0.5 hours.

[0035] During the aerobic phase, ammonia-oxidizing bacteria (AOB) promote the oxidation of NH4+. + Oxidized to NO2 - At the same time, PAO absorbs phosphate from the water, achieving aerobic phosphorus uptake.

[0036] Micro-oxygen zone one: Then, the mixture is propelled upward by circulation. The mixture overflows from the top of reaction zone II16 into the outer reaction zone III17. In the outer reaction zone III17, the mixture flows under gravity and circulation. As microorganisms consume oxygen, the dissolved oxygen (DO) gradually decreases. The dissolved oxygen concentration in the outer reaction zone III17 is below 1 mg / L, and the dissolved oxygen concentration naturally decreases to form micro-oxygen zone I.

[0037] At this stage, the remaining NH4 + Continue to oxidize to NO2 - This creates a short-cut nitrification and denitrification environment, enabling short-cut nitrification and denitrification and creating conditions for subsequent microaerobic reactions.

[0038] Micro-oxygen zone two: The mixture is further pumped downwards by circulation pump 7 into reaction zone I15, where DO is further reduced to below 0.5 mg / L, forming micro-oxygen zone II, which further enhances the simultaneous removal of endogenous denitrification and phosphorus.

[0039] During this stage, DPAO and DGAO utilize stored PHA as an electron donor for endogenous denitrification, while DPAO completes phosphorus absorption and unconverted NH4+. +Under the action of the fluid, the mixture continues to move from reaction zone I15 to reaction zone II16. The total time for micro-oxygen stage one and micro-oxygen stage two is 4.5 hours.

[0040] After the aerobic-microaerobic cycle was completed, the ammonia nitrogen concentration was 10 mg / L, the nitrite nitrogen concentration was 2 mg / L, the nitrate nitrogen concentration was 0 mg / L, and the total phosphorus concentration was 10 mg / L.

[0041] (3) Sedimentation and effluent stage Under the influence of gravity, the sludge settles and concentrates at the bottom of reaction zone I15, entering a settling phase to enhance the microbial starvation effect. The settling time is 5 minutes. After the sedimentation is complete, the sludge is concentrated in reaction zone I15. After the settling is complete, the effluent pump 4 is turned on, and the treated water is discharged through the clean water outlet 5, completing the entire SBR cycle. The device then continues to the next cycle.

[0042] Tests revealed that denitrifying polysaccharide bacteria were present in the sludge at this time. Candidatus Competibacter At the genus level, the abundance percentage was 28%, and denitrifying polysaccharide bacteria accounted for 28%. Defluviococcus At the genus level, the abundance percentage was 1.84%, and polyphosphate-accumulating bacteria... Candidate Accumulibacter The abundance of this species was 10.01%, and it was a denitrifying polyphosphate-accumulating bacterium. Tetrasphere At the genus level, the abundance percentage was 2.04%, and denitrifying polyphosphate-accumulating bacteria... Dechloromonas The abundance percentage at the genus level was 10%.

[0043] Calculations were performed on the above Example 2. After stable operation, the concentrations of TN and TP in the purified water effluent were lower than the detection line, and the COD concentration was 6.7 mg / L, that is, the total nitrogen removal rate was 100%, the total phosphorus removal rate was 100%, and the COD removal rate was 97.7%.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A process for deep nitrogen and phosphorus removal from municipal wastewater, characterized in that: The device used includes a main reactor and an aeration unit. The main reactor is equipped with a reaction zone I, a reaction zone II, and a peripheral reaction zone III surrounding the reaction zone II. Both the reaction zone II and the peripheral reaction zone III are located above the reaction zone I. The main reactor has a wastewater inlet and a circulating inlet at the bottom. The wastewater inlet is connected to the inlet pump. The clean water outlet is located at the top of reaction zone I and is connected to the outlet pump. The aeration unit includes an aeration disc located at the bottom of reaction zone II and an aeration pump connected to the aeration disc. The circulating outlet is located at the bottom of the outer reaction zone III and is connected to the circulating inlet via a circulating pump. The process mainly includes the following steps: (1) Anaerobic influent stage The inlet pump delivers the wastewater to be treated into reaction zone I of the main reactor through the sewage inlet. During the inlet process, the water flows from bottom to top and mixes thoroughly with the sludge in reaction zone I to achieve anaerobic contact. The inlet pump stops when the water level rises to the top of reaction zone II, and the circulation pump is started until the anaerobic process ends. (2) Aerobic-microaerobic cycle stage After the anaerobic process ends, the device enters continuous operation, with the aeration pump and circulation pump running continuously, and the mixed liquor forms a stable circulating flow in the reactor. Aerobic Zone: Gas is evenly distributed throughout the reaction zone II via aeration discs at the bottom, forming an aerobic zone where sludge and oxygen are in full contact. Ammonia-oxidizing bacteria convert NH4+ into oxygen. + Oxidized to NO2 - Polyphosphate-accumulating bacteria absorb phosphate from water to achieve aerobic phosphorus uptake; Micro-oxygen zone 1: Under the action of air lift, the mixed liquor enters the peripheral reaction zone Ⅲ with the fluid movement, and the dissolved oxygen concentration naturally decreases to form micro-oxygen zone 1, realizing short-cut nitrification and denitrification; Micro-oxygen zone 2: The mixed liquor is refluxed to reaction zone 1 under the drive of the circulation pump, and the dissolved oxygen concentration further decreases, forming micro-oxygen zone 2. Denitrifying polyphosphate bacteria and denitrifying polysaccharide bacteria carry out endogenous denitrification, while denitrifying polyphosphate bacteria further absorb phosphate. In the aerobic-microaerobic cycle stage, the aerobic and microaerobic zones and the mixed liquid dual circulation process are realized simultaneously. The dual circulation process includes the internal circulation of reaction zone II and the outer reaction zone III, as well as the external circulation of the outer reaction zone III and the reaction zone I. After the aerobic-microaerobic cycle stage is completed, the aeration pump and the circulation pump are turned off. (3) Sedimentation and effluent stage The sludge settles and concentrates in the lower part of reaction zone I under the action of gravity, and enters the idle stage to enhance the microbial starvation effect. After the idle stage, the effluent pump is turned on, and the treated water is discharged through the clean water outlet, and the device enters the next cycle. In step (2), the dissolved oxygen concentration in the middle of the outer reaction zone III in micro-oxygen zone one is below 1 mg / L, and the dissolved oxygen concentration in reaction zone I in micro-oxygen zone two is below 0.5 mg / L.

2. The municipal wastewater deep nitrogen and phosphorus removal process according to claim 1, characterized in that: The device also includes a PLC control unit, and the inlet pump, outlet pump, circulation pump and aeration pump are all connected to the PLC control unit.

3. The municipal wastewater deep nitrogen and phosphorus removal process according to claim 2, characterized in that: The device also includes a dissolved oxygen monitoring probe and NH4. + Two dissolved oxygen monitoring probes are respectively set in reaction zone II and the outer reaction zone III, and two NH4+ probes are also present. + The sensor monitoring probes are respectively installed in reaction zone II and the peripheral reaction zone III.

4. The municipal wastewater deep nitrogen and phosphorus removal process according to claim 1, characterized in that: In step (1), the wastewater to be treated is municipal wastewater with a COD of 200~500 mg / L and NH4+. + The concentration is 40~60 mg / L, and the total phosphorus concentration is 2~12 mg / L.

5. The municipal wastewater deep nitrogen and phosphorus removal process according to claim 1, characterized in that: The entire SBR cycle takes 4 to 8 hours, with the anaerobic influent stage taking 1 to 2 hours, the aerobic-microaerobic cycle stage taking 2 to 5 hours, and the remaining time for sedimentation, idle time, and effluent stage.

6. The municipal wastewater deep nitrogen and phosphorus removal process according to claim 1, characterized in that: The volume ratio of reaction zone I, reaction zone II, and peripheral reaction zone III is 2:1:4, and the water displacement ratio is over 70%.

7. The municipal wastewater deep nitrogen and phosphorus removal process according to claim 1, characterized in that: In step (2), the dissolved oxygen concentration in reaction zone II of the aerobic zone is 2~4 mg / L.

8. The municipal wastewater deep nitrogen and phosphorus removal process according to claim 1, characterized in that: In step (2), the sludge age is controlled between 25 and 30 days, and the sludge particle size D 50 The sludge volume index is 30-60 mL / g, and the sludge concentration in the main reactor is 6-10 g / L. In step (3), the TN removal rate is 94.2±3.4%, the TP removal rate is 95.6±4.3%, and the COD removal rate is higher than 95%.

9. The municipal wastewater deep nitrogen and phosphorus removal process according to claim 1, characterized in that: In step (2), the abundance distribution of polyphosphate-accumulating bacteria and denitrifying polysaccharide bacteria in the sludge was relatively balanced, with denitrifying polysaccharide bacteria being the most abundant. Candidatus Competibacter and Defluviococcus The abundances were 28% and 1.84%, respectively, totaling 29.84%. Polyphosphate-associated bacteria, polyphosphate-accumulating bacteria Candidatus Accumulibacter The abundance was 10.01%, denitrifying polyphosphate-accumulating bacteria. Tetrasphere and Dechloromonas The abundances were 2.04% and 10%, respectively, accounting for a total of 22.05%.

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