Sewage treatment rubber ball with microorganisms embedded in MgFe-LDO / AC composite material as well as preparation and application of sewage treatment rubber ball

Abstract

The invention relates to the technical field of environmental functional materials, and particularly discloses sewage treatment rubber balls with microorganisms embedded in an MgFe-LDO / AC composite material as well as preparation and application of the sewage treatment rubber balls. Activated carbon is subjected to acid pickling and high-temperature calcination to form a porous carrier, MgFe-LDO is loaded through a hydrothermal synthesis method to construct a composite material, and a bacterial-algae symbiotic system and a sodium alginate gel embedding technology are combined to prepare the composite functional rubber ball. Compared with a common immobilized rubber ball, the rubber ball has the phosphate adsorption memory effect of MgFe-LDO and the NH4 < + > adsorption performance of activated carbon, is especially suitable for a decentralized sewage treatment system with low C / N ratio and high load fluctuation, and provides an efficient and stable solution for synchronous nitrogen and phosphorus removal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, and particularly relates to a multifunctional glue ball formed by a composite material based on activated carbon loaded layered double metal oxide (LDO) and microorganisms in cooperation with embedding and application of the multifunctional glue ball in sewage treatment. BACKGROUND

[0002] The rapid development of aquaculture industry leads to a sharp increase in tail water discharge, and the high concentration of nitrogen and phosphorus pollutants often exceeds the carrying capacity of water bodies. The discharge of poorly treated aquaculture tail water can cause water eutrophication and other ecological hazards. The biological remediation technology based on microalgae, especially the bacteria-algae symbiotic system, can effectively utilize sewage resources, enhance the pollutant removal efficiency and improve the recovery potential of algal biomass. However, the current aquaculture, especially the decentralized aquaculture system, has small scale and water quality fluctuates dramatically. The traditional activated sludge method has problems such as microbial loss and poor system stability (Burger et Fe., The influence of protruding filamentous bacteria on floc stability and solid-liquid separation in the activated sludge process, Water Research, 123 (2017) 578-585.). Although the existing embedding technology can fix microorganisms, it has insufficient buffering capacity for sudden nitrogen and phosphorus shock loads, and a single carrier material is difficult to simultaneously achieve nitrogen and phosphorus adsorption and microbial protection. Therefore, adding a substrate with dual functions of adsorption and slow release to the microbial treatment system is most likely to become a breakthrough to solve the above problems.

[0003] The adsorption performance of activated carbon makes it have excellent absorption effect on NH4 + Research has shown that the layered double oxide (LDO) obtained by calcining layered double metal hydroxide (LDH) has a "memory effect" and can restore the LDH structure by rehydrating and combining anions. Benefiting from this feature and a larger specific surface area, LDO shows better phosphate adsorption potential. Using activated carbon as a carrier of LDO not only improves its dispersibility and stability, but also significantly enhances its adsorption capacity, broadens its application field, and enables the MgFe-LDO / AC composite material to have excellent performance in the field of water treatment, especially in the application of relieving hydraulic load shock in the microbial treatment system. However, there are few applications of MgFe-LDO / AC in such systems at present.

[0004] Immobilization technology effectively promotes the cultivation of microbial community by immobilizing cells in carriers. Compared with free cells, immobilized carriers can effectively prevent the loss of biomass and provide higher operation flexibility and separation convenience. Alginate is an economical and efficient matrix that can easily embed microbial cells in alginate beads.

[0005] In view of the above status, it is urgent to develop an immobilized microbial technology based on MgFe-LDO / AC composite material, which is suitable for removal of nitrogen and phosphorus pollutants in low C / N water body, especially in decentralized wastewater treatment systems and systems under high load fluctuation conditions. SUMMARY

[0006] In order to overcome the above-mentioned deficiencies existing in the prior art, the present application provides a preparation method of wastewater treatment gel balls embedded with microorganisms by MgFe-LDO / AC composite material, which aims to overcome the problems that the existing embedding technology can fix microorganisms, but has insufficient buffering capacity for sudden nitrogen and phosphorus impact load, and single carrier material is difficult to simultaneously realize nitrogen and phosphorus adsorption and microorganism protection.

[0007] A preparation method of wastewater treatment gel balls embedded with microorganisms by MgFe-LDO / AC composite material, comprising the following steps:

[0008] (1) Pretreatment and activation of activated carbon:

[0009] Select 200 mesh activated carbon, then soak the activated carbon in 1-2 mol / L HCl solution, rinse the activated carbon to neutral with deionized water after soaking for 2-4 h, and dry for standby use;

[0010] (2) Synthesis of composite material:

[0011] Dissolve MgCl2 and FeCl3 in deionized water to prepare metal salt solutions with different molar ratios, add the activated activated carbon after acid pickling in step (1), then adjust the pH to 10-12 with NaOH and Na2CO3 solution, heat to 60-80℃, hydrothermal aging for 12-24 h with continuous stirring; then filter and wash with deionized water to neutral pH, dry at 60-80℃ for 12-24 h; finally, calcine the obtained material at 350-500℃ for 3-5 h to obtain MgFe-LDO / AC composite material;

[0012] (3) Preparation of bacterial and algal suspension:

[0013] Mix activated sludge and chlorella according to the proportion, centrifuge and resuspend in deionized water to form a bacterial and algal suspension with a mass concentration of 2-3 g / L;

[0014] (4) Preparation of gel balls:

[0015] The algal-bacterial suspension of step (3) is mixed with a 20-40 g / L sodium alginate solution at a volume ratio of 1:2-2:1, the MgFe-LDO / AC composite material of step (2) is added, and after stirring, it is injected into a 20-30 g / L CaCl2 solution to cross-link to form sewage treatment gel balls with a diameter of 3-5 mm.

[0016] Further, the molar ratio of magnesium salt to iron salt in the mixed solution in step (2) is (1-3):1.

[0017] Further, the solid-liquid ratio of the activated activated carbon after pickling in step (2) to the metal salt solution is (1-2):10 g / mL.

[0018] Further, the activated sludge in step (3) is sieved twice before use to remove particulate impurities therein, and the treated activated sludge is placed in an environment at 25-28℃ and domesticated and cultured using wastewater for 12-15 days.

[0019] Further, in the wastewater, NH4 + The concentration of NO3 - The concentration of NO3

[0020] Further, the chlorella in step (3) is inoculated in a sterilized BG11 medium and cultured at a temperature of 25±1℃, an illumination intensity of 5000±500 lux, and a light / dark cycle of 12 / 12 h for 6-8 days.

[0021] Further, the dry weight mixing ratio of the activated sludge to the chlorella in step (3) is (1-2):1.

[0022] Further, the addition amount of the MgFe-LDO / AC composite material in the mixed solution of the algal-bacterial suspension and the sodium alginate solution in step (4) is (2-2.5) g / 50 ml.

[0023] The application also provides the sewage treatment gel balls with microorganisms embedded by the MgFe-LDO / AC composite material prepared by the preparation method.

[0024] The sewage treatment gel balls with microorganisms embedded by the MgFe-LDO / AC composite material provided by the application can be used for wastewater treatment.

[0025] Compared with the prior art, the application has the beneficial technical effects that:

[0026] The preparation method of the MgFe-LDO / AC composite material embedding microbial gel balls used in the application is as follows: first, porous activated carbon is prepared for the synthesis of the MgFe-LDO / AC composite material, then algal bacterial suspension is prepared, then the MgFe-LDO / AC composite material, the algal bacterial suspension and a sodium alginate solution are mixed, and finally a crosslinking agent is dropped to obtain the gel balls.

[0027] In the application, the introduction of the activated carbon improves the dispersibility and the anti-scouring performance of the LDH, and effectively prevents the defects that the traditional LDH material is easy to decompose in the water body.

[0028] In the application, the porous structure on the surface of the MgFe-LDO / AC composite material is beneficial to adsorption, and provides a carrier for the adhesion and growth of the microorganisms, and is suitable for the biological enhanced sewage treatment process.

[0029] In the application, the sodium alginate is used as the embedding material, the gel has good mechanical strength, the inside is a porous structure, and the biological toxicity is small, so the sodium alginate is an economical and efficient substrate, and can easily embed and fix the microbial cells.

[0030] The MgFe-LDO / AC composite material embedding microbial gel balls used in the application has excellent adsorption capacity in the removal of phosphate and ammonia nitrogen, and is suitable for the nitrogen and phosphorus removal requirements of low-concentration sewage.

[0031] The mild wet chemical process is adopted in the application, the complex equipment requirement is avoided, the process has strong repeatability, and has good industrial application prospects. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application are described in detail below. In the following description, a large number of specific details are described in order to facilitate a full understanding of the application. However, the application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the concept of the application, so the application is not limited by the specific embodiments disclosed below.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the application belongs. The terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit the application.

[0034] In the present invention, the numerical ranges are continuous and include the minimum and maximum values of the range, as well as every value between the minimum and maximum values, unless otherwise specifically stated. Further, when ranges are provided, the range includes each integer within the range, unless otherwise specifically stated. In addition, when multiple ranges are provided, the ranges can be combined. In other words, unless otherwise specifically stated, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein.

[0035] In the present invention, the percentage content refers to mass percentage for solid-liquid mixing and solid-solid mixing, and refers to volume percentage for liquid-liquid mixing, unless otherwise specifically stated.

[0036] In the present invention, the percentage concentration refers to final concentration, unless otherwise specifically stated. The final concentration refers to the proportion of the added component in the system after the component is added.

[0037] In the present invention, the temperature parameter allows for constant temperature treatment and treatment within a certain temperature range, unless otherwise specifically limited. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. In the first aspect of the present invention, a preparation method of MgFe-LDO / AC composite material is provided, which exhibits good phosphate adsorption capacity, comprising the following steps:

[0038] (1) Pretreatment and activation of activated carbon;

[0039] Select 200-mesh activated carbon, then soak the activated carbon in a 1-2 mol / L HCl solution, rinse the activated carbon raw material to neutral with deionized water after soaking for 2-4 h, and dry for standby use;

[0040] (2) Synthesis of composite material:

[0041] Dissolve MgCl2 and FeCl3 in deionized water to prepare a metal salt solution with different molar ratios, add the activated activated carbon described in step (1), then adjust the pH to 10-12 with NaOH and Na2CO3 solution, heat to 60-80°C, hydrothermal aging for 12-24 h with continuous stirring; then filter and wash with deionized water to neutral pH, dry at 60-80°C for 12-24 h; finally, calcine the obtained material at 350-500°C for 3-5 h to obtain MgFe-LDO / AC composite material.

[0042] In one specific example, the molar ratio of magnesium salt to iron salt in step (2) is (1-3): 1. It can be understood that the molar ratio of magnesium salt to iron salt includes but is not limited to 1:1, 2:1, and 3:1.

[0043] In one embodiment, the pH of the metal salt solution in step (2) is 10-12. It is understood that the pH of the metal salt solution includes, but is not limited to, 10, 10.5, 11.5, 12.

[0044] In one embodiment, the calcination temperature in step (2) is 350-500℃. It is understood that the calcination temperature includes, but is not limited to, 350℃, 400℃, 450℃, 500℃.

[0045] In a second aspect, the present application provides a method for preparing a wastewater treatment microbial-embedded gel ball of MgFe-LDO / AC composite material, comprising the following steps:

[0046] (1) Preparation of a bacteria-algae suspension:

[0047] Mix the activated sludge and Chlorella with a ratio of (1-2):1, centrifuge and resuspend in deionized water to form a bacteria-algae suspension with a mass concentration of 2-3g / L;

[0048] (2) Preparation of a gel ball:

[0049] Mix the bacteria-algae suspension of step (1) with a sodium alginate solution with a mass concentration of 20-40g / L at a volume ratio of 1:1, add MgFe-LDO / AC composite material, and the addition amount is (2-2.5)g / 50ml; After stirring, inject a CaCl2 solution with a mass concentration of 20-30g / L to crosslink and form a gel ball with a diameter of 3-5mm.

[0050] In one embodiment, the ratio of the activated sludge to Chlorella in step (1) is (1-2):1. It is understood that the ratio includes, but is not limited to, 1:1, 2:1.

[0051] In one embodiment, the mass concentration of the bacteria-algae suspension in step (1) is 2-3g / L. It is understood that the concentration of the bacteria-algae suspension includes, but is not limited to, 2g / L, 2.5g / L, 3g / L.

[0052] In one embodiment, the addition amount of the MgFe-LDO / AC composite material in step (2) is (2-2.5)g / 50ml. It is understood that the addition amount of the MgFe-LDO / AC composite material includes, but is not limited to, 2g / 50ml, 2.5g / 50ml.

[0053] In one of the specific examples, the sodium alginate solution in step (2) has a mass concentration of 20-40 g / L; the CaCl2 solution has a mass concentration of 20-30 g / L. Understandably, the concentration of the sodium alginate includes but is not limited to 20 g / L, 30 g / L, 40 g / L; the concentration of the CaCl2 solution includes but is not limited to 20 g / L, 25 g / L, 30 g / L.

[0054] In a third aspect of the present application, the application provides a use of the MgFe-LDO / AC composite material embedding microorganisms in wastewater treatment as described above, which exhibits excellent adsorption capacity in the removal of phosphate and ammonia nitrogen.

[0055] The technical solutions of the present application are further described below through specific examples. It should be understood that the implementation of the present application is not limited to the following examples, and any form of modification and / or change of the present application will fall within the scope of protection of the present application.

[0056] Example 1

[0057] (1) Pretreatment and activation of activated carbon;

[0058] Take natural activated carbon, grind and sieve to 200 mesh, then soak the activated carbon in 1 mol / L HCl solution, rinse the activated carbon raw material to neutral with deionized water after soaking for 2 h, and dry at 80℃ for 12 h for standby;

[0059] (2) Synthesis of composite material:

[0060] Take MgCl2 (0.1 mol) and FeCl3 (0.05 mol) according to the molar ratio of Mg:Fe = 2:1, dissolve in 200 mL deionized water; add 2 mol / L NaOH solution and 1 mol / L NaCO3 solution to adjust the pH to 10.5, stir for 3 h to form a uniform precursor solution;

[0061] Add 5 g of activated activated carbon to the precursor solution, with a solid-liquid ratio of 1:10 g / mL, and continue to stir at 80℃ for 12 h, then filter and wash with deionized water to neutral pH, and dry at 80℃ for 12 h; finally, calcine the obtained material at 350℃ for 3 h to obtain MgFe-LDO / AC composite material.

[0062] Example 2

[0063] (1) Pretreatment and activation of activated carbon;

[0064] Take natural activated carbon, grind and sieve to 200 mesh, then soak the activated carbon in 1 mol / L HCl solution, rinse the activated carbon raw material to neutral with deionized water after soaking for 2 h, and dry at 80℃ for 12 h for standby;

[0065] (2) Synthesis of composite material:

[0066] MgCl2(0.1125 mol) and FeCl3(0.0375 mol) were weighed according to a molar ratio of Mg:Fe = 2:1, and dissolved in 200 mL of deionized water; 2 mol / L NaOH solution and 1 mol / L NaCO3 solution were added to adjust the pH to 10.5, and stirred for 3 h to form a uniform precursor solution;

[0067] 5 g of activated activated carbon was added to the precursor solution, with a solid-liquid ratio of 2:10 g / mL, and the temperature was raised to 80°C for continued stirring for 12 h, and then filtered and washed with deionized water to neutral pH, and dried at 80°C for 12 h; finally, the obtained material was calcined at 350°C for 3 h to obtain the MgFe-LDO / AC composite material.

[0068] Example 3

[0069] (1) Pretreatment and activation of activated carbon:

[0070] Natural activated carbon was ground and sieved to 200 mesh, and then the activated carbon was soaked in 1 mol / L HCl solution, washed with deionized water to neutralize the activated carbon raw material after soaking for 2 h, and dried at 80°C for 12 h for standby;

[0071] (2) Synthesis of composite material:

[0072] MgCl2(0.1125 mol) and FeCl3(0.0375 mol) were weighed according to a molar ratio of Mg:Fe = 2:1, and dissolved in 200 mL of deionized water; 2 mol / L NaOH solution and 1 mol / L NaCO3 solution were added to adjust the pH to 10.5, and stirred for 3 h to form a uniform precursor solution;

[0073] 5 g of activated activated carbon was added to the precursor solution, with a solid-liquid ratio of 1:10 g / mL, and the temperature was raised to 80°C for continued stirring for 12 h, and then filtered and washed with deionized water to neutral pH, and dried at 80°C for 12 h; finally, the obtained material was calcined at 500°C for 3 h to obtain the MgFe-LDO / AC composite material.

[0074] Example 4

[0075] (1) The activated sludge collected from the aerobic section of a sewage treatment plant in Guangzhou City was screened twice (screen hole diameter of 1 mm) to remove particulate impurities. The treated activated sludge was placed in a laboratory environment at 25°C, and the configured wastewater (NH4 + -N = 10 mg / L, NO3 -The activated sludge was acclimated in the wastewater with the following composition: N = 20 mg / L, TP = 5 mg / L, COD = 45 mg / L for 15 days. After the cultivation, the supernatant was removed and the remaining high-concentration activated sludge was used as the bacterial inoculum for the experiment.

[0076] (2) The Chlorella was then cultured in sterilized BG11 medium at a temperature of 25 ± 1 °C, an illumination intensity of 5000 lux, and a light / dark cycle of 12 / 12 h for 8 days. The dry weight of the Chlorella obtained after the preliminary culture was 0.65 g / L, and the activated sludge was 23 g / L.

[0077] (3) The microorganism with a dry weight of 0.0325 g was resuspended in deionized water (mass ratio of 1:1 in the bacteria-algae mixture) to form a 50 mL suspension.

[0078] (4) The microorganism suspension was mixed with a sodium alginate solution with a mass concentration of 20 g / L to a final concentration of 10 g / L, and 0.5 g of the MgFe-LDO / AC composite material prepared in Example 1 was added to the mixture and stirred thoroughly. The mixed solution was injected into a CaCl2 solution with a mass concentration of 20 g / L using a syringe to form a hydrogel bead.

[0079] (5) 100 mL of the particles were added to a conical flask containing the simulated wastewater. The experiment used an LED lamp to provide an illumination intensity of 5000 lux, and the light / dark ratio was set to 12 h:12 h at room temperature.

[0080] Example 5

[0081] (1) The activated sludge collected from the aerobic section of a sewage treatment plant in Guangzhou was screened twice (screening hole diameter of 1 mm) to remove particulate impurities. The treated activated sludge was placed in a laboratory environment at 25 °C, and the prepared wastewater (NH4 + -N = 10 mg / L, NO3 - The activated sludge was acclimated in the wastewater with the following composition: N = 20 mg / L, TP = 5 mg / L, COD = 45 mg / L for 15 days. After the cultivation, the supernatant was removed and the remaining high-concentration activated sludge was used as the bacterial inoculum for the experiment.

[0082] (2) The Chlorella was then cultured in sterilized BG11 medium at a temperature of 25 ± 1 °C, an illumination intensity of 5000 lux, and a light / dark cycle of 12 / 12 h for 8 days. The dry weight of the Chlorella obtained after the preliminary culture was 0.65 g / L, and the activated sludge was 23 g / L.

[0083] (3) The microorganism with a dry weight of 0.0325 g was resuspended in deionized water (mass ratio of 1:1 in the bacteria-algae mixture) to form a 50 mL suspension.

[0084] (4) The microbial suspension was mixed with a 40 g / L sodium alginate solution to a final concentration of 20 g / L, and 1.0 g of MgFe-LDO / AC composite material prepared in Example 1 was added to the mixture and stirred thoroughly. The mixed solution was injected into a 30 g / L CaCl2solution using a syringe to form hydrogel beads.

[0085] (5) 100 mL of the granules were added to a conical flask containing simulated wastewater. The experiment used an LED lamp to provide an illumination intensity of 5000 lux, and the light / dark ratio was set to 12h:12h at room temperature.

[0086] Example 6

[0087] (1) The activated sludge collected from the aerobic section of a sewage treatment plant in Guangzhou City was screened twice (screening hole diameter of 1 mm) to remove particulate impurities. The treated activated sludge was placed in a laboratory environment at 25°C and acclimated using the prepared simulated wastewater for 15 days. After the cultivation was completed, the supernatant was removed, and the remaining high-concentration activated sludge was used as the bacterial inoculum for the experiment.

[0088] (2) Chlorella was then cultured in a sterilized BG11 medium at a temperature of 25±1°C, an illumination intensity of 5000 lux, and a light / dark cycle of 12 / 12h for 8 days. The dry weight of Chlorella obtained after the preliminary culture was 0.65 g / L, and the dry weight of activated sludge was 23 g / L.

[0089] (3) The microbial suspension was mixed with a 40 g / L sodium alginate solution to a final concentration of 20 g / L, and 1.0 g of MgFe-LDO / AC composite material prepared in Example 1 was added to the mixture and stirred thoroughly. The mixed solution was injected into a 30 g / L CaCl2solution using a syringe to form hydrogel beads.

[0090] (4) The microbial suspension was mixed with a 40 g / L sodium alginate solution to a final concentration of 20 g / L, and 1.0 g of MgFe-LDO / AC composite material prepared in Example 1 was added to the mixture and stirred thoroughly. The mixed solution was injected into a 30 g / L CaCl2solution using a syringe to form hydrogel beads.

[0091] (5) 100 mL of the granules were added to a conical flask containing wastewater (NH4 + -N = 10 mg / L, NO3 - -N = 20 mg / L, TP = 5 mg / L, COD = 45 mg / L). The experiment used an LED lamp to provide an illumination intensity of 5000 lux, and the light / dark ratio was set to 12h:12h at room temperature.

[0092] The MgFe-LDO / AC composite material prepared in Examples 1-3 was added to a conical flask containing wastewater for effect testing, and the phosphate adsorption capacity thereof is shown in Table 1 below; the wastewater treatment effect of the wastewater treatment gel balls embedding microorganisms based on the MgFe-LDO / AC composite material prepared in Examples 4-6 is shown in Table 2 below.

[0093] Table 1

[0094] Group Example 1 Example 2 Example 3 Phosphate adsorption capacity (mg / g) 12.452 10.261 9.743

[0095] Table 2

[0096] Group Example 4 Example 5 Example 6 NH4 + - N (mg / L) 10 10 10 NH4 + -N(mg / L) 0.842 0.532 0.256 NH4 + - N removal rate (%)]] 91.58 94.68 97.44 Raw water NO3 - - N (mg / L) 20 20 20 treatment NNO3 - - N (mg / L) 17.526 15.261 13.638 NO3 - - N removal rate (%)]] 12.37 23.695 31.81 Raw water TP (mg / L) 5 5 5 TP after treatment (mg / L) 0.642 0.076 0.064 TP removal rate (%) 87.16 98.48 98.72 Raw water COD (mg / L) 45 45 45 COD after treatment (mg / L) 17 14 13 COD removal rate (%) 62.22 68.89 71.11

[0097] In summary, the present application provides a preparation method of wastewater treatment gel balls embedding microorganisms based on the MgFe-LDO / AC composite material, which has high efficiency and stability. By combining a plurality of optimized processes, the problems of insufficient adsorption performance and poor environmental tolerance of single material are successfully solved. The material has wide application potential in the field of water treatment, and provides technical support and theoretical basis for low-cost and high-efficiency decentralized wastewater treatment technology.

[0098] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present application.

[0099] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are all within the scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A method for preparing wastewater treatment gel balls encapsulating microorganisms in a MgFe-LDO / AC composite material, characterized in that... The method comprises the following steps: (1) Pretreatment and activation of activated carbon: Select 200 mesh activated carbon, then soak the activated carbon in 1-2 mol / L HCl solution, rinse the activated carbon to neutral with deionized water after soaking for 2-4 h, and dry for standby use; (2) Synthesis of composite material: Dissolve MgCl2 and FeCl3 in deionized water to prepare a metal salt solution with different molar ratios, add the activated carbon after acid washing in step (1), then adjust the pH to 10-12 with NaOH and Na2CO3 solution, heat to 60-80℃, hydrothermal aging for 12-24 h with continuous stirring; then filter and wash with deionized water to neutral pH, dry at 60-80℃ for 12-24 h; finally, calcine the obtained material at 350-500℃ for 3-5 h to obtain MgFe-LDO / AC composite material; (3) Preparation of bacteria-algae suspension: Mix activated sludge and chlorella in proportion, centrifuge, and resuspend in deionized water to form a bacteria-algae suspension with a mass concentration of 2-3 g / L; (4) Preparation of gel balls: Mix the bacteria-algae suspension in step (3) with a sodium alginate solution with a mass concentration of 20-40 g / L at a volume ratio of 1:2-2:1, add the MgFe-LDO / AC composite material in step (2), stir, and then inject into a CaCl2 solution with a mass concentration of 20-30 g / L to crosslink and form wastewater treatment gel balls with a diameter of 3-5 mm, which are embedded with microorganisms.

2. The method for preparing a wastewater treatment gel ball embedded with microorganisms of MgFe-LDO / AC composite material according to claim 1, characterized in that The molar ratio of magnesium salt to iron salt in the mixed solution in step (2) is (1-3):

1.

3. The method for preparing wastewater treatment gel balls encapsulating microorganisms using MgFe-LDO / AC composite material according to claim 1, characterized in that... The solid-liquid ratio of the activated carbon after acid washing and activation in step (2) to the metal salt solution is (1-2):10 g / mL.

4. The method for preparing wastewater treatment gel balls encapsulating microorganisms in MgFe-LDO / AC composite material according to claim 1, characterized in that... The activated sludge in step (3) is sieved twice before use to remove particulate impurities. The treated activated sludge is placed in an environment with a temperature of 25-28℃ and domesticated and cultured with wastewater for 12-15 days.

5. The method for preparing wastewater treatment gel balls encapsulating microorganisms in MgFe-LDO / AC composite material according to claim 4, characterized in that... The NH4 + The -N concentration is 5-15 mg / L, the NO3 - The -N concentration is 15-25 mg / L, the TP concentration is 3-5 mg / L, and the COD concentration is 40-50 mg / L.

6. The method for preparing wastewater treatment gel balls encapsulating microorganisms using MgFe-LDO / AC composite material according to claim 1, characterized in that... The chlorella in step (3) is inoculated in sterilized BG11 medium and cultured for 6-8 days under the conditions of a temperature of 25±1℃, a light intensity of 5000±500 lux, and a light / dark cycle of 12 / 12 h.

7. The method for preparing wastewater treatment gel balls encapsulating microorganisms in MgFe-LDO / AC composite material according to claim 1, characterized in that... The dry weight mixing ratio of activated sludge to chlorella in step (3) is (1-2):

1.

8. The method for preparing wastewater treatment gel balls encapsulating microorganisms using MgFe-LDO / AC composite material according to claim 1, characterized in that... The addition amount of MgFe-LDO / AC composite material in step (4) in the mixed solution formed by the bacteria-algae suspension and the sodium alginate solution is (2-2.5) g / 50 ml.

9. The wastewater treatment gel balls embedded with microorganisms prepared by the method of any one of claims 1-8.

10. The use of a MgFe-LDO / AC composite material according to claim 9 for embedding microorganisms in wastewater treatment beads, characterized in that, The wastewater treatment gel balls embedded with microorganisms of MgFe-LDO / AC composite material are used for wastewater treatment.