Harmless treatment method for aquaculture sewage

Abstract

The invention relates to a harmless treatment method of aquaculture sewage, which comprises the following steps: (1) gathering the aquaculture sewage, enabling the aquaculture sewage to flow into a sewage collecting tank provided with a grid, adding a microbial preparation at one time, and then enabling the aquaculture sewage to enter a precipitation filtering tank from the sewage collecting tank through a pipeline; (2) a flocculating agent is continuously added into the sewage, the sewage is continuously aerated with air while the flocculating agent is added, and the retention time of the sewage in the flocculation basin is 5-15 minutes; (3) standing the aquaculture sewage entering the precipitation and filtration tank for 1-2 hours, and then pumping supernatant clear water in the precipitation and filtration tank into a culture pond for culture production after membrane filtration treatment; sludge settled at the bottom of the settling and filtering tank enters sludge drying equipment through a sludge pump to be dehydrated and then is used as seawater pond fertilizer water or used as farmland fertilizer after desalination treatment. According to the invention, aquaculture pollution can be effectively degraded, the cost is low, and aquaculture sewage can be reasonably utilized.

Description

Technical Field

[0001] The invention belongs to the field of aquaculture pond sewage treatment, and in particular relates to a harmless treatment method for aquaculture sewage. Background Art

[0002] Aquaculture provides high-quality animal protein for humans and plays an important role in solving the global food problem. The output of aquatic products in my country has been increasing year by year. At the same time, the environmental problems caused by the discharge of aquaculture tailwater containing a large amount of organic pollutants such as leftover bait and feces have attracted widespread attention, and the treatment of aquaculture tailwater has received more and more attention.

[0003] At present, the treatment modes for aquaculture wastewater at home and abroad mainly include the return to farmland mode, natural treatment mode and industrial treatment mode. The return to farmland mode refers to the direct application of wastewater to the land. This mode has the advantages of simplicity and economy, but it occupies a large area and has low resource recovery efficiency. It can no longer meet the wastewater treatment requirements of the modern intensive aquaculture industry. The industrial treatment mode refers to a method that uses anaerobic, aerobic, anaerobic-aerobic and other processes to treat aquaculture wastewater for the purpose of meeting discharge standards. It is the main treatment method in Europe and the United States. Its main defects are high operating energy consumption and high treatment costs. In addition, the treatment cost of residual sludge is equivalent to the cost of wastewater treatment. Moreover, this mode uses biochemical treatment alone without considering resource recycling, which does not meet the development needs of my country's aquaculture industry at this stage. The natural treatment mode refers to the use of natural treatment methods such as oxidation ponds, land treatment or artificial wetland systems to treat aquaculture wastewater. However, the effect of using this mode to treat organic matter is not ideal.

[0004] Therefore, it is of great significance to develop a method that can effectively degrade aquaculture pollution, has low cost, and can reasonably utilize aquaculture wastewater. Summary of the invention

[0005] The following is a summary of some aspects of the present invention, but is not intended to limit the present invention. When there is a discrepancy between the disclosure of this specification and the referenced document, the disclosure of this specification shall prevail.

[0006] One of the purposes of the present invention is to provide a harmless treatment method for aquaculture wastewater, which can effectively degrade aquaculture pollution, has low cost, and can reasonably utilize aquaculture wastewater.

[0007] In order to solve the above technical problems, the present invention adopts the following technical scheme, a method for harmless treatment of aquaculture wastewater, comprising the following steps:

[0008] (1) The aquaculture wastewater is collected and flowed into a sewage collection tank equipped with a screen, and a microbial agent is added at one time, and then enters the sedimentation and filtration tank through a pipeline from the sewage collection tank;

[0009] (2) Continuously add flocculant into the sewage. While adding the flocculant, continuously aerate the sewage with air. The residence time of the sewage in the flocculation tank is 5 - 15 minutes;

[0010] (3) Let the aquaculture sewage entering the sedimentation and filtration tank stand for 1 - 2 hours. Then, the upper clear water in the sedimentation and filtration tank is pumped into the aquaculture pond for aquaculture production after membrane filtration treatment; The sludge settled at the bottom of the sedimentation and filtration tank enters the sludge drying equipment through a sludge pump for dehydration, and is used for fertilizing seawater ponds or used as farmland fertilizer after desalination treatment.

[0011] Furthermore, in the above step (1), the microbial agent is a composite microbial community, which is composed of photosynthetic bacteria, nitrifying bacteria, and Bacillus subtilis; The composite microbial community embedding bead material has a double-layer embedding structure, with the inner core being Bacillus subtilis and the outer layer being photosynthetic bacteria and nitrifying bacteria; The particle size of the composite microbial community is 2 - 8 mm, and the shape is spherical.

[0012] Furthermore, in the above step (1), for the composite microbial community, the mass ratio of photosynthetic bacteria, Bacillus subtilis, and nitrifying bacteria is 1:0.5 - 2.0:0.5 - 2.0, and preferably the mass ratio of photosynthetic bacteria, Bacillus subtilis, and nitrifying bacteria is 1:0.8:1.

[0013] Furthermore, the specific preparation steps of the composite microbial community embedding beads are as follows:

[0014] (a) After subjecting the Bacillus subtilis to coagulation, drying, and sieving treatments, prepare the inner core of the composite microbial community embedding beads;

[0015] (b) After centrifuging and rinsing the photosynthetic bacteria and nitrifying bacteria, add the embedding agent and stir evenly to prepare a bacteria-colloid mixture. Among them, the photosynthetic bacteria: nitrifying bacteria: embedding agent are mixed evenly according to the mass ratio of 1:0.5 - 2.0:3 - 7; In the embedding agent, the mass ratio of polyvinyl alcohol: sodium alginate: water is 5:0.2 - 0.7:70 - 120.

[0016] (c) Place the inner core of the composite microbial community embedding beads in a spherical hollow mold, inject the bacteria-colloid mixture, and at the same time inject the fixing agent and roll the spherical hollow mold for 1 - 2 hours. Then, inject the fixing agent again and roll the spherical hollow mold for 6 - 12 hours. After taking it out, obtain the composite microbial community embedding beads through stirring, screening, and activation steps. Among them, the mass ratio of the embedding agent and the fixing agent in the spherical hollow mold is 1:2 - 5, and the fixing agent is a saturated boric acid + KCl solution; The activation is to culture the prepared composite microbial community embedding beads under the conditions of pH = 7 - 8, dissolved oxygen 3 - 5 mg / L, and water temperature 20 - 30 °C for 1 - 3 days.

[0017] Further, the specific preparation steps of the composite microbial community-embedded pellets are as follows:

[0018] (a) After subjecting the Bacillus subtilis to coagulation, drying, and sieving, the core of the composite microbial community-embedded pellets is prepared.

[0019] (b) After centrifuging and rinsing the photosynthetic bacteria and nitrifying bacteria groups, an embedding agent is added and stirred evenly to prepare a bacteria-colloid mixed solution, wherein the photosynthetic bacteria: nitrifying bacteria groups: embedding agent are mixed evenly according to a mass ratio of 1:1:5; in the embedding agent, the mass ratio of polyvinyl alcohol: sodium alginate: water is 5:0.5:100.

[0020] (c) The core of the composite microbial community-embedded pellets is placed in a spherical hollow mold, the bacteria-colloid mixed solution is injected, and at the same time a fixing agent is injected and the spherical hollow mold is rotated for 1 to 2 hours, then the fixing agent is injected again, and the spherical hollow mold is rotated for 6 to 12 hours. After taking out, the composite microbial community-embedded pellets are obtained through stirring, screening, and activation steps, wherein the mass ratio of the embedding agent to the fixing agent in the spherical hollow mold is 1:3, and the fixing agent is a saturated boric acid + KCl solution; the activation is to culture the prepared composite microbial community-embedded pellets under the conditions of pH = 7.5, dissolved oxygen 4 mg / L, and water temperature 25 °C for 2 days.

[0021] Further, the diameter of the core of the composite microbial community-embedded pellets is 1 to 4 mm, the outer layer thickness is 1 to 4 mm, the porosity is 30% to 70%, and the specific surface area is 15 to 30 m 2 / g.

[0022] Further, the diameter of the core of the composite microbial community-embedded pellets is 2 mm, the outer layer thickness is 4 mm, the porosity is 50%, and the specific surface area is 20 m 2 / g.

[0023] Further, in the above step (2), the flocculant is a mixture of cyanobacteria metabolites and fermentation broth, wherein the fermentation broth components are corn straw, sweet potato vines, sawdust, cactus, houttuynia cordata, artemisia argyi, and yeast powder.

[0024] Further, the mass ratio of the cyanobacteria metabolites to the fermentation broth in the flocculant is 1:2 to 5; preferably, the mass ratio of the cyanobacteria metabolites to the fermentation broth is 1:3.

[0025] Further, the preparation method of the cyanobacteria metabolites is to transfer cyanobacteria to Zarrouk medium for culture, add diethylaminoacetaldehyde diethyl acetal strengthening agent, and the culture conditions are: growth temperature 25 to 27 °C, pH value 8 to 9, light intensity 3000 lx, and light-dark ratio 12 h:12 h; the cyanobacteria cultured to the stationary phase are centrifuged at 4000 to 5000 rpm for 20 min to remove the algal bodies, and the supernatant is reserved for use.

[0026] Further, the preparation method of the fermentation broth is as follows: Weigh the following components by mass: 25 parts of corn straw, 25 parts of sweet potato stems and leaves, 15 parts of sawdust, 15 parts of cactus, 12 parts of Houttuynia cordata, 4 parts of Artemisia argyi, and 4 parts of yeast powder. Mash or crush the weighed components above and mix them evenly. Add purified water with the same mass as the mixed components to the mixed components, mix well, put them into a glass container, seal the glass container, ferment in the dark at 100 - 120 rpm and 20°C - 25°C for 24 hours, and then ferment in the dark at 140 - 160 rpm and 25°C - 27°C for 36 - 48 hours. Sieve the fermentation product through a 100 - mesh sieve to obtain the fermentation broth.

[0027] Further, the concentration of the flocculant added to the sewage is 30 - 70 mg / L, preferably 50 mg / L.

[0028] Further, in the above step (3), the membrane is a microfiltration membrane or an ultrafiltration membrane.

[0029] Further, the method for making farmland fertilizer from the sedimentation sludge in step (3) is as follows: a. Dry the sedimented sludge at a temperature of 70 - 90°C and crush it; b. Remove the salt in the sludge: Add clear water with a weight 2 - 7 times that of the sludge to the crushed sludge, mix well, stir at a speed of 70 - 90 rpm for 20 minutes, filter the washed sludge by suction, and dry it at a temperature of 60 - 80°C until the water content is 15 - 20%, and then crush it; c. Dry the filter residue obtained in step (3) at a temperature of 60 - 80°C until the water content is 15 - 20%, and then crush it; d. Mix the dried filter residue and the dried sludge obtained in step b in a ratio of 0.5 - 2:1 to obtain a dried mixture; e. Put the dried mixture into a granulator to granulate, obtain particles with a diameter less than or equal to 1 mm, inspect, package, and store in a warehouse.

[0030] Further, in step d, the dried filter residue and the dried sludge obtained in step b are mixed evenly in a ratio of 1:1.

[0031] Further, the membrane is a microfiltration membrane or an ultrafiltration membrane; the method for making farmland fertilizer from the sedimentation sludge is as follows: a. Dry the sedimented sludge at a temperature of 80°C and crush it; b. Remove the salt in the sludge: Add clear water with a weight 5 times that of the sludge to the crushed sludge, mix well, stir at a speed of 80 rpm for 20 minutes, filter the washed sludge by suction, and dry it at a temperature of 70°C until the water content is 18%, and then crush it; c. Dry the filter residue obtained in step (3) at a temperature of 70°C until the water content is 18%, and then crush it; d. Mix the dried filter residue and the dried sludge obtained in step b in a ratio of 1:1 to obtain a dried mixture; e. Put the dried mixture into a granulator to granulate, obtain particles with a diameter less than or equal to 1 mm, inspect, package, and store in a warehouse.

[0032] Beneficial technical effects of the present invention

[0033] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0034] 1. The present invention can effectively degrade aquaculture pollution, has low cost, and can reasonably utilize aquaculture sewage. Among them, the grille can be used for pretreatment to remove insoluble solid particulate matter in the sewage. The separated solid particulate matter can be used for fertilizing seawater ponds or as organic fertilizer for growing crops. By the grille, part of the organic matter in the sewage can be removed, reducing the subsequent sewage treatment load and cost. By adding a microbial preparation, especially the microbial preparation being a composite microbial community embedded in a spherical material with a double-layer embedding structure, with the inner core being Bacillus subtilis and the outer layer being photosynthetic bacteria and nitrifying bacteria, the simultaneous removal of organic matter and nitrite is achieved. This embedding method has clear zoning and good treatment effects. During the flocculation treatment process, air aeration treatment is continuously carried out to provide the oxygen required for biochemical treatment and can cause part of the ammonia nitrogen to escape from the water surface. Thus, the effect of biological sewage treatment is greatly improved.

[0035] 2. Cyanobacteria not only have a wide source and are easy to culture, but also have important health care value and medicinal value. Among them, the metabolites of cyanobacteria can be mixed with the fermentation broth in a specific ratio to prepare a flocculant. During the preparation process of the cyanobacteria metabolites, diethylaminoacetaldehyde acetal is added as a strengthening agent to activate the cyanobacteria and their metabolites. The finally formed flocculant has good flocculation effect, can effectively remove the organic matter in aquaculture sewage, degrade aquaculture pollution, with the removal rate of suspended solids SS reaching 95.8 - 98.3%, the removal rate of chemical oxygen demand COD reaching 89.8 - 93.5%, and the removal rate of BOD reaching 91.5 - 94.8%. It also has good turbidity removal and decolorization performance, fully exerting the synergistic effect among them. And the sources of each component are wide, the cost is low, and they are all environmentally friendly and non-toxic, without causing secondary pollution to the environment.

[0036] 3. Cactus, Houttuynia cordata and Artemisia argyi are added to the fermented product for preparing the fermentation broth. The prepared fermentation product has the effect of sterilization and antibacterial, and has a certain inhibitory effect on harmful microorganisms, parasites, etc. in aquaculture sewage. The advantage of membrane filtration treatment is that it first completes the separation of pollutants, ensures that the effluent does not contain pathogenic bacteria, etc., without the need to additionally increase a sterilization device. Secondly, it ensures that the microbial preparation does not flow out and can be reused repeatedly. The clarified water passing through can be directly discharged or returned to the culture pond for reuse. Thus, the recycling of water resources is realized. The sludge obtained by sedimentation can be used for fertilizing seawater ponds or used as farmland fertilizer after desalination treatment, improving the utilization rate of resources. Detailed implementation manners

[0037] Unless otherwise specified or there is an obvious conflict in the context, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. In case of contradiction, the definitions provided in this application shall prevail. When trade names appear in this text, they are intended to refer to the corresponding products or their active ingredients. All patents, published patent applications, and publications cited herein are incorporated herein by reference.

[0038] Example 1:

[0039] 1. Preparation of microbial agent

[0040] The microbial agent is a composite microbial community composed of photosynthetic bacteria, nitrifying bacteria, and Bacillus subtilis. The composite microbial community embedding pellet material has a double-layer embedding structure, with the inner core being Bacillus subtilis and the outer layer being photosynthetic bacteria and nitrifying bacteria; the particle size of the composite microbial community is 2 - 8 mm, and the shape is spherical. Among them, the mass ratio of photosynthetic bacteria, Bacillus subtilis, and nitrifying bacteria is 1:0.8:1; the specific preparation method is as follows:

[0041] (a) After subjecting the Bacillus subtilis to coagulation, drying, and sieving treatments, the inner core of the composite microbial community embedding pellet is prepared.

[0042] (b) After centrifuging and rinsing the photosynthetic bacteria and nitrifying bacteria, an embedding agent is added and stirred evenly to obtain a bacteria - glue mixture. Among them, the photosynthetic bacteria: nitrifying bacteria: embedding agent are mixed evenly according to a mass ratio of 1:1:5; in the embedding agent, the mass ratio of polyvinyl alcohol: sodium alginate: water is 5:0.5:100.

[0043] (c) Place the inner core of the composite microbial community embedding pellet in a spherical hollow mold, inject the bacteria - glue mixture, and at the same time inject a fixing agent and roll the spherical hollow mold for 1 - 2 hours, then inject the fixing agent again and roll the spherical hollow mold for 6 - 12 hours. After taking it out, through stirring, screening, and activation steps, the composite microbial community embedding pellet is obtained. Among them, the mass ratio of the embedding agent and the fixing agent in the spherical hollow mold is 1:3, and the fixing agent is a saturated boric acid + KCl solution; the activation is to culture the prepared composite microbial community embedding pellet under the conditions of pH = 7.5, dissolved oxygen 4 mg / L, and water temperature 25 °C for 2 days. The diameter of the inner core of the prepared composite microbial community embedding pellet is 2 mm, the outer layer thickness is 4 mm, the porosity is 50%, and the specific surface area is 20 m 2 / g.

[0044] 2. Preparation of flocculant

[0045] 1. The flocculant is a mixture of cyanobacteria metabolites and fermentation broth. The components of the fermentation broth are corn straw, sweet potato vine leaves, sawdust, cactus, houttuynia cordata, mugwort leaf, and yeast powder; the mass ratio of cyanobacteria metabolites to fermentation broth is 1:3.

[0046] 2. The method for preparing cyanobacterial metabolites is to transfer the cyanobacteria to Zarrouk medium for cultivation, add diethylaminoacetaldehyde diethyl acetal enhancer, and the culture conditions are: growth temperature 25-27°C, pH 8-9, light intensity 3000lx, light-dark ratio of 12h:12h; the cyanobacteria cultured to the stable period are centrifuged at 4000-5000rpm for 20min, the algae are removed, and the supernatant is retained for later use.

[0047] 3. The preparation method of the fermentation liquid is as follows: weigh the following components in parts by mass: 25 parts of corn stalks, 25 parts of sweet potato stems and leaves, 15 parts of sawdust, 15 parts of cactus, 12 parts of Houttuynia cordata, 4 parts of wormwood, and 4 parts of yeast powder, crush or grind the weighed components and mix them evenly, add purified water of the same mass as the mixed components to the mixed components, put them into a glass container after mixing, seal the glass container, ferment in the dark at 100-120rpm and 20℃-25℃ for 24 hours, then ferment in the dark at 140-160rpm and 25℃-27℃ for 36-48 hours, and pass the fermentation product through a 100 sieve to obtain the fermentation liquid.

[0048] 3. A method for harmless treatment of aquaculture wastewater, comprising the following steps:

[0049] (1) The aquaculture wastewater is collected and flowed into a sewage collection tank equipped with a screen, and a microbial agent is added at one time, and then enters the sedimentation and filtration tank through a pipeline from the sewage collection tank;

[0050] (2) Continuously adding flocculants to the sewage, and at the same time, continuously aerating the sewage with air, the residence time of the sewage in the flocculation tank is 5 to 15 minutes, and the concentration of the flocculants added to the sewage is 50 mg / L;

[0051] (3) The aquaculture wastewater entering the sedimentation and filtration tank is left to stand for 1-2 hours, and then the upper clear water in the sedimentation and filtration tank is treated by membrane filtration and pumped into the aquaculture pond for aquaculture production; the sludge settled at the bottom of the sedimentation and filtration tank is pumped into the sludge drying equipment for dehydration, and then used as fertilizer water for seawater ponds or used as farmland fertilizer after desalination treatment.

[0052] Among them, the membrane is a microfiltration membrane or an ultrafiltration membrane; the method for making farmland fertilizer from sedimented sludge is as follows: a. Dry and crush the sedimented sludge at a temperature of 80°C; b. Remove the salts in the sludge: Add 5 times the weight of the sludge in clear water to the crushed sludge, mix well, stir at a speed of 80 rpm for 20 minutes, filter the washed sludge by suction, dry it at a temperature of 70°C until the water content is 18%, and crush it; c. Dry the filter residue obtained in step (3) at a temperature of 70°C until the water content is 18%, and crush it; d. Mix the dried filter residue and the dried sludge obtained in step b in a ratio of 1:1 to obtain a dried mixture; e. Put the dried mixture into a granulator for granulation to obtain particles with a diameter less than or equal to 1 mm, and then inspect, package, and store them in a warehouse.

[0053] Example 2:

[0054] 1. Preparation of microbial agent

[0055] The microbial agent is a composite microbial community composed of photosynthetic bacteria, nitrifying bacteria, and Bacillus subtilis. The composite microbial community embedding beads have a double-layer embedding structure. The inner core is Bacillus subtilis, and the outer layer is photosynthetic bacteria and nitrifying bacteria; the particle size of the composite microbial community is 2 - 8 mm, and the shape is spherical. Among them, the mass ratio of photosynthetic bacteria, Bacillus subtilis, and nitrifying bacteria is 1:0.5:0.5; the specific preparation method is as follows:

[0056] (a) After coagulation, drying, and sieving treatment of the Bacillus subtilis, the inner core of the composite microbial community embedding beads is prepared.

[0057] (b) After centrifugation and rinsing of the photosynthetic bacteria and nitrifying bacteria, add an embedding agent and stir evenly to obtain a bacteria-colloid mixture. Among them, the photosynthetic bacteria: nitrifying bacteria: embedding agent are mixed evenly in a mass ratio of 1:0.5:3; the mass ratio of polyvinyl alcohol: sodium alginate: water in the embedding agent is 5:0.2:70.

[0058] (c) Place the inner core of the composite microbial community embedding beads in a spherical hollow mold, inject the bacteria-colloid mixture, and at the same time inject a fixing agent and roll the spherical hollow mold for 1 - 2 hours, then inject the fixing agent again, and roll the spherical hollow mold for 6 - 12 hours. After taking it out, through stirring, screening, and activation steps, the composite microbial community embedding beads are obtained. Among them, the mass ratio of the embedding agent and the fixing agent in the spherical hollow mold is 1:2, and the fixing agent is a saturated boric acid + KCl solution; the activation is to culture the prepared composite microbial community embedding beads under the conditions of pH = 7, dissolved oxygen 3 mg / L, and water temperature 20°C for 1 day. The diameter of the inner core of the prepared composite microbial community embedding beads is 2 mm, the outer layer is 4 mm thick, the porosity is 30%, and the specific surface area is 15 m 2 / g.

[0059] 2. Preparation of flocculant

[0060] 1. The flocculant is a mixture of cyanobacteria metabolites and fermentation liquid, wherein the fermentation liquid components are corn straw, sweet potato stems and leaves, sawdust, cactus, houttuynia cordata, wormwood leaves, and yeast powder; the mass ratio of cyanobacteria metabolites to fermentation liquid is 1:2.

[0061] 2. The method for preparing cyanobacterial metabolites is to transfer the cyanobacteria to Zarrouk medium for cultivation, add diethylaminoacetaldehyde diethyl acetal enhancer, and the culture conditions are: growth temperature 25-27°C, pH 8-9, light intensity 3000lx, light-dark ratio of 12h:12h; the cyanobacteria cultured to the stable period are centrifuged at 4000-5000rpm for 20min, the algae are removed, and the supernatant is retained for later use.

[0062] 3. The preparation method of the fermentation liquid is as follows: weigh the following components in parts by mass: 25 parts of corn stalks, 25 parts of sweet potato stems and leaves, 15 parts of sawdust, 15 parts of cactus, 12 parts of Houttuynia cordata, 4 parts of wormwood, and 4 parts of yeast powder, crush or grind the weighed components and mix them evenly, add purified water of the same mass as the mixed components to the mixed components, put them into a glass container after mixing, seal the glass container, ferment in the dark at 100-120rpm and 20℃-25℃ for 24 hours, then ferment in the dark at 140-160rpm and 25℃-27℃ for 36-48 hours, and pass the fermentation product through a 100 sieve to obtain the fermentation liquid.

[0063] 3. A method for harmless treatment of aquaculture wastewater, comprising the following steps:

[0064] (1) The aquaculture wastewater is collected and flowed into a sewage collection tank equipped with a screen, and a microbial agent is added at one time, and then enters the sedimentation and filtration tank through a pipeline from the sewage collection tank;

[0065] (2) Continuously adding flocculants to the sewage, and at the same time, continuously aerating the sewage with air, the residence time of the sewage in the flocculation tank is 5 to 15 minutes, and the concentration of the flocculants added to the sewage is 30 mg / L;

[0066] (3) The aquaculture wastewater entering the sedimentation and filtration tank is left to stand for 1-2 hours, and then the upper clear water in the sedimentation and filtration tank is treated by membrane filtration and pumped into the aquaculture pond for aquaculture production; the sludge settled at the bottom of the sedimentation and filtration tank is pumped into the sludge drying equipment for dehydration, and then used as fertilizer water for seawater ponds or used as farmland fertilizer after desalination treatment.

[0067] Among them, the membrane is a microfiltration membrane or an ultrafiltration membrane; the method for making farmland fertilizer from sedimented sludge is as follows: a. Dry and crush the sedimented sludge at a temperature of 70°C; b. Remove the salts in the sludge: Add clear water twice the weight of the sludge to the crushed sludge, mix well, stir at a speed of 80 rpm for 20 minutes, filter the washed sludge by suction, dry it at a temperature of 60°C until the water content is 15%, and crush it; c. Dry the filter residue obtained in step (3) at a temperature of 60°C until the water content is 15%, and crush it; d. Mix the dried filter residue and the dried sludge obtained in step b in a ratio of 0.5:1 to obtain a dried mixture; e. Put the dried mixture into a granulator to granulate, obtain particles with a diameter less than or equal to 1 mm, inspect, package, and store in the warehouse.

[0068] Example 3:

[0069] 1. Preparation of microbial agent

[0070] The microbial agent is a composite microbial community composed of photosynthetic bacteria, nitrifying bacteria, and Bacillus subtilis. The composite microbial community embedding bead material has a double-layer embedding structure, with the inner core being Bacillus subtilis and the outer layer being photosynthetic bacteria and nitrifying bacteria; the composite microbial community has a particle size of 2 - 8 mm and a spherical shape. Among them, the mass ratio of photosynthetic bacteria, Bacillus subtilis, and nitrifying bacteria is 1:2:2; the specific preparation method is as follows:

[0071] (a) After coagulation, drying, and sieving treatment of the Bacillus subtilis, the inner core of the composite microbial community embedding bead is prepared.

[0072] (b) After centrifugation and rinsing of the photosynthetic bacteria and nitrifying bacteria, add an embedding agent and stir evenly to obtain a bacteria-colloid mixture. Among them, the photosynthetic bacteria: nitrifying bacteria: embedding agent are mixed evenly in a mass ratio of 1:2:7; in the embedding agent, the mass ratio of polyvinyl alcohol: sodium alginate: water is 5:0.7:120.

[0073] (c) Place the inner core of the composite microbial community embedding bead in a spherical hollow mold, inject the bacteria-colloid mixture, inject a fixing agent at the same time, and roll the spherical hollow mold for 1 - 2 hours, then inject the fixing agent again, and roll the spherical hollow mold for 6 - 12 hours. After taking it out, through stirring, screening, and activation steps, the composite microbial community embedding bead is obtained. Among them, the mass ratio of the embedding agent and the fixing agent in the spherical hollow mold is 1:5, and the fixing agent is a saturated boric acid + KCl solution; the activation is to culture the prepared composite microbial community embedding bead under the conditions of pH = 8, dissolved oxygen 5 mg / L, and water temperature 30°C for 3 days. The diameter of the inner core of the prepared composite microbial community embedding bead is 2 mm, the outer layer is 4 mm thick, the porosity is 70%, and the specific surface area is 30 m 2 / g.

[0074] 2. Preparation of flocculant

[0075] 1. The flocculant is a mixture of cyanobacteria metabolites and fermentation liquid, wherein the fermentation liquid components are corn straw, sweet potato stems and leaves, sawdust, cactus, houttuynia cordata, wormwood leaves, and yeast powder; the mass ratio of cyanobacteria metabolites to fermentation liquid is 1:5.

[0076] 2. The method for preparing cyanobacterial metabolites is to transfer the cyanobacteria to Zarrouk medium for cultivation, add diethylaminoacetaldehyde diethyl acetal enhancer, and the culture conditions are: growth temperature 25-27°C, pH 8-9, light intensity 3000lx, light-dark ratio of 12h:12h; the cyanobacteria cultured to the stable period are centrifuged at 4000-5000rpm for 20min, the algae are removed, and the supernatant is retained for later use.

[0077] 3. The preparation method of the fermentation liquid is as follows: weigh the following components in parts by mass: 25 parts of corn stalks, 25 parts of sweet potato stems and leaves, 15 parts of sawdust, 15 parts of cactus, 12 parts of Houttuynia cordata, 4 parts of wormwood, and 4 parts of yeast powder, crush or grind the weighed components and mix them evenly, add purified water of the same mass as the mixed components to the mixed components, put them into a glass container after mixing, seal the glass container, ferment in the dark at 100-120rpm and 20℃-25℃ for 24 hours, then ferment in the dark at 140-160rpm and 25℃-27℃ for 36-48 hours, and pass the fermentation product through a 100 sieve to obtain the fermentation liquid.

[0078] 3. A method for harmless treatment of aquaculture wastewater, comprising the following steps:

[0079] (1) The aquaculture wastewater is collected and flowed into a sewage collection tank equipped with a screen, and a microbial agent is added at one time, and then enters the sedimentation and filtration tank through a pipeline from the sewage collection tank;

[0080] (2) Continuously adding flocculants to the sewage, and at the same time, continuously aerating the sewage with air, the residence time of the sewage in the flocculation tank is 5 to 15 minutes, and the concentration of the flocculants added to the sewage is 70 mg / L;

[0081] (3) The aquaculture wastewater entering the sedimentation and filtration tank is left to stand for 1-2 hours, and then the upper clear water in the sedimentation and filtration tank is treated by membrane filtration and pumped into the aquaculture pond for aquaculture production; the sludge settled at the bottom of the sedimentation and filtration tank is pumped into the sludge drying equipment for dehydration, and then used as fertilizer water for seawater ponds or used as farmland fertilizer after desalination treatment.

[0082] Among them, the membrane is a microfiltration membrane or an ultrafiltration membrane; the method for making farmland fertilizer from sedimented sludge is as follows: a. Dry the sedimented sludge at 90°C and crush it; b. Remove the salts in the sludge: Add 7 times the weight of the sludge in clear water to the crushed sludge, mix well, stir at a speed of 90 rpm for 20 minutes, filter the washed sludge, and dry it at 80°C until the water content is 20%, then crush it; c. Dry the filter residue obtained in step (3) at 80°C until the water content is 20%, and crush it; d. Mix the dried filter residue and the dried sludge obtained in step b in a ratio of 2:1 to obtain a dried mixture; e. Put the dried mixture into a granulator for granulation to obtain particles with a diameter less than or equal to 1 mm, and then inspect, package, and store them in a warehouse.

[0083] Example 4:

[0084] 1. Preparation of microbial agent

[0085] The microbial agent is a composite microbial community composed of photosynthetic bacteria, nitrifying bacteria, and Bacillus subtilis. The composite microbial community embedding beads have a double-layer embedding structure. The inner core is Bacillus subtilis, and the outer layer is photosynthetic bacteria and nitrifying bacteria; the particle size of the composite microbial community is 2-8 mm, and the shape is spherical. Among them, the mass ratio of photosynthetic bacteria, Bacillus subtilis, and nitrifying bacteria is 1:0.2:0.2; the specific preparation method is as follows:

[0086] (a) After coagulation, drying, and sieving treatment of the Bacillus subtilis, the inner core of the composite microbial community embedding beads is prepared.

[0087] (b) After centrifugation and rinsing of the photosynthetic bacteria and nitrifying bacteria, add an embedding agent and stir evenly to obtain a bacteria-colloid mixture. Among them, the photosynthetic bacteria: nitrifying bacteria: embedding agent are mixed evenly according to a mass ratio of 1:0.2:2; in the embedding agent, the mass ratio of polyvinyl alcohol: sodium alginate: water is 5:0.1:50.

[0088] (c) Place the inner core of the composite microbial community embedding beads in a spherical hollow mold, inject the bacteria-colloid mixture, and at the same time inject a fixing agent and roll the spherical hollow mold for 1-2 hours, then inject the fixing agent again, and roll the spherical hollow mold for 6-12 hours. After taking out, the composite microbial community embedding beads are obtained through stirring, screening, and activation steps. Among them, the mass ratio of the embedding agent and the fixing agent in the spherical hollow mold is 1:1, and the fixing agent is a saturated boric acid + KCl solution; the activation is to culture the prepared composite microbial community embedding beads under the conditions of pH = 6, dissolved oxygen 2 mg / L, and water temperature 15°C for 1 day. The diameter of the inner core of the prepared composite microbial community embedding beads is 2 mm, the outer layer is 4 mm thick, the porosity is 20%, and the specific surface area is 10 m 2 / g.

[0089] 2. Preparation of flocculant

[0090] 1. The flocculant is a mixture of cyanobacteria metabolites and fermentation liquid, wherein the fermentation liquid components are corn straw, sweet potato stems and leaves, sawdust, cactus, houttuynia cordata, wormwood leaves, and yeast powder; the mass ratio of cyanobacteria metabolites to fermentation liquid is 1:1.

[0091] 2. The method for preparing cyanobacterial metabolites is to transfer the cyanobacteria to Zarrouk medium for cultivation, add diethylaminoacetaldehyde diethyl acetal enhancer, and the culture conditions are: growth temperature 25-27°C, pH 8-9, light intensity 3000lx, light-dark ratio of 12h:12h; the cyanobacteria cultured to the stable period are centrifuged at 4000-5000rpm for 20min, the algae are removed, and the supernatant is retained for later use.

[0092] 3. The preparation method of the fermentation liquid is as follows: weigh the following components in parts by mass: 25 parts of corn stalks, 25 parts of sweet potato stems and leaves, 15 parts of sawdust, 15 parts of cactus, 12 parts of Houttuynia cordata, 4 parts of wormwood, and 4 parts of yeast powder, crush or grind the weighed components and mix them evenly, add purified water of the same mass as the mixed components to the mixed components, put them into a glass container after mixing, seal the glass container, ferment in the dark at 100-120rpm and 20℃-25℃ for 24 hours, then ferment in the dark at 140-160rpm and 25℃-27℃ for 36-48 hours, and pass the fermentation product through a 100 sieve to obtain the fermentation liquid.

[0093] 3. A method for harmless treatment of aquaculture wastewater, comprising the following steps:

[0094] (1) The aquaculture wastewater is collected and flowed into a sewage collection tank equipped with a screen, and a microbial agent is added at one time, and then enters the sedimentation and filtration tank through a pipeline from the sewage collection tank;

[0095] (2) Continuously adding flocculants to the sewage, and at the same time, continuously aerating the sewage with air, the residence time of the sewage in the flocculation tank is 5 to 15 minutes, and the concentration of the flocculants added to the sewage is 20 mg / L;

[0096] (3) The aquaculture wastewater entering the sedimentation and filtration tank is left to stand for 1-2 hours, and then the upper clear water in the sedimentation and filtration tank is treated by membrane filtration and pumped into the aquaculture pond for aquaculture production; the sludge settled at the bottom of the sedimentation and filtration tank is pumped into the sludge drying equipment for dehydration, and then used as fertilizer water for seawater ponds or used as farmland fertilizer after desalination treatment.

[0097] Among them, the membrane is a microfiltration membrane or an ultrafiltration membrane; the method for making farmyard manure from sedimented sludge is as follows: a. Dry and crush the sedimented sludge at a temperature of 60°C; b. Remove the salts in the sludge: Add clear water with a weight 1 time that of the sludge to the crushed sludge, mix well, stir at a speed of 60 rpm for 20 minutes, filter the washed sludge by suction, dry it at a temperature of 50°C until the water content is 10%, and crush it; c. Dry the filter residue obtained in step (3) at a temperature of 50°C until the water content is 10%, and crush it; d. Mix the dried filter residue with the dried sludge obtained in step b in a ratio of 0.2:1 to obtain a dried mixture; e. Put the dried mixture into a granulator for granulation to obtain particles with a diameter less than or equal to 1 mm, and then inspect, package, and store in a warehouse.

[0098] Example 5:

[0099] 1. Preparation of microbial agent

[0100] The microbial agent is a composite microbial community composed of photosynthetic bacteria, nitrifying bacteria, and Bacillus subtilis. The composite microbial community embedding pellet material has a double-layer embedding structure. The inner core is Bacillus subtilis, and the outer layer is photosynthetic bacteria and nitrifying bacteria; the particle size of the composite microbial community is 2 - 8 mm, and the shape is spherical. Among them, the mass ratio of photosynthetic bacteria, Bacillus subtilis, and nitrifying bacteria is 1:3:3; the specific preparation method is as follows:

[0101] (a) After coagulation, drying, and sieving treatment of the Bacillus subtilis, the inner core of the composite microbial community embedding pellet is prepared.

[0102] (b) After centrifugation and rinsing of the photosynthetic bacteria and nitrifying bacteria, add an embedding agent and stir evenly to obtain a bacteria-colloid mixture. Among them, the photosynthetic bacteria: nitrifying bacteria: embedding agent are mixed evenly according to a mass ratio of 1:3:8; in the embedding agent, the mass ratio of polyvinyl alcohol: sodium alginate: water is 5:1:150.

[0103] (c) Place the inner core of the composite microbial community embedding pellet in a spherical hollow mold, inject the bacteria-colloid mixture, and at the same time inject a fixing agent and roll the spherical hollow mold for 1 - 2 hours, then inject the fixing agent again, and roll the spherical hollow mold for 6 - 12 hours. After taking out, through stirring, screening, and activation steps, the composite microbial community embedding pellet is obtained. Among them, the mass ratio of the embedding agent and the fixing agent in the spherical hollow mold is 1:7, and the fixing agent is a saturated boric acid + KCl solution; the activation is to culture the prepared composite microbial community embedding pellet under the conditions of pH = 9, dissolved oxygen 6 mg / L, and water temperature 35°C for 5 days. The diameter of the inner core of the prepared composite microbial community embedding pellet is 2 mm, the outer layer is 4 mm thick, the porosity is 80%, and the specific surface area is 35 m 2 / g.

[0104] 2. Preparation of flocculant

[0105] 1. The flocculant is a mixture of cyanobacteria metabolites and fermentation liquid, wherein the fermentation liquid components are corn straw, sweet potato stems and leaves, sawdust, cactus, houttuynia cordata, wormwood leaves, and yeast powder; the mass ratio of cyanobacteria metabolites to fermentation liquid is 1:6.

[0106] 2. The method for preparing cyanobacterial metabolites is to transfer the cyanobacteria to Zarrouk medium for cultivation, add diethylaminoacetaldehyde diethyl acetal enhancer, and the culture conditions are: growth temperature 25-27°C, pH 8-9, light intensity 3000lx, light-dark ratio of 12h:12h; the cyanobacteria cultured to the stable period are centrifuged at 4000-5000rpm for 20min, the algae are removed, and the supernatant is retained for later use.

[0107] 3. The preparation method of the fermentation liquid is as follows: weigh the following components in parts by mass: 25 parts of corn stalks, 25 parts of sweet potato stems and leaves, 15 parts of sawdust, 15 parts of cactus, 12 parts of Houttuynia cordata, 4 parts of wormwood, and 4 parts of yeast powder, crush or grind the weighed components and mix them evenly, add purified water of the same mass as the mixed components to the mixed components, put them into a glass container after mixing, seal the glass container, ferment in the dark at 100-120rpm and 20℃-25℃ for 24 hours, then ferment in the dark at 140-160rpm and 25℃-27℃ for 36-48 hours, and pass the fermentation product through a 100 sieve to obtain the fermentation liquid.

[0108] 3. A method for harmless treatment of aquaculture wastewater, comprising the following steps:

[0109] (1) The aquaculture wastewater is collected and flowed into a sewage collection tank equipped with a screen, and a microbial agent is added at one time, and then enters the sedimentation and filtration tank through a pipeline from the sewage collection tank;

[0110] (2) Continuously adding flocculants to the sewage, and at the same time, continuously aerating the sewage with air, the residence time of the sewage in the flocculation tank is 5 to 15 minutes, and the concentration of the flocculants added to the sewage is 80 mg / L;

[0111] (3) The aquaculture wastewater entering the sedimentation and filtration tank is left to stand for 1-2 hours, and then the upper clear water in the sedimentation and filtration tank is treated by membrane filtration and pumped into the aquaculture pond for aquaculture production; the sludge settled at the bottom of the sedimentation and filtration tank is pumped into the sludge drying equipment for dehydration, and then used as fertilizer water for seawater ponds or used as farmland fertilizer after desalination treatment.

[0112] The membrane is a microfiltration membrane or an ultrafiltration membrane; the method for preparing farmland fertilizer from sedimented sludge is as follows: a. drying the sedimented sludge at 100°C and crushing it; b. removing salt from the sludge: adding clean water 8 times the weight of the sludge to the crushed sludge, mixing it evenly, stirring it at a speed of 100 rpm for 20 minutes, filtering the washed sludge, drying it at 90°C to a water content of 25%, and crushing it; c. drying the filter residue obtained in step (3) at 90°C to a water content of 25%, and crushing it; d. mixing the dried filter residue with the dried sludge obtained in step b at a ratio of 3:1 to obtain a dried mixture; e. placing the dried mixture into a granulator for granulation to obtain particles with a diameter less than or equal to 1 mm, inspecting, packaging, and storing them.

[0113] Embodiment 6:

[0114] 1. Preparation of microbial preparations

[0115] The microbial preparation is a composite bacterial community composed of nitrifying bacteria and Bacillus subtilis. The composite bacterial community embedded pellet material has a double-layer embedding structure, with the inner core being Bacillus subtilis and the outer layer being nitrifying bacteria. The composite bacterial community particle size is 2 to 8 mm and the shape is spherical, wherein the mass ratio of Bacillus subtilis to nitrifying bacteria is 1:1. The specific preparation method is as follows:

[0116] (a) subjecting the Bacillus subtilis to coagulation, drying and sieving to obtain a composite bacterial flora-embedded pellet core;

[0117] (b) After centrifuging and washing the nitrifying bacteria, an embedding agent is added and stirred evenly to obtain a bacteria-gel mixed solution, wherein the nitrifying bacteria and the embedding agent are evenly mixed in a mass ratio of 1:3; the mass ratio of polyvinyl alcohol: sodium alginate: water in the embedding agent is 5:0.2:100.

[0118] (c) placing the inner core of the composite flora-embedded pellet in a spherical hollow mold, injecting the bacteria-gel mixture, injecting a fixative, and rolling the spherical hollow mold for 1 to 2 hours, then injecting a fixative again, and rolling the spherical hollow mold for 6 to 12 hours. After taking out, the composite flora-embedded pellet is obtained through stirring, screening, and activation steps.

[0119] 2. A method for harmless treatment of aquaculture wastewater, comprising the following steps:

[0120] (1) The aquaculture wastewater is collected and flowed into a sewage collection tank equipped with a screen, and a microbial agent is added at one time, and then enters the sedimentation and filtration tank through a pipeline from the sewage collection tank;

[0121] (2) Chitosan is continuously added to the sewage, the residence time of the sewage in the flocculation tank is 5 to 15 minutes, and the concentration of the flocculant added to the sewage is 50 mg / L;

[0122] (3) Let the aquaculture sewage entering the sedimentation and filtration tank stand still for 1 - 2 hours, and then the upper clear water in the sedimentation and filtration tank is pumped into the aquaculture pond for aquaculture production after membrane filtration treatment; the sludge settled at the bottom of the sedimentation and filtration tank enters the sludge drying equipment through a sludge pump for dehydration, and is used for fertilizing seawater ponds or used as farmland fertilizer after desalination treatment.

[0123] Example 7:

[0124] 1. Measure the COD, BOD, suspended solids, transparency value, pH value, NH 4 -N, NO 2 -N in the sewage when it is discharged into the sewage collection tank respectively, and measure the COD, BOD, suspended solids, transparency value, pH value, NH 4 -N, NO 2 -N in the seawater after being treated by the harmless treatment method of the embodiments of the present invention respectively, and calculate the removal rates of COD, BOD, and suspended solids. The experimental results are shown in Tables 1 - 3:

[0125] Table 1 Removal rates of aquaculture pollution by the comprehensive treatment method of the embodiments

[0126] COD removal rate, % BOD removal rate, % Suspended solid SS removal rate, % Example 1 93.5 94.8 98.3 Example 2 90.2 93.1 95.8 Example 3 89.8 91.5 96.2 Example 4 80.6 82.3 84.7 Example 5 81.4 81.8 83.9 Example 6 75.2 70.9 75.1

[0127] Table 2 Water quality conditions of the sewage collection tank of the embodiments before treatment

[0128] Transparency pH <![CDATA[NH 4 -N]]> <![CDATA[NO 2 -N]]> Example 1 21 6.5 0.41 0.22 Example 2 21 6.7 0.40 0.23 Example 3 20 6.6 0.42 0.23 Example 4 20 6.7 0.41 0.22 Example 5 21 6.7 0.41 0.22 Example 6 20 6.5 0.42 0.21

[0129] Table 3 Water quality conditions of the seawater samples in the sedimentation and filtration tank after treatment

[0130] Transparency pH <![CDATA[NH 4 -N]]> <![CDATA[NO 2 -N]]> Example 1 52 8.9 0.07 0.01 Example 2 50 8.6 0.09 0.03 Example 3 49 8.7 0.10 0.02 Example 4 38 7.2 0.27 0.12 Example 5 37 7.3 0.25 0.13 Example 6 32 6.9 0.37 0.18

[0131] In summary, the experimental results show that the present invention can effectively degrade aquaculture pollution, has low cost, and can reasonably utilize aquaculture sewage. The removal rate of suspended solids SS reaches 95.8 - 98.3%, the removal rate of chemical oxygen demand COD is 89.8 - 93.5%, and the removal rate of BOD is 91.5 - 94.8%. The water quality conditions after treatment have been greatly improved.

[0132] The above is a description of the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above - mentioned embodiments, and what is described in the above - mentioned embodiments and the specification is only to illustrate the principle of the present invention.

[0133] Without departing from the concept of the present invention, those skilled in the art will also have various non - substantial changes and improvements, and these all fall within the scope of protection required by the present invention.

Claims

1. A method for harmless treatment of aquaculture wastewater, comprising the following steps: (1) The aquaculture wastewater is collected and flowed into a sewage collection tank equipped with a screen, and a microbial agent is added at one time, and then enters the sedimentation and filtration tank through a pipeline from the sewage collection tank; (2) Continuously adding flocculants to the sewage, and at the same time, continuously aerating the sewage with air, the residence time of the sewage in the flocculation tank is 5 to 15 minutes; (3) The aquaculture wastewater entering the sedimentation and filtration tank is left to stand for 1-2 hours, and then the upper clear water in the sedimentation and filtration tank is treated by membrane filtration and pumped into the aquaculture pond for aquaculture production; the sludge settled at the bottom of the sedimentation and filtration tank is pumped into the sludge drying equipment for dehydration, and then used as fertilizer water for seawater ponds or used as farmland fertilizer after desalination treatment.

2. The method according to claim 1, characterized in that In the above step (1), the microbial preparation is a composite bacterial community, which is composed of photosynthetic bacteria, nitrifying bacteria and Bacillus subtilis; the composite bacterial community encapsulation ball material has a double-layer encapsulation structure, with the inner core being Bacillus subtilis and the outer layer being photosynthetic bacteria and nitrifying bacteria; the composite bacterial community particle size is 2 to 8 mm and the shape is spherical.

3. The method according to claim 2, characterized in that The specific preparation steps of the composite flora embedded beads are as follows: (a) subjecting the Bacillus subtilis to coagulation, drying and sieving to obtain a composite bacterial flora-embedded pellet core; (b) After centrifugation and washing, the photosynthetic bacteria and nitrifying bacteria are added with an embedding agent and stirred evenly to obtain a bacteria-gel mixed solution, wherein the photosynthetic bacteria: nitrifying bacteria: embedding agent are mixed evenly in a mass ratio of 1:0.5-2.0:3-7; the mass ratio of polyvinyl alcohol: sodium alginate: water in the embedding agent is 5:0.2-0.7:70-120; (c) placing the inner core of the composite flora embedded sphere in a spherical hollow mold, injecting the bacteria-glue mixture, injecting the fixative at the same time and rolling the spherical hollow mold for 1 to 2 hours, then injecting the fixative again, and rolling the spherical hollow mold for 6 to 12 hours, taking it out and performing stirring, screening and activation steps to obtain the composite flora embedded sphere, wherein the mass ratio of the embedding agent to the fixative in the spherical hollow mold is 1:2 to 5, and the fixative is a saturated boric acid + KCl solution; the activation is to culture the prepared composite flora embedded sphere under the conditions of pH = 7 to 8, dissolved oxygen 3 to 5 mg / L, and water temperature 20 to 30°C for 1 to 3 days.

4. The method according to claim 3, characterized in that The composite bacterial colony embedded sphere has an inner core diameter of 1 to 4 mm, an outer layer thickness of 1 to 4 mm, a porosity of 30% to 70%, and a specific surface area of ​​15 to 30 m 2 / g.

5. The method according to claim 1, characterized in that In the step (2), the flocculant is a mixture of cyanobacteria metabolites and fermentation liquid, wherein the fermentation liquid components are corn stalks, sweet potato stems and leaves, sawdust, cactus, houttuynia cordata, wormwood leaves, and yeast powder.

6. The method according to claim 1, characterized in that The mass ratio of the flocculant cyanobacteria metabolite to the fermentation broth is 1:2-5; preferably, the mass ratio of the cyanobacteria metabolite to the fermentation broth is 1:

3.

7. The method according to claim 1, characterized in that The method for preparing the cyanobacteria metabolite comprises the following steps: transferring the cyanobacteria to a Zarrouk medium for culture, adding a diethylaminoacetaldehyde diethyl acetal enhancer, and the culture conditions are: a growth temperature of 25 to 27°C, a pH value of 8 to 9, a light intensity of 3000 lx, and a light-dark ratio of 12h:12h; centrifuging the cyanobacteria cultured to a stable period at 4000 to 5000 rpm for 20 minutes, removing the algae, and retaining the supernatant for later use.

8. The method according to claim 1, characterized in that The preparation method of the fermentation liquid comprises the following steps: weighing the following components in parts by mass: 25 parts of corn stalks, 25 parts of sweet potato stems and leaves, 15 parts of sawdust, 15 parts of cactus, 12 parts of houttuynia cordata, 4 parts of wormwood leaves, and 4 parts of yeast powder; crushing or grinding the weighed components and mixing them evenly; adding purified water of the same mass as the mixed components to the mixed components; mixing the components evenly and putting the components into a glass container; sealing the glass container; fermenting the components in the dark at 100-120 rpm and 20-25° C. for 24 hours; and then fermenting the components in the dark at 140-160 rpm and 25-27° C. for 36-48 hours; and passing the fermentation product through a 100-sieve to obtain the fermentation liquid.

9. The method according to claim 1, characterized in that: The concentration of the flocculant added to the sewage is 30~ 70mg / L, preferably 50mg / L.

10. The method according to claim 5, characterized in that The method for preparing farmland fertilizer from the precipitated sludge in step (3) comprises: (a) drying the precipitated sludge at a temperature of 70 to 90° C. and crushing it; (b) removing salt from the sludge: adding clean water 2 to 7 times the weight of the sludge to the crushed sludge, mixing it evenly, stirring it at a speed of 70 to 90 rpm for 20 minutes, filtering the washed sludge, drying it at a temperature of 60 to 80° C. to a water content of 15 to 20%, and crushing it; (c) drying the filter residue obtained in step (3) at a temperature of 60 to 80° C. to a water content of 15 to 20%, and crushing it; (d) mixing the dried filter residue with the dried sludge obtained in step b at a ratio of 0.5 to 2:1 to obtain a dried mixture; (e) placing the dried mixture into a granulator for granulation to obtain particles with a diameter less than or equal to 1 mm, inspecting, packaging, and storing them.