CN118063000A - A method for repairing aquaculture tail water using photosynthetic bacteria - Google Patents

Abstract

The invention relates to the technical field of aquaculture tail water treatment, in particular to a method for repairing aquaculture tail water by utilizing photosynthetic bacteria. A method for restoring aquaculture tail water using photosynthetic bacteria, comprising: inoculating microalgae-microorganism symbiota onto an immobilized nanoparticle carrier; introducing the aquaculture tail water into a bioreactor, and domesticating for a long time; planting aquatic plants in a bioreactor, and inoculating activated sludge into the bioreactor; and (3) operating the bioreactor, detecting the water quality parameter of the water outlet, and adjusting the parameter of the bioreactor. According to the invention, by constructing a high-efficiency and good-compatibility tail water restoration system, the immobilized carrier particles are used for immobilizing microalgae-microorganism symbionts, so that the concentration and stability of microorganisms are improved, and the comprehensive and high-efficiency removal of pollutants such as ammonia nitrogen, organic matters and the like in the aquaculture tail water is realized by combining the absorption and degradation actions of the algae-microorganism symbionts and aquatic plants and the microorganism metabolic activities of activated sludge.

Description

A method for repairing aquaculture tail water using photosynthetic bacteria

Technical Field

The invention relates to the technical field of aquaculture water treatment, and in particular to a method for repairing aquaculture tail water by utilizing photosynthetic bacteria.

Background technique

Aquaculture tailwater contains high concentrations of pollutants such as ammonia nitrogen, nitrite, organic matter and suspended solids, which need to be purified before discharge and recycled back to the breeding area or other uses. Due to the difficulty of treating aquaculture tailwater and the development of aquaculture water treatment technology, a combination of multiple technologies has become a major trend. The current multi-technical combination usually uses several processes such as traditional activated sludge, anaerobic-anoxic-aerobic and sequencing batch activated sludge, and is mostly treated in the order of "physical method + biological method + physicochemical method".

However, although these combined methods can remove some pollutants, the overall treatment efficiency is still limited. For example, traditional activated sludge has poor removal effect on ammonia nitrogen and nitrite. In addition, the compatibility between different treatment technologies is also poor, which ultimately leads to low remediation efficiency of aquaculture tail water. Therefore, the present invention provides a method for remediating aquaculture tail water using photosynthetic bacteria to solve the above problems.

Summary of the invention

In view of the shortcomings of the prior art, the object of the present invention is to provide a method for repairing aquaculture tail water using photosynthetic bacteria.

A method for repairing aquaculture tail water using photosynthetic bacteria, comprising the following steps:

(1) inoculating the pre-cultured microalgae-microorganism symbiont onto the immobilized nanoparticle carrier, and evenly distributing the symbiont on the carrier to obtain a mixture;

(2) introducing the mixture into the bioreactor, turning on the aeration device to provide sufficient oxygen for the symbionts, and introducing the pretreated aquaculture tail water into the bioreactor for long-term domestication;

(3) Planting aquatic plants in a bioreactor with their roots distributed near the immobilized nanoparticle carriers and inoculating activated sludge into the bioreactor;

(4) During the operation of the bioreactor, the water quality parameters at the outlet are regularly tested to evaluate the tailwater treatment effect and the parameters of the bioreactor are adjusted according to the test results.

Furthermore, the method for culturing the microalgae-microorganism symbiont is as follows: selecting species of microalgae, microorganisms and photosynthetic bacteria, simulating the environment of actual aquaculture tail water, optimizing the culture conditions of microalgae and microorganisms, adding the screened microalgae, microbial inoculants and photosynthetic bacterial inoculants into a culture system containing simulated aquaculture tail water, and culturing them together until the cell density reaches an appropriate level, thereby obtaining a microalgae-microorganism symbiont.

Furthermore, the microalgae are Chlorella or diatoms; the microorganisms are nitrifying bacteria and denitrifying bacteria; and the photosynthetic bacteria are Rhodopseudomonas.

Furthermore, the conditions of the culture method are: light intensity of 2000-10000 lux, light time of 12-14 hours per day, temperature of 20-30°C, pH of 6.5-8.5, and aeration volume to maintain sufficient oxygen supply demand of the culture system.

Furthermore, the mixing mass ratio of the microalgae to the total bacterial agent is 15:1-2.5, and the bacterial count ratio of nitrifying bacteria, denitrifying bacteria and photosynthetic bacteria in the total bacterial agent is 4-6:4-6:1-2.

Furthermore, the immobilized nanoparticle carrier is obtained by fixing the surface-modified nanoparticles on a carrier material by physical adsorption, chemical bonding or embedding.

Furthermore, the carrier material is one or more of activated carbon, diatomaceous earth, high molecular polymer and ceramic material; the nanoparticles are nano titanium dioxide, nano zinc oxide or nano iron.

Furthermore, the bioreactor is an oxidation pond, an artificial wetland or a sequencing batch reactor.

Furthermore, the method of inoculating the microalgae-microorganism symbiont into the immobilized nanoparticle carrier is stirring, soaking or dripping.

Furthermore, the aquatic plants are one or more of reed, water hyacinth, canna and water plantain; the activated sludge is one or more of aerobic activated sludge, anaerobic activated sludge, anoxic activated sludge and biofilm activated sludge.

The beneficial effects achieved by the present invention are as follows: 1. The present invention constructs an efficient tailwater remediation system with good compatibility, uses immobilized carrier particles to fix microalgae-microorganism symbionts, is beneficial to the attachment and growth of microorganisms and algae, improves the concentration and stability of microorganisms, combines the absorption and degradation effects of algae-microorganism-photosynthetic bacteria symbionts and aquatic plants, and the microbial metabolic activities of the activated sludge method, and can achieve comprehensive and efficient removal of pollutants such as ammonia nitrogen, nitrite, organic matter and suspended solids in aquaculture tailwater.

2. The microalgae-microorganism symbiosis, aquatic plants and activated sludge of the present invention can work synergistically to form an artificial wetland. The microorganisms in the activated sludge are responsible for degrading organic pollutants and ammonia nitrogen, etc., the aquatic plants absorb nutrients and provide oxygen through their roots, and the microalgae-microorganism symbiosis can further utilize light energy and carbon dioxide for photosynthesis, while producing oxygen for other organisms to use, thereby improving the efficiency of sewage treatment and the ecological benefits.

3. The microalgae, microorganisms and photosynthetic bacteria on the immobilized carrier particles of the present invention can work together. The microorganisms and microalgae on the immobilized carrier particles can work synergistically to convert nitrogen and phosphorus into harmless or low-toxic substances. At the same time, the nanoparticles can promote the photosynthesis of algae, thereby alleviating the eutrophication problem of water bodies.

4. The present invention uses carrier materials to immobilize nanoparticles, which can reduce the toxicity of the nanoparticles and improve the stability and biocompatibility of the nanoparticles.

5. The aquatic plant roots of the present invention can adsorb and enrich nanoparticles, reduce the release of nanoparticles during operation, and facilitate subsequent recycling and reuse.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic flow diagram of a method for repairing aquaculture tail water using photosynthetic bacteria according to an embodiment of the present invention;

FIG. 2 is a graph showing the comparison of the treatment effects of aquaculture tail water used in the embodiments of the present invention and the comparative examples.

Detailed ways

The present invention is further described in detail below with reference to specific embodiments.

In the following Examples 1 to 3, in the step of culturing the microalgae-microorganism symbiont, the environment of actual aquaculture tail water is simulated, and microalgae, microbial agents and photosynthetic bacterial agents are added to a culture system containing simulated aquaculture tail water for co-cultivation until the cell density reaches an appropriate level to obtain the microalgae-microorganism symbiont. The specific scheme is:

In order to simulate the actual environment of aquaculture tail water, BG-11 culture medium was selected, which contains the following components:

Carbon source: 0.2 g/L glucose. Depending on the growth of the symbiont, 0.2 g/L of glucose was added every 24-48 hours until the optimal growth effect was achieved or no obvious growth promotion effect was observed;

Nitrogen and phosphorus sources: 1 mM sodium nitrate and 0.2 mM disodium hydrogen phosphate;

Trace elements: iron, zinc, copper and manganese, with the concentration range of each element being 0.05 mg/L;

Vitamins: Vitamin B12, biotin and thiamine, with concentrations of each vitamin ranging from 0.005 mg/L;

Buffer: Sodium bicarbonate or phosphate buffer to maintain the pH of the medium at 7.0 ± 0.5.

Co-culture conditions of microalgae, microbial agents and photosynthetic bacteria:

Microalgae, microorganisms and photosynthetic bacteria were inoculated into the culture medium in a predetermined ratio, with a total inoculation volume of 3% of the culture medium volume; the light intensity was 5000 lux, the lighting time was 13 h per day, the temperature was 25°C, the pH of the culture medium was 7.0±0.5, and the aeration volume was adjusted according to the dissolved oxygen level of the culture system to ensure that the symbionts obtained sufficient oxygen. The culture time was determined according to the growth rate of the symbionts and the tailwater remediation effect, and was set to 10 days.

Specific steps for microalgae-microorganism cultivation:

Medium preparation: Prepare the medium according to the above ingredients and concentrations, and adjust the pH to 7.0 ± 0.5;

Autoclave: Autoclave the prepared culture medium at 121°C for 20 minutes to eliminate potential microbial contamination. After cooling, it can be used to culture the symbionts.

Inoculation: Under sterile conditions, the pre-cultured symbionts are inoculated into the sterilized culture medium according to a predetermined ratio;

Cultivation: Cultivate the symbiont under controlled conditions of light, temperature and aeration;

Monitoring: Regularly monitor the pH value, dissolved oxygen level, biomass of the culture medium and water quality indicators of the tail water;

Harvest: Harvest is carried out when the symbiont growth reaches a stable period or the tailwater remediation effect reaches the expected level.

Example 1: A method for repairing aquaculture tail water using photosynthetic bacteria, as shown in Figure 1, a method for repairing aquaculture tail water using photosynthetic bacteria, comprising the following steps:

(1) Cultivation of microalgae-microorganism symbiosis

Chlorella, nitrifying bacteria, denitrifying bacteria and Rhodopseudomonas are selected to simulate the environment of actual aquaculture tail water, and the microalgae, microbial inoculants and photosynthetic bacterial inoculants are added to a culture medium containing the simulated aquaculture tail water for co-cultivation until the cell density reaches an appropriate level, thereby obtaining a microalgae-microorganism symbiont;

The mixing mass ratio of microalgae to total bacterial agent is 15:1, and the bacterial number ratio of nitrifying bacteria, denitrifying bacteria and photosynthetic bacteria in the total bacterial agent is 4:4:1;

(2) Preparation of immobilized nanoparticle carriers

Chitosan was selected as the carrier material and nano-titanium dioxide was selected as the nanoparticles. Chitosan was dissolved, the pH of the solution was controlled to be 5, nano-titanium dioxide was added, and the solution was fully adsorbed for 5 hours to fix the nano-titanium dioxide on the chitosan by an embedding method. After vacuum drying, the immobilized nano-particle carrier was obtained. The mass ratio of chitosan to nano-titanium dioxide was 1:1.

(3) Inoculation of microalgae-microorganism symbionts onto immobilized nanoparticle carriers

The immobilized nanoparticle carrier was immersed in sterile water for 2 h; Chlorella cells were collected during the exponential growth phase, washed twice by centrifugation (3000 rpm, 5 minutes), and resuspended in fresh culture medium; bacterial cells were collected during the exponential growth phase, washed twice by centrifugation (4000 rpm, 10 minutes), and resuspended in a buffer containing appropriate nutrients; Rhodopseudomonas cells were collected during the exponential growth phase, washed twice by centrifugation (4000 rpm, 10 minutes), and resuspended in a liquid culture medium containing appropriate carbon and nitrogen sources;

Add the pretreated immobilized nanoparticle carrier into a sterile container; stir the symbiotic cell suspension and the carrier together for 30 minutes, with the mass volume ratio of the immobilized nanoparticle carrier to the symbiotic cell suspension being 8 mg:1 L, to ensure that the symbionts are evenly distributed on the carrier, to obtain a mixture; transfer the inoculated carrier to a light incubator or a shake flask, and continue to culture the symbiont under suitable conditions;

(4) Introducing the mixture into the bioreactor

Select oxidation pond as bioreactor, introduce the mixture and evenly distribute it in the bioreactor, with a filling rate of 40% (the ratio of carrier volume to the total volume of the reactor), turn on the aeration device to ensure sufficient and even oxygen supply, and adjust the aeration volume to a suitable level to meet the respiratory needs of the symbionts, while avoiding damage to the cells caused by excessive aeration;

Collect and pre-treat aquaculture tailwater to remove large particles and suspended solids, introduce the pre-treated tailwater into the bioreactor, pay attention to controlling the influent flow and load, and start the long-term domestication process of the symbiont;

(5) Planting aquatic plants and inoculating activated sludge

Spread soil or fine sand near the immobilized nanoparticle carrier, plant the roots of reed and canna near the immobilized nanoparticle carrier, and reasonably arrange the planting positions of reed and canna in the bioreactor, with a planting density of 10 plants per square meter to ensure sufficient sunlight and air circulation;

The combination of anaerobic activated sludge and aerobic activated sludge is evenly added to the bioreactor to ensure full contact between the sludge and the wastewater. The sludge concentrations are 3g/L and 4g/L respectively, and the amount added is 1/3 of the effective volume of the bioreactor. The activated sludge is tamed by gradually increasing the tail water concentration and load until a stable treatment effect is achieved.

(6) Operation of bioreactor

Build the above efficient and compatible tailwater remediation system. During the operation of the bioreactor, regularly test the water quality parameters at the outlet to evaluate the treatment effect of aquaculture tailwater and adjust the parameters of the bioreactor according to the test results.

Example 2: A method for repairing aquaculture tail water using photosynthetic bacteria, as shown in Figure 1, a method for repairing aquaculture tail water using photosynthetic bacteria, comprising the following steps:

(1) Cultivation of microalgae-microorganism symbiosis

Chlorella, nitrifying bacteria, denitrifying bacteria and Rhodopseudomonas are selected to simulate the environment of actual aquaculture tail water, and the microalgae, microbial inoculants and photosynthetic bacterial inoculants are added to a culture medium containing the simulated aquaculture tail water for co-cultivation until the cell density reaches an appropriate level, thereby obtaining a microalgae-microorganism symbiont;

The mixing mass ratio of microalgae to total bacterial agent is 15:2, and the bacterial count ratio of nitrifying bacteria, denitrifying bacteria and photosynthetic bacteria in the total bacterial agent is 5:5:1.5;

(2) Preparation of immobilized nanoparticle carriers

Chitosan was selected as the carrier material and nano-titanium dioxide was selected as the nanoparticles. Chitosan was dissolved, the pH of the solution was controlled to be 5, nano-titanium dioxide was added, and the solution was fully adsorbed for 5 hours to fix the nano-titanium dioxide on the chitosan by an embedding method. After vacuum drying, the immobilized nano-particle carrier was obtained. The mass ratio of chitosan to nano-titanium dioxide was 1:1.

(3) Inoculation of microalgae-microorganism symbionts onto immobilized nanoparticle carriers

The immobilized nanoparticle carrier was immersed in sterile water for 2 h; Chlorella cells were collected during the exponential growth phase, washed twice by centrifugation (3000 rpm, 5 minutes), and resuspended in fresh culture medium; bacterial cells were collected during the exponential growth phase, washed twice by centrifugation (4000 rpm, 10 minutes), and resuspended in a buffer containing appropriate nutrients; Rhodopseudomonas cells were collected during the exponential growth phase, washed twice by centrifugation (4000 rpm, 10 minutes), and resuspended in a liquid culture medium containing appropriate carbon and nitrogen sources;

Add the pretreated immobilized nanoparticle carrier into a sterile container; stir the symbiotic cell suspension and the carrier together for 30 minutes, with the mass volume ratio of the immobilized nanoparticle carrier to the symbiotic cell suspension being 10 mg:1 L, to ensure that the symbionts are evenly distributed on the carrier, to obtain a mixture; transfer the inoculated carrier to a light incubator or a shake flask, and continue to culture the symbiont under suitable conditions;

(4) Introducing the mixture into the bioreactor

Select oxidation pond as bioreactor, introduce the mixture and evenly distribute it in the bioreactor, with a filling rate of 40% (the ratio of carrier volume to the total volume of the reactor), turn on the aeration device to ensure sufficient and even oxygen supply, and adjust the aeration volume to a suitable level to meet the respiratory needs of the symbionts, while avoiding damage to the cells caused by excessive aeration;

Collect and pre-treat aquaculture tailwater to remove large particles and suspended solids, introduce the pre-treated tailwater into the bioreactor, pay attention to controlling the influent flow and load, and start the long-term domestication process of the symbiont;

(5) Planting aquatic plants and inoculating activated sludge

Spread soil or fine sand near the immobilized nanoparticle carrier, plant the roots of reed and canna near the immobilized nanoparticle carrier, and reasonably arrange the planting positions of reed and canna in the bioreactor, with a planting density of 10 plants per square meter to ensure sufficient sunlight and air circulation;

The combination of anaerobic activated sludge and aerobic activated sludge is evenly added to the bioreactor to ensure full contact between the sludge and the wastewater. The sludge concentrations are 3g/L and 4g/L respectively, and the amount added is 1/3 of the effective volume of the bioreactor. The activated sludge is tamed by gradually increasing the tail water concentration and load until a stable treatment effect is achieved.

(6) Operation of bioreactor

Build the above efficient and compatible tailwater remediation system. During the operation of the bioreactor, regularly test the water quality parameters at the outlet to evaluate the treatment effect of aquaculture tailwater and adjust the parameters of the bioreactor according to the test results.

Example 3: A method for repairing aquaculture tail water using photosynthetic bacteria, as shown in Figure 1, a method for repairing aquaculture tail water using photosynthetic bacteria, comprising the following steps:

(1) Cultivation of microalgae-microorganism symbiosis

Chlorella, nitrifying bacteria, denitrifying bacteria and Rhodopseudomonas are selected to simulate the environment of actual aquaculture tail water, and the microalgae, microbial inoculants and photosynthetic bacterial inoculants are added to a culture medium containing the simulated aquaculture tail water for co-cultivation until the cell density reaches an appropriate level, thereby obtaining a microalgae-microorganism symbiont;

The mixing mass ratio of microalgae to total bacterial agent is 15:1, and the bacterial number ratio of nitrifying bacteria, denitrifying bacteria and photosynthetic bacteria in the total bacterial agent is 4:4:1;

(2) Preparation of immobilized nanoparticle carriers

Polyurethane is selected as a carrier material and nano zinc dioxide is selected as nanoparticles. Polyurethane is dissolved and nano zinc dioxide is dispersed. The two solutions are mixed and ultrasonically dispersed to fix the nano zinc dioxide on the polyurethane through a solution mixing method. After vacuum drying, an immobilized nanoparticle carrier is obtained. The mass ratio of polyurethane to nano zinc dioxide is 1:1.

(3) Inoculation of microalgae-microorganism symbionts onto immobilized nanoparticle carriers

The immobilized nanoparticle carrier was immersed in sterile water for 2 h; Chlorella cells were collected during the exponential growth phase, washed twice by centrifugation (3000 rpm, 5 minutes), and resuspended in fresh culture medium; bacterial cells were collected during the exponential growth phase, washed twice by centrifugation (4000 rpm, 10 minutes), and resuspended in a buffer containing appropriate nutrients; Rhodopseudomonas cells were collected during the exponential growth phase, washed twice by centrifugation (4000 rpm, 10 minutes), and resuspended in a liquid culture medium containing appropriate carbon and nitrogen sources;

Add the pretreated immobilized nanoparticle carrier into a sterile container; stir the symbiotic cell suspension and the carrier together for 30 minutes, with the mass volume ratio of the immobilized nanoparticle carrier to the symbiotic cell suspension being 8 mg:1 L, to ensure that the symbionts are evenly distributed on the carrier, to obtain a mixture; transfer the inoculated carrier to a light incubator or a shake flask, and continue to culture the symbiont under suitable conditions;

(4) Introducing the mixture into the bioreactor

Select oxidation pond as bioreactor, introduce the mixture and evenly distribute it in the bioreactor, with a filling rate of 40% (the ratio of carrier volume to the total volume of the reactor), turn on the aeration device to ensure sufficient and even oxygen supply, and adjust the aeration volume to a suitable level to meet the respiratory needs of the symbionts, while avoiding damage to the cells caused by excessive aeration;

Collect and pre-treat aquaculture tailwater to remove large particles and suspended solids, introduce the pre-treated tailwater into the bioreactor, pay attention to controlling the influent flow and load, and start the long-term domestication process of the symbiont;

(5) Planting aquatic plants and inoculating activated sludge

Soil or fine sand is laid near the immobilized nanoparticle carrier, and the roots of water hyacinth and water plantain are planted near the immobilized nanoparticle carrier. The planting positions of water hyacinth and water plantain are reasonably arranged in the bioreactor, with a planting density of 10 plants per square meter to ensure sufficient sunlight and air circulation;

The combination of anoxic activated sludge and aerobic activated sludge is evenly added to the bioreactor to ensure full contact between the sludge and the wastewater. The sludge concentrations are 3g/L and 4g/L respectively, and the amount added is 1/3 of the effective volume of the bioreactor. The activated sludge is tamed by gradually increasing the tail water concentration and load until a stable treatment effect is achieved.

(6) Operation of bioreactor

Build the above efficient and compatible tailwater remediation system. During the operation of the bioreactor, regularly test the water quality parameters at the outlet to evaluate the treatment effect of aquaculture tailwater and adjust the parameters of the bioreactor according to the test results.

Comparative Example 1: Compared with Example 1, this comparative example adopts a traditional tail water treatment method, and the specific method is:

Aquaculture tail water was collected and treated in a sedimentation tank for 2 hours; the tail water after sedimentation treatment entered a sand filter with a filtration rate of 5m³/h; lime was added to the tail water at a dosage of 100mg/L, and sludge was treated regularly; the tail water entered an aeration tank with an aeration volume of 10m³/min and a dissolved oxygen concentration of 6mg/L; and the COD removal rate, nitrogen removal rate and phosphorus removal rate were measured on the 8th day of treating the aquaculture tail water.

Comparative Example 2: Compared with Example 1, this comparative example only uses sedimentation, chemical treatment and activated sludge treatment, and the specific method is:

Aquaculture tail water was collected and treated in a sedimentation tank for 2 hours; lime was added to the tail water at a dosage of 100 mg/L; the tail water was treated by activated sludge method at a sludge concentration of 3 g/L; and the COD removal rate, nitrogen removal rate and phosphorus removal rate were measured on the 8th day after the treatment of the aquaculture tail water.

Comparative Example 3: Compared with Example 1, no aquatic plants were planted in this comparative example, and the others were consistent with Example 1; and the COD removal rate, nitrogen removal rate and phosphorus removal rate were measured on the 8th day of treating aquaculture tail water.

As can be seen from Figure 2, the COD removal rate, nitrogen removal rate and phosphorus removal rate of the aquaculture tail water after treatment in Example 1 are higher than those in Comparative Examples 1-3, that is, the bioreactor tail water remediation system constructed by the present invention, combined with the inoculation of microalgae-microorganism symbionts with immobilized nanocarriers, the planting of aquatic plants, and the introduction of activated sludge, has a better treatment effect on aquaculture tail water.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims (10)

1. A method for restoring aquaculture tail water by photosynthetic bacteria, which is characterized by comprising the following steps:

(1) Inoculating the pre-cultured microalgae-microorganism symbiota onto an immobilized nanoparticle carrier, and uniformly distributing the symbiota on the carrier to obtain a mixture;

(2) Introducing the mixture into a bioreactor, starting an aeration device to provide sufficient oxygen for symbionts, introducing pretreated aquaculture tail water into the bioreactor, and carrying out long-term domestication;

(3) Planting aquatic plants in a bioreactor, distributing root systems of the aquatic plants near the immobilized nanoparticle carriers, and inoculating activated sludge into the bioreactor;

(4) In the running process of the bioreactor, periodically detecting the water quality parameter of the water outlet so as to evaluate the tail water treatment effect and adjusting the parameter of the bioreactor according to the detection result.

2. The method for restoring aquaculture tail water by photosynthetic bacteria according to claim 1, wherein said culturing method of microalgae-microorganism symbiota comprises: selecting microalgae, microorganisms and photosynthetic bacteria, simulating the environment of the actual aquaculture tail water, optimizing the culture conditions of the microalgae and the microorganisms, adding the screened microalgae, microbial agents and photosynthetic bacteria agents into a culture system containing the simulated aquaculture tail water for co-culture until the cell density reaches a proper level, and obtaining the microalgae-microorganism symbiont.

3. The method for restoring aquaculture tail water by photosynthetic bacteria of claim 2 wherein the microalgae is chlorella or diatom; the microorganism is nitrifying bacteria and denitrifying bacteria; the photosynthetic bacteria are rhodopseudomonas.

4. A method for restoring aquaculture tail water with photosynthetic bacteria according to claim 2 wherein the culturing method is under the following conditions: the illumination intensity is 2000-10000 lux, the illumination time is 12-14h per day, the temperature is 20-30 ℃, the pH is 6.5-8.5, and the aeration quantity can keep the sufficient oxygen supply requirement of the culture system.

5. The method for restoring aquaculture tail water by photosynthetic bacteria according to claim 2, wherein the mixing mass ratio of microalgae to total bacteria is 15:1-2.5, wherein the bacterial count ratio of nitrifying bacteria, denitrifying bacteria and photosynthetic bacteria in the total bacterial agent is 4-6:4-6:1-2.

6. The method for restoring aquaculture tail water by photosynthetic bacteria according to claim 1 wherein the immobilized nanoparticle carrier is obtained by immobilizing surface-modified nanoparticles onto a carrier material by physical adsorption, chemical bonding or embedding.

7. The method for restoring aquaculture tail water with photosynthetic bacteria of claim 6, wherein the carrier material is one or more of activated carbon, diatomaceous earth, high molecular polymer and ceramic material; the nano particles are nano titanium dioxide, nano zinc oxide or nano iron.

8. The method for restoring aquaculture tail water by photosynthetic bacteria of claim 1 wherein the bioreactor is an oxidation pond, constructed wetland or sequencing batch reactor.

9. The method for restoring aquaculture tail water by photosynthetic bacteria of claim 1 wherein the method for inoculating the microalgae-microorganism symbiont to the immobilized nanoparticle carrier is stirring, soaking or dripping.

10. The method of restoring aquaculture tail water with photosynthetic bacteria of claim 1 wherein the aquatic plant is one or more of reed, eichhornia crassipes, canna and allium mongolicum; the activated sludge is one or more of aerobic activated sludge, anaerobic activated sludge, anoxic activated sludge and biomembrane activated sludge.