A device and method for efficiently treating aquaculture wastewater by deep coupling of SND-AO process and sulfur autotrophic denitrification

Abstract

This invention discloses a device and method for the efficient treatment of aquaculture wastewater using a deep-coupled SND-AO process with sulfur autotrophic denitrification. The device provided by this invention is based on the microenvironment theory of simultaneous short-cut nitrification-denitrification and sulfur autotrophic denitrification technology. It achieves close mass exchange through a specific circulation reflux setting, and the segmented deep coupling design avoids the influence of the external environment on its stability. Furthermore, it reduces sulfate ions to generate hydrogen sulfide in the gas phase and sulfur in the liquid phase. 2‑ By enhancing sulfur autotrophic denitrification through recycling, the efficiency of pollutant removal is improved, sulfur waste is reduced, and the content of sulfate byproducts is lowered. This invention achieves efficient removal of nitrogen and organic pollutants from aquaculture wastewater, as well as the recycling of sulfur. It significantly improves the operational stability, treatment effect, and economy of the device, and is particularly suitable for the efficient treatment of aquaculture wastewater containing complex pollutants, achieving the goal of efficiently removing organic and nitrogen pollution from aquaculture wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology. More specifically, it relates to an apparatus and method for the efficient treatment of aquaculture wastewater using a deep coupling of SND-AO process with sulfur autotrophic denitrification. Background Technology

[0002] With the rapid advancement of agricultural modernization in my country, livestock and poultry farming is gradually shifting from small-scale, decentralized operations to intensive, large-scale operations. Traditional farms are increasingly relocating to cities and surrounding areas. While this has improved production efficiency, it has also brought serious environmental pollution problems. In particular, livestock wastewater, due to its complex water quality, high concentrations of ammonia nitrogen, total nitrogen, and organic matter, and large fluctuations in discharge volume, significantly increases the difficulty of treatment.

[0003] Because aquaculture wastewater contains not only high concentrations of organic pollutants and suspended solids, but is also rich in nutrients such as nitrogen and phosphorus, with high ammonia nitrogen content, denitrification is extremely difficult, making it more challenging than treating other domestic wastewater or dye wastewater. Existing research has explored ammonia stripping processes for treating aquaculture wastewater, but this method is unsuitable for large-scale treatment. Furthermore, the stripping process can lead to increases in wastewater pH and COD concentration, making it difficult to meet discharge standards. Therefore, current aquaculture wastewater treatment typically relies on an "A / O (anaerobic / aerobic) + advanced treatment" process. However, this process still has many limitations. For example, the anaerobic / anaerobic process consumes a large amount of organic matter, resulting in insufficient carbon source for subsequent denitrification, thus limiting nitrogen removal efficiency. Even with a two-stage A / O process, the nitrogen removal rate is only 70%-80%, making it difficult to meet stricter discharge standards. Advanced treatment units often employ heterotrophic denitrification filters, requiring additional carbon source additions, which not only increases treatment costs but may also cause secondary pollution.

[0004] To avoid the need for external carbon sources, existing research has incorporated sulfur autotrophic denitrification (SAD) technology. This method utilizes reduced sulfur sources to react in an anaerobic environment, reducing nitrates to nitrogen gas. In this process, sulfur oxidation and nitrogen reduction occur simultaneously, removing both sulfur ions and nitrates, achieving a waste-to-waste treatment effect. However, this method generates large amounts of sulfate byproducts, causing foul odors in the water. It also suffers from sulfur waste, fluctuations in system effluent pH, and unstable treatment performance. Existing research combines sulfur autotrophic denitrification with short-cut denitrification anaerobic ammonium oxidation (AMO) to simultaneously remove ammonia and nitrite nitrogen through AMO. This method requires external alkalinity supplementation to adjust pH and maintain the stability of the sulfur autotrophic reaction. In short-cut denitrification coupled with AMO, while primarily used for nitrogen removal, high organic matter content preferentially promotes the growth of heterotrophic denitrifying bacteria during short-cut denitrification, inhibiting the activity of anaerobic ammonium oxidizing bacteria, leading to low reaction efficiency and even system collapse. Using an internal circulation anaerobic reactor to treat aquaculture wastewater can achieve high organic matter removal rates, but the ammonia nitrogen concentration in the effluent may be higher than the influent. Therefore, sulfur autotrophic denitrification combined with anaerobic treatment technology typically cannot achieve high nitrogen removal rates. Since aquaculture wastewater treatment is a complex process, current wastewater treatment technologies often fall short of ideal nitrogen removal effects, and their treatment efficiency needs further improvement. Therefore, there is still a lack of devices and methods that can efficiently treat aquaculture wastewater. In order to improve the denitrification rate and overall treatment effect of aquaculture wastewater, maintain reaction stability, reduce pH fluctuations, and reduce the generation of by-products, more new devices and methods that can efficiently and stably treat aquaculture wastewater need to be developed, in order to achieve the goal of deep denitrification of aquaculture wastewater and energy saving and consumption reduction. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the low denitrification rate of existing aquaculture wastewater and the deficiencies of the devices and methods for treating aquaculture wastewater, and to provide a device and method for the efficient treatment of aquaculture wastewater by deep coupling of SND-AO process with sulfur autotrophic denitrification.

[0006] The purpose of this invention is to provide a device for the efficient treatment of aquaculture wastewater by deep coupling of SND-AO process with sulfur autotrophic denitrification.

[0007] Another object of the present invention is to provide the application of the above-described device.

[0008] Another objective of this invention is to provide a method for the efficient treatment of aquaculture wastewater by deep coupling of SND-AO process with sulfur autotrophic denitrification.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] A device and method for the efficient treatment of aquaculture wastewater using a deep coupling SND-AO process with sulfur autotrophic denitrification, comprising an aquaculture wastewater tank, an SND-AO system, a sulfur autotrophic denitrification-SAD reactor, an effluent tank, and an electrical control system connected in sequence; the SND-AO system includes three adjacently arranged tanks: an SND tank, an A tank, and an O tank; wherein the SND tank is equipped with an inlet I, a sludge discharge valve, an aeration blower, a stirrer I, an aeration disc I, an overflow port I, a sensor assembly I, and a return port I; the discharge... The mud valve and aeration disc I are located at the bottom of the SND tank. Aeration disc I is connected to the aeration blower. Wastewater enters tank A through overflow port I. Tank A is a closed tank, equipped with a stirrer II, overflow port II, air outlet I, return port II, return port III, sensor assembly II, and effluent outlet. Overflow port II is located on the side near tank O and opposite overflow port I. Air outlet I is located at the top of tank A and connected to the vortex blower. Return port II is connected to return port V of the sulfur autotrophic denitrification-SAD reactor. The effluent outlet is connected to the sulfur autotrophic denitrification-SAD reactor. The inlet II of the denitrification-SAD reactor is connected, and wastewater enters the O tank through the overflow port II. The O tank is equipped with a stirrer III, aeration disc II, return port IV, a suction pump, membrane module, level sensor, and sensor module III. Aeration disc II is located at the bottom of the O tank and connected to an aeration blower. The membrane module is sequentially connected to the suction pump and the effluent tank. The sulfur autotrophic denitrification-SAD reactor includes sulfur-containing biological packing material, an air distribution disc, inlet II, outlet II, return port V, positive and negative pressure protectors, and sensor module IV. A one-way valve; an air distribution plate and inlet II are located at the bottom of the sulfur autotrophic denitrification-SAD reactor, and a positive and negative pressure protector is located at the top of the sulfur autotrophic denitrification-SAD reactor. The air outlet II is connected to the vortex blower through a one-way valve; the return port IV of the O tank is connected in sequence to the return port I, return port II, and inlet II; the electrical automatic control system is electrically connected to the aquaculture wastewater tank, aeration blower, agitator I, agitator II, agitator III, sensor components I~IV, liquid level sensor, membrane module, and suction pump.

[0011] This invention utilizes the deep coupling of Simultaneous Short-Cut Nitrification and Denitrification (SND), Anaerobic Oxic (AO), and Sulfur Autotrophic Denitrification (SAD) to propose a highly efficient system for treating aquaculture wastewater. This system integrates four main areas: the SND tank, the anaerobic tank (A tank), the SAD tank, and the aerobic tank (O tank). Through specific circulation settings and precise aeration control of dissolved oxygen (DO), the system operates under optimal conditions. The zonal circulation allows for the synergistic treatment of nitrogen, sulfur, and organic pollutants without the need for additional carbon sources. This efficient and stable treatment of aquaculture wastewater achieves deep denitrification and efficient resource recycling. This invention's device enhances material flow through circulation, utilizing the mutual matching of production and demand in each region, which is beneficial to the stability of regional reactions and reduces the impact of external conditions (such as pH, electron donors, etc.) on the overall system, achieving highly efficient nitrogen removal. This invention's device can achieve self-circulation of SND-AO-SAD, and simultaneously complete internal circulation of OA / SND and OA / SAD-A. Specifically, after aquaculture wastewater is sent to the SND tank for reaction, it enters the A tank, and the hydrogen sulfide gas generated from the reduction reaction is transported to the SAD. This ensures sufficient electron donors in the sulfur autotrophic denitrification-SAD reactor while enhancing COD removal from the wastewater in the A tank and reducing the sulfate content in the effluent. Sulfur autotrophic denitrification utilizes sulfides in the biological feed module as electron donors, achieving highly efficient nitrogen removal without the need for an external carbon source by reducing nitrates in the system. Simultaneously, the sulfate ions generated in the SAD are recycled back to the A tank, where they are further reduced to generate hydrogen sulfide in the gas phase and sulfur in the liquid phase. 2-This invention employs sulfur autotrophic denitrification to enhance the system's removal and stability of organic matter, further improving the efficiency of sulfur autotrophic denitrification and achieving deep nitrogen removal. This material circulation design facilitates mutual promotion between the two reactors. The effluent ultimately exits through the membrane reactor in the O-tank. This invention achieves deep treatment of aquaculture wastewater without the need for an external carbon source. Compared to traditional processes, this invention significantly improves nitrogen removal efficiency and achieves alkalinity balance without requiring additional alkalinity. The system pH does not significantly decrease after operation, maintaining stable reaction conditions. The residence time is shorter than that of ordinary two-stage AO systems for aquaculture wastewater treatment, improving treatment efficiency. Simultaneously, the optimized system setup reduces operating energy consumption and floor space, offering economic and environmental advantages and driving wastewater treatment technology towards greater efficiency, environmental friendliness, and economy.

[0012] The technical principle of this invention's device is as follows: Aquaculture wastewater first enters the simultaneous short-cut nitrification-denitrification zone (SND tank). Within this zone, dissolved oxygen (DO < 0.3 mg / L) and oxidation-reduction potential (ORP -50 to +50 mV) are precisely controlled to create a suitable micro-aerobic environment, allowing nitrifying and denitrifying bacteria to coexist and achieving simultaneous short-cut nitrification-denitrification, effectively removing organic matter (COD), ammonia nitrogen, and total nitrogen (TN) from the aquaculture wastewater. The wastewater treated by SND overflows into the anaerobic tank (A tank). In the A tank, an anaerobic or anoxic environment is present, involving the conversion of ammonia nitrogen. Nitrates and nitrites in the wastewater are reduced to nitrogen gas by denitrifying bacteria in the anaerobic environment, further removing nitrogen from the wastewater. Simultaneously, the A tank provides a suitable reducing environment, which is conducive to the enrichment of sulfate-reducing bacteria, achieving the recycling of sulfur and reducing sulfate emissions. Furthermore, sulfate reduction also enhances COD removal. To ensure the smooth operation of this series of reactions, the oxidation-reduction potential (ORP) in tank A is controlled between -120 and -160 mV. An oxidizing environment is provided in tank O, which converts ammonia nitrogen into nitrate nitrogen. Nitrate nitrogen is the primary target for removal in the SAD, and tank O also has a certain removal effect on COD. The mixture from tanks A and O is pumped into the sulfur autotrophic denitrification zone (SAD) via circulation. In this zone, sulfur-containing biological carriers slowly release sulfides as electron donors while simultaneously enriching sulfur autotrophic bacteria, achieving deep denitrification. Simultaneously, hydrogen sulfide gas generated in tank A is transferred to the SAD to enhance the denitrification effect and ensure system stability; while SO4 produced in the SAD... 2- The effluent is recycled back to Tank A, where a reduction reaction produces hydrogen sulfide gas for use in SAD (sulfuric acid treatment). The wastewater from Tank A and after SAD treatment enters Tank O, where the membrane bioreactor (MBR) module is activated to further remove ammonia nitrogen and organic matter. Simultaneously, the MBR module performs efficient sludge-water separation to improve the effluent quality, and finally, the treated effluent is ready for use.

[0013] Furthermore, the aquaculture wastewater tank is equipped with a booster pump, a solenoid valve, and a flow meter connected in sequence, and is connected to the inlet of the SND tank.

[0014] Furthermore, sensor assembly I in the SND pool includes: a pH sensor, a DO sensor I, an ORP sensor I, an MLSS sensor, and an NH4 sensor. + -N sensor, NO2 - -N sensor I, NO3 - -N sensor I;

[0015] Sensor assembly II in pool A includes: H2S gas sensor I, ORP sensor II, DO sensor II, and S. 2- Sensor I;

[0016] The sensor assembly III in the O pool includes: DO sensor III, NO3. - -N sensor II.

[0017] Furthermore, the sensor assembly IV in the sulfur autotrophic denitrification-SAD reactor includes: H2S gas sensor II, NO2... - -N sensor II, NO3 - -N sensor III, S 2- Sensor II, SO4 2- sensor.

[0018] Furthermore, the electrical automatic control system includes a PLC control box and a computer connected in sequence.

[0019] Furthermore, sulfur-containing biological packing material is inoculated with sulfur-autotrophic denitrification functional bacteria, and commonly used bacteria in this field can be used.

[0020] This invention provides the application of the above-mentioned device in the treatment of aquaculture wastewater.

[0021] This invention provides a method for the efficient treatment of aquaculture wastewater using a deep coupling of SND-AO process with sulfur autotrophic denitrification, employing the aforementioned device to treat the aquaculture wastewater.

[0022] Furthermore, during operation, the device controls the DO content in the SND tank to be 0.3~0.5 mg / L, ORP to be -50~+50 mv, pH to be 6.5-8.5, and hydraulic retention time to be 3~4 days; controls the DO in the A tank to be less than 0.1 mg / L, ORP to be -120~-160 mv, and hydraulic retention time to be 1~2 days; the DO in the overflow wastewater entering the O tank is controlled between 2.0~3.0 mg / L, and the hydraulic retention time is 0.5~1 days; the mixed liquor from the O tank is pumped back to the SND tank and the A tank through the return port, with return ratios set to 300% and 100% respectively; the mixed liquor from the A tank and the O tank is pumped into the bottom water distribution space of the SAD reactor, with a hydraulic retention time set to 0.2~0.3 days, and the mixed liquor return ratio is controlled according to the S / N ratio of 1.3, and the device operates continuously for 24 hours.

[0023] Furthermore, the membrane module in the O pool operates at a flux of 12~15 LMH, with intermittent water extraction for 8~9 minutes and stopping for 1~2 minutes.

[0024] Preferably, the membrane module is equipped with automatic cleaning, with a cleaning cycle of 5-10 days and a cleaning time of 20-30 minutes; online cleaning is carried out using sodium hypochlorite at a concentration of 0.2 g / L, and the system stops operating during cleaning.

[0025] The present invention has the following beneficial effects:

[0026] (1) This invention breaks through the bottleneck of existing aquaculture wastewater treatment technology. By deeply coupling simultaneous short-cut nitrification-denitrification (SND) and sulfur autotrophic denitrification (SAD), it achieves multi-biological synergistic effects of carbon and sulfur sources and self-circulation of SND-AO-SAD, while also completing internal circulation of OA / SND and OA / SAD-A. Through circulation and reflux, it achieves close material exchange. The segmented deep coupling design avoids the risk of stability being affected by fluctuations in the external environment (such as pH, dissolved oxygen, and electron donor concentration). Under this design, the device of this invention achieves efficient removal of nitrogen, sulfur, and organic pollutants from aquaculture wastewater and recycling of sulfur, significantly improving the system's operational stability, treatment effect, and economy. It is especially suitable for the efficient treatment of complex pollutants in aquaculture wastewater.

[0027] (2) By coupling pool A with the SAD region, the hydrogen sulfide generated in pool A and S 2- Recycling sulfur into the SAD reactor reduces sulfur waste and avoids SO4 emissions. 2- This addresses the issue of accumulated pollution. Furthermore, aeration and flushing can prevent the SAD biological packing biofilm from aging, further improving the system's stability and efficiency.

[0028] (3) The device and method of the present invention can be used to perform deep denitrification of aquaculture wastewater. No additional carbon source needs to be added throughout the process, which effectively reduces the sludge production and wastewater treatment costs of the system. The precise micro-aeration control reduces the energy consumption of the system. The entire device has a compact structure, can treat aquaculture wastewater on a large scale, has low operating costs, and has a more efficient process economy, meeting the requirements of energy conservation and emission reduction. Attached Figure Description

[0029] Figure 1 This is a cross-sectional structural diagram of a device for the efficient treatment of aquaculture wastewater by deep coupling of SND-AO process with sulfur autotrophic denitrification.

[0030] Figure 2 This is a top view of the main body of the device in Embodiment 1.

[0031] Figure 3 This is a schematic diagram of the process for treating aquaculture wastewater using the device in Example 1.

[0032] The following components are marked in the diagram: Aquaculture wastewater tank-1, lift pump-1.1, solenoid valve-1.2, flow meter-1.3, SND tank-2, inlet I-2.1, sludge discharge valve-2.2, aeration blower-2.3, agitator I-2.4, aeration disc I-2.5, overflow port I-2.6, pH sensor-2.7, DO sensor I-2.8, ORP sensor I-2.9, MLSS sensor-2.10, NH4+. + -N sensor-2.11, NO2 - -N sensor I-2.12, NO3 - -N sensor I-2.13, reflux port I-2.14, A tank-3, stirrer II-3.1, overflow port II-3.2, gas outlet I-3.3, reflux port II-3.4, reflux port III-3.5, H2S gas sensor I-3.6, ORP sensor II-3.7, DO sensor II-3.8, S 2- Sensor I-3.9, Outlet-3.10, Vortex Blower-3.11, O2 Tank-4, Agitator III-4.1, Aeration Disc II-4.2, Return Port IV-4.3, Suction Pump-4.4, Membrane Module-4.5, Liquid Level Sensor-4.6, DO Sensor III-4.7, NO3 - -N Sensor II-4.8, Sulfur Autotrophic Denitrification (SAD) Reactor-5, Sulfur-Containing Biological Packing Material-5.1, Gas Distribution Plate-5.2, Inlet II-5.3, Outlet II-5.4, Return Port V-5.5, Positive and Negative Pressure Protector-5.6, H2S Gas Sensor II-5.7, NO2 - -N sensor II-5.8, NO3 - -N sensorⅢ-5.9, S 2- Sensor II-5.10, SO4 2-Sensors - 5.11, Check valves - 5.12, Water outlet tanks - 6, Electrical automatic control system - 7, PLC control box - 7.1, Computer - 7.2. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0034] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0035] Example 1

[0036] A device for the efficient treatment of aquaculture wastewater using a deep coupling of SND-AO process with sulfur autotrophic denitrification is shown in the schematic cross-sectional diagram below. Figure 1 As shown, it includes aquaculture wastewater tank 1, SND-AO system, sulfur autotrophic denitrification-SAD reactor 5, effluent tank 6, and electrical automatic control system 7, which are connected in sequence.

[0037] The SND-AO system comprises three adjacent tanks: SND tank 2, A tank 3, and O tank 4. SND tank 2 includes an inlet I 2.1, a sludge discharge valve 2.2, an aeration blower 2.3, a mixer I 2.4, an aeration disc I 2.5, an overflow outlet I 2.6, and a sensor assembly I (pH sensor 2.7, DO sensor I 2.8, ORP sensor I 2.9, MLSS sensor 2.10, NH4+ sensor). + -N sensor 2.11, NO2 - -N sensor I 2.12, NO3 - -N sensor Ⅰ 2.13), return port Ⅰ 2.14; sludge discharge valve 2.2 and aeration disc Ⅰ 2.5 are located at the bottom of SND tank 2. Aeration disc Ⅰ 2.5 is connected to aeration blower 2.3. Wastewater enters A tank 3 through overflow port Ⅰ 2.6.

[0038] Pool A3 is a closed pool. Pool A3 is equipped with a stirrer II 3.1, an overflow port II 3.2, a gas outlet I 3.3, a return port II 3.4, a return port III 3.5, and sensor assembly II (H2S gas sensor I 3.6, ORP sensor II 3.7, DO sensor II 3.8, S...). 2-Sensor I 3.9), outlet 3.10; overflow outlet II 3.2 is located on the side near O tank 4 and opposite to overflow outlet I 2.6; air outlet I 3.3 is located at the top of A tank 3 and connected to vortex blower 3.11; return outlet II 3.4 is connected to return outlet V 5.5 of sulfur autotrophic denitrification-SAD reactor 5; outlet 3.10 is connected to inlet II 5.3 of sulfur autotrophic denitrification-SAD reactor 5; wastewater enters O tank 4 through overflow outlet II 3.2.

[0039] The O-tank 4 is equipped with a stirrer III 4.1, an aeration disc II 4.2, a return port IV 4.3, a suction pump 4.4, a membrane module 4.5, a level sensor 4.6, and sensor assembly III (DO sensor III 4.7, NO3 sensor). - -N sensor II 4.8); Aeration disc II 4.2 is located at the bottom of O tank 4 and connected to aeration blower 2.3; membrane module 4.5 is connected in sequence to suction pump 4.4 and outlet tank 6.

[0040] The sulfur autotrophic denitrification-SAD reactor 5 is equipped with sulfur-containing biological packing material 5.1, an air distribution plate 5.2, inlet II 5.3, outlet II 5.4, reflux outlet V 5.5, positive and negative pressure protectors 5.6, and sensor assembly IV (H2S gas sensor II 5.7, NO2). - -N sensor II 5.8, NO3 - -N sensor Ⅲ 5.9, S 2- Sensor II 5.10, SO4 2- Sensor 5.11), check valve 5.12; air distribution plate 5.2 and water inlet II 5.3 are located at the bottom of the SAD reactor, positive and negative pressure protector 5.6 is located at the top of the SAD reactor, and air outlet II 5.4 is connected to vortex blower 3.11 through check valve 5.12.

[0041] The return port Ⅳ 4.3 of O pool 4 is connected in sequence to return port Ⅰ 2.14, return port Ⅱ 3.5, and inlet port Ⅱ 5.3; the aquaculture wastewater tank 1 is equipped with a lift pump 1.1, a solenoid valve 1.2, and a flow meter 1.3 connected in sequence to the inlet port 2.1 of SND pool 2.

[0042] The electrical control system 7 is equipped with a PLC control box 7.1 and a computer 7.2 connected in sequence. The electrical control system 7 is electrically connected to the aquaculture wastewater tank 1, the SND-AO system, and the sulfur autotrophic denitrification-SAD reactor 5; wherein, the electrical control system 7 is electrically connected to the aquaculture wastewater tank 1, the aeration blower 2.3, the agitator I 2.4, the agitator II 3.1, the agitator III 4.1, the sensor assembly I~IV, the liquid level sensor 4.6, the membrane assembly 4.5, and the suction pump 4.4.

[0043] A top view of the experimental setup is shown below. Figure 2 As shown, the device is arranged in concentric circles from the inside out, with the sulfur autotrophic denitrification-SAD reactor 5 as the center. The O tank 4, A tank 3, and SND tank 2 are set up. The internal circulation of SND requires a large reflux ratio. The circular design is conducive to the self-circulation of the SND area. The wastewater flows in the concentric circles with inertia and enters the next stage of reaction through overflow. This reasonable arrangement can save energy. Secondly, the wastewater flows in an arc shape in the concentric circles, which reduces the dead zone of the reaction, is conducive to the homogenization of the influent, and accelerates the reflux circulation. At the same time, it can be set according to actual needs.

[0044] During treatment, the wastewater in the aquaculture wastewater tank 1 is connected to the inlet I 2.1 of the SND tank 2 in the SND-AO system via a booster pump 1.1, a solenoid valve 1.2, and a flow meter 1.3. Under the action of the agitator I 2.4, the wastewater circulates. Air enters the SND tank 2 sequentially through the aeration blower 2.3 and the aeration disc I 2.5, where a low-oxygen aeration reaction is carried out to achieve simultaneous short-cut nitrification and denitrification. In this area, a suitable micro-aerobic environment is achieved by precisely controlling the dissolved oxygen (DO less than 0.3 mg / L) and oxidation-reduction potential (ORP of -50~+50mv), allowing nitrifying and denitrifying bacteria to coexist and achieving simultaneous short-cut nitrification and denitrification, effectively removing organic matter (COD), ammonia nitrogen, and total nitrogen (TN) from the aquaculture wastewater. The aquaculture wastewater treated in SND tank 2 enters tank A 3 through overflow outlet I 2.6 and is circulated under the action of stirrer II 3.1. Tank A provides a suitable sulfate reduction environment, enriching sulfate-reducing bacteria to achieve the recycling of sulfur and reduce sulfate emissions. To ensure the smooth progress of this series of reactions, the oxidation-reduction potential (ORP) in tank A is controlled between -120 and -160 mV. In tank A, nitrates and nitrites in the wastewater are reduced to nitrogen gas by denitrifying bacteria in an anaerobic environment, thereby further removing nitrogen from the wastewater. At the same time, the sulfur-generating gas H2S produced by the reaction is pumped into the bottom of the sulfur autotrophic denitrification-SAD reactor 5 through the top outlet I 3.3 under the action of vortex blower 3.11 and gas distribution plate 5.2, providing an electron donor for sulfur autotrophic denitrification. If the H2S produced in pool A is not completely absorbed by the SAD reactor, after detection by the sensor in the SAD reactor, the gas is returned to pool A through outlet II 5.4 via check valve 5.12 and under the action of vortex blower 3.11. It is necessary to ensure that its concentration does not exceed the discharge limit. When pool A is under negative pressure, the gas pressure in pool A can also be balanced through outlet II 5.4 of the SAD reactor.

[0045] The various sensors installed in the device transmit the collected signals to the PLC control box 7.1 of the electrical automatic control system 7, and then feed them back to the computer 7.2 to continuously monitor the pH range, DO, ORP, and NH4 during the reaction process online.+ -N, NO2 - -N, NO3 - -N, SO4 2- S 2- The mass concentration of H2S is controlled by setting a preset control index range and adjusting parameters in real time based on monitoring data, such as the mixed liquor reflux ratio and membrane suction start / stop, to control the simultaneous short-range nitrification-denitrification and sulfur autotrophic denitrification processes.

[0046] The wastewater after reaction in Tank A3 enters Tank O4 through overflow outlet II 3.2. Tank O4 provides an oxidation environment to convert ammonia nitrogen into nitrate nitrogen. Nitrate nitrogen can be the main target for removal in SAD. Tank O4 also has a certain removal effect on COD. The wastewater is then returned to Tank A and SND or SAD through the return outlet for circulation. Through ammonia oxidation and carbon oxidation reactions under aerobic conditions in Tank O4, ammonia nitrogen and organic matter are further removed. Meanwhile, a membrane bioreactor (MBR) module is installed in tank O 4. It is activated when the effluent is discharged after the final circulation treatment is completed, and performs efficient sludge-water separation. It can be used to retain microorganisms, improve the system MLSS, and improve the effluent quality. The operation of membrane module 4.5 is automatically controlled by liquid level sensor 4.6. When the liquid level is higher than the membrane module by 1.0m (which can be set according to actual needs), it starts to run. After the reaction, the treated water is transported to the effluent tank 6 by suction pump 4.4 to complete the treatment of aquaculture wastewater. When the liquid level is less than 0.1m, the permeate pump stops to prevent the membrane from dredging due to low water level.

[0047] The mixed liquor of aquaculture wastewater treated by the SND-AO system enters the bottom of the sulfur autotrophic denitrification-SAD reactor 5 through the return inlets of tanks A3 and O4 via inlet II 5.3 for reaction. Inside the sulfur autotrophic denitrification-SAD reactor 5, there is a sulfur-containing biological packing material 5.1. This sulfur-containing biological carrier slowly releases sulfides as electron donors, enhancing sulfur autotrophic denitrification through hydrogen sulfide in the gas phase, while simultaneously enriching sulfur autotrophic bacteria to achieve deep denitrification. Simultaneously, the hydrogen sulfide gas in tank A3 is transported back to the SAD through the top outlet I 3.3 under the action of a vortex blower 3.11, providing electron donors, enhancing the denitrification effect, and ensuring system stability. The nitrogen gas produced can be discharged by activating the positive and negative pressure protectors 5.6 at the top of the sulfur autotrophic denitrification-SAD reactor 5, as detected by sensors. The wastewater after SAD treatment (SO4 produced by SAD) 2- The wastewater is returned to pool A 3 through return port V5.5, where it reacts and decomposes into H2S or provides an electron donor for SAD. This cycle is repeated to reduce sulfur waste and lower the content of sulfate byproducts. After the reaction, the wastewater flows into pool O 4. Finally, it reacts through membrane module 4.5 in pool O 4 to improve the quality of the effluent. The membrane effluent is then pumped by suction pump 4.4 to the effluent tank 6, completing the treatment of aquaculture wastewater.

[0048] In summary, the device of this invention integrates four main areas: a simultaneous short-cut nitrification-denitrification (SND) tank, an anaerobic tank (A tank), a sulfur autotrophic denitrification (SAD) tank, and an aerobic tank (O tank). Through zoned internal and external circulation, it synergistically treats nitrogen, sulfur, and organic pollutants, achieving deep denitrification of wastewater and efficient resource recycling. The flowchart of this device is as follows: Figure 3 As shown, the device of this invention can achieve self-circulation of SND-AO-SAD, and can also complete internal circulation of OA / SND and OA / SAD-A. Through the device's circulation and reflux, close material exchange is achieved. The segmented, deeply coupled design avoids the risk of stability being affected by fluctuations in the external environment (such as pH, dissolved oxygen, and electron donor concentration). Sulfate is reduced in tank A, and the hydrogen sulfide gas produced in the reaction is recycled back to SAD. This ensures sufficient electron donors in the sulfur autotrophic denitrification-SAD reactor while enhancing COD removal from wastewater in tank A and reducing sulfate content in the effluent. Simultaneously, sulfate produced in SAD is recycled back to tank A, where it is reduced to hydrogen sulfide in the gaseous phase and reacts with sulfur in the liquid phase. 2- By enhancing sulfur autotrophic denitrification to achieve deep denitrification, this material circulation setup enables the two reactors to mutually promote each other.

[0049] With this design, the device of this invention achieves efficient removal of nitrogen, sulfur, and organic pollutants from aquaculture wastewater, as well as the recycling of sulfur. It significantly improves the system's operational stability, treatment effect, and economy, and is particularly suitable for the efficient treatment of complex pollutants in aquaculture wastewater. The entire device system is compact, has low operating costs, low energy consumption, and stable treatment effects, achieving efficient deep denitrification of aquaculture wastewater without the need for additional carbon sources. Based on the microenvironment theory of simultaneous short-cut nitrification and denitrification and sulfur autotrophic denitrification technology, this invention denitrifies aquaculture wastewater through a system that deeply couples simultaneous short-cut nitrification and denitrification with sulfur autotrophic denitrification. PLC automatic control and membrane bioreactors ensure system stability, achieving the goal of efficiently removing organic pollutants and nitrogen pollution from aquaculture wastewater through simultaneous short-cut nitrification and denitrification.

[0050] Example 2

[0051] Taking the aquaculture wastewater from a certain aquaculture enterprise in Guangxi Zhuang Autonomous Region, after solid-liquid separation and phosphorus removal by chemical treatment, as the treatment target, the NH4 in the aquaculture wastewater... +The concentrations of nitrogen (N) and nitrogen (TN) are 400-500 mg / L, TN is 300-600 mg / L, COD is 2000-3000 mg / L, and pH is 8.2. The treatment is carried out using the apparatus described in Example 1, wherein the SND-AO system for simultaneous short-cut nitrification and denitrification uses an SND tank, an A tank, and an O tank (with the membrane module placed in the O tank) with effective volumes of 20.94 m³. 3 9.6m 3 4.0m 3 The pilot-scale reactor; the effective volume of the sulfur autotrophic denitrification-SAD reactor is 3m³. 3 The SAD reactor was equipped with a sulfur-autotrophic biological filler consisting of 60% polyurethane sponge and 40% sulfur-containing filler. The composite material's density, porosity, and specific surface area were 0.3~0.5 g / cm³. 3 15%~25%, 100~150cm 2 / g.

[0052] 1. System startup

[0053] (1) Start-up of the SND-AO system: Inoculate the system with sludge from the traditional AO process, adjust the system operating conditions to the SND operating control conditions, and carry out sludge acclimatization. The actual influent water quality of the aquaculture wastewater is COD=2000~3000mg / L, NH4+=2000~3000mg / L. + -N = 300~500 mg / L, TN = 400~600 mg / L. The aeration rate of the reactor is controlled by adjusting the frequency of the aeration blowers. The preset values ​​for DO (dissolved oxygen) in the SND tank are 0.3~0.5 mg / L, ORP (oxidation-reduction potential) is -50~+50 mv, and pH is 6.5-8.5. The DO in the anaerobic tank is controlled to be less than 0.1 mg / L, and the ORP is -120~-160 mv. The DO in the aerobic MBR tank is controlled between 2.0~3.0 mg / L. The mixed liquor from the aerobic tank is returned to the SND tank at a return ratio of 300%. The system MLSS (mixed liquor sludge concentration) is controlled at 6000-8000 mg / L, and sludge is discharged periodically. The membrane module operates at a flux of 12-15 LMH, producing water intermittently, with a 4-minute pumping cycle followed by a 1-minute stop. Automatic backwashing is employed, with a backwash cycle of 5-10 days and a backwash time of 20-30 minutes. Under these conditions, when the MBR effluent NH4... + When -N is less than 2 mg / L, COD concentration is less than 90 mg / L, and TN mass concentration is less than 30 mg / L, it indicates that the SND-AO system has started successfully.

[0054] (2) Start-up of the sulfur autotrophic denitrification-SAD reactor: The reactor is equipped with a replaceable sulfur autotrophic denitrification biological carrier module. During the start-up phase, sulfur autotrophic denitrification functional bacteria are inoculated, and sulfur-containing biological carriers are used to provide sulfur autotrophic denitrification bacteria with sulfur. 2- and use NO3 - Aquaculture wastewater with a nitrogen concentration of 30 mg / L was circulated into a SAD reactor to cultivate and acclimatize sulfur-autotrophic denitrifying bacteria. After 3 days of circulation, under continuous influent and effluent conditions, when the NO3 in the reactor effluent... - When the -N concentration is less than 10 mg / L, it indicates that the sulfur autotrophic denitrification-SAD reactor has been successfully started up.

[0055] (3) Coupling start-up of SND-AO system and sulfur autotrophic denitrification-SAD reactor system: Connect the corresponding circulation pipes, turn on the vortex blower to realize gas circulation, and pass the SAD effluent into tank A to enrich sulfate-reducing bacteria for SO4 production. 2- The reduction process involves recirculating the O-cell mixture back to the SND and A-cells, with recirculation ratios controlled at 300% and 100%, respectively. The SND-AO system mixture from the A and O-cells is then pumped into the bottom water distribution space of the SAD reactor, replenishing the S-cells. 2- and NO3 - -N (extracted from tanks A and O respectively), the mixed liquor reflux ratio is controlled according to an S:N ratio of 1.3. A vortex blower introduces the mixed gas containing H2S from the top of the anaerobic tank into the bottom of the SAD reactor. When the H2S concentration at the top of the SAD reactor exceeds 0.03 mg / m³... 3 At this time, increase the operating frequency of the fan to increase gas circulation. When the H2S concentration at the top is below 0.03 mg / m³, 3 When the frequency of the blower is reduced, the gas can be directly discharged into the atmosphere. When the gas circulation and sulfur recycling are started, the TN concentration of the effluent is less than 10 mg / L, indicating that the system has started successfully.

[0056] 2. System startup and operation

[0057] (1) The aquaculture wastewater is pumped into the SND-AO system via a lift pump in the water tank. The complete operation process includes water inlet, stirring, low-oxygen aeration, circulation return, and membrane effluent. In the SND tank, the wastewater is mixed by a stirrer, and the frequency of the aeration blower is controlled to control the aeration rate of the reactor. The DO content in the SND tank is controlled at 0.3~0.5 mg / L, ORP at -50~+50 mv, pH at 6.5-8.5, and hydraulic retention time at 2~3 days. The wastewater overflows into the anaerobic tank, where the DO is controlled at less than 0.1 mg / L, ORP at -120~-160 mv, and hydraulic retention time at 1~2 days. The wastewater overflows into the aerobic tank, where the DO is controlled at 2.0~3.0 mg / L, and the hydraulic retention time is 0.4~1 days. The mixed liquor from the aerobic tank is pumped back to the SND tank through the return port, with a return ratio of 300%. The aerobic tank is equipped with membrane modules, whose operation is automatically controlled by a level sensor. Operation begins when the liquid level is 1.0m above the membrane module, and stops when the liquid level is less than 0.1m. The membrane module operates at a flux of 12-15 LMH, with intermittent effluent extraction for 9 minutes followed by a 1-minute stop. Membrane cleaning is automatic, with a cleaning cycle of 5-10 days and a cleaning time of 20-30 minutes. The cleaning agent used is 0.2g / L sodium hypochlorite for online cleaning. After backwashing, the system automatically restarts.

[0058] (2) The mixed liquor from pools A and O of the SND-AO system is pumped into the bottom water distribution space of the sulfur autotrophic denitrification-SAD reactor through a reflux pipe. The reflux ratio of the mixed liquor from pool O is controlled according to the S / N ratio of 1.3, and the system is operated continuously for 24 hours. Sulfur autotrophic denitrification is enhanced by hydrogen sulfide in the gas phase. The S content inside the sulfur autotrophic denitrification-SAD reactor is... 2- The concentration determines the replacement time of the packing module to ensure sufficient electron donors in the sulfur autotrophic denitrification-SAD reactor.

[0059] The actual influent water quality for aquaculture wastewater is COD = 2000~3000 mg / L, NH4+ = 2000~3000 mg / L. + Under these conditions, with -N=300~500mg / L and TN=400~600mg / L, the final MBR effluent COD concentration after treatment by the system is less than 90.0mg / L and NH4+ is less than 400mg / L. + -N concentration less than 2.0 mg / L, TN mass concentration less than 5.0 mg / L, COD removal rate ≥97%, NH4 + -N removal rate ≥99%, TN removal rate ≥99%, and the specific operation and processing results of each step are shown in Table 1.

[0060] Comparative Example 1

[0061] The device used in this comparative example, which employs a deep coupling of SND-AO process with sulfur autotrophic denitrification for efficient treatment of aquaculture wastewater, differs from the device in Example 1 in that it does not perform sulfur recycling and gas reuse treatment. Instead, the aquaculture wastewater is directly passed through the SND tank, A tank, O tank, and sulfur autotrophic denitrification filter in sequence for treatment, and finally discharged from the sulfur autotrophic denitrification filter. The device's condition parameters are set in the same way as in Example 2.

[0062] The results of different treatment devices are shown in Table 1. The table shows that the device in Example 1 further removed COD, ammonia nitrogen, and total nitrogen from the aquaculture wastewater. The removal rates of ammonia nitrogen and TN in the effluent were ≥99%, and the SO4 content in the effluent was also reduced. 2- The concentration was effectively reduced. Compared with traditional denitrification processes, this device has a higher TN removal rate, and the device itself can reach alkalinity balance without the need for alkalinity replenishment. After operation, the pH fluctuation of the system is small, maintaining stable reaction conditions. Compared with ordinary two-stage AO systems for aquaculture wastewater treatment, the residence time is shorter, improving treatment efficiency. At the same time, this device ensures efficient TN removal from wastewater without the need for additional carbon source addition, pH adjustment, or low aeration, reducing sulfur waste and the content of by-products in the effluent. It effectively reduces system sludge production and wastewater treatment costs. It has the advantages of compact structure, low operating cost, low energy consumption, and stable treatment effect. It realizes efficient deep denitrification treatment of aquaculture wastewater without the need for additional carbon source addition, simplifies the denitrification process steps, and shows good potential for engineering applications.

[0063] Table 1. Operational processing results of the apparatus in Example 1 and Comparative Example 1

[0064]

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A device for efficient treatment of aquaculture wastewater by deep coupling of SND-AO process and sulfur autotrophic denitrification, characterized in that, The system comprises, in sequence, a culture wastewater tank (1), an SND-AO system, a sulfur autotrophic denitrification-SAD reactor (5), a water outlet tank (6) and an electrical automatic control system (7); The SND-AO system comprises, in sequence, an SND tank (2), an A tank (3) and an O tank (4); The SND tank (2) is provided with a water inlet (2.1), a sludge discharge valve (2.2), an aeration fan (2.3), a stirrer I (2.4), an aeration disc I (2.5), an overflow port I (2.6), a sensor assembly I and a backflow port I (2.14); the sludge discharge valve I (2.2) and the aeration disc I (2.5) are arranged at the bottom of the SND tank (2), the aeration disc I (2.5) is connected with the aeration fan (2.3), and wastewater enters the A tank (3) through the overflow port I (2.6); The A tank (3) is a closed tank, is in an anoxic state, and is related to the conversion of ammonia nitrogen; the A tank (3) is provided with a stirrer II (3.1), an overflow port II (3.2), an air outlet I (3.3), a backflow port II (3.4), a backflow port III (3.5), a sensor assembly II and a water outlet (3.10); the overflow port II (3.2) is arranged on the side close to the O tank (4) and opposite to the overflow port I (2.6); the air outlet I (3.3) is arranged at the top of the A tank (3) and connected with a vortex air pump (3.11); the backflow port II (3.4) is connected with a backflow port V (5.5) of the sulfur autotrophic denitrification-SAD reactor (5); the water outlet (3.10) is connected with a water inlet II (5.3) of the sulfur autotrophic denitrification-SAD reactor (5); and wastewater enters the O tank (4) through the overflow port II (3.2); The O tank (4) is provided with a stirrer III (4.1), an aeration disc II (4.2), a backflow port IV (4.3), a suction pump (4.4), a membrane assembly (4.5), a liquid level sensor (4.6) and a sensor assembly III; the aeration disc II (4.2) is arranged at the bottom of the O tank (4) and connected with the aeration fan (2.3); the membrane assembly (4.5) is connected with the suction pump (4.4) and the water outlet tank (6) in sequence; The sulfur autotrophic denitrification-SAD reactor (5) is provided with sulfur-containing biological fillers (5.1), a gas distribution disc (5.2), a water inlet II (5.3), an air outlet II (5.4), a backflow port V (5.5), a positive and negative pressure protector (5.6), a sensor assembly IV and a one-way valve (5.12); the gas distribution disc (5.2) and the water inlet II (5.3) are arranged at the bottom, the positive and negative pressure protector (5.6) is arranged at the top, the air outlet II (5.4) is connected with the vortex air pump (3.11) through the one-way valve (5.12); and sulfur autotrophic denitrification functional bacteria are inoculated on the sulfur-containing biological fillers (5.1); The backflow port IV (4.3) of the O tank (4) is connected with the backflow port I (2.14), the backflow port II (3.5) and the water inlet II (5.3) in sequence. The sensor assembly I in the SND tank (2) comprises: a pH sensor (2.7), a DO sensor I (2.8), an ORP sensor I (2.9), an MLSS sensor (2.10), an NH4 + -N sensor (2.11), a NO2 - -N sensor I (2.12), a NO3 - -N sensor I (2.13); The sensor assembly II in the A tank (3) comprises: an H2S gas sensor I (3.6), an ORP sensor II (3.7), a DO sensor II (3.8), an S 2- ensor I (3.9); The sensor assembly III in the O-pool (4) comprises: a DO sensor III (4.7), a NO3 - -N sensor II (4.8); Sensor package IV in the Sulfur Autotrophic Denitrification - SAD reactor (5) comprises: H2S gas sensor II (5.7), NO2 - -N sensor II (5.8), NO3 - -N sensor III (5.9), S 2- sensor II (5.10), SO4 2- sensor (5.11); The electric automatic control system (7) is electrically connected with the aquaculture wastewater tank (1), the aeration fan (2.3), the agitator I (2.4), the agitator II (3.1), the agitator III (4.1), the sensor assembly I-IV, the liquid level sensor (4.6), the membrane assembly (4.5) and the suction pump (4.4). The device controls the DO content in the SND pool to be 0.3-0.5 mg / L, the ORP to be -50-+50 mv, the pH to be 6.5-8.5, and the hydraulic retention time to be 3-4 d; the DO in the A pool is controlled to be less than 0.1 mg / L, the ORP is -120--160 mv, and the hydraulic retention time is 1-2 d; the DO in the O pool is controlled to be 2.0-3.0 mg / L, and the hydraulic retention time is 0.5-1 d; the mixed liquid in the O pool is pumped back to the SND pool and the A pool through the reflux port, and the reflux ratios are set to be 300% and 100% respectively; the mixed liquid in the A pool and the O pool is pumped into the bottom water distribution space of the SAD reactor, the hydraulic retention time is set to be 0.2-0.3 d, the mixed liquid reflux ratio is controlled according to the S / N ratio 1.3, and the device is continuously operated for 24 h. The device can realize self-circulation treatment of SND-AO-SAD, and also realize internal circulation treatment of O-A / SND, O-A / SAD-A.

2. The apparatus of claim 1, wherein The aquaculture wastewater tank (1) is provided with a lifting pump (1.1), an electromagnetic valve (1.2) and a flowmeter (1.3) connected in sequence, and is connected with the water inlet (2.1) of the SND pool (2).

3. The apparatus of claim 1, wherein The electric automatic control system (7) is provided with a PLC control box (7.1) and a computer (7.2) connected in sequence.

4. The device of claim 1 is applied to the treatment of aquaculture wastewater.

5. A method for efficient treatment of aquaculture wastewater by deep coupling of SND-AO process and sulfur autotrophic denitrification, characterized in that, The device of any one of claims 1-3 is used for treating aquaculture wastewater.

6. The method of claim 5, wherein, The device controls the DO content in the SND pool to be 0.3-0.5 mg / L, the ORP to be -50-+50 mv, the pH to be 6.5-8.5, and the hydraulic retention time to be 3-4 d; the DO in the A pool is controlled to be less than 0.1 mg / L, the ORP is -120--160 mv, and the hydraulic retention time is 1-2 d; the DO in the O pool is controlled to be 2.0-3.0 mg / L, and the hydraulic retention time is 0.5-1 d; the mixed liquid in the O pool is pumped back to the SND pool and the A pool through the reflux port, and the reflux ratios are set to be 300% and 100% respectively; the mixed liquid in the A pool and the O pool is pumped into the bottom water distribution space of the SAD reactor, the hydraulic retention time is set to be 0.2-0.3 d, the mixed liquid reflux ratio is controlled according to the S / N ratio 1.3, and the device is continuously operated for 24 h.

7. The method of claim 5 or 6, wherein, The membrane assembly in the O pool operates at a flux of 12-15 LMH, and the water is intermittently pumped out, with pumping for 8-9 min and stopping for 1-2 min.

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