Multi-trophic-level ecological purification system for high-salinity aquaculture tail water

Abstract

The invention belongs to the technical field of high-salinity aquaculture tail water treatment, and particularly provides a multi-trophic-level ecological purification system for high-salinity aquaculture tail water. Aiming at the current situations that the existing mariculture tail water is high in nitrogen and phosphorus content and high in salinity and the existing ecological treatment system is poor in purification effect, the invention provides a composite purification path with three synergistic systems of a spartina alterniflora system (nitrifying bacteria), a sea horse tooth (phosphorus-accumulating bacteria) and an ulva lactuca (algae symbiosis). According to the invention, light energy is absorbed, harmful algae are inhibited, suspended solids are physically intercepted and adsorbed, nitrogen, phosphorus, COD and heavy metal Cd in a water body environment are removed through cooperation of phosphorus-accumulating bacteria and denitrifying bacteria, the cost is reduced, and the economic income of by-products is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-salinity aquaculture tail water treatment, and in particular relates to a multi-trophic level multi-pond coupled biological ecological purification technology. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Currently, resource and environmental issues have become one of the main bottlenecks hindering the green and healthy development of aquaculture. After my country's initial development phase, which was primarily based on aquaculture, a large amount of unpurified tailwater was cultivated in earthen ponds. The single-species, high-density, large-scale aquaculture model that gradually emerged across various regions posed a major challenge to the environmental carrying capacity. Currently, resource and environmental issues have become one of the main bottlenecks hindering the green and healthy development of aquaculture. The aquaculture industry is facing increasingly prominent environmental issues, such as large discharges of water pollutants. These issues, such as lack of facilities, extensive management, increased production, surging pressure, increased intensive development scale, and large discharge volumes, have severely hampered the green and healthy development of the aquaculture industry. Therefore, there is an urgent need for green transformation and upgrading of aquaculture, and the development of efficient tailwater treatment technologies and equipment.

[0004] Currently, marine aquaculture tailwater treatment faces technical bottlenecks and systemic challenges. Technically, high salinity inhibits microbial activity. Furthermore, tailwater from aquaculture farms typically has a salinity below 32‰, so tailwater with a salinity between 22‰ and 32‰ is generally considered high-salinity. Traditional biochemical methods remove less than 30% of dissolved nitrogen and phosphorus. High-efficiency technologies like membrane bioreactors (MBRs) are difficult to popularize because equipment investment accounts for over 30% of operating costs. Regulatory gaps exist, with idle rates exceeding 50% for treatment facilities in some regions, and small-scale aquaculture operators lack policy support. Regarding environmental risks, antibiotic residues and nitrogen and phosphorus emissions in tailwater (total nitrogen concentrations can reach 15.1 mg / L) directly contribute to offshore eutrophication and red tides. While ecological treatment technologies such as bacterial-algal symbiosis show promise, poor technical adaptability (significant differences in tailwater characteristics between industrial and pond aquaculture) and a long payback period (3-5 years) continue to hinder the green development of the industry.

[0005] Ecological floating bed technology currently shows promising application prospects in marine aquaculture tailwater treatment. Through plant absorption and microbial degradation, it can effectively remove pollutants such as nitrogen and phosphorus from tailwater (removal rates can reach 40%-60%), with advantages such as low investment costs and zero secondary pollution. However, this technology still has significant drawbacks: First, high salinity inhibits plant growth, and existing salt-tolerant plant species only account for approximately 30% of applicable species. Second, its effectiveness against dissolved pollutants (such as antibiotic residues) is limited, and the floating bed requires a coverage rate of 15%-20% to ensure treatment efficiency, which is difficult to achieve in actual aquaculture ponds. Furthermore, the seasonal wilting of floating bed plants can lead to fluctuations in treatment effectiveness. Because most plants have distinct rhythmic growth patterns, the degradation efficiency of ecological floating beds can drop by over 50% in winter. Summary of the Invention

[0006] In response to the problem that existing marine aquaculture tail water contains high levels of pollutants such as nitrogen and phosphorus, and existing biological treatment methods are difficult to adapt to high-salinity environments, the present invention provides a multi-trophic level ecological purification system for high-salinity aquaculture tail water. Through the decomposition action of multi-level microorganisms (aerobic, facultative anaerobic bacteria), combined with plant roots and matrix adsorption, it can efficiently degrade organic pollutants and achieve the coordinated removal of complex pollutants.

[0007] Based on the technical effects achieved, the present invention provides the following technical solutions: In a first aspect, the present invention provides a multi-trophic level ecological purification system for high-salinity aquaculture tail water, wherein the purification system is an integrated pond having an inlet and an outlet, and the pond body is divided into a water-emerging area, a floating bed area, and a submerged area; A planting matrix for planting emergent plants is provided in the emergent area, wherein the planting matrix is volcanic rock mixed with humus soil; A polyethylene floating bed is set up in the floating bed area, and seahorse teeth are planted on the floating bed; Net cages for green algae to attach and grow are set up in the submerged area.

[0008] In view of the characteristics of existing marine aquaculture tail water with high content of pollutants such as nitrogen, phosphorus, COD, and high salinity, the present invention is designed to realize a synergistic mechanism for sewage treatment through a combination model of "emergent plants-floating bed plants-submerged algae".

[0009] The above-mentioned water-emerging area; The roots of emergent plants form an aerobic-anoxic gradient environment by secreting oxygen. The aerobic zone is located within 0-5 mm of the root surface, with dissolved oxygen (DO) > 2 mg / L, which promotes ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) to convert NH4 + Oxidized to NO2 - and NO3 -The anoxic zone is located outside the root system, with DO < 0.5 mg / L. Denitrifying bacteria use organic acids secreted by emergent plants as carbon sources to convert NO3 - It is reduced to N2O or N2 escapes, thereby achieving the degradation of nitrogen in the aquaculture tail water.

[0010] Furthermore, the emergent plants include but are not limited to Spartina alterniflora, cattail, water chestnut, lotus, water celery, wild rice stem or cattail. In one embodiment verified by the present invention, the emergent plant is Spartina alterniflora. The soluble sugars (glucose, sucrose) and phenolic substances secreted by the roots of Spartina alterniflora can provide a carbon source for nitrifying bacteria, improve the expression efficiency of the amoA gene of AOB, induce the expression of the nirS / nirK genes of denitrifying bacteria, promote nitrite reduction, and inhibit the activity of methanogens, avoiding the decrease in denitrification efficiency caused by carbon source competition. In the above embodiment, the planting density of Spartina alterniflora is 16 to 20 plants / m², and further 18 plants / m 2 .

[0011] In the above-mentioned planting matrix, the volcanic rock has a porous structure, which provides a high surface area for the cultivation of nitrifying bacteria in the water. The surface of the volcanic rock is positively charged, which is conducive to the fixation and growth of microorganisms. It has strong hydrophilicity and can convert NO2 and NH4 produced in the water for various reasons, which are extremely toxic to vertebrates, into NO3 with relatively low toxicity, which can greatly improve the water quality. In addition, the volcanic rock can be easily separated from the humus soil matrix, and only the volcanic rock needs to be replaced regularly during later maintenance.

[0012] Furthermore, the mass ratio of the volcanic rock to the humus soil is 6:4; furthermore, it is 6:5.

[0013] Furthermore, the emergent water area uses a floating island as a carrier, and the floating island is combined by a floating basin and a floating plate; a plurality of floating plates are connected to form the floating island body, and a socket for accommodating the floating basin is provided in the center of the floating plate; the floating basin is used to carry emergent plants and planting substrates, and has a through hole at the bottom. When in working state, the bottom of the floating basin is immersed in the aquaculture tail water.

[0014] The above-mentioned floating bed area: In an environment with a salinity of 2‰-3.5%, the root system of seahorse teeth secretes oxygen to promote the decomposition of glycogen by polyphosphate bacteria, thus enhancing the aerobic phosphorus absorption capacity. The floating bed can serve as a microbial attachment matrix, and salt-tolerant bacteria and polyphosphate bacteria coexist to achieve synergistic denitrification and phosphorus removal. In addition, the root system of seahorse teeth forms an iron film and secretes extracellular polysaccharides to absorb PO4 in the water. 3- , combined with the excessive phosphorus uptake of phosphate-accumulating bacteria, phosphate precipitation is formed. At the same time, organic acids (citric acid, malic acid) secreted by the roots dissolve insoluble phosphorus in the soil, improving the phosphorus uptake efficiency of phosphate-accumulating bacteria.

[0015] Furthermore, the planting density of the seahorse teeth is 6 to 10 plants / m², and further, 8 plants / m².

[0016] Furthermore, the polyethylene floating bed is distributed at the four corners of the pond, and the floating bed has through holes with a diameter of 1 to 2 cm.

[0017] The above-mentioned submerged area: The green algae is selected from one or more of Ulva, Enteromorpha, Pseudomonas, Chlamydomonas, Spirogyra, and Umbelliferae; in one embodiment verified by the present invention, Ulva is used, and its advantages are mainly as follows: Ulva can coexist with diatoms and green algae, on the one hand, it can intercept suspended matter through the cage mesh, with an adsorption rate of >80%, and on the other hand, the biofilm system of Ulva and microalgae coexistence can degrade organic matter in the intercepted matter (COD removal rate >70%). In addition, Ulva preferentially absorbs NH4 + and PO4 3- , inhibiting excessive algae growth and reducing the water TN / TP ratio to below 5:1. The sulfobetaine secreted by Ulva can also promote the activity of sulfate-reducing bacteria, oxidizing H2S to elemental sulfur precipitation.

[0018] In addition, Ulva and the above-mentioned seahorse teeth can also form a plant-bacteria-algae symbiosis, which can significantly improve the water quality of aquaculture water, and appropriate density and reasonable combination can effectively promote the effect of plant restoration. 2+ The efficiency is >50%, and the seahorse root system secretes oxygen to inhibit red tide algae.

[0019] In some embodiments of the present invention, the water inlet is located in a corner of the pool, 20-30 cm above the water surface, and the outlet is located at the bottom of the pool diagonally opposite the inlet. Filters (pore size ≤ 5 mm) are required at both the inlet and outlet to intercept fish, aquatic plants, and benthic organisms.

[0020] The aquaculture tail water is treated by the above-mentioned purification system and is discharged or returned to the aquaculture pond for recycling after meeting the standards. If it does not meet the standards, it is recycled to the aeration tank for treatment.

[0021] A second aspect of the present invention provides an ecological purification method for marine aquaculture tail water, comprising using the ecological purification system of the first aspect to perform ex situ treatment on the aquaculture tail water to be treated.

[0022] The above-mentioned aquaculture tail water does not limit the aquaculture objects. The feasible aquaculture objects include fish farming, shrimp and crab farming, shellfish farming, algae farming or farming of marine delicacies such as sea cucumbers and abalone.

[0023] The aquaculture tail water to be treated is put into the water inlet, and the water retention time is at least 7 days. After the treated tail water is discharged through the outlet, it can enter the aquaculture pond for recycling, or it can meet the discharge standards after monitoring and compliance with the requirements of DB46 / 475-2023. If it does not meet the standards, it will be recycled to the aeration tank for treatment.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention first provides a multi-trophic level ecological purification system for high-salinity aquaculture tail water. The purification system utilizes the synergistic effect of three systems: the root system of Spartina alterniflora (nitrifying bacteria) - Hippophae rhamnoides (phosphate-accumulating bacteria) - Ulva (algae symbiosis). First, it adsorbs suspended matter in the aquaculture tail water based on physical interception. Then, based on the biofilm system of bacteria-algae symbiosis, it realizes the synergistic effect of phosphate-accumulating bacteria and denitrifying bacteria, strengthens the denitrification effect of microorganisms, and comprehensively realizes the synergistic removal of pollutants. 2. The ecological purification system boasts low maintenance costs. Maintenance personnel only need to regularly trim Spartina alterniflora and Ulva and replace volcanic rock fillers. Ulva and seahorse teeth are high-value feed ingredients, while Spartina alterniflora is a fundamental raw material for papermaking and weaving, and also provides abundant biomass for producing green dyes and energy. This multi-trophic-level biological ecological purification system, along with its enhanced, highly efficient treatment technology, combines natural ecological processes with artificial enhancements. Its core advantages lie in its eco-friendliness, low energy consumption, and high adaptability, resulting in low-cost and sustainable operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a schematic structural diagram of the ecological purification system for high-salinity aquaculture tail water described in the present invention. DETAILED DESCRIPTION

[0027] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] Aiming at the treatment of ectopic tailwater from raceway-type aquaculture ponds (external circulation) and multi-stage ecological ditch aquaculture ponds, a technical system focusing on multi-trophic-level ecological aquaculture and water purification is studied and constructed. An enhanced biological ecological tailwater purification device is constructed by combining bacterial oxygen denitrification and functional fillers, functional filter materials and other technologies. The present invention belongs to the technical field of marine aquaculture wastewater treatment, and specifically relates to a multi-stage purification device integrating emergent plants (Spartina alterniflora), floating bed plants (Hippocampus) and algae (Ulva), which is suitable for the circulation treatment of high-salinity aquaculture tailwater.

[0030] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0031] Example 1 In this embodiment, a multi-trophic ecological purification system for high-salinity aquaculture tailwater is provided. The purification system is an integrated square concrete structure (4m×4m×1.5m, length×width×depth), with a water inlet at the top and a water outlet at the bottom. The tank body is cast with C30 concrete (impermeability grade P6), and the inner wall is coated with an epoxy resin anti-corrosion layer. The tank body is provided with an undivided water area, a floating bed area, and a submerged area. The structure is as follows when viewed from above: Figure 1 shown.

[0032] The aforementioned inlet is located in a corner of the pond, 20–30 cm above the water surface, allowing for natural water inflow by gravity while also minimizing surface disturbance. The inlet is located at the bottom of the pond on the opposite corner. Filters (pore size ≤ 5 mm) are required at both the inlet and outlet to intercept fish, aquatic plants, and benthic organisms. In the emergent water area, two ecological floating islands, measuring 1m x 1m, are planted with emergent plants, located on either side of the ecological pond. The islands are secured to the shore by ropes with a diameter greater than 8mm. The islands are constructed using a combination of HDPE floats and square floats. The floats are secured to the floats' sockets, and the planting cavities are filled with ecological filler and aquatic plants.

[0033] The ecological floating island is constructed as follows: The main body of the island is made of several square floating plates (33cm side, 6cm thick). The plates have a central socket for securing the floating basins, with nine per square meter. Connection holes are located at the four corners for bolts or nylon ropes to connect or secure the basins. The basins are inverted frustums (5cm thick), with an upper diameter slightly larger than the sockets and a lower edge extending beyond the plates to immerse in the aquaculture wastewater. They are made of a high-molecular-weight, high-density synthetic material. Several small holes are located at the bottom of the basins.

[0034] The ecological filler in the floating basin consists of volcanic rock (particle size 3-5cm) mixed with humus (15cm thick). The emergent plant is Spartina alterniflora, with a density of 18 / m². Aquaculture tailwater is allowed to come into contact with the roots of the Spartina alterniflora and the planting medium through holes in the bottom of the floating basin. Under ideal water levels, the roots and planting medium are located 0.1-0.3m below the water surface.

[0035] In the floating bed area, four square polyethylene floating plates are arranged at the four corners of the pool. The size of the floating plates is length × width = 1m × 1m, thickness is 5cm, and the total floating bed area is 4m 2 Each board is pre-drilled with holes (1cm-Φ2cm). Seahorse teeth are planted on the floating boards at a density of 8 plants / m². The floating bed can also serve as a substrate for microbial attachment.

[0036] In the submerged area, cages for Ulva growth are set up. These cages use stainless steel as their rigid frames. They measure 2 x 1 m in length and width and are 20–30 cm high. Two cages are located on the upper and lower sides of the pond and sunk to the bottom. Several mesh sheets are suspended inside the cages. The four corners of the mesh sheets can be connected to the frames with rolled strips or with lead weights suspended from the bottom to ensure the mesh sheets are spread vertically, reducing dead spots caused by wrinkles. Before cultivation, the mesh sheets are sprayed with 1% alginate, which forms a sticky layer after drying, improving the efficiency of Ulva attachment. The mesh pores are 2–4 cm in diameter to ensure water flow and uniform light distribution. Four Ulva plants are inoculated per square meter of mesh to ensure uniform attachment.

[0037] A microporous aeration device with a power of 0.5-1 kW / mu is installed in the center of the pond to increase the dissolved oxygen in the aquaculture tail water and avoid the problem of insufficient dissolved oxygen caused by high-density aquaculture, decomposition of leftover bait or excrement that aggravates oxygen consumption, and low temperature.

[0038] The operation and management of the above purification system are as follows: Harvesting strategy: Harvest Spartina alterniflora once every three months (retain 1 / 2 height), and prune Ulva monthly (coverage ≤ 40%); volcanic rock filler is removable and replaceable.

[0039] Replanting measures: Supplement cold-resistant Ulva in winter to maintain winter purification function.

[0040] Performance Characterization 1. Research Methods 1. Aquaculture tail water purification effect Three sampling points were set up in the pool (water inlet, water outlet, and pool center), and three parallel samples were measured for each water quality index, and the average value was taken as the final result.

[0041] Water samples were collected and tested every 5 days to determine TN, TP, COD, ammonia nitrogen and pH values.

[0042] COD removal rate, total phosphorus removal rate: TN was determined by potassium persulfate digestion ultraviolet spectrophotometry, TP was determined by molybdenum antimony spectrophotometry, COD was determined by rapid closed catalytic digestion method, ammonia nitrogen was determined by Nessler's reagent spectrophotometry, and pH was determined by glass electrode method.

[0043] The removal rate of each indicator is calculated according to the following formula: L= C0-C i / C0×100% where C0 is the initial concentration, C i is the concentration after treatment.

[0044] 2. Upper limit of salinity tolerance of ecological purification system The salinity tolerance limit of the ecological purification system was analyzed by combining gradient salt stress experiments with plant physiological responses. The research methods are as follows: (1) Preparation of gradient salt solution: Analytical grade NaCl and CaCl2 were added to deionized water to prepare the basic salt solution, which was diluted step by step to obtain the gradient salt solution (10‰, 20‰, 30‰, 40‰). The conductivity meter was calibrated with standard seawater to ensure that the salinity error was less than ±2‰.

[0045] (2) Healthy plants were randomly divided into a control group and an experimental group. The experimental group consisted of Spartina alterniflora + Hippocampus + Ulva; the control group consisted of single plant groups: Spartina alterniflora group / Hippocampus group / Ulva group; the combination groups consisted of Spartina alterniflora + Hippocampus / Spartina alterniflora + Ulva / Hippocampus + Ulva; the blank group consisted of no plants, with ≥30 plants in each group and three replicates. Salt was applied in stages so that the salt concentration in the water environment increased in the following gradient: 10‰ → 20‰ → 30‰ → 40‰, with each gradient separated by 24 hours.

[0046] (3) Determination of plant indicators in the control and experimental groups Morphological indicators: Measure plant height and number of leaves with a ruler every day. Physiological and biochemical indicators: Chlorophyll content (acetone extraction method), proline content (sulfosalicylic acid method), and SOD activity (nitroblue tetrazolium method) were measured weekly.

[0047] (4) Data analysis: SPSS 26.0 was used to perform one-way analysis of variance (ANOVA) with Duncan multiple comparisons (p < 0.05). R language was used to construct a random model and analyze the key salt tolerance evaluation indicators.

[0048] 2. Research Results 1. Aquaculture tail water purification effect Through the synergistic action of the three systems of "nitrification by the root system of Spartina alterniflora, phosphorus accumulation by Hippophae rhamnoides, and symbiosis by Ulva spp.," the removal rates of total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) achieve a cumulative improvement over the optimal effects of a single plant, with ammonia nitrogen and inorganic phosphorus removal rates reaching 100%. This combination, through the functional complementarity of "denitrification-phosphorus removal-heavy metal adsorption," constructs a triple purification system of "physical interception + biological absorption + microbial degradation," achieving the synergistic removal of multiple types of pollutants. Through functional complementarity and synergistic mechanisms, the three plants significantly outperform single plants or pairwise combinations in terms of pollutant removal efficiency, salinity tolerance, economic benefits, and system operational stability. They successfully achieve the triple goals of "high-efficiency purification, low-cost operation and maintenance, and resource utilization," providing the optimal technical solution for the ecological treatment of high-salinity aquaculture effluents.

[0049] 2. Salinity tolerance results Through the above experiments, it was found that the system can treat aquaculture tail water with a salinity tolerance below 33‰.

[0050] 3. Resource-based output Direct effect: Reduced operation and maintenance costs: Annual labor maintenance costs are reduced by 60% (compared to traditional ecological ponds), and the filler replacement cycle is extended to 2 years (traditional process 1 year).

[0051] Resource output: Annual plants such as Spartina alterniflora and Ulva produce biomass, which can also be processed into feed, with an output value of about 12,000 yuan per mu. The protein content of seahorse teeth is about 18%, which can be eaten and also processed into feed.

[0052] All three plants pose no risk of biological invasion, seahorse teeth are edible, and all three can be processed into feed; reducing the use of chemical agents by 80% and avoiding secondary pollution.

[0053] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A multi-trophic level ecological purification system for high-salinity aquaculture tail water, characterized in that: The purification system is an integrated pond with a water inlet and a water outlet, and the pond body is divided into a water-emerging area, a floating bed area and a submerged area; The emergent water area uses a floating island as a carrier. The floating island is a combination of a floating basin and a floating board. Several floating boards are connected to form the main body of the floating island. The center of the floating board has a socket for accommodating the floating basin. The floating basin is used to carry emergent water plants and planting substrates. The bottom has a through hole. When in operation, the bottom of the floating basin is immersed in the aquaculture tail water. The planting substrate is volcanic rock mixed with humus soil. A polyethylene floating bed array is set up in the floating bed area, and seahorse teeth are planted on the floating bed; Net cages for green algae to attach and grow are set up in the submerged area.

2. The multi-trophic level ecological purification system for high-salinity aquaculture tail water according to claim 1, characterized in that: The emergent plant is Spartina alterniflora, and the planting density is 16 to 20 plants / m².

3. The multi-trophic level ecological purification system for high-salinity aquaculture tail water according to claim 1, characterized in that: In the emergent water area, the mass ratio of the volcanic rock to the humus soil is 6:4-7.

4. The multi-trophic level ecological purification system for high-salinity aquaculture tail water according to claim 1, characterized in that: The planting density of the seahorse teeth is 6 to 10 plants / m².

5. The multi-trophic level ecological purification system for high-salinity aquaculture tail water according to claim 1, characterized in that: The polyethylene floating bed is distributed at the four corners of the pond and has through holes with a diameter of 1 to 2 cm.

6. The multi-trophic level ecological purification system for high-salinity aquaculture tail water according to claim 1, characterized in that: In the submerged area, the green algae is Ulva.

7. The multi-trophic level ecological purification system for high-salinity aquaculture tail water according to claim 1, characterized in that: The cage uses stainless steel as the frame and is sunk to the bottom of the pond. Several meshes are hung inside the cage. The meshes are sprayed with 1% alginate before cultivation, which forms a sticky layer after drying. The mesh pore size is 2-4 cm.

8. An ecological purification method for marine aquaculture tail water, characterized in that: The method comprises using the ecological purification system described in any one of claims 1 to 7 to perform ex situ treatment on the aquaculture tail water to be treated.

9. The ecological purification method according to claim 8, characterized in that: The aquaculture tail water is the aquaculture tail water of fish aquaculture, shrimp and crab aquaculture, shellfish aquaculture, algae aquaculture or sea cucumber, abalone or other marine treasures aquaculture; The aquaculture tail water to be treated is put into the water inlet, and the water retention time is at least 7 days. The treated tail water enters the aquaculture pond for recycling or discharge in compliance with the standards. If it does not meet the standards, it will be circulated to the aeration tank for treatment.

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