Culture tail water circulation purification device and purification method based on microorganism fixed culture

Abstract

The invention discloses a culture tail water circulation purification device and purification method based on microorganism fixed culture, the purification device comprises a first water flow branch and a second water flow branch, the first water flow branch and the second water flow branch are mutually isolated and arranged in parallel, and the first water flow branch and the second water flow branch are respectively communicated with a culture pond for circulation. The purification method comprises the following steps: S1, constructing a first water flow branch and a second water flow branch; s2, directional cultivation of microbial flora is carried out; and S3, immobilizing the microbial flora on the ceramsite layer. The method is suitable for polluted water bodies with medium and low nutrition levels by depending on an ecological purification technology, and has the characteristics of energy conservation, low operation cost, no need of professional management, simplicity in operation and maintenance, formation of an ecological landscape effect and the like.

Description

Technical Field

[0001] The invention relates to the field of aquaculture, and in particular to an aquaculture tail water circulation purification device and a purification method based on microbial culture. Background Art

[0002] Aquaculture tailwater contains a large amount of nutrients and microorganisms. If it is discharged without treatment, it will lead to the deterioration of water quality in surrounding waters. The concentration of soluble nutrients and organic matter in aquaculture tailwater generally does not meet the load required by conventional activated sludge treatment technology. At the same time, its high salinity increases the difficulty of using traditional microbial methods to treat aquaculture tailwater. Traditional microbial treatment technology generally includes screens, sand filters, primary sedimentation tanks, aeration tanks, secondary sedimentation tanks, disinfection tanks, etc., with high construction costs and high operating energy consumption, and must be managed, operated and maintained by professionals for a long time. Summary of the invention

[0003] In order to overcome the above-mentioned defects, the present invention provides an aquaculture tail water circulation purification device and purification method based on the fixed cultivation of microorganisms, which relies on ecological purification technology to adapt to polluted water bodies with medium and low nutrient levels. It also has the characteristics of energy saving, low operating cost, no need for professional personnel management, simple operation and maintenance, and the formation of ecological landscape effects.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A circulating purification device for aquaculture tail water based on microbial fixed cultivation comprises a first water flow branch and a second water flow branch, the first water flow branch and the second water flow branch are isolated from each other and arranged in parallel, the first water flow branch comprises a sedimentation treatment unit and an undercurrent treatment unit arranged in sequence, the aquaculture tail water of the aquaculture pond flows through the sedimentation treatment unit and the undercurrent treatment unit in sequence and returns to the aquaculture pond for circulation, the second water flow branch comprises a sedimentation treatment unit, a surface flow treatment unit and an undercurrent treatment unit arranged in sequence, the aquaculture tail water of the aquaculture pond flows through the sedimentation treatment unit, the surface flow treatment unit and the undercurrent treatment unit in sequence and returns to the aquaculture pond for circulation;

[0006] The surface flow treatment unit includes a soil layer below and a surface water layer above. Salicornia herba is planted in the surface water layer. The subsurface flow treatment unit is provided with a zeolite layer, a ceramsite layer, a gravel layer and a subsurface water layer from bottom to top. The aquaculture tail water flows through the subsurface water layer, the gravel layer, the ceramsite layer and the zeolite layer in sequence.

[0007] As an improvement, the culture of spotted mullet in the subsurface water layer is carried out at a rate of 20 fish / m 2 The stocking density is 5cm or above.

[0008] As an improvement, a floating bed is provided in the subsurface water layer, and the sea salicornia is planted in the floating bed. The floating bed made of ceramsite as the main aggregate is used to plant the sea salicornia according to the area ratio of 40% of the pool, and the external tender stems are harvested when the plants grow to more than 15 cm.

[0009] As an improvement, the culture of sandworms in the ceramsite layer is carried out at a rate of 20-30 pieces / m 3 The density of double-toothed or multi-toothed perinecrotizers with a size of more than 10 cm is released.

[0010] A method for circulating and purifying aquaculture tail water based on microbial cultivation, which uses the above purification device, comprises the following steps:

[0011] S1: construct the first water flow branch and the second water flow branch;

[0012] S2: Directed cultivation of microbial flora;

[0013] S3: Immobilize the microbial flora on the expanded clay layer.

[0014] As an improvement, in step S2, the directional cultivation of the microbial flora includes taking out the aquaculture sediment, filtering out the water, drying and grinding into powder, and high-temperature sterilization to obtain treated sediment, taking a mixed sample of fresh sediment and aquaculture water, inoculating it in a container filled with sterilized sand-filtered seawater, and after fully shaking in a water bath, transferring it to a container containing sterilized sand-filtered seawater with treated sediment for cultivation, using the culture solution as a seed solution, and transferring it into a sand-filtered seawater suspension containing treated sediment for expansion culture to obtain a Bacillus flora expansion culture solution.

[0015] As an improvement, in step S2, the directional cultivation of the microbial flora also includes taking a mixed sample of fresh sediment and aquaculture water, inoculating it in a nitrifying bacteria enrichment medium for cultivation, testing the nitrite nitrogen content every day, and supplementing NaNO when the test result is colorless. 2 To 50 mg / L, after supplementing 4 times, the bacterial cells were collected by low-speed centrifugation and re-added to the enrichment culture medium for cultivation. The enrichment culture process was repeated until the bacterial concentration reached the standard, and it was added as seed liquid to the new enrichment culture medium for expansion culture to obtain the nitrifying bacteria expansion culture liquid.

[0016] As an improvement, in step S3, the immobilization of the microbial flora includes selecting ceramsite with a specification of 2-3 cm, placing it in a culture medium for expanding the Bacillus flora, aerating and forming biofilms, taking out the ceramsite with biofilms, placing new ceramsite, and adding treated sediments, and repeating the previous process until a sufficient amount of ceramsite carriers for immobilizing the Bacillus flora are obtained.

[0017] As an improvement, in step S3, the immobilization of the microbial flora includes selecting ceramsite with a specification of 2-3 cm, placing it in a culture medium for expanding the nitrifying bacteria, and aerating and forming biofilms. During the biofilm formation process, the content of nitrite nitrogen is detected every day. When the content drops to 0, the ceramsite is taken out and washed with sand-filtered seawater until the cleaning liquid contains no nitrate nitrogen. Thereafter, the washed ceramsite is transferred to a culture medium for expanding the nitrifying bacteria, and biofilm formation is continued. After three consecutive transfers according to the aforementioned method, a ceramsite carrier for immobilizing the nitrifying bacteria is obtained.

[0018] Beneficial effects of the present invention:

[0019] 1. In the sedimentation treatment unit, most of the suspended particles are removed for preliminary treatment.

[0020] 2. In the surface flow treatment unit, some soluble nutrients and suspended particles that cannot be precipitated are removed through the colloidal adsorption of the soil layer, bacterial denitrification, and absorption by plant roots; before the surface water layer in the surface flow treatment unit enters the subsurface flow treatment unit, most of the dissolved organic matter and nutrients are removed under aeration and oxygenation conditions, so that the water quality meets the aquaculture water standards.

[0021] 3. In the subsurface treatment unit, the zeolite layer absorbs phosphorus in the aquaculture tail water, further reducing the phosphorus content of the water body; laying it on the bottom can provide a larger gap to prevent the bottom water outlet channel from being blocked by sediments, making dredging easier.

[0022] Regarding the expanded clay layer, zeolite can withstand the scouring of water flow and shear stress, making the water distribution uniform and the flow state stable, so that the soluble pollutants in the water body are in full contact with the bacterial biofilm on the surface of the expanded clay, which is conducive to the full adsorption and decomposition of the pollutants. At the same time, the dissolved oxygen in the water is evenly distributed in the filler layer to prevent the formation of hypoxic areas; the density of expanded clay is lower than that of water. When the system is running, it is suspended in water. Under the action of water flow, the expanded clay is constantly moving, so that there will be no sediment in the expanded clay layer, and the blockage of the expanded clay layer with small gaps is eliminated; the large specific surface area of ​​expanded clay is conducive to the enrichment of a large number of microorganisms, and finally a large area of ​​biofilm is formed as the main functional area for aquaculture wastewater treatment.

[0023] Regarding the gravel layer, since the density of expanded clay is lower than that of water, the buoyancy generated by the accumulation of a large amount of expanded clay will push part of the surface expanded clay out of the water, thus losing its water treatment function. The gravel is laid to press down the expanded clay layer so that it can be stably below the water surface. A large number of microorganisms accumulate on the expanded clay to form a stable biofilm, which is not good for human perception. The laying of the gravel layer can serve as an ecological landscape. The gravel layer can effectively prevent the influence of sun exposure on the biofilm of the expanded clay layer, and at the same time form a darkroom effect, preventing the growth of algae in the wetland, which is conducive to the stable operation of the water treatment system.

[0024] 4. The present invention greatly reduces the amount of water discharged and the amount of water consumed, thereby minimizing the environmental impact of aquaculture on the surrounding sea areas and striving to reduce the amount of sewage discharged to zero, that is, no longer discharging pollutants into external waters. At the same time, the first water flow branch and the second water flow branch are isolated from each other and arranged in parallel, which not only has the effect of coordinated purification, but can also be set as two independent comparative experimental devices to collect data.

[0025] 5. The present invention does not go through the traditional process of isolating, identifying and then cultivating a single strain. Instead, it directly uses enrichment culture medium to cultivate a large number of microbial flora in aquaculture water, and then prepares bacterial carriers through immobilized microbial technology. Finally, it uses a ceramsite layer to form a wetland microbial ecosystem with outstanding nitrification ability and the ability to degrade multiple pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is an overall schematic diagram of the aquaculture tail water circulation purification device.

[0027] Figure 2 This is a schematic diagram of the first water flow branch s1 of the aquaculture tail water circulation purification device.

[0028] Figure 3 It is a schematic diagram of the second water flow branch s2 of the aquaculture tail water circulation purification device.

[0029] In the figure: s1, the first water flow branch; s2, the second water flow branch; 1, sedimentation treatment unit; 11, water collection tank at the water inlet; 12, inclined plate sedimentation tank; 2, underflow treatment unit; 21, zeolite layer; 22, expanded clay layer; 23, gravel layer; 24, underflow water layer; 25, floating bed; 26, "L" type aeration pipe; 3, surface flow treatment unit; 31, soil layer; 32, surface water layer; 33, samphire. DETAILED DESCRIPTION

[0030] The following is a specific implementation of the present invention and combined with the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0031] like Figure 1-3 The figure shows a specific embodiment of the aquaculture tail water circulation purification device and purification method based on microbial cultivation of the present invention.

[0032] The aquaculture tailwater circulation purification device based on microbial fixed cultivation includes a first water flow branch s1 and a second water flow branch s2, the first water flow branch s1 and the second water flow branch s2 are isolated from each other and arranged in parallel, the first water flow branch s1 includes a sedimentation treatment unit 1 and an undercurrent treatment unit 2 arranged in sequence, the aquaculture tailwater of the aquaculture pond flows through the sedimentation treatment unit 1 and the undercurrent treatment unit 2 in sequence and returns to the aquaculture pond for circulation, the second water flow branch s2 includes a sedimentation treatment unit 1, a surface flow treatment unit 3 and an undercurrent treatment unit 2 arranged in sequence, the aquaculture tailwater of the aquaculture pond flows through the sedimentation treatment unit 1, the surface flow treatment unit 3 and the undercurrent treatment unit 2 in sequence and returns to the aquaculture pond for circulation. The aquaculture pond is generally for aquaculture of shrimp, and the following is implemented by taking aquaculture of shrimp as an example.

[0033] Since the first water flow branch s1 and the second water flow branch s2 differ only in whether the surface flow processing unit 3 is provided, only the second water flow branch s2 is described in detail.

[0034] The sedimentation treatment unit 1 in the second water flow branch s2 is composed of a water inlet collection tank 11 and an inclined plate sedimentation tank 12. The inlet water enters from the top of the leftmost water collection area and enters the bottom of the inclined plate sedimentation tank 12 along the "L" shape of the water inlet collection tank 11. At the same time, the water that has been completely precipitated in the upper layer of the inclined plate sedimentation tank 12 is pushed into the surface flow treatment unit 3 (if it is the first water flow branch s1, it is pushed into the submerged flow treatment unit 2) for further treatment.

[0035] The surface flow treatment unit 3 includes a soil layer 31 below and a surface flow water layer 32 above, and a salicornia 33 is planted in the surface flow water layer 32. Due to the water level difference, the tail water flowing through the surface flow treatment unit 3 enters the subsurface flow treatment unit 2. The subsurface flow treatment unit 2 is sequentially provided with a zeolite layer 21, a ceramsite layer 22, a gravel layer 23, and a subsurface flow water layer 24 from bottom to top, and the aquaculture tail water flows sequentially through the subsurface flow water layer 24, the gravel layer 23, the ceramsite layer 22, and the zeolite layer 21. An "L"-shaped aeration pipe 26 is laid in the zeolite layer 21, and the "L"-shaped aeration pipe 26 extends from the zeolite layer 21 to the subsurface flow water layer 24 through its own shape.

[0036] Zeolite is a natural, harmless, pollution-free, environmentally friendly phosphorus removal adsorption material that can effectively remove phosphorus from aquaculture wastewater within a wide pH range. In my country, it has abundant reserves, a wide range of sources, and is inexpensive. The zeolite filling volume ratio is 20%, and large-sized zeolite with a size of 10-20cm is used to pave the bottom of the pool. The functions of the zeolite layer are: [1] to adsorb phosphorus in the aquaculture wastewater, further reducing the phosphorus content of the water body; [2] to provide a larger gap at the bottom to prevent the bottom water outlet channel from being blocked by sediments, making it easier to clear silt.

[0037] Ceramic granules are made of clay, shale, coal gangue or fly ash as the main raw materials, mixed with a small amount of auxiliary raw materials and pore-forming agents, and processed through batching, crushing, balling, high-temperature firing, screening and other processes. They have high biological and chemical stability, rough surface, large specific surface area and high porosity. The specific surface area of ​​ordinary ceramsite is 300-1000rn2·m- 3 , bulk density is 200~1000kg·m- 3 , the porosity reaches more than 30%, so it is a good biofilm water treatment filler. The functions of the ceramsite layer are: [1] Zeolite can withstand water scouring and shear stress, making the water distribution uniform and the flow state stable, so that the soluble pollutants in the water body are fully in contact with the bacterial biofilm on the surface of the ceramsite, which is conducive to the full adsorption and decomposition of the pollutants, and at the same time, the dissolved oxygen in the water is evenly distributed in the filler layer to prevent the formation of hypoxic areas; [2] Zeolite has a lower density than water. When the system is running, it is suspended in the water. Under the action of water flow, the ceramsite is constantly moving, so that there will be no sediment in the ceramsite layer, and the ceramsite layer with smaller gaps is blocked; [3] Ceramsite has a large specific surface area, which is conducive to the enrichment of a large number of microorganisms, and finally forms a large area of ​​biofilm as the main functional area for aquaculture wastewater treatment.

[0038] The volume ratio of gravel filling is less than 10%. Gravel of 3-5 cm is used to lay on the expanded clay layer. The functions of the gravel layer are: [1] Since the density of expanded clay is lower than that of water, the buoyancy generated by the accumulation of a large amount of expanded clay will push part of the surface expanded clay out of the water, thereby losing its water treatment function. The laying of gravel presses down the expanded clay layer, making it stable below the water surface; [2] A large number of microorganisms accumulate on the expanded clay, forming a stable biofilm, which is not good for human perception. The laying of the gravel layer can be used as an ecological landscape; [3] The gravel layer can effectively prevent the influence of sun exposure on the biofilm of the expanded clay layer, and at the same time form a darkroom effect, preventing the growth of algae in the wetland, which is conducive to the stable operation of the water treatment system.

[0039] As a preferred method, the undercurrent water layer 24 is used to culture shad. Shad (Konosirus punctatus) is a species of the genus Shad of the family Herringidae in the order Herpetiformes. It has a wide range of salt adaptation and mainly feeds on phytoplankton, zooplankton and benthic organisms. It is found along the coast of China and is a pelagic fish in the coastal waters of my country. It usually lives in shallow waters of inner bays and likes to swim on the water surface. It is a marine fish to be cultured. 2 The stocking density is 5 cm or larger, with the following effects: [1] The tailwater from shrimp farming usually contains high concentrations of diatoms and green algae, which can be used as natural biological bait for the cultivation of spotted mullet. At the same time, the filter feeding effect of spotted mullet can reduce the concentration of algae and suspended organic particles, and further remove the total nitrogen and phosphorus content in the water; [2] As part of the ecological landscape, it can enhance the landscape value of the water treatment system.

[0040] Preferably, a floating bed 25 is provided in the undercurrent water layer 24, and salicornia europaea is planted in the floating bed 25. Salicornia europaea is an annual herbaceous plant of the Chenopodiaceae family, which grows on beaches and saline-alkali mudflats. Its growth period is about 220 days, of which tender stems can be kept for 50 to 60 days. In summer, the whole plant can be harvested as a green health food. In the undercurrent water layer 24 where the spotted bream is cultivated, salicornia europaea is planted in a floating bed 25 made of ceramsite as the main aggregate, which accounts for 40% of the area of ​​the pool. When the plant grows to more than 15 cm, the external tender stems are harvested. The functions are as follows: [1] Previous studies have shown that salicornia europaea is a fast-growing, harvestable plant suitable for growing in seawater. It can be used to absorb nutrients such as nitrogen and phosphorus in the water body and help purify the water quality. At the same time, the ceramsite floating bed itself also has a certain effect on improving water quality; [2] It forms an ecological landscape together with the gravel layer 23 and the spotted bream, and provides a shelter for the spotted bream.

[0041] Preferably, the ceramsite layer 22 is used to culture nereids. Nereids belong to the family Nereididae, class Polychaete, order Amphiprion, phylum Annelida, and inhabit muddy beaches and seabed sand. They can swim during the reproductive season or when they go out at night to forage. They are widely cultured along the coast of my country. 3 The density of double-toothed or multi-toothed sandworms with a size of more than 10 cm is used to place them. The functions are as follows: [1] The sandworms can swallow the sediment at the bottom of the digestion tank, reducing the accumulation of sediment at the bottom; [2] The sandworms can eat the aged and shed biofilm, maintain the continuous renewal of the expanded clay biofilm, and prevent system aging.

[0042] As a preference, the ceramsite layer 22 is provided with a biofilm flora, i.e., a microbial flora, to form a microbial ecosystem that has a prominent nitrification ability and a variety of pollutant degradation capabilities. More preferably, the biofilm flora includes a nitrifying flora and a bacillus flora. Nitrifying flora and bacillus flora are currently the most economical microbial community pollution degradation solutions. Nitrification is the oxidation process of ammonia nitrogen to nitrate nitrogen, and the bacterial groups that work in this process are called nitrifying flora. The nitrifying flora enables the subsurface treatment unit 2 to produce nitrification capabilities, which are mainly used to remove ammonia nitrogen and nitrite nitrogen in the water body. The bacillus flora can usually produce proteases, participate in material circulation, and decompose various macromolecular organic matter, among which some bacillus also participate in various processes of the nitrogen cycle. At the same time, combined with the nitrifying bacterial flora, the diversity of the bacterial community can be improved, the impact resistance can be enhanced, the system function can be stabilized, and a variety of pollutant treatment capabilities such as the ability to decompose macromolecular organic matter can be provided, which is mainly used to remove macromolecular organic matter in the water body, reduce the surface foam of the aquaculture water body, and reduce the pollutant indicators such as COD, BOD, and petroleum hydrocarbons. At the same time, nitrifying bacteria and Bacillus flora can effectively establish carbon-nitrogen cycle pathways in artificial wetlands, making the function of artificial wetland biofilms more stable, the degradation capacity more diverse, and better able to withstand the impact of changes in pollutant concentrations.

[0043] A method for circulating and purifying aquaculture tail water based on microbial cultivation, which uses the above purification device, comprises the following steps:

[0044] S1: construct the first water flow branch s1 and the second water flow branch s2;

[0045] S2: Directed cultivation of microbial flora;

[0046] S3: Immobilizing the microbial flora on the ceramsite layer 22.

[0047] After the construction is completed, the breeding pool and the first water flow branch s1 and the second water flow branch s2 are connected to form a closed loop. That is, the water outlet of the breeding pool is connected to the water inlet of the first water flow branch s1 and the second water flow branch, and the water outlet of the first water flow branch s1 and the second water flow branch is connected to the water inlet of the breeding pool. The breeding tail water is discharged into the system for bacterial cultivation and domestication. The system operation parameters are: water inlet time 1 hour, hydraulic retention time 1 hour, and aeration pipe aeration for 1 hour.

[0048] The spotted mullet is temporarily raised in seawater pools or glass tanks. The stocking density is that the aquaculture water body uses sand-filtered seawater, and then 5% of the artificial wetland effluent is increased every day for adaptive domestication. After 100% is used to replace the sand-filtered seawater, the breeding is continued for more than 3 days. If the fish has no obvious discomfort or disease, it can be placed in the above system.

[0049] The sandworms are temporarily reared in mud or sand layers on the beach, with a layer thickness of about 20 cm and a breeding density of 400 / rn2. The breeding water is sand-filtered seawater, and then the effluent from the artificial wetland is increased by 5% every day until 100% of the sand-filtered seawater is replaced. During the temporary rearing process, the bait is fed 2-3 times a day, and the bait added is shrimp feed + 5% of wetland pool sediment. Then the sediment is increased by 5% every day until 100% of the feed is replaced. After the replacement of the breeding water and bait is completed, the breeding is continued for more than 3 days, and then the live sandworms are manually harvested and placed in the above system.

[0050] The directional cultivation of the microbial flora in step S2 mainly includes the directional cultivation of the Bacillus flora and the directional cultivation of the nitrifying flora.

[0051] The targeted cultivation of nitrifying bacteria includes taking a mixed sample of fresh sediment and aquaculture water, inoculating it into a nitrifying bacteria enrichment medium for cultivation, testing the nitrite nitrogen content every day, and supplementing NaNO when the test result is colorless. 2 To 50 mg / L, after supplementing 4 times, the bacterial cells were collected by low-speed centrifugation and re-added to the enrichment culture medium for cultivation. The enrichment culture process was repeated until the bacterial concentration reached the standard, and it was added as seed liquid to the new enrichment culture medium for expansion culture to obtain the nitrifying bacteria expansion culture liquid.

[0052] The specific parameters are: take 1 ml of the mixed sample of fresh sediment and aquaculture water, inoculate it into a 250 ml Erlenmeyer flask containing 100 ml of nitrifying bacteria enrichment medium, shake it thoroughly, and culture it at 30°C and 150 r / min. Use Griess reagent to test the nitrite nitrogen content in the enrichment solution every day. If the test result is colorless, add NaNO 2 After four supplements, the bacterial cells were collected by low-speed centrifugation and re-added to the enrichment medium for culture. The enrichment culture process was repeated until the bacterial concentration reached 1×10 5 / ml, which is used as seed liquid, and added into new enrichment medium at a 5% inoculation amount for expansion culture, and the obtained nitrifying bacteria group expansion culture liquid is used for standby.

[0053] The formula of the nitrifying bacteria enrichment medium (50 times): 20g sodium nitrite, 500g calcium carbonate, 50g sodium chloride, 50g dipotassium hydrogen phosphate, 50g magnesium sulfate, 40g ferrous sulfate, dissolved in sterile seawater, fixed to 2000ml, adjusted pH to 7.5, sterilized at 121℃ for 20min. Dilute 50 times when using.

[0054] The immobilization of the nitrifying bacteria in step S3 is to place the ceramsite in the culture solution for expanding the nitrifying bacteria and perform aeration and biofilm formation. During the biofilm formation process, the content of nitrite nitrogen is detected every day. When the content drops to 0, the ceramsite is taken out and washed with sand-filtered seawater until the washing solution contains no nitrate nitrogen. The washed ceramsite is then transferred to the culture solution for expanding the nitrifying bacteria and biofilm formation is continued. After three consecutive transfers according to the above method, a ceramsite carrier for immobilizing the nitrifying bacteria is obtained.

[0055] The specific parameters are: 2-3cm ceramsite is selected as the biological carrier for bacterial fixation, and is placed in a nitrifying bacteria expansion culture medium with a nitrite nitrogen concentration of 20 mg / L, and aerated biofilm is formed at 30°C and pH 7.0-7.5. During the biofilm formation process, the content of nitrite nitrogen in the culture medium is qualitatively detected by Griess reagent every day. When the content drops to 0, the carrier is taken out and washed with sand-filtered seawater until the washing liquid does not contain nitrate nitrogen (diphenylamine qualitative detection is colorless). After that, the washed carrier is transferred to a fresh culture medium and the biofilm formation is continued. After three consecutive transfers according to the above method, a ceramsite carrier with nitrifying bacteria fixed is obtained.

[0056] The directional cultivation of Bacillus flora is to take out the sediment from the aquaculture pond, filter out the water, dry and grind it into powder, sterilize it at high temperature to obtain treated sediment, take a mixed sample of fresh sediment and aquaculture water, inoculate it in a container filled with sterilized sand-filtered seawater, shake it thoroughly in a water bath, transfer it to a container containing sterilized sand-filtered seawater with treated sediment for cultivation, use the culture solution as seed solution, transfer it into a sand-filtered seawater suspension containing treated sediment for expansion culture, and obtain Bacillus flora expansion culture solution.

[0057] The specific parameters are: drying in a 60℃ oven, grinding into powder, putting into a glass container and sterilizing at 121℃ for 30min, obtaining treated sediment, and placing in a cool and dry place for use. Take 1ml of the mixed sample of fresh sediment and aquaculture water, inoculate it in a 15ml centrifuge tube containing 10ml sterilized sand-filtered seawater, shake it well, bathe it in a water bath at 80℃ for 20min, and then transfer it to a 250ml triangular flask containing 100ml sand-filtered sterilized seawater containing 10% treated sediment, and culture it at 30℃ and 150r / min for 24 hours. The culture solution is used as the seed solution, and the sand-filtered seawater suspension containing 10% treated sediment is inoculated at a 10% inoculation amount for expansion culture, and the obtained Bacillus flora expansion culture solution is used for use.

[0058] In step S3, the immobilization of the Bacillus flora includes selecting ceramsite with a specification of 2-3 cm, placing it in the Bacillus flora expansion culture medium, aerating and forming biofilm, taking out the biofilm-forming ceramsite, adding new ceramsite, and adding treated sediment, and repeating the previous process until a sufficient amount of ceramsite carriers for immobilizing the Bacillus flora are obtained.

[0059] The specific parameters are: 2-3cm ceramsite is selected as the biological carrier for bacterial fixation, placed in the culture medium for the expansion of the Bacillus flora, and aerated biofilm is formed at 30°C and pH 7.0-7.5. After 24 hours of biofilm formation, it is taken out, new ceramsite is placed, and 5% of the treated sediment is added. Repeat the previous process until a sufficient amount of ceramsite carrier for the immobilization of the Bacillus flora is obtained.

[0060] The following is the specific test data when the aquaculture wastewater recycling purification device was applied to the intensive aquaculture of white shrimp. The specific time span is from May to June. The water samples were first filtered through a 0.45μm glass fiber filter membrane, and then the indicators such as soluble ammonium salt, nitrite, nitrate, and active phosphate in the water were determined according to the method recommended in the "Marine Monitoring Specifications":

[0061] Table 1 Ammonia nitrogen removal effect during aquaculture (unit: mg / 1)

[0062]

[0063] Table 2 Nitrite nitrogen removal effect during aquaculture (unit: mg / l)

[0064]

[0065] Table 3 Nitrate nitrogen removal effect during aquaculture (unit: mg / l)

[0066]

[0067]

[0068] Table 4 COD removal effect during aquaculture (unit: mg / l)

[0069]

[0070] Table 5 Chlorophyll a removal effect during aquaculture (unit: mg / l)

[0071]

[0072] Table 6 Removal effect of active phosphate during aquaculture (unit: mg / l)

[0073]

[0074] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for circulating and purifying aquaculture tail water based on microbial cultivation, using a purification device, characterized in that: The purification device comprises a first water flow branch and a second water flow branch, the first water flow branch and the second water flow branch are isolated from each other and arranged in parallel, the first water flow branch comprises a sedimentation treatment unit and an undercurrent treatment unit arranged in sequence, the aquaculture tail water of the aquaculture pond flows through the sedimentation treatment unit and the undercurrent treatment unit in sequence and returns to the aquaculture pond for circulation, the second water flow branch comprises a sedimentation treatment unit, a surface flow treatment unit and an undercurrent treatment unit arranged in sequence, the aquaculture tail water of the aquaculture pond flows through the sedimentation treatment unit, the surface flow treatment unit and the undercurrent treatment unit in sequence and returns to the aquaculture pond for circulation; The surface flow treatment unit includes a soil layer below and a surface flow water layer above. Salicornia is planted in the surface flow water layer. The subsurface flow treatment unit is provided with a zeolite layer, a ceramsite layer, a gravel layer and a subsurface flow water layer from bottom to top. The aquaculture tail water flows through the subsurface flow water layer, the gravel layer, the ceramsite layer and the zeolite layer in sequence. The purification method includes the following steps: S1: construct the first water flow branch and the second water flow branch; S2: Directed cultivation of microbial flora; S3: Immobilize the microbial flora on the expanded clay layer.

2. The method for circulating and purifying aquaculture tail water based on microbial culture according to claim 1, characterized in that: The subsurface water layer is used to culture spotted mullet at a rate of 20 per m 2 The stocking density is 5cm or above.

3. The method for circulating and purifying aquaculture tail water based on microbial culture according to claim 1, characterized in that: A floating bed is arranged in the subsurface water layer, and the salicornia is planted in the floating bed. The salicornia is planted on the floating bed made of ceramsite as the main aggregate according to 40% of the area of ​​the pool, and the external tender stems are harvested when the plants grow to more than 15 cm.

4. The method for circulating and purifying aquaculture tail water based on microbial culture according to claim 1, characterized in that: The ceramsite layer is used to culture sandworms at a rate of 20 to 30 pieces / m 3 The density of double-toothed or multi-toothed sandworms with a size of more than 10 cm is released.

5. The method for circulating and purifying aquaculture tail water based on microbial culture according to any one of claims 1 to 4, characterized in that: In step S2, the directional cultivation of the microbial flora includes taking out the aquaculture sediment, filtering out the water, drying and grinding into powder, and high-temperature sterilization to obtain treated sediment, taking a mixed sample of fresh sediment and aquaculture water, inoculating it in a container filled with sterilized sand-filtered seawater, and after fully shaking in a water bath, transferring it to a container containing sterilized sand-filtered seawater with treated sediment for cultivation, using the culture solution as a seed solution, and transferring it to a sand-filtered seawater suspension containing treated sediment for expansion culture to obtain a Bacillus flora expansion culture solution.

6. The method for circulating and purifying aquaculture tail water based on microbial culture according to claim 5, characterized in that: In step S2, the directional cultivation of the microbial flora also includes taking a mixed sample of fresh sediment and aquaculture water, inoculating it into a nitrifying bacteria enrichment medium for cultivation, testing the nitrite nitrogen content every day, supplementing NaNO2 to 50 mg / L when the test result is colorless, and after four supplements, collecting the bacterial cells by low-speed centrifugation filtration, re-adding the enrichment medium for cultivation, repeating the enrichment culture process until the bacterial concentration reaches the standard, and adding it as a seed liquid to a new enrichment medium for expansion culture to obtain a nitrifying bacteria expansion culture liquid.

7. The method for circulating and purifying aquaculture tail water based on microbial culture according to claim 5, characterized in that: In step S3, the immobilization of the microbial flora includes selecting 2-3 cm ceramsite, placing it in a culture medium for expanding the Bacillus flora, aerating and forming biofilms, taking out the biofilm-forming ceramsite, placing new ceramsite, and adding treated sediments, and repeating the previous process until a sufficient amount of ceramsite carriers for immobilizing the Bacillus flora are obtained.

8. The method for circulating and purifying aquaculture tail water based on microbial culture according to claim 6, characterized in that: In step S3, the immobilization of the microbial flora includes selecting ceramsite with a specification of 2-3 cm, placing it in a culture medium for expanding the nitrifying bacteria, and aerating and forming biofilms. During the biofilm forming process, the content of nitrite nitrogen is detected every day. When the content drops to 0, the ceramsite is taken out and washed with sand-filtered seawater until the washing liquid contains no nitrate nitrogen. Thereafter, the washed ceramsite is transferred to a culture medium for expanding the nitrifying bacteria, and biofilm formation is continued. After three consecutive transfers according to the above method, a ceramsite carrier for immobilizing the nitrifying bacteria is obtained.

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