Enrichment method for synchronous endogenous denitrification phosphorus removal bacteria in A2O process

Abstract

The invention discloses an enrichment method for synchronous endogenous denitrification phosphorus removal bacteria in an A2O process. Endogenous denitrifying bacteria and denitrifying phosphorus removal bacteria are screened and enriched at the same time, under the condition that equipment and facilities are not newly added, a basic A2O system is utilized, the growth and reproduction environment of microorganisms is changed by adjusting the operating parameters of an anaerobic tank, an aerobic tank and a secondary sedimentation tank, the endogenous denitrifying bacteria and the denitrifying phosphorus removal bacteria become dominant bacteria, and the phosphorus removal effect of the microorganisms is improved. And synchronous denitrifying phosphorus removal is realized by utilizing a carbon source stored in the microorganisms. According to the invention, an internal carbon source is used as an electron donor, denitrification nitrogen removal and biological phosphorus removal are synchronously completed, 'one carbon has two purposes' is realized, the utilization efficiency of the carbon source is fundamentally optimized, the nitrogen and phosphorus removal efficiency of sewage with low carbon-nitrogen ratio inflow under the condition of not adding the carbon source is improved, and energy conservation and consumption reduction are realized while stable operation is realized. The method is generally suitable for an A2O process sewage treatment plant with low-carbon-nitrogen-ratio inflow water, has very high practical application value and is easy to popularize and apply.

Description

Technical Field

[0001] This invention relates to an A 2 The enrichment method of endogenous denitrifying and phosphorus-removing bacteria in the O process belongs to the field of wastewater treatment technology. Background Technology

[0002] Biological nitrogen and phosphorus removal is a wastewater treatment technology that simultaneously removes nitrogen and phosphorus from wastewater through microbial metabolism. Its core relies on the synergistic effect of different functional microorganisms. Traditional denitrifying bacteria and aerobic polyphosphate-accumulating bacteria both depend on organic carbon sources in wastewater, leading to carbon source competition between them. This not only affects nitrogen and phosphorus removal efficiency but also necessitates the addition of external carbon sources, increasing the operating costs of wastewater treatment plants. Denitrification and phosphorus removal technology, combined with endogenous denitrification technology, solves the problem of insufficient carbon sources in traditional processes, achieving highly efficient synergistic removal of nitrogen and phosphorus.

[0003] Denitrifying polysaccharide bacteria (DGAOs) are key functional bacteria for achieving endogenous denitrification. They obtain metabolic energy by breaking down stored glycogen (Gly) during the anaerobic phase and converting volatile fatty acids (VFAs) in wastewater into endogenous polyhydroxyalkanoates (PHAs, including PHB, PHV, and PH2MV). During the anoxic phase, DGAOs utilize stored PHAs as electron donors to convert NO3- into nitrogen. - -N or NO2 - -N acts as an electron acceptor, converting NO3- into electrons. - -N or NO2 - -N is reduced to N2, achieving efficient denitrification.

[0004] Denitrifying polyphosphate (DPAOs) are a special type of facultative polyphosphate-accumulating bacteria. In anaerobic environments, DPAOs actively transport VFAs into their cells and synthesize them into polyhydroxyalkanoates (PHAs, including PHB and PHV). Under hypoxic conditions, they are converted into NO3-. - -N or NO2 - -N acts as an electron acceptor, obtaining energy by oxidizing and decomposing PHA accumulated during the anaerobic stage, thus driving cells to over-absorb PO4 from the environment. 3- -P enables efficient synergy between nitrogen and phosphorus removal.

[0005] Simultaneous endogenous denitrification for phosphorus removal is a coupling of endogenous denitrification and denitrification for phosphorus removal. Under anaerobic conditions, DGAOs and DPAOs simultaneously utilize VFAs in wastewater to synthesize PHAs as an internal carbon source for storage within the cells. Under anoxic conditions, both DGAOs and DPAOs utilize NO3-. - -N or NO2 - -N acts as an electron acceptor for denitrification, while DPAOs simultaneously perform excess phosphorus uptake, achieving "dual use of carbon." Simultaneous denitrification and phosphorus removal are particularly suitable for the treatment of wastewater with a low carbon-to-nitrogen ratio.

[0006] In conventional activated sludge process urban wastewater treatment plants, denitrifying bacteria and aerobic polyphosphate-accumulating bacteria are the dominant bacterial species for heterotrophic denitrification and biological phosphorus removal. The proportion of endogenous denitrifying bacteria (DGAOs) and denitrifying polyphosphate-accumulating bacteria (DPAOs) is relatively low, and their role in nitrogen and phosphorus removal is negligible. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention simultaneously enriches endogenous denitrifying bacteria and denitrifying polyphosphate-accumulating bacteria through process adjustments, making them dominant species for denitrification and phosphorus removal. This allows for simultaneous nitrogen and phosphorus removal in the anoxic tank, achieving "dual utilization of carbon," reducing the carbon source dosage in low-carbon-to-nitrogen ratio wastewater treatment plants, and achieving the dual goals of water quality compliance and energy conservation. Furthermore, this method utilizes traditional A... 2 The O process system requires no additional equipment or facilities.

[0008] This invention is achieved through the following technical solution: The first objective of this invention is to provide an A 2 An enrichment method for simultaneous endogenous denitrification and phosphorus removal bacteria in the O process, based on A 2 The wastewater treatment process includes the following steps: S1. Use wastewater with a carbon-to-nitrogen ratio of not less than 5 as the influent to the anaerobic tank, and inoculate the reactor with sludge at a concentration of 3500~4500 mg / L to carry out internal carbon source enrichment treatment for microorganisms. S2, Internal carbon source enrichment treatment to PO4 at the end of the anaerobic stage 3- When the -P concentration is stable at 7~9 mg / L, wastewater with a carbon-to-nitrogen ratio not higher than 2.5 is used as the influent to the anaerobic tank, and the discharge of excess sludge from the secondary sedimentation tank is stopped. The sludge retention time in the secondary sedimentation tank is increased to raise the sludge concentration at the bottom of the secondary sedimentation tank. The external reflux ratio is gradually reduced, while the sludge concentration in the reactor is still controlled at 3500~4500 mg / L. Simultaneous denitrification and phosphorus removal bacteria screening treatment is carried out. S3. Simultaneous denitrifying and phosphorus-removing bacteria screening and treatment until the return sludge concentration reaches 18-24 g / L, reducing NO3 in the sludge return liquid. - When the -N concentration is below 0.5 mg / L and the endogenous denitrification index is stable above 50%, the aeration mode of the last 1 / 4 zone of the aerobic zone is changed to the stirring mode. The DO concentration of the effluent in this zone is controlled to be below 0.5 mg / L, and simultaneous denitrification and phosphorus removal bacteria enrichment treatment is carried out to obtain enriched simultaneous endogenous denitrification and phosphorus removal bacteria.

[0009] In this invention, A 2 The wastewater treatment process includes an anaerobic zone, anoxic zone, aerobic zone, and secondary sedimentation tank.

[0010] In one embodiment of the present invention, during the internal carbon source enrichment treatment of microorganisms, the DO concentration in the anaerobic tank is controlled below 0.2 mg / L, and the NO3 concentration is controlled below 0.2 mg / L. - -N concentration <0.5mg / L, DO concentration at the end of the aerobic tank should be controlled below 2 mg / L.

[0011] In this invention, both the internal and external reflux pumps are controlled by frequency conversion, and the reflux flow rate can be adjusted by adjusting the frequency.

[0012] In one embodiment of the present invention, during the microbial internal carbon source enrichment treatment, the external return ratio of sludge from the secondary sedimentation tank to the anaerobic tank is 90%~110%, and the internal return ratio from the end of the aerobic tank to the anoxic tank is 180%~220%.

[0013] In one embodiment of the present invention, during the simultaneous screening treatment of denitrifying and phosphorus-removing bacteria, the internal reflux ratio is gradually reduced to 55-65%.

[0014] In one embodiment of the present invention, during the simultaneous denitrification and phosphorus removal bacteria screening treatment, the pH value of the effluent from the aerobic tank is between 7.0 and 8.2.

[0015] In one embodiment of the present invention, the simultaneous denitrifying and phosphorus-removing bacteria screening process also includes adding a bioflocculant to the secondary sedimentation tank.

[0016] In one embodiment of the present invention, the concentration of the bioflocculant is 0.5~1.5 mg / L.

[0017] In this invention, adding a biological flocculant to the secondary sedimentation tank can prevent the formation of floating sludge and improve the sludge settling performance.

[0018] In this invention, during the simultaneous denitrification and phosphorus removal bacteria enrichment stage, wastewater with a carbon-to-nitrogen ratio below 2.5 is used as the influent to prevent external carbon sources from reacting with NO3. - When -N is present, ordinary denitrifying bacteria preferentially carry out denitrification reactions, resulting in a lack of electron acceptors for denitrification and phosphorus removal, which affects the growth, reproduction and activity of denitrifying phosphorus removal bacteria.

[0019] In this invention, the aerobic zone is divided into two parts: a front 3 / 4 region and a rear 1 / 4 region. The rear 1 / 4 region is equipped with an aeration device and a stirring device, which can realize two operating modes: aeration or stirring. During the synchronous denitrification and phosphorus removal bacteria enrichment stage, the rear 1 / 4 region of the aerobic zone is changed from aeration mode to stirring mode, and the final DO concentration in this region is controlled to be lower than 0.5 mg / L. In some embodiments of the present invention, NO3 in the anoxic zone was observed during the simultaneous denitrification and phosphorus removal bacteria enrichment stage. - -N and PO4 3-The simultaneous decrease in -P and the decrease in nitrate nitrogen concentration in the last quarter of the aerobic zone are indicators of successful enrichment of simultaneous denitrifying phosphorus-removing bacteria.

[0020] In this invention, the endogenous denitrification index (ED / EI) (ED: endogenous denitrification, EI: denitrification potential): the ratio of the endogenous denitrification rate to the denitrification potential.

[0021] A second objective of this invention is the application of the enrichment method in wastewater treatment.

[0022] In one embodiment of the present invention, the application is to use the enrichment method to enrich synchronous endogenous denitrifying phosphorus removal bacteria, which are then used for synchronous endogenous denitrification phosphorus removal in wastewater treatment.

[0023] In one embodiment of the present invention, the wastewater treatment is a low carbon-to-nitrogen ratio wastewater treatment.

[0024] The beneficial effects of this invention are: This invention simultaneously screens and enriches endogenous denitrifying bacteria and denitrifying phosphorus-removing bacteria, utilizing basic A... 2 The O system adjusts the operating parameters of the anaerobic tank, aerobic tank, and secondary sedimentation tank to change the growth and reproduction environment of microorganisms, making endogenous denitrifying bacteria and denitrifying phosphorus removal bacteria the dominant species, and using the carbon source stored inside the microorganisms to achieve simultaneous denitrification and phosphorus removal.

[0025] Experimental results show that this method uses an internal carbon source as an electron donor to simultaneously complete denitrification and biological phosphorus removal, achieving "dual utilization of carbon." This fundamentally optimizes carbon source utilization efficiency and improves the nitrogen and phosphorus removal efficiency of wastewater with a low carbon-to-nitrogen ratio influent without the addition of a carbon source. It also achieves energy conservation and consumption reduction while maintaining stable operation. This method requires no additional equipment or facilities, is simple to operate, and is widely applicable to wastewater with a low carbon-to-nitrogen ratio influent. 2 The O process wastewater treatment plant has high practical application value and is easy to promote and apply. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The endogenous denitrification index; Figure 2 NO3 at the front and end of the anoxic pool - -N,PO4 3- -P concentration; Figure 3 NO3 at the front and rear of the aerobic tank in the last quarter zone - -N concentration. Detailed Implementation

[0028] The present invention will be further illustrated below with specific examples. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0029] The technical solution of the present invention will be described in detail below with reference to specific embodiments. In the following embodiments, unless otherwise specified, the reagents, materials and equipment used can be purchased commercially, prepared by conventional methods, or commonly used in the industry.

[0030] Example 1: The specific A2O process flow: 1. Microbial internal carbon source enrichment stage: Select an effective volume of 8L of A 2 The reactor and secondary sedimentation tank have an effective volume of 2L. The effective volume ratio of the anaerobic tank:anoxic tank:aerobic tank is 2:4:8. Wastewater treatment plant wastewater sludge is inoculated. 2 The sludge concentration in the O reactor was controlled at around 4000 mg / L. Influent from a certain domestic wastewater treatment plant (with a carbon-to-nitrogen ratio higher than 5) was selected as the reactor influent. The water quality concentrations are shown in Table 1. The influent flow rate was 0.5 L / h. The control parameters for each process section are as follows: DO concentration in the A2O anaerobic tank was controlled below 0.2 mg / L, and NO3... - -N concentration <0.5mg / L, DO concentration at the end of the aerobic tank controlled below 2 mg / L, internal and external reflux ratios of 100% and 200% respectively, SRT controlled at around 20 days, and after 8 days of operation, the orthophosphorus concentration at the end of the anaerobic tank stabilized above 8 mg / L.

[0031] Table 1. Influent water quality during the microbial internal carbon source enrichment stage

[0032] 2. Simultaneous Denitrification and Phosphorus Removal Bacteria Screening Stage: Wastewater from a wastewater treatment plant with a carbon-to-nitrogen ratio below 2.5 was used as the A2O system influent. Excess sludge discharge was stopped, leading to an increase in sludge volume and level in the secondary sedimentation tank, and an increase in the concentration of returned sludge. The frequency of the return pump was reduced, gradually decreasing the internal return ratio, and the sludge concentration in the biological tank was controlled at approximately 4000 mg / L. At this point, the pH of the aerobic tank effluent was between 7.2 and 7.4. After approximately 15 days of sludge discharge cessation, severe floating sludge appeared on the surface of the secondary sedimentation tank. 1.0 mg / L of biological flocculant was added to the aerobic tank effluent. The floating sludge gradually decreased on the second day of operation. Starting from day 15, the endogenous denitrification index was measured every 5 days. After 40 days of sludge discharge cessation, the returned sludge concentration rose to approximately 22 g / L. When the nitrate nitrogen concentration in the sludge return liquid was below 0.2 mg / L, the endogenous denitrification index (ED EI) of the returned sludge stabilized above 54%, as shown in the results. Figure 1 As shown.

[0033] Table 2. Influent water quality during the screening stage of simultaneous denitrification and phosphorus removal bacteria

[0034] 3. Simultaneous denitrification and phosphorus removal bacteria enrichment stage: In the last quarter of the aerobic zone, the aeration mode was changed to stirring mode, and DO was measured along the entire process. In the middle section of the last quarter, the DO concentration had decreased to below 0.2 mg / L. Nitrate nitrogen and phosphate concentrations were measured at the beginning and end of the anoxic zone, and nitrate nitrogen concentrations were measured at the beginning and end of the last quarter of the aerobic zone. The results are as follows: Figure 2 , Figure 3 As shown.

[0035] Depend on Figure 2 It can be seen that after entering the third stage of simultaneous denitrification and phosphorus removal bacteria enrichment, the effect of simultaneous denitrification and phosphorus removal gradually increases. After the third day, the effect of simultaneous denitrification and phosphorus removal tends to stabilize. By the 15th day, NO3 in the anoxic stage... - The average concentration of -N decreased from 4.33 mg / L at the front end to 0.82 mg / L, and the PO4 concentration decreased. 3- The average phosphorus concentration decreased from 6.09 mg / L to 1.89 mg / L, and the simultaneous denitrification phosphorus removal effect remained stable.

[0036] Depend on Figure 3 It can be seen that after the aerobic tank's last quarter section was switched to stirring mode, the endogenous denitrification effect gradually increased, and the NO3 at the front and rear ends decreased. - The NO3-N concentration gradient increased from approximately 1.02 mg / L to around 3 mg / L. After stabilization, the NO3- concentration gradient in this region decreased. - The average nitrogen removal was 3.72 mg / L, indicating good endogenous denitrification.

[0037] Comparative Example 1: The only difference from Example 1 is that, during the simultaneous denitrification and phosphorus removal bacteria enrichment stage, an influent with a C / N ratio greater than 5 is still used. Other control parameters remain the same as in Example 1. After approximately 40 days of sludge discharge being stopped during this stage, the endogenous denitrification index (EDEI) stabilizes above 51%. After 15 days of operation in the simultaneous denitrification and phosphorus removal bacteria enrichment stage, the NO3 in the anoxic tank... - -N decreased by an average of 5.13 mg / L, PO4 3- The average phosphorus concentration decreased by 0.57 mg / L, but the simultaneous denitrification phosphorus removal effect was not significant. The reason for this was that the influent organic matter concentration was high, and the bacteria in the anoxic tank that utilize carbon sources for denitrification became the dominant species, competing with the denitrifying phosphorus removal bacteria for NO3. - -N deprives denitrifying phosphorus-removing bacteria of electron acceptors, thus affecting the enrichment of this bacterial community.

[0038] Comparative Example 2: The only difference from Example 1 is that, during the simultaneous denitrification and phosphorus removal bacteria enrichment stage, the last quarter of the aerobic zone was not switched to a stirred operation mode. The DO concentration at the end of the aerobic tank remained at around 2 mg / L. After 15 days of operation, the NO3 concentration in the anoxic tank... - -N decreased by an average of 1.75 mg / L, PO4 3- The average phosphorus concentration decreased by 0.17 mg / L, resulting in virtually no phosphorus removal through simultaneous denitrification. Analysis revealed that the dissolved oxygen (DO) carried by the internal recirculation disrupted the anoxic environment of the anoxic tank. Denitrifying polyphosphate (PPA) bacteria are highly sensitive to DO concentrations, thus affecting their growth, reproduction, and activity. Furthermore, due to the poor anoxic environment and low influent organic matter concentration in the anoxic tank, the denitrification bacteria utilizing carbon sources failed to perform denitrification effectively, leading to an increase in NO3 in the anoxic tank. - -N concentration decreased less.

[0039] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A type of A 2 The method for enriching endogenous denitrifying and phosphorus-removing bacteria in the O process is characterized by, Based on A 2 The wastewater treatment process includes the following steps: S1. Use wastewater with a carbon-to-nitrogen ratio of not less than 5 as the influent to the anaerobic tank, and inoculate the reactor with sludge at a concentration of 3500~4500 mg / L to carry out internal carbon source enrichment treatment for microorganisms. S2, Internal carbon source enrichment treatment to PO4 at the end of the anaerobic stage 3- When the -P concentration is stable at 7~9 mg / L, wastewater with a carbon-to-nitrogen ratio not higher than 2.5 is used as the influent to the anaerobic tank, and the discharge of excess sludge from the secondary sedimentation tank is stopped. The sludge retention time in the secondary sedimentation tank is increased to raise the sludge concentration at the bottom of the secondary sedimentation tank. The external reflux ratio is gradually reduced, while the sludge concentration in the reactor is still controlled at 3500~4500 mg / L. Simultaneous denitrification and phosphorus removal bacteria screening treatment is carried out. S3. Simultaneous denitrifying and phosphorus-removing bacteria screening and treatment until the return sludge concentration reaches 18-24 g / L, reducing NO3 in the sludge return liquid. - When the -N concentration is below 0.5 mg / L and the endogenous denitrification index is stable above 50%, the aeration mode of the last 1 / 4 zone of the aerobic zone is changed to the stirring mode. The DO concentration of the effluent in this zone is controlled to be below 0.5 mg / L, and simultaneous denitrification and phosphorus removal bacteria enrichment treatment is carried out to obtain enriched simultaneous endogenous denitrification and phosphorus removal bacteria.

2. The enrichment method according to claim 1, characterized in that, During the microbial internal carbon source enrichment treatment, the DO concentration in the anaerobic tank is controlled below 0.2 mg / L, and the NO3 concentration is controlled below 0.2 mg / L. - -N concentration <0.5mg / L.

3. The enrichment method according to claim 1 or 2, characterized in that, When enriching carbon sources within microorganisms, the DO concentration at the end of the aerobic tank should be controlled below 2 mg / L.

4. The enrichment method according to claim 1, characterized in that, When the internal carbon source is enriched by microorganisms, the external return ratio of sludge from the secondary sedimentation tank to the anaerobic tank is 90%~110%, and the internal return ratio from the end of the aerobic tank to the anoxic tank is 180%~220%.

5. The enrichment method according to claim 1, characterized in that, During the simultaneous screening treatment of denitrifying and phosphorus-removing bacteria, the internal reflux ratio was gradually reduced to 55-65%.

6. The enrichment method according to claim 1, characterized in that, During the simultaneous denitrification and phosphorus removal bacteria screening treatment, the pH value of the aerobic tank effluent is between 7.0 and 8.

2.

7. The enrichment method according to claim 1 or 6, characterized in that, The simultaneous screening and treatment of denitrifying and phosphorus-removing bacteria also includes adding bioflocculants to the secondary sedimentation tank.

8. The enrichment method according to claim 7, characterized in that, The concentration of the bio-flocculant is 0.5~1.5 mg / L.

9. The application of the enrichment method according to any one of claims 1 to 8 in wastewater treatment, wherein the application is to enrich the simultaneous endogenous denitrifying phosphorus-removing bacteria by the enrichment method and use them for simultaneous endogenous denitrification phosphorus removal in wastewater treatment.

10. The application according to claim 9, characterized in that, The wastewater treatment mentioned is a low carbon-to-nitrogen ratio wastewater treatment.

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