A sea cucumber seedling rearing tail water treatment and reuse process

Abstract

The present invention discloses a sea cucumber seedling rearing tail water treatment and reuse process, belonging to the technical field of sea cucumber seedling rearing, including a sea cucumber seedling rearing pond, a horizontal flow grit chamber, a drum filter and a microfiltration tank, a particulate matter collection tank, a high-temperature fermentation tank, a straw carrier biological filter tank and a plate heat exchanger. In the present invention, large particulate matter in the tail water is removed by the horizontal flow grit chamber, and then small particulate matter in the water is removed by the drum filter and microfiltration. Then, the straw carrier biological filter tank is used to strengthen the removal of microorganisms and inorganic nitrogen of nitrates with the straw carrier as a slow-release carbon source. In the present invention, heat exchange is carried out between seawater and tail water through the plate heat exchanger to increase the seawater temperature for sea cucumber seedling rearing. In the present invention, the aged biofilm in the straw carrier biological filter tank returns to the filtration system with the backwash water for filtration, and then enters the particulate matter collection tank together with the particulate matter generated by the filtration system. After the particulate matter, the aged biofilm and microalgae are mixed and fermented in the high-temperature fermentation tank, they can be used as a feed additive for sea cucumbers.

Description

Technical Field

[0001] The present invention belongs to the technical field of sea cucumber seedling cultivation, and particularly relates to a process for treating and recycling the tail water of sea cucumber seedling cultivation. Background Art

[0002] As a kind of seafood with extremely high nutritional and medical value, sea cucumbers have always been favored by consumers. In recent years, the sea cucumber aquaculture industry has developed rapidly, and seedling cultivation is one of the key steps. Sea cucumber seedling cultivation mostly adopts the factory-style running water aquaculture mode, with a large water consumption and a large amount of tail water generated. Since a large amount of sea mud needs to be added to sea cucumber feed to ensure the normal excretion function of sea cucumbers, the tail water generated during the seedling cultivation process contains a large amount of particulate matter, organic matter, and nutrients. If such wastewater is not properly treated and discharged into the sea water, it will inevitably have a negative impact on the nearshore marine environment.

[0003] Compared with the tail water of other seafood aquaculture, the particulate matter content in the tail water of sea cucumber seedling cultivation is relatively large, and it is mainly sea mud with relatively large particles. The commonly used aquaculture tail water treatment process mostly adopts a combination of filtration and biological treatment to treat particulate matter, dissolved organic matter, and nutrients in the water respectively. For the tail water of sea cucumber seedling cultivation, if only the filtration method is used to treat particulate matter, it will increase the equipment load and cause problems such as equipment blockage. The existing biological treatment method mainly converts ammonium salts into nitrates through oxygenation and then discharges them into the sea water. However, the nitrates discharged into the sea water can still be absorbed and utilized by algae through the action of marine biogeochemical processes, thereby causing water eutrophication. Therefore, with the improvement of emission standards, the treatment of nitrates in aquaculture tail water has also attracted people's attention. However, due to the low organic matter content in the tail water, it is difficult to use the organic matter in the tail water to reduce nitrates to achieve the purpose of denitrification and nitrogen removal, which has become a difficult point in the treatment of sea cucumber aquaculture tail water.

[0004] In addition to pollutants, the tail water of sea cucumber seedling cultivation also contains energy and resources that can be recycled. Sea mud is an essential component in sea cucumber feed, and with the continuous growth of the sea cucumber aquaculture industry, the demand for sea mud is gradually increasing. If a large amount of sea mud and various particulate matters in the seedling tail water can be recycled, the pressure of sea mud mining can be reduced, which contributes to the protection of the marine ecological environment. In addition, the tail water of sea cucumber seedling cultivation contains a large amount of heat that can be recycled. The water temperature required for sea cucumber seedling cultivation is 10 - 15 °C. In winter, the sea water temperature is close to 0 °C, and the discharged tail water temperature is 15 - 18 °C. If the heat of the tail water and sea water can be heat-exchanged to increase the sea water temperature, the electricity cost generated by enterprises for heating sea water in winter can be reduced. Summary of the Invention

[0005] In order to solve the problems raised in the above background art, the present invention provides a process for treating and recycling the tail water of sea cucumber seedling cultivation, which has the characteristics of increasing the sea water temperature, effectively removing microorganisms, and recycling particulate matter.

[0006] To achieve the above object, the present invention provides the following technical solution: a sea cucumber seedling rearing tail water treatment and reuse process, including a sea cucumber seedling rearing pond, a horizontal flow grit chamber, a drum filter and a microfiltration tank, a particulate matter collection tank, a high-temperature fermentation tank, a straw carrier biological filter tank and a plate heat exchanger. The water inlet of the sea cucumber seedling rearing pond is connected to an electric heating tank, the water outlet end of the sea cucumber seedling rearing pond is connected to a horizontal flow grit chamber, the water outlet end of the horizontal flow grit chamber is connected to a drum filter and a microfiltration tank, the water outlet end of the drum filter and the microfiltration tank is connected to a straw carrier biological filter tank, the water outlet end of the straw carrier biological filter tank is connected to a plate heat exchanger, the water outlet end of the plate heat exchanger is connected to the electric heating tank, the water inlet end of the electric heating tank is connected to a sand filter tank, the water outlet end of the sand filter tank is connected to the water inlet end of the plate heat exchanger, the solid discharge port of the drum filter and the microfiltration tank is connected to a particulate matter collection tank, and the discharge port of the particulate matter collection tank is connected to a high-temperature fermentation tank;

[0007] The process flow includes the following steps;

[0008] First, the tail water generated in the sea cucumber seedling rearing pond flows into the horizontal flow grit chamber, and particulate matter larger than 200 μm in the tail water is removed through filtration in the horizontal flow grit chamber;

[0009] Second, particulate matter with a size of 2 - 200 μm in the water is removed by the drum filter and the microfilter in the drum filter and the microfiltration tank;

[0010] Third, the organic matter and inorganic nitrogen in the water are removed by using the straw carrier biological filter tank. The biological carrier is straw, and the straw mats are laid flat in the filter tank. When the tail water flows through the straw carrier layer, the organic matter and inorganic nitrogen in the water are removed;

[0011] Fourth, the treated tail water transfers heat to the seawater taken from the outside filtered by the sand filter tank through the plate heat exchanger, and the seawater is heated through heat exchange for sea cucumber seedling rearing in the sea cucumber seedling rearing pond in winter;

[0012] Fifth, the aged biofilm in the straw carrier biological filter tank returns to the filtration system for filtration along with the backwash water, and then enters the particulate matter collection tank together with the particulate matter generated in the horizontal flow grit chamber and the drum filter and the microfiltration tank. After the particulate matter, the aged biofilm and microalgae are mixed and fermented in the high-temperature fermentation tank, they can be used as a feed additive for sea cucumbers.

[0013] Furthermore, the filtration aperture of the drum filter in the drum filter and the microfiltration tank is 5 - 10 μm, and the filtration aperture of the microfilter used in the drum filter and the microfiltration tank is 2 - 5 μm. The removal rate of particulate matter with a particle size of 2 - 200 μm can reach 93 - 95%.

[0014] Furthermore, the straw carrier biological filter uses straw mats as microbial carriers. The straw carrier layer accounts for 55-70% of the filter volume, and the rate of organic matter release is 4-8 mgCOD Mn / g straw / d. The suitable water temperature is 15-18 °C, the suitable pH is 6-9, and the suitable water flow rate is 5-8 m / h.

[0015] Furthermore, the straw carrier biological filter uses the mixed liquid of urban sewage plant sludge with a sludge concentration of 300-700 mgSS / L as the inoculum for film hanging. During film hanging, the external circulation flow rate at the inlet and outlet needs to be controlled at 4-6 m 3 / h. Using the tail water of sea cucumber seedling rearing as the nutrient, continuously enrich the biofilm, control the hydraulic retention time at 18-24 h, and the aeration volume at 125-170 m 3 / h. After stable operation for 14-30 days, the film hanging process ends.

[0016] Furthermore, the salinity of the tail water of sea cucumber seedling rearing treated by the straw carrier biological filter is 28-32‰, the temperature is 15-18 °C, and the NH4 + -N concentration is 0.3-0.8 mg / L, the organic matter concentration is 3-8 mgCOD Mn / L, and the NO3 - -N concentration is 5-15 mg / L.

[0017] Furthermore, when the straw carrier biological filter treats the tail water of sea cucumber seedling rearing, the controlled hydraulic retention time is 1.5-3 h, and the air-water ratio is 25-40.

[0018] Furthermore, when the straw carrier biological filter treats the tail water of sea cucumber seedling rearing, when the effluent suspended solids SS is 15-20 mg / L for three consecutive days, generally, air-water combined backwashing is required every 30-60 days. The backwashing air volume during backwashing is 10-12 L / m 2 / s, the backwashing water volume is 3-5 L / m 2 / s, and the backwashing time is 20-60 min.

[0019] Furthermore, the plate heat exchanger is mainly used in winter to raise the seawater temperature from 0-2 °C to 4-6 °C and reduce the tail water temperature from 15-18 °C to 10-12 °C.

[0020] Furthermore, the mixing ratio of the mixture of particulate matter and aged biofilm in the high-temperature fermentation tank to microalgae is 20:1-25:1, the fermentation temperature is 55-60 °C, and the fermentation time is 20-30 days.

[0021] Further, a storage battery is connected to the input end of the electric heating device of the electric heating pool. The power input end of the storage battery is connected to an inverter. The control end interface of the inverter is connected to a controller. The input end of the inverter is connected to a wind turbine and a solar panel.

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

[0023] 1. In the present invention, large particulate matters in the tail water are removed through a horizontal flow grit chamber, and then small particulate matters in the water are removed through drum filtration and microfiltration. Then, a straw carrier biological filter is used to strengthen the removal of microorganisms and inorganic nitrogen of nitrate with the straw carrier as a slow-release carbon source.

[0024] 2. In the present invention, heat exchange is carried out between seawater and tail water through a plate heat exchanger to increase the seawater temperature for sea cucumber seedling cultivation, improving the reuse of tail water.

[0025] 3. In the present invention, the aged biofilm in the straw carrier biological filter returns to the filtration system for filtration along with the backwash water, and then enters the particulate matter collection pool together with the particulate matters generated by the filtration system. After the particulate matters, the aged biofilm and microalgae are mixed and fermented in a high-temperature fermentation tank, which can be used as a feed additive for sea cucumbers.

[0026] 4. In the present invention, wind energy is generated by a wind turbine, and solar energy is generated by a solar panel. The generated electric energy is converted by an inverter and stored in a storage battery, and the storage battery supplies power to the electric heating device of the electric heating pool, improving the utilization of clean energy, reducing energy consumption, and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a process flow block diagram of the present invention;

[0028] In the figure: 1. Sea cucumber seedling cultivation pool; 2. Horizontal flow grit chamber; 3. Drum filtration and microfiltration pool; 4. Particulate matter collection pool; 5. High-temperature fermentation tank; 6. Straw carrier biological filter; 7. Plate heat exchanger; 8. Sand filter; 9. Electric heating pool; 10. Storage battery; 11. Inverter; 12. Controller; 13. Wind turbine; 14. Solar panel. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Embodiment 1

[0031] Please refer to Figure 1 , the present invention provides the following technical solutions: A sea cucumber seedling rearing tail water treatment and reuse process, including a sea cucumber seedling rearing pond 1, a horizontal flow grit chamber 2, a drum filter and a microfiltration tank 3, a particulate matter collection tank 4, a high-temperature fermentation tank 5, a straw carrier biological filter tank 6 and a plate heat exchanger 7. The water inlet of the sea cucumber seedling rearing pond 1 is connected to an electric heating tank 9. The water outlet end of the sea cucumber seedling rearing pond 1 is connected to the horizontal flow grit chamber 2. The water outlet end of the horizontal flow grit chamber 2 is connected to the drum filter and the microfiltration tank 3. The water outlet end of the drum filter and the microfiltration tank 3 is connected to the straw carrier biological filter tank 6. The water outlet end of the straw carrier biological filter tank 6 is connected to the plate heat exchanger 7. The water outlet end of the plate heat exchanger 7 is connected to the electric heating tank 9. The water inlet end of the electric heating tank 9 is connected to a sand filter tank 8. The water outlet end of the sand filter tank 8 is connected to the water inlet end of the plate heat exchanger 7. The solid discharge port of the drum filter and the microfiltration tank 3 is connected to the particulate matter collection tank 4. The discharge port of the particulate matter collection tank 4 is connected to the high-temperature fermentation tank 5;

[0032] The process flow includes the following steps;

[0033] First, the tail water generated by the sea cucumber seedling rearing pond 1 flows into the horizontal flow grit chamber 2, and particulate matter larger than 200 μm in the tail water is removed through filtration by the horizontal flow grit chamber 2;

[0034] Second, particulate matter with a size of 2 - 200 μm in the water is removed by the drum filter and the microfilter in the drum filter and the microfiltration tank 3;

[0035] Third, the organic matter and inorganic nitrogen in the water are removed by using the straw carrier biological filter tank 6. The biological carrier is straw, and the straw mats are laid flat in the filter tank. When the tail water flows through the straw carrier layer, the organic matter and inorganic nitrogen in the water are removed;

[0036] Fourth, the treated tail water transfers heat to the seawater taken from the outside filtered by the sand filter tank 8 through the plate heat exchanger 7, and the seawater is heated through heat exchange for sea cucumber seedling rearing in the sea cucumber seedling rearing pond 1 in winter;

[0037] Fifth, the aged biofilm in the straw carrier biological filter tank 6 returns to the filtration system with the backwash water for filtration, and then enters the particulate matter collection tank 4 together with the particulate matter generated by the horizontal flow grit chamber 2 and the drum filter and the microfiltration tank 3. After the particulate matter, the aged biofilm and microalgae are mixed and fermented in the high-temperature fermentation tank 5, they can be used as a feed additive for sea cucumbers.

[0038] Further in the present invention, the filtration aperture of the drum filter in the drum filter and the microfiltration tank 3 is 5 - 10 μm, and the filtration aperture of the microfilter used in the drum filter and the microfiltration tank 3 is 2 - 5 μm. The removal rate of particulate matter with a particle size of 2 - 200 μm can reach 93 - 95%.

[0039] Further in the present invention, in the straw carrier biological filter 6, a straw mat is used as the microbial carrier. The straw carrier layer accounts for 55 - 70% of the filter volume, and the rate of organic matter release is 4 - 8 mgCOD Mn / g straw / d. The suitable water temperature is 15 - 18°C, the suitable pH is 6 - 9, and the suitable water flow rate is 5 - 8 m / h.

[0040] Further in the present invention, in the straw carrier biological filter 6, the sludge mixture of a municipal wastewater treatment plant with a sludge concentration of 300 - 700 mgSS / L is used as the inoculum for film formation. During film formation, the external circulation flow rate at the inlet and outlet needs to be controlled at 4 - 6 m 3 / h. Using the sea cucumber seedling rearing tail water as the nutrient, the biological film is continuously enriched. The hydraulic retention time is controlled at 18 - 24 h, and the aeration volume is 125 - 170 m 3 / h. After stable operation for 14 - 30 days, the film formation process ends.

[0041] Further in the present invention, when the straw carrier biological filter 6 treats the sea cucumber seedling rearing tail water, the salinity is 28 - 32‰, the temperature is 15 - 18°C, and the NH4 + -N concentration is 0.3 - 0.8 mg / L, the organic matter concentration is 3 - 8 mgCOD Mn / L, and the NO3 - -N concentration is 5 - 15 mg / L.

[0042] Further in the present invention, when the straw carrier biological filter 6 treats the sea cucumber seedling rearing tail water, the controlled hydraulic retention time is 1.5 - 3 h, and the air-water ratio is 25 - 40.

[0043] Further in the present invention, when the straw carrier biological filter 6 treats the sea cucumber seedling rearing tail water, when the suspended solids SS in the effluent is 15 - 20 mg / L for three consecutive days, generally, air-water combined backwashing needs to be carried out every 30 - 60 days. During backwashing, the backwashing air volume is 10 - 12 L / m 2 / s, the backwashing water volume is 3 - 5 L / m 2 / s, and the backwashing time is 20 - 60 min.

[0044] Further in the present invention, the plate heat exchanger 7 is mainly used in winter to increase the sea water temperature from 0 - 2°C to 4 - 6°C and reduce the tail water temperature from 15 - 18°C to 10 - 12°C.

[0045] Further in the present invention, the mixing ratio of the mixture of particulate matter and aged biofilm in the high-temperature fermentation tank 5 to microalgae is 20:1 - 25:1, the fermentation temperature is 55 - 60°C, and the fermentation time is 20 - 30 days.

[0046] The daily water treatment capacity of this embodiment is 3000 m 3 / d. First, the biofilm is formed in the straw carrier biological filter 6. The straw mats are laid layer by layer in the filter. The straw filter layer accounts for 60% of the filter volume. Then, a sludge mixture of the sewage treatment plant with a sludge concentration of 450 mg SS / L is prepared for the straw carrier biological filter 6, ensuring that the liquid level reaches the outlet. At this time, the sea cucumber seedling rearing tail water is introduced into the filter, entering from the inlet of the filter and discharging from the outlet. At the same time, an external circulation is established between the inlet and outlet using a circulation pump, controlling the circulation water flow rate at 5 m 3 / h, ensuring full mixing of the sludge mixture and the straw carrier. During the biofilm formation process, the hydraulic retention time is controlled at 22 h, and the aeration rate is 130 m 3 / h. After 21 days of biofilm formation, the presence of the biofilm can be clearly seen on the straw carrier, and the biofilm formation is completed;

[0047] When treating the seedling rearing tail water, a horizontal flow grit chamber 2 is set up with a tank volume of 2000 m 3 , the water flow rate is 0.258 m / h, and the removal rate of particles with a particle size of more than 200 μm can reach 99%. Then, a drum filter with a filtration pore size of 5 - 10 μm and a microfiltration machine with a filtration pore size of 2 - 5 μm are used to filter the tail water. The removal rate of particles with a particle size of more than 2 μm in the water can reach 95% after filtration. The filtered tail water enters the straw carrier biological filter 6. The salinity of this tail water is 30‰, the water temperature is 17°C, pH is 6.8 - 7.5, the NH4 + -N concentration is 0.4 - 0.7 mg / L, the organic matter concentration is 3 - 8 mg COD Mn / L, the NO3 - -N concentration is 7 - 10 mg / L. During the treatment process, the hydraulic retention time is controlled at 2.5 h, and the air-water ratio is 32. The SS of the treated effluent is less than 20 mg / L, the organic matter concentration is less than 8 mg / L, and the total inorganic nitrogen is less than 0.05 mg / L. When the SS of the effluent from the straw carrier biological filter has been 15 - 18 mg / L for three consecutive days after 45 days of operation of the straw carrier biological filter, air-water combined backwashing is used to clean the aged biofilm in the biological filter. The backwashing air volume is 11 L / m 2 / s, the backwashing water volume is 4 L / m 2 / s, and the backwashing time is 40 min. The tail water purified by the straw carrier biological filter 6 exchanges heat with the seawater taken from outside through a plate heat exchanger 7. After the exchange, the temperature of the seawater taken from outside is raised from 0°C to 5°C, and the temperature of the tail water is lowered from 17°C to 11°C. When the straw carrier biological filter 6 is backwashed, the aged biofilm is flushed into the filtration system, and after filtration, it is mixed with the particles and enters the high-temperature fermentation tank 5. A certain amount of microalgae is added to the high-temperature fermentation tank 5 to ensure that the mixing ratio of the mixture of particles and the aged biofilm to the microalgae is 25:1. The fermentation temperature is 58°C. After 30 days of fermentation, the fermentation product is obtained and can be used as a feed additive for sea cucumbers;

[0048] Example 2

[0049] The daily water treatment capacity of this embodiment is 3500 m 3 / d. First, the biofilm is formed on the straw carrier biological filter 6. The straw mats are laid layer by layer in the filter. The straw filter layer accounts for 60% of the filter volume. Then, a mixed solution of sewage treatment plant sludge with a sludge concentration of 500 mg SS / L and straw carrier biological filter 6 is prepared, ensuring that the liquid level reaches the outlet. At this time, the sea cucumber seedling rearing tail water is introduced into the filter. The tail water enters from the inlet of the filter and exits from the outlet. At the same time, an external circulation is established at the inlet and outlet using a circulation pump, and the circulation water flow rate is controlled at 6 m 3 / h to ensure full mixing of the sludge mixed solution and the straw carrier. During the biofilm formation process, the hydraulic retention time is controlled at 24 h, and the aeration rate is 150 m 3 / h. After 30 days of biofilm formation, the presence of the biofilm can be clearly seen on the straw carrier, and the biofilm formation is completed;

[0050] When treating the seedling rearing tail water, a horizontal flow grit chamber 2 is set up with a volume of 2000 m 3 . The water flow velocity is 0.301 m / h, and the removal rate of particles with a particle size of more than 200 μm can reach 98%. Then, a drum filter with a filtration pore size of 5 - 10 μm and a microfiltration machine with a filtration pore size of 2 - 5 μm are used to filter the tail water. The removal rate of particles with a particle size of more than 2 μm in the water can reach 94%. The filtered tail water enters the straw carrier biological filter 6. The salinity of this tail water is 32‰, the water temperature is 15℃, the pH is 7.2 - 8.3, the NH4+-N concentration is 0.3 - 0.8 mg / L, the organic matter concentration is 4 - 7 mg COD Mn / L, and the NO3 - -N concentration is 5 - 13 mg / L. During the treatment process, the hydraulic retention time is controlled at 3 h, and the air-water ratio is 30. The SS of the treated effluent is less than 20 mg / L, the organic matter concentration is less than 8 mg / L, and the total inorganic nitrogen is less than 0.05 mg / L. When the SS of the effluent from the straw carrier biological filter 6 is 15 - 18 mg / L for three consecutive days during the 35th day of operation, air-water combined backwashing is used to clean the aged biofilm in the biological filter. The backwashing air volume is 10 L / m 2 / s, the backwashing water volume is 3 L / m 2 / s, and the backwashing time is 50 min. The tail water purified by the biological filter exchanges heat with the seawater taken from outside through a plate heat exchanger 7. After the exchange, the temperature of the seawater taken from outside is increased from 0℃ to 4℃, and the temperature of the tail water is decreased from 15℃ to 10℃. When the biological filter is backwashed, the aged biofilm is flushed into the filtration system, and after filtration, it is mixed with the particles and enters the high-temperature fermentation tank 5. A certain amount of microalgae is added to the high-temperature fermentation tank 5 to ensure that the mixing ratio of the mixture of particles and aged biofilm to microalgae is 20:1. The fermentation temperature is 60℃. After 30 days of fermentation, the fermentation product is obtained and can be used as a feed additive for sea cucumbers;

[0051] Example 3

[0052] The difference between this embodiment and Embodiments 1 and 2 lies in that: the input end of the electric heating device of the electric heating pool 9 is connected to a storage battery 10, the power input end of the storage battery 10 is connected to an inverter 11, the control end interface of the inverter 11 is connected to a controller 12, and the input end of the inverter 11 is connected to a wind turbine 13 and a solar panel 14.

[0053] In this embodiment, wind energy is generated by the wind turbine 13 and solar energy is generated by the solar panel 14. The generated electric energy is converted by the inverter 11 and stored in the storage battery 10, and the storage battery 10 supplies power to the electric heating device of the electric heating pool 9, improving the utilization of clean energy, reducing energy consumption, and saving costs.

[0054] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sea cucumber seedling rearing tail water treatment and reuse process, including a sea cucumber seedling rearing pond (1), a horizontal flow grit chamber (2), a drum filter and microfiltration pond (3), a particulate matter collection pond (4), a high-temperature fermentation pond (5), a straw carrier biological filter pond (6) and a plate heat exchanger (7), characterized in that: The water inlet of the sea cucumber breeding pond (1) is connected to an electric heating pond (9), and the water outlet end of the sea cucumber breeding pond (1) is connected to a horizontal flow sedimentation pond (2). The water outlet end of the horizontal flow sedimentation pond (2) is connected to a drum filter and microfiltration pond (3). The water outlet end of the drum filter and microfiltration pond (3) is connected to a rice straw carrier biological filter pond (6). The water outlet end of the rice straw carrier biological filter pond (6) is connected to a plate heat exchanger (7). The water outlet end of the plate heat exchanger (7) is connected to the electric heating pond (9). The water inlet end of the electric heating pond (9) is connected to a sand filter pond (8). The water outlet end of the sand filter pond (8) is connected to the water inlet end of the plate heat exchanger (7). The solid discharge port of the drum filter and microfiltration pond (3) is connected to a particulate matter collection pond (4). The discharge port of the particulate matter collection pond (4) is connected to a high-temperature fermentation pond (5); The process flow includes the following steps: The tail water generated in the sea cucumber breeding pond (1) flows into the horizontal flow sedimentation pond (2), and particulate matter larger than 200 μm in the tail water is removed through filtration in the horizontal flow sedimentation pond (2); Particulate matter with a size of 2 - 200 μm in the water is removed by the drum filter and microfilter in the drum filter and microfiltration pond (3); The rice straw carrier biological filter pond (6) is used to remove organic matter and inorganic nitrogen in the water. The biological carrier is rice straw, and the rice straw carrier layer is laid flat in the filter pond. When the tail water flows through the rice straw carrier layer, the organic matter and inorganic nitrogen in the water are removed; The treated tail water transfers heat to the seawater taken from the outside filtered by the sand filter pond (8) through the plate heat exchanger (7), and the seawater is heated through heat exchange for sea cucumber breeding in winter in the sea cucumber breeding pond (1); The aged biofilm in the rice straw carrier biological filter pond (6) returns to the filtration system for filtration along with the backwash water, and then enters the particulate matter collection pond (4) together with the particulate matter generated in the horizontal flow sedimentation pond (2) and the drum filter and microfiltration pond (3). After the particulate matter, aged biofilm and microalgae are mixed and fermented in the high-temperature fermentation pond (5), they can be used as feed additives for sea cucumbers.

2. The sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: The filtration aperture of the drum filter used in the drum filter and microfiltration pond (3) is 5 - 10 μm, and the filtration aperture of the microfilter used in the drum filter and microfiltration pond (3) is 2 - 5 μm. The removal rate of particulate matter with a particle size of 2 - 200 μm can reach 93 - 95%.

3. A sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: The straw carrier biological filter (6) uses a straw carrier layer as a microbial carrier. The straw carrier layer accounts for 55-70% of the filter volume, and the rate of organic matter release is 4-8 mgCOD Mn / g straw / d. The suitable water temperature is 15-18 °C, the suitable pH is 6-9, and the suitable water flow rate is 5-8 m / h.

4. A sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: The straw carrier biological filter (6) uses the mixed liquid of sludge from a municipal wastewater treatment plant with a sludge concentration of 300 - 700 mg SS / L as the inoculum for film formation. During film formation, the external circulation flow rate at the inlet and outlet needs to be controlled at 4 - 6 m 3 / h, and the biological film is continuously enriched with the tail water from sea cucumber seedling cultivation as the nutrient. The hydraulic retention time is controlled at 18 - 24 h, and the aeration volume is 125 - 170 m 3 / h. After stable operation for 14 - 30 days, the film formation process ends.

5. A sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: The salinity of the sea cucumber seedling rearing tail water treated by the straw carrier biological filter (6) is 28-32‰, the temperature is 15-18°C, the concentration of NH4 + -N is 0.3-0.8 mg / L, and the organic matter concentration is 3-8 mgCOD Mn / L, and the concentration of NO3 - -N is 5-15 mg / L.

6. The sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: When the rice straw carrier biological filter pond (6) treats the tail water of sea cucumber breeding, the controlled hydraulic retention time is 1.5 - 3 h, and the air-water ratio is 25 - 40.

7. A sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: When the straw carrier biological filter (6) treats the tail water of sea cucumber seedling cultivation, when the suspended solids (SS) in the effluent is 15 - 20 mg / L for three consecutive days, air-water combined backwashing is generally required every 30 - 60 days. The air volume for backwashing is 10 - 12 L / m 2 / s, and the water volume for backwashing is 3 - 5 L / m 2 / s, and the backwashing time is 20 - 60 min.

8. A sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: The plate heat exchanger (7) is mainly used in winter to raise the water temperature of seawater at 0 - 2 °C to 4 - 6 °C and reduce the tail water temperature from 15 - 18 °C to 10 - 12 °C.

9. A sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: The mixing ratio of the mixture of particulate matter and aged biofilm in the high-temperature fermentation pond (5) and microalgae is 20:1 - 25:1, the fermentation temperature is 55 - 60 °C, and the fermentation time is 20 - 30 days.

10. A sea cucumber seedling rearing tail water treatment and reuse process according to claim 1, characterized in that: The input end of the electric heating device of the electric heating pool (9) is connected to a storage battery (10), the power input end of the storage battery (10) is connected to an inverter (11), the control end interface of the inverter (11) is connected to a controller (12), and the input end of the inverter (11) is connected to a wind turbine (13) and a solar panel (14).

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