Water circulation system and treatment method for culturing marine fishes by using brackish water in saline-alkali soil

Abstract

The invention discloses a circulation system for culturing marine fishes by using brackish water in saline-alkali soil, which comprises a primary purification unit for receiving brackish water and / or spirulina secondary wastewater, the primary purification unit is communicated with a biological tank, the biological tank is communicated with a secondary purification unit, the secondary purification unit is communicated with an aeration tank, and the aeration tank is communicated with an aeration tank. The aeration tank is communicated with the culture pond; the invention also provides a water treatment method for culturing marine fishes by using brackish water in saline-alkali soil. The brackish water treatment system can treat brackish water and is used for culturing marine fishes, in the whole water circulation stage, the water circulation utilization rate is high, water source waste and other redundant substances generated in the system cannot be caused, the water body components of the water circulation system are discharged out of the system after filter pressing, and the brackish water treatment system is large in treatment capacity, free of pollution and small in energy consumption in the aspect of water treatment. And the method is suitable for large-area popularization so as to solve the problem that brackish water cannot be effectively utilized.

Description

Technical Field

[0001] The present application relates to the technical field of brackish water transformation, and in particular to a water circulation system and a treatment method for cultivating marine fish using brackish water in saline-alkali land. Background Art

[0002] At present, the research on the development of brackish water fisheries at home and abroad mainly focuses on several aspects: domestication of alkaline water fish, shellfish, shrimp, variety selection, ecological improvement of brackish water water quality, brackish water aquaculture technology and model, tourism development, etc. Among them, the research on basic theory and healthy aquaculture technology has achieved certain results, clarified the key factors restricting brackish water fishery aquaculture, clarified the water quality characteristics of brackish waters, and the limiting factors that restrict the survival of aquatic organisms in brackish waters.

[0003] At present, the amount of brackish water resources that can be used for breeding marine fish in Northwest my country is very abundant, and the development and utilization rate of existing saline-alkali return water is still not high. Therefore, the marine fish breeding resources of brackish water have obvious advantages. In terms of breeding, through the development and utilization of brackish water, the economic and ecological benefits of marine fish breeding can be doubled. At present, the main problem in the application of brackish water is that there are differences in specific components from seawater, and the pH value and nitrite content of brackish water are relatively high. Secondly, during the breeding process, it is necessary to stably maintain the normal environment of the breeding water body. For this reason, we proposed a water circulation system and treatment method for breeding marine fish using brackish water in saline-alkali land to solve the above problems. Summary of the invention

[0004] The present application provides a water circulation system and a treatment method for cultivating marine fish using brackish water in saline-alkali land, which solves the problem that a large amount of brackish water cannot be effectively utilized.

[0005] The present application provides a circulation system for breeding marine fish using brackish water in saline-alkali land, comprising a primary purification unit for receiving brackish water and / or secondary wastewater of spirulina, wherein the primary purification unit is connected to a biological pool, the biological pool is connected to a secondary purification unit, the secondary purification unit is connected to an aeration pool, and the aeration pool is connected to a breeding pool;

[0006] The primary purification unit comprises a water diversion unit for receiving bitter idle water and / or spirulina secondary wastewater, the water diversion unit is connected to a mixing tank via a pipeline, a dosing tank is installed on the pipeline, a sedimentation tank is provided on one side of the mixing tank, and an overflow port of the sedimentation tank is connected to the biological pool;

[0007] The secondary purification unit comprises a plurality of biofilters arranged in series, a screen is detachably mounted on the top of the biofilter, an overflow trough is arranged on one side of the biofilter, a guide pipe of an adjacent biofilter is connected to the bottom of the overflow trough, and a pressure pump is installed on the guide pipe;

[0008] One side of the water diversion unit and the bottom of the biological filter are both equipped with sewage pipes.

[0009] Preferably, the water diversion unit includes a water diversion trough body, in which a filter screen bucket is arranged, the filter screen bucket divides the water diversion trough body into a filter chamber and a water collecting chamber, a sewage outlet is arranged on one side of the filter chamber, the sewage outlet is connected to the sewage outlet, and a drainage outlet is arranged at the bottom of the water collecting chamber.

[0010] Preferably, a buffer bin is provided on one side of the sedimentation tank, and the drain outlet of the mixing tank corresponds to the buffer bin.

[0011] Preferably, a vibrator is installed on the screen.

[0012] Preferably, a filter press is installed at the sewage discharge end of the sewage pipe, and the water outlet end of the filter press is connected to the water diversion unit.

[0013] Preferably, a temperature control device is also provided between the aeration tank and the breeding pond.

[0014] A water treatment method for cultivating marine fish using brackish water in saline-alkali land comprises the following steps:

[0015] S1, send the brackish water and / or secondary wastewater from spirulina treatment to the water diversion unit for simple filtration, and test the introduced water, compare it with the seawater element configuration table, and mark the excess elements, pH value and harmful impurities;

[0016] S2, preparing drugs for reducing excess elements, pH value and harmful impurities, adding them into the water body through a drug adding tank, and sending them to a sedimentation tank after mixing;

[0017] S3, the water overflowing from the sedimentation tank is sent to the biological pool to be treated by adding nitrifying bacteria;

[0018] S4, the water treated with nitrifying bacteria is sent to the biofilter, where it is filtered in multiple stages and sent to the blending tank;

[0019] S5, testing the water in the blending tank to obtain water composition and pH value, and supplementing the water composition to the range value in the seawater composition table by comparing with the seawater composition table;

[0020] S6, sending the water body after the supplementation to an aeration tank for aeration, reducing the pH value of the water body, increasing the oxygen content of the water body, and then sending it to the breeding pond;

[0021] S7, regularly testing the composition and pH value in the culture pond, and when the composition and pH value deviate from the preset value, draining 25%-35% of the water in the culture pond and replenishing the water treated in S6;

[0022] S8, the water discharged from the aquaculture pond, the supernatant liquid is sent to the aeration tank and the biological filter, and the water containing impurities is sent to the water diversion unit.

[0023] Preferably, in stage S6, carbon dioxide gas is first introduced into the aeration tank, and when the pH value of the water body drops to a set value, oxygen is introduced until the oxygen content of the water body is greater than 80%.

[0024] Preferably, the impure water discharged from the sedimentation tank, water diversion unit, biological pool and biological filter is sent to the filter press workshop for treatment, wherein the filter press wastewater is sent to the water diversion unit and the filter press cake is left to stand and dry.

[0025] Preferably, the aeration time is no more than three hours.

[0026] It can be seen from the above technical scheme that the present application provides a circulation system and method for cultivating marine fish using brackish water in saline-alkali land. The present application combines multi-stage purification with biological methods, removes excess ions and harmful substances in the water through flocculation, and then further reduces the nitrite content in the water through digestive bacteria, and then removes other impurities such as digestive bacteria, adjusts according to the required components, and then reduces the pH value of the water and increases the oxygen content of the water through aeration, and adjusts the components of the brackish water to be close to the components of seawater, and cultivates artificially domesticated salmon, trout, shrimp, oysters and other seafood. The water generated during the cultivation process is sent to this system to complete the recycling. The present application solves the problem of the utilization of brackish water through a lower processing cost, and can turn brackish water into treasure with less investment.

[0027] Compared with the prior art, the beneficial effects of this application are:

[0028] 1. Through the setting of the primary purification unit, impurities in brackish water are removed in stages, so that the content of each element is less than the required amount, which is convenient for the subsequent aquaculture seawater configuration, and the efficiency of segmented impurity removal is higher. According to the time, the water storage capacity of each link is set to achieve continuous circulation treatment;

[0029] 2. Through the setting of biological pool, the nitrite content can be further reduced through nitrifying bacteria to the content required for breeding;

[0030] 3. Through the setting of secondary purification, microorganisms in water can be removed in multiple links and steps, the purification efficiency can be improved, the nutrients in water can be reduced, and thus the growth of microorganisms in aquaculture can be reduced;

[0031] 4. Through the aeration setting, carbon dioxide can be used to lower the pH value of the water, and the oxygen content of the water can be increased to reach the actual oxygen content of seawater, thereby increasing the survival rate of marine fish in the water.

[0032] In summary, the present application can treat brackish water for breeding marine fish, and in the entire water circulation stage, the water circulation utilization rate is high, and no water waste is caused. Other excess substances generated in the system are discharged from the system after pressure filtration, thereby stabilizing the water composition of the water circulation system. In addition, the present application has a large processing capacity, is pollution-free, has low energy consumption, and has a low processing cost in water treatment. It is suitable for large-scale promotion to solve the problem that brackish water cannot be effectively utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the implementation cases. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] Figure 1 This is a schematic diagram of the structure of a circulation system for breeding marine fish using brackish water in saline-alkali land proposed in this application;

[0035] Figure 2 This is a schematic diagram of the structure of the primary purification unit of a circulation system for breeding marine fish using brackish water in saline-alkali land proposed in this application;

[0036] Figure 3 This is a schematic diagram of the installation structure of a sedimentation tank and a biological tank in a circulation system for breeding marine fish using brackish water in saline-alkali land proposed in this application;

[0037] Figure 4 This is a schematic diagram of the structure of a secondary purification unit of a circulation system for aquaculture of marine fish using brackish water in saline-alkali land proposed in this application;

[0038] Figure 5 This is a schematic diagram of the structure of a water diversion unit of a circulation system for breeding marine fish in saline-alkali land using brackish water, as proposed in this application.

[0039] In the figure: 1 sedimentation tank, 2 sewage pipe, 3 mixing tank, 4 buffer bin, 5 water diversion unit, 51 sewage outlet, 52 water outlet, 53 filter screen bucket, 54 water diversion tank body, 6 dosing tank, 7 biological tank, 8 vibrator, 9 screen, 10 overflow tank, 11 diversion pipe, 12 biological filter, 13 booster pump. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0041] See also Figure 1-5A circulation system for cultivating marine fish using brackish water in saline-alkali land, including a primary purification unit for receiving brackish water and / or spirulina secondary wastewater. In addition to brackish water, the present application can also utilize wastewater generated during the production of spirulina. There are a large number of sodium, potassium, and calcium ions in the spirulina wastewater, so it cannot be discharged directly. In the past, in the production of spirulina, the wastewater was mainly the water from the centrifugation or filter pressing process of spirulina slurry, i.e., the secondary wastewater. The wastewater cannot be used as culture water and can only be treated by high-pressure reverse osmosis technology. In the present application, the spirulina secondary wastewater can be used as brackish water. The primary purification unit mainly performs initial filtration on the water entering the system and collects trace element information of the water source to facilitate the preparation of medicines and the treatment of excess or harmful ions. Nitrite has a greater impact on the survival rate of marine fish during the breeding process, and it is not easy to increase too much chemical agents, so it is necessary to A small amount of nitrite is biologically treated, and the pH value of the water body can be lowered by the initial filtration. The first-level purification unit is connected to the biological pool 7, and there are multiple biological pools 7. The biological pool 7 can be designed as an open-air pool or a greenhouse. Although the biological pool 7 occupies a large area, the saline-alkali land is mostly wasteland, so the land around the brackish water can be effectively utilized. The water after the initial filtration is sent to multiple biological pools 7 according to the time stage, and nitrifying bacteria are added to further reduce the amount of nitrite. In the stage of treating nitrite, other impurities or algae will be produced, and the nitrifying bacteria in the water also exceed the standard. For this reason, the biological pool 7 is connected to the secondary purification unit to remove impurities such as algae, and at the same time, the nitrifying bacteria are further removed to reduce their content. After the secondary purification of the water, the content of each element in the water body is measured again. According to the different requirements of aquaculture seawater, Ca is artificially added 2+ Mg 2+ , K + 、Na + Elements such as chlorinated carbon dioxide and chlorinated chlorinated carbon dioxide are used to adjust the concentration and proportion of major ions in brackish water. The secondary purification unit is connected to an aeration tank. Different aeration tanks are configured for different seafood breeding ponds. The required water quality conditions are fine-tuned in the aeration tank. The aeration tank is connected to the breeding pond, and the fine-tuned water is sent to the breeding pond. When the water quality in the breeding pond decreases, it can be sent to this system for treatment, so that the water in the entire breeding process can be recycled.

[0042] The primary purification unit includes a water diversion unit 5 for receiving bitter and salty water and / or spirulina secondary wastewater. External bitter and salty water can be introduced into the water diversion unit 5 by means of a water pump or a water channel, and is simply filtered by the water diversion unit 5. The water diversion unit 5 is connected to a mixing tank 3 through a pipeline, and the filtered water flows into the mixing tank 3. A stirring motor is installed in the mixing tank 3 to improve the stirring efficiency of the water and the drug. A dosing tank 6 is installed on the pipeline. While the water flows into the mixing tank 3, drugs are added. The drugs need to be configured according to the actual bitter and salty water. In this application, nitrite, excess manganese, hydrogen sulfide and ammonia nitrogen compounds are mainly removed. A sedimentation tank 1 is connected and arranged on one side of the mixing tank 3. The water after adding the drugs is sent to The sedimentation tank 1 further reacts, and part of the flocculants and solids are precipitated. The construction of the sedimentation tank 1 can refer to the existing sedimentation tank settings. In the specific process of water entering, a buffer bin 4 is set on one side of the sedimentation tank 1. The buffer bin 4 is on the tangent of the sedimentation tank 1 and is connected to the sedimentation tank 1 through a bottom connection. The drainage port of the mixing tank 3 is connected to the buffer bin 4. The water in the mixing tank 3 enters the sedimentation tank 1 through the buffer bin 4. The overflow port of the sedimentation tank 1 is connected to the biological pool 7. The water precipitated in the sedimentation tank 1 is sent to different biological pools 7 in batches according to time. Nitrifying bacteria are added to remove nitrite and ammonia nitrogen compounds. In order to reduce the impact of brackish water on the soil, a black film can be laid on the bottom of the pool to reduce water penetration;

[0043] The secondary purification unit includes a plurality of biological filters 12 arranged in series. Since there are fewer solid impurities in the water body after the primary treatment, the water body after the treatment in the sedimentation tank 1 contains more bacteria and algae, so the secondary treatment is biological filtration. Specifically, the water body in the sedimentation tank 1 enters the biological filter 12 in a tangential direction. A screen 9 is detachably installed on the top of the biological filter 12. The screen 9 is a particle filter membrane that can filter particles in the water. The screen 9 holes of the plurality of biological filters 12 are arranged to be roughly small, which can improve the filtration efficiency. An overflow trough 10 is arranged on one side of the biological filter 12. The overflow trough 10 is located above the sieve 9. The guide pipes 11 of the adjacent biological filters 12 are connected to the bottom of the overflow trough 10 and are connected in series in sequence. A pressure pump 13 is installed on the guide pipe 11 to increase the water pressure entering the next biological filter 12.

[0044] During the specific filtration, the water enters the position below the screen 9 in the biological filter 12. The water in the biological filter 12 rotates under the action of water pressure, and some substances rotate to the center of the biological filter 12 and are discharged through the sewage pipe 2. The upper water is filtered through the screen 9 and enters the overflow tank 10 to be discharged to the next link. Under the flushing of the rotating water body, the permeability of the screen 9 can be guaranteed, thereby improving the filtration efficiency. After running for a period of time, the screen 9 will still be blocked, which can be cleaned with a sodium hydroxide aqueous solution;

[0045] A sewage pipe 2 is installed on one side of the water diversion unit 5 and the bottom of the biological filter 12 for discharging impurities generated during the filtration process. The discharged impurities can be further precipitated or directly discharged to the filter press for treatment. The water outlet of the filter press is connected to the water diversion unit. The wastewater generated during the filtration process can be sent to this system for reuse, and the solid matter generated can be dried and handed over to a qualified manufacturer for treatment.

[0046] In the present application, the water diversion unit 5 includes a water diversion trough body 54, which is a rectangular trough body. A filter screen 53 is arranged in the water diversion trough body 54. The filter screen 53 can be arranged in a trapezoidal shape and fixed on a side wall of the water diversion trough body 54. The filter screen 53 divides the water diversion trough body 54 into a filter chamber and a water collecting chamber, wherein the water body directly enters the filter chamber, is filtered by the filter screen 53, and then enters the water collecting chamber. A sewage outlet 51 is arranged on one side of the filter chamber. During the filtering process, the sewage outlet 51 is opened at a fixed time, and the sewage outlet 2 is connected to the sewage outlet 51. Impurities accumulated in the filter chamber can be carried out of the filter chamber through the water body and discharged through the sewage outlet 2. A drain outlet 52 is arranged at the bottom of the water collecting chamber, and the filtered water is discharged to the next link through the drain outlet 52. The water entering the system can be simply filtered continuously, and only regular cleaning is required.

[0047] In the present application, a vibrator 8 is installed on the screen 9. The vibrator 8 generates vibrations on the screen 9. Combined with water flushing, the blockage of the screen 9 can be reduced, the water passing rate can be further increased, and the filtering effect can be improved.

[0048] In the present application, a temperature control device is also provided between the aeration tank and the breeding tank. In view of the water temperature requirements of some seafood, such as salmon and trout, the water temperature can be adjusted before entering the breeding tank.

[0049] A water treatment method for cultivating marine fish using brackish water in saline-alkali land comprises the following steps:

[0050] S1, send the brackish water and / or secondary wastewater from spirulina treatment to the water diversion unit 5 for simple filtration, and detect the introduced water. The present application can treat brackish water, algae culture water, algae treatment water, and their mixed water. Since there are certain differences in the composition of water and culture brine, the excess elements, pH value and harmful impurities are marked by referring to the seawater element configuration table. The excess elements need to be adjusted to below the values ​​marked in the configuration table to facilitate the later configuration of water components. The pH value involves the specific adjustment of the dosage to reach the set value. If there are harmful bacteria in the water, bactericides need to be added for further treatment. In terms of impurities, if heavy metals exceed the standard, the heavy metals need to be flocculated. Other impurities can be seen in Table 1.

[0051] Table 1

[0052] parameter equation unit Normal value oxygen <![CDATA[O2]]> ％ 80-100 Nitrogen <![CDATA[N2]]> % Saturation 80-100 carbon dioxide <![CDATA[CO2]]> mg / L 10-15 Ammonia nitrogen <![CDATA[NH4+]]> mg / L 0-2.5 Ammonia nitrogen <![CDATA[NH3]]> mg / L ＜0.01 Nitrite <![CDATA[NO 2- ]]> mg / L 0-0.5 Nitrates <![CDATA[NO 3- ]]> mg / L 100-200 pH 6.5-8.2 phosphorus <![CDATA[PO4 3- ]]> mg / L 1-20 Suspended solids SS mg / L 10-25 oxygen demand COD mg / L 25-100 Turbidity NTU 1-3 Hydrogen sulfide <![CDATA[H2S]]> microgram ＜5

[0053] S2, prepare drugs for reducing excess elements, pH value and harmful impurities, add them into the water body through the drug adding tank 6, and send them to the sedimentation tank 1 after mixing. The drugs for improving water quality are sent into the flowing water body through the drug adding tank 6 to accelerate mixing, and then sent to the bottom of the sedimentation tank 1 for reaction and precipitation, and the clear liquid at the top of the sedimentation tank 1 flows out through overflow;

[0054] S3, the water overflowing from the sedimentation tank 1 is sent to the biological tank 7 for treatment with nitrifying bacteria. The treatment time of nitrifying bacteria is determined according to the test results. Please note that the sensor needs to be wiped clean before testing;

[0055] S4, after the test is qualified, the pH value cannot be greater than 0.5 of the upper limit of the alkalinity of the aquaculture water. If the pH value is large, it can be prepared by chemical agents. The water treated by nitrifying bacteria is sent to the biological filter 12. The water enters from the bottom of the biological filter 12 and overflows from the top. The bottom-up filtration method is adopted, which can effectively improve the filtration efficiency. Multiple biological filters 12 are connected in series, and multi-stage filtration can be performed. The filtered water is sent to the preparation tank;

[0056] S5, test the water in the mixing tank to obtain the water composition and pH value, mainly test the difference of the components required for aquaculture, and add the water composition to the range of the seawater composition table according to the seawater composition table, that is, to achieve the composition required for aquaculture. For different aquaculture species and domesticated species, configure according to actual needs;

[0057] S6, the water after supplementation is sent to the aeration tank for aeration. If the pH value of the water is greater than the maximum value required for aquaculture, carbon dioxide gas is first introduced into the aeration tank. When the pH value of the water drops to the set value, oxygen is introduced until the oxygen content of the water is greater than 80%. Ventilation increases the water-air exchange area, the amount of CO2 dissolved in the air in the water increases, and the carbonate balance system Moving to the right will increase the H+ concentration in the water and decrease the pH value. It can decrease by 0.5, thereby reducing the pH value of the water. After the pH reaches the set value, oxygen is introduced to increase the oxygen content in the water and then sent to the breeding pond. It is worth noting that too long aeration will lead to increased turbidity and total ammonia nitrogen, so the aeration time should not be too long. Therefore, the aeration time should not exceed three hours. Specifically, the carbon dioxide aeration time can be controlled within half an hour, and the oxygen aeration time can be controlled within 2.5 hours.

[0058] When individual indicators cannot be reduced to the set value during the aeration stage, the content of the indicator can be further reduced in the S2 and S3 stages. For example, hydrogen sulfide gas can be further removed by drugs or aeration in this application. If transitional aeration is required during the aeration stage, the indicator can be left at the set value and can be further reduced in the S2 and S3 stages.

[0059] S7, regularly testing the composition and pH value in the breeding pond. When the composition and pH value deviate from the preset value, 25%-35% of the water in the breeding pond is discharged and supplemented with the water treated in S6;

[0060] S8, the water discharged from the breeding pond, the supernatant is sent to the aeration tank and the biological filter 12, and the impurity-containing water is sent to the water diversion unit 5. Specifically, 20% of the supernatant is sent to the aeration tank, and hydrogen sulfide and alkalinity can be reduced by aeration. At the same time, the water body and the breeding water are closer in composition, which reduces the stress response of seafood during water change. 20-30% of the supernatant is sent to the biological filter 12 for filtration, and the biomass of the water body is reduced by filtration. 50-60% of the tail water is directly sent to the initial stage of S1 for treatment, thereby realizing the recycling of the breeding water, and the water from the multi-layer breeding pond is added to the new water replaced in the breeding pond, so that the new water and the breeding water are closer, further improving the adaptability of seafood.

[0061] In the present application, the impure water discharged from the sedimentation tank 1, the water diversion unit 5, the biological tank 7, and the biological filter 12 is sent to the filter press workshop for treatment, wherein the filter press wastewater is sent to the water diversion unit 5, and the filter cake is left to stand and dry. Specifically, when too much wastewater is discharged, it can be left to stand for treatment, and the upper clear liquid is sent to the sedimentation tank, and the precipitate is treated by filter press. The water discharged from the filter press is sent to the water diversion unit 5. In the present application, zero wastewater discharge can be achieved, and only impurities in the system are discharged. After the impurities are dried, they can be handed over to a third party for treatment. Therefore, the present application will not have an impact on the environment and will not affect the normal ecological environment.

[0062] It can be seen from the above technical solutions that the present application combines multi-stage purification with biological methods, removes excess ions and harmful substances in the water through flocculation, and then further reduces the nitrite content in the water through digestive bacteria, and then removes other impurities such as digestive bacteria, adjusts according to the required components, and then reduces the pH value of the water and increases the oxygen content of the water through aeration, adjusts the components of the brackish water to be close to the components of seawater, and cultivates artificially domesticated salmon, trout, shrimp, oysters and other seafood. The water generated during the cultivation process is sent to this system to complete the recycling. The present application solves the problem of the utilization of brackish water through a lower processing cost, and can turn brackish water into treasure with less investment.

[0063] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the application disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope of the present application is indicated by the claims.

[0064] It should be understood that the present application is not limited to the precise structure described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The above-described embodiments of the present application do not constitute a limitation on the scope of protection of the present application.

Claims

1. A circulation system for breeding marine fish using brackish water in saline-alkali land, characterized in that: It comprises a primary purification unit for receiving bitter idle water and / or spirulina secondary wastewater, the primary purification unit is connected to a biological pool (7), the biological pool (7) is connected to a secondary purification unit, the secondary purification unit is connected to an aeration pool, and the aeration pool is connected to a culture pool; The primary purification unit comprises a water diversion unit (5) for receiving bitter idle water and / or spirulina secondary wastewater, the water diversion unit (5) being connected to a mixing tank (3) via a pipeline, a dosing tank (6) being installed on the pipeline, a sedimentation tank (1) being arranged in communication with one side of the mixing tank (3), and an overflow port of the sedimentation tank (1) being in communication with the biological pool (7); The secondary purification unit comprises a plurality of biofilters (12) arranged in series, a screen (9) being detachably mounted on the top of the biofilter (12), an overflow trough (10) being arranged on one side of the biofilter (12), a guide pipe (11) of an adjacent biofilter (12) being connected to the bottom of the overflow trough (10), and a pressure pump (13) being mounted on the guide pipe (11); A sewage pipe (2) is installed on one side of the water diversion unit (5) and on the bottom of the biological filter (12).

2. The circulation system for breeding marine fish in saline-alkali land using brackish water according to claim 1, characterized in that: The water diversion unit (5) comprises a water diversion trough body (54), a filter screen bucket (53) is arranged in the water diversion trough body (54), the filter screen bucket (53) divides the water diversion trough body (54) into a filter chamber and a water collection chamber, a sewage outlet (51) is arranged on one side of the filter chamber, the sewage pipe (2) is connected to the sewage outlet (51), and a drainage outlet (52) is arranged at the bottom of the water collection chamber.

3. The circulation system for breeding marine fish in saline-alkali land using brackish water according to claim 1, characterized in that: A buffer bin (4) is provided on one side of the sedimentation tank (1), and the drainage outlet of the mixing tank (3) corresponds to the buffer bin (4).

4. The circulation system for breeding marine fish in saline-alkali land using brackish water according to claim 1, characterized in that: A vibrator (8) is installed on the screen (9).

5. The circulation system for breeding marine fish in saline-alkali land using brackish water according to claim 1, characterized in that: A filter press is installed at the sewage discharge end of the sewage discharge pipe (2), and the water outlet end of the filter press is connected to the water diversion unit.

6. The circulation system for breeding marine fish in saline-alkali land using brackish water according to claim 1, characterized in that: A temperature control device is also arranged between the aeration tank and the breeding pond.

7. A water treatment method for breeding marine fish using brackish water in saline-alkali land, characterized in that: The following steps are involved: S1, sending the brackish water and / or the secondary wastewater from the treatment of spirulina to the water diversion unit (5) for simple filtration, and testing the introduced water, comparing it with the seawater element configuration table, marking the excess elements, pH value and harmful impurities; S2, preparing drugs for reducing excess elements, pH value and harmful impurities, adding them into the water body through a drug adding tank (6), and sending them to the sedimentation tank (1) after mixing; S3, the overflow water from the sedimentation tank (1) is sent to the biological tank (7) to be treated with nitrifying bacteria; S4, the water treated with nitrifying bacteria is sent to the biofilter (12), filtered in multiple stages and sent to the blending tank; S5, testing the water in the blending tank to obtain water composition and pH value, and supplementing the water composition to the range value in the seawater composition table by comparing with the seawater composition table; S6, sending the water body after the supplementation to an aeration tank for aeration, reducing the pH value of the water body, increasing the oxygen content of the water body, and then sending it to the breeding pond; S7, regularly testing the composition and pH value in the culture pond, and when the composition and pH value deviate from the preset value, draining 25%-35% of the water in the culture pond and replenishing the water treated in S6; S8, the water discharged from the aquaculture pond, the supernatant liquid is sent to the aeration tank and the biological filter (12), and the water containing impurities is sent to the water diversion unit (5).

8. The water treatment method for breeding marine fish in saline-alkali land using brackish water according to claim 7, characterized in that: In the S6 stage, carbon dioxide gas is first introduced into the aeration tank, and when the pH value of the water body drops to a set value, oxygen is introduced until the oxygen content of the water body is greater than 80%.

9. The water treatment method for breeding marine fish in saline-alkali land using brackish water according to claim 7, characterized in that: The impure water discharged from the sedimentation tank (1), the water diversion unit (5), the biological tank (7) and the biological filter (12) is sent to the filter press workshop for treatment, wherein the filter press wastewater is sent to the water diversion unit (5) and the filter press cake is left to stand for drying treatment.

10. The water treatment method for breeding marine fish in saline-alkali land using brackish water according to claim 7, characterized in that: The aeration time is no more than three hours.

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