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

Abstract

The invention relates to the technical field of sewage treatment, and discloses a method for realizing sludge in-situ reduction by using a modified biological filler reinforced A2O process, which comprises the following steps: building an A2O process reactor, inoculating activated sludge, and forming an initial liquid phase environment; adding a composite modified biological filler and domesticating a biological membrane to construct a solid-liquid composite system for enhancing nitrogen removal and pollution reduction; executing preset process parameters to enable the solid-liquid composite reaction system to enter reference steady-state operation; starting closed-loop feedback regulation and control, and monitoring and adjusting ORP gradient to intervene in microbial metabolism; starting feed-forward regulation, monitoring the carbon-nitrogen ratio of inlet water, and supplementing a carbon source with raw water when the carbon-nitrogen ratio is lower than a threshold value; under cooperative regulation and control, low-yield operation of the sludge is maintained, the total amount is controlled, and the reduced sludge is discharged; according to the invention, the oxidation-reduction potential gradient between the anoxic tank and the aerobic tank is maintained, and the effect of magnetite in the composite modified biological filler is combined, so that the metabolic path of microorganisms is induced to deviate towards endogenous respiration, and the energy utilization efficiency is optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the sewage treatment technical field, specifically to a method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process. BACKGROUND

[0002] A2O process, as a mature biological denitrification and phosphorus removal technology, has been widely used in the field of municipal sewage treatment. By setting up anaerobic, anoxic and aerobic functional zones, the process utilizes the synergistic metabolism of different microbial communities in activated sludge to effectively remove organic matter, nitrogen, phosphorus and other pollutants in water.

[0003] In the application of conventional A2O process, the system mainly relies on suspended growth of activated sludge. The core of its operation control is usually to maintain the dissolved oxygen (DO) in the aerobic tank at a relatively constant level to ensure the full performance of nitrification reaction. When treating low carbon-nitrogen ratio sewage, in order to ensure the efficiency of denitrification in the anoxic zone, it is common to add methanol, sodium acetate and other exogenous chemicals as supplemental carbon source. This operation mode constitutes the basic form of current A2O process application.

[0004] However, the existing A2O process control logic usually takes pollutant removal as the primary goal, ignoring the regulation of biological metabolism, resulting in a large amount of organic matter being used to synthesize new cells, causing a huge amount of excess sludge. The suspended sludge system is sensitive to hydraulic load fluctuations, prone to sludge bulking and loss, affecting the stability of operation. Therefore, the present application provides a method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process, to solve the problems existing in the prior art. SUMMARY

[0005] In view of the shortcomings of the prior art, the present application provides a method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process, which solves the problems of high sludge production, high operation cost and poor system stability of the existing A2O process.

[0006] To achieve the above purpose, the present application realizes the method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process through the following technical scheme: S1, an A2O process reactor composed of an anaerobic tank, an anoxic tank and an aerobic tank in series is built, the volume ratio and total hydraulic retention time are set, and activated sludge is inoculated into the anoxic tank and the aerobic tank to generate an initial liquid phase environment with basic biological treatment capacity; S2, composite modified biological filler is added to the generated initial liquid phase environment, and biological membrane domestication is carried out by continuous water feeding operation, biological membrane with catalytic activity is cultured on the surface of the composite modified biological filler to form a solid-liquid composite reaction system for strengthening denitrification and pollution reduction; S3, based on the solid-liquid composite reaction system, execute the preset process operation parameters, including internal and external reflux and dissolved oxygen concentration in the aerobic tank, so that the A2O process reactor enters the reference steady-state operation state; S4, under the reference steady-state operation state, start the closed-loop feedback control, by real-time monitoring the oxidation-reduction potential difference between the anoxic tank and the aerobic tank and dynamically adjusting the aeration amount and the internal reflux ratio, so as to build and maintain the oxidation-reduction potential gradient between the anoxic tank and the aerobic tank, which drives the metabolic intervention of microorganisms; S5, in cooperation with the closed-loop feedback control, start the feedforward control, by real-time monitoring the influent carbon-nitrogen ratio, when the influent carbon-nitrogen ratio is lower than the preset threshold, by pumping raw water directly into the temporary supply flow path of the anoxic tank as a supplemental carbon source; S6, under the cooperative control operation mode of closed-loop feedback control and feedforward control, the A2O process reactor maintains a stable operation state of low sludge yield to control the total amount of activated sludge, and discharges the sludge generated after the corresponding reduction.

[0007] The composite modified biological filler is composed of powdered activated carbon and magnetite powder loaded on a porous carrier skeleton: Powdered activated carbon (PAC): provides specific surface area and pore structure, provides attachment sites for microorganisms, promotes the formation of stable biofilms with high biomass, and has adsorption capacity for organic matter and resistance to impact load. At the same time, the adsorption properties of PAC itself help to enrich pollutants, creating favorable conditions for biodegradation.

[0008] Magnetite (Fe3O4): As a conductive mineral, magnetite can promote 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 of heterotrophic microorganisms and the denitrification rate during the denitrification process. In addition, magnetite induces or selectively enriches microorganisms with special metabolic functions, such as iron-reducing bacteria, whose metabolic processes help to break down sludge components such as extracellular polymeric substances (EPS). These synergies build a high-efficiency, stable solid-liquid composite reaction system.

[0009] By closed-loop feedback control of the oxidation-reduction potential difference (ΔORP) between the anoxic tank and the aerobic tank, precise control of the microenvironment of microorganisms is achieved: Nitrification-denitrification optimization: appropriate ΔORP gradient can accurately regulate the dissolved oxygen level in the aerobic zone and the low oxygen state in the anoxic zone, ensuring the optimal activity of nitrifying bacteria and denitrifying bacteria. The aerobic zone maintains sufficient oxygen to facilitate complete nitrification of ammonia nitrogen, while the anoxic zone controls the low ORP environment to utilize the nitrate nitrogen of internal reflux for denitrification, improving the total nitrogen removal rate.

[0010] Microbial metabolic regulation and sludge reduction: The maintained ORP gradient can induce the microorganisms to shift from the metabolic pathway mainly for growth and proliferation to the pathway more for maintaining energy and endogenous respiration. Under specific redox conditions, it is possible to promote microbial cell autolysis, predation of protozoa on bacteria, and succession of microbial community structure to low sludge yield, thereby reducing the microbial growth yield coefficient.

[0011] Real-time monitoring of influent C / N ratio by feedforward control system and automatic carbon source supplement when C / N is insufficient: Guaranteeing denitrification efficiency: Carbon source is the necessary electron donor for denitrification process, and insufficient C / N ratio will severely limit the activity of denitrifying bacteria, leading to accumulation of nitrate nitrogen and decrease of total nitrogen removal rate. Intelligent carbon source supplement ensures that there is sufficient electron donor in the anoxic zone at all times, maintaining efficient denitrification.

[0012] Optimizing microbial metabolism: Sufficient 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, part of the organic matter can be directly used for heterotrophic denitrification, rather than all being converted into new biomass, which helps to reduce the sludge yield coefficient and further promote sludge reduction.

[0013] The introduction of composite modified biological filler, the control of redox potential gradient, and the intelligent supplement of carbon source, through comprehensive intervention of microbial growth environment and metabolic pathway, establish the process conditions that drive low-yield operation of sludge, which can effectively reduce the net generation amount of residual sludge by regulating the growth, metabolism, and community structure of microorganisms, and ultimately realize in-situ reduction and total control of sludge.

[0014] Preferably, the composite modified biological filler comprises powdered activated carbon and magnetite powder, and 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: According to the ratio of 2.5-3.5 parts by mass of powdered activated carbon, 1 part by mass of magnetite powder, and 21-30 parts by mass of water, the powdered activated carbon and magnetite powder are mixed and dispersed in water to prepare a uniform suspension; Take 21-30 parts by mass of dry weight of the porous carrier skeleton and completely immerse it in the prepared suspension for impregnation loading treatment; Dry the porous carrier skeleton subjected to impregnation loading treatment 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 to be 8-12 hours.

[0017] Preferably, in step S2, the dosage volume of the composite modified biological filler is 18-22% of the effective volume of the anoxic tank, and the biological membrane domestication period is 25 days.

[0018] Preferably, in step S3, the preset process operation 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 to be 2.0-3.0 mg / L.

[0019] Preferably, the step of S4 further includes: the closed-loop feedback control takes 10 minutes as a calculation and adjustment period; the aeration amount of the blower of the aerobic tank and the rotating speed of the internal reflux pump are adjusted dynamically by frequency conversion to maintain the oxidation-reduction potential gradient in the target control interval of 250-400 mV.

[0020] Preferably, in step S5, the feedforward control is linked to control the bypass metering pump through an online water quality analyzer, and the preset threshold of the influent carbon-nitrogen ratio is 4.8-5.2.

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

[0022] Preferably, in step S6, the control of the total amount of activated sludge is specifically: according to the maintenance level of the mixed liquor suspended solids concentration at the end of the aerobic tank, the residual sludge is discharged quantitatively.

[0023] The present application provides a method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process. The present application has the following beneficial effects: 1、The present application constructs and maintains the oxidation-reduction potential gradient between the anoxic tank and the aerobic tank, and combines the electron shuttling and catalytic effect of magnetite in the composite modified biological filler, which together induces the metabolic pathway of microorganisms to deviate to endogenous respiration, optimizes the energy utilization efficiency, effectively inhibits the net proliferation rate of microorganisms, and reduces the yield of residual sludge, thereby reducing the subsequent cost and environmental load of sludge disposal.

[0024] 2、The present application enriches high concentration of functional microorganisms through the introduction of composite modified biological filler, forms a composite system coexisting with biofilm and activated sludge, enhances the resistance of the system to hydraulic and load shock, and strengthens the denitrification process by the promotion of extracellular electron transfer of magnetite, and combines with the protection of carbon and nitrogen ratio feedforward regulation to the carbon source of denitrification, so that the removal rates of chemical oxygen demand and total nitrogen can be maintained stable and efficient under the condition of fluctuation of influent water quality.

[0025] 3、The present application integrates closed-loop feedback based on ORP gradient and feedforward regulation system based on carbon-nitrogen ratio, realizes automation and refinement of process operation. The accurate control of ORP gradient enables the aeration quantity to be dynamically adjusted according to the actual metabolic demand of microorganisms, avoiding excessive aeration and energy consumption. At the same time, using raw water as a supplement carbon source replaces expensive additional chemicals, thereby reducing the comprehensive operation cost of the sewage treatment plant by saving power consumption and chemical consumption. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The method flow chart of the present application is shown in the figure; Figure 2 The sludge reduction schematic diagram of the present application is shown in the figure; Figure 3 The pollutant removal performance schematic diagram of the present application is shown in the figure. DETAILED DESCRIPTION

[0027] The sources and specifications of the main raw materials and reagents used in the following preparation examples, examples and comparative examples are as follows, and the reagents not specifically explained are commercially available analytical pure 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 Example 1-3.

[0035] Preparation Example 1: The raw materials were weighed according to the following mass fractions: powdered activated carbon (PAC) 2.5 parts, magnetite (Fe304) powder 1 part. The weighed two powders were added to 28-30 parts of deionized water, and a mechanical stirrer was started at room temperature to stir at a speed of 300 rpm for 30 minutes to prepare a uniform suspension.

[0036] 28-30 parts of dry polyurethane (PU) sponge filler were taken and completely immersed in the prepared suspension. The immersed filler was subjected to periodic extrusion and relaxation operation by a mechanical device at a frequency of 12 times / minute for 40 minutes to ensure that the particles in the suspension fully entered and adhered to the internal skeleton of the filler.

[0037] The filler subjected to the impregnation loading treatment was removed, and the excess liquid in the pores was removed by a rolling device. Subsequently, the filler was laid flat on a tray and moved into a forced air drying oven, dried at a constant temperature of 60°C for 14 hours until the filler reached a constant weight. After cooling to room temperature, the composite modified biological filler was obtained, denoted as S1.

[0038] Preparation Example 2: The raw materials were weighed according to the following mass fractions: powdered activated carbon (PAC) 3.0 parts, magnetite (Fe304) powder 1 part. The weighed two powders were added to 24-26 parts of deionized water, and a mechanical stirrer was started at room temperature to stir at a speed of 350 rpm for 30 minutes to prepare a uniform suspension.

[0039] 24-26 parts of dry polyurethane (PU) sponge filler were taken and completely immersed in the prepared suspension. The immersed filler was subjected to periodic extrusion and relaxation operation by a mechanical device at a frequency of 12 times / minute for 40 minutes to ensure that the particles in the suspension fully entered and adhered to the internal skeleton of the filler.

[0040] The filler subjected to the impregnation loading treatment was removed, and the excess liquid in the pores was removed by a rolling device. Subsequently, the filler was laid flat on a tray and moved into a forced air drying oven, dried at a constant temperature of 65°C for 12 hours until the filler reached a constant weight. After cooling to room temperature, the composite modified biological filler was obtained, denoted as S2.

[0041] Preparation Example 3: The raw materials are weighed according to the following quality parts: powdered activated carbon (PAC) 3.5 parts, magnetite (Fe3O4) powder 1 part. The two powders weighed above are added to 21-23 parts of deionized water, and a mechanical stirrer is started at room temperature to stir at a speed of 400 rpm for 25 minutes to prepare a uniform suspension.

[0042] Take 21-23 parts of dry polyurethane (PU) sponge filler and immerse it completely in the prepared suspension. The immersed filler is subjected to periodic compression and relaxation operations by a mechanical device at a frequency of 12 times per 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 filler subjected to the impregnation loading treatment is removed from the pores by a rolling device. Then, the filler is laid flat on a tray and moved into a forced air drying oven at a constant temperature of 70°C for 10 hours until the filler reaches a constant weight. After cooling to room temperature, the composite modified biological filler, denoted as S3, is obtained.

[0044] See the accompanying Figure 1 Examples 1-3.

[0045] Example 1: This example provides a method for realizing sludge in-situ reduction by using modified biological filler to strengthen the A2O process, which comprises the following steps: S1, an A2O process reactor composed of an anaerobic tank, an anoxic tank and an aerobic tank in series is built, and 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. The activated sludge from the secondary sedimentation tank of the municipal wastewater treatment plant is inoculated into the anoxic tank and the aerobic tank, so that the initial mixed liquor suspended solids concentration (MLSS) reaches 3500 mg / L.

[0046] S2, the composite modified biological filler S1 prepared in Preparation Example 1 is added to the anoxic tank, and the volume of the filler is 18% of the effective volume of the anoxic tank. The submersible mixer in the anoxic tank is started to make the filler in a uniform suspended and fluidized state. The biological membrane is domesticated with continuous water at a design load of 50%, and the domestication period is 25 days, until a uniform and dense biological membrane is formed on the surface of the filler, and the removal rates of COD and ammonia nitrogen of the system remain stable for a week.

[0047] S3, after the domestication of the biological membrane is completed, the system is adjusted to the normal operating condition. The internal reflux ratio is set to 200%, the external reflux ratio is set to 80%, and the dissolved oxygen (DO) concentration in the aerobic tank is controlled to be 2.0 mg / L.

[0048] S4, start the online ORP monitoring and PLC control system. Set the target control interval of the oxidation-reduction potential difference (ΔORP) between the anoxic tank and the aerobic tank to 250-300 mV. The PLC system takes 10 minutes as a calculation and adjustment period, and through frequency regulation of the aeration amount of the aerobic tank blower and the speed of the internal reflux pump, the ΔORP is maintained in the set target interval in real time.

[0049] S5, start the linkage control of the online water quality analyzer and the bypass metering pump, and set the C / N ratio threshold of the influent water quality to 4.8. When the online analyzer monitors that the influent C / N ratio is continuously lower than 4.8 for 30 minutes, the PLC automatically starts the bypass metering pump to pump the primary sedimentation tank effluent equivalent to 8% of the total influent flow directly into the front end of the anoxic tank for carbon source supplementation. When the C / N ratio recovers to above 4.8 and stabilizes for 30 minutes, the PLC automatically closes the bypass metering pump.

[0050] S6, the system discharges a certain amount of excess sludge according to the MLSS concentration at the end of the aerobic tank (maintained at 4000 mg / L) every day, and accurately records the discharge amount. At the same time, the influent and effluent water quality of the system is continuously monitored, and the apparent sludge yield coefficient and the pollutant removal rate are calculated.

[0051] Example 2: The embodiment provides a method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process, comprising the following steps: S1, build an A2O process reactor composed of an anaerobic tank, an anoxic tank and an aerobic tank in series, and the effective volume ratio of the three tanks is set to 1:1.5:3. The total hydraulic retention time (HRT) of the system is controlled to be 10 hours. The reflux activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant is inoculated into the anoxic tank and the aerobic tank, so that the initial mixed liquid suspended solid concentration (MLSS) reaches 3500 mg / L.

[0052] S2, the composite modified biological filler S2 prepared in Preparation Example 2 is added to the anoxic tank, and the addition volume is 20% of the effective volume of the anoxic tank. The submersible agitator in the anoxic tank is started to make the filler in a uniform suspended and fluidized state. The biological membrane is domesticated by continuously feeding water at 50% of the design load, and the domestication period is 25 days, until a uniform and dense biological membrane is formed on the surface of the filler, and the removal rates of COD and ammonia nitrogen of the system remain stable for one week.

[0053] S3, after the biological membrane domestication is completed, the system is adjusted to the normal operation condition. The internal reflux ratio is set to 200%, the external reflux ratio is set to 80%, and the dissolved oxygen (DO) concentration in the aerobic tank is controlled to be 2.5 mg / L.

[0054] S4, start online ORP monitoring and PLC control system. Set the target control interval of the oxidation-reduction potential difference (ΔORP) between the anoxic tank and the aerobic tank to 300-350 mV. The PLC system takes 10 minutes as a calculation and adjustment period, and through frequency regulation of the aeration amount of the aerobic tank blower and the speed of the internal reflux pump, the ΔORP is maintained in the set target interval in real time.

[0055] S5, start the linkage control of the online water quality analyzer and the bypass metering pump. Set the C / N ratio threshold of the influent water quality to 5.0. When the online analyzer monitors that the influent C / N ratio is continuously lower than 5.0 for 30 minutes, the PLC automatically starts the bypass metering pump to pump the primary sedimentation tank effluent equivalent to 10% of the total influent flow directly into the front end of the anoxic tank for carbon source supplementation. When the C / N ratio recovers to above 5.0 and stabilizes for 30 minutes, the PLC automatically closes the bypass metering pump.

[0056] S6, the system discharges a certain amount of excess sludge according to the MLSS concentration at the end of the aerobic tank (maintained at 4000 mg / L) every day, and accurately records the discharge amount. At the same time, the influent and effluent water quality of the system is continuously monitored, and the apparent sludge yield coefficient and the pollutant removal rate are calculated.

[0057] Example 3: The present embodiment provides a method for realizing sludge in-situ reduction by using modified biological filler to strengthen A2O process, comprising the following steps: S1, build an A2O process reactor composed of an anaerobic tank, an anoxic tank and an aerobic tank in series, and the effective volume ratio of the three tanks is set to 1:1.5:3. The total hydraulic retention time (HRT) of the system is controlled to be 10 hours. The reflux activated sludge from the secondary sedimentation tank of the municipal wastewater treatment plant is inoculated into the anoxic tank and the aerobic tank, so that the initial mixed liquid suspended solid concentration (MLSS) reaches 3500 mg / L.

[0058] S2, the composite modified biological filler S3 prepared in Preparation Example 3 is added to the anoxic tank, and the addition volume is 22% of the effective volume of the anoxic tank. Start the submersible mixer in the anoxic tank to make the filler in a uniform suspended and fluidized state. Continuously feed water at 50% of the design load to acclimate the biofilm, and the acclimation period is 25 days, until a uniform and dense biofilm is formed on the surface of the filler, and the removal rates of COD and ammonia nitrogen of the system remain stable for one week.

[0059] S3, after the biofilm acclimation is completed, the system is adjusted to the normal operating condition. The internal reflux ratio is set to 250%, the external reflux ratio is set to 80%, and the dissolved oxygen (DO) concentration in the aerobic tank is controlled to be 3.0 mg / L.

[0060] S4, start online ORP monitoring and PLC control system. Set the target control interval of the redox potential difference (ΔORP) between the anoxic tank and the aerobic tank to 350-400 mV. The PLC system takes 10 minutes as a calculation and adjustment period, and through frequency regulation of the aeration quantity of the aerobic tank blower and the speed of the internal reflux pump, the ΔORP is maintained in the set target interval in real time.

[0061] S5, start the linkage control of the online water quality analyzer and the bypass metering pump. Set the C / N ratio threshold of the influent water quality to 5.2. When the online analyzer monitors that the influent C / N ratio is continuously lower than 5.2 for 30 minutes, the PLC automatically starts the bypass metering pump to pump the primary sedimentation tank effluent equivalent to 12% of the total influent flow directly into the front end of the anoxic tank for carbon source supplement. When the C / N ratio recovers to above 5.2 and stabilizes for 30 minutes, the PLC automatically closes the bypass metering pump.

[0062] S6, the system discharges a certain amount of excess sludge according to the MLSS concentration at the end of the aerobic tank (maintained at 4000 mg / L) every day, and accurately records the discharge amount. At the same time, the influent and effluent water quality of the system is continuously monitored, and the apparent sludge yield coefficient and the pollutant removal rate are calculated.

[0063] Comparative Examples 1-5.

[0064] Comparative Example 1: Compared with Example 2, the difference is that the conventional A2O process is used in this comparative example, no biological filler is added in the reactor, and the ORP gradient feedback control and the influent C / N ratio feedforward control strategy are not performed, and the rest are the same.

[0065] Comparative Example 2: Compared with Example 2, the difference is that the modified biological filler used in this comparative example is only made by loading PAC on PU sponge (no Fe3O4 powder is added in the preparation process, and the rest of the preparation parameters are the same as those in Preparation Example 2), and the ORP gradient feedback control and the influent C / N ratio feedforward control strategy are not performed, and the rest are the same.

[0066] Comparative Example 3: Compared with Example 2, the difference is that the modified biological filler used in this comparative example is only made by loading Fe3O4 powder on PU sponge (no PAC is added in the preparation process, and the rest of the preparation parameters are the same as those in Preparation Example 2), and the ORP gradient feedback control and the influent C / N ratio feedforward control strategy are not performed, and the rest are 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 refers to the influent chemical oxygen demand (COD) 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 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.

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 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.

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, 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.

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 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.

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 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.

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 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.

7. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 1, characterized in that, 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.

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 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.

9. The method for in-situ sludge reduction using modified biological packing material to enhance the A2O process according to claim 8, 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.

10. 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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