A nitrogen and phosphorus adsorption unit, device, treatment system and method for fish farming wastewater.

Abstract

A nitrogen and phosphorus adsorption unit, device, treatment system, and method for fish farming wastewater belong to the field of wastewater purification in aquaculture. It includes two vertical pipes with open tops and perforated surfaces. Between the two vertical pipes, several support pipes with perforated surfaces are distributed along the vertical direction. Each support pipe has two ends connected to the interior of the vertical pipe and contains several adsorption balls connected in series by connecting lines. Each adsorption ball is filled with bentonite and has several perforated surfaces. This invention achieves rapid replacement of the adsorption material by filling the adsorption balls with bentonite and using connecting lines to connect them. The perforations on the support pipes and the perforations on the adsorption balls allow for seepage contact between the wastewater and the bentonite, effectively preventing bentonite loss. Furthermore, the connecting lines allow for the removal of adsorption balls from the support pipes and replacement with new ones.

Description

Technical Field

[0001] This invention relates to the field of wastewater purification in aquaculture, specifically to a nitrogen and phosphorus adsorption unit, device, treatment system, and method for fish farming wastewater. Background Technology

[0002] With the large-scale development of my country's freshwater fish farming industry, environmental problems caused by the discharge of aquaculture wastewater have become increasingly prominent. The accumulation of uneaten feed and feces during the farming process leads to excessively high concentrations of nitrogen and phosphorus in the wastewater. Direct discharge of these wastewaters can cause eutrophication of natural water bodies, induce red tides and algal blooms, disrupt the ecological balance, increase the risk of aquatic diseases, and hinder the sustainable development of the industry.

[0003] Traditional nitrogen and phosphorus treatment technologies for wastewater have significant drawbacks. For example, electrolysis methods require large investments and consume a lot of energy, and are prone to generating secondary pollutants such as chlorinated organic compounds; phytoremediation methods are dependent on climate conditions, have long treatment cycles, and are difficult to adapt to the rapid treatment needs of high-concentration wastewater; conventional adsorption materials such as activated carbon and zeolite have limited adsorption capacity and high regeneration costs, making large-scale application impossible. Therefore, developing low-cost, high-efficiency, and environmentally friendly nitrogen and phosphorus treatment technologies for wastewater has become an urgent need for the industry.

[0004] Bentonite, a natural clay mineral, is mainly composed of montmorillonite. It has a layered crystal structure, is highly hydrophilic, and easily swells upon contact with water, with a specific surface area of ​​up to 700-800 m². 2 With a high cation exchange capacity of 100-150 meq / 100g, bentonite can efficiently capture nitrogen and phosphorus pollutants through physical adsorption, chemical adsorption, and ion exchange. Furthermore, bentonite is abundant, has a low extraction cost (approximately 1 / 5 that of activated carbon), is non-toxic and harmless, and can be recycled after adsorption saturation, giving it significant advantages as an adsorption material for wastewater.

[0005] However, when bentonite is used as an adsorbent material, it is often piled with materials such as sand and gravel to form a seepage adsorption wall, allowing water to seep through the wall for adsorption and purification. However, existing adsorption walls have the following problems: 1) Bentonite particles are very small. When dispersed or in a fluid state, bentonite particles can flow within the pores of sand and gravel particles. This causes the bentonite to be unable to be fixed inside the sand particles and to seep out with the wastewater, resulting in adsorption failure. If the bentonite concentration is increased, there will be molecular attraction, and flocculent matter will form between the particles during the water flow. Gradually, the pores of the sand and gravel particles will be blocked by viscosity, which will also cause the adsorption function to fail. 2) The adsorption capacity of the bentonite in the adsorption wall is limited. When the adsorption limit is reached, the bentonite in the adsorption wall needs to be replaced. This often requires excavation and destruction of the original structure, causing great damage and impact on the original treatment facilities and the environment. Summary of the Invention

[0006] The purpose of this invention is to provide a nitrogen and phosphorus adsorption unit, device, treatment system and method for fish farming wastewater, which uses bentonite as an adsorption material to efficiently remove nitrogen and phosphorus from the wastewater and enables rapid replacement of the bentonite material during the adsorption process.

[0007] The technical solution adopted by the present invention to achieve the above-mentioned technical objectives is as follows: a nitrogen and phosphorus adsorption unit for fish farming tailwater includes two vertical pipes with open tops and through holes distributed on the surface, and several support pipes with through holes distributed on the surface are distributed between the two vertical pipes along their height direction. Both ends of each support pipe are connected to the inside of the vertical pipe, and several adsorption balls are distributed inside. These adsorption balls are connected in series by connecting lines, and both ends of the connecting lines extend out of the top opening of the vertical pipe. Each adsorption ball is filled with bentonite and has several permeable holes distributed on its surface.

[0008] A nitrogen and phosphorus adsorption device for fish farming wastewater includes a front protective filter layer and a rear support filter layer arranged sequentially along the flow direction of the wastewater, forming a main adsorption zone. The main adsorption zone is filled with an adsorption material formed by mixing bentonite and coarse sand in a mass ratio of 1:2-9. Multiple sets of the above-mentioned nitrogen and phosphorus adsorption units are distributed in the main adsorption zone, and the support tubes in each set of nitrogen and phosphorus adsorption units are arranged along the water head flow network in the main adsorption zone.

[0009] As another optimized solution for the nitrogen and phosphorus adsorption device in the aforementioned fish farming wastewater, the particle size of the bentonite in the main adsorption zone does not exceed 0.01 mm, and the particle size of the coarse sand is 2-5 mm. The gradation design method in the main adsorption zone is as follows: S1. Given a preset permeability coefficient k and hydraulic gradient i, where k = 1.5 - 2.0 and i < 0.5, calculate d10 using the Hassen formula. Hassen's formula is ; In the formula, C is an empirical coefficient, with a value of 100-150; n is the porosity, n=V v / V×100%, V v V is the pore volume, and V is the total volume of the sample. v V was obtained through geotechnical tests; S2, d obtained from step S1 10 Construct a continuous and smooth gradation curve, and then obtain d from this gradation curve. 30 and d 60 According to d 30 and d 60 Calculate the non-uniformity coefficient C at this time. u and curvature coefficient C c ; Inhomogeneity coefficient C u The calculation formula is ; curvature coefficient C c The calculation formula is ; In the formula, d 60 For particles that account for 60% of the weight of the sieve, d 30 The particle size that accounts for 30% of the weight of the sieved particles; S3. Determine the non-uniformity coefficient C calculated in step S2. u Does it satisfy C? u <5, and curvature coefficient C c Does it satisfy C? c =1-3, if satisfied, proceed to step S4; if not satisfied, return to step S1; S4. Based on the permeability coefficient k and hydraulic gradient i preset in step S1, Darcy's law is applied. Calculate the seepage velocity v, and then calculate the Reynolds number Re using the Reynolds number formula; The Reynolds number formula is ; In the formula, Fluid density, unit: kg / m³ 3 v represents the seepage velocity, in m / s; d 10 The d obtained in step S1 10 μ is the dynamic viscosity of the fluid, measured in Pa·s or kg / (m·s); S5. Determine whether Re calculated in step S4 is less than 10. If it is less than 10, proceed to step S6. If it is greater than or equal to 10, return to step S1. S6. Based on the gradation curve constructed in step S2, construct an indoor model using coarse sand with a particle size of 2-5 mm and bentonite with a particle size of no more than 0.01 mm, and conduct a permeability test. Determine the actual permeability coefficient k through the permeability test. If the actual permeability coefficient k satisfies k=1.5-2.0, proceed to step S7; otherwise, return to step S1. S7. Use the indoor model constructed in step S6 to conduct a seepage stability test to determine whether the risk of piping and soil erosion meets the standards. If it does not meet the standards, return to step S1. If it meets the standards, the gradation curve constructed in step S2 is the gradation distribution in the main adsorption zone.

[0010] As another optimized solution for the above-mentioned nitrogen and phosphorus adsorption device for fish farming wastewater, an impermeable layer is provided at the bottom of the front protective filter layer, the main adsorption zone and the rear support filter layer.

[0011] As another optimized solution for the above-mentioned nitrogen and phosphorus adsorption device for fish farming wastewater, a backwashing pipe is provided in the front protective filter layer.

[0012] As another optimized solution for the above-mentioned nitrogen and phosphorus adsorption device for fish farming wastewater, the main adsorption zone is equipped with a grouting pipe for injecting bentonite slurry into the main adsorption zone and a grouting pipe for discharging bentonite slurry.

[0013] A fish farming wastewater treatment system includes a wastewater collection tank located on one side of a fishpond, wherein the outlet of the wastewater collection tank is equipped with the aforementioned nitrogen and phosphorus adsorption device.

[0014] As an optimized solution for the above-mentioned fish farming wastewater treatment system, the wastewater collection tank is equipped with a water pump that draws wastewater from the fishpond and a water level sensor that monitors the water level in the wastewater collection tank. The wastewater discharged from the nitrogen and phosphorus adsorption device enters the sedimentation tank for settling.

[0015] As another optimized solution for the above-mentioned fish farming wastewater treatment system, the pre-protective filter layer and the post-support filter layer of the nitrogen and phosphorus adsorption device are respectively equipped with a pre-nitrogen and phosphorus concentration real-time detection unit and a post-nitrogen and phosphorus concentration real-time detection unit.

[0016] The method for treating fish farming wastewater using the above-mentioned wastewater treatment system includes the following steps: 1) Set up a tailwater collection pond on one side of the fishpond. The outlet of the tailwater collection pond is connected to the sedimentation pond. In the outlet of the tailwater collection pond, according to the direction of tailwater flow, first construct a front protective filter layer with coarse sand with a particle size of 2-5mm, and then construct a rear support filter layer with gravel with a particle size of 5-10mm. The space between the two forms the main adsorption zone. 2) Calculate the distribution of the head flow network in the main adsorption zone according to the existing head flow network calculation method, and then plan the layout of the support pipes in advance according to the calculated head flow network distribution to form the layout design drawing of the support pipes in the main adsorption zone. 3) Use a mixture of bentonite with a particle size not exceeding 0.01 mm and coarse sand with a particle size of 2-5 mm to fill the main adsorption zone. During the filling process, install the support tube for filling the adsorption balls according to the layout design diagram formed in step 2), and expose the end of the vertical tube in the nitrogen and phosphorus adsorption unit to the surface of the main adsorption zone. 4) Inject tailwater into the tailwater collection tank, allowing the tailwater to permeate through the pre-protective filter layer, main adsorption zone, and post-support filter layer into the settling tank. 5) Use the two vertical pipes in each nitrogen and phosphorus adsorption unit as grouting pipe and grout discharge pipe respectively. Based on the ammonia nitrogen and phosphorus concentration data monitored in real time by the real-time nitrogen and phosphorus concentration detection unit, adjust the proportion of bentonite in the main adsorption zone through the grouting pipe and grout discharge pipe. 6) Monitor the ammonia nitrogen and phosphorus concentration data of the real-time nitrogen and phosphorus concentration detection unit in real time. If the concentration reaches the set standard, inject bentonite slurry with a solid-liquid ratio of 1:3 into the main adsorption zone through the grouting pipe at a pressure of 0.3-0.5MPa. The injection volume is 1.1-1.3 times the volume of the main adsorption zone, so as to push the bentonite slurry that has completed adsorption out of the slurry discharge pipe.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1) The tailwater nitrogen and phosphorus adsorption unit of the present invention loads bentonite into adsorption balls with permeable holes distributed on the surface, and uses connecting wires to string the adsorption balls together and insert them into a support tube. The through holes on the support tube and the permeable holes on the surface of the adsorption balls realize the seepage contact between the tailwater and the bentonite. The support tube and the adsorption balls can effectively prevent the loss of bentonite. After a period of use, the adsorption balls in the support tube can be pulled out using the connecting wires and replaced with new adsorption balls, realizing the rapid replacement of adsorption materials. 2) In the tailwater nitrogen and phosphorus adsorption device of the present invention, a main adsorption zone is formed by a front protective filter layer and a rear support filter layer. The main adsorption zone is filled with an adsorption material formed by a mixture of bentonite and coarse sand. At the same time, multiple sets of nitrogen and phosphorus adsorption units are distributed in the main adsorption zone. The support pipes in each set of nitrogen and phosphorus adsorption units are arranged along the water head flow network in the main adsorption zone. This arrangement of support pipes along the water head flow network is based on the pore water seepage flow line inside the main adsorption zone. This avoids the problem of uniform distribution and low concentration of bentonite, which makes it easy to be washed away by water, and also avoids the problem of bentonite being localized. The problem of high concentrations forming a water-blocking layer can cause filtration failure. However, the adsorption ball design inside the support tube ensures that the bentonite is evenly distributed and fully absorbs nitrogen and phosphorus without causing excessive bentonite to escape and create a water barrier. It also ensures that the bentonite is fully saturated and recyclable. At the same time, this patented design arranges and designs the adsorption balls according to the water head flow network, so that the water flows into the support tube along the optimal route under seepage pressure. This maximizes the use of the seepage channel in the main adsorption zone and the contact surface between the main adsorption zone and the support tube, effectively improving the adsorption efficiency of bentonite for nitrogen and phosphorus in the tailwater. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the nitrogen and phosphorus adsorption unit in the tailwater of the present invention; Figure 2 This is a schematic diagram showing the arrangement of adsorption balls inside the support tube in the nitrogen and phosphorus adsorption unit of the tailwater. Figure 3 This is a schematic diagram of the adsorption sphere structure; Figure 4 This is a schematic diagram of the nitrogen and phosphorus adsorption device for tailwater of the present invention; Figure 5 This is a schematic diagram of the wastewater treatment system of the present invention; Attached reference numerals: 1. Vertical pipe, 101. Support pipe, 102. Connecting line, 103. Through hole, 2. Adsorption ball, 201. Hemispherical shell, 202. Water seepage hole, 203. Hook, 3. Main adsorption zone, 301. Impermeable layer, 302. Grouting pipe, 303. Grout discharge pipe, 4. Front protective filter layer, 401. Front nitrogen and phosphorus concentration real-time detection unit, 402. Backwash pipe, 5. Rear support filter layer, 501. Rear nitrogen and phosphorus concentration real-time detection unit, 6. Tailwater collection tank, 601. Water pump, 602. Water level sensor, 7. Sedimentation tank, 8. Fish pond. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Parts not explained in the following embodiments of the present invention are all considered to be prior art known or should be known by those skilled in the art. Example 1

[0020] A nitrogen and phosphorus adsorption unit for fish farming wastewater, such as Figure 1 As shown, the device includes two vertical pipes 1 with open tops and through holes distributed on their surfaces. The bottom of the vertical pipes 1 can be open or closed. The material of the vertical pipes 1 can be PVC plastic pipe, and the shape can be round or square. The pipe diameter is generally 50±5mm. Between the two vertical pipes 1, several support pipes 101 with through holes 103 distributed on their surfaces are distributed along their height. The diameter of the support pipes 101 is generally 10mm. On the opposite surfaces of the two vertical pipes 1, multiple through holes are evenly distributed along the height. The two ends of the support pipes 101 are fixed in the through holes, and the interior of the support pipes 1 is connected to the interior of the vertical pipes 1. The material of the support pipes 101 is metal pipe or PVC pipe with a certain degree of hardness. Its surface is distributed with through holes for water seepage. The spacing between the support pipes 101 is generally 5cm. Both ends of each support pipe 101 are connected to the interior of the vertical pipe 1, and several adsorption balls 2 are distributed inside. Figure 2 As shown, the adsorption ball 2 is spherical and hollow inside, with a diameter slightly smaller than the inner diameter of the support tube 101, typically 9 mm, allowing it to move within the support tube 101. These adsorption balls 2 are connected in series by connecting lines 102, which are made of metal wire to ensure sufficient strength. That is, an adsorption ball 2 is installed at intervals along the connecting lines 102, and both ends of the connecting lines 102 extend through the top opening of the vertical tube 1. The purpose is to allow the adsorption balls 2 inside the support tube 101 to be pulled out and replaced by pulling the connecting lines 102. Each adsorption ball 2 is filled with bentonite, which can be ordinary bentonite or modified bentonite. Several seepage holes 202 are distributed on the surface. The shape of the seepage holes 202 can be round, square, strip-shaped, or even irregularly shaped. Generally, they are round or slit-shaped and evenly distributed. The openings cannot be too large, as this will lead to the loss of the internal bentonite, nor can they be too small, as this will easily cause blockage and affect the seepage efficiency.

[0021] In this embodiment, the adsorption sphere 2 is formed by splicing together two hollow hemispherical shells 201, as shown below. Figure 3 As shown, the two hemispherical shells 201 are connected by threads, and the surface of the adsorption ball 2 is provided with hooks 203 that connect to the connecting line 102. The number of hooks 203 can be one or two. The hooks 203 are generally semi-circular ring structures. At the same time, a hook-shaped structure or other similar structure is provided on the connecting line 102 to achieve a detachable connection between the connecting line 102 and the adsorption ball 2. Example 2

[0022] A device for adsorbing nitrogen and phosphorus in fish farming wastewater, such as Figure 4 As shown, the system includes a front protective filter layer 4 and a rear support filter layer 5 arranged sequentially along the tailwater flow direction. In practice, measures such as walls and ditches are used to constrain the tailwater flow in a certain direction. The front protective filter layer 4 and the rear support filter layer 5 are arranged sequentially within the tailwater flow channel. Both have a certain height, forming a partition-like structure that blocks the tailwater flow, and they are separated by a distance, forming a main adsorption zone 3. The front protective filter layer 4 is composed of coarse sand with a particle size of 2-5 mm, and its thickness is generally 15±2 cm along the tailwater flow direction. The rear support filter layer 5 is composed of gravel with a particle size of 5-10 mm, and its thickness is also along the tailwater flow direction. Its thickness is generally 20±2cm. The main adsorption zone 3 is filled with an adsorption material formed by mixing bentonite and coarse sand in a mass ratio of 1:2-9. The particle size of the bentonite does not exceed 0.01mm, and the particle size of the coarse sand is generally 2-5mm. In practice, the adsorption material fills the area between the front protective filter layer 4 and the rear support filter layer 5 to form the main adsorption zone 3. Along the flow direction of the tailwater, the thickness of the main adsorption zone 3 is generally 50-80cm. Multiple sets of nitrogen and phosphorus adsorption units in Example 1 are distributed in the main adsorption zone 3. In practice, the nitrogen and phosphorus adsorption units are buried in the main adsorption zone 3 as a skeleton. The support pipe 101 in each set of nitrogen and phosphorus adsorption units is arranged along the head flow network in the main adsorption zone 3.

[0023] In this embodiment, the gradation design method within the main adsorption region is as follows: S1. Given a preset permeability coefficient k and hydraulic gradient i, where k = 1.5 - 2.0 and i < 0.5, calculate d10 using the Hassen formula. Hassen's formula is ; In the formula, C is an empirical coefficient, with a value of 100-150; n is the porosity, n=V v / V×100%, V v V is the pore volume, and V is the total volume of the sample. v V was obtained through geotechnical tests; S2, d obtained from step S1 10 Construct a continuous and smooth gradation curve, and then obtain d from this gradation curve. 30 and d 60 According to d 30 and d 60 Calculate the non-uniformity coefficient C at this time. u and curvature coefficient C c ; Inhomogeneity coefficient C u The calculation formula is ; curvature coefficient Cc The calculation formula is ; In the formula, d 60 For particles that account for 60% of the weight of the sieve, d 30 The particle size that accounts for 30% of the weight of the sieved particles; S3. Determine the non-uniformity coefficient C calculated in step S2. u Does it satisfy C? u <5, and curvature coefficient C c Does it satisfy C? c =1-3, if satisfied, proceed to step S4; if not satisfied, return to step S1; S4. Based on the permeability coefficient k and hydraulic gradient i preset in step S1, Darcy's law is applied. Calculate the seepage velocity v, and then calculate the Reynolds number Re using the Reynolds number formula; The Reynolds number formula is ; In the formula, Fluid density, unit: kg / m³ 3 v represents the seepage velocity, in m / s; d 10 The d obtained in step S1 10 μ is the dynamic viscosity of the fluid, measured in Pa·s or kg / (m·s); S5. Determine whether Re calculated in step S4 is less than 10. If it is less than 10, proceed to step S6. If it is greater than or equal to 10, return to step S1. S6. Based on the gradation curve constructed in step S2, construct an indoor model using coarse sand with a particle size of 2-5 mm and bentonite with a particle size of no more than 0.01 mm, and conduct a permeability test. Determine the actual permeability coefficient k through the permeability test. If the actual permeability coefficient k satisfies k=1.5-2.0, proceed to step S7; otherwise, return to step S1. S7. Use the indoor model constructed in step S6 to conduct a seepage stability test to determine whether the risk of piping and soil erosion meets the standards. If it does not meet the standards, return to step S1. If it meets the standards, the gradation curve constructed in step S2 is the gradation distribution in the main adsorption zone.

[0024] In this embodiment, a seepage-proof layer 301 is provided at the bottom of the front protective filter layer 4, the main adsorption zone 3, and the rear support filter layer 5. In practice, before setting the front protective filter layer 4, the main adsorption zone 3, and the rear support filter layer 5, it is necessary to lay seepage-proof materials, such as seepage-proof cloth, on the ground to form the seepage-proof layer 301. Then, the front protective filter layer 4, the main adsorption zone 3, and the rear support filter layer 5 are set on the seepage-proof layer to effectively prevent tailwater from seeping into the groundwater.

[0025] In this embodiment, a backwash pipe 402 is provided inside the front protective filter layer 4. The backwash pipe 402 is a hollow tubular component with through holes distributed on its surface. Its bottom end is inserted into the lower part of the front protective filter layer 4, and its top end is exposed above the top of the front protective filter layer 4. When the equipment is shut down for repair and maintenance after a period of operation, clean water is introduced into the front protective filter layer 4 through the backwash pipe 402 to flush and repair the entire device. The backwashing uses clean water to flush the front protective filter layer 4 from top to bottom, with a flushing flow rate of 3-5 m³ / h. 3 / h, rinsing time 15-20min, rinsing wastewater is retreated before being returned to the front protective filter layer 4; In this embodiment, the main adsorption zone 3 is equipped with a grouting pipe 302 for injecting bentonite slurry into the main adsorption zone 3 and a grouting pipe 303 for discharging bentonite slurry. Both the grouting pipe 302 and the grouting pipe 303 are tubular components with open tops and through holes distributed on their surfaces. There are generally multiple grouting pipes 302 and 303, spaced apart along the width of the main adsorption zone 3. The purpose is to re-inject new bentonite into the main adsorption zone 3 after the bentonite in the main adsorption zone 3 has adsorbed sufficient nitrogen and phosphorus, replacing the old bentonite that has completed adsorption. In practice, the grouting pipe 302... 2 and the grout discharge pipe 303 can be replaced by two vertical pipes 1 in the nitrogen and phosphorus adsorption unit. That is, any two vertical pipes 1 in the nitrogen and phosphorus adsorption unit, one of which is used as the grout injection pipe 302 and the other as the grout discharge pipe 303. The grout injection pipes 302 are evenly distributed, with a spacing of 1.5±0.1m and a pipe diameter of 50±5mm. The grouting pressure can be adjusted within the range of 0.3-0.5MPa. The grout discharge pipes 303 and grout injection pipes 302 are arranged alternately. The spacing between the grout discharge pipes 303 is 2±0.1m and the pipe diameter is 60±5mm. The outlet of the grout discharge pipe 303 is connected to the mud collection tank. Example 3

[0026] A fish farming wastewater treatment system, such as Figure 5 As shown, it includes a tailwater collection pond 6 set on one side of the fishpond 8. The tailwater collection pond 6 is a dug pond with arbitrary shape and a drainage channel as the outlet. The outlet of the tailwater collection pond 6 is equipped with the nitrogen and phosphorus adsorption device in Example 2.

[0027] In this embodiment, the tailwater collection tank 6 is equipped with a water pump 601 that draws tailwater from the fishpond 8 and a water level sensor 602 that monitors the water level in the tailwater collection tank 6. The water pump 601 can be an existing water pump. Generally, two water level sensors 602 are used and are set at different heights on the side wall of the tailwater collection tank 6. When the tailwater level in the tailwater collection tank 6 is lower than the water level sensor at the lower position, the water pump 601 is started to pump tailwater into the tailwater collection tank 6. When the water level reaches the water level sensor at the higher position, the water pump 601 stops pumping water. The tailwater discharged from the nitrogen and phosphorus adsorption device enters the sedimentation tank 7 for settling. The sedimentation tank 7 is used for the self-settling of the tailwater after adsorbing nitrogen and phosphorus to remove large particulate impurities contained therein. In this embodiment, the front protective filter layer 4 and the rear support filter layer 5 of the nitrogen and phosphorus adsorption device are respectively provided with a front nitrogen and phosphorus concentration real-time detection unit 401 and a rear nitrogen and phosphorus concentration real-time detection unit 501. The nitrogen and phosphorus concentration real-time detection unit is existing technology. Its purpose is to monitor the concentration of nitrogen and phosphorus in the water before and after the effluent treatment, so as to determine the treatment effect of the nitrogen and phosphorus adsorption device and whether the bentonite needs to be replaced. The real-time nitrogen and phosphorus concentration detection unit includes an ammonia nitrogen sensor, a total phosphorus sensor, a data acquisition terminal, a wireless transmission module, and a control platform. The sensor accuracy is ≤0.01mg / L, the data acquisition frequency is ≥1 time / 10min, and the control platform can set nitrogen and phosphorus concentration warning thresholds and trigger linkage commands. Example 4

[0028] The method for treating fish farming wastewater using the wastewater treatment system of Example 3 includes the following steps: 1) Set up a tailwater collection pond 6 on one side of the fishpond 8. The outlet of the tailwater collection pond 6 is connected to the sedimentation pond 7. In the outlet of the tailwater collection pond 6, according to the direction of tailwater flow, first construct a front protective filter layer 4 with coarse sand with a particle size of 2-5mm, and then construct a rear support filter layer 5 with gravel with a particle size of 5-10mm. The space between the two forms the main adsorption zone 3. 2) Calculate the distribution of the head flow network in the main adsorption zone 3 according to the existing head flow network calculation method, and then plan the layout of the support pipe 101 in advance according to the calculated head flow network distribution to form the layout design drawing of the support pipe 101 in the main adsorption zone 3. 3) Use a mixture of bentonite with a particle size not exceeding 0.01 mm and coarse sand with a particle size of 2-5 mm to fill the main adsorption zone 3. During the filling process, install the support tube 101 for filling the adsorption ball 2 according to the layout design diagram formed in step 2), and expose the end of the vertical tube 1 in the nitrogen and phosphorus adsorption unit to the surface of the main adsorption zone 3. 4) Inject tailwater into tailwater collection tank 6, so that tailwater can pass through the front protective filter layer 4, the main adsorption zone 3 and the rear support filter layer 5 by permeation and enter the sedimentation tank 7; install a permeability monitoring probe in the main adsorption zone 3 to provide real-time feedback on the permeation rate in the main adsorption zone 3, and control the permeation rate within the range of 0.5-1.0 m / d. 5) The two vertical pipes 1 in each nitrogen and phosphorus adsorption unit are respectively used as grouting pipes 302 and grout discharge pipes 303. Based on the ammonia nitrogen and phosphorus concentration data monitored in real time by the pre-nitrogen and phosphorus concentration real-time detection unit 401, the proportion of bentonite in the main adsorption zone 3 is adjusted through grouting pipes 302 and grout discharge pipes 303. The specific operation is as follows: If ammonia nitrogen ≥ 5 mg / L and total phosphorus ≥ 1 mg / L, the mass ratio of bentonite to sand and gravel in the main adsorption zone 3 is set to 1:2; if ammonia nitrogen 3-5 mg / L and total phosphorus 0.5-1 mg / L, the ratio is set to 1:5; if ammonia nitrogen < 3 mg / L and total phosphorus < 0.5 mg / L, the ratio is set to 1:9. 6) Monitor the ammonia nitrogen and phosphorus concentration data of the real-time nitrogen and phosphorus concentration detection unit 501 in real time. If the concentration reaches the set standard, inject bentonite slurry with a solid-liquid ratio of 1:3 into the main adsorption zone 3 through the grouting pipe 302 at a pressure of 0.3-0.5 MPa. The injection volume should be 1.1-1.3 times the volume of the main adsorption zone 3. This will push the bentonite slurry that has completed adsorption to be discharged from the slurry discharge pipe 303 to the slurry collection tank. The specific operation is as follows: When the ammonia nitrogen and phosphorus concentration data of the post-nitrogen and phosphorus concentration real-time detection unit 501 is 30% of the ammonia nitrogen and phosphorus concentration detected by the pre-nitrogen and phosphorus concentration real-time detection unit 401, or after the filter layer has been running continuously for 30-45 days, it is determined that the main adsorption zone 3 is saturated. Start the grouting pump and inject new bentonite slurry with a solid-liquid ratio of 1:3 into the main adsorption zone 3 through the grouting pipe 302 at a pressure of 0.3-0.5MPa. The injection volume is 1.1-1.3 times the volume of the main adsorption zone 3. This pushes the saturated old slurry out of the slurry discharge pipe to the slurry collection tank, completing the filter layer renewal. After the filter layer is replaced, let it stand for 24 hours and test the nitrogen and phosphorus removal rate at the outlet. If the removal rate is ≥85%, resume the tailwater filtration operation; if the removal rate is <85%, repeat the grouting and replacement step. The old mud in the mud collection tank is sent to the drying equipment and dried at 60-80℃ until the moisture content is ≤15%, which is then made into granular inorganic fertilizer. The nitrogen and phosphorus content in the fertilizer is tested to ensure that it meets the inorganic nutrient requirements in the NY / T 525-2021 "Organic Fertilizer" standard.

Claims

1. A nitrogen and phosphorus adsorption unit for fish farming wastewater, comprising two vertical pipes (1) with open tops and perforations distributed on their surfaces, characterized in that: Between two vertical pipes (1), a number of support pipes (101) with through holes (103) distributed on their surfaces are distributed along their height direction. Both ends of each support pipe (101) are connected to the inside of the vertical pipe (1). A number of adsorption balls (2) are distributed inside. These adsorption balls (2) are connected in series by connecting lines (102), and both ends of the connecting lines (102) pass through the top opening of the vertical pipe (1). Each adsorption ball (2) is filled with bentonite, and a number of seepage holes (202) are distributed on its surface.

2. A nitrogen and phosphorus adsorption device for fish farming wastewater, comprising a front protective filter layer (4) and a rear support filter layer (5) arranged sequentially along the wastewater flow direction, with the two forming a main adsorption zone (3), characterized in that: The main adsorption zone (3) is filled with an adsorption material formed by mixing bentonite and coarse sand in a mass ratio of 1:2-9, and multiple sets of nitrogen and phosphorus adsorption units as described in claim 1 are distributed in the main adsorption zone (3). The support tube (101) in each set of nitrogen and phosphorus adsorption units is arranged along the water head flow network in the main adsorption zone (3).

3. The nitrogen and phosphorus adsorption device for fish farming wastewater according to claim 2, characterized in that: The particle size of bentonite in the main adsorption zone (3) does not exceed 0.01 mm, and the particle size of coarse sand is 2-5 mm. The gradation design method in the main adsorption zone (3) is as follows: S1. Given a pre-defined permeability coefficient k and hydraulic gradient i, where k = 1.5 - 2.0 and i < 0.5, calculate d using the Hassen formula. 10 ; Hassen's formula is ; In the formula, C is an empirical coefficient, with a value of 100-150; n is the porosity, n=Vv / V×100%; Vv is the pore volume, and V is the total volume of the sample. Vv and V are obtained through geotechnical tests. S2, d obtained from step S1 10 Construct a continuous and smooth gradation curve, and then obtain d from this gradation curve. 30 and d 60 According to d 30 and d 60 Calculate the non-uniformity coefficient C at this time. u and curvature coefficient C c ; Inhomogeneity coefficient C u The calculation formula is: ; curvature coefficient C c The calculation formula is: ; In the formula, d 60 For particles that account for 60% of the weight of the sieve, d 30 The particle size that accounts for 30% of the weight of the sieved particles; S3. Determine the non-uniformity coefficient C calculated in step S2. u Does it satisfy C? u <5, and curvature coefficient C c Does it satisfy C? c =1-3, if satisfied, proceed to step S4; if not satisfied, return to step S1; S4. Based on the permeability coefficient k and hydraulic gradient i preset in step S1, Darcy's law is applied. Calculate the seepage velocity v, and then calculate the Reynolds number Re using the Reynolds number formula; The Reynolds number formula is ; In the formula, Fluid density, unit: kg / m³ 3 v represents the seepage velocity, in m / s; d 10 The d obtained in step S1 10 μ is the dynamic viscosity of the fluid, measured in Pa·s or kg / (m·s); S5. Determine whether Re calculated in step S4 is less than 10. If it is less than 10, proceed to step S6. If it is greater than or equal to 10, return to step S1. S6. Based on the gradation curve constructed in step S2, construct an indoor model using coarse sand with a particle size of 2-5 mm and bentonite with a particle size of no more than 0.01 mm, and conduct a permeability test. Determine the actual permeability coefficient k through the permeability test. If the actual permeability coefficient k satisfies k=1.5-2.0, proceed to step S7; otherwise, return to step S1. S7. Use the indoor model constructed in step S6 to conduct a seepage stability test to determine whether the risk of piping and soil erosion meets the standards. If it does not meet the standards, return to step S1. If it meets the standards, the gradation curve constructed in step S2 is the gradation distribution in the main adsorption zone.

4. The nitrogen and phosphorus adsorption device for fish farming wastewater according to claim 2, characterized in that: The bottom of the front protective filter layer (4), the main adsorption zone (3) and the rear support filter layer (5) are provided with an impermeable layer (301).

5. The nitrogen and phosphorus adsorption device for fish farming wastewater according to claim 2, characterized in that: A backwash pipe (402) is provided inside the front protective filter layer (4).

6. The nitrogen and phosphorus adsorption device for fish farming wastewater according to claim 2, characterized in that: The main adsorption zone (3) is provided with a grouting pipe (302) for injecting bentonite slurry into the main adsorption zone (3) and a grouting pipe (303) for discharging bentonite slurry.

7. A fish farming wastewater treatment system, comprising a wastewater collection tank (6) located on one side of a fishpond (8), characterized in that: The outlet of the tailwater collection tank (6) is equipped with a nitrogen and phosphorus adsorption device as described in any one of claims 2-6.

8. A fish farming wastewater treatment system according to claim 7, characterized in that: The tailwater collection tank (6) is equipped with a water pump (601) that draws tailwater from the fishpond (8) and a water level sensor (602) that monitors the water level in the tailwater collection tank (6). The tailwater discharged from the nitrogen and phosphorus adsorption device enters the sedimentation tank (7) to settle.

9. A fish farming wastewater treatment system according to claim 7, characterized in that: The front protective filter layer (4) and the rear support filter layer (5) of the nitrogen and phosphorus adsorption device are respectively provided with a front nitrogen and phosphorus concentration real-time detection unit (401) and a rear nitrogen and phosphorus concentration real-time detection unit (501).

10. A method for treating fish farming wastewater using the wastewater treatment system according to claim 9, characterized in that, Includes the following steps: 1) Set up a tailwater collection pond (6) on one side of the fishpond (8). The outlet of the tailwater collection pond (6) is connected to the sedimentation pond (7). In the outlet of the tailwater collection pond (6), according to the direction of tailwater flow, first construct a front protective filter layer (4) with coarse sand with a particle size of 2-5mm, and then construct a rear support filter layer (5) with gravel with a particle size of 5-10mm. The space between the two forms the main adsorption zone (3). 2) Calculate the distribution of the head flow network in the main adsorption zone (3) according to the existing head flow network calculation method, and then plan the layout of the support pipe (101) in advance according to the calculated head flow network distribution to form the layout design of the support pipe (101) in the main adsorption zone (3); 3) Use a mixture of bentonite with a particle size not exceeding 0.01 mm and coarse sand with a particle size of 2-5 mm to fill the main adsorption zone (3). During the filling process, install the support tube (101) for filling the adsorption ball (2) according to the layout design diagram formed in step 2), and expose the end of the vertical tube (1) in the adsorption nitrogen and phosphorus unit to the surface of the main adsorption zone (3). 4) Inject tailwater into the tailwater collection tank (6) so that the tailwater can pass through the front protective filter layer (4), the main adsorption zone (3) and the rear support filter layer (5) in a permeable manner and enter the sedimentation tank (7); 5) Take the two vertical pipes (1) in each nitrogen and phosphorus adsorption unit as grouting pipe (302) and grout discharge pipe (303) respectively. Based on the ammonia nitrogen and phosphorus concentration data monitored in real time by the real-time nitrogen and phosphorus concentration detection unit (401), adjust the proportion of bentonite in the main adsorption zone (3) through grouting pipe (302) and grout discharge pipe (303). 6) Monitor the ammonia nitrogen and phosphorus concentration data of the real-time nitrogen and phosphorus concentration detection unit (501) in real time. If the concentration reaches the set standard, inject bentonite slurry with a solid-liquid ratio of 1:3 into the main adsorption zone (3) through the grouting pipe (302) at a pressure of 0.3-0.5MPa. The injection volume is 1.1-1.3 times the volume of the main adsorption zone (3) to push the bentonite slurry that has completed adsorption out of the grouting pipe (303).

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