A method for treating aquaculture wastewater using immobilized algae cells

Abstract

The present invention discloses a method for treating aquaculture wastewater with immobilized algae cells, and relates to the technical field of water treatment. The immobilized algae cells use sodium alginate or a sodium alginate derivative modified with a pyridine compound as a carrier, and activated carbon as an adsorbent to embed and fix the algae cells. The obtained immobilized algae cells have good heavy metal ion removal effect, ammonia nitrogen removal effect and total organic carbon removal effect in wastewater treatment. In addition, the present invention also uses N-(5-nitro-2-pyridyl)-1,2-ethylenediamine to modify sodium alginate, and then the obtained pyridine compound-modified sodium alginate derivative is used for the preparation of immobilized algae cells, so that the immobilized algae cells have better heavy metal ion removal effect, ammonia nitrogen removal effect and total organic carbon removal effect in wastewater treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a method for treating aquaculture wastewater by using immobilized algae cells. Background Art

[0002] With the increasing demand for aquatic products and the advancement and expansion of aquaculture technology, my country's aquaculture industry has increasingly adopted high-density, intensive farming models. The impact of aquaculture wastewater on the aquatic environment has attracted widespread attention, and aquaculture wastewater treatment technology has also developed accordingly. The main pollutants in aquaculture wastewater include leftover feed, organic waste rich in nitrogen and phosphorus, chemical residues, and toxic substances. High concentrations of nitrogen and phosphorus can lead to eutrophication of water bodies. The main treatment methods for aquaculture wastewater include physical treatment, chemical treatment, physicochemical treatment, and biological treatment.

[0003] With global water shortages and increasing aquatic pollution, the comprehensive utilization and harmless treatment of aquaculture wastewater is an inevitable research direction for all countries. While traditional physical and chemical treatment methods are simple, they require significant labor and processing costs, making them unsuitable for sustainable development. Traditional microbial treatment technologies primarily rely on the selection and propagation of naturally occurring microbial populations, resulting in low levels of pollutant degradation. Genetic modification and targeted breeding of engineered strains with exceptionally high degradation capabilities are necessary to significantly enhance these microbial degradation capabilities to meet wastewater treatment requirements. To enhance enzyme activity, immobilization technology is a highly active research area.

[0004] Immobilized biotechnology (IMB) involves the use of physical or chemical methods to immobilize free-living microbial cells or enzymes on a carrier, confining them to a specific area while maintaining their activity and enabling repeated use. This technology was developed in the 1970s. With the rapid development of society, the massive discharge of domestic sewage, livestock and poultry wastewater, and industrial wastewater has caused significant damage to the aquatic ecosystem. Consequently, immobilization technology for wastewater treatment has emerged. Immobilization enhances the metabolic activity of microbial cells and provides a mild environment for their growth. Immobilized microbial cells are resistant to high temperatures, toxicity, and acidity and alkalinity. Using this technology to treat digestate not only results in rapid and efficient reactions but also allows for resource utilization. This technology is highly effective in removing pollutants and has been gaining popularity in wastewater treatment in recent years.

[0005] Immobilization requires an ideal carrier to ensure that substances within the matrix can easily enter the cells, while also considering the leakage of immobilized cells. Existing choices for immobilization carriers can be roughly divided into two categories: polymer gel carriers and organic synthetic carriers. The adsorption mechanism of activated carbon is mainly through physical adsorption and microbial degradation, utilizing the carbon surface of activated carbon to adsorb one or more organic substances in the water to achieve the purpose of purifying the water. Therefore, the present invention uses sodium alginate or a sodium alginate derivative modified with a pyridine compound as a carrier and activated carbon as an adsorbent to prepare an immobilized algae cell. Summary of the Invention

[0006] The object of the present invention is to provide a method for treating aquaculture wastewater using immobilized algae cells, wherein the immobilized algae cells have good heavy metal ion removal effect, ammonia nitrogen removal effect and total organic carbon removal effect in wastewater treatment.

[0007] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0008] An immobilized algae cell is prepared by embedding and fixing the algae cell with a carrier and an adsorbent;

[0009] The carrier is selected from at least one of sodium alginate and sodium alginate derivatives modified with pyridine compounds;

[0010] The sodium alginate derivative modified with the pyridine compound is obtained by modifying sodium alginate with N-(5-nitro-2-pyridyl)-1,2-ethylenediamine.

[0011] The present invention also discloses a method for preparing a sodium alginate derivative modified with a pyridine compound, comprising: subjecting sodium alginate to an oxidative ring-opening treatment, and then reacting the sodium alginate with N-(5-nitro-2-pyridyl)-1,2-ethylenediamine to a Schiff base reaction to obtain the sodium alginate derivative modified with a pyridine compound.

[0012] The present invention provides a method for preparing a sodium alginate derivative modified with a pyridine compound. The method comprises the following steps: performing an oxidative ring-opening treatment on sodium alginate to generate an aldehyde group; then reacting the aldehyde group with an amino group in N-(5-nitro-2-pyridyl)-1,2-ethylenediamine to prepare the sodium alginate derivative modified with the pyridine compound; and then using the sodium alginate derivative modified with the pyridine compound to prepare immobilized algae cells. The immobilized algae cells have good heavy metal ion removal effect, ammonia nitrogen removal effect, and total organic carbon removal effect in wastewater treatment.

[0013] Specifically, the preparation method of the above-mentioned pyridine compound-modified sodium alginate derivative comprises the following steps:

[0014] Sodium alginate is added to ethanol (the mass volume ratio of sodium alginate to ethanol is: 1 g: 8-15 mL), stirred and dispersed uniformly, and then a 0.25-0.35 mol / L sodium periodate solution is added. The mixture is reacted in the dark at room temperature for 5-8 hours, and then ethylene glycol is added to terminate the reaction. The mixture is filtered and washed 3-5 times with a 60-75 wt% ethanol aqueous solution to obtain oxidized sodium alginate. Deionized water is added to the oxidized sodium alginate (the mass volume ratio of the two is: 1 g: 20-30 mL) to obtain an oxidized sodium alginate solution. N-(5-nitro-2-pyridyl)-1,2-ethylenediamine is then slowly added to the oxidized sodium alginate solution at 45-55°C while stirring. The reaction is continued at a constant temperature for 10-15 hours, cooled to room temperature, and ethanol is added (the amount of ethanol added is 3-5 times the volume of the reaction solution). The mixture is then incubated at 3-7°C for 6-10 hours, filtered, and freeze-dried to obtain a pyridine-modified sodium alginate derivative.

[0015] According to an embodiment of the present invention, the mass volume ratio of the sodium alginate to the sodium periodate solution is: 1 g: 8-15 mL; the mass volume ratio of the sodium alginate to the ethylene glycol is: 1 g: 1-1.3 mL.

[0016] According to an embodiment of the present invention, the mass ratio of the sodium alginate to N-(5-nitro-2-pyridyl)-1,2-ethylenediamine is 1:0.8-1.5.

[0017] The present invention also discloses the use of the sodium alginate derivative modified with the pyridine compound prepared by the preparation method in preparing immobilized algae cells.

[0018] A wastewater treatment agent comprises the above-mentioned immobilized algae cells.

[0019] Specifically, the method for preparing the immobilized algae cells comprises:

[0020] Take the algae cells in the logarithmic phase (algae cell density is 1.5×10 7 -2×10 7 cell / mL), centrifuged at 4000-5000 r / min for 10-20 min, discarded the supernatant, washed with sterilized ultrapure water, centrifuged, and repeated washing and centrifugation 3-5 times to obtain algae cell concentrate;

[0021] Ultrapure water is added to the carrier and the adsorbent (the mass volume ratio of the carrier to the ultrapure water is: 1g:20-25mL), and the mixture is sterilized at 120-125°C and 100-105kPa for 15-25 minutes to obtain a sterilized mixed solution. The algae cell concentrate is then added to the sterilized mixed solution, mixed evenly, and then dripped into a calcium chloride solution with a concentration of 2-4wt%. The mixture is hardened at 3-5°C for 15-20 hours, removed, and washed with ultrapure water 3-5 times to obtain immobilized algae cells.

[0022] According to an embodiment of the present invention, the algae cells are selected from at least one of Scenedesmus quadricauda cells and Chlorella vulgaris cells.

[0023] According to an embodiment of the present invention, the adsorbent includes activated carbon.

[0024] According to an embodiment of the present invention, the activated carbon is 40-60 mesh powdered activated carbon.

[0025] According to an embodiment of the present invention, the mass ratio of the carrier to the adsorbent is 1:0.1-0.15.

[0026] According to an embodiment of the present invention, the volume ratio of the sterilized mixed solution to the algae cell concentrate is 1:0.8-1.3.

[0027] The invention also discloses the use of the immobilized algae cells in treating aquatic product breeding wastewater.

[0028] A method for treating aquatic product breeding wastewater comprises: adding the above-mentioned immobilized algae cells into the aquatic product breeding wastewater for treatment.

[0029] According to an embodiment of the present invention, the usage of the immobilized algae cells is 4-7 g / L.

[0030] The beneficial effects of the present invention include:

[0031] The present invention obtains an immobilized algae cell. The present invention uses sodium alginate or a sodium alginate derivative modified with a pyridine compound as a carrier and activated carbon as an adsorbent to embed and immobilize the algae cells. The obtained immobilized algae cells have good heavy metal ion removal effect, ammonia nitrogen removal effect, and total organic carbon removal effect in wastewater treatment. In addition, the present invention also uses N-(5-nitro-2-pyridyl)-1,2-ethylenediamine to modify sodium alginate, and then uses the obtained pyridine compound-modified sodium alginate derivative for the preparation of the immobilized algae cells, so that the immobilized algae cells have better heavy metal ion removal effect, ammonia nitrogen removal effect, and total organic carbon removal effect in wastewater treatment.

[0032] Therefore, the present invention provides a method for treating aquaculture wastewater using immobilized algae cells, wherein the immobilized algae cells have good heavy metal ion removal effect, ammonia nitrogen removal effect and total organic carbon removal effect in wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The infrared spectra of the sodium alginate derivative modified with pyridine compounds and sodium alginate prepared in Example 2 are tested;

[0034] Figure 2 The test results of the immobilized algae cells prepared in Examples 1 to 6 on the removal of heavy metal ions from wastewater are shown;

[0035] Figure 3 The results of the test on the removal of ammonia nitrogen from wastewater by the immobilized algae cells prepared in Examples 1 to 6 are as follows;

[0036] Figure 4 These are the test results of the total organic carbon removal effect of the immobilized algae cells prepared in Examples 1 to 6 in wastewater. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention are further described in detail below in conjunction with specific embodiments:

[0038] Example 1:

[0039] A method for preparing immobilized algae cells, comprising:

[0040] Take the logarithmic phase Chlorella cells (the cell density of Chlorella is 1.5×10 7 cell / mL), centrifuged at 4000 r / min for 20 min, discarded the supernatant, washed with sterilized ultrapure water, centrifuged, and repeated washing and centrifugation for 3 times to obtain algae cell concentrate;

[0041] Ultrapure water was added to the sodium alginate carrier and 40-mesh powdered activated carbon adsorbent (the mass volume ratio of the carrier to the ultrapure water was 1 g:20 mL, and the mass ratio of the carrier to the adsorbent was 1:0.1), and the mixture was sterilized at 120°C and 100 kPa for 25 min to obtain a sterilized mixed solution. Algae cell concentrate was then added to the sterilized mixed solution (the volume ratio of the sterilized mixed solution to the algae cell concentrate was 1:0.8). After mixing evenly, the mixture was dropped into a 2 wt % calcium chloride solution, hardened at 3°C for 15 h, taken out, and washed three times with ultrapure water to obtain immobilized algae cells.

[0042] Example 2:

[0043] The difference between the method for preparing immobilized algae cells and Example 1 is that a sodium alginate derivative modified with a pyridine compound is used instead of sodium alginate.

[0044] A method for preparing a pyridine compound-modified sodium alginate derivative comprises the following steps:

[0045] Sodium alginate was added to ethanol (the mass volume ratio of sodium alginate to ethanol was 1 g: 8 mL), stirred and dispersed evenly, and then a sodium periodate solution with a concentration of 0.25 mol / L was added. The mixture was reacted in the dark at room temperature for 8 h, and then ethylene glycol was added to terminate the reaction. The mixture was filtered and then washed three times with a 75 wt% ethanol aqueous solution to obtain oxidized sodium alginate. Deionized water was added to the oxidized sodium alginate (the mass volume ratio of the two was 1 g: 20 mL) to obtain an oxidized sodium alginate solution. Then, N-(5-nitro-2-pyridine) was added to the oxidized sodium alginate at 45 °C. The oxidized sodium alginate solution was slowly added with stirring to form 5-nitro-2-pyridyl)-1,2-ethylenediamine. The reaction was carried out at a constant temperature for 10 hours. After cooling to room temperature, ethanol was added (the amount of ethanol added was 3 times the volume of the reaction solution). The reaction was then placed at 3°C for 6 hours, filtered, and freeze-dried to obtain a pyridine-modified sodium alginate derivative. The mass volume ratio of sodium alginate to sodium periodate solution was 1 g:8 mL; the mass volume ratio of sodium alginate to ethylene glycol was 1 g:1 mL; and the mass ratio of sodium alginate to N-(5-nitro-2-pyridyl)-1,2-ethylenediamine was 1:0.8.

[0046] Example 3:

[0047] The difference between the method for preparing immobilized algae cells and Example 2 is that the method for preparing the sodium alginate derivative modified with a pyridine compound is different.

[0048] A method for preparing a pyridine compound-modified sodium alginate derivative comprises the following steps:

[0049] Sodium alginate was added to ethanol (the mass volume ratio of sodium alginate to ethanol was 1 g: 15 mL), stirred and dispersed evenly, and then a sodium periodate solution with a concentration of 0.35 mol / L was added. The mixture was reacted for 5 h in the dark at room temperature, and then ethylene glycol was added to terminate the reaction. The mixture was filtered and then washed 5 times with a 60 wt% ethanol aqueous solution to obtain oxidized sodium alginate. Deionized water was added to the oxidized sodium alginate (the mass volume ratio of the two was 1 g: 30 mL) to obtain an oxidized sodium alginate solution. Then, N-(5-nitro-2-pyridyl)-1,2-diol was added to the oxidized sodium alginate solution at 55°C. )-1,2-ethylenediamine was slowly added to the oxidized sodium alginate solution while stirring, and the reaction was carried out at a constant temperature for 15 hours. The reaction was cooled to room temperature, and ethanol was added (the amount of ethanol added was 5 times the volume of the reaction solution). The reaction was then placed at 7°C for 10 hours, filtered, and freeze-dried to obtain a pyridine compound-modified sodium alginate derivative; the mass volume ratio of sodium alginate to sodium periodate solution was 1 g:15 mL; the mass volume ratio of sodium alginate to ethylene glycol was 1 g:1.3 mL; and the mass ratio of sodium alginate to N-(5-nitro-2-pyridyl)-1,2-ethylenediamine was 1:1.5.

[0050] Example 4:

[0051] A method for preparing immobilized algae cells differs from Example 1 in that sodium 3-morpholine-2-hydroxypropanesulfonate is added during the preparation of the immobilized algae cells; the mass ratio of sodium 3-morpholine-2-hydroxypropanesulfonate to the adsorbent is 1:10-15.

[0052] The present invention adds sodium 3-morpholine-2-hydroxypropanesulfonate during the preparation of immobilized algae cells, and the prepared immobilized algae cells are then used in wastewater treatment, thereby achieving good heavy metal ion removal effects, ammonia nitrogen removal effects, and total organic carbon removal effects in the wastewater treatment. This may be because elements such as S, N, and O in the sodium 3-morpholine-2-hydroxypropanesulfonate can form stable chelates with heavy metal ions through coordination, thereby further promoting the removal of heavy metal ions. In addition, the presence of hydroxyl groups and other groups in the sodium 3-morpholine-2-hydroxypropanesulfonate can form hydrogen bonds with ammonia nitrogen molecules, thereby further enhancing the adsorption effect of ammonia nitrogen. Furthermore, the presence of oxygen-containing functional groups in the sodium 3-morpholine-2-hydroxypropanesulfonate can enhance the adsorption of organic matter in water through the formation of hydrogen bonds, thereby further promoting the removal effect of total organic carbon.

[0053] Specifically, the method for preparing the immobilized algae cells comprises:

[0054] Take the logarithmic phase Chlorella cells (the cell density of Chlorella is 1.5×10 7cell / mL), centrifuged at 4000 r / min for 20 min, discarded the supernatant, washed with sterilized ultrapure water, centrifuged, and repeated washing and centrifugation for 3 times to obtain algae cell concentrate;

[0055] Ultrapure water was added to sodium 3-morpholine-2-hydroxypropanesulfonate (the mass volume ratio of sodium 3-morpholine-2-hydroxypropanesulfonate to ultrapure water was 1 g:20 mL). After dissolution, a 40-mesh powdered activated carbon adsorbent was added (the mass ratio of sodium 3-morpholine-2-hydroxypropanesulfonate to adsorbent was 1:10). After stirring and mixing for 30 minutes, the mixture was filtered and added to a sodium alginate carrier. Ultrapure water was then added (the mass volume ratio of the carrier to ultrapure water was 1 g:20 mL, and the mass ratio of the carrier to the adsorbent was 1:0.1). The mixture was sterilized at 120°C and 100 kPa for 25 minutes to obtain a sterilized mixture. Algae cell concentrate was then added to the sterilized mixture (the volume ratio of the sterilized mixture to the algae cell concentrate was 1:0.8). After uniform mixing, the mixture was dripped into a 2 wt% calcium chloride solution, hardened at 3°C for 15 hours, removed, and washed three times with ultrapure water to obtain immobilized algae cells.

[0056] Example 5:

[0057] A method for preparing immobilized algae cells differs from Example 1 in that sodium 3-morpholine-2-hydroxypropanesulfonate is added during the preparation of the immobilized algae cells; the mass ratio of sodium 3-morpholine-2-hydroxypropanesulfonate to the adsorbent is 1:15.

[0058] Example 6:

[0059] The difference between the method for preparing immobilized algae cells and Example 4 is that a sodium alginate derivative modified with a pyridine compound is used instead of sodium alginate.

[0060] The preparation method of the sodium alginate derivative modified with pyridine compounds is the same as that in Example 2.

[0061] Test Example 1:

[0062] Infrared spectrum test

[0063] The samples were tested using a Fourier transform infrared spectrometer (VERTEX 70, Bruker Optics, Germany) with a wavelength range of 400–4000 cm -1 .

[0064] The above test was performed on the sodium alginate derivative modified with pyridine compounds and sodium alginate prepared in Example 2. The results are as follows: Figure 1 As shown. Figure 1It can be seen that compared with the infrared spectrum of sodium alginate, the infrared spectrum of the sodium alginate derivative modified by pyridine compounds is at 1653 cm -1 There is an infrared characteristic absorption peak of pyridine ring at 1543cm -1 There is an infrared characteristic absorption peak of nitro group at 1206cm -1 There is an infrared characteristic absorption peak of CN bond at the position, indicating that N-(5-nitro-2-pyridyl)-1,2-ethylenediamine participates in the formation reaction of sodium alginate derivatives modified with pyridine compounds.

[0065] Test Example 2:

[0066] Heavy metal ion removal effect test

[0067] Take 100 mL of wastewater with an arsenic concentration of 10 mg / L, add 0.5 g of immobilized algae cells, and then shake for 4 hours. The arsenic concentration in the treated wastewater is measured using an inductively coupled plasma mass spectrometer. The heavy metal ion removal rate is calculated as follows:

[0068] F / %=[(R1-R2) / R1]×100%

[0069] Wherein, F is the heavy metal ion removal rate; R1 is the arsenic concentration in the wastewater before treatment; R2 is the arsenic concentration in the wastewater after treatment.

[0070] The above tests were performed on the immobilized algae cells obtained in Examples 1 to 6. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the heavy metal ion removal rate of Example 2 is significantly increased compared with Example 1, and Example 6 is significantly increased compared with Example 4, indicating that the sodium alginate is modified with N-(5-nitro-2-pyridyl)-1,2-ethylenediamine, and then the sodium alginate derivative modified with a pyridine compound is used for the preparation of immobilized algae cells, so that the immobilized algae cells have a good removal effect on heavy metal ions in wastewater; the heavy metal ion removal rate of Example 4 is also increased compared with Example 1, and Example 6 is increased compared with Example 2, indicating that when sodium 3-morpholine-2-hydroxypropanesulfonate is used for the preparation of immobilized algae cells, the immobilized algae cells also have a good removal effect on heavy metal ions in wastewater; the reason may be that elements such as S, N, and O in sodium 3-morpholine-2-hydroxypropanesulfonate can form stable chelates with heavy metal ions through coordination, thereby further promoting the removal of heavy metal ions.

[0071] Test Example 3:

[0072] Ammonia nitrogen removal effect test

[0073] Take 100mL of wastewater with an ammonia nitrogen content of 337mg / L, add 0.5g of immobilized algae cells, and then shake it for 4h. Then, use GL-900 multi-parameter water quality meter to test the ammonia nitrogen content in the treated wastewater.

[0074] The above tests were performed on the immobilized algae cells obtained in Examples 1 to 6. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the ammonia nitrogen removal rate is significantly increased in Example 2 compared with Example 1, and in Example 6 compared with Example 4, indicating that sodium alginate is modified with N-(5-nitro-2-pyridyl)-1,2-ethylenediamine, and then the sodium alginate derivative modified with a pyridine compound is used to immobilize algae cells, so that the immobilized algae cells have a good removal effect on ammonia nitrogen in wastewater; compared with Example 4 and Example 1, and Example 6 and Example 2, the ammonia nitrogen removal rate is also increased, indicating that when sodium 3-morpholine-2-hydroxypropanesulfonate is used for the preparation of immobilized algae cells, the immobilized algae cells also have a good removal effect on ammonia nitrogen in wastewater; the reason may be that the presence of hydroxyl groups and other groups in sodium 3-morpholine-2-hydroxypropanesulfonate forms hydrogen bonds with ammonia nitrogen molecules, further enhancing the adsorption effect on ammonia nitrogen.

[0075] Test Example 4:

[0076] Total organic carbon removal effect test

[0077] Take 100mL of wastewater with a total organic carbon content of 886mg / L, add 0.5g of immobilized algae cells, and then shake it for 4h. Then, use a multi-parameter water quality meter to test the total organic carbon content in the treated wastewater.

[0078] The above tests were performed on the immobilized algae cells obtained in Examples 1 to 6. The results are as follows: Figure 4 As shown. Figure 4 It can be seen that the total organic carbon removal rate of Example 2 is significantly increased compared with Example 1, and Example 6 is significantly increased compared with Example 4, indicating that sodium alginate is modified with N-(5-nitro-2-pyridyl)-1,2-ethylenediamine, and then the sodium alginate derivative modified with a pyridine compound is used to immobilize algae cells, so that the immobilized algae cells have a good removal effect on the total organic carbon in the wastewater; the total organic carbon removal rate is also increased compared with Example 1, and Example 6 is compared with Example 2, indicating that when sodium 3-morpholine-2-hydroxypropanesulfonate is used for the preparation of immobilized algae cells, the immobilized algae cells also have a good removal effect on the total organic carbon in the wastewater; the reason may be that the presence of oxygen-containing functional groups in sodium 3-morpholine-2-hydroxypropanesulfonate can enhance the adsorption of organic matter in water by forming hydrogen bonds, thereby further promoting the removal effect of total organic carbon.

[0079] The conventional techniques in the above embodiments are prior arts known to those skilled in the art, and thus will not be described in detail here.

[0080] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An immobilized algae cell, characterized in that: The immobilized algae cells are prepared by embedding the immobilized algae cells with a carrier, sodium 3-morpholine-2-hydroxypropanesulfonate and an adsorbent; the carrier is selected from sodium alginate modified with a pyridine compound; the adsorbent is activated carbon; in the preparation of the sodium alginate modified with a pyridine compound, the sodium alginate is subjected to an oxidative ring-opening treatment, and then undergoes a Schiff base reaction with N-(5-nitro-2-pyridyl)-1,2-ethylenediamine to obtain the sodium alginate modified with the pyridine compound.

2. The immobilized algae cell according to claim 1, characterized in that: The algae cells are selected from at least one of Scenedesmus quadricauda cells and Chlorella vulgaris cells.

3. The immobilized algae cell according to claim 1, characterized in that: The activated carbon is 40-60 mesh powdered activated carbon.

4. The immobilized algae cell according to claim 1, characterized in that: The mass ratio of the carrier to the adsorbent is 1:0.1-0.

15.

5. The immobilized algae cell according to claim 1, characterized in that: The mass ratio of the sodium alginate to N-(5-nitro-2-pyridyl)-1,2-ethylenediamine is 1:0.8-1.

5.

6. A method for treating aquaculture wastewater, comprising: The immobilized algae cells according to any one of claims 1 to 5 are added to aquaculture wastewater for treatment.

7. The method for treating aquaculture wastewater according to claim 6, characterized in that: The dosage of the immobilized algae cells is 4-7 g / L.

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