Sewage treatment method adopting enhanced pretreatment and improved two-stage AO denitrification process

Abstract

The invention discloses a sewage treatment method of an enhanced pretreatment and improved two-stage AO denitrification process, and relates to the technical field of sewage treatment.The method comprises the steps that enhanced pretreatment is conducted, specifically, sewage passes through a grating, a water collecting tank, a solid-liquid separator and other units, and suspended solids and part of organic matter are removed; improved two-stage AO nitrogen removal is carried out, and short-cut nitrification and denitrification and anaerobic ammonia oxidation are used for synergic nitrogen removal through an anaerobic reactor, a first-stage / second-stage anoxic tank, a large-reflux micro-aerobic aeration tank and the like; advanced treatment and disinfection are carried out, and the effluent is guaranteed to reach the standard through Fenton oxidation, phosphorus removal precipitation and disinfection. The process is efficient in nitrogen removal, energy-saving, consumption-reducing, low in sludge yield, stable in operation and suitable for high-concentration organic sewage, deep removal of pollutants is achieved through multi-unit cooperation and parameter optimization, and an effective scheme is provided for sewage treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a sewage treatment method using an enhanced pretreatment and an improved two-stage AO denitrification process. Background Art

[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 have become increasingly stringent. In recent years, how to remove total nitrogen more efficiently and energy-efficiently has received increasing attention.

[0003] Conventional wastewater treatment processes for this type of wastewater suffer from low treatment efficiency, high energy consumption, high operating costs, large sludge production, and extensive land use requirements. In recent years, anaerobic ammonium oxidation and short-cut nitrification and denitrification technologies have garnered widespread attention due to their high efficiency, energy efficiency, environmental friendliness, and low sludge production. However, these technologies still face challenges in practical application, such as insufficient pretreatment leading to reduced efficiency in subsequent processes and suboptimal process combinations. Therefore, the development of efficient, energy-saving, and stable wastewater treatment processes is of great practical significance. Summary of the Invention

[0004] In order to solve the technical problems existing in the background technology, the present invention proposes a sewage treatment method with enhanced pretreatment and an improved two-stage AO denitrification process.

[0005] The sewage treatment method of the enhanced pretreatment and improved two-stage AO denitrification process proposed in the present invention comprises the following steps:

[0006] The sewage passes through the screen machine, water collection tank, solid-liquid separator, regulating tank, full-volume filtration device, reaction tank 1, reaction tank 2, primary sedimentation tank and transfer tank in sequence;

[0007] The effluent from the transfer tank enters the anaerobic reactor and then enters the improved two-stage AO denitrification process, including the primary anoxic tank, the primary large reflow micro-aeration tank, the secondary anoxic tank, the secondary large reflow micro-aeration tank and the aerobic aeration tank, and finally passes through the secondary sedimentation tank for sludge separation;

[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 refractory organic matter, and then enters reaction tank 5, reaction tank 6 and final sedimentation tank to remove phosphorus, and finally is treated in the disinfection tank before being discharged in compliance with discharge standards.

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

[0010] Furthermore, the dissolved oxygen concentration in the first-stage large reflux micro-oxygen aeration tank and the second-stage large reflux micro-oxygen aeration tank is controlled at 0.45-0.55 mg / L, thereby achieving short-range nitrification and denitrification.

[0011] Furthermore, the dissolved oxygen concentration in the primary anoxic tank and the secondary anoxic tank is controlled at less than 0.15-0.25 mg / L, providing a suitable growth environment for anaerobic ammonium oxidizing bacteria and denitrifying bacteria, thereby achieving simultaneous denitrification by denitrification and anaerobic ammonium oxidation.

[0012] Furthermore, the internal reflux ratio of the first-level large reflux micro-aeration tank and the second-level large reflux micro-aeration tank is 1:50, and at the same time, a reflux rate of 3 to 5 times the water inlet volume is refluxed to the corresponding first-level anoxic tank and the second-level anoxic tank, and internal large reflux is performed through gas stripping to achieve complete mixing in the tank, thereby enhancing short-range nitrification, denitrification and denitrification.

[0013] Furthermore, in the Fenton advanced oxidation tank, the dosage of Fenton reagent is adjusted according to the concentration of refractory organic matter in the sewage, and the Fenton reagent generates highly oxidizing hydroxyl radicals to oxidatively decompose the refractory organic matter.

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

[0015] Furthermore, the sludge in the secondary sedimentation tank is returned to the primary anoxic tank and the secondary anoxic tank respectively, so as to maintain the microbial biomass and denitrification process in the system and enhance the stability and shock resistance of the system.

[0016] Furthermore, the anaerobic reactor is interconnected with the primary anoxic tank through a pipeline, and the primary anoxic tank, the secondary anoxic tank and the large reflux micro-aeration tank are connected to each other through a reserved hole on the common pool wall.

[0017] Furthermore, the first-level large reflux micro-aeration tank and the second-level large reflux micro-aeration tank are respectively connected to the first-level anoxic tank and the second-level anoxic tank through reflux pipes.

[0018] Beneficial effects of the present invention:

[0019] 1. Through the synergy of short-term nitrification and denitrification and anaerobic ammonium oxidation, the dissolved oxygen is precisely controlled and large reflux is set in the first and second large-scale reflux micro-aeration tanks to achieve short-term nitrification and denitrification simultaneously, converting ammonia nitrogen into nitrite and partially denitrifying it into nitrogen gas; the anoxic tank creates an environment for anaerobic ammonium oxidizing bacteria and denitrifying bacteria, and the two bacteria remove nitrogen simultaneously, significantly improving the total nitrogen removal rate and reducing nitrogen emissions;

[0020] 2. Short-term nitrification and denitrification, and anaerobic ammonium oxidation do not require a large amount of oxygen and an external carbon source. Micro-aerobic aeration reduces aeration energy consumption and does not require additional carbon sources, which also reduces operating costs. Energy conservation is achieved from both aeration and carbon source input, alleviating the energy consumption pressure of sewage treatment.

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

[0022] 4. The improved two-stage AO denitrification process, combined with sludge return and tank connection design, enhances the system's impact resistance. When dealing with fluctuations in water quality and water volume, it can still provide stable treatment and ensure the effluent effect. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0025] Figure 3 This is a logic block diagram of sludge return turbidity control in the control system of the present invention. DETAILED DESCRIPTION

[0026] Example 1

[0027] Reference Figure 1 The sewage treatment method of the enhanced pretreatment and improved two-stage AO denitrification process proposed in the present invention is as follows:

[0028] 1. According to the process flow chart, construct the screen, water collection tank, solid-liquid separator (such as spiral press or plate and frame machine, selected according to the project scale and sludge characteristics), regulating tank (equipped with mechanical stirring device, the power is designed according to the tank capacity to ensure uniform adjustment of water quality and water quantity), reaction tank 1 and 2 (reserved chemical agent addition port, such as coagulant addition system, metering pump accurately controls the addition amount), primary sedimentation tank (design reasonable hydraulic retention time, generally 2-4 hours, to ensure sedimentation effect), transfer tank (install micro-aeration device, use microporous aerator, control the aeration volume to achieve ammonia nitrogen stripping), anaerobic reactor (construct anaerobic sludge bed, inoculate anaerobic granular sludge, and maintain sludge concentration). Maintained at 30-50g / L), improved two-stage AO denitrification unit (first-stage anoxic tank, first-stage large-return micro-aerobic aeration tank, second-stage anoxic tank, second-stage large-return micro-aerobic aeration tank, aerobic aeration tank, the tank body adopts reinforced concrete structure, the inner wall is treated with anti-corrosion and anti-seepage treatment), secondary sedimentation tank (radial flow or vertical flow, selected according to the water treatment volume, and designed sludge return system), Fenton advanced oxidation tank (equipped with Fenton reagent dosing system and stirring device, and the reaction pH is controlled at 3-4), reactive phosphorus removal sedimentation tank (equipped with phosphorus removal agent dosing device, such as polyferric sulfate dosing system), disinfection tank (reserved chlorine, sodium hypochlorite dosing interface or ultraviolet disinfection module installation position);

[0029] 2. Equipment debugging, details are as follows:

[0030] 1) Pretreatment unit: Start the screen to test the effect of intercepting large debris; fill the water collection tank with water, debug the liquid level control system to ensure stable water volume; run the solid-liquid separator at no load, then introduce sewage, adjust the mud inlet pressure, screw shaft speed (screw stacker) or filter plate pressure (plate and frame machine) to make the mud cake moisture content lower than 80%; operate the stirring device in the regulating tank to verify the water quality regulation ability; add simulated reagents (such as polyaluminum chloride) to reaction tanks 1 and 2, observe the coagulation and sedimentation effect, and optimize the reagent dosage; test the sedimentation efficiency in the primary sedimentation tank and clean the mud discharge pipe.

[0031] 2) Anaerobic reactor: After inoculating anaerobic sludge, introduce low-concentration sewage (COD≤1000mg / L) from the water collection tank and gradually increase the water load (initial volume load 0.5-1.0kgCOD / (m 3 d) Monitor biogas production and composition (a methane content of 50% or more is considered a successful start-up) and stabilize the COD removal rate at above 60% by adjusting the inlet flow and temperature (controlled at 30-35°C, mesophilic anaerobic).

[0032] 3) Improved two-stage AO denitrification unit: inoculate activated sludge (sludge concentration 3-5g / L) into the anoxic tank and aeration tank, first debug the return system with clean water (50 times return inside the primary and secondary large return micro-aerobic aeration tanks, 3-5 times return outside to the anoxic tank), verify the operation of the pipeline and pump group; introduce pretreated sewage, control the dissolved oxygen in the primary and secondary large return micro-aerobic aeration tanks to about 0.5mg / L (through frequency conversion adjustment of the aeration fan), and the dissolved oxygen in the anoxic tank to <0.2mg / L (close aeration and maintain by returning the mixed liquid), monitor the changes in ammonia nitrogen and nitrite nitrogen, and when the efficiency of oxidation of ammonia nitrogen to nitrite nitrogen in the primary aeration tank reaches more than 70%, and the secondary system has a stable supply of nitrite nitrogen, the startup is considered complete.

[0033] 4) Deep treatment and disinfection unit: inject simulated sewage into the Fenton oxidation tank, adjust the Fenton reagent (H2O2, FeSO4) dosage ratio (generally H2O2:Fe 2+ =10-20:1), and the reaction process was controlled by online monitoring of ORP and pH; the phosphorus removal agent was added to the reaction dephosphorization sedimentation tank to determine the optimal dosage (with the goal of effluent total phosphorus <0.5mg / L); different disinfection methods were tested in the disinfection tank (such as sodium hypochlorite dosage of 2-5mg / L, ultraviolet dose of 10-30mJ / cm 2 ) to verify the sterilization effect.

[0034] 3. The process of operation is as follows:

[0035] I. Strengthening pretreatment stage

[0036] Grille: Use mechanical grille with a gap of 5mm. Clean the intercepted pig hair, feces lumps and other debris regularly every day to ensure smooth water flow.

[0037] Water collection tank: The volume is designed to be 1 / 5 of the daily water treatment volume. It is equipped with a liquid level sensor and a lifting pump to automatically adjust the water volume so that the subsequent treatment units can have stable water inflow (flow fluctuation <10%).

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

[0039] Regulating tank: effective volume 500m 3 , install two 5kW mechanical agitators, stir once every 2 hours, each time for 30 minutes, and control the COD and ammonia nitrogen fluctuation coefficients of water quality within ±10%; the effluent from the regulating tank is sent to the full-volume filtration device through a lifting pump.

[0040] Full filtration (snail stacking machine): Snail stacking machine model is suitable for processing water volume (processing capacity 50m 3 / h), working pressure 0.1-0.2MPa, further remove suspended solids, make sewage turbidity less than 50NTU, COD, suspended solids removal rate reaches 20% and 60% respectively, after filtration, sewage enters reaction tanks 1 and 2.

[0041] Reaction tanks 1 and 2: operated in series, with a total hydraulic retention time of 1.5 hours, continuous addition of polyaluminium chloride (dosage 200-300 mg / L) via a metering pump, stirring intensity G = 30-50s -1 , so that the colloidal particles and soluble pollutants coagulate to form flocs with a particle size of more than 100μm, which is convenient for precipitation.

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

[0043] Transfer pool: volume 200m 3 , install microporous aerator (aeration volume 2-3m 3 / (m 2 h)), blow off some free ammonia (ammonia nitrogen removal rate 10%-15%), and at the same time play a role in buffering 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

[0045] Anaerobic reactor: effective volume 1000m 3 , volume load 3.0-4.0kgCOD / (m 3 d) The temperature was controlled at 32-35°C (maintained by heating rods or waste heat utilization), the hydraulic retention time was 12 hours, and anaerobic granular sludge was inoculated (sludge concentration 40g / L). After 3 months of operation, the COD removal rate was stabilized at 70%-80%, and the biogas production was 0.3-0.4m 3 / kgCOD is removed, the carbon-nitrogen ratio of sewage is improved (C / N is increased from 3-5 to 5-7), and the effluent enters the primary anoxic tank.

[0046] Level 1 anoxic pool: effective volume 300m 3 , hydraulic retention time 4 hours, dissolved oxygen <0.2mg / L, install a low-speed stirrer (stirring intensity G = 5-10s -1), using denitrifying bacteria and anaerobic ammonia-oxidizing bacteria for denitrification; receiving 3-5 times the amount of reflux liquid from the first-stage large reflux micro-aeration tank (nitrite nitrogen concentration in the reflux liquid is 20-30 mg / L), the influent ammonia nitrogen is 200-300 mg / L, the ammonia nitrogen removal rate after reaction is 30%-40%, the nitrite nitrogen is partially removed, and the effluent enters the first-stage large reflux micro-aeration tank.

[0047] First-stage large reflux micro-oxygen aeration tank: effective volume 400m 3 , hydraulic retention time 5 hours, dissolved oxygen control 0.4-0.6mg / L (through microporous aerator and variable frequency fan adjustment, aeration volume 2-3m 3 / (m 2 h)); internally, air stripping reflux (reflux volume is 50 times the inlet water volume) is used to achieve short-range nitrification and denitrification, oxidizing ammonia nitrogen to nitrite nitrogen (nitrification rate >80%) and partially denitrifying nitrite nitrogen to nitrogen gas (denitrification rate 30%-40%). Simultaneously, 3-5 times the effluent volume flows back to the primary anoxic tank; the sludge concentration in the tank is 4-6g / L, and sludge is discharged regularly (discharged to the front end of the secondary anoxic tank to replenish system sludge).

[0048] Secondary anoxic pool: effective volume 250m 3 , hydraulic retention time is 3 hours, dissolved oxygen is <0.2mg / L, and the function is the same as that of the first-level anoxic tank, further strengthening denitrification and anaerobic ammonia oxidation, using the return liquid of the secondary large reflux micro-aeration aeration tank (nitrite nitrogen concentration 15-25mg / L), the influent ammonia nitrogen is 80-120mg / L, the ammonia nitrogen removal rate is 40%-50%, and the effluent enters the secondary large reflux micro-aeration tank.

[0049] Secondary large reflux micro-oxygen aeration tank: effective volume 350m 3 , hydraulic retention time 4.5 hours, dissolved oxygen 0.4-0.6 mg / L, internal reflux of 50 times the water inlet volume of the air stripping, continue short-term nitrification and denitrification, ensure a stable supply of nitrite nitrogen (nitritation rate > 70%), 3-5 times the effluent flows back to the secondary anoxic tank; sludge concentration 3-5g / L, coordinated with the first-level system to ensure denitrification efficiency, and the effluent enters the aerobic aeration tank.

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

[0051] Secondary sedimentation tank: radial flow type, diameter 15m, surface load 0.6-0.8m 3 / (m 2h), 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 tank at 3-4g / L), suspended solids after sedimentation <50mg / L, and the effluent enters the deep treatment unit.

[0052] III. Deep treatment and disinfection stage

[0053] Fenton advanced oxidation tank: effective volume 150m 3 , hydraulic retention time 2 hours, pH is controlled at 3.5-4.0 by pH automatic adjustment system, H2O2 (dosage 1000-1500 mg / L) and FeSO4 (dosage 50-100 mg / L) are added by metering pump, stirring intensity G = 20-30s -1 , using hydroxyl radicals to decompose difficult-to-degrade organic matter (COD removal rate 30%-40%, making the effluent COD <60mg / L), after the reaction, the pH is adjusted to 6.5-7.0 through alkaline solution and enters the reaction dephosphorization sedimentation tank.

[0054] Reactive phosphorus removal sedimentation tank: effective volume 100m 3 , hydraulic retention time 1.5 hours, add polyferric sulfate (dosage 50-100 mg / L), stir and mix and let it settle, total phosphorus removal rate > 90%, total phosphorus in effluent < 5 mg / L, discharge sludge regularly (sludge is transported to the solid-liquid separation system), and the supernatant enters the disinfection tank.

[0055] Disinfection pool: Sodium hypochlorite disinfection, effective volume 50m 3 , hydraulic retention time 0.5 hours, dosage 3-5mg / L, residual chlorine control 0.5-1.0mg / L, kill pathogens and viruses (E. coli removal rate > 99%), the final effluent meets the discharge standards or is reused for greening of the breeding park, flushing toilets, etc.

[0056] 4. At different times in a pig farm, the chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total phosphorus (TP) and total nitrogen (TN) data were tested in the water collection tank, regulating tank, transfer tank, anaerobic effluent, secondary aerobic tank, secondary sedimentation tank and clear water tank, as shown in the following table:

[0057]

[0058]

[0059]

[0060] The water quality data shown in the table above can be summarized as follows:

[0061] A. Pollutant removal trends

[0062] 1) Chemical oxygen demand (COD): The COD concentration in the water collection tank was between 10114-23475 mg / L. After enhanced pretreatment (grid-transfer tank), anaerobic reactor, two-stage AO and deep treatment, the COD in the clear water tank dropped to 106.3-194.8 mg / L, with an overall removal rate of over 90%, demonstrating the process's efficient degradation capability for high-concentration organic matter. Furthermore, as the operation continued, the removal effect tended to stabilize (COD fluctuations in the clear water tank were small in the later stages).

[0063] 2) Ammonia nitrogen (NH3-N): The ammonia nitrogen in the water collection tank is 899.4-1814.4 mg / L. After the anaerobic reactor and two-stage AO denitrification (first-stage anoxic-microaerobic aeration synergy, second-stage enhancement), the ammonia nitrogen in the clear water tank is reduced to 0.4-13.23 mg / L. The denitrification efficiency is significant, especially the synergistic effect of short-range nitrification and denitrification and anaerobic ammonia oxidation, which greatly reduces the ammonia nitrogen after the aerobic tank and further stabilizes it from the secondary sedimentation tank to the clear water tank.

[0064] 3) Total phosphorus (TP): In some tests, the TP in the water collection pool was 1.45-17.15 mg / L. After Fenton advanced oxidation and reactive phosphorus removal precipitation, the TP in the clear water pool was 0.7-30.7 mg / L (early data was missing, and the data was stable and met the standards in the later period). The deep treatment process ensured the removal of phosphorus and met the emission requirements.

[0065] 4) Total nitrogen (TN): 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 + anaerobic ammonia oxidation in the anoxic tank, and short-range nitrification in the micro-aerobic aeration tank), TN in the clear water tank is 26-60 mg / L. Although there are fluctuations due to water inflow fluctuations, the overall high-concentration total nitrogen is effectively reduced, reflecting the denitrification advantages of the improved two-stage AO process.

[0066] B. Process stability

[0067] On different test dates, although the water quality of each treatment unit (such as anaerobic effluent, secondary aerobic tank, and secondary sedimentation tank) fluctuated (affected by the influent water quality and fine-tuning of operating parameters), the main indicators of the clear water tank (COD, ammonia nitrogen, TN) gradually converged with operation, indicating that after debugging, the process has enhanced its adaptability to water quality fluctuations. Through sludge return and parameter control (such as return ratio and aeration volume), a stable treatment effect can be maintained, and the impact resistance is gradually reflected.

[0068] Example 2

[0069] See also Figure 2 Based on the above method, this embodiment proposes an online automatic control system for process operation, which specifically includes:

[0070] Data acquisition module 1 (online turbidity meter 1): Data acquisition module 1 is set inside the regulating tank to collect the turbidity of sewage in real time, and collect turbidity data 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, the next sewage treatment process section is determined based on the incoming water turbidity data. 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 water outlet pipe of the regulating tank lifting 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 regulating tank is less than 1000NTU. If it is less than 1000NTU, the electric valve will discharge the water in the regulating tank into the reaction tank 1. If it is greater than 1000NTU, the electric valve will discharge the water in the regulating tank into the full-volume filtration system for filtration;

[0073] See also Figure 3 , a process operation online automatic control system, further comprising:

[0074] Data acquisition module 2 (online turbidity meter 2): Data acquisition module 2 is installed inside the primary anoxic tank and the secondary anoxic tank to detect the turbidity of the mixed liquid inside the tank in real time (the turbidity is linearly related to the sludge concentration in the tank and can refer to 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 the turbidity data transmitted by the data acquisition module 2, the sludge return ratio of the secondary sedimentation tank is determined according to the average value of the turbidity data of the primary anoxic tank and the secondary anoxic tank. The sludge return ratio of the secondary sedimentation tank is controlled at 30%-100% (sludge return flow / regulating tank water pump hourly flow);

[0076] Execution module 2: used for adjusting the electric valve at the outlet of the sludge return pump, that is, the normal sludge return is controlled at about 50%. When the turbidity data concentration is less than 5000NTU, the sludge return volume is increased, and the 10% sludge return ratio is 1 control unit. The hourly flow rate of the regulating tank lift pump is 50m 3 / h, the sludge return pump flow rate is 25m 3 / h; For example, if the average value of the measured turbidity data is 4000NTU, the control system adjusts the sludge return pump flow rate to 30m 3 / h. The next time turbidity data is collected, adjustments will be made based on the actual situation.

[0077] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A wastewater treatment method with enhanced pretreatment and an improved two-stage AO denitrification process, characterized in that: The following steps are involved: The sewage passes through the screen machine, water collection tank, solid-liquid separator, regulating tank, full-volume filtration device, reaction tank 1, reaction tank 2, primary sedimentation tank and transfer tank in sequence; The effluent from the transfer tank enters the anaerobic reactor and then enters the improved two-stage AO denitrification process, including the primary anoxic tank, the primary large reflow micro-aeration tank, the secondary anoxic tank, the secondary large reflow micro-aeration tank and the aerobic aeration tank, and finally passes through the secondary sedimentation tank for sludge separation; 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 refractory organic matter, and then enters reaction tank 5, reaction tank 6 and final sedimentation tank to remove phosphorus, and finally is treated in the disinfection tank before being discharged in compliance with discharge standards.

2. The sewage treatment method with enhanced pretreatment and improved two-stage AO denitrification process according to claim 1 is characterized in that: The full-volume filtration device uses a screw press or a plate-and-frame machine to perform solid-liquid separation on the water in the regulating tank, remove most of the suspended solids, and reduce the turbidity of the sewage and the concentration of pollutants.

3. The sewage treatment method with enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that: The dissolved oxygen concentration in the first-stage large reflux micro-oxygen aeration tank and the second-stage large reflux micro-oxygen aeration tank is controlled at 0.45-0.55 mg / L, thereby realizing short-range nitrification and denitrification.

4. The sewage treatment method with enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that: The dissolved oxygen concentration in the primary anoxic tank and the secondary anoxic tank is controlled to be less than 0.15-0.25 mg / L, providing a suitable growth environment for anaerobic ammonium oxidizing bacteria and denitrifying bacteria, thereby achieving simultaneous denitrification by denitrification and anaerobic ammonium oxidation.

5. The sewage treatment method with enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that: The internal reflux ratio of the first-level large reflux micro-aeration tank and the second-level large reflux micro-aeration tank is 1:50, and at the same time, a reflux rate of 3 to 5 times the water inlet volume is refluxed to the corresponding first-level anoxic tank and the second-level anoxic tank. The internal large reflux is performed by gas stripping to achieve complete mixing in the tank, thereby enhancing short-range nitrification, denitrification and denitrification.

6. The sewage treatment method with 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 refractory organic matter in the sewage. The Fenton reagent generates highly oxidizing hydroxyl radicals to oxidatively decompose the refractory organic matter.

7. The sewage treatment method with enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that: The disinfection pool uses chlorine, sodium hypochlorite or ultraviolet disinfection to kill pathogens and viruses in the sewage and ensure that the effluent meets the standards.

8. The sewage treatment method with enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that: The sludge in the secondary sedimentation tank is returned to the primary anoxic tank and the secondary anoxic tank respectively, so as to maintain the microbial biomass and denitrification process in the system and enhance the stability and shock resistance of the system.

9. The sewage treatment method with 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 through a pipeline, and the public pool wall of the primary anoxic tank, the secondary anoxic tank and the large reflux micro-aeration tank is connected through a reserved hole.

10. The sewage treatment method with enhanced pretreatment and improved two-stage AO denitrification process according to claim 1, characterized in that: The first-level large reflux micro-aeration tank and the second-level large reflux micro-aeration tank are respectively connected to the first-level anoxic tank and the second-level anoxic tank through reflux pipes.

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