Aquaculture tail water treatment process and treatment system

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to an aquaculture tail water treatment process and treatment system. The process comprises the following steps: tail water generated by aquaculture is subjected to buffer treatment through a buffer mechanism, then enters a precipitation mechanism to remove suspended solids, then passes through a filtering mechanism to filter out large-particle substances, then enters an aeration mechanism to oxidize and decompose organic pollutants in water through an aeration process, and finally enters a biological purification mechanism to purify the tail water under the action of microorganisms. And finally, the wastewater is treated by the filling mechanism, and the concentrations of the total nitrogen and the total phosphorus in the water are further reduced by utilizing the electrochemical and microorganism synergistic effect of iron-carbon micro-electrolysis and a pyrite system, so that final effluent is obtained. The invention aims to solve the problem of comprehensive treatment of the aquaculture tail water and ensure that the tail water can reach the discharge standard, so that the continuous and healthy development of the aquaculture industry is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to an aquaculture tail water treatment process and a treatment system. Background Art

[0002] In recent years, the aquaculture industry has shown a high-input, high-output development model. The excrement and leftover bait of various aquatic products have accumulated over a long period of time, seriously damaging the ecological balance of aquaculture water bodies and losing their own regulatory functions, resulting in large-scale infectious diseases and causing serious economic losses to aquaculture entities. At the same time, the concentrations of pollutants such as total nitrogen and total phosphorus in aquaculture effluents are relatively high, which will enter natural water bodies through the effluent discharge outlets, posing a threat to the ecological security of the water environment.

[0003] Due to the large discharge volume and high concentration of pollutants in high-density aquaculture tailwater, the existing treatment technology cannot ensure that the tailwater is stably discharged up to standard. In addition, the impact load is insufficient in the face of sudden heavy rain and other extreme weather conditions, and the tailwater treatment efficiency and stability are poor. Therefore, how to efficiently, greenly and sustainably treat high-density aquaculture wastewater is particularly important, and its efficient treatment is related to the sustainable and healthy development of the aquaculture industry. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an aquaculture tailwater treatment process and a treatment system to solve the comprehensive treatment of aquaculture tailwater, ensure the treatment system's ability to resist the impact of extreme weather, ensure that aquaculture tailwater is discharged in compliance with the standards, and maintain the sustainable and healthy development of the aquaculture industry.

[0005] The technical solution adopted in this application to solve this technical problem is:

[0006] A process for treating tail water from aquaculture, comprising the following steps:

[0007] Step S1: the tail water generated by aquaculture enters the buffer mechanism through the tail water outlet, where it is buffered and initially settled to generate the first tail water;

[0008] Step S2: the first tail water obtained in step S1 enters the sedimentation mechanism, and the suspended matter is removed during the sedimentation process to form the second tail water;

[0009] Step S3: The second tail water obtained in step S2 is filtered through a filtering mechanism to filter out large particles therein, thereby effectively reducing the concentration of suspended matter in the water and the turbidity of the tail water, thereby obtaining third tail water;

[0010] Step S4: the third tail water obtained in step S3 enters the aeration mechanism, and is oxidized and decomposed into organic pollutants in the water through the aeration process to produce fourth tail water;

[0011] Step S5: the fourth tail water obtained in step S4 enters the biological purification mechanism, and under the action of microorganisms, most of the COD, total nitrogen and total phosphorus indicators are reduced to form the fifth tail water;

[0012] Step S6: The fifth tail water obtained in step S5 is treated by a packing mechanism, and the electrochemical and microbial synergistic effect of iron-carbon micro-electrolysis and pyrite system is utilized to further reduce the concentration of total nitrogen and total phosphorus in the water 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 filtration dam, the aeration mechanism is an aeration tank, the biological purification mechanism is a biological purification tank, and the filler mechanism is a filler filtration dam.

[0014] A system for treating aquaculture tailwater is used to implement the above-mentioned aquaculture tailwater treatment process, comprising a buffer ditch, a sedimentation tank, an overflow filter dam, an aeration tank, a biological purification tank and a filler filter dam, wherein one end of the buffer ditch is provided with a tailwater inlet and the other end is connected to the sedimentation tank, the sedimentation tank is connected to the overflow filter dam, the other end of the overflow filter dam is connected to the aeration tank, the aeration tank is connected to the biological purification tank, the biological purification tank is connected to the filler filter dam, the other end of the filler filter dam is provided with a total water outlet, the total water outlet comprises a first water outlet, a second water outlet and a third water outlet, the first water outlet is connected to an external river; the second water outlet is connected to a water inlet of a breeding pond; the third water outlet is connected to the buffer ditch.

[0015] Furthermore, the filler filtration dam is composed of an iron-carbon micro-electrolysis coupled pyrite filler layer and a gravel layer, 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 mixture of particles of three raw materials: scrap iron filings, activated carbon, and pyrite. In terms of mass percentage, the iron-carbon micro-electrolysis coupled pyrite filler contains 33% to 50% scrap iron filings, 17% to 25% activated carbon, and 25% to 50% pyrite.

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

[0018] Furthermore, the scrap iron filings are pretreated before being made into iron-carbon micro-electrolysis coupled pyrite filler, and the pretreatment method is: 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, a microbial carrier is provided in the biological purification pool, and the microbial carrier is a biochemical cotton and a biological filter brush. The biological filter brush includes a skeleton and a carrier wire. The carrier wire extends outward from the skeleton to form a permeable material with water diversion channels evenly distributed inside. The biochemical cotton and the biological filter brush are arranged at intervals and evenly distributed in the biological purification pool.

[0020] Furthermore, the filter material in the overflow filter dam is composed of pebbles, zeolites and crushed stones, and the volume ratio of pebbles, zeolites and crushed stones is 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 flow is provided at the inlet end of the buffer ditch.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention adds a buffer ditch before the traditional three-pond two-dam process, and reduces the water inlet load of the three-pond two-dam through the adsorption and purification ability of aquatic plants in the ecological ditch, 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 in extreme weather. It is a treatment system that integrates physical, chemical, and biological purification methods and is suitable for a variety of aquaculture models.

[0024] 2. The filler in the filler 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 and stabilize the effluent pH, thereby providing 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 pool instead of an ecological purification pool, which greatly reduces the floor space. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 2 is a diagram of the experimental device of the present invention (top view);

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

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

[0030] Figure 5 This is a comparison chart of the effect of different fillers in the filler filter dam on the removal of nitrate nitrogen in Example 1;

[0031] Figure 6 This is a comparison of the denitrification effects of different ratios of iron-carbon micro-electrolysis coupled with pyrite filler in Example 2

[0032] Figure 7 This is a comparison chart of the effect of the buffer ditch on the denitrification effect in Example 3.

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

[0034] Fig. 9 This is a total nitrogen removal effect diagram in Example 4;

[0035] Fig.10 It is a connection relationship diagram of the aquaculture tail water treatment system of the present invention.

[0036] The numbers in the attached figure are: 1, breeding pond; 2, buffer ditch; 3, sedimentation tank; 4, overflow filter dam; 5, aeration tank; 6, biological purification tank; 7, filler filter dam; 8, total water outlet; 9, first water outlet; 10, second water outlet; 11, third water outlet. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0038] like Fig.10 As shown, the present invention provides a treatment system for aquaculture tail water, comprising a buffer ditch 2, a sedimentation tank 3, an overflow filter dam 4, an aeration tank 5, a biological purification tank 6 and a filler filter dam 7, the buffer ditch 2 is connected with the outlet of the aquaculture tail water, the buffer ditch 2 is directly connected with the sedimentation tank 3, an overflow filter dam 4 is arranged between the sedimentation tank 3 and the aeration tank 5, the aeration tank 5 is directly connected with the biological purification tank 6, and a filler filter dam 7 is arranged between the biological purification tank 6 and the total outlet 8; the aquaculture tail water passes through the buffer ditch 2, the water flow rate is controlled, the residence time of the aquaculture tail water in the buffer ditch 2 is adjusted, a small part of suspended matter and nutrient elements such as N and P are removed, and the first tail water is generated, and the first tail water is treated by three tanks and two dams and finally the tail water meets the discharge standard; the aforementioned "control of water flow rate" is achieved by pumping or controlling the gate opening, and in this embodiment, it is achieved by using the conveying speed of the water pump in the experimental device, which is arranged at the inlet end of the buffer ditch 2;

[0039] The buffer ditch 2 is paved with natural zeolite, and is planted with emergent plants and submerged plants, wherein the emergent plants are yellow iris and the submerged plants are pink-green foxtail algae, thereby utilizing the adsorption capacity of plants to purify nitrogen and phosphorus in the tail water, and at the same time, the roots of the yellow iris can play a role in reinforcing the embankment, and 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 laid in the buffer ditch 2 can prevent soil erosion and ditch collapse caused by water flow impact on the one hand, and on the other hand, it is also conducive to the attachment of microorganisms and realizes the treatment of part of the N and P elements. The emergent plants can reduce the water flow velocity and maintain water and soil, and the pink-green foxtail algae can utilize N and P in the water to grow, and the consumed N and P elements can reduce the subsequent treatment load of the three pools and two dams, and the effluent water quality of the buffer ditch 2 can be monitored, thereby reasonably regulating the hydraulic retention time in the buffer ditch 2.

[0040] The total water outlet 8 includes a first water outlet 9, a second water outlet 10 and a third water outlet 11. The first water outlet 9 is connected to an external river for discharging tail water that has been treated to meet the standards; the second water outlet 10 is connected to the water inlet of the aquaculture pond 1, and can reuse the tail water that has been treated to meet the standards, reducing the demand for external water; the third water outlet 11 is connected to the buffer ditch 2. When the treatment does not meet the standards, the tail water is returned to the buffer ditch 2 for re-treatment, and at the same time, the concentration of the aquaculture tail water in the buffer ditch 2 is diluted, which is beneficial to subsequent treatment.

[0041] The filler filtration dam 7 is composed of an iron-carbon micro-electrolysis coupled pyrite filler layer and a gravel layer. The iron-carbon micro-electrolysis coupled pyrite filler layer is located above the gravel layer, and the filling volume ratio of the iron-carbon micro-electrolysis coupled pyrite filler layer and the gravel layer is 5:1; the gravel acts as a base, mainly supporting the iron-carbon micro-electrolysis coupled pyrite filler layer, preventing the iron-carbon micro-electrolysis coupled pyrite filler layer from being covered by sludge and causing adverse effects. The denitrifying bacteria attached to the pyrite in the upstream biological purification tank 6 reduce the pH of the water body to 4-5 when removing N and P. The iron-carbon micro-electrolysis coupled pyrite filler layer can improve the pH of the water body during the sewage treatment process while filtering the water body, avoiding the pH of the tail water entering the river after the water is too low, affecting the activity of beneficial bacteria in the external environment; at the same time, the iron-carbon micro-electrolysis denitrification produces NH4 + It can also be used by denitrifying bacteria to carry out denitrification.

[0042] The mechanism of action of the iron-carbon micro-electrolysis coupled 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 denitrification: NO3 - +4Fe 0 +7H + →NH4 + +4Fe 2+ +3OH -

[0046] The iron-carbon micro-electrolysis coupled pyrite filler is composed of scrap iron, activated carbon and pyrite. In terms of mass percentage, the iron-carbon micro-electrolysis coupled pyrite filler comprises 33% to 50% scrap iron, 17% to 25% activated carbon and 25% to 50% pyrite.

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

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

[0049] The appropriate particle size is conducive to the contact between the iron-carbon micro-electrolysis coupled pyrite filler and the water flow, and will not produce too much resistance to the water flow. In the iron-carbon micro-electrolysis coupled pyrite filler, waste iron filings and pyrite will be consumed. Therefore, the three materials are made into particles separately to achieve contact with each other. It can also facilitate the subsequent replenishment of materials and avoid the water treatment effect being blocked by the particle surface covered with activated carbon that cannot be consumed after the powder mixing.

[0050] The scrap iron is pretreated before being made into iron-carbon micro-electrolysis coupled pyrite filler, and the pretreatment method is: 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 on the surface of the scrap iron, make the scrap iron fully exposed, fully contact with water, and increase the reaction rate.

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

[0052] The biological purification pool 6 is provided with a microbial carrier, which is a biochemical cotton and a biological filter brush. The biological filter brush includes a skeleton and a carrier wire. The carrier wire extends outward from the skeleton to form a water-permeable material with water diversion channels evenly distributed inside. The biochemical cotton and the biological filter brush are arranged at intervals and are evenly distributed in the biological purification pool 6.

[0053] The biochemical cotton has good air permeability and high mechanical strength. The gaps in the biochemical cotton can be used for microorganisms to attach and grow, and it also plays a filtering role. The iron wire (steel wire) is used as a skeleton, and the fine PE hair filaments extending outward are used as carrier filaments. The brush is placed vertically in the purification tank. The fine PE hair filaments can be used for microorganisms to attach and grow. The biochemical cotton and the biological filtration brush are arranged at intervals and are evenly distributed in the biological purification tank 6. They occupy a larger volume as much as possible while satisfying the premise of sufficient drainage cross-section, providing a basis for microbial attachment. After purification by microorganisms, the concentrations of nitrate nitrogen and total phosphorus in the water are reduced.

[0054] The filter material in the overflow filter dam 4 is composed of pebbles, zeolites, and crushed stones, and the volume ratio of pebbles, zeolites, and crushed stones is 1:1:1; through the interception effect of the filter material, the concentration of suspended matter in the water can be effectively reduced, and the turbidity of the tail water can be reduced.

[0055] In specific implementation, the treatment process of aquaculture tail water of the present invention comprises the following steps:

[0056] S1: The tailwater of aquaculture enters the buffer ditch 2 from the tailwater outlet. The buffer ditch 2 has a certain depth and width. By controlling the water flow rate, the residence time of the tailwater in the buffer ditch 2 is prolonged, and the sedimentation rate of suspended matter in the tailwater is increased; the emergent plant yellow iris is planted on the bank of the buffer ditch 2, and the submerged plant pink green foxtail algae is planted in the ditch. The planting area accounts for 30% of the water surface, which can effectively reduce the nitrogen and phosphorus concentrations in the water, reduce the pollutant load of the three pools and two dams, monitor the effluent water quality of the buffer ditch 2, and thus reasonably regulate the hydraulic retention time in the buffer ditch 2;

[0057] S2: The tail water treated by the buffer ditch 2 then enters the sedimentation tank 3, where the submerged plant Myriophyllum glabra is planted to slow down the flow rate of the incoming water and effectively settle the suspended matter. At the same time, the submerged plant Myriophyllum glabra also plays a role in absorbing nitrogen and phosphorus.

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

[0059] S4: the tail water treated by the overflow filter dam 4 enters the aeration tank 5, and the concentrations of COD and ammonia nitrogen in the tail water are reduced by aeration oxidation, volatilization and decomposition;

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

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

[0062] Experimental Materials:

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

[0064] The device is placed in the warehouse of the breeding pond of Zhengzhou Wanshui Qianshan Agriculture Co., Ltd., and the breeding tail water is directly extracted from the breeding pond.

[0065] Embodiment 1:

[0066] By using only the filling dam, we used pyrite layer and gravel layer as fillers, iron-carbon micro-electrolysis material layer (the mass ratio of scrap iron to activated carbon was 1:1) and gravel layer as fillers, and iron-carbon micro-electrolysis coupled with pyrite filler layer (the mass ratio of scrap iron, activated carbon to pyrite was 1:1:2) and gravel layer as fillers, and other conditions remained the same. We tested the effect of iron-carbon micro-electrolysis coupled with pyrite filler in stabilizing water pH and removing nitrogen compared with using pyrite filler and iron-carbon micro-electrolysis material alone. The results are shown in the figure. Figure 3 , Figure 4 and Figure 5 As shown: It can be clearly seen from the figure that compared with using pyrite filler or iron-carbon micro-electrolysis material alone, iron-carbon micro-electrolysis coupled with pyrite filler shows better effect in stabilizing the pH value of water body, and also has a significant improvement in the removal rate of total nitrogen and nitrate nitrogen.

[0067] Embodiment 2:

[0068] Using the composite three-tank two-dam treatment system, the iron scraps, activated carbon and pyrite in the iron-carbon micro-electrolysis coupled pyrite filler in the filler filter dam 7 were prepared with iron-carbon micro-electrolysis coupled pyrite filler in different mass ratios, and applied to the composite three-tank two-dam treatment system. Other conditions were the same, and the denitrification effect of iron-carbon micro-electrolysis coupled pyrite filler with different preparation ratios was tested; the results are as follows Figure 6As shown in the figure, the experimental group with a ratio of 2:1:1 for scrap iron filings, activated carbon and pyrite has the strongest denitrification effect, but the stability is insufficient and the denitrification effect fluctuates too much; the experimental group with a ratio of 2:1:2 for scrap iron filings, activated carbon and pyrite has a higher treatment efficiency and a longer service life, and has good treatment stability. The denitrification efficiency of the other two experimental groups is relatively low.

[0069] Embodiment three:

[0070] The buffer ditch 2 is not set, but the water is directly fed from the sedimentation tank 3. The effect of the buffer ditch 2 on the denitrification of the present invention is tested. The test results are as follows: Figure 7 As shown, it can be seen that the buffer ditch 2 can effectively reduce the denitrification load of the subsequent three pools and two dams and ensure the water treatment effect.

[0071] In order to explore whether the buffer ditch 2 has an effect on the denitrification of the present invention, the device removed the buffer ditch 2 on the 11th day and directly fed water from the sedimentation tank 3. The other operating conditions remained unchanged. Figure 7 The results shown in the figure show that after the buffer ditch 2 is not set, the removal rate of total nitrogen in the effluent water decreases significantly, and the average removal rate is 39.5%. Therefore, it can be explained that the existence of the buffer ditch 2 can improve the total nitrogen removal efficiency of the present invention.

[0072] Embodiment 4:

[0073] A composite three-tank two-dam treatment system was used, with iron-carbon micro-electrolysis coupled with pyrite in the filler filter dam 7. The mass ratio of waste iron filings, activated carbon and pyrite in the filler was 2:1:2. The aquaculture tailwater was treated comprehensively with an HRT of 24h. The purification effect of aquaculture tailwater within 20 days was as follows: Figure 8 and Fig. 9 As shown, the composite three-pond and two-dam system of the embodiment of the present invention can achieve long-term compliance with ecological treatment standards for aquaculture effluent under low HRT. The setting of the buffer ditch 2 can alleviate the pollutant load of the three-pond and two-dam system. Its super strong water storage capacity can cope with the impact of floods on the three-pond and 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 rates of total nitrogen and nitrate nitrogen, and realizes the composite of processes and fillers.

[0074] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

Claims

1. A process for treating tail water from aquaculture, characterized in that: The following steps are involved: Step S1: the tail water generated by aquaculture enters the buffer mechanism through the tail water outlet, where it is buffered and initially settled to generate the first tail water; Step S2: the first tail water obtained in step S1 enters the sedimentation mechanism, and the suspended matter is removed during the sedimentation process to form the second tail water; Step S3: The second tail water obtained in step S2 is filtered through a filtering mechanism to filter out large particles therein, thereby effectively reducing the concentration of suspended matter in the water and the turbidity of the tail water, thereby obtaining third tail water; Step S4: the third tail water obtained in step S3 enters the aeration mechanism, and is oxidized and decomposed into organic pollutants in the water through the aeration process to produce fourth tail water; Step S5: the fourth tail water obtained in step S4 enters the biological purification mechanism, and under the action of microorganisms, most of the COD, total nitrogen and total phosphorus indicators are reduced to form the fifth tail water; Step S6: The fifth tail water obtained in step S5 is treated by a packing mechanism, and the electrochemical and microbial synergistic effect of iron-carbon micro-electrolysis and pyrite system is utilized to further reduce the concentration of total nitrogen and total phosphorus in the water to obtain the final effluent.

2. The aquaculture tailwater 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 filtration dam (4), the aeration mechanism is an aeration tank (5), the biological purification mechanism is a biological purification tank (6), and the filler mechanism is a filler filtration dam (7).

3. A system for treating aquaculture tail water, which realizes the aquaculture tail water treatment process according to any one of claims 1 to 2, characterized in that: The invention comprises a buffer ditch (2), a sedimentation tank (3), an overflow filter dam (4), an aeration tank (5), a biological purification tank (6) and a filler 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 filler filter dam (7); the other end of the filler filter dam (7) is provided with a total water outlet (8); the total water outlet (8) comprises a first water outlet (9), a second water outlet (10) and a third water outlet (11); the first water outlet (9) is connected to an external river; the second water outlet (10) is connected to a water inlet of a breeding pond; the third water outlet (11) is connected to the buffer ditch (2).

4. The aquaculture tail water treatment system according to claim 3, characterized in that: The filler filtration dam (7) 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.

5. The aquaculture tail water treatment system according to claim 4, characterized in that: The iron-carbon micro-electrolysis coupled pyrite filler layer is composed of a mixture of particles of three raw materials: scrap iron, activated carbon, and pyrite. In terms of mass percentage, the iron-carbon micro-electrolysis coupled pyrite filler contains 33% to 50% scrap iron, 17% to 25% activated carbon, and 25% to 50% pyrite.

6. The aquaculture tail water treatment system according to claim 5, characterized in that: The particle size of the gravel particles in the gravel layer is 20mm-30mm, the particle size of the waste iron particles in the iron-carbon micro-electrolysis coupled pyrite filler layer is 6-8mm, the particle size of the activated carbon particles is 3-5mm, and the particle size of the pyrite particles is 10-12mm.

7. The aquaculture tail water treatment system according to claim 5, characterized in that: The scrap iron is pretreated before being made into iron-carbon micro-electrolysis coupled pyrite filler. The pretreatment method is: 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.

8. The aquaculture tail water treatment system according to claim 3, characterized in that: The biological purification pool (6) is provided with a microbial carrier, which is a biochemical cotton and a biological filter brush. The biological filter brush comprises a skeleton and a carrier wire. The carrier wire extends outward from the skeleton to form a water-permeable material with water diversion channels evenly distributed inside. The biochemical cotton and the biological filter brush are arranged at intervals and evenly distributed in the biological purification pool (6).

9. The aquaculture tail water treatment system according to claim 3, characterized in that: The filter material in the overflow filter dam (4) is composed of pebbles, zeolites and crushed stones, and the volume ratio of the pebbles, zeolites and crushed stones is 1:1:

1.

10. The aquaculture tail water 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, and 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); and a gate or a water pump for regulating flow is provided at the inlet end of the buffer ditch (2).

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