Microbial capsule for sewage treatment and preparation method thereof

Abstract

The invention relates to the technical field of environmental protection, and discloses a microbial capsule for sewage treatment and a preparation method thereof, and the method adopts a polyvinyl alcohol material as a base material, combines activated carbon powder or zeolite powder as a composite carrier, and encapsulates a microbial agent to form the microbial capsule. The invention aims to solve the problems of easy loss of bacteria, poor environmental tolerance and unstable treatment effect in a traditional biological method and the problems of poor strength and easy swelling of a traditional polyvinyl alcohol cured product, innovatively utilizes a composite cross-linking curing technology to prepare the novel microbial capsule, and significantly improves the possibility of large-scale application of the product. The microbial capsule has good microbial compatibility, excellent mechanical strength and chemical stability, can be widely applied to various wastewater treatment processes, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection, particularly to the technical fields of sewage treatment and microbial immobilization, and aims to provide a microbial capsule encapsulation technology and its preparation method that can improve sewage treatment efficiency, extend the storage time of microorganisms, and reduce sludge generation. Background Art

[0002] With the acceleration of the global industrialization process and the improvement of urbanization level, the continuous increase in sewage discharge has become one of the urgent problems to be solved in the field of environmental protection. Traditional sewage treatment methods, including the activated sludge method, biofilm method, etc., although achieving sewage purification and treatment to a certain extent, still have many deficiencies. Among them, microbial agents, as the key elements in sewage treatment, their performance directly affects the effect and efficiency of sewage treatment.

[0003] However, the currently widely used microbial agents face many challenges in practical applications. First of all, microbial agents are extremely sensitive to the wastewater environmental conditions. Even minor changes in factors such as temperature, pH value, and dissolved oxygen concentration can significantly affect their activity, resulting in unstable treatment effects. Secondly, microbial agents are easily affected by the external environment during storage and transportation, including light, temperature fluctuations, oxygen contact, etc., thus leading to a decrease or even inactivation of the agent's activity, greatly shortening its effective service life. In addition, the traditional dosing methods of microbial agents often have problems such as agent loss and uneven distribution, making it difficult to form a stable biological community in the sewage treatment system, further affecting the treatment effect.

[0004] To solve the above problems, the microbial immobilization technology has emerged. This technology immobilizes microorganisms inside a carrier through physical or chemical methods to form structures such as microcapsules or biofilms, thereby achieving effective protection and stable control of microorganisms. Among them, the microbial encapsulation technology, as an advanced microbial immobilization means, has the advantages of stable structure, high biological activity, and good storage resistance, showing broad application prospects in the field of sewage treatment.

[0005] However, there are still many deficiencies in the existing microbial encapsulation technology in terms of material selection, preparation process, and actual application effect. Some traditional carrier materials, including sodium alginate and gelatin, although having good biocompatibility, have low mechanical strength and are difficult to maintain a stable structure in a complex sewage treatment environment. At the same time, some preparation processes are complex and costly, which is not conducive to the popularization and application of the technology. In addition, the treatment effect and stability of the microbial capsules in the prior art vary greatly for different types of sewage, making it difficult to meet the diverse sewage treatment requirements.

[0006] In existing sewage treatment processes, especially the activated sludge process, there are problems such as easy loss of microorganisms, difficulty in controlling and optimizing bacterial strains. Summary of the Invention

[0007] The object of the present invention is to propose a microbial solid encapsulation technology, aiming to encapsulate microbial agents of nitrifying bacteria and anaerobic ammonium oxidation bacteria through the combination of polymer materials and porous adsorption materials to form a stable and permeable capsule structure; to achieve efficient immobilization and stable release of microbial agents, improve the sewage treatment effect and stability, and at the same time extend the storage time of microbial agents, providing a new solution for sustainable ecological restoration.

[0008] To achieve the above object, the present invention provides the following technical solution: A microbial capsule for sewage treatment, comprising a capsule shell and a microbial complex inside the capsule shell; the capsule shell is made of a polymer material, and a porous adsorption material such as activated carbon, zeolite powder, graphene oxide, and carbon nanotubes is added to improve the mechanical strength and chemical and microbial stability of the material;

[0009] The microbial complex adsorbs and encapsulates a microbial agent with highly efficient degrading bacteria through the porous adsorption material; the porous adsorption material includes a composite material of activated carbon, graphene oxide, carbon nanotubes, and zeolite, which can effectively adsorb and immobilize the microbial agent.

[0010] A method for preparing the microbial capsule as described above, comprising the following steps:

[0011] (1) Prepare microbial agents, including Bacillus subtilis, nitrifying bacteria, and anaerobic ammonium oxidation bacteria, which are microorganisms important for the biological denitrification process;

[0012] (2) Mix the microbial agent with the porous adsorption material to achieve partial adsorption and immobilization;

[0013] (3) Embed the porous material adsorbed with the microbial agent with a polymer material to form a stable capsule structure; during this process, it should be ensured that the material of the capsule shell has good permeability so that dissolved pollutants and products in the sewage can freely enter and exit;

[0014] (4) Form a gel with mechanical strength through the freeze-thaw method, and then further crosslink and cure with a crosslinking agent, namely saturated boric acid, and stabilizers including sodium sulfate and sodium carbonate to form a microbial capsule with high strength;

[0015] (5) Cut the product into microbial capsules of a predetermined shape and size through a cutting machine.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. Through solid-state encapsulation technology, the present invention encapsulates microorganisms in a polymer material made of polyvinyl alcohol and carbon-based composite materials to form a stable and permeable microbial capsule. The microbial complex inside the capsule enriches microbial agents through a porous adsorbent material and improves the stability and mechanical strength of the capsule with the assistance of activated carbon powder.

[0018] 2. The microbial capsule has excellent stability and mechanical strength, protecting microorganisms from adverse growth conditions; the capsule wall material is permeable, allowing dissolved pollutants and products in sewage to freely enter and exit, achieving efficient and precise microbial enrichment; the encapsulation technology is easily integrated into existing wastewater treatment processes with various configurations. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a graph showing the results of the ammonia nitrogen degradation control experiment for the industrialized fresh water aquaculture sewage treatment of the present invention;

[0020] Figure 2 It is a graph showing the results of the chemical oxygen demand degradation control experiment for the high-concentration organic sewage treatment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] A microbial capsule for sewage treatment and its preparation method, the method comprising the following steps:

[0023] a. Prepare microbial agents of nitrifying bacteria and anaerobic ammonium oxidation bacteria, obtain highly active microbial agents through cultivation and screening, and centrifuge to obtain a high-concentration bacterial suspension.

[0024] b. Prepare porous adsorbent materials of activated carbon and zeolite powder, mix them with the microbial agents and adsorb them to ensure that the microbial agents are effectively adsorbed and fixed by the porous materials.

[0025] c. Prepare a polyvinyl alcohol carrier, and embed the porous materials adsorbed with microbial agents with these polymer materials through conditions. During this process, by controlling the embedding conditions, including temperature and pH value, ensure the permeability and stability of the capsule shell.

[0026] d. Place the prepared microbial capsules into the sewage treatment system and add and adjust them as needed. Since the microbial capsules have excellent mechanical strength, chemical and microbial stability, they can effectively prevent the loss and death of microorganisms, and improve the efficiency and stability of the biological denitrification process. At the same time, due to the solid encapsulation structure of the microbial capsules, they are easy to integrate into existing wastewater treatment processes with various configurations.

[0027] Example 1:

[0028] a. Prepare a polyvinyl alcohol solution: Disperse 10% by mass of polyvinyl alcohol 1799 in water, stir at room temperature for a period of time for swelling, then heat up to 90 °C and continue stirring until the polyvinyl alcohol is completely dissolved to form a homogeneous solution;

[0029] b. Add the carrier and the microbial liquid: After the solution cools to room temperature, add 5% by mass of activated carbon powder and 10% of the microbial suspension, and stir well to mix all components evenly;

[0030] c. Prepare the gel by the freeze-thaw method: Treat the above mixed liquid by the freeze-thaw method, freeze at -18 °C for 24 hours and thaw at room temperature for 10 hours, and repeat 3 cycles to form a gel with mechanical strength;

[0031] d. Crosslinking and stabilization treatment: Place the gel in saturated boric acid for crosslinking reaction for 10 hours, and then soak it in the stabilizer solution, that is, 8% sodium sulfate aqueous solution, for 5 hours to enhance the stability of the gel;

[0032] e. Cutting and shaping: After washing the crosslinked and stabilized gel with deionized water, cut it into cubic small pieces with a side length of 1 cm by a cutting machine.

[0033] Example 2:

[0034] a. Prepare a polyvinyl alcohol solution: Disperse 10% by mass of polyvinyl alcohol 1799 in water, stir at room temperature for a period of time for swelling, then heat up to 90 °C and continue stirring until the polyvinyl alcohol is completely dissolved to form a homogeneous solution;

[0035] b. Add the carrier and the microbial liquid: After the solution cools to room temperature, add 5% by mass of activated carbon powder and 10% of the high-efficiency microbial liquid, and stir well to mix all components evenly;

[0036] c. Prepare the gel by the freeze-thaw method: Treat the above mixed liquid by the one-time freeze-thaw method, freeze at -18 °C for 24 hours and thaw at room temperature for 10 hours to form a gel with mechanical strength;

[0037] d. Crosslinking and stabilization treatment: The gel was placed in saturated boric acid with a pH adjusted to 6.7 for a crosslinking reaction for 10 hours, and then soaked in a stabilizer solution, namely 8% aqueous sodium sulfate solution, for 5 hours to enhance the stability of the gel;

[0038] e. Cutting and shaping: After the crosslinked and stabilized gel was rinsed clean with deionized water, it was cut into cubic small pieces with a side length of 1 cm by a cutting machine.

[0039] Compared with Example 1, the preparation of microbial capsules in Example 2 reduced the number of freezing times, that is, from 3 times to 1 time. At the same time, due to the adjustment of the pH of boric acid, including the comparison of saturated boric acid with a saturated boric acid solution with a pH of 6.7, higher microbial activity can be maintained.

[0040] Examples and data of different sewage treatments

[0041] Example 1: Industrialized fresh water aquaculture sewage treatment

[0042] Test conditions: The aquaculture wastewater from a certain aquaculture base was selected, and the water quality indicators mainly included ammonia nitrogen and nitrate nitrogen. Three groups of tests were set up, namely a blank control experiment, an experiment using traditional free microbial agents, and an experiment using microbial capsules prepared by this method. The microbial agent mainly contained nitrifying bacteria and denitrifying bacteria.

[0043] Test results: After comparison, the system treated with microbial capsules showed a significantly improved treatment effect on ammonia nitrogen. Specifically, on the 3rd day, the degradation efficiency of ammonia nitrogen in the microbial capsule group reached 92%, far higher than 71% in the free bacteria group. On the 5th day, it reached 98%, higher than 86% in the free bacteria group, as Figure 1 shown.

[0044] Example 2: High-concentration organic sewage

[0045] Test conditions: A certain preserved fruit wastewater was selected as the test object. This wastewater contained a large amount of organic matter, and the chemical oxygen demand, that is, COD reached 1079.4 mg / L, and the sewage was strongly acidic with a pH of 5.6. Three groups of tests were set up, namely a blank control experiment, an experiment using traditional free microbial agents, and an experiment using microbial capsules prepared by this method. The microbial agent was mainly Bacillus subtilis and anaerobic ammonia-oxidizing bacteria.

[0046] Test results: In the comparative test, for the treatment of high-concentration organic wastewater, the microbial capsule technology is significantly superior to the traditional microbial inoculant method. Among them, the degradation of chemical oxygen demand in the group added with free inoculant showed an unstable state, first decreasing slowly and then increasing, because the survival rate of free bacteria in a strong acidic system is relatively low, resulting in poor degradation effect. However, due to the protective effect on cells, the microbial capsule has significantly improved tolerance to this acidic environment, and its degradation efficiency of chemical oxygen demand reached 90% on the 5th day, significantly higher than the traditional inoculant method, as Figure 2 shown.

[0047] In summary, the microbial capsule technology and its preparation method proposed by the present invention have broad application prospects and important practical values in the field of wastewater treatment. By optimizing the preparation process and carrier selection, efficient immobilization of microorganisms is achieved, improving the efficiency and effect of wastewater treatment.

[0048] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0049] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A microbial capsule for sewage treatment, characterized in that, The capsule consists of the following two parts: a. The capsule shell is made of 10% by mass fraction of polyvinyl alcohol 1799, 5% activated carbon powder and zeolite powder adsorption material; b. Different types of commonly used microbial agents for sewage treatment, including Bacillus subtilis, nitrifying / denitrifying bacteria, with a mass fraction of 10%.

2. A preparation method of a microbial capsule for sewage treatment, based on the microbial capsule for sewage treatment described in claim 1, characterized in that, It includes the following steps: S1. Prepare the polyvinyl alcohol solution: Disperse 10% by mass fraction of polyvinyl alcohol 1799 into water, stir for a period of time at room temperature for swelling, then heat up to 90 °C and continue stirring until the polyvinyl alcohol is completely dissolved to form a homogeneous solution; S2. Add the adsorbent and microbial bacterial liquid: After the solution cools to room temperature, add 5% activated carbon powder and zeolite powder and 10% microbial bacterial suspension, and stir well to make each component evenly mixed; S3. Prepare the gel by the freeze-thaw method: Treat the above mixed liquid by the freeze-thaw method to form a gel with mechanical strength; S4. Crosslinking and stabilization treatment: Place the gel in a crosslinking agent solution of saturated boric acid for crosslinking reaction, and then soak it in a stabilizer solution, including an aqueous solution of sodium sulfate and sodium carbonate, to enhance the stability of the gel; S5. Cutting and shaping: After washing the crosslinked and stabilized gel with water, cut it into microbial capsules with a predetermined shape and size.

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