A method for treating tail water of circulating water aquaculture in a land-based circular pond

Abstract

The application discloses a kind of land-based circular pool circulating water aquaculture tail water treatment methods, comprising (1) pretreatment, (2) precipitation and aeration, (3) secondary purification: water discharged from the sedimentation tank is sequentially through the porous filter material purification zone and biological purification zone of secondary purification tank, the biological purification zone is put into purification accelerator, (4) water quality detection: the water after purification is detected, if it is qualified, then it is discharged into the reservoir for standby, and then reaches the breeding pond through the water inlet system, to realize the recycling of aquaculture tail water.The land-based circular pool circulating water aquaculture tail water treatment method of the application is scientific and reasonable, after pretreatment of aquaculture tail water, precipitation, aeration, porous filter material purification and biological purification through secondary purification tank, and through purification accelerator to improve the purification efficiency and purification effect of aquaculture tail water, to realize the recycling of aquaculture tail water, improve resource utilization efficiency, and save the cost of aquaculture.

Description

Technical Field

[0001] This invention belongs to the field of recirculating aquaculture technology, and particularly relates to a method for treating wastewater from land-based circular pond recirculating aquaculture. Background Technology

[0002] Land-based circular pond recirculating aquaculture is a modern aquaculture technology that uses circular ponds built on land and equipped with a recirculating water system to achieve high-density, intensive aquaculture. Compared with traditional flow-through aquaculture and cage aquaculture, land-based circular pond recirculating aquaculture equipment has a higher degree of automation, occupies less land, and has a higher yield per unit volume of water. However, with the large-scale application of land-based circular pond recirculating aquaculture, wastewater treatment has become an urgent industrial problem to be solved.

[0003] Chinese patent document (application number: CN202111068032.1) discloses a land-based circular pond recirculating aquaculture wastewater treatment system and method. This system utilizes a sedimentation tank, a primary filter dam, a subsurface flow wetland tank, a secondary filter dam, a biological purification tank, a third-stage filter dam, and a storage tank arranged sequentially according to the water flow direction to effectively treat aquaculture wastewater through multiple stages. This improves the efficiency of wastewater treatment and resource utilization, reduces water consumption and water quality control costs during the aquaculture process, and increases aquaculture profits. However, the wastewater treatment efficiency is relatively low, and the treatment time is long.

[0004] A Chinese journal article titled "Introduction to a Land-Based Circular Pond Recirculating Aquaculture Wastewater Treatment System" (China Fisheries, 2024, No. 4) discloses a land-based circular pond recirculating aquaculture wastewater treatment system. This system includes a circular aquaculture pond, an inlet and outlet system, an aeration system, and a wastewater treatment system. The wastewater treatment system comprises a sedimentation tank, a primary filtration dam, an aeration tank, a secondary filtration dam, and a biological purification tank. After multi-stage effective treatment by this system, the aquaculture wastewater can be returned to the aquaculture area via a water supply channel for recycling, or it can be directly discharged into natural water bodies. The wastewater treatment system primarily purifies the aquaculture wastewater by introducing aquatic animals such as snails, clams, silver carp, and bighead carp, and by setting up floating biological beds to cultivate aquatic plants such as water spinach and water lilies. Alternatively, appropriate aquatic plant species can be selected according to local conditions, or biological treatment methods using porous adsorption media such as expanded clay pebbles and volcanic rock can be employed. Biological purification ponds mainly use aquatic plants and animals to absorb ammonia nitrogen, nutrients and other substances in the water to purify the wastewater. However, the utilization rate of nitrogen and phosphorus in the wastewater by aquatic plants and animals is low, resulting in poor treatment effect.

[0005] A study published in the *Journal of Agricultural Resources and Environment* investigated the purification capacity of 29 aquatic plant species for rural domestic sewage. The results showed that, over a 75-day experimental period, aquatic plants improved the purification rates of total nitrogen (TN), ammonia nitrogen (NH3-N), total phosphorus (TP), chemical oxygen demand (CODCr), and suspended solids (SS). However, the purification efficiency of aquatic plants decreased, and the purification tended to saturate over time. Summary of the Invention

[0006] The purpose of this invention is to provide a land-based circular pond recirculating aquaculture wastewater treatment method that effectively improves the purification efficiency and effect of aquaculture wastewater by using a purification promoter, thereby realizing the recycling of aquaculture wastewater.

[0007] To achieve the above objectives, the present invention employs the following technical effects:

[0008] According to one aspect of the present invention, a method for treating wastewater from a land-based circular recirculating aquaculture system is provided, comprising the following steps:

[0009] (1) Pretreatment: After pretreatment, the upper and middle layers of the aquaculture wastewater from the aquaculture pond are discharged into the sedimentation tank.

[0010] (2) Sedimentation and aeration: After sedimentation, the upper layer of water in the sedimentation tank enters the aeration tank through the primary filtration dam, and then enters the purification tank after aeration.

[0011] (3) Secondary purification: Water discharged from the sedimentation tank passes sequentially through the porous filter media purification zone and the biological purification zone of the secondary purification tank, where a purification promoter is added to the biological purification zone.

[0012] (4) Water quality testing: The purified water is tested for water quality. If the test is qualified, it is discharged into the storage tank for later use, and then reaches the breeding pond through the water intake system to realize the recycling of breeding tail water.

[0013] Preferably, the biological purification zone is equipped with aquatic plants and algae, and the amount of purification promoter added is 0.01-1% of the required purified water volume. The aquatic plants are one or more of emergent, floating, or submerged plants; emergent plants include, but are not limited to, reeds, cattails, variegated reed, and canna lilies; floating-leaved plants include, but are not limited to, water lilies; floating plants include, but are not limited to, water hyacinths; submerged plants include, but are not limited to, Elodea nuttallii and Vallisneria natans; algae include, but are not limited to, Chlorella vulgaris, Spirulina, Scenedesmus stenoptera, Asterella spp., and Algae.

[0014] Preferably, the purification promoter is mainly composed of PGPR, nano-SiO2 and EPS, and the mass ratio of PGPR, nano-SiO2 and EPS is 1:0.1-1:1-10.

[0015] Preferably, the pretreatment involves collecting the aquaculture wastewater from the aquaculture pond using a sludge collection well, separating large particulate matter and suspended solids in the wastewater through a screen or sieve, and then discharging the separated upper and middle layers of water into a sedimentation tank.

[0016] Preferably, the primary filter dam is filled with filter media.

[0017] Preferably, the filter media is activated carbon or diatomaceous earth.

[0018] Preferably, the porous filter media purification zone is provided with a first porous filter media layer and a second porous filter media layer, with the second porous filter media layer disposed above the first porous filter media layer; the first porous filter media layer is composed of ceramsite, coconut coir, and palm fiber.

[0019] Preferably, the preparation method of the first porous filter material layer is as follows: take ceramic particles of different particle sizes with a volume ratio of 1:3-4 and mix them evenly to obtain ceramic particles; add 4-5 mm of coconut coir to the ceramic particles, mix them, and then wrap and press them with palm fiber to form a filter filler layer.

[0020] Preferably, the volume ratio of the porous filter media purification zone to the biological purification zone is 1:3-5.

[0021] Preferably, the biological purification zone is aerated using an intermittent aeration method with an aeration-to-stop ratio of 1:1-3.

[0022] In summary, the present invention adopts the above technical solution, and the present invention has the following technical effects:

[0023] 1. The land-based circular pond recirculating aquaculture wastewater treatment method of the present invention is scientific and reasonable. After pretreatment, the aquaculture wastewater undergoes sedimentation and aeration. After purification by porous filter media and biological purification in a secondary purification tank, a purification promoter is used to obtain aquaculture wastewater with high purification efficiency and good effect, thereby realizing the recycling of aquaculture wastewater and saving aquaculture costs.

[0024] 2. The purification promoter used in this invention is composed of PGPR, nano-SiO2 and EPS. By adding the purification promoter to the biological purification zone, the absorption and purification of nutrients and ammonia nitrogen elements such as total nitrogen, ammonia nitrogen, total phosphorus, chemical oxygen demand and suspended solids in the aquaculture wastewater can be effectively improved.

[0025] PGPR, short for Plant Rhizosphere Promoting Bacteria, refers to a class of beneficial bacteria that live near plant roots and promote plant growth through various mechanisms. PGPR can convert insoluble phosphorus in aquaculture wastewater into a form that can be absorbed by aquatic plants and algae in the biological purification zone, accelerating the absorption of phosphorus from the wastewater by aquatic plants and algae. At the same time, PGPR can produce substances similar to plant growth hormones, promoting root development, enhancing the diversity and stability of the rhizosphere community, and further improving the purification effect of aquatic plants and algae. Through the interaction between PGPR and plants, the absorption and utilization of mineral nutrients by plants can be improved, harmful organisms can be inhibited, and thus plant growth can be promoted.

[0026] Nano-silica has strong adsorption and adhesion capabilities. The hydroxyl radicals on the surface of nano-silica can combine with polar hydrophobic organic substances in plants, increasing the adhesion of the purification promoter in aquatic plants and algae, and increasing the retention time of the purification promoter in the plant roots. This allows the plant to exert its purification effect for a longer period of time, thereby improving the purification efficiency.

[0027] EPS is a type of high-molecular-weight viscous substance, also known as extracellular polymeric material. It is mainly composed of high-molecular-weight organic substances such as polysaccharides, proteins, nucleic acids, and phospholipids, with polysaccharides and proteins being the main components. EPS can change the surface characteristics of bacterial flocs and the physical properties of granular sludge in aquaculture wastewater, promoting coagulation and structural stability. At the same time, it enriches nutrients such as ammonia nitrogen, nutrient solution, and phosphorus in the biological purification zone, thereby improving the treatment efficiency of aquaculture wastewater.

[0028] The synergistic effect of EPS, nano-silica, and PGPR has significant effects on aquaculture wastewater treatment and plant growth promotion. First, EPS, as a stabilizer in the purification promoter, can ensure that nano-silica is evenly dispersed in aquaculture wastewater, preventing its aggregation and thus enhancing the stability and application effect of nano-silica; the addition of nano-silica also improves the thermal stability of EPS. Secondly, EPS provides a protective layer for PGPR, helping microorganisms survive in the unfavorable environment of aquaculture wastewater under salt stress. PGPR can utilize the organic matter in EPS as a nutrient source, promoting its growth and activity. In addition, the metabolites of PGPR can also promote the synthesis of EPS, forming a mutually beneficial symbiotic cycle. Nano-silica acts as an attachment point for PGPR, promoting its colonization on the surface of plant roots. The metabolic activity of PGPR further alters the surface properties of nano-silica, thereby enhancing the interaction between PGPR and plant roots, improving the absorption and utilization of nutrients in aquaculture wastewater by plants. The synergistic effect of EPS and PGPR not only promotes plant growth but also improves plant stress resistance. Nano-silica enhances the removal effect of pollutants by adsorbing and fixing them. The combination of these three factors not only improves aquaculture wastewater but also enhances the purification effect and efficiency of aquatic plants and algae on aquaculture wastewater, providing effective technical support for the sustainable development of aquaculture.

[0029] 3. The land-based circular pond recirculating aquaculture method of the present invention can effectively remove suspended solids and organic pollutants in wastewater by filling the primary filter dam with activated carbon or diatomaceous earth as filter media, thus reducing the burden on subsequent treatment. At the same time, the treatment effect is further optimized by the porous filter media purification zone. This zone is composed of a porous filter media layer of ceramsite, coconut coir and palm fiber, which provides surface area for microbial attachment and growth, significantly improving purification efficiency.

[0030] 4. This invention employs intermittent aeration in the biological purification zone. By controlling the aeration-to-stop ratio of 1:1-3, the dissolved oxygen level is intelligently regulated. Together with the purification promoter, it promotes the metabolic activities of aquatic plants, algae, and microorganisms, effectively degrading nutrients and phosphorus in the aquaculture wastewater. The intermittent aeration method can effectively improve purification efficiency and reduce energy consumption while ensuring high-efficiency treatment. Attached Figure Description

[0031] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the invention, and these aspects of the invention can be implemented even without these specific details.

[0033] Example 1

[0034] Combination Figure 1 As shown, a method for treating wastewater from a land-based circular recirculating aquaculture system includes the following steps:

[0035] (1) Pretreatment: The aquaculture wastewater from the aquaculture pond is collected by a sludge collection well and then separated by a screen or sieve to separate large particles and suspended solids. The separated middle and upper layers of water are then discharged into a sedimentation tank.

[0036] (2) Sedimentation and aeration: After sedimentation, the upper layer of water in the sedimentation tank enters the aeration tank through the primary filter dam filled with activated carbon, and then enters the purification tank after aeration.

[0037] (3) Secondary purification: The water discharged from the sedimentation tank passes sequentially through the porous filter media purification zone and the biological purification zone of the secondary purification tank. The volume ratio of the porous filter media purification zone to the biological purification zone is 1:3, and the ceramsite is:

[0038] A purification accelerator is added to the biological purification zone, which is also home to reeds, canna lilies, chlorella, and spirulina. The purification accelerator is added at 0.01% of the required purified water volume. The accelerator consists of PGPR, nano-SiO2, and EPS, with a mass ratio of 1:0.1:1. In practical use, the three main components can be directly mixed evenly and then added to the biological purification zone in appropriate amounts. The porous filter media purification zone contains a first porous filter media layer and a second porous filter media layer, with the second layer positioned above the first. The first porous filter media layer consists of ceramsite, coconut coir, and palm fiber. The first porous filter media layer is prepared by mixing ceramsite particles of different particle sizes at a volume ratio of 1:3 to obtain mixed ceramsite particles with particle sizes of 7mm and 21mm. 4mm coconut coir is added to the ceramsite, and the mixture is then wrapped and pressed with palm fiber to form a filter media layer.

[0039] Intermittent aeration is used to aerate the biological purification zone, with an aeration-to-stop ratio of 1:1.

[0040] (4) Water quality testing: The purified water is tested for water quality. If the test is qualified, it is discharged into the storage tank for later use, and then reaches the breeding pond through the water intake system to realize the recycling of breeding tail water.

[0041] Example 2

[0042] A method for treating wastewater from a land-based circular recirculating aquaculture system includes the following steps:

[0043] (1) Pretreatment: The aquaculture wastewater from the aquaculture pond is collected by a sludge collection well and then separated by a screen or sieve to separate large particles and suspended solids. The separated middle and upper layers of water are then discharged into a sedimentation tank.

[0044] (2) Sedimentation and aeration: After sedimentation, the upper layer of water in the sedimentation tank enters the aeration tank through the primary filter dam filled with activated carbon, and then enters the purification tank after aeration.

[0045] (3) Secondary purification: The water discharged from the sedimentation tank passes through the porous filter media purification zone and the biological purification zone of the secondary purification tank in sequence. The volume ratio of the porous filter media purification zone to the biological purification zone is 1:4.5, and the ceramsite is:

[0046] A purification accelerator is added to the biological purification zone, which is also home to cattails, canna lilies, and spirulina. The amount of the purification accelerator added is 0.05% of the required purified water volume. The purification accelerator consists of PGPR, nano-SiO2, and EPS, with a mass ratio of PGPR, nano-SiO2, and EPS of 1:0.5:6. In actual use, the three main components of the purification accelerator can be mixed with water, starch, and other binders, pressed into granules, and then added to the biological purification zone. The porous filter media purification zone is equipped with a first porous filter media layer and a second porous filter media layer, with the second porous filter media layer positioned above the first porous filter media layer. The first porous filter media layer consists of ceramsite, coconut coir, and palm fiber. The preparation method of the first porous filter media layer is as follows: ceramsite particles of different particle sizes with a volume ratio of 1:3.5 are mixed evenly to obtain mixed ceramsite particles with particle sizes of 7mm and 24.5mm; 4.5mm coconut coir is added to the ceramsite, and after mixing, it is wrapped with palm fiber and pressed into a filter packing layer.

[0047] Intermittent aeration is used to aerate the biological purification zone, with an aeration-to-stop ratio of 1:2.

[0048] (4) Water quality testing: The purified water is tested for water quality. If the test is qualified, it is discharged into the storage tank for later use, and then reaches the breeding pond through the water intake system to realize the recycling of breeding tail water.

[0049] Example 3

[0050] A method for treating wastewater from a land-based circular recirculating aquaculture system includes the following steps:

[0051] (1) Pretreatment: The aquaculture wastewater from the aquaculture pond is collected by a sludge collection well and then separated by a screen or sieve to separate large particles and suspended solids. The separated middle and upper layers of water are then discharged into a sedimentation tank.

[0052] (2) Sedimentation and aeration: After sedimentation, the upper layer of water in the sedimentation tank enters the aeration tank through the primary filter dam filled with activated carbon, and then enters the purification tank after aeration.

[0053] (3) Secondary purification: The water discharged from the sedimentation tank passes sequentially through the porous filter media purification zone and the biological purification zone of the secondary purification tank. The volume ratio of the porous filter media purification zone to the biological purification zone is 1:5, and the ceramsite is:

[0054] A purification accelerator is added to the biological purification zone, which is also home to cattails, variegated reeds, spirulina, sceneggia, and chain algae. The purification accelerator is added at 1% of the required purified water volume. The accelerator consists of PGPR, nano-SiO2, and EPS in a mass ratio of 1:1:10. In practical use, the three main components can be mixed with water and starch binders, pressed into granules, and then added to the biological purification zone. The porous filter media purification zone contains a first porous filter media layer and a second porous filter media layer, with the second layer positioned above the first. The first porous filter media layer consists of ceramsite, coconut coir, and palm fiber. The first porous filter media layer is prepared by mixing ceramsite particles of different sizes at a volume ratio of 1:5 to obtain mixed ceramsite particles with diameters of 7mm and 35mm. 5mm coconut coir is added to the ceramsite, and the mixture is then wrapped with palm fiber and pressed into a filter media layer.

[0055] Intermittent aeration is used to aerate the biological purification zone, with an aeration-to-stop ratio of 1:3.

[0056] (4) Water quality testing: The purified water is tested for water quality. If the test is qualified, it is discharged into the storage tank for later use, and then reaches the breeding pond through the water intake system to realize the recycling of breeding tail water.

[0057] Example 4

[0058] A method for treating wastewater from a land-based circular recirculating aquaculture system includes the following steps:

[0059] (1) Pretreatment: The aquaculture wastewater from the aquaculture pond is collected by a sludge collection well and then separated by a screen or sieve to separate large particles and suspended solids. The separated middle and upper layers of water are then discharged into a sedimentation tank.

[0060] (2) Sedimentation and aeration: After sedimentation, the upper layer of water in the sedimentation tank enters the aeration tank through the primary filter dam filled with activated carbon, and then enters the purification tank after aeration.

[0061] (3) Secondary purification: The water discharged from the sedimentation tank passes through the porous filter media purification zone and the biological purification zone of the secondary purification tank in sequence. The volume ratio of the porous filter media purification zone to the biological purification zone is 1:4.5, and the ceramsite is:

[0062] A purification promoter is added to the biological purification zone, which is also home to cattails, canna lilies, and spirulina. The purification promoter is added at 0.08% of the required purified water volume. The promoter consists of PGPR, nano-SiO2, and EPS, with a mass ratio of 1:0.5:6. The three main components can be directly mixed evenly and then added to the biological purification zone in appropriate amounts. A first porous filter layer and a second porous filter layer are provided in the porous filter media purification zone, with the second layer positioned above the first. The first porous filter layer consists of ceramsite, coconut coir, and palm fiber. The first porous filter layer is prepared by mixing ceramsite particles of different sizes at a volume ratio of 1:3.5 to obtain mixed ceramsite particles with particle sizes of 7mm and 24.5mm. 4.5mm coconut coir is added to the ceramsite, and the mixture is then wrapped and pressed with palm fiber to form a filter media layer.

[0063] Intermittent aeration is used to aerate the biological purification zone, with an aeration-to-stop ratio of 1:2.

[0064] (4) Water quality testing: The purified water is tested for water quality. If the test is qualified, it enters the water storage tank and then the water intake system of the breeding pond to realize the circulation of the breeding tail water.

[0065] Comparative Example 1

[0066] It is basically the same as Example 2, except that the primary filter dam is not filled with activated carbon.

[0067] Comparative Example 2

[0068] It is basically the same as Example 2, except that the porous filter media purification zone does not have a first porous filter media layer.

[0069] Comparative Example 3

[0070] It is basically the same as Example 2, except that the porous filter media purification zone does not have a first porous filter media layer.

[0071] Comparative Example 4

[0072] It is basically the same as Example 2, except that no purification promoter is added to the biological purification zone.

[0073] Comparative Example 5

[0074] It is basically the same as Example 2, except that the purification promoter in the biological purification zone does not contain PGPR.

[0075] Comparative Example 6

[0076] It is basically the same as Example 2, except that the purification promoter in the biological purification zone does not contain nano-SiO2.

[0077] Comparative Example 7

[0078] It is basically the same as Example 2, except that EPS was not added to the purification promoter in the biological purification zone.

[0079] Comparative Example 8

[0080] It is basically the same as Example 2, except that the purification promoter in the biological purification zone is not intermittently aerated.

[0081] I. Purification Effect Test

[0082] A farm in Wuming District, Nanning City, Guangxi Zhuang Autonomous Region, was selected to conduct treatment experiments on aquaculture wastewater according to Examples 1-4 and Comparative Examples 1-8. During the purification process, water quality samples were taken from the biological purification zone at regular intervals, with 500 mL samples collected each time. The experimental period was 90 days, and the contents of suspended solids, COD, total nitrogen, ammonia nitrogen, and total phosphorus in the aquaculture wastewater were tested at 0, 30, 60, and 100 days after treatment.

[0083] (1) Before the treatment of aquaculture wastewater, i.e., on day 0 of treatment

[0084] Table 1. Relevant water quality indicators before aquaculture wastewater treatment

[0085]

[0086] (2) On the 30th day after the aquaculture wastewater treatment, water quality samples were taken and analyzed.

[0087] Table 2. Water quality indicators of aquaculture wastewater on day 30 after treatment.

[0088]

[0089] As shown in Table 2, compared with Comparative Example 4, Example 2 reduced the suspended solids content by 64.56%, COD content by 68.17%, total nitrogen content by 75.61%, ammonia nitrogen content by 55.32%, and total phosphorus content by 75%. This indicates that the land-based circular pond recirculating aquaculture wastewater treatment method of the present invention can improve the absorption and utilization of mineral nutrients by plants and effectively improve the purification efficiency.

[0090] Compared with Comparative Example 4, Comparative Example 5 showed a 19.62% reduction in suspended solids, a 31.13% reduction in COD, a 32.93% reduction in total nitrogen, a 12.77% reduction in ammonia nitrogen, and a 10% reduction in total phosphorus.

[0091] Compared with Comparative Example 4, Comparative Example 6 showed a 27.85% reduction in suspended solids, a 31.48% reduction in COD, a 17.07% reduction in total nitrogen, a 19.15% reduction in ammonia nitrogen, and a 25% reduction in total phosphorus.

[0092] Compared with Comparative Example 4, Comparative Example 7 showed a 15.19% reduction in suspended solids, a 27.83% reduction in COD, a 7.32% reduction in total nitrogen, a 14.89% reduction in ammonia nitrogen, and a 30% reduction in total phosphorus.

[0093] Compared to Comparative Example 4, Comparative Example 8 showed a 17.72% reduction in suspended solids, a 53.39% reduction in COD, a 63.41% reduction in total nitrogen, a 31.91% reduction in ammonia nitrogen, and a 50% reduction in total phosphorus. Data from Comparative Example 8 and Example 2 indicate that intermittent aeration, intelligent regulation of dissolved oxygen levels in the biological purification zone, and the combined effect of purification promoters on the metabolic activities of aquatic plants, algae, and microorganisms effectively degrade nutrients and phosphorus, thereby improving the purification efficiency of aquaculture wastewater.

[0094] It is evident that the land-based circular pool recirculating aquaculture wastewater treatment method of the present invention can significantly improve purification efficiency. The metabolites of PGPR promote the synthesis of EPS, forming a mutually beneficial cycle. Nano-silica serves as an attachment point for PGPR, promoting its colonization on the surface of plant roots. Furthermore, the metabolic activity of PGPR further alters the surface properties of nano-silica, thereby enhancing the interaction between PGPR and plant roots. This improves the absorption and utilization of nutrients in the aquaculture wastewater by plants, ultimately increasing the purification efficiency of the wastewater.

[0095] (3) On the 60th day after the aquaculture wastewater treatment, water quality samples were taken and analyzed.

[0096] Table 3. Water quality indicators of aquaculture wastewater treated on day 60.

[0097]

[0098] As shown in Table 3, the treatment method of the present invention was still effective in purifying aquaculture wastewater on the 60th day after treatment.

[0099] (4) On the 100th day after the aquaculture wastewater treatment, water quality samples were taken and analyzed.

[0100] Table 4. Water quality indicators of aquaculture wastewater on day 100 after treatment.

[0101]

[0102] Table 2 shows the relevant water quality indicators of Example 2's aquaculture wastewater on day 30 after treatment, and Table 4 shows the relevant water quality indicators of Comparative Example 4's aquaculture wastewater on day 100 after treatment. It is evident that using the purification promoter of this invention achieves the same treatment effect as Comparative Example 4 (without the purification promoter) on day 100 after treatment on day 30. Table 4 shows that the purification effect of using the purification promoter of this invention is superior on day 100.

[0103] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for treating wastewater from land-based circular pond recirculating aquaculture systems, characterized in that: Includes the following steps: (1) Pretreatment: After pretreatment, the upper and middle layers of the aquaculture wastewater from the aquaculture pond are discharged into the sedimentation tank. (2) Sedimentation and aeration: After sedimentation, the upper layer of water in the sedimentation tank enters the aeration tank through the primary filtration dam, and then enters the purification tank after aeration. (3) Secondary purification: Water discharged from the sedimentation tank passes sequentially through the porous filter media purification zone and the biological purification zone of the secondary purification tank, where a purification promoter is added to the biological purification zone. (4) Water quality testing: The purified water is tested for water quality. If the test is qualified, it is discharged into the storage tank for later use, and then reaches the breeding pond through the water intake system to realize the recycling of breeding tail water. The purification accelerator is composed of PGPR, nano-SiO2 and EPS, and the mass ratio of PGPR, nano-SiO2 and EPS is 1:0.1-1:1-10.

2. The method for treating wastewater from a land-based circular pond recirculating aquaculture system according to claim 1, characterized in that: The biological purification zone is equipped with aquatic plants and algae, and the amount of purification promoter added is 0.01-1% of the required amount of purified water.

3. The method for treating wastewater from a land-based circular pond recirculating aquaculture system according to claim 1, characterized in that: The pretreatment involves collecting the aquaculture wastewater from the aquaculture pond using a sludge collection well, separating large particles and suspended solids in the wastewater through a grid or screen, and then discharging the separated upper and middle layers of water into a sedimentation tank.

4. The method for treating wastewater from a land-based circular pond recirculating aquaculture system according to claim 1, characterized in that: The primary filter dam is filled with filter media.

5. The method for treating wastewater from a land-based circular pond recirculating aquaculture system according to claim 4, characterized in that: The filter media is activated carbon or diatomaceous earth.

6. The method for treating wastewater from a land-based circular pond recirculating aquaculture system according to claim 1, characterized in that: The porous filter media purification zone is provided with a first porous filter media layer and a second porous filter media layer, with the second porous filter media layer disposed above the first porous filter media layer; the first porous filter media layer is composed of ceramsite, coconut coir and palm fiber.

7. The method for treating wastewater from a land-based circular pond recirculating aquaculture system according to claim 6, characterized in that: The preparation method of the first porous filter material layer is as follows: take ceramic particles of different particle sizes with a volume ratio of 1:3-4 and mix them evenly to obtain ceramic particles; add 4-5 mm of coconut coir to the ceramic particles, mix them, and then wrap them with palm fiber and press them into a filter filler layer.

8. The method for treating wastewater from a land-based circular pond recirculating aquaculture system according to claim 6, characterized in that: The volume ratio of the porous filter media purification zone to the biological purification zone is 1:3-5.

9. The method for treating wastewater from a land-based circular pond recirculating aquaculture system according to claim 5, characterized in that: Intermittent aeration is used to aerate the biological purification zone, with an aeration-to-stop ratio of 1:1-3.

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