A breeding wastewater grading anaerobic-aerobic biochemical treatment process

Abstract

The application discloses a kind of breeding wastewater grading anaerobic aerobic biochemical treatment processes, belong to the technical field of breeding wastewater treatment.The solid-liquid separation breeding wastewater after composite conditioning-functional filler contact, USR anaerobic fermentation, UASB anaerobic degradation, middle sedimentation pretreatment, two-stage A / O aerobic denitrification, final sedimentation separation, microalgae-biofilm biochemical treatment and disinfection standard treatment are discharged after discharge.The composite conditioning-functional filler contact tank is used to balance water quality, buffer load and adsorb suspended and colloidal pollutants;USR and UASB realize organic matter grading anaerobic degradation and biogas recovery;Two-stage A / O reactor strengthens nitrification and denitrification denitrification;Microalgae-biofilm biochemical tank further absorbs nitrogen and phosphorus and degrades residual organic matter.Each process is monitored and linked control by intelligent central control system in real time, which can improve the stability of breeding wastewater treatment, resource utilization rate and standard discharge reliability.

Description

Technical Field

[0001] This invention belongs to the field of aquaculture wastewater treatment, specifically relating to a graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater. Background Technology

[0002] Large-scale livestock and poultry farm wastewater, due to the mixture of dry manure cleaning and water-flushing processes, exhibits high concentrations of COD, BOD5, ammonia nitrogen, and SS, with significant fluctuations in water quality and quantity, making it a key area for water pollution control. Currently, the mainstream process is a combination of anaerobic and aerobic treatment. Improved solutions such as UASB+A / O, two-stage A / O, integrated equipment combining ammonia stripping tower + UASB + two-stage A / O, short-cut nitrification-anaerobic ammonia oxidation denitrification, and resource utilization combining solid-liquid separation + ultrafiltration + anaerobic + A / O have emerged. However, these technologies are all designed for a single manure cleaning process, and the load distribution in the two-stage anaerobic process is often unreasonable. When dealing with mixed wastewater, this can easily lead to excessively high shock loads in the aerobic stage, resulting in unstable treatment effects and insufficient process adaptability.

[0003] Existing technologies also have shortcomings in terms of intelligence and resource utilization. Intelligent control is often limited to simple adjustment of single parameters such as DO and pH. For example, the short-cut nitrification-anaerobic ammonia oxidation process only controls three parameters, failing to cover the entire process including anaerobic digestion, sludge treatment, and biogas recovery, and lacking the ability to predict water quality and handle shock loads. Regarding resource utilization, key parameters such as biogas production, hydrogen sulfide concentration, and sludge moisture content lack real-time intelligent control, leading to low biogas utilization efficiency, poor sludge dewatering, and waste of chemicals. Meanwhile, high-power equipment such as pumps and blowers mostly operate at fixed frequencies, without dynamic adjustment according to process load, resulting in high energy consumption and high failure rates due to reliance on manual maintenance.

[0004] Furthermore, existing automated controls are mostly local control modes, lacking remote monitoring and mobile operation capabilities, making operation and management difficult and unable to meet the needs of large-scale breeding bases for unmanned and intelligent operation. Therefore, developing a deep treatment process and system for aquaculture wastewater that is adapted to mixed manure removal technology, achieves full-process parameter linkage, is highly efficient in resource utilization, and has low energy consumption has become an urgent need for the industry's development. Summary of the Invention

[0005] The purpose of this invention is to provide a graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater, which solves the technical problems of existing anaerobic-aerobic combined processes for treating wastewater from mixed sources of dry manure cleaning and water-soaked manure, such as large shock loads of suspended and colloidal organic matter at the front end, unreasonable load distribution in the anaerobic stage, and unstable nitrogen and phosphorus removal in the subsequent stages.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater, which includes, in sequence, a composite conditioning-functional packing contact process, a USR anaerobic fermentation process, a UASB anaerobic degradation process, a mid-sedimentation pretreatment process, a two-stage A / O aerobic denitrification process, a final sedimentation separation process, a microalgae-biofilm biochemical treatment process, and a disinfection and standard attainment process. The aquaculture wastewater after solid-liquid separation first flows into a composite conditioning-functional filler contact tank. Functional filler is added to this tank; the filler is a biochar-zeolite framework formed by the anaerobic pyrolysis of pig manure residue, corn cob powder, and natural zeolite powder, and is obtained through in-situ deposition of magnesium and iron salts, as well as granulation with sodium alginate and polyvinyl alcohol. In the composite conditioning-functional filler contact tank, the aquaculture wastewater undergoes water quality equalization, load buffering, adsorption and partial hydrolysis of suspended and colloidal organic matter, and acidification. It then enters a USR biogas fermentation device and a UASB reactor for graded anaerobic degradation. Afterward, it passes through a mid-sedimentation tank to remove suspended solids and settling sludge. Subsequently, it enters a first-stage A / O reactor and a second-stage A / O reactor for organic matter degradation, nitrification / denitrification, and enhanced denitrification. The effluent from the final sedimentation tank further flows into a microalgae-biofilm biochemical tank with a microalgae cultivation zone and a biofilm carrier zone for nitrogen and phosphorus absorption, residual organic matter degradation, ammonia nitrification, and fine suspended solids retention. Finally, it is disinfected before discharge. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater is controlled by an intelligent central control system. The intelligent central control system is used to monitor water quality, water quantity, liquid level, sludge interface, dissolved oxygen, biogas production, hydrogen sulfide concentration and equipment status in real time, and to perform linkage regulation and fault early warning for lift pumps, return pumps, sludge pumps, blowers and disinfectant dosing devices based on the monitoring data.

[0007] Preferably, the composite conditioning-functional filler contact tank is provided with a mixing and conditioning zone and a functional filler contact zone. The filler dosage is 3-8 g / L, and the hydraulic retention time is 30-60 min. The preparation method of the functional filler includes the following steps: Q1: After drying pig manure biogas residue, mix it with corn cob powder and natural zeolite powder in a mass ratio of 40-70:10-30:10-30, pyrolyze it under anaerobic conditions at 500-650℃ for 1-3 hours, cool it, crush it and sieve it to obtain the basic skeleton. Q2: The basic framework is immersed in a mixed solution of MgCl2, FeCl3 and FeSO4, with a molar ratio of MgCl2, FeCl3 and FeSO4 of 1-4:2:1. The pH of the system is adjusted to 9-11, so that magnesium salt and iron salt are deposited in situ in the pores and surface of the basic framework to form a modified layer. Q3: Mix the basic skeleton containing the modified layer with sodium alginate and polyvinyl alcohol and granulate. The mass ratio of the basic skeleton containing the modified layer, sodium alginate and polyvinyl alcohol is 100:(2-6):(5-12) to obtain the functional filler.

[0008] Preferably, the USR anaerobic fermentation process uses a USR biogas fermentation device, and the intelligent central control system monitors the USR influent COD, BOD5, pH and liquid level in real time. When the USR influent COD or SS is higher than the set threshold, the intelligent central control system reduces the influent frequency of the booster pump and extends the actual residence time of the composite conditioning-functional packing contact tank to reduce the instantaneous impact load on the USR biogas fermentation device.

[0009] Preferably, in the UASB anaerobic degradation process, the intelligent central control system adjusts the volumetric load of the UASB reactor to 1.5-2.5 kg COD / m³·d and monitors the three-phase separator, sludge bed height, and gas production status in real time; when the sludge bed height exceeds the set upper limit, the intelligent central control system starts the sludge discharge pump for intermittent sludge discharge.

[0010] Preferably, the two-stage A / O aerobic denitrification process includes a first-stage A / O reactor and a second-stage A / O reactor. The first-stage A / O reactor controls the DO to be 2-4 mg / L and the sludge age to be 20-30 days. The second-stage A / O reactor serves as an enhanced denitrification stage. When the DO in the first-stage A / O reactor is below 2 mg / L or the ammonia nitrogen concentration is above the set threshold, the intelligent central control system increases the blower operating frequency. When the DO is above 4 mg / L, the blower operating frequency is reduced.

[0011] Preferably, in the microalgae-biofilm biochemical treatment process, the effluent from the final sedimentation tank enters the microalgae-biofilm biochemical tank, which is equipped with a microalgae cultivation zone and a biofilm carrier zone.

[0012] Preferably, the microalgae are one or more of Chlorella, Chlorella proteoglycans, and Scenedesmus obliquus, and the initial algal cell density after inoculation is 1.0 × 10⁻⁶. 6 -5.0×10 6 The microalgae-biofilm biochemical tank has a hydraulic retention time of 12-36 h, an operating temperature of 20-35 ℃, a pH of 6.8-8.5, a light intensity of 3000-8000 lx, and a light-dark cycle of 12 h:12 h.

[0013] Preferably, the biofilm carrier zone is equipped with polyethylene suspended packing or polyurethane sponge packing, with a carrier filling rate of 20-40%. The biofilm carrier zone is inoculated with activated sludge from two A / O reaction tanks, with an inoculated sludge concentration of 3-8 g / L (MLSS). The carrier is kept in a suspended or semi-suspended state by intermittent stirring or low-intensity aeration. The oxygen released by the microalgae and the low-intensity aeration together provide the oxygen source required for nitrification of the attached biofilm.

[0014] Preferably, in the disinfection process, the effluent from the microalgae-biofilm biochemical tank enters the disinfection tank, and the intelligent central control system automatically adjusts the chlorine dioxide dosage based on the influent flow rate, effluent COD, ammonia nitrogen, turbidity, and residual chlorine data. The chlorine dioxide dosage is 2-10 mg / L, the contact disinfection time is 30-60 min, and the COD, BOD5, SS, ammonia nitrogen, TN, and TP in the effluent after disinfection meet the discharge and reuse standards.

[0015] Preferably, the process also includes biogas recovery and sludge treatment steps; wherein, the biogas generated by the USR biogas fermentation unit and the UASB reactor is used for heating in the on-site boiler or power generation by the generator set after gas-liquid separation, desulfurization, pressure stabilization and gas storage, and the intelligent central control system monitors the biogas output, hydrogen sulfide concentration and gas storage pressure in real time; the residual sludge generated by each sedimentation and biochemical process enters the sludge thickening and dewatering system, and the intelligent central control system automatically adjusts the dosage of PAM, polyaluminum chloride or magnesium chloride according to the sludge moisture content.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention utilizes a composite conditioning-functional packing contact tank to achieve water quality equalization, load buffering, and adsorption of suspended and colloidal pollutants in aquaculture wastewater after solid-liquid separation. The biochar-zeolite framework in the functional packing provides a large specific surface area, which is beneficial for microbial attachment and pre-hydrolysis of organic matter; the magnesium-iron modified layer enhances phosphorus adsorption and slow release of ammonia nitrogen, improves initial water quality stability, reduces the load impact of subsequent anaerobic processes, increases the removal rates of COD, BOD5, and SS in the USR and UASB reactors, and reduces system fluctuations.

[0017] 2. The USR and UASB staged anaerobic process in this invention achieves the degradation of high-concentration organic matter and biogas recovery. USR provides primary fermentation to reduce BOD5 load, while UASB further removes COD and maintains stable biogas production. The two-stage A / O system enhances denitrification through nitrification-denitrification coupling, and precise control of DO and sludge age ensures high efficiency in the removal of ammonia nitrogen and total nitrogen. The intelligent central control system can adjust the influent flow, DO and blower frequency in real time, making the entire system operate stably and with low energy consumption.

[0018] 3. The microalgae-biofilm biochemical tank in this invention combines microalgae photosynthesis and biofilm adhesion degradation to further remove residual nitrogen and phosphorus, organic matter and fine suspended solids, achieving deep water purification. Microalgae release oxygen, partially replacing aeration energy consumption, while providing stable secondary oxidation conditions. The amount of chlorine dioxide added in the disinfection tank is automatically adjusted by the intelligent central control system, which can ensure that the effluent meets the discharge standards in a long-term stable manner, while avoiding the byproducts generated by excessive disinfection. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: This example discloses a method for preparing a functional filler, including the following steps: Q1: After drying pig manure biogas residue, mix it with corn cob powder and natural zeolite powder in a mass ratio of 60:20:20, and pyrolyze it at 600℃ under anaerobic conditions for 2 hours to obtain the basic skeleton. Q2: The basic framework is immersed in a mixed solution of MgCl2, FeCl3 and FeSO4 in a molar ratio of 2:2:1. The pH is adjusted to 10 so that magnesium salts and iron salts are deposited in situ in the pores and surface of the framework to form a modified layer. Q3: The basic skeleton containing the modified layer is mixed with sodium alginate and polyvinyl alcohol at a mass ratio of 100:4:8 and granulated to obtain the functional filler.

[0023] See Figure 1This embodiment discloses a graded anaerobic-aerobic biochemical treatment process for livestock wastewater. The process treats pig farm wastewater after solid-liquid separation. The influent COD is 6590-6600 mg / L, BOD5 is 3530-3540 mg / L, SS is 1500 mg / L, ammonia nitrogen is 276-278 mg / L, TN is 429-430 mg / L, TP is 41.0-41.5 mg / L, pH is 6.8-7.3, and the treatment flow rate is 25 m³ / L. 3 / h, the normal hydraulic retention time of the composite conditioning-functional packing contact tank is 40min, the COD threshold is set at 6600mg / L, and the SS threshold is set at 1500mg / L; Step 1: The solid-liquid separated aquaculture wastewater is sent to a composite conditioning-functional filler contact tank. The tank is set up with a mixing and conditioning zone and a functional filler contact zone in sequence. The dosage of functional filler is 5g / L and the hydraulic retention time is 40min. It is used to balance water quality, buffer organic load and adsorb suspended and colloidal pollutants. Step 2: The wastewater after compound conditioning treatment enters the USR biogas fermentation unit. The intelligent central control system monitors COD, BOD5, pH and liquid level in real time, and controls the inlet flow of the booster pump in conjunction with the system to ensure that the COD removal rate of the USR process is ≥70%, the BOD5 removal rate is ≥65%, and the SS removal rate is ≥70%. Step 3: The USR effluent enters the UASB reactor, with the volumetric loading rate controlled at 2.0 kg COD / m³·d. The three-phase separator, sludge bed height, and gas production status are monitored in real time to ensure that the COD removal rate of the UASB process is ≥70% and the BOD5 removal rate is ≥65%. Step 4: The UASB effluent flows by gravity into the intermediate settling tank. The intelligent central control system automatically controls the start and stop of the sludge discharge pump according to the sludge interface height, so that the SS removal rate is ≥50% and the ammonia nitrogen removal rate is ≥20%. Step 5: The effluent from the intermediate settling tank sequentially enters the first-stage A / O reactor and the second-stage A / O reactor. The DO in the first-stage A / O reactor is controlled at 3 mg / L, and the sludge age is controlled at 25 days. The second-stage A / O reactor serves as an enhanced denitrification stage. The system automatically adjusts the blower air volume based on dissolved oxygen data to ensure that the overall COD removal rate of the two A / O stages is ≥71%, the BOD5 removal rate is ≥85%, and the ammonia nitrogen removal rate is ≥92%. Step Six: The effluent from both A / O stages enters the final sedimentation tank for mud-water separation. The effluent from the final sedimentation tank then enters the microalgae-biofilm biochemical tank. The microalgae-biofilm biochemical tank includes a microalgae cultivation zone and a biofilm carrier zone. The microalgae cultivation zone is inoculated with a mixed algal solution of *Chlorella vulgaris* and *Scenedesmus obliquus* at a volume ratio of 1:1. The initial algal cell density after inoculation is 3.0 × 10⁻⁶ cells / day. 6The microalgae-biofilm biochemical tank has a hydraulic retention time of 24 h, an operating temperature of 25-30℃, a pH of 7.0-8.0, a light intensity of 5000 lx, and a light-dark cycle of 12 h:12 h. The biofilm carrier zone is equipped with polyethylene suspended packing material with a carrier filling rate of 30%, and is inoculated with activated sludge from the two-stage A / O reactor at a concentration of 5 g / L (MLSS). Intermittent stirring is used during operation, for 10 minutes per hour, to keep the carrier in a suspended or semi-suspended state. When the DO in the microalgae-biofilm biochemical tank is below 1 mg / L, low-intensity aeration is performed to maintain the DO at 1-3 mg / L. Microalgae absorb nitrogen and phosphorus and release oxygen, and the attached biofilm further degrades residual organic matter and nitrified ammonia nitrogen. Step 7: The effluent from the microalgae-biofilm biochemical tank enters the disinfection tank. The intelligent central control system automatically adjusts the chlorine dioxide dosage according to the influent flow rate, and the effluent meets the discharge standards after disinfection.

[0024] Example 2: This example discloses a method for preparing a functional filler, including the following steps: Q1: After drying pig manure biogas residue, mix it with corn cob powder and natural zeolite powder in a mass ratio of 70:15:15, and pyrolyze it at 650℃ under anaerobic conditions for 3 hours to obtain the basic skeleton. Q2: The basic framework is immersed in a mixed solution of MgCl2, FeCl3 and FeSO4 in a molar ratio of 4:2:1. The pH is adjusted to 11 so that magnesium salts and iron salts are deposited in situ in the pores and surface of the framework to form a modified layer. Q3: The basic skeleton containing the modified layer is mixed with sodium alginate and polyvinyl alcohol at a mass ratio of 100:6:12 and granulated to obtain the functional filler.

[0025] See Figure 1 This embodiment discloses a graded anaerobic-aerobic biochemical treatment process for livestock wastewater. The process treats pig farm wastewater after solid-liquid separation. The influent COD is 7260-7270 mg / L, BOD5 is 3990-4010 mg / L, SS is 1900 mg / L, ammonia nitrogen is 306-308 mg / L, TN is 479-481 mg / L, TP is 49.5-50.5 mg / L, pH is 6.8-7.3, and the treatment flow rate is 25 m³ / L. 3 / h, the normal hydraulic retention time of the composite conditioning-functional packing contact tank is 60min, the COD threshold is set at 7270mg / L, and the SS threshold is set at 1900mg / L; Step 1: The solid-liquid separated aquaculture wastewater is sent to a composite conditioning-functional filler contact tank. The tank is set up with a mixing and conditioning zone and a functional filler contact zone in sequence. The dosage of functional filler is 8g / L and the hydraulic retention time is 60min. It is used to balance water quality, buffer organic load and adsorb suspended and colloidal pollutants. Step 2: The wastewater after compound conditioning treatment enters the USR biogas fermentation unit. The intelligent central control system monitors COD, BOD5, pH and liquid level in real time, and controls the inlet flow of the booster pump in conjunction with the system to ensure that the COD removal rate of the USR process is ≥70%, the BOD5 removal rate is ≥65%, and the SS removal rate is ≥70%. Step 3: The USR effluent enters the UASB reactor, with the volumetric loading rate controlled at 2.5 kg COD / m³·d. The three-phase separator, sludge bed height, and gas production status are monitored in real time to ensure that the COD removal rate of the UASB process is ≥70% and the BOD5 removal rate is ≥65%. Step 4: The UASB effluent flows by gravity into the intermediate settling tank. The intelligent central control system automatically controls the start and stop of the sludge discharge pump according to the sludge interface height, so that the SS removal rate is ≥50% and the ammonia nitrogen removal rate is ≥20%. Step 5: The effluent from the intermediate settling tank sequentially enters the first-stage A / O reactor and the second-stage A / O reactor. The DO in the first-stage A / O reactor is controlled at 4 mg / L, and the sludge age is controlled at 30 days. The second-stage A / O reactor serves as an enhanced denitrification stage. The system automatically adjusts the blower air volume based on dissolved oxygen data to ensure that the overall COD removal rate of the two A / O stages is ≥71%, the BOD5 removal rate is ≥85%, and the ammonia nitrogen removal rate is ≥92%. Step Six: The effluent from both A / O stages enters the final settling tank for mud-water separation. The effluent from the final settling tank then enters the microalgae-biofilm biological treatment tank. The microalgae cultivation area is inoculated with a mixed algal solution formed by mixing Chlorella vulgaris and Scenedesmus obliquus at a volume ratio of 1:1. The initial algal cell density after inoculation is 5.0 × 10⁻⁶. 6 The microalgae-biofilm biochemical tank has a hydraulic retention time of 36 h, an operating temperature of 25-32℃, a pH of 7.0-8.5, a light intensity of 8000 lx, a light-dark cycle of 12 h:12 h, a polyethylene suspended packing material in the biofilm carrier zone with a carrier filling rate of 40%, an inoculated sludge concentration of 8 g / L (MLSS), and DO maintained at 1-3 mg / L through intermittent stirring and low-intensity aeration. Step 7: The effluent from the microalgae-biofilm biochemical tank enters the disinfection tank. The intelligent central control system automatically adjusts the chlorine dioxide dosage according to the influent flow rate, and the effluent meets the discharge standards after disinfection.

[0026] Example 3: This example discloses a method for preparing a functional filler, including the following steps: Q1: After drying pig manure biogas residue, mix it with corn cob powder and natural zeolite powder in a mass ratio of 40:30:30, and pyrolyze it at 500℃ under anaerobic conditions for 1 hour to obtain the basic framework. Q2: The basic framework is immersed in a mixed solution of MgCl2, FeCl3 and FeSO4 in a molar ratio of 1:2:1. The pH is adjusted to 9 so that magnesium salts and iron salts are deposited in situ in the framework channels and on the surface to form a modified layer. Q3: The basic skeleton containing the modified layer is mixed with sodium alginate and polyvinyl alcohol at a mass ratio of 100:2:5 and granulated to obtain the functional filler.

[0027] See Figure 1 This embodiment discloses a graded anaerobic-aerobic biochemical treatment process for livestock wastewater. The process treats pig farm wastewater after solid-liquid separation. The influent COD is 5550-5560 mg / L, BOD5 is 3160-3170 mg / L, SS is 1000 mg / L, ammonia nitrogen is 229-231 mg / L, TN is 362-364 mg / L, TP is 34.0-35.0 mg / L, pH is 6.8-7.3, and the treatment flow rate is 25 m³ / L. 3 / h, the normal hydraulic retention time of the composite conditioning-functional filler contact tank is 30min, the COD threshold is set at 5560mg / L, and the SS threshold is set at 1000mg / L; Step 1: The solid-liquid separated aquaculture wastewater is sent to a composite conditioning-functional filler contact tank. The tank is set up with a mixing and conditioning zone and a functional filler contact zone in sequence. The dosage of functional filler is 3g / L and the hydraulic retention time is 30min. It is used to balance water quality, buffer organic load and adsorb suspended and colloidal pollutants. Step 2: The wastewater after compound conditioning treatment enters the USR biogas fermentation unit. The intelligent central control system monitors COD, BOD5, pH and liquid level in real time, and controls the inlet flow of the booster pump in conjunction with the system to ensure that the COD removal rate of the USR process is ≥70%, the BOD5 removal rate is ≥65%, and the SS removal rate is ≥70%. Step 3: The USR effluent enters the UASB reactor, with the volumetric loading rate controlled at 1.5 kg COD / m³·d. The three-phase separator, sludge bed height, and gas production status are monitored in real time to ensure that the COD removal rate of the UASB process is ≥70% and the BOD5 removal rate is ≥65%. Step 4: The UASB effluent flows by gravity into the intermediate settling tank. The intelligent central control system automatically controls the start and stop of the sludge discharge pump according to the sludge interface height, so that the SS removal rate is ≥50% and the ammonia nitrogen removal rate is ≥20%. Step 5: The effluent from the intermediate settling tank sequentially enters the first-stage A / O reactor and the second-stage A / O reactor. The DO in the first-stage A / O reactor is controlled at 2 mg / L, and the sludge age is controlled at 20 days. The second-stage A / O reactor serves as an enhanced denitrification stage. The system automatically adjusts the blower air volume based on dissolved oxygen data to ensure that the overall COD removal rate of the two A / O stages is ≥71%, the BOD5 removal rate is ≥85%, and the ammonia nitrogen removal rate is ≥92%. Step Six: The effluent from both A / O stages enters the final settling tank for sludge-water separation. The effluent from the final settling tank then enters the microalgae-biofilm biological treatment tank. The microalgae cultivation zone is inoculated with a mixed algal solution formed by mixing Chlorella vulgaris and Scenedesmus obliquus at a volume ratio of 1:1. The initial algal cell density after inoculation is 1.0 × 10⁶ cells / mL. The hydraulic retention time in the microalgae-biofilm biological treatment tank is 12 h, the operating temperature is 20-28℃, the pH is controlled at 6.8-8.0, the light intensity is 3000 lx, and the light-dark cycle is 12 h:12 h. The biofilm carrier zone is equipped with polyurethane sponge packing material with a carrier filling rate of 20%. The inoculated sludge concentration is 3 g / L (MLSS). The carrier is kept in a suspended or semi-suspended state by intermittent stirring. When the DO is below 1 mg / L, low-intensity aeration is added. Step 7: The effluent from the microalgae-biofilm biochemical tank enters the disinfection tank. The intelligent central control system automatically adjusts the chlorine dioxide dosage according to the influent flow rate, and the effluent meets the discharge standards after disinfection.

[0028] Comparative Example 1: Compared with Example 1, Comparative Example 1 did not allow the aquaculture wastewater after solid-liquid separation to enter the composite conditioning-functional packing contact tank, but instead allowed it to directly enter the USR biogas fermentation device, while other conditions remained unchanged.

[0029] Comparative Example 2: Compared with Example 1, Comparative Example 2 retains the tank structure of the composite conditioning-functional filler contact tank, but no functional filler is added to the tank. Only hydraulic mixing and conditioning is performed, and the hydraulic retention time is 40 minutes. All other conditions remain unchanged.

[0030] Comparative Example 3: Compared with Example 1, the filler added to the composite conditioning-functional filler contact tank in Comparative Example 3 was prepared by mixing pig manure biogas residue, corn cob powder and natural zeolite powder in a mass ratio of 60:20:20 and then pyrolyzing it at 600℃ under anaerobic conditions for 2 hours. It was not modified by impregnation with MgCl2, FeCl3 and FeSO4, nor was a magnesium-iron modified layer formed. All other conditions remained unchanged.

[0031] Comparative Example 4: Compared with Example 1, the filler added to the composite conditioning-functional filler contact tank in Comparative Example 4 had its basic skeleton modified by MgCl2, FeCl3 and FeSO4. Instead of being mixed with sodium alginate and polyvinyl alcohol for granulation, it was directly added to the composite conditioning-functional filler contact tank in the form of powder or irregular particles. All other conditions remained unchanged.

[0032] Comparative Example 5: Compared with Example 1, in Comparative Example 5, the effluent from the composite conditioning-functional packing contact tank does not enter the USR biogas fermentation device, but directly enters the UASB reactor for anaerobic treatment, while other conditions remain unchanged.

[0033] Comparative Example 6: Compared with Example 1, Comparative Example 6 only had the effluent from the intermediate settling tank enter the first stage of the A / O reaction tank, without setting up a second stage of A / O enhanced denitrification; the DO in the first stage of the A / O reaction tank was controlled at 3 mg / L, the sludge age was controlled at 25 days, and other conditions remained unchanged.

[0034] Comparative Example 7: Compared with Example 1, Comparative Example 7 did not allow the effluent from the final sedimentation tank to enter the microalgae-biofilm biochemical tank, but instead allowed it to directly enter the disinfection tank for chlorine dioxide disinfection before discharge. All other conditions remained unchanged.

[0035] Performance testing: Each embodiment and comparative example was evaluated under the same treatment volume, the same detection method, and the same sampling period. Each system was started and operated continuously for 30 days before entering a stable operating period. During this stable operating period, sampling was conducted continuously for 7 days, with water samples collected daily at the disinfection tank outlet. Each water sample was measured in triplicate, and the average value was taken. Influent samples were taken from the influent of the aquaculture wastewater after solid-liquid separation, and effluent samples were taken from the disinfection tank outlet. The total removal rate was calculated using the following formula: Total removal rate = (Influent pollutant concentration - Effluent pollutant concentration) / Influent pollutant concentration × 100%. Discharge compliance was in accordance with GB 18596-2001, "Emission Standard of Pollutants for Livestock and Poultry Breeding Industry". Wastewater monitoring was conducted according to HJ 91.1-2019. Water quality sampling was conducted according to HJ 494-2009. COD was determined according to the dichromate method (HJ 828-2017), BOD5 according to the dilution and inoculation method (HJ 505-2009), and SS according to GB / T The following methods were used for determination: Gravimetric method (11901-1989); Ammonia nitrogen was determined by Nessler's reagent spectrophotometric method (HJ 535-2009); Total nitrogen was determined by alkaline potassium persulfate digestion ultraviolet spectrophotometric method (HJ 636-2012); Total phosphorus was determined by ammonium molybdate spectrophotometric method (GB 11893-1989); pH was determined by electrode method (HJ1147-2020); Biogas yield was calculated as the ratio of cumulative biogas production to cumulative COD removal of the USR biogas digester and UASB reactor during the stable operation period; Electricity consumption per ton of water was calculated as the ratio of total system power consumption to treated water volume during the stable operation period. The test results are shown in Table 1. Table 1 Table 2 As shown in Tables 1 and 2, after adopting the complete combined process of "composite conditioning-functional packing contact tank + USR + UASB + intermediate sedimentation + two-stage A / O + final sedimentation + microalgae-biofilm + disinfection" in Examples 1-3, the final effluent COD was 150-218 mg / L, BOD5 was 38-60 mg / L, SS was 36-55 mg / L, ammonia nitrogen was 8.5-13.5 mg / L, and TP was 1.0-1.5 mg / L. The overall water quality was significantly better than that of the comparative examples. Even though the influent SS of Example 2 was high and the operating load was large, the final effluent still maintained a low pollutant concentration, indicating that this application has good adaptability and shock resistance to high-load aquaculture wastewater.

[0036] Comparative Examples 1 and 2 show that the front-end composite conditioning-functional filler contact tank and the functional filler play a crucial role in system stability. Without this unit or without the addition of functional filler, COD, SS, ammonia nitrogen, TN, and TP all increased significantly, indicating that subsequent anaerobic-aerobic treatment alone is insufficient to adequately resist front-end water quality fluctuations. Comparative Example 3 shows that the magnesium-iron modified layer enhances phosphorus adsorption, ammonia nitrogen buffering, and microbial adhesion. Comparative Example 4 shows that granulation can reduce filler loss and clogging, improving contact efficiency and long-term stability. Comparative Example 5, after removing the USR, shows that the UASB directly experiences higher suspended solids and colloids. The organic load, COD, BOD5, and TN increased significantly, and the biogas yield also decreased from 0.42 m³·kg⁻¹ COD removal in Example 1 to 0.19 m³·kg⁻¹ COD removal, indicating that USR has a significant contribution to pre-hydrolysis acidification and biogas recovery. After eliminating the second-stage A / O in Comparative Example 6, the removal efficiency of ammonia nitrogen and TN decreased, indicating that the second-stage A / O is essential for enhancing nitrification and denitrification. After eliminating the microalgae-biofilm biochemical tank in Comparative Example 7, TN, TP, SS, and ammonia nitrogen were all higher than in Example 1, indicating that this deep purification unit can further ensure the stability of the final effluent.

[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0038] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater, characterized in that, The process includes, in sequence, a composite conditioning-functional filler contact process, a USR anaerobic fermentation process, a UASB anaerobic degradation process, a mid-sedimentation pretreatment process, a two-stage A / O aerobic denitrification process, a final sedimentation separation process, a microalgae-biofilm biochemical treatment process, and a disinfection and standardization process. The aquaculture wastewater after solid-liquid separation first flows into a composite conditioning-functional filler contact tank. Functional filler is added to this tank; the filler is a biochar-zeolite framework formed by the anaerobic pyrolysis of pig manure residue, corn cob powder, and natural zeolite powder, and is obtained through in-situ deposition of magnesium and iron salts, as well as granulation with sodium alginate and polyvinyl alcohol. In the composite conditioning-functional filler contact tank, the aquaculture wastewater undergoes water quality equalization, load buffering, adsorption and partial hydrolysis of suspended and colloidal organic matter, and acidification. It then enters a USR biogas fermentation device and a UASB reactor for graded anaerobic degradation. Afterward, it passes through a mid-sedimentation tank to remove suspended solids and settling sludge. Subsequently, it enters a first-stage A / O reactor and a second-stage A / O reactor for organic matter degradation, nitrification / denitrification, and enhanced denitrification. The effluent from the final sedimentation tank further flows into a microalgae-biofilm biochemical tank with a microalgae cultivation zone and a biofilm carrier zone for nitrogen and phosphorus absorption, residual organic matter degradation, ammonia nitrification, and fine suspended solids retention. Finally, it is disinfected before discharge. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater is controlled by an intelligent central control system. The intelligent central control system is used to monitor water quality, water quantity, liquid level, sludge interface, dissolved oxygen, biogas production, hydrogen sulfide concentration and equipment status in real time, and to perform linkage regulation and fault early warning for lift pumps, return pumps, sludge pumps, blowers and disinfectant dosing devices based on the monitoring data.

2. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater according to claim 1, characterized in that, The composite conditioning-functional filler contact tank is provided with a mixing and conditioning zone and a functional filler contact zone. The filler dosage is 3-8 g / L, and the hydraulic retention time is 30-60 min. The preparation method of the functional filler includes the following steps: Q1: After drying pig manure biogas residue, mix it with corn cob powder and natural zeolite powder in a mass ratio of 40-70:10-30:10-30, pyrolyze it under anaerobic conditions at 500-650℃ for 1-3 hours, cool it, crush it and sieve it to obtain the basic skeleton. Q2: The basic framework is immersed in a mixed solution of MgCl2, FeCl3 and FeSO4, with a molar ratio of MgCl2, FeCl3 and FeSO4 of 1-4:2:

1. The pH of the system is adjusted to 9-11, so that magnesium salt and iron salt are deposited in situ in the pores and surface of the basic framework to form a modified layer. Q3: The functional filler is obtained by mixing and granulating the basic skeleton containing the modified layer with sodium alginate and polyvinyl alcohol. The mass ratio of the basic skeleton containing the modified layer, sodium alginate and polyvinyl alcohol is 100:(2-6):(5-12).

3. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater according to claim 1, characterized in that, The USR anaerobic fermentation process uses a USR biogas fermentation device, and the intelligent central control system monitors the USR influent COD, BOD5, pH and liquid level in real time. When the COD or SS of the USR influent exceeds the set threshold, the intelligent central control system reduces the influent frequency of the booster pump and extends the actual residence time of the composite conditioning-functional packing contact tank to reduce the instantaneous shock load on the USR biogas fermentation unit.

4. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater according to claim 1, characterized in that, In the UASB anaerobic degradation process, the intelligent central control system adjusts the volumetric load of the UASB reactor to 1.5-2.5 kg COD / m³·d and monitors the three-phase separator, sludge bed height, and gas production status in real time. When the sludge bed height exceeds the set upper limit, the intelligent central control system starts the sludge discharge pump for intermittent sludge discharge.

5. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater according to claim 1, characterized in that, The two-stage A / O aerobic denitrification process includes a first-stage A / O reactor and a second-stage A / O reactor. The first-stage A / O reactor controls the DO to be 2-4 mg / L and the sludge age to be 20-30 days. The second-stage A / O reactor serves as an enhanced denitrification stage. When the DO in the first-stage A / O reactor is below 2 mg / L or the ammonia nitrogen concentration is above the set threshold, the intelligent central control system increases the blower operating frequency. When the DO is above 4 mg / L, the blower operating frequency is reduced.

6. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater according to claim 1, characterized in that, The microalgae are one or more of Chlorella, Chlorella proteoglycans, and Scenedesmus obliquus, and the initial algal cell density after inoculation is 1.0 × 10⁻⁶. 6 -5.0×10 6 The microalgae-biofilm biochemical tank has a hydraulic retention time of 12-36 h, an operating temperature of 20-35 ℃, a pH of 6.8-8.5, a light intensity of 3000-8000 lx, and a light-dark cycle of 12 h:12 h.

7. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater according to claim 1, characterized in that, The biofilm carrier zone is equipped with polyethylene suspended packing or polyurethane sponge packing, with a carrier filling rate of 20-40%. The biofilm carrier zone is inoculated with activated sludge from two A / O reaction tanks, with an inoculated sludge concentration of 3-8 g / L (MLSS). The carrier is kept in a suspended or semi-suspended state by intermittent stirring or low-intensity aeration. The oxygen released by the microalgae and the low-intensity aeration together provide the oxygen source required for nitrification of the attached biofilm.

8. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater according to claim 1, characterized in that, In the disinfection process, the effluent from the microalgae-biofilm biochemical tank enters the disinfection tank. The intelligent central control system automatically adjusts the chlorine dioxide dosage based on the influent flow rate, effluent COD, ammonia nitrogen, turbidity, and residual chlorine data. The chlorine dioxide dosage is 2-10 mg / L, and the contact disinfection time is 30-60 minutes. After disinfection, the COD, BOD5, SS, ammonia nitrogen, TN, and TP in the effluent meet the discharge and reuse standards.

9. The graded anaerobic-aerobic biochemical treatment process for aquaculture wastewater according to claim 1, characterized in that, The process also includes biogas recovery and sludge treatment steps; wherein, the biogas produced by the USR biogas fermentation unit and UASB reactor is used for heating in the on-site boiler or power generation by the generator set after gas-liquid separation, desulfurization, pressure stabilization and gas storage, and the intelligent central control system monitors the biogas output, hydrogen sulfide concentration and gas storage pressure in real time; the residual sludge produced by each sedimentation and biochemical process enters the sludge thickening and dewatering system, and the intelligent central control system automatically adjusts the dosage of PAM, polyaluminum chloride or magnesium chloride according to the sludge moisture content.

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