Aquaculture tail water treatment process and treatment system

Abstract

The present application belongs to the technical field of sewage treatment, and particularly relates to a water treatment process and system for tail water from aquaculture. The process includes buffering the tail water generated from aquaculture through a buffering mechanism, removing suspended solids through a sedimentation mechanism, filtering out large particulate matter through a filtration mechanism, oxidizing and decomposing organic pollutants in the water through an aeration mechanism, reducing most of the COD, total nitrogen and total phosphorus under the action of microorganisms through a biological purification mechanism, and finally treating the water through a filler mechanism to further reduce the concentration of total nitrogen and total phosphorus in the water using the electrochemical and microbial synergistic effect of the iron-carbon micro-electrolysis and pyrite system to obtain the final effluent. The present application aims to solve the problem of comprehensive treatment of tail water from aquaculture and ensure that the tail water can meet the discharge standard, thereby ensuring the sustainable and healthy development of the aquaculture industry.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a process and system for treating aquaculture wastewater. Background Technology

[0002] In recent years, aquaculture has developed a high-input, high-output model. Excrement and uneaten feed from various aquatic products have accumulated over a long period of time, seriously disrupting the ecological balance of aquaculture water bodies and causing them to lose their self-regulating function. This has led to large-scale outbreaks of infectious diseases and caused serious economic losses to aquaculture operators. At the same time, the high concentrations of pollutants such as total nitrogen and total phosphorus in aquaculture wastewater can enter natural water bodies through wastewater discharge outlets, threatening the ecological security of the aquatic environment.

[0003] Due to the large volume and high concentration of pollutants in wastewater discharged from high-density aquaculture, existing treatment technologies cannot guarantee stable compliance with discharge standards. Furthermore, they are insufficiently resistant to shock loads from sudden heavy rainfall and other extreme weather events, resulting in poor wastewater treatment efficiency and stability. Therefore, efficient, green, and sustainable treatment of wastewater from high-density aquaculture is particularly important, as its efficient treatment is crucial for the sustainable and healthy development of the aquaculture industry. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a process and system for treating aquaculture wastewater, which solves the comprehensive treatment of aquaculture wastewater, ensures the treatment system's resistance to extreme weather events, guarantees that aquaculture wastewater meets discharge standards, and maintains the sustainable and healthy development of the aquaculture industry.

[0005] The technical solution adopted in this application to address this technical problem is as follows:

[0006] A process for treating aquaculture wastewater includes the following steps:

[0007] Step S1: The wastewater generated by aquaculture enters the buffer mechanism through the wastewater outlet, where it undergoes buffering treatment and initial sedimentation to produce the first wastewater.

[0008] Step S2: The first tailwater obtained in step S1 enters the sedimentation unit, where suspended solids are removed during the sedimentation process to form the second tailwater;

[0009] Step S3: The second tailwater obtained in step S2 is filtered through a filtration mechanism to remove large particulate matter, effectively reducing the concentration of suspended solids and the turbidity of the tailwater, thus obtaining the third tailwater.

[0010] Step S4: The third tailwater obtained in step S3 enters the aeration unit, where the organic pollutants in the water are oxidized and decomposed through the aeration process to produce the fourth tailwater.

[0011] Step S5: The fourth tailwater obtained in step S4 enters the biological purification unit. Under the action of microorganisms, most of the COD, total nitrogen, and total phosphorus indicators are reduced, forming the fifth tailwater.

[0012] Step S6: The fifth tailwater obtained in step S5 is treated by the packing mechanism. By utilizing the synergistic effect of iron-carbon micro-electrolysis and the electrochemical and microbial effects of the pyrite system, the concentration of total nitrogen and total phosphorus in the water is further reduced to obtain the final effluent.

[0013] Furthermore, the buffer mechanism is a buffer ditch, the sedimentation mechanism is a sedimentation tank, the filtration mechanism is an overflow filter dam, the aeration mechanism is an aeration tank, the biological purification mechanism is a biological purification tank, and the packing mechanism is a packing filter dam.

[0014] A system for treating aquaculture wastewater, used to implement the above-mentioned aquaculture wastewater treatment process, includes a buffer ditch, a sedimentation tank, an overflow filter dam, an aeration tank, a biological purification tank, and a packing filter dam. One end of the buffer ditch has a wastewater inlet, and the other end is connected to the sedimentation tank. The sedimentation tank is connected to the overflow filter dam, and the other end of the overflow filter dam is connected to the aeration tank. The aeration tank is connected to the biological purification tank, and the biological purification tank is connected to the packing filter dam. The other end of the packing filter dam has a main outlet, which includes a first outlet, a second outlet, and a third outlet. The first outlet is connected to an external river; the second outlet is connected to the inlet of the aquaculture tank; and the third outlet is connected to the buffer ditch.

[0015] Furthermore, the filler filter dam is composed of an iron-carbon micro-electrolysis coupled pyrite filler layer and a gravel layer, wherein the iron-carbon micro-electrolysis coupled pyrite filler layer is located above the gravel layer, and the volume ratio of the iron-carbon micro-electrolysis coupled pyrite filler layer to the gravel layer is greater than or equal to 5:1.

[0016] Furthermore, the iron-carbon micro-electrolysis coupled pyrite filler layer is composed of a granular mixture of three raw materials: waste iron filings, activated carbon, and pyrite. By mass percentage, the iron-carbon micro-electrolysis coupled pyrite filler contains 33%–50% waste iron filings, 17%–25% activated carbon, and 25%–50% pyrite.

[0017] Furthermore, the gravel particles in the gravel layer have a particle size of 20mm-30mm, and the waste iron particles in the iron-carbon micro-electrolysis coupled pyrite filler layer have a particle size of 6-8mm, activated carbon particles have a particle size of 3-5mm, and pyrite particles have a particle size of 10-12mm.

[0018] Furthermore, the waste iron filings are pretreated before being made into iron-carbon micro-electrolytic coupling pyrite filler. The pretreatment method is as follows: soaking in 10% NaOH solution for 3 hours, then soaking in 10% dilute hydrochloric acid for 1 hour, washing with pure water until neutral, and drying in an oven at 70°C.

[0019] Furthermore, the biological purification tank is equipped with a microbial carrier, which is a biochemical cotton and a biological filter brush. The biological filter brush includes a skeleton and carrier filaments. The carrier filaments extend outward from the skeleton to form a permeable material with water distribution channels evenly distributed inside. The biochemical cotton and the biological filter brush are arranged alternately and are evenly distributed in the biological purification tank.

[0020] Furthermore, the filter media in the overflow filter dam is composed of pebbles, zeolite, and crushed stone, with a volume ratio of pebbles, zeolite, and crushed stone of 1:1:1.

[0021] Furthermore, the buffer ditch has a certain width and depth, and natural zeolite is laid in the buffer ditch; emergent plants and submerged plants are planted in the buffer ditch, and the planting area of ​​submerged plants in the buffer ditch is greater than or equal to 30% of the water surface area of ​​the buffer ditch; a gate or water pump for regulating the flow is provided at the inlet end of the buffer ditch.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention adds a buffer ditch before the traditional three-pond, two-dam process. Through the adsorption and purification capacity of aquatic plants in the ecological ditch, the water intake load of the three-pond, two-dam process is reduced, which can increase the total phosphorus removal rate of the composite three-pond, two-dam process by more than 40%. Secondly, the buffer ditch also has water storage capacity, which can alleviate the pressure of floods on the three-pond, two-dam process under extreme weather conditions. It is a treatment system that integrates physical, chemical and biological purification methods and is suitable for various aquaculture models.

[0024] 2. The packing material in the filter dam of the present invention adopts the method of iron-carbon micro-electrolysis coupled with pyrite. The alkalinity generated by iron-carbon micro-electrolysis can neutralize the acidity generated by sulfur autotrophic denitrification, stabilize the pH of the effluent, and thus provide a good reaction environment for the denitrifying bacteria in the downstream effluent.

[0025] 3. Compared with the prior art, the present invention uses a biological purification pond instead of an ecological purification pond, which greatly reduces the land area required. Attached Figure Description

[0026] Figure 1 This is a diagram of the experimental apparatus of the present invention (front view);

[0027] Figure 2 This is a top view of the experimental apparatus of the present invention;

[0028] Figure 3 This is a diagram showing the influence of different fillers in the filler filter dam on the pH of the effluent in Example 1;

[0029] Figure 4 This is a comparison chart of the total nitrogen removal rates of different packing materials in the packing filter dam in Example 1;

[0030] Figure 5 This is a comparison diagram of the nitrate nitrogen removal system of different packing materials in the packing filter dam in Example 1;

[0031] Figure 6 This is a comparison chart of the denitrification effects of pyrite packing with different proportions of iron-carbon micro-electrolysis coupling in Example 2.

[0032] Figure 7 This is a comparison diagram of the effect of buffer ditches on denitrification efficiency in Example 3.

[0033] Figure 8 This is a diagram showing the total phosphorus removal effect in Example 4;

[0034] Figure 9 This is a diagram showing the total nitrogen removal effect in Example 4;

[0035] Figure 10 This is a connection diagram of the aquaculture wastewater treatment system of the present invention.

[0036] The attached diagram is labeled as follows: 1. Aquaculture pond; 2. Buffer ditch; 3. Sedimentation pond; 4. Overflow filter dam; 5. Aeration pond; 6. Biological purification pond; 7. Packed filter dam; 8. Main outlet; 9. First outlet; 10. Second outlet; 11. Third outlet. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0038] like Figure 10 As shown, this invention provides a treatment system for aquaculture wastewater, including a buffer ditch 2, a sedimentation tank 3, an overflow filter dam 4, an aeration tank 5, a biological purification tank 6, and a packing filter dam 7. The buffer ditch 2 is connected to the outlet of the aquaculture wastewater, and the buffer ditch 2 is directly connected to the sedimentation tank 3. An overflow filter dam 4 is provided between the sedimentation tank 3 and the aeration tank 5. The aeration tank 5 is directly connected to the biological purification tank 6, and a packing filter dam 7 is provided between the biological purification tank 6 and the main outlet 8. The aquaculture wastewater passes through the buffer ditch 2, the water flow rate is controlled, and the residence time of the aquaculture wastewater in the buffer ditch 2 is adjusted. After removing a small portion of suspended solids and nutrients such as N and P, the first wastewater is produced. The first wastewater is treated by the three tanks and two dams, and the final wastewater meets the discharge standards. The aforementioned "controlling the water flow rate" is achieved by pumping or controlling the gate opening. In this embodiment, the pumping speed of the pump in the experimental device is used, and it is set at the inlet end of the buffer ditch 2.

[0039] The buffer ditch 2 is lined with natural zeolite and planted with emergent and submerged plants. The emergent plants are yellow irises, and the submerged plants are pink myriophyllum. This utilizes the adsorption capacity of the plants to purify nitrogen and phosphorus in the effluent. At the same time, the roots of the yellow irises can reinforce the banks. The planting area of ​​the submerged plants in the buffer ditch 2 is greater than or equal to 30% of the water surface area of ​​the buffer ditch 2. The natural zeolite lining the buffer ditch 2 prevents soil erosion and ditch collapse caused by water flow impact. On the other hand, it also facilitates microbial attachment, achieving some treatment of N and P elements. The emergent plants can reduce the water flow velocity and maintain soil and water conservation. The pink myriophyllum can utilize the N and P in the water for growth, and the N and P elements consumed can reduce the treatment load of the subsequent three pools and two dams. By monitoring the effluent water quality of the buffer ditch 2, the hydraulic retention time in the buffer ditch 2 can be reasonably controlled.

[0040] The main outlet 8 includes a first outlet 9, a second outlet 10, and a third outlet 11. The first outlet 9 is connected to an external river for discharging treated wastewater that meets the standards. The second outlet 10 is connected to the inlet of the aquaculture pond 1, enabling the reuse of treated wastewater that meets the standards, thus reducing the demand for external water. The third outlet 11 is connected to a buffer ditch 2, where wastewater that does not meet the standards is returned to the buffer ditch 2 for reprocessing, while also diluting the concentration of aquaculture wastewater in the buffer ditch 2, which is beneficial for subsequent treatment.

[0041] The filter dam 7 consists of an iron-carbon micro-electrolysis coupled pyrite packing layer and a gravel layer. The iron-carbon micro-electrolysis coupled pyrite packing layer is located above the gravel layer, and the volume ratio of the iron-carbon micro-electrolysis coupled pyrite packing layer to the gravel layer is 5:1. The gravel acts as a substrate, mainly supporting the iron-carbon micro-electrolysis coupled pyrite packing layer and preventing it from being covered by sludge, which would have an adverse effect. During the denitrification process of nitrogen and phosphorus removal in the upstream biological purification tank 6 and on the pyrite, the denitrifying bacteria cause the water pH to drop to 4-5. While filtering the water, the iron-carbon micro-electrolysis coupled pyrite packing layer can also improve the water pH during the wastewater treatment process, preventing the effluent entering the river from having too low a pH, which would affect the activity of beneficial bacteria in the external environment. At the same time, the iron-carbon micro-electrolysis denitrifies and produces NH4. + It can also be utilized by denitrifying bacteria to carry out denitrification.

[0042] The working mechanism of the iron-carbon micro-electrolytic coupling pyrite filler of the present invention is as follows:

[0043] Sulfur autotrophic denitrification: 6NO - +2FeS2+4H2O→3N2+4SO4 2- +2Fe(OH)3+2H +

[0044] 55S+50NO3 - +38H2O+20CO2+4NH4 + →4C5H7O2N+55SO4 2- +64H +

[0045] Iron-carbon micro-electrolysis to remove nitrogen: NO3 - +4Fe 0 +7H + →NH4 + +4Fe 2+ +3OH -

[0046] The iron-carbon micro-electrolysis coupled pyrite packing is composed of waste iron filings, activated carbon, and pyrite. By mass percentage, the waste iron filings account for 33% to 50%, activated carbon for 17% to 25%, and pyrite for 25% to 50%.

[0047] Preferably, the mass ratio of waste iron filings, activated carbon, and pyrite in the iron-carbon micro-electrolysis coupled pyrite filler is 2:1:2, that is, by mass percentage, waste iron filings 40%, activated carbon 20%, and pyrite 40%.

[0048] The gravel has a particle size of 20mm-30mm, and the waste iron scrap in the iron-carbon micro-electrolysis coupled pyrite filler has a particle size of 8mm, activated carbon has a particle size of 5mm, and pyrite has a particle size of 10mm.

[0049] A suitable particle size is beneficial for the contact between the iron-carbon micro-electrolysis coupled pyrite packing and the water flow, without creating excessive resistance to the water flow. In the iron-carbon micro-electrolysis coupled pyrite packing, waste iron filings and pyrite are consumed. Therefore, the three materials are made into granules to achieve contact between them. This also facilitates the subsequent replenishment of materials and avoids the water treatment effect being hindered by the activated carbon covering the particle surface after the powder is mixed and cannot be consumed.

[0050] The waste iron filings are pretreated before being made into iron-carbon micro-electrolysis coupled pyrite filler. The pretreatment method is as follows: soaking in 10% NaOH solution for 3 hours, then soaking in dilute hydrochloric acid for 1 hour, washing with pure water until neutral, and drying in an oven at 70°C. The above treatment can remove impurities from the surface of the waste iron filings, fully expose the waste iron filings, and allow them to fully contact with water, thereby increasing the reaction rate.

[0051] The sedimentation tank 3 is planted with submerged plants, and the planting area of ​​submerged plants in the sedimentation tank 3 accounts for 30% of the area of ​​the sedimentation tank 3. This can slow down the influent flow rate and effectively settle suspended matter. At the same time, the submerged plant Myriophyllum spicatum also plays a role in adsorbing nitrogen and phosphorus.

[0052] The biological purification tank 6 is equipped with a microbial carrier, which consists of biochemical cotton and a biological filter brush. The biological filter brush includes a skeleton and carrier filaments. The carrier filaments extend outward from the skeleton to form a permeable material with water distribution channels evenly distributed inside. The biochemical cotton and the biological filter brush are arranged alternately and are evenly distributed in the biological purification tank 6.

[0053] The biochemical cotton has good air permeability and high mechanical strength. The gaps in the biochemical cotton can provide a space for microorganisms to attach and grow, while also serving as a filter. The brush uses iron wire (steel wire) as a skeleton and outward-extending PE material fine bristles as carrier filaments. The brush is placed vertically in the purification tank. The PE material fine bristles can provide a space for microorganisms to attach and grow. The biochemical cotton and biological filter brush are arranged alternately and evenly distributed in the biological purification tank 6. While ensuring sufficient drainage cross-section, it occupies as large a volume as possible to provide a basis for microorganism attachment. After purification by microorganisms, the concentrations of nitrate nitrogen and total phosphorus in the water are reduced.

[0054] The filter media in the overflow filter dam 4 is composed of pebbles, zeolite, and crushed stone, with a volume ratio of 1:1:1. Through the interception effect of the filter media, the concentration of suspended solids in the water can be effectively reduced, and the turbidity of the effluent can be reduced.

[0055] In specific implementation, the aquaculture wastewater treatment process of the present invention includes the following steps:

[0056] S1: The wastewater from aquaculture enters buffer ditch 2 from the wastewater outlet. Buffer ditch 2 has a certain depth and width. By controlling the water flow speed, the residence time of the wastewater in buffer ditch 2 is extended, thereby increasing the sedimentation rate of suspended matter in the wastewater. Emergent plants such as yellow iris are planted on the banks of buffer ditch 2, and submerged plants such as pink myriophyllum are planted in the ditch. The planting area accounts for 30% of the water surface, which can effectively reduce the concentration of nitrogen and phosphorus in the water, reduce the pollutant load of the three ponds and two dams, monitor the water quality of the effluent from buffer ditch 2, and thus rationally regulate the hydraulic residence time in buffer ditch 2.

[0057] S2: The tailwater that has been treated by the buffer ditch 2 then enters the sedimentation tank 3. The sedimentation tank 3 is planted with the submerged plant Myriophyllum sp., which can slow down the flow rate of the incoming water and effectively settle suspended matter. At the same time, the submerged plant Myriophyllum sp. also plays a role in adsorbing nitrogen and phosphorus.

[0058] S3: The effluent treated by the sedimentation tank 3 then flows into the overflow filter dam 4. Through the interception effect of the filter media, the concentration of suspended solids in the water can be effectively reduced, and the turbidity of the effluent can be reduced.

[0059] S4: The effluent treated by the overflow filter dam 4 enters the aeration tank 5, where the concentrations of COD and ammonia nitrogen are reduced through aeration oxidation, volatilization and decomposition.

[0060] S5: The effluent treated by the aeration tank 5 enters the biological purification tank 6. After purification by microorganisms, the concentrations of nitrate nitrogen and total phosphorus in the water are reduced.

[0061] S6: The effluent treated by the biological purification tank 6 enters the packing filter dam 7. Through the iron-carbon micro-electrolysis coupled with the pyrite system, the concentration of nitrate nitrogen in the water can be effectively reduced to obtain the final effluent.

[0062] Experimental materials:

[0063] like Figure 1 and Figure 2 As shown, this invention is based on a storage box and a glass tank to construct a composite three-pool, two-dam treatment system. Different "pools" and "dams" are separated by partitions with water passage holes. The overflow filter dam 4 is made of pebbles, zeolite, and crushed stone. The aeration device of the aeration pool 5 uses an air compressor in conjunction with the aeration pipeline. The biological purification pool 6 uses biochemical cotton and biological filter brushes. The packing filter dam 7 is made of treated waste iron filings, activated carbon, and pyrite.

[0064] The device is placed in the warehouse of the aquaculture pond of Zhengzhou Wanshui Qianshan Agricultural Co., Ltd., and the aquaculture wastewater is directly drawn from the aquaculture pond.

[0065] Example 1:

[0066] By using only packed dams, we tested the effects of iron-carbon micro-electrolysis coupled with pyrite layers and gravel layers as packing materials, iron-carbon micro-electrolysis material layers (waste iron filings and activated carbon in a 1:1 mass ratio) and gravel layers as packing materials, and iron-carbon micro-electrolysis coupled with pyrite packing materials (waste iron filings, activated carbon, and pyrite in a 1:1:2 mass ratio) and gravel layers as packing materials, keeping other conditions consistent. We evaluated the effectiveness of iron-carbon micro-electrolysis coupled with pyrite packing materials in stabilizing water pH and denitrification compared to using pyrite packing materials or iron-carbon micro-electrolysis materials alone. The results are as follows: Figure 3 , Figure 4 and Figure 5 As shown in the figure, it is clear that compared with using pyrite packing material or iron-carbon micro-electrolysis material alone, iron-carbon micro-electrolysis coupled with pyrite packing material shows better effect in stabilizing the pH value of water, and also significantly improves the removal rate of total nitrogen and nitrate nitrogen.

[0067] Example 2:

[0068] Using a composite three-pool two-dam treatment system, waste iron filings, activated carbon, and pyrite were mixed in different mass ratios to prepare iron-carbon micro-electrolysis coupled pyrite packing in the packed filter dam 7. This mixture was then applied to the composite three-pool two-dam treatment system, with all other conditions remaining the same. The denitrification effect of the iron-carbon micro-electrolysis coupled pyrite packing with different formulation ratios was tested. The results are as follows: Figure 6As shown in the figure, the experimental group with a ratio of 2:1:1 of waste iron filings, activated carbon, and pyrite had the strongest denitrification effect, but its stability was insufficient and the denitrification effect fluctuated too much. The experimental group with a ratio of 2:1:2 of waste iron filings, activated carbon, and pyrite had higher treatment efficiency and longer service life, and good treatment stability. The other two experimental groups had lower denitrification efficiency.

[0069] Example 3:

[0070] Instead of using buffer ditch 2, water was directly fed into sedimentation tank 3. The impact of buffer ditch 2 on the denitrification process of this invention was tested, and the test results are as follows: Figure 7 As shown, buffer ditch 2 can effectively reduce the denitrification load of the subsequent three pools and two dams, ensuring the water treatment effect.

[0071] To investigate whether buffer ditch 2 had any impact on the denitrification process of this invention, the device was deactivated on day 11, and water was directly fed into sedimentation tank 3, with all other operating conditions remaining unchanged. Figure 7 The results shown indicate that without the buffer ditch 2, the total nitrogen removal rate of the effluent decreased significantly, with an average removal rate of 39.5%. Therefore, it can be concluded that the presence of the buffer ditch 2 can improve the total nitrogen removal efficiency of the present invention.

[0072] Example 4:

[0073] A composite three-pool, two-dam treatment system was used. In the iron-carbon micro-electrolysis coupled pyrite packing material of dam 7, the mass ratio of waste iron filings, activated carbon, and pyrite was 2:1:2. This system comprehensively treated aquaculture wastewater, with a heat treatment time (HRT) of 24 hours. The purification effect of aquaculture wastewater within 20 days was as follows: Figure 8 and Figure 9 As shown, the composite three-pond-two-dam system of this invention can achieve long-term compliance with ecological treatment standards for aquaculture wastewater with a relatively low HRT. The buffer ditch 2 can alleviate the pollutant load of the three-pond-two-dam system, and its strong water storage capacity can cope with the impact of floods on the three-pond-two-dam system under extreme weather conditions. The coupling of iron-carbon materials and pyrite enhances the sulfur autotrophic denitrification capacity of denitrifying bacteria, improves the removal rate of total nitrogen and nitrate nitrogen, and realizes the composite process and the composite packing material.

[0074] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Claims

1. A process for treating aquaculture wastewater, characterized in that, Includes the following steps: Step S1: The wastewater generated by aquaculture enters the buffer mechanism through the wastewater outlet, where it undergoes buffering treatment and initial sedimentation to produce the first wastewater. Step S2: The first tailwater obtained in step S1 enters the sedimentation unit, where suspended solids are removed during the sedimentation process to form the second tailwater; Step S3: The second tailwater obtained in step S2 is filtered through a filtration mechanism to remove large particulate matter, effectively reducing the concentration of suspended solids and the turbidity of the tailwater, thus obtaining the third tailwater. Step S4: The third tailwater obtained in step S3 enters the aeration unit, where the organic pollutants in the water are oxidized and decomposed through the aeration process to produce the fourth tailwater. Step S5: The fourth tailwater obtained in step S4 enters the biological purification unit. Under the action of microorganisms, most of the COD, total nitrogen, and total phosphorus indicators are reduced, forming the fifth tailwater. Step S6: The fifth effluent obtained in step S5 is treated by a packing mechanism. Utilizing the synergistic effect of iron-carbon micro-electrolysis and the electrochemical and microbial processes of the pyrite system, the concentrations of total nitrogen and total phosphorus in the water are further reduced to obtain the final effluent. The packing structure is a packing filter dam (7), which is composed of an iron-carbon micro-electrolysis coupled pyrite packing layer and a gravel layer. The iron-carbon micro-electrolysis coupled pyrite packing layer is located above the gravel layer, and the volume ratio of the iron-carbon micro-electrolysis coupled pyrite packing layer to the gravel layer is greater than or equal to 5:

1. The iron-carbon micro-electrolysis coupled pyrite filler layer is composed of a granular mixture of three raw materials: waste iron filings, activated carbon, and pyrite. By mass percentage, the iron-carbon micro-electrolysis coupled pyrite filler contains 40% waste iron filings, 20% activated carbon, and 40% pyrite. The gravel particles in the gravel layer have a particle size of 20mm-30mm, while the waste iron filings in the iron-carbon micro-electrolysis coupled pyrite filler layer have a particle size of 6-8mm, activated carbon particles have a particle size of 3-5mm, and pyrite particles have a particle size of 10-12mm.

2. The aquaculture wastewater treatment process according to claim 1, characterized in that, The buffer mechanism is a buffer ditch (2), the sedimentation mechanism is a sedimentation tank (3), the filtration mechanism is an overflow filter dam (4), the aeration mechanism is an aeration tank (5), and the biological purification mechanism is a biological purification tank (6).

3. A system for treating aquaculture wastewater, implementing the aquaculture wastewater treatment process described in any one of claims 1-2, characterized in that, The system includes a buffer ditch (2), a sedimentation tank (3), an overflow filter dam (4), an aeration tank (5), a biological purification tank (6), and a packing filter dam (7). One end of the buffer ditch (2) is provided with a tailwater inlet and the other end is connected to the sedimentation tank (3). The sedimentation tank (3) is connected to the overflow filter dam (4). The other end of the overflow filter dam (4) is connected to the aeration tank (5). The aeration tank (5) is connected to the biological purification tank (6). The biological purification tank (6) is connected to the packing filter dam (7). The other end of the packing filter dam (7) is provided with a main outlet (8). The main outlet (8) includes a first outlet (9), a second outlet (10), and a third outlet (11). The first outlet (9) is connected to an external river. The second outlet (10) is connected to the inlet of the aquaculture pond. The third outlet (11) is connected to the buffer ditch (2).

4. The aquaculture wastewater treatment system according to claim 3, characterized in that, The waste iron filings are pretreated before being made into iron-carbon micro-electrolysis coupled pyrite filler. The pretreatment method is as follows: soaking in 10% NaOH solution for 3 hours, then soaking in 10% dilute hydrochloric acid for 1 hour, washing with pure water until neutral, and drying in an oven at 70°C.

5. The aquaculture wastewater treatment system according to claim 3, characterized in that, The biological purification tank (6) is equipped with a microbial carrier, which is a biochemical cotton and a biological filter brush. The biological filter brush includes a skeleton and carrier filaments. The carrier filaments extend outward from the skeleton to form a permeable material with water distribution channels evenly distributed inside. The biochemical cotton and the biological filter brush are arranged at intervals and are evenly distributed in the biological purification tank (6).

6. The aquaculture wastewater treatment system according to claim 3, characterized in that, The filter media in the overflow filter dam (4) consists of pebbles, zeolite, and crushed stone, with a volume ratio of 1:1:

1.

7. The aquaculture wastewater treatment system according to claim 3, characterized in that, The buffer ditch (2) has a certain width and depth, and natural zeolite is laid in the buffer ditch (2); emergent plants and submerged plants are planted in the buffer ditch (2), and the planting area of ​​submerged plants in the buffer ditch (2) is greater than or equal to 30% of the water surface area of ​​the buffer ditch (2); a gate or water pump for regulating the flow is provided at the inlet end of the buffer ditch (2).

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