Wastewater treatment method of enhanced pretreatment and modified two-stage ao denitrification process

Abstract

The application discloses a sewage treatment method of reinforced pretreatment and improved two-stage AO denitrification process, relates to the technical field of sewage treatment, and comprises the following steps: reinforced pretreatment, in which suspended solids and part of organic matter are removed from sewage through units such as a grid, a water collecting pool and a solid-liquid separator; improved two-stage AO denitrification, in which short-cut nitrification and denitrification and anaerobic ammonia oxidation are utilized to realize synergistic denitrification through an anaerobic reactor, a primary / secondary anoxic tank and a large reflux micro-aerobic aeration tank; and advanced treatment and disinfection, in which Fenton oxidation, phosphorus removal precipitation and disinfection are performed to guarantee that the effluent meets the standard. The process is high in denitrification efficiency, low in energy consumption, small in sludge production and stable in operation, is suitable for high-concentration organic sewage, realizes deep removal of pollutants through multi-unit cooperation and parameter optimization, and provides an effective scheme for sewage treatment.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a wastewater treatment method using an enhanced pretreatment and a modified two-stage AO denitrification process. Background Technology

[0002] With the acceleration of industrialization and urbanization, the treatment of high-concentration organic wastewater has become an important issue in the field of environmental protection. At the same time, the requirements for pollution indicators are becoming increasingly stringent, and in recent years, how to remove total nitrogen more efficiently and energy-savingly has received increasing attention.

[0003] Traditional wastewater treatment processes suffer from low efficiency, high energy consumption, high operating costs, large sludge production, and large land area requirements when treating this type of wastewater. In recent years, anaerobic ammonia oxidation and short-cut nitrification-denitrification technologies have attracted widespread attention due to their advantages such as high efficiency, energy saving, environmental friendliness, and low sludge production. However, these technologies still face some challenges in practical applications, such as insufficient pretreatment leading to reduced efficiency in subsequent processes, and suboptimal process combinations. Therefore, developing a highly efficient, energy-saving, and stable wastewater treatment process is of significant practical importance. Summary of the Invention

[0004] To address the technical problems existing in the background art, this invention proposes a wastewater treatment method based on enhanced pretreatment and an improved two-stage AO denitrification process.

[0005] The wastewater treatment method proposed in this invention, which combines enhanced pretreatment and a modified two-stage AO denitrification process, includes the following steps:

[0006] Wastewater passes sequentially through a bar screen, a collection tank, a solid-liquid separator, an equalization tank, a full-volume filtration device, reaction tank 1, reaction tank 2, a primary sedimentation tank, and a transfer tank.

[0007] The effluent from the transfer tank enters the anaerobic reactor, and then enters the modified two-stage AO denitrification process, which includes a primary anoxic tank, a primary large-recirculation micro-aerobic aeration tank, a secondary anoxic tank, a secondary large-recirculation micro-aerobic aeration tank, and an aerobic aeration tank. Finally, sludge is separated through a secondary sedimentation tank.

[0008] The effluent from the secondary sedimentation tank enters reaction tank 3, reaction tank 4, and Fenton advanced oxidation tank for further oxidation and decomposition of recalcitrant organic matter. It then enters reaction tank 5, reaction tank 6, and final sedimentation tank to remove phosphorus. Finally, it is treated in a disinfection tank before being discharged in compliance with standards.

[0009] Furthermore, the full-volume filtration device uses a screw press or plate and frame filter press to perform solid-liquid separation on the water in the equalization tank, removing most of the suspended solids and reducing the turbidity and pollutant concentration of the wastewater.

[0010] Furthermore, the dissolved oxygen concentration inside the primary and secondary large-recirculation micro-aeration tanks is controlled at 0.45–0.55 mg / L to achieve short-cut nitrification and denitrification.

[0011] Furthermore, the dissolved oxygen concentration in the primary and secondary anoxic tanks is controlled to be less than 0.15–0.25 mg / L, providing a suitable growth environment for anaerobic ammonia oxidizing bacteria and denitrifying bacteria, thereby achieving simultaneous denitrification through denitrification and anaerobic ammonia oxidation.

[0012] Furthermore, the internal recirculation ratio of the primary and secondary large-recirculation micro-aeration tanks is 1:50, and the water is recirculated back to the corresponding primary and secondary anoxic tanks at a recirculation rate of 3 to 5 times the influent volume. The internal large-recirculation is achieved through airlift to realize complete mixing in the tanks and enhance short-cut nitrification and denitrification.

[0013] Furthermore, in the Fenton advanced oxidation tank, the dosage of Fenton reagent is adjusted according to the concentration of recalcitrant organic matter in the wastewater. The Fenton reagent generates highly oxidizing hydroxyl radicals, which oxidize and decompose the recalcitrant organic matter.

[0014] Furthermore, the disinfection tank treatment uses chlorine, sodium hypochlorite, or ultraviolet disinfection to kill pathogens and viruses in the sewage, ensuring that the effluent meets the standards.

[0015] Furthermore, the sludge from the secondary sedimentation tank is returned to the primary anoxic tank and the secondary anoxic tank respectively to maintain the microbial biomass and denitrification process in the system, thereby enhancing the system's stability and shock resistance.

[0016] Furthermore, the anaerobic reactor is interconnected with the primary anoxic tank via pipelines, and the common tank walls of the primary anoxic tank, the secondary anoxic tank, and the large-return micro-aerobic aeration tank are connected through reserved holes.

[0017] Furthermore, the primary large-flow micro-aerobic aeration tank and the secondary large-flow micro-aerobic aeration tank are respectively connected to the primary anoxic tank and the secondary anoxic tank through return pipes.

[0018] The beneficial effects of this invention are:

[0019] 1. By synergistically combining short-cut nitrification and denitrification with anaerobic ammonia oxidation, dissolved oxygen is precisely controlled and large-scale recirculation is set up in the primary and secondary large-recirculation micro-aerobic aeration tanks, and short-cut nitrification and denitrification are achieved simultaneously, converting ammonia nitrogen into nitrite and partially denitrifying it into nitrogen gas; the anoxic tank creates an environment for anaerobic ammonia oxidizing bacteria and denitrifying bacteria, and the two remove nitrogen simultaneously, which greatly improves the total nitrogen removal rate and reduces nitrogen emissions;

[0020] 2. Short-cut nitrification and denitrification, as well as anaerobic ammonium oxidation, do not require large amounts of oxygen or external carbon sources. Micro-aeration reduces aeration energy consumption, and the absence of additional carbon sources also reduces operating costs. Energy saving is achieved from both aeration and carbon source input, alleviating the energy consumption pressure of wastewater treatment.

[0021] 3. Compared with traditional nitrification and denitrification, short-cut nitrification and denitrification and anaerobic ammonium oxidation have lower carbon source requirements and produce less sludge; the anaerobic reactor stage removes a large amount of organic matter, further reducing sludge generation and lowering sludge disposal costs and environmental burden.

[0022] 4. The improved two-stage AO denitrification process, combined with sludge return and interconnection design of each tank, enhances the system's resistance to shocks and can still stably treat water when there are fluctuations in water quality and quantity, ensuring the quality of effluent. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention;

[0024] Figure 2 This is a block diagram of the turbidity control logic in the wastewater treatment system of the present invention;

[0025] Figure 3 This is a block diagram of the turbidity control logic for sludge return flow in the control system of this invention. Detailed Implementation

[0026] Example 1

[0027] Reference Figure 1 The wastewater treatment method proposed in this invention, which combines enhanced pretreatment and a modified two-stage AO denitrification process, is as follows:

[0028] I. Following the process flow diagram, construct the following components in sequence: bar screen, collection tank, solid-liquid separator (such as a screw press or plate and frame separator, selected according to project scale and sludge characteristics), equalization tank (equipped with a mechanical stirring device, power designed according to tank volume to ensure uniform adjustment of water quality and quantity), reaction tanks 1 and 2 (with reserved chemical reagent dosing ports, such as a coagulant dosing system, with metering pumps for precise dosing control), primary sedimentation tank (designed with a reasonable hydraulic retention time, generally 2-4 hours, to ensure sedimentation effect), transfer tank (installed with a micro-aeration device, using microporous aerators to control aeration volume for ammonia nitrogen stripping), and anaerobic reactor (constructing an anaerobic sludge bed, inoculated with anaerobic granular sludge, maintaining sludge concentration...). The system includes: a sludge removal tank (maintaining a concentration of 30-50 g / L), a modified two-stage AO denitrification unit (primary anoxic tank, primary large-flow micro-aeration tank, secondary anoxic tank, secondary large-flow micro-aeration tank, and aerobic aeration tank; the tank body is made of reinforced concrete with anti-corrosion and anti-seepage treatment on the inner wall), a secondary sedimentation tank (radial or vertical flow type, selected according to the treatment volume, with a sludge return system), a Fenton advanced oxidation tank (equipped with a Fenton reagent dosing system and stirring device, controlling the reaction pH at 3-4), a reaction phosphorus removal sedimentation tank (equipped with a phosphorus removal agent dosing device, such as a polyferric sulfate dosing system), and a disinfection tank (with reserved chlorine, sodium hypochlorite dosing interfaces or ultraviolet disinfection module installation positions).

[0029] II. Equipment debugging, details are as follows:

[0030] 1) Pretreatment Unit: Start the screen to test its effectiveness in intercepting large debris; fill the collection tank with water and adjust the liquid level control system to ensure stable water volume; run the solid-liquid separator under no-load test, then introduce sewage and adjust the sludge inlet pressure, screw shaft speed (screw press) or filter plate pressure (plate and frame filter press) to make the sludge cake moisture content lower than 80%; run the stirring device in the equalization tank to verify the water quality adjustment capability; add simulated agents (such as polyaluminum chloride) to reaction tanks 1 and 2, observe the coagulation and sedimentation effect, and optimize the agent dosage; test the sedimentation efficiency in the primary sedimentation tank and clean the sludge discharge pipe.

[0031] 2) Anaerobic reactor: After inoculating with anaerobic sludge, low-concentration wastewater (COD≤1000mg / L) is introduced from the collection tank, and the influent load is gradually increased (initial volumetric load 0.5-1.0kgCOD / (m³)). 3 •d) Monitor biogas production and composition (start-up is considered successful when methane content reaches 50% or more). By adjusting the influent flow rate and temperature (controlled at 30-35℃, mesophilic anaerobic), the COD removal rate is stabilized at 60% or more.

[0032] 3) Improved two-stage AO denitrification unit: Inoculate the anoxic tank and aeration tank with activated sludge (sludge concentration 3-5 g / L). First, test the return system with clean water (50 times return inside the primary and secondary large return micro-aeration tanks, and 3-5 times return externally to the anoxic tank) to verify the operation of pipelines and pump sets; introduce pretreated wastewater and control the dissolved oxygen in the primary and secondary large return micro-aeration tanks to about 0.5 mg / L (adjusted by frequency conversion of the aeration blower), and the dissolved oxygen in the anoxic tank to <0.2 mg / L (aeration is turned off, and the system is maintained by the return mixed liquor). Monitor the changes in ammonia nitrogen and nitrite nitrogen. When the efficiency of oxidizing ammonia nitrogen to nitrite nitrogen in the primary aeration tank reaches more than 70%, and the nitrite nitrogen supply in the secondary system is stable, the start-up is considered complete.

[0033] 4) Advanced Treatment and Disinfection Unit: Simulated wastewater is injected into the Fenton oxidation tank, and the dosage ratio of Fenton reagent (H2O2, FeSO4) is adjusted (generally H2O2:FeSO4). 2+ =10-20:1), the reaction process is controlled by online monitoring of ORP and pH; phosphorus removal agent is added to the reaction phosphorus removal sedimentation tank to determine the optimal dosage (targeting total phosphorus in the effluent <0.5mg / L); different disinfection methods are tested in the disinfection tank (e.g., sodium hypochlorite dosage 2-5mg / L, ultraviolet dose 10-30mJ / cm). 2 To verify the sterilization effect.

[0034] III. The process operation is as follows:

[0035] I. Enhanced Pretreatment Stage

[0036] The grating is a mechanical grating with a 5mm gap. It is cleaned regularly every day to remove pig hair, fecal clumps and other debris, ensuring smooth water flow.

[0037] Water collection tank: The volume is designed to be 1 / 5 of the daily water treatment capacity. It is equipped with a liquid level sensor and a booster pump to automatically adjust the water volume and ensure stable water intake for subsequent treatment units (flow fluctuation <10%).

[0038] Solid-liquid separator: A screw press solid-liquid separator is selected, with a sludge inlet pressure of 0.2-0.3MPa and a screw shaft speed of 2-4r / min. The sludge after separation has a moisture content of 75%-80% and is regularly transported to the sludge composting area; the wastewater after separation enters the equalization tank.

[0039] Equalization tank: effective volume 500m³ 3 Two 5kW mechanical agitators are installed, and the agitation is carried out once every 2 hours for 30 minutes each time to control the fluctuation coefficient of COD and ammonia nitrogen in the water quality within ±10%; the effluent from the equalization tank is sent to the full-volume filtration device by a booster pump.

[0040] Full-volume filtration (screw press): Screw press model suitable for water treatment capacity (50m³ / h) 3 / h), working pressure 0.1-0.2MPa, further remove suspended solids, so that the turbidity of the sewage is <50NTU, and the removal rates of COD and suspended solids are 20% and 60% or more, respectively. After filtration, the sewage enters reaction tanks 1 and 2.

[0041] Reactors 1 and 2: operated in series, with a total hydraulic retention time of 1.5 hours. Polyaluminum chloride is continuously added via metering pumps (dosage 200-300 mg / L), with a stirring intensity G = 30-50 s. -1 This causes colloidal particles and dissolved pollutants to aggregate, forming flocs with a particle size >100μm, which facilitates sedimentation.

[0042] Primary sedimentation tank: surface loading 0.8-1.2m 3 / (m 2 •h), hydraulic retention time 2.5 hours, suspended solids content after sedimentation <100mg / L, sludge is discharged regularly (sludge discharge cycle 8 hours, sludge discharge volume is controlled according to sludge interface instrument), and sludge is transported to the front end of the solid-liquid separator for co-processing.

[0043] Transfer pool: 200m³ 3 Install microporous aerators (aeration capacity 2-3m³ / h). 3 / (m 2 The process involves stripping away some free ammonia (ammonia nitrogen removal rate 10%-15%), while also acting as a buffer for water quality and quantity. The pH of the effluent from the transfer tank is maintained at 7.5-8.0 before entering the anaerobic reactor.

[0044] II. Improved Two-Stage AO Denitrification Process Stage

[0045] Anaerobic reactor: effective volume 1000m³ 3 Volumetric loading rate: 3.0-4.0 kg COD / (m³) 3 •d), temperature controlled at 32-35℃ (maintained by heating rods or waste heat utilization), hydraulic retention time 12 hours, inoculated with anaerobic granular sludge (sludge concentration 40g / L), after 3 months of operation, COD removal rate stabilized at 70%-80%, biogas production 0.3-0.4m³ / L. 3 / kgCOD removal improves the carbon-nitrogen ratio of wastewater (C / N increases from 3-5 to 5-7), and the effluent enters the primary anoxic tank.

[0046] Level 1 anoxic tank: effective volume 300m³ 3 Hydraulic retention time 4 hours, dissolved oxygen <0.2 mg / L, install a low-speed agitator (agitation intensity G = 5-10 s). -1The system utilizes denitrifying bacteria and anaerobic ammonia-oxidizing bacteria for nitrogen removal. It receives 3-5 times the influent volume of return liquid (20-30 mg / L nitrite nitrogen concentration) from the primary large-flow micro-aeration tank, with an influent ammonia nitrogen concentration of 200-300 mg / L. After the reaction, the ammonia nitrogen removal rate is 30%-40%, and nitrite nitrogen is partially removed. The effluent then enters the primary large-flow micro-aeration tank.

[0047] Primary large-flow micro-aeration tank: effective volume 400m³ 3 The hydraulic retention time is 5 hours, and the dissolved oxygen is controlled at 0.4-0.6 mg / L (adjusted by a microporous aerator and a variable frequency blower, with an aeration rate of 2-3 m³ / h). 3 / (m 2 •h)); Internally, airlift reflux (reflux rate is 50 times the influent flow rate) is adopted to achieve short-cut nitrification and denitrification, oxidizing ammonia nitrogen to nitrite nitrogen (nitrification rate >80%), and denitrifying some nitrite nitrogen into nitrogen gas (denitrification rate 30%-40%). At the same time, 3-5 times the effluent flow back to the primary anoxic tank; the sludge concentration in the tank is 4-6 g / L, and sludge is discharged regularly (sludge is discharged to the front end of the secondary anoxic tank to replenish the system sludge).

[0048] Secondary anoxic tank: effective volume 250m³ 3 With a hydraulic retention time of 3 hours and dissolved oxygen <0.2 mg / L, it functions as the same as the first-stage anoxic tank, further enhancing denitrification and anaerobic ammonia oxidation. It utilizes the return liquid (nitrite nitrogen concentration 15-25 mg / L) from the secondary large-flow micro-aeration tank, with influent ammonia nitrogen at 80-120 mg / L and an ammonia nitrogen removal rate of 40%-50%. The effluent enters the secondary large-flow micro-aeration tank.

[0049] Secondary large-flow micro-aeration tank: effective volume 350m³ 3 The hydraulic retention time is 4.5 hours, dissolved oxygen is 0.4-0.6 mg / L, and the internal airlift reflux is 50 times the influent volume to continue short-cut nitrification and denitrification, ensuring a stable supply of nitrite nitrogen (nitrification rate > 70%). 3-5 times the effluent is returned to the secondary anoxic tank; the sludge concentration is 3-5 g / L, working in conjunction with the primary system to ensure denitrification efficiency, and the effluent enters the aerobic aeration tank.

[0050] Aerobic aeration tank: effective volume 500m³ 3 The hydraulic retention time is 6 hours, dissolved oxygen is 2-4 mg / L (controlled by aeration), aerobic microorganisms decompose the remaining organic matter (COD removal rate > 80%, so that the effluent COD < 100 mg / L), sludge concentration is 5-7 g / L, sludge is discharged regularly (to the sludge treatment system), and the effluent enters the secondary sedimentation tank.

[0051] Secondary sedimentation tank: radial flow type, 15m in diameter, surface loading 0.6-0.8m. 3 / (m 2•h), hydraulic retention time 3 hours, sludge return ratio 50%-70% (returned to the primary and secondary anoxic tanks respectively, maintaining the sludge concentration in the anoxic tanks at 3-4 g / L), suspended solids after sedimentation <50 mg / L, effluent enters the deep treatment unit.

[0052] III. Deep Treatment and Disinfection Stage

[0053] Fenton advanced oxidation tank: effective volume 150m³ 3 The hydraulic retention time is 2 hours, and the pH is controlled at 3.5-4.0 by an automatic pH adjustment system. H2O2 (dosage 1000-1500 mg / L) and FeSO4 (dosage 50-100 mg / L) are added by metering pumps, and the stirring intensity G = 20-30 s. -1 The hydroxyl radicals are used to decompose recalcitrant organic matter (COD removal rate of 30%-40%, resulting in effluent COD < 60 mg / L). After the reaction, the pH is adjusted to 6.5-7.0 with alkaline solution before entering the reaction phosphorus removal sedimentation tank.

[0054] Reactive phosphorus removal sedimentation tank: effective volume 100m³ 3 The hydraulic retention time is 1.5 hours. Polyferric sulfate (dosage 50-100 mg / L) is added, stirred and mixed, and then allowed to settle. The total phosphorus removal rate is >90%, and the total phosphorus in the effluent is <5 mg / L. Sludge is discharged regularly (sludge is transported to the solid-liquid separation system), and the supernatant enters the disinfection tank.

[0055] Disinfection pool: Disinfected with sodium hypochlorite, effective volume 50m³ 3 The hydraulic retention time is 0.5 hours, the dosage is 3-5 mg / L, the residual chlorine is controlled at 0.5-1.0 mg / L, and pathogens and viruses are killed (E. coli removal rate >99%). The final effluent meets the discharge standards or is reused for greening, toilet flushing, etc. in aquaculture parks.

[0056] IV. The following table shows the data on chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total phosphorus (TP), and total nitrogen (TN) measured at different time periods in the collection tank, equalization tank, transfer tank, anaerobic effluent, secondary aerobic tank, secondary sedimentation tank, and clear water tank of a pig farm:

[0057]

[0058]

[0059]

[0060] Based on the water quality data shown in the table above, the following conclusions can be drawn:

[0061] A. Trends in Pollutant Removal

[0062] 1) Chemical Oxygen Demand (COD): The COD concentration in the collection tank was 10114-23475 mg / L. After enhanced pretreatment (grid-transfer tank), anaerobic reactor, two-stage AO and advanced treatment, the COD in the clear water tank was reduced to 106.3-194.8 mg / L, with an overall removal rate of over 90%. This demonstrates the process's highly efficient degradation capability for high-concentration organic matter. Furthermore, as operation continues, the removal effect tends to stabilize (the COD in the clear water tank fluctuates little in the later stages).

[0063] 2) Ammonia nitrogen (NH3-N): The ammonia nitrogen in the collection tank was 899.4-1814.4 mg / L. After passing through an anaerobic reactor and two-stage AO denitrification (first stage anoxic-microaerobic aeration synergy, second stage enhanced), the ammonia nitrogen in the clear water tank was reduced to 0.4-13.23 mg / L. The denitrification efficiency was significant. In particular, the synergistic effect of short-cut nitrification and denitrification and anaerobic ammonia oxidation greatly reduced the ammonia nitrogen after the aerobic tank, and further stabilized it in the secondary sedimentation tank and clear water tank.

[0064] 3) Total phosphorus (TP): In some tests, the TP in the collection tank was 1.45-17.15 mg / L. After Fenton advanced oxidation and phosphorus removal precipitation, the TP in the clear water tank was 0.7-30.7 mg / L (data was missing in the early stage, but it was stable and met the standard in the later stage). The advanced treatment process ensured phosphorus removal and met the discharge requirements.

[0065] 4) Total nitrogen (TN): The TN in the collection tank is 899.4-1934.4 mg / L. After anaerobic improvement of the carbon-nitrogen ratio and two-stage AO denitrification (denitrification in the anoxic tank + anaerobic ammonia oxidation, and short-cut nitrification in the microaerobic aeration tank), the TN in the clear water tank is 26-60 mg / L. Although there are fluctuations due to the influent, the overall high concentration of total nitrogen is effectively reduced, which reflects the advantages of the improved two-stage AO process for denitrification.

[0066] B. Process stability

[0067] On different testing dates, the water quality of each treatment unit (such as anaerobic effluent, secondary aerobic tank, and secondary sedimentation tank) fluctuated (affected by influent water quality and minor adjustments to operating parameters). However, the main indicators (COD, ammonia nitrogen, TN) in the clear water tank gradually converged with operation, indicating that after the process was adjusted, its adaptability to water quality fluctuations was enhanced. Through sludge return and parameter control (such as return ratio and aeration rate), a stable treatment effect can be maintained, and its shock resistance is gradually demonstrated.

[0068] Example 2

[0069] Please see Figure 2 Based on the above method, this embodiment proposes an online automated control system for process operation, specifically including:

[0070] Data acquisition module 1 (online turbidity meter 1): Data acquisition module 1 is installed inside the equalization tank to collect the turbidity of the sewage in real time, and the turbidity data is collected once every 6 hours;

[0071] Data processing and control module 1 (programmable logic controller 1): By setting the data processing and control module 1 to receive the sewage turbidity data transmitted by the data acquisition module 1, and based on the influent turbidity data, determine the next treatment process stage of the sewage. When the turbidity detection data is less than 1000 NTU, the sewage bypasses the full filtration system and directly enters the reaction tank 1.

[0072] Execution Module 1: Used to switch the electric valve of the outlet pipe of the equalization tank lift pump. That is, based on the data provided by the data acquisition module 1, the data processing and control module 1 determines whether the turbidity detection data in the equalization tank is less than 1000 NTU. If it is less than 1000 NTU, the electric valve will discharge the water in the equalization tank into the reaction tank 1. If it is greater than 1000 NTU, the electric valve will discharge the water in the equalization tank into the full-volume filtration system for filtration.

[0073] Please see Figure 3 An online automated control system for process operation further includes:

[0074] Data acquisition module 2 (online turbidity meter 2): Data acquisition module 2 is set up inside the primary anoxic tank and the secondary anoxic tank to detect the turbidity of the mixed liquor inside the tank in real time (turbidity has a linear relationship with the sludge concentration in the tank and can be used to represent the sludge concentration in the tank). Turbidity data is collected every 6 hours.

[0075] Data processing and control module 2 (programmable logic controller 2): By setting the data processing and control module 2 to receive turbidity data transmitted by the data acquisition module 2, and based on the average turbidity data of the primary anoxic tank and the secondary anoxic tank, the sludge return ratio of the secondary sedimentation tank is determined, and the sludge return ratio of the secondary sedimentation tank is controlled at 30%-100% (sludge return flow rate / equalization tank pump hourly flow rate).

[0076] Module 2: Used for adjusting the electric valve at the outlet of the sludge return pump. Normal sludge return is controlled at around 50%. When the turbidity concentration is less than 5000 NTU, the sludge return flow rate is increased. One control unit is used for every 10% sludge return ratio. The hourly flow rate of the equalization tank lift pump is 50 m³ / h. 3 / h, sludge return pump flow rate 25m³ / h 3 / h; for example, if the average measured turbidity data is 4000 NTU, then the control system adjusts the sludge return pump flow rate to 30 m³ / h. 3 / h. Adjustments will be made again based on the actual situation during the next turbidity data collection and testing.

[0077] 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.

Claims

1. A wastewater treatment method combining enhanced pretreatment and a modified two-stage AO denitrification process, characterized in that, Includes the following steps: Wastewater passes sequentially through a bar screen, a collection tank, a solid-liquid separator, an equalization tank, a full-volume filtration device, reaction tank 1, reaction tank 2, a primary sedimentation tank, and a transfer tank. The effluent from the transfer tank enters the anaerobic reactor, and then enters the modified two-stage AO denitrification process, which includes a primary anoxic tank, a primary large-recirculation micro-aerobic aeration tank, a secondary anoxic tank, a secondary large-recirculation micro-aerobic aeration tank, and an aerobic aeration tank. Finally, sludge is separated through a secondary sedimentation tank. The effluent from the secondary sedimentation tank enters reaction tank 3, reaction tank 4 and Fenton advanced oxidation tank for further oxidation and decomposition of recalcitrant organic matter. It then enters reaction tank 5, reaction tank 6 and final sedimentation tank to remove phosphorus. Finally, it is treated in a disinfection tank and discharged in compliance with standards. The full-volume filtration device uses a screw press or plate and frame machine to perform solid-liquid separation on the water in the equalization tank, removing most of the suspended solids and reducing the turbidity and pollutant concentration of the wastewater. The dissolved oxygen concentration inside the primary and secondary large-flow micro-aeration tanks is controlled at 0.45–0.55 mg / L to achieve short-cut nitrification and denitrification. The dissolved oxygen concentration in the primary and secondary anoxic tanks is controlled to be less than 0.2 mg / L, providing a suitable growth environment for anaerobic ammonia oxidizing bacteria and denitrifying bacteria, thereby achieving simultaneous denitrification through denitrification and anaerobic ammonia oxidation. The internal recirculation ratio of the primary and secondary large-flow micro-aeration tanks is 1:

50. At the same time, the water is recirculated back to the corresponding primary and secondary anoxic tanks at a recirculation rate of 3 to 5 times the influent. The internal large-flow recirculation is achieved through air lifting to achieve complete mixing in the tanks and enhance short-cut nitrification and denitrification.

2. The wastewater treatment method based on the enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that, In the Fenton advanced oxidation tank, the dosage of Fenton reagent is adjusted according to the concentration of recalcitrant organic matter in the wastewater. The Fenton reagent generates highly oxidizing hydroxyl radicals, which oxidize and decompose the recalcitrant organic matter.

3. The wastewater treatment method based on the enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that, The disinfection tank uses chlorine, sodium hypochlorite, or ultraviolet light to kill pathogens and viruses in the wastewater, ensuring that the effluent meets the standards.

4. The wastewater treatment method based on the enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that, The sludge from the secondary sedimentation tank is returned to the primary anoxic tank and the secondary anoxic tank respectively to maintain the microbial biomass and denitrification process in the system, and to enhance the system's stability and shock resistance.

5. The wastewater treatment method based on the enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that, The anaerobic reactor is connected to the primary anoxic tank via pipelines, and the common tank walls of the primary anoxic tank, secondary anoxic tank, and large-recirculation micro-aerobic aeration tank are connected through reserved holes.

6. The wastewater treatment method based on the enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that, The primary and secondary large-flow micro-aerobic aeration tanks are connected to the primary and secondary anoxic tanks respectively via return pipes.

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