Saline-alkali soil aquaculture tail water circulation treatment system and method

Abstract

The invention discloses a saline-alkali soil aquaculture tail water circulation treatment system and method, relates to the technical field of saline-alkali soil aquaculture tail water treatment, and aims to solve the problems that the existing microbiological treatment technology is poor in effect of adapting to saline-alkali soil shrimp culture tail water, the connection between the system and culture circulation is insufficient, and nutrients are not recycled. According to the method, a closed-loop circulating system comprising a pretreatment unit, a microbiological treatment unit, a water quality conditioning and buffering unit and a nutrient recycling unit is constructed, pollutants are degraded through cooperation of a composite salt-tolerant flora and a saline-alkaline water modified filler, reuse water parameters are accurately controlled through water quality conditioning, and then nitrogen and phosphorus in tail water are converted into microalgae bait to be reused in a shrimp culture pond. According to the method, the tail water pollutant removal effect is improved, the problem of parameter fluctuation of reuse water is solved, tail water nutrient recycling and high-utilization-rate circulation are achieved, and the economic benefits and sustainability of saline-alkali land shrimp culture are enhanced.

Description

Technical Field

[0001] This invention relates to the field of microbial wastewater treatment technology, specifically to a system and method for recycling wastewater from aquaculture in saline-alkali land. Background Technology

[0002] Saline-alkali land aquaculture (especially shrimp farming) is an important direction for the development and utilization of saline-alkali land resources. It can revitalize idle saline-alkali land resources and enrich the industrial layout of aquaculture. However, this model has always faced the dual constraints of water shortage and wastewater pollution. The uneaten feed, feces, and nitrogen and phosphorus organic matter contained in the wastewater not only waste precious freshwater resources if directly discharged, but also exacerbate eutrophication of surrounding water bodies and disrupt the regional ecological balance. Therefore, wastewater recycling has become a core requirement for the sustainable development of the saline-alkali land shrimp farming industry. Currently, microbial wastewater treatment technology has become the mainstream technology for aquaculture wastewater treatment due to its low cost, lack of secondary pollution, and good degradation effect. It naturally degrades pollutants through the metabolic action of microorganisms, aligning with the development concept of green aquaculture. However, saline-alkali land shrimp farming wastewater has unique characteristics of high salinity and high alkalinity. Existing microbial treatment technologies are mostly developed based on freshwater aquaculture scenarios, and have significant shortcomings in the screening of salt-tolerant microorganisms and the design of synergistic effects of microbial communities, resulting in pollutant removal effects that are difficult to meet the treatment requirements of saline-alkali land shrimp farming wastewater.

[0003] When existing microbial treatment technologies are applied to the treatment of shrimp tailwater in saline-alkali land, several shortcomings are exposed that make them difficult to adapt to actual production: First, the connection between the microbial treatment unit and the aquaculture cycle is seriously insufficient. The salinity and pH of the treated tailwater lack precise control, and large fluctuations in parameters can easily cause stress to shrimp, significantly reducing the survival rate. Moreover, the system design does not fully consider the characteristics of water scarcity in saline-alkali land and does not optimize the recycling chain, resulting in low water resource utilization. Second, the nutrients in the tailwater are not utilized as resources. Existing technologies only focus on the degradation and removal of pollutants, converting nutrients such as nitrogen and phosphorus in the tailwater into sludge sediment. This not only wastes nutrient resources but also increases the cost of subsequent sludge treatment. At the same time, the application mode of a single microbial community also leads to insufficient nitrogen and phosphorus degradation efficiency in high-salt environments, which cannot meet the actual production needs of shrimp farming in saline-alkali land. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a system and method for recycling and treating wastewater from aquaculture in saline-alkali land, which solves the problems of insufficient integration between existing microbial treatment units and aquaculture cycles, as well as the failure to utilize wastewater nutrients as a resource.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a wastewater recycling system for aquaculture in saline-alkali land, comprising a shrimp pond, a pretreatment unit, a microbial treatment unit, a water quality conditioning and buffering unit, and a nutrient resource utilization unit; the system is a closed-loop circulation structure, wherein the wastewater output end of the shrimp pond is connected to the input end of the pretreatment unit, the output end of the pretreatment unit is connected to the input end of the microbial treatment unit, the output end of the microbial treatment unit is connected to the input end of the water quality conditioning and buffering unit, the output end of the water quality conditioning and buffering unit is connected to the input end of the nutrient resource utilization unit, and the output end of the nutrient resource utilization unit is connected to the recycled water input end of the shrimp pond; The pretreatment unit includes a screen and a sedimentation tank; the microbial treatment unit is a salt-tolerant microbial reaction tank, which is filled with a salt-alkali water modified composite packing material composed of zeolite, modified ceramsite and halophyte fiber, and the modified composite packing material is immobilized with a composite microbial community of halophilic denitrifying bacteria, salt-tolerant polyphosphate-accumulating bacteria and organic matter degrading bacteria. The water quality conditioning and buffer unit includes a salinity adjustment module, a pH adjustment module, and a dissolved oxygen adjustment module, and is equipped with a salinity sensor and a pH sensor for real-time monitoring of water quality parameters. The nutrient resource utilization unit includes a microalgae cultivation tank and a feed conversion module.

[0006] Preferably, the aperture of the grating is 1-3 mm, and the settling time in the sedimentation tank is 2-4 hours.

[0007] Preferably, the dissolved oxygen in the salt-tolerant microbial reaction tank is controlled at 2-3 mg / L, the temperature is controlled at 25-30℃, and the concentration of the composite microbial community is 10^8 CFU / m³.

[0008] Preferably, the water quality conditioning and buffering unit controls the salinity fluctuation of the recycled water within ±1% and stabilizes the pH at 7.0-8.0.

[0009] A method for recycling wastewater from aquaculture in saline-alkali land includes the following steps: S1. The aquaculture wastewater discharged from the shrimp pond is transported to the pretreatment unit. First, large suspended particles are removed by the screen, and then the wastewater is allowed to stand in the sedimentation tank for 2-4 hours to complete the wastewater pretreatment. S2. The pretreated effluent is transported to the salt-tolerant microbial reactor of the microbial treatment unit. The dissolved oxygen in the reactor is controlled at 2-3 mg / L and the temperature is controlled at 25-30℃. The organic matter, total nitrogen and total phosphorus in the effluent are degraded by the metabolic action of the composite microbial community. The treatment time is 8-12 hours, so that the COD in the effluent is ≤30 mg / L, TN is ≤5 mg / L and TP is ≤0.5 mg / L. S3. The treated wastewater is transported to the water quality conditioning and buffer unit. The water quality is monitored in real time by salinity and pH sensors. The salinity adjustment module and pH adjustment module are used to control the salinity fluctuation of the recycled water within ±1% and stabilize the pH at 7.0-8.0. The buffering time is 1-2 hours. S4. The conditioned wastewater is transported to the microalgae culture tank of the nutrient resource utilization unit. After inoculating microalgae and culturing for 3-5 days, the microalgae liquid is returned to the shrimp pond at a volume ratio of 5%-10% through the feed conversion module. The remaining conditioned wastewater is directly reused in the shrimp pond. S5. Repeat steps 1-4 to achieve closed-loop recycling of shrimp farming tailwater, and the system tailwater recycling rate is ≥90%.

[0010] Preferably, the complex microbial community in S2 includes halophilic denitrifying bacteria of the genus *Pseudomonas*, halophilic polyphosphate-accumulating bacteria of the genus *Acinetobacter*, and organic matter-degrading bacteria of the genus *Bacillus*, with an inoculation volume ratio of 2:2:1.

[0011] Preferably, the microalgae in S4 are Chlorella and Platycodon, with an inoculation volume ratio of 1:1 and an initial inoculation concentration of 10^6 cells / mL.

[0012] Preferably, during the microalgae cultivation process in S4, the temperature in the microalgae cultivation tank is controlled at 20-28℃ and the dissolved oxygen is controlled at 5-6 mg / L.

[0013] Preferably, the wastewater recycling rate of the system in S5 is ≥92%, and the volume ratio of microalgae liquid returned to the shrimp pond is 8%.

[0014] (III) Beneficial Effects This invention provides a system and method for recycling wastewater from aquaculture in saline-alkali land. It offers the following advantages: 1. This invention constructs a specialized composite salt-tolerant bacterial community for saline-alkali water and combines it with modified composite packing material. Utilizing the metabolic complementarity among the bacterial communities and the unique microenvironment of the packing material, it solves the problem of insufficient degradation capacity of single microorganisms in high-salt environments, significantly improving the removal efficiency of organic matter and nitrogen and phosphorus pollutants in the effluent. Simultaneously, the precise control design of the water quality conditioning and buffering unit effectively addresses the pain points of salinity and pH fluctuations in reclaimed water in existing technologies, avoiding stress responses in shrimp, ensuring the operational stability of the microbial treatment system and the safety of effluent reuse, and adapting to the special water quality requirements of shrimp farming in saline-alkali land.

[0015] 2. The nutrient resource utilization unit of this invention converts nitrogen and phosphorus nutrients in the tailwater into natural shrimp feed, realizing the resource utilization of tailwater nutrients. This reduces the amount of artificial feed required and lowers the environmental treatment costs caused by sludge production. Attached Figure Description

[0016] Figure 1 This is an overall flow chart of a wastewater recycling system and method for aquaculture in saline-alkali land proposed in this invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example: like Figure 1 As shown, this embodiment of the invention provides a wastewater recycling system for aquaculture in saline-alkali land, including a shrimp pond, a pretreatment unit, a microbial treatment unit, a water quality conditioning and buffering unit, and a nutrient resource utilization unit. The system is a closed-loop circulation structure, wherein the wastewater output end of the shrimp pond is connected to the input end of the pretreatment unit, the output end of the pretreatment unit is connected to the input end of the microbial treatment unit, the output end of the microbial treatment unit is connected to the input end of the water quality conditioning and buffering unit, the output end of the water quality conditioning and buffering unit is connected to the input end of the nutrient resource utilization unit, and the output end of the nutrient resource utilization unit is connected to the reclaimed water input end of the shrimp pond. The pretreatment unit includes a screen and a sedimentation tank; the microbial treatment unit is a salt-tolerant microbial reaction tank, which is filled with a salt-alkali water modified composite packing material composed of zeolite, modified ceramsite and halophyte fiber, and the modified composite packing material is immobilized with a complex microbial community of halophilic denitrifying bacteria, salt-tolerant polyphosphate-accumulating bacteria and organic matter degrading bacteria. The water quality conditioning and buffering unit includes a salinity adjustment module, a pH adjustment module, and a dissolved oxygen adjustment module, and is equipped with a salinity sensor and a pH sensor for real-time monitoring of water quality parameters. The nutrient resource utilization unit includes a microalgae cultivation tank and a feed conversion module.

[0019] The mesh size of the screen is 1-3mm, and the settling time in the sedimentation tank is 2-4 hours. The dissolved oxygen in the salt-tolerant microbial reaction tank is controlled at 2-3 mg / L, the temperature is controlled at 25-30℃, and the concentration of the complex bacterial community is 10^8 CFU / m.

[0020] The water quality conditioning and buffering unit controls the salinity fluctuation of the recycled water within ±1% and stabilizes the pH at 7.0-8.0.

[0021] A method for recycling wastewater from aquaculture in saline-alkali land includes the following steps: S1. The aquaculture wastewater discharged from the shrimp pond is transported to the pretreatment unit. First, large suspended particles are removed by the screen, and then the wastewater is allowed to stand in the sedimentation tank for 2-4 hours to complete the wastewater pretreatment. S2. The pretreated effluent is transported to the salt-tolerant microbial reactor of the microbial treatment unit. The dissolved oxygen in the reactor is controlled at 2-3 mg / L and the temperature is controlled at 25-30℃. The organic matter, total nitrogen and total phosphorus in the effluent are degraded by the metabolic action of the composite microbial community. The treatment time is 8-12 hours, so that the COD in the effluent is ≤30 mg / L, TN is ≤5 mg / L and TP is ≤0.5 mg / L. S3. The treated wastewater is transported to the water quality conditioning and buffer unit. The water quality is monitored in real time by salinity and pH sensors. The salinity adjustment module and pH adjustment module are used to control the salinity fluctuation of the recycled water within ±1% and stabilize the pH at 7.0-8.0. The buffering time is 1-2 hours. S4. The conditioned wastewater is transported to the microalgae culture tank of the nutrient resource utilization unit. After inoculating microalgae and culturing for 3-5 days, the microalgae liquid is returned to the shrimp pond at a volume ratio of 5%-10% through the feed conversion module. The remaining conditioned wastewater is directly reused in the shrimp pond. S5. Repeat steps 1-4 to achieve closed-loop recycling of shrimp farming tailwater, and the system tailwater recycling rate is ≥90%.

[0022] The complex microbial community in S2 includes halophilic denitrifying bacteria of the genus Pseudomonas, halophilic polyphosphate-accumulating bacteria of the genus Acinetobacter, and organic matter-degrading bacteria of the genus Bacillus, with an inoculation volume ratio of 2:2:1.

[0023] The microalgae in S4 are Chlorella and Platycodon, with an inoculation volume ratio of 1:1 and an initial inoculation concentration of 10^6 cells / mL.

[0024] During the microalgae cultivation process in S4, the temperature in the microalgae cultivation tank is controlled at 20-28℃ and the dissolved oxygen is 5-6 mg / L.

[0025] The wastewater recycling rate of the S5 system is ≥92%, and the volume ratio of microalgae liquid returned to the shrimp pond is 8%.

[0026] Comparative Example The technology commonly used in this field, namely "pretreatment + single-microbial activated sludge treatment + direct reuse", is adopted as follows: Pretreatment unit: Same as in Example 1 (grid + sedimentation tank).

[0027] Microbial treatment unit: Set up an activated sludge tank (volume 10m³), inoculate only a single type of Bacillus (concentration 10^8 CFU / mL), fill with conventional elastic packing material, control dissolved oxygen 2-3mg / L, temperature 25-30℃, and treatment time 10 hours.

[0028] Reuse process: The wastewater treated by microorganisms is directly transported back to the shrimp ponds without undergoing water quality conditioning or resource reuse.

[0029] Experimental example: (I) Experimental Design Two experimental groups were set up: an example group and a comparative group. Each group had three parallel experiments. The experimental period was 30 days. The following samples were collected and the indicators were detected synchronously every day: Pretreated effluent: The suspended solids removal rate was measured. Wastewater after microbial treatment: COD, TN, and TP removal rates were measured; Reclaimed water: Measure salinity and pH fluctuation range; Shrimp ponds: Statistics on shrimp survival rate, amount of artificial feed, and wastewater recycling rate.

[0030] (II) Detection Methods Suspended solids (SS): Gravimetric method (GB / T11901-1989); COD: Potassium dichromate method (GB / T11914-1989). TN: Alkaline potassium persulfate digestion ultraviolet spectrophotometry (GB / T11894-1989); TP: Ammonium molybdate spectrophotometric method (GB / T11893-1989). Shrimp survival rate: Daily count of surviving shrimp / initial stocking quantity × 100%; Recycling rate: reused wastewater volume / total discharged wastewater volume × 100%.

[0031] (III) Experimental Procedure Two sets of experimental systems were started and run according to the methods of Example 1 and the comparative example, respectively. Water samples are collected from each unit at 9:00 AM daily, and water quality indicators are tested according to national standards. Record the amount of shrimp fed and the number of surviving shrimp daily. Calculate the average survival rate and the amount of feed after the experiment. After the experiment was completed, the wastewater recycling rate of the two systems was statistically analyzed.

[0032] Water treatment effect comparison: Table 1. Comparison of water quality treatment indicators between the examples and the comparative examples: Comparison of breeding benefits and resource utilization Table 2 Comparison of aquaculture and resource utilization indicators between the examples and comparative examples: This invention significantly improves the removal efficiency of COD, TN, and TP in shrimp tail water in saline-alkali land through a microbial treatment unit consisting of a composite microbial community and modified filler, and solves the problem of insufficient degradation capacity of conventional single microbial treatment in high-salt environments. The water quality conditioning and buffering unit effectively controls the salinity and pH fluctuations of the recycled water, avoids stress on shrimp, and significantly improves the survival rate of shrimp. The nutrient resource utilization unit converts nitrogen and phosphorus in the tailwater into natural feed for shrimp, reducing the amount of artificial feed required and improving the tailwater recycling rate, making it suitable for the actual scenario of water shortage in saline-alkali land.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A saline-alkaline water aquaculture tail water recycling treatment system, characterized in that, The system comprises a shrimp pond, a pretreatment unit, a microbial treatment unit, a water quality conditioning buffer unit, and a nutrient resource unit; the system is a closed loop circulation structure, wherein the tail water output end of the shrimp pond is communicated with the input end of the pretreatment unit, the output end of the pretreatment unit is communicated with the input end of the microbial treatment unit, the output end of the microbial treatment unit is communicated with the input end of the water quality conditioning buffer unit, the output end of the water quality conditioning buffer unit is communicated with the input end of the nutrient resource unit, and the output end of the nutrient resource unit is communicated with the reuse water input end of the shrimp pond; The pretreatment unit comprises a grid and a sedimentation tank; the microbial treatment unit is a salt-tolerant microbial reaction tank, the salt-tolerant microbial reaction tank is filled with a saline-alkali water modification composite filler composed of zeolite, modified ceramic and halophyte fiber, and the modified composite filler is fixed with a complex bacterial community of halophilic denitrifying bacteria, salt-tolerant phosphorus accumulating bacteria and organic matter degrading bacteria; The water quality conditioning buffer unit comprises a salinity adjustment module, a pH adjustment module and a dissolved oxygen adjustment module, and is provided with a salinity sensor and a pH sensor for real-time monitoring of water quality parameters; The nutrient resource unit comprises a microalgae culture tank and a bait conversion module.

2. The system according to claim 1, wherein: The grid has a pore size of 1-3 mm, and the sedimentation tank has a standing time of 2-4 hours.

3. The system according to claim 1, wherein: The dissolved oxygen in the salt-tolerant microbial reaction tank is controlled at 2-3 mg / L, the temperature is controlled at 25-30℃, and the concentration of the complex bacterial community is 10^8 CFU / m.

4. The system according to claim 1, wherein: The salinity fluctuation of the reuse water is controlled within ±1% and the pH is stabilized at 7.0-8.0 by the water quality conditioning buffer unit.

5. A method for treating tail water of saline-alkali water aquaculture based on the system of claim 1, characterized in that, The method comprises the following steps: S1, delivering the aquaculture tail water discharged from the shrimp pond to the pretreatment unit, removing large particle suspended solids through the grid, and then standing in the sedimentation tank for 2-4 hours to complete the tail water pretreatment; S2, delivering the pretreated tail water to the salt-tolerant microbial reaction tank of the microbial treatment unit, controlling the dissolved oxygen in the reaction tank to be 2-3 mg / L and the temperature to be 25-30℃, degrading the organic matter, total nitrogen and total phosphorus in the tail water through the metabolic action of the complex bacterial community, and treating for 8-12 hours to make the COD in the tail water ≤30 mg / L, the TN ≤5 mg / L and the TP ≤0.5 mg / L; S3, delivering the microbially treated tail water to the water quality conditioning buffer unit, real-time monitoring the water quality through the salinity sensor and the pH sensor, controlling the salinity fluctuation of the reuse water within ±1% and stabilizing the pH at 7.0-8.0 through the salinity adjustment module and the pH adjustment module, and buffering for 1-2 hours; S4, delivering the conditioned tail water to the microalgae culture tank of the nutrient resource unit, inoculating microalgae and culturing for 3-5 days, then returning the microalgae liquid to the shrimp pond at a volume ratio of 5%-10% through the bait conversion module, and directly recycling the remaining conditioned tail water to the shrimp pond; S5, repeating steps 1-4 to realize the closed loop circulation treatment of the shrimp tail water, and the system tail water recycling rate is ≥90%.

6. The method according to claim 5, wherein the method is characterized by: The complex bacterial community in S2 comprises halophilic denitrifying bacteria of Pseudomonas, salt-tolerant phosphorus accumulating bacteria of Acinetobacter and organic matter degrading bacteria of Bacillus, and the inoculation volume ratio of the three is 2:2:

1.

7. The method according to claim 5, wherein the method is characterized by: The microalgae in the S4 are Chlorella and Platymonas, and the inoculation volume ratio of the two is 1:1, and the initial inoculation concentration is 10^6 cells / mL.

8. The method according to claim 5, wherein the method is characterized by: In the microalgae culture process in the S4, the temperature in the microalgae culture pool is controlled to be 20-28℃, and the dissolved oxygen is 5-6 mg / L.

9. The method according to claim 5, wherein the method is characterized by: The tail water recycling rate of the system in the S5 is ≥92%, and the volume ratio of the microalgae liquid returned to the shrimp pond is 8%.

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