Method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process

Abstract

The application relates to the sewage treatment technical field and discloses a method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process, which comprises the following steps: building an A2O process reactor, inoculating active sludge, and forming an initial liquid phase environment; adding composite modified biological filler and domesticating a biofilm to construct a solid-liquid composite system for strengthening denitrification and pollution reduction; executing preset process parameters to make the solid-liquid composite reaction system enter a benchmark steady state operation; starting closed-loop feedback regulation, monitoring and adjusting an ORP gradient to intervene in microbial metabolism; starting feedforward regulation, monitoring an influent carbon-nitrogen ratio, and supplementing a carbon source with raw water when the carbon-nitrogen ratio is lower than a threshold value; and maintaining low-yield operation of sludge under the synergistic regulation, controlling the total amount and discharging reduced sludge; the application maintains the oxidation-reduction potential gradient between an anoxic tank and an aerobic tank, combines the magnetite action in the composite modified biological filler, induces the metabolic path of microorganisms to deviate to endogenous respiration, and optimizes energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically a method for in-situ sludge reduction using modified biological packing material to enhance the A2O process. Background Technology

[0002] The A2O process, as a mature biological nitrogen and phosphorus removal technology, has been widely used in urban wastewater treatment. This process utilizes the synergistic metabolic effects of different microbial communities within activated sludge to effectively remove pollutants such as organic matter, nitrogen, and phosphorus from water bodies by setting up three functional zones: anaerobic, anoxic, and aerobic.

[0003] In conventional A2O process applications, the system primarily relies on suspended activated sludge. The core of its operation and control is typically maintaining a relatively constant dissolved oxygen (DO) level in the aerobic tank to ensure sufficient nitrification. When treating wastewater with a low carbon-to-nitrogen ratio, to ensure denitrification efficiency in the anoxic zone, exogenous chemical agents such as methanol and sodium acetate are commonly added as supplementary carbon sources. This operating mode constitutes the basic form of current A2O process applications.

[0004] However, existing A2O process control logic typically prioritizes pollutant removal, neglecting the regulation of biological metabolism. This results in a large amount of organic matter being used to synthesize new cells, leading to a massive amount of excess sludge. Simple suspended sludge systems are sensitive to fluctuations in hydraulic load, easily experiencing sludge bulking and loss, thus affecting operational stability. Therefore, this invention provides a method for in-situ sludge reduction in the A2O process using modified biological packing material, addressing the shortcomings of existing technologies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for in-situ sludge reduction by enhancing the A2O process with modified biological packing materials, which solves the problems of high sludge production, high operating costs, and poor system stability in existing A2O processes.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for in-situ sludge reduction using modified biological packing material to enhance the A2O process, comprising the following steps: S1. Construct an A2O process reactor consisting of an anaerobic tank, an anoxic tank, and an aerobic tank connected in series, set the volume ratio and total hydraulic retention time, and inoculate the anoxic tank and the aerobic tank with activated sludge to generate an initial liquid phase environment with basic biological treatment capabilities. S2. Add composite modified biological packing material to the generated initial liquid phase environment, and carry out biofilm acclimatization through continuous water intake operation. Cultivate a biofilm with catalytic activity on the surface of the composite modified biological packing material to form a solid-liquid composite reaction system for enhanced denitrification and pollution reduction. S3. Based on the solid-liquid composite reaction system, execute the preset process operating parameters, including internal and external reflux and dissolved oxygen concentration in the aerobic tank, so that the A2O process reactor enters the baseline steady-state operating state. S4. Under the aforementioned baseline steady-state operating conditions, a closed-loop feedback control is initiated. By monitoring the redox potential difference between the anoxic tank and the aerobic tank in real time and dynamically adjusting the aeration rate and internal reflux ratio, a redox potential gradient driving microbial metabolic intervention is constructed and maintained between the anoxic tank and the aerobic tank. S5. In coordination with closed-loop feedback control, feedforward control is initiated. By monitoring the influent carbon-nitrogen ratio in real time, when the influent carbon-nitrogen ratio is lower than the preset threshold, a temporary supply flow path is established by directly pumping raw water into the anoxic tank as a supplementary carbon source. S6. Under the coordinated control mode of closed-loop feedback control and feedforward control, the A2O process reactor is kept in a stable state with low sludge production rate in order to control the total amount of activated sludge and discharge the sludge generated after the corresponding reduction.

[0007] The composite modified biofiller is composed of powdered activated carbon and magnetite powder supported on a porous carrier framework. Powdered activated carbon (PAC): Provides specific surface area and pore structure, offering attachment sites for microorganisms, promoting the formation of stable biofilms with high biomass, and enhancing its adsorption capacity for organic matter and resistance to shock loads. Simultaneously, PAC's inherent adsorption properties help enrich pollutants, creating favorable conditions for biodegradation.

[0008] Magnetite (Fe3O4): As a conductive mineral, magnetite promotes extracellular electron transfer (EET), acting as an electron shuttle between microorganisms or directly as an electron acceptor to enhance the redox activity of microorganisms and strengthen the organic matter degradation efficiency and denitrification rate in the nitrogen removal process of heterotrophic microorganisms. Furthermore, magnetite induces or selectively enriches microorganisms with special metabolic functions, such as iron-reducing bacteria, whose metabolic processes contribute to the decomposition of sludge components (such as extracellular polymeric substances, EPS). These synergistic effects construct an efficient and stable solid-liquid composite reaction system.

[0009] By controlling the redox potential difference (ΔORP) between the anoxic and aerobic tanks through closed-loop feedback, precise control of the microbial microenvironment is achieved. Nitrification-denitrification optimization: An appropriate ΔORP gradient can precisely control the dissolved oxygen level in the aerobic zone and the low oxygen state in the anoxic zone, ensuring the optimal activity of nitrifying and denitrifying bacteria. Sufficient oxygen in the aerobic zone is conducive to the complete nitrification of ammonia nitrogen, while the anoxic zone uses the internally refluxed nitrate nitrogen for denitrification by controlling the low ORP environment, thereby improving the total nitrogen removal rate.

[0010] Microbial metabolic regulation and sludge reduction: A maintained ORP gradient can induce microorganisms to shift from metabolic pathways primarily used for growth and proliferation to pathways more focused on energy maintenance and endogenous respiration. Under specific redox conditions, this may promote microbial cell autolysis, protozoan predation of bacteria, and the evolution of microbial community structure towards lower sludge yields, thereby reducing the microbial growth productivity coefficient.

[0011] The feedforward control system monitors the influent C / N ratio in real time and automatically replenishes carbon source when the C / N ratio is insufficient. Ensuring denitrification efficiency: Carbon source is an essential electron donor in the denitrification process. Insufficient C / N ratio will severely limit the activity of denitrifying bacteria, leading to nitrate nitrogen accumulation and a decrease in total nitrogen removal rate. Intelligent carbon source replenishment ensures that there is always sufficient electron donor in the anoxic zone, maintaining efficient denitrification.

[0012] Optimizing microbial metabolism: Adequate and timely carbon source supply combined with ORP regulation can guide microorganisms to use more energy for pollutant removal rather than biomass proliferation. For example, some organic matter can be directly used for heterotrophic denitrification, rather than being completely converted into new biomass, which helps to reduce the sludge yield coefficient and further promote sludge reduction.

[0013] The introduction of composite modified biological packing, control of redox potential gradient, and intelligent supplementation of carbon source, through comprehensive intervention of microbial growth environment and metabolic pathway, establish process conditions for driving low sludge production. While maintaining high pollutant removal performance, it can effectively reduce the net amount of residual sludge by regulating the growth, metabolism and community structure of microorganisms, and ultimately achieve in-situ sludge reduction and total sludge control.

[0014] Preferably, the composite modified biological filler comprises powdered activated carbon and magnetite powder, wherein the mass ratio of the powdered activated carbon to the magnetite powder is 2.5-3.5:1.

[0015] Preferably, the preparation steps of the composite modified biological filler specifically include: The powdered activated carbon and magnetite powder are mixed and dispersed in water according to a ratio of 2.5-3.5 parts by weight, 1 part by weight, and 21-30 parts by weight of water to prepare a uniform suspension. Take 21-30 parts by weight of the porous carrier skeleton and immerse it completely in the prepared suspension for impregnation and loading treatment. The porous carrier skeleton that has undergone impregnation and loading treatment is dried to obtain the composite modified biological filler.

[0016] Preferably, in step S1, the effective volume ratio of the anaerobic tank, the anoxic tank, and the aerobic tank is set to 1:1.5:3, and the total hydraulic retention time is controlled at 8-12 hours.

[0017] Preferably, in step S2, the volume of the composite modified biological packing is 18-22% of the effective volume of the anoxic pool, and the acclimatization period of the biofilm is 25 days.

[0018] Preferably, in step S3, the preset process operating parameters include: The internal reflux ratio is set to 200-250%; The external reflux ratio is set to 80%; The dissolved oxygen concentration in the aerobic tank is controlled at 2.0-3.0 mg / L.

[0019] Preferably, step S4 further includes: The closed-loop feedback control uses a 10-minute calculation and adjustment cycle. The oxidation-reduction potential gradient is maintained within the target control range of 250-400mV by dynamically adjusting the aeration rate of the blower and the speed of the internal reflux pump in the aerobic tank through frequency conversion.

[0020] Preferably, in step S5, the feedforward control is achieved through linkage control between the online water quality analyzer and the bypass metering pump, and the preset threshold for the influent carbon-nitrogen ratio is 4.8-5.2.

[0021] Preferably, when the carbon-nitrogen ratio of the influent is lower than the preset threshold, the bypass metering pump is automatically started to deliver 8-12% of the total influent flow rate of raw water to the front end of the anoxic tank for carbon source replenishment.

[0022] Preferably, in step S6, controlling the total amount of activated sludge specifically involves: maintaining a horizontal level of suspended solids concentration in the mixed liquor at the end of the aerobic tank, and quantitatively discharging the remaining sludge.

[0023] This invention provides a method for in-situ sludge reduction in the A2O process using modified biological packing material. It has the following beneficial effects: 1. This invention constructs and maintains a redox potential gradient between the anoxic and aerobic tanks, and combines this with the electron shuttle and catalytic effects of magnetite in the composite modified biological packing material to induce a shift in the metabolic pathway of microorganisms towards endogenous respiration, thereby optimizing energy utilization efficiency. This effectively inhibits the net proliferation rate of microorganisms, thus reducing the yield of excess sludge and decreasing subsequent costs and environmental burden associated with sludge disposal.

[0024] 2. By introducing composite modified biological packing material, the specific surface area of ​​which is enriched with high concentrations of functional microorganisms, a composite system of biofilm and activated sludge coexisting is formed, which enhances the system's resistance to hydraulic and load shocks. The promoting effect of magnetite on the extracellular electron transfer of microorganisms strengthens the denitrification process. Combined with the carbon-nitrogen ratio feedforward regulation to ensure the carbon source for denitrification, it can maintain a stable and efficient chemical oxygen demand and total nitrogen removal rate even under fluctuating influent water quality.

[0025] 3. This invention integrates a closed-loop feedback system based on ORP gradient and a feedforward control system based on carbon-nitrogen ratio, achieving automation and precision in process operation. Precise control of the ORP gradient allows for dynamic adjustment of aeration volume according to the actual metabolic needs of microorganisms, avoiding energy consumption caused by over-aeration. Simultaneously, utilizing raw water as a supplementary carbon source replaces expensive external chemical agents, thereby reducing the overall operating cost of the wastewater treatment plant by saving on electricity and chemical consumption. Attached Figure Description

[0026] Figure 1 This is a flowchart of the method steps of the present invention; Figure 2 This is a schematic diagram of sludge reduction according to the present invention; Figure 3 This is a schematic diagram illustrating the pollutant removal performance of the present invention. Detailed Implementation

[0027] The main raw materials and reagents used in the following preparation examples, embodiments and comparative examples are as follows. Unless otherwise specified, all reagents are commercially available analytical grade or higher grade products.

[0028] Powdered Activated Carbon (PAC): CAS No.: 7440-44-0.

[0029] Magnetite (Fe3O4) powder: CAS No.: 1317-61-9.

[0030] Glucose: CAS No.: 50-99-7.

[0031] Sodium acetate: CAS No.: 127-09-3.

[0032] Ammonium chloride: CAS No.: 12125-02-9.

[0033] Potassium dihydrogen phosphate: CAS No.: 7778-77-0.

[0034] Preparation Examples 1-3.

[0035] Preparation Example 1: Weigh the raw materials according to the following proportions: 2.5 parts of powdered activated carbon (PAC) and 1 part of magnetite (Fe3O4) powder. Add the weighed powders to 28-30 parts of deionized water, start a mechanical stirrer at 300 rpm for 30 minutes at room temperature to prepare a uniform suspension.

[0036] Take 28-30 parts by dry weight of polyurethane (PU) sponge filler and completely immerse it in the prepared suspension. Use a mechanical device to periodically squeeze and relax the immersed filler at a frequency of 12 times / minute for 40 minutes to ensure that the particles in the suspension fully enter and adhere to the internal skeleton of the filler.

[0037] The impregnated and loaded packing material was removed, and excess liquid in the pores was removed using a roller press. The packing material was then laid flat on a tray and placed in a forced-air drying oven, where it was dried at a constant temperature of 60°C for 14 hours until it reached constant weight. After cooling to room temperature, the composite modified biological packing material, denoted as S1, was obtained.

[0038] Preparation Example 2: Weigh the raw materials according to the following mass proportions: 3.0 parts of powdered activated carbon (PAC) and 1 part of magnetite (Fe3O4) powder. Add the weighed powders to 24-26 parts of deionized water, start a mechanical stirrer at 350 rpm for 30 minutes at room temperature to prepare a uniform suspension.

[0039] Take 24-26 parts by dry weight of polyurethane (PU) sponge filler and completely immerse it in the prepared suspension. Use a mechanical device to periodically squeeze and relax the immersed filler at a frequency of 12 times / minute for 40 minutes to ensure that the particles in the suspension fully enter and adhere to the internal skeleton of the filler.

[0040] The impregnated and loaded packing material was removed, and excess liquid in the pores was removed using a roller press. The packing material was then laid flat on a tray and placed in a forced-air drying oven, where it was dried at a constant temperature of 65°C for 12 hours until it reached constant weight. After cooling to room temperature, the composite modified biological packing material, denoted as S2, was obtained.

[0041] Preparation Example 3: Weigh the raw materials according to the following mass proportions: 3.5 parts of powdered activated carbon (PAC) and 1 part of magnetite (Fe3O4) powder. Add the weighed powders to 21-23 parts of deionized water, start a mechanical stirrer at 400 rpm for 25 minutes at room temperature to prepare a uniform suspension.

[0042] Take 21-23 parts by dry weight of polyurethane (PU) sponge filler and completely immerse it in the prepared suspension. Use a mechanical device to periodically squeeze and relax the immersed filler at a frequency of 12 times / minute for 40 minutes to ensure that the particles in the suspension fully enter and adhere to the internal skeleton of the filler.

[0043] The impregnated and loaded packing material was removed, and excess liquid in the pores was removed using a roller press. The packing material was then laid flat on a tray and placed in a forced-air drying oven, where it was dried at a constant temperature of 70°C for 10 hours until it reached constant weight. After cooling to room temperature, the composite modified biological packing material, denoted as S3, was obtained.

[0044] Please see the appendix Figure 1 Examples 1-3.

[0045] Example 1: This embodiment provides a method for in-situ sludge reduction using modified biological packing material to enhance the A2O process, including the following steps: S1. Construct an A2O process reactor consisting of an anaerobic tank, an anoxic tank, and an aerobic tank connected in series. The effective volume ratio of the three tanks is set to 1:1.5:3, and the total hydraulic retention time (HRT) of the system is controlled to be 10 hours. Recycled activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant is inoculated into the anoxic and aerobic tanks to achieve an initial mixed liquor suspended solids concentration (MLSS) of 3500 mg / L.

[0046] S2. The composite modified biological packing material S1 prepared in Preparation Example 1 is added to the anoxic tank, with an addition volume of 18% of the effective volume of the anoxic tank. The submersible agitator in the anoxic tank is started to bring the packing material into a uniform suspended fluidized state. Biofilm acclimation is carried out by continuously feeding water at 50% of the design load for 25 days, until a uniform and dense biofilm forms on the surface of the packing material, and the removal rates of COD and ammonia nitrogen by the system remain stable for one week.

[0047] S3. After the biofilm acclimatization is completed, adjust the system to normal operating conditions. Set the internal reflux ratio to 200%, the external reflux ratio to 80%, and control the dissolved oxygen (DO) concentration in the aerobic tank at 2.0 mg / L.

[0048] S4. Start the online ORP monitoring and PLC control system. Set the target control range for the oxidation-reduction potential difference (ΔORP) between the anoxic tank and the aerobic tank to 250-300mV. The PLC system uses a 10-minute calculation and adjustment cycle, and adjusts the aeration rate of the blower in the aerobic tank and the speed of the internal return pump through frequency conversion to maintain ΔORP within the set target range in real time.

[0049] S5. Initiate the linkage control between the online water quality analyzer and the bypass metering pump, setting the C / N ratio threshold for the influent to 4.8. When the online analyzer detects that the influent C / N ratio remains below 4.8 for 30 consecutive minutes, the PLC automatically starts the bypass metering pump, directly pumping 8% of the total influent flow rate of the primary sedimentation tank effluent into the front end of the anoxic tank for carbon source replenishment. Once the C / N ratio recovers to above 4.8 and stabilizes for 30 minutes, the PLC automatically shuts off the bypass metering pump.

[0050] S6. The system discharges a fixed amount of excess sludge daily based on the MLSS concentration at the end of the aerobic tank (maintained at 4000 mg / L), and accurately records the discharge volume. Simultaneously, the system continuously monitors the influent and effluent water quality, and calculates the apparent sludge yield coefficient and pollutant removal rate.

[0051] Example 2: This embodiment provides a method for in-situ sludge reduction using modified biological packing material to enhance the A2O process, including the following steps: S1. Construct an A2O process reactor consisting of an anaerobic tank, an anoxic tank, and an aerobic tank connected in series. The effective volume ratio of the three tanks is set to 1:1.5:3, and the total hydraulic retention time (HRT) of the system is controlled to be 10 hours. Recycled activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant is inoculated into the anoxic and aerobic tanks to achieve an initial mixed liquor suspended solids concentration (MLSS) of 3500 mg / L.

[0052] S2. The composite modified biological packing material S2 prepared in Preparation Example 2 is added to the anoxic tank, with an addition volume of 20% of the effective volume of the anoxic tank. The submersible agitator in the anoxic tank is started to bring the packing material into a uniform suspended fluidized state. Biofilm acclimation is carried out by continuously feeding water at 50% of the design load for 25 days, until a uniform and dense biofilm forms on the surface of the packing material, and the removal rates of COD and ammonia nitrogen by the system remain stable for one week.

[0053] S3. After the biofilm acclimatization is completed, adjust the system to normal operating conditions. Set the internal reflux ratio to 200%, the external reflux ratio to 80%, and control the dissolved oxygen (DO) concentration in the aerobic tank at 2.5 mg / L.

[0054] S4. Start the online ORP monitoring and PLC control system. Set the target control range for the oxidation-reduction potential difference (ΔORP) between the anoxic tank and the aerobic tank to 300-350mV. The PLC system uses a 10-minute calculation and adjustment cycle, and adjusts the aeration rate of the blower in the aerobic tank and the speed of the internal return pump through frequency conversion to maintain ΔORP within the set target range in real time.

[0055] S5. Activate the linkage control between the online water quality analyzer and the bypass metering pump. Set the C / N ratio threshold for the influent to 5.0. When the online analyzer detects that the influent C / N ratio remains below 5.0 for 30 consecutive minutes, the PLC automatically starts the bypass metering pump, directly pumping 10% of the total influent flow rate of the primary sedimentation tank effluent into the front end of the anoxic tank for carbon source replenishment. Once the C / N ratio recovers to above 5.0 and stabilizes for 30 minutes, the PLC automatically shuts off the bypass metering pump.

[0056] S6. The system discharges a fixed amount of excess sludge daily based on the MLSS concentration at the end of the aerobic tank (maintained at 4000 mg / L), and accurately records the discharge volume. Simultaneously, the system continuously monitors the influent and effluent water quality, and calculates the apparent sludge yield coefficient and pollutant removal rate.

[0057] Example 3: This embodiment provides a method for in-situ sludge reduction using modified biological packing material to enhance the A2O process, including the following steps: S1. Construct an A2O process reactor consisting of an anaerobic tank, an anoxic tank, and an aerobic tank connected in series. The effective volume ratio of the three tanks is set to 1:1.5:3, and the total hydraulic retention time (HRT) of the system is controlled to be 10 hours. Recycled activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant is inoculated into the anoxic and aerobic tanks to achieve an initial mixed liquor suspended solids concentration (MLSS) of 3500 mg / L.

[0058] S2. The composite modified biological packing material S3 prepared in Preparation Example 3 is added to the anoxic tank, with an addition volume of 22% of the effective volume of the anoxic tank. The submersible agitator in the anoxic tank is started to bring the packing material into a uniform suspended fluidized state. Biofilm acclimation is carried out by continuously feeding water at 50% of the design load for 25 days, until a uniform and dense biofilm forms on the surface of the packing material, and the removal rates of COD and ammonia nitrogen by the system remain stable for one week.

[0059] S3. After the biofilm acclimatization is completed, adjust the system to normal operating conditions. Set the internal reflux ratio to 250%, the external reflux ratio to 80%, and control the dissolved oxygen (DO) concentration in the aerobic tank at 3.0 mg / L.

[0060] S4. Start the online ORP monitoring and PLC control system. Set the target control range for the oxidation-reduction potential difference (ΔORP) between the anoxic tank and the aerobic tank to 350-400mV. The PLC system uses a 10-minute calculation and adjustment cycle to adjust the aeration rate of the blower in the aerobic tank and the speed of the internal return pump in real time, thereby maintaining ΔORP within the set target range.

[0061] S5. Initiate the linkage control between the online water quality analyzer and the bypass metering pump. Set the C / N ratio threshold for the influent to 5.2. When the online analyzer detects that the influent C / N ratio remains below 5.2 for 30 consecutive minutes, the PLC automatically starts the bypass metering pump, directly pumping 12% of the total influent flow rate of the primary sedimentation tank effluent into the front end of the anoxic tank for carbon source replenishment. Once the C / N ratio recovers to above 5.2 and stabilizes for 30 minutes, the PLC automatically shuts off the bypass metering pump.

[0062] S6. The system discharges a fixed amount of excess sludge daily based on the MLSS concentration at the end of the aerobic tank (maintained at 4000 mg / L), and accurately records the discharge volume. Simultaneously, the system continuously monitors the influent and effluent water quality, and calculates the apparent sludge yield coefficient and pollutant removal rate.

[0063] Comparative examples 1-5.

[0064] Comparative Example 1: Compared with Example 2, the difference is that this comparative example uses the conventional A2O process, no biological packing is added to the reactor, and the ORP gradient feedback control and influent C / N ratio feedforward control strategies are not implemented. All other aspects are the same.

[0065] Comparative Example 2: Compared with Example 2, the difference is that the modified biological packing material used in this comparative example is only prepared by loading PAC with PU sponge (no Fe3O4 powder is added during the preparation process, and the other preparation parameters are the same as in Example 2). The ORP gradient feedback control and feedforward control strategy of influent C / N ratio are not implemented, but everything else is the same.

[0066] Comparative Example 3: Compared with Example 2, the difference is that the modified biological packing used in this comparative example is only prepared by loading Fe3O4 powder onto PU sponge (no PAC is added during the preparation process, and the other preparation parameters are the same as in Example 2). The ORP gradient feedback control and feedforward control strategy of influent C / N ratio are not implemented, but everything else is the same.

[0067] Comparative Example 4: Compared with Example 2, the difference is that although the same composite modified biological packing material S2 as in Example 2 was added to the anoxic tank in this comparative example, the ORP gradient feedback control and influent C / N ratio feedforward control strategy were not implemented. It was operated according to the constant parameters of the conventional A2O process, and everything else was the same.

[0068] Comparative Example 5: The difference between this comparative example and Example 2 is that the PU sponge filler added to the anoxic tank was unmodified, while the rest were the same.

[0069] Test Examples 1-3.

[0070] Please see the appendix Figure 2 Test Example 1: Experimental objective: To test the sludge reduction performance of different processes by quantitatively measuring and comparing the average apparent sludge yield coefficients of each embodiment and the comparative embodiment under long-term stable operating conditions.

[0071] Experimental steps: The A2O reactor systems of Examples 1-3 and Comparative Examples 1-5 were operated continuously and stably for 30 days under the set conditions.

[0072] During this period, excess sludge was discharged daily from the end of the aerobic tanks of each system at set times to maintain the MLSS concentration within a constant range of (4000±200) mg / L. The daily volume of excess sludge discharged was accurately recorded. Samples of the remaining sludge were collected and their volatile suspended solids concentration was determined by gravimetric method.

[0073] The influent and effluent flow rates of each system are recorded synchronously daily, and 24-hour mixed water samples are collected to determine the influent and effluent chemical oxygen demand (COD) concentrations.

[0074] The apparent sludge yield coefficient for each system is calculated using the following formula: ; in, It is the apparent sludge yield coefficient; This is the daily volume of residual sludge discharged; It is the concentration of volatile suspended solids in the residual sludge sample; It is the inflow rate; It is the influent chemical oxygen demand concentration; It is the water flow rate; It refers to the chemical oxygen demand (COD) concentration in the effluent.

[0075] The daily sludge yield coefficient values ​​measured over 30 consecutive days were arithmetically averaged to obtain the average apparent sludge yield coefficient of each system during the stable operation phase, which served as the final indicator for evaluating its sludge reduction effect.

[0076] Experimental data (see Table 1): Table 1: Comparison of average apparent sludge yield coefficients for each reactor system in conclusion: The data in Table 1 show that the apparent sludge yield coefficients of Examples 1, 2, and 3 are significantly lower than those of all comparative examples, with Example 2 being the most significant. The lowest value was 0.128 kgVSS / kgCOD. This is compared to Comparative Example 1, which represents a conventional A2O process. Compared to (0.385), the sludge production in the embodiments of the present invention is significantly reduced. This proves the effectiveness of the technical solution proposed in the present invention in achieving in-situ sludge reduction.

[0077] By analyzing each item in the comparative examples, the function of each technical feature of the present invention can be further clarified. Comparative Example 4 ( Although the sludge yield of Example 1 was lower than that of Comparative Example 1, it was still significantly higher than that of Example 2. This indicates that simply adding the composite modified filler without applying a synergistic control strategy is insufficient to fully realize its sludge reduction potential, highlighting the necessity of a synergistic control strategy of ORP gradient and C / N ratio. (Comparative Example 2) Comparative Example 3 Comparative Example 5 and Comparative Example 4 show that the combined use of PAC and Fe3O4 results in a better sludge reduction effect than either single component, confirming a synergistic effect between the two functional components. The results are similar to those of Comparative Example 1, indicating that the synergistic regulation strategy must be applied to the specific composite modified filler of this invention to be effective, while having no significant effect on conventional biological fillers.

[0078] Therefore, the sludge reduction effect of this application stems from the organic combination of composite modified biological packing material and synergistic regulation strategy. This system enhances key metabolism through PAC-mediated electron shuttle, and at the same time utilizes the Fe(III) / Fe(II) redox cycle constructed by Fe3O4 to guide a portion of the energy used for microbial synthesis to ineffective energy consumption processes, thereby macroscopically manifesting as a significant reduction in the apparent yield coefficient of microorganisms.

[0079] Please see the appendix Figure 3 Test Example 2: Experimental objective: By comparing the chemical oxygen demand (COD) and ammonia nitrogen (NH4) of each embodiment with the comparative example, +The removal rates of total nitrogen (TN) and total phosphorus (TP) were measured to test the pollutant removal performance of each process.

[0080] Experimental steps: After the A2O reactor systems of Examples 1-3 and Comparative Examples 1-5 entered the stable operation phase, continuous monitoring was carried out for 30 days.

[0081] Collect 24-hour mixed water samples from the inlet and outlet of each system daily.

[0082] All water samples were filtered through a 0.45 μm filter membrane, and the pollutant concentrations were determined according to national standard methods. Chemical oxygen demand (COD) was determined using the dichromate method (GB 11914-89); ammonia nitrogen (NH4) was determined... + Total nitrogen (TN) was determined by Nessler's reagent spectrophotometry (GB 7479-87); total nitrogen (TN) was determined by alkaline potassium persulfate digestion ultraviolet spectrophotometry (GB 11894-89); and total phosphorus (TP) was determined by ammonium molybdate spectrophotometry (GB 11893-89).

[0083] Based on the pollutant concentrations in the influent and effluent of each system, the average removal rate of each pollutant is calculated using the following formula: ; in, This represents the average concentration of pollutants in the influent. This represents the average concentration of pollutants in the effluent.

[0084] The arithmetic mean of 30 days of monitoring data was used to obtain the stable removal performance of each system for different pollutants.

[0085] Experimental data (see Table 2): Table 2: Average removal rates of major pollutants for each reactor system in conclusion: The data in Table 2 show that Examples 1, 2, and 3 have effects on COD and NH4. + The removal rates of -N, TN, and TP were all higher than those of all comparative examples, demonstrating the superiority of the present invention in terms of comprehensive pollutant removal efficiency. This proves that the sludge reduction mechanism proposed in this invention does not come at the expense of effluent quality, but rather occurs synergistically with the efficient pollutant removal process.

[0086] By comparing with the comparative examples, the contribution of different technical features of the present invention to pollutant removal can be analyzed. The TN removal rate of Comparative Example 2 (containing only PAC) (78.9%) was significantly higher than that of Comparative Example 1 (68.3%), while the TP removal rate showed no significant change. This is consistent with the mechanism by which PAC acts as an electron shuttle to enhance denitrification in anoxic zones. Conversely, the TP removal rate of Comparative Example 3 (containing only Fe3O4) (88.2%) was better than that of Comparative Example 1, which may be attributed to the participation of iron ions in enhancing biological phosphorus removal or chemical precipitation processes. The TN and TP removal rates of Example 2 were both higher than those of Comparative Examples 2 and 3, demonstrating a synergistic effect between PAC and Fe3O4 components in enhancing nitrogen and phosphorus removal.

[0087] Although the removal rates of various pollutants in Comparative Example 4 (with packing material but without synergistic regulation) were better than those in Comparative Example 1, they were still lower than those in Example 2. This indicates that the synergistic regulation strategy of ORP gradient and C / N ratio is not only the core of achieving sludge reduction, but also optimizes the system's operating environment, ensuring and improving the stability and efficiency of nitrogen and phosphorus removal. The indicators of Comparative Example 5 (with synergistic regulation but without modified packing material) were basically the same as those in Comparative Example 1, further confirming that the synergistic regulation strategy is a specific operating method for the composite modified packing material of this invention, and the two must be combined to achieve the best technical effect.

[0088] In summary, the pollutant removal performance test confirms that, by combining composite modified biological packing material with a synergistic regulation strategy, this invention not only achieves the core objective of sludge reduction, but also enhances the denitrification and biological phosphorus removal processes of the system through the synergistic effect of PAC and Fe3O4, ultimately achieving a comprehensive pollutant removal performance superior to traditional processes.

[0089] Test Example 3: Experimental objective: To test the stability of each process by simulating organic shock loads and determining the time required for each system to recover to a steady state.

[0090] Experimental steps: After the A2O reactor systems of Examples 1-3 and Comparative Examples 1-5 had been running stably for 30 days, shock load experiments were conducted. Twenty-four hours before the experiment, the COD concentration of the effluent from each system was measured as a baseline value.

[0091] At the start of the experiment, by adjusting the ratio of raw water to influent, the COD concentration of the influent in all systems was increased from (450±20) mg / L to (810±20) mg / L within 2 hours, which means the load was increased by 80%.

[0092] Maintain this high concentration shock load continuously for 8 hours. After 8 hours, restore the influent COD concentration to the normal level of (450±20) mg / L.

[0093] Starting from the moment the impact load ends, water samples are collected from the outlets of each system every 2 hours to determine their COD concentration.

[0094] Record the time required for the COD concentration in the effluent of each system to recover to within 110% of the baseline value before the shock load. This time is defined as the system recovery time.

[0095] Experimental data (see Table 3): Table 3: Effluent COD Recovery Time for Each Reactor System under Shock Load in conclusion: The data in Table 3 show that, comparing Example 2 with the comparative example, the recovery time of Comparative Example 4 (with packing but no synergistic regulation) (19.5 h) was much longer than that of Example 2 (13.5 h). This indicates that the synergistic regulation strategy of the present invention plays a key role in system stability. When the load increases dramatically, the ORP gradient feedback regulation system can quickly adjust aeration and reflux, maintaining the redox potential of the core functional area within a suitable buffer range, thus avoiding drastic deterioration of the microbial metabolic environment.

[0096] The recovery time of Comparative Example 5 (with synergistic regulation but without modified packing material) (37.0 h) was close to that of Comparative Example 1 (38.5 h), demonstrating that the effectiveness of the synergistic regulation strategy is highly dependent on the presence of the composite modified biological packing material. This packing material not only provides basic load buffering capacity by enriching high concentrations of biomass, but its internal PAC and Fe3O4 components can also provide additional metabolic pathways for the rapid degradation of excess substrates by microorganisms during load shocks by accelerating electron transfer and providing alternative electron acceptors, thereby accelerating the system's recovery process.

[0097] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for in-situ sludge reduction using modified biological packing material to enhance the A2O process, characterized in that, Includes the following steps: S1. Construct an A2O process reactor consisting of an anaerobic tank, an anoxic tank, and an aerobic tank connected in series, set the volume ratio and total hydraulic retention time, and inoculate the anoxic tank and the aerobic tank with activated sludge to generate an initial liquid phase environment with basic biological treatment capabilities. S2. Add composite modified biological packing material to the generated initial liquid phase environment, and carry out biofilm acclimatization through continuous water intake operation. Cultivate a biofilm with catalytic activity on the surface of the composite modified biological packing material to form a solid-liquid composite reaction system for enhanced denitrification and pollution reduction. S3. Based on the solid-liquid composite reaction system, execute the preset process operating parameters, including internal and external reflux and dissolved oxygen concentration in the aerobic tank, so that the A2O process reactor enters the baseline steady-state operating state. S4. Under the aforementioned baseline steady-state operating conditions, a closed-loop feedback control is initiated. By monitoring the redox potential difference between the anoxic tank and the aerobic tank in real time and dynamically adjusting the aeration rate and internal reflux ratio, a redox potential gradient driving microbial metabolic intervention is constructed and maintained between the anoxic tank and the aerobic tank. S5. In coordination with closed-loop feedback control, feedforward control is initiated. By monitoring the influent carbon-nitrogen ratio in real time, when the influent carbon-nitrogen ratio is lower than the preset threshold, a temporary supply flow path is established by directly pumping raw water into the anoxic tank as a supplementary carbon source. S6. Under the coordinated control operation mode of closed-loop feedback control and feedforward control, the A2O process reactor is kept in a stable operating state with low sludge production rate in order to control the total amount of activated sludge and discharge the sludge generated after the corresponding reduction. The composite modified biological filler comprises powdered activated carbon and magnetite powder, wherein the mass ratio of the powdered activated carbon to the magnetite powder is 2.5-3.5:1; Step S4 further includes: The closed-loop feedback control uses a 10-minute calculation and adjustment cycle. The oxidation-reduction potential gradient is maintained within the target control range of 250-400mV by dynamically adjusting the aeration rate of the blower and the speed of the internal reflux pump in the aerobic tank through frequency conversion.

2. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 1, characterized in that, The preparation steps of the composite modified biological filler specifically include: The powdered activated carbon and magnetite powder are mixed and dispersed in water according to a ratio of 2.5-3.5 parts by weight, 1 part by weight, and 21-30 parts by weight of water to prepare a uniform suspension. Take 21-30 parts by weight of the porous carrier skeleton and immerse it completely in the prepared suspension for impregnation and loading treatment. The porous carrier skeleton that has undergone impregnation and loading treatment is dried to obtain the composite modified biological filler.

3. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 1, characterized in that, In step S1, the effective volume ratio of the anaerobic tank, the anoxic tank, and the aerobic tank is set to 1:1.5:3, and the total hydraulic retention time is controlled at 8-12 hours.

4. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 1, characterized in that, In step S2, the volume of the composite modified biological packing is 18-22% of the effective volume of the anoxic pool, and the acclimatization period of the biofilm is 25 days.

5. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 1, characterized in that, In step S3, the preset process operating parameters include: The internal reflux ratio is set to 200-250%; The external reflux ratio is set to 80%; The dissolved oxygen concentration in the aerobic tank is controlled at 2.0-3.0 mg / L.

6. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 1, characterized in that, In step S5, the feedforward control is achieved through linkage control between the online water quality analyzer and the bypass metering pump, and the preset threshold for the influent carbon-nitrogen ratio is 4.8-5.

2.

7. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 6, characterized in that, When the carbon-nitrogen ratio of the influent is lower than the preset threshold, the bypass metering pump is automatically started to deliver 8-12% of the total influent flow rate of raw water to the front end of the anoxic tank for carbon source replenishment.

8. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 1, characterized in that, In step S6, controlling the total amount of activated sludge specifically involves: maintaining a horizontal level of suspended solids concentration in the mixed liquor at the end of the aerobic tank, and quantitatively discharging the remaining sludge.

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