In-situ control covering material for lake polluted bottom mud and preparation method thereof

Abstract

The invention provides a lake sediment in-situ control covering material and a preparation method thereof, and belongs to the technical field of water treatment, the covering material provided by the invention has extremely strong reduction ability to various pollutants in a water body, can effectively improve the quality of the water body, enables the water body to be converted to a healthy and clean state, and has a good application prospect. A good water body environment is created for survival and reproduction of aquatic organisms in a water ecosystem, and restoration and improvement of lake ecological functions are facilitated. The bottom mud covering material disclosed by the invention can practically act on bottom mud to successfully inhibit release of pollutants to a water body, so that endogenous diffusion pollution of lakes can be effectively reduced, and habitat conditions are provided for ecological restoration; the method has important application significance in the aspects of maintaining the balance and stability of the whole lake ecological system, restoring the ecological landscape of the lake, guaranteeing the ecological safety of surrounding areas and the like, and an effective new thought and a new method are provided for lake pollution treatment and ecological restoration.

Description

Technical Field

[0001] The invention relates to the technical field of water pollution remediation, and in particular to an in-situ controlled covering material for lake polluted sediment and a preparation method thereof. Background Art

[0002] With the acceleration of global industrialization and urbanization and the increasing frequency of agricultural production activities, pollution sources such as industrial wastewater, farmland runoff and urban domestic sewage are continuously discharged into rivers and eventually accumulated in lakes and reservoirs. Damage to the health of lake water environment often presents phenomena such as reduced water transparency, excessive algae reproduction and deterioration of water quality, which seriously affects the ecological function of lakes and surrounding landscapes. For example, the explosive growth of algae will form thick algae blooms on the water surface, which not only hinders sunlight from penetrating the water body and affects the photosynthesis of underwater plants, but also decomposes and consumes a large amount of oxygen in the water after death, causing hypoxia in the water body, which in turn leads to the death of a large number of aquatic organisms, destroying the balance of the lake ecosystem, reducing the deep diversity and stability of aquatic organisms, and the deteriorated water quality cannot meet people's needs for viewing, irrigation, drinking, fishery and other aspects of lake water.

[0003] As the "source" and "sink" of pollutants, lake sediments play a key role in the circulation and evolution of lake materials. For a long time, some of the nutrients such as nitrogen and phosphorus and heavy metal pollutants that enter the lake will settle to the bottom of the lake through physical, chemical and biological effects, and continue to accumulate in the sediments. However, the sediment is not a simple place for pollutants to accumulate. There is a complex material exchange process between it and the overlying water body. Under specific environmental conditions, such as temperature, water flow, microbial activity and other factors, the nutrients and heavy metals in the sediment will be released back into the water body, becoming an important endogenous pollution for the eutrophication of lake water bodies, and continuously providing nutrients for the growth of algae and other plankton, further aggravating the degree of lake pollution, making lake management work face great challenges. It is often difficult to fundamentally solve the problem of lake water ecological restoration by relying solely on the control of exogenous pollution to reduce the impact of lake pollution. At the same time, it is necessary to pay attention to the management of endogenous pollution such as sediments.

[0004] At present, the technical means for the treatment of polluted lake sediments mainly include physical dredging, chemical remediation and bioremediation, but all of them have certain limitations: although mechanical excavation and other methods can directly remove a large number of pollutants, the engineering workload is huge and the cost is high. In addition, the dredging process is likely to cause serious damage to the benthic ecological environment of the lake. At the same time, the subsequent disposal of sediments is also a thorny issue. If it is not handled properly, it may also lead to secondary pollution. Chemical agents are used to react chemically with pollutants in the sediments, such as adding lime and other substances to fix heavy metals in the sediments or control the release of phosphorus. However, excessive use of chemical agents may change the chemical properties of the water body such as pH, and have a toxic effect on aquatic organisms. Moreover, the remediation effect is often difficult to last, and pollutants may be released again over time. With the help of biological means such as microorganisms and aquatic plants to degrade or absorb pollutants in the sediments, the bioremediation process is usually slow and has strict requirements on environmental conditions. For example, the growth and reproduction of microorganisms requires suitable temperature, nutrients and other conditions. When facing heavily polluted sediments, biological remediation alone is often difficult to quickly and effectively achieve sediment purification and eutrophication control.

[0005] In view of the many shortcomings of existing treatment technologies, it is particularly urgent to develop an efficient, economical and environmentally friendly in-situ control technology for lake polluted sediments. In-situ control technology can directly act on polluted sediments without destroying the benthic ecological environment of the lake, effectively inhibit the release of pollutants in the sediments into the water body, reduce endogenous pollution from the source, and combine multiple repair mechanisms to synergistically accelerate the purification process of sediments, thereby achieving the goal of reducing the degree of eutrophication of lakes, improving lake water quality and restoring the functions of lake ecosystems. This has great practical significance for the protection of lake water ecological environment and sustainable development.

[0006] In summary, in order to better deal with the problem of lake ecological restoration and overcome the limitations of existing sediment management technologies, an innovative in-situ control technology for lake polluted sediments is developed, namely, the technical solution of combining aluminum-based composite materials with microbial agents involved in the present invention, which has important research value and application prospects. Summary of the invention

[0007] The purpose of the present invention is to provide an in-situ controlled covering material for lake polluted sediment and a preparation method thereof, which can effectively reduce endogenous diffuse pollution in lakes and provide ideal habitat conditions for water ecological restoration.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides an in-situ controlled covering material for lake polluted sediment, comprising an aluminum-based composite material and a microbial agent;

[0010] The microbial agent contains nitrifying bacteria, Pseudomonas mendocinae and Bacillus subtilis.

[0011] Preferably, the ratio of nitrifying bacteria, Pseudomonas mendocina and Bacillus subtilis in the microbial agent is 1:1.5-2.5:0.5-1.5.

[0012] Preferably, the method comprises the following steps:

[0013] Mixing activated alumina powder, bentonite, diatomaceous earth, polyethylene glycol and sodium carboxymethyl cellulose to obtain a muddy material;

[0014] The mud-like material is subjected to extrusion molding, drying treatment and sintering treatment to obtain an aluminum-based composite material.

[0015] Preferably, the method comprises the following steps:

[0016] The bacterial liquids of nitrifying bacteria, Pseudomonas mendocinae and Bacillus subtilis are mixed, fixed and embedded to obtain a microbial agent.

[0017] Preferably, the diatomaceous earth is calcined at 600-800° C. for 2-3 hours before mixing.

[0018] Preferably, the mass ratio of the activated alumina powder: bentonite: diatomaceous earth is 4.5-5.5:2.5-3.5:1.5-2.5.

[0019] Preferably, the amount of polyethylene glycol used is 0.5-2% of the total mass of the raw materials;

[0020] The amount of sodium carboxymethyl cellulose used is 0.3-1% of the total mass of the raw materials.

[0021] Preferably, the sintering treatment is carried out at a temperature of 300 to 500° C. and for a time of 2 to 3 hours.

[0022] Preferably, the diameter of the material particles after extrusion molding is 1 to 3 cm and the length is 4 to 6 cm;

[0023] The amount of aluminum-based composite material added is 5-20 kg / m 2 .

[0024] Preferably, the fixed embedding adopts the sodium alginate-calcium chloride embedding method, and the diameter of the material after fixed embedding is 2 to 3 mm;

[0025] The amount of microbial agent added is 100 to 300 particles / m 2 .

[0026] Technical effects and advantages of the present invention:

[0027] The beneficial effect of the present invention is that remarkable results have been achieved after in-situ covering treatment of lake polluted sediments by using a scheme combining aluminum-based composite materials and microbial agents. In terms of water bodies, the total nitrogen, total phosphorus, ammonia nitrogen and heavy metal contents in the water bodies of the treatment area have shown a significant downward trend over time, which fully demonstrates that the materials and microbial agents provided by the present invention work together to have a strong ability to reduce various pollutants in the water body, and can effectively improve the water quality, transform it into a healthy and clean state, create a good water environment for the survival and reproduction of aquatic organisms in the water ecosystem, and help restore and enhance the ecological functions of the lake. At the sediment level, the total nitrogen, total phosphorus, heavy metal content and organic matter content in the treatment area will continue to decrease over time, which means that the content of nutrients and pollutants in the sediment is continuously decreasing, and the sediment environment has been effectively improved.

[0028] The sediment covering material of the present invention can effectively act on the polluted sediment, successfully inhibit the release of pollutants into the water body, and then inhibit the resuspension of the lake sediment, and prevent the risk of upward exchange of soluble nutrients. It has important application significance for maintaining the balance and stability of the entire lake ecosystem, restoring the healthy cycle of the lake's water ecology, and ensuring the ecological security of the surrounding areas. It provides an effective new idea and method for lake ecological restoration. DETAILED DESCRIPTION

[0029] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0030] Example 1

[0031] Prepare the ingredients:

[0032] Activated alumina powder: Activated alumina powder with a particle size of 200 mesh and a purity of 99.99% is selected as the main aluminum source of the aluminum-based composite material.

[0033] Bentonite: Select sodium bentonite with a montmorillonite content of more than 80% (the montmorillonite content of the Ayong product in this embodiment is 90%), and grind it and pass it through a 200-mesh sieve.

[0034] Diatomaceous earth: Select high-quality diatomaceous earth, calcine it at 700℃ for 2.5h, and then crush it through a 150-mesh sieve.

[0035] Additives: polyethylene glycol (PEG-4000) as a dispersant, sodium carboxymethyl cellulose (CMC) as a thickener and stabilizer.

[0036] Premixing: Weigh the raw materials according to the mass ratio of activated alumina powder: bentonite: diatomaceous earth = 5:3:2, put them into a high-speed mixer, add 1% polyethylene glycol (PEG-4000) of the total mass of the raw materials, stir at a speed of 800r / min for 20 minutes to fully mix the raw materials to obtain a premix.

[0037] Kneading: slowly add an appropriate amount of deionized water to the premix, and at the same time add 0.5% of sodium carboxymethyl cellulose (CMC) accounting for the total weight of the raw materials, and continue to stir and knead until a muddy material with a certain plasticity, uniform humidity and no obvious particle agglomeration is formed.

[0038] Molding: The kneaded mud material is extruded into a cylindrical shape (2 cm in diameter and 5 cm in length) through an extruder to facilitate subsequent placement and covering operations.

[0039] Drying and sintering: Place the formed material in a ventilated drying oven and dry it at 60°C for 12 hours to remove moisture. Then transfer the dried material to a muffle furnace, heat it to 400°C at a heating rate of 5°C / min, and sinter it at this temperature for 3 hours to make the raw materials closely bonded, improve the strength and stability of the composite material, and finally obtain the finished aluminum-based composite material.

[0040] Preparation of microbial inoculants

[0041] The nitrifying bacteria (purchased from Beijing Bio-Bowei Biotechnology Co., Ltd., Bio-74091, Nitrobacter Sp.): Pseudomonas mendocina (purchased from China General Microbiological Culture Collection Center, CGMCC 1.8049, Pseudomonas mendocina): Bacillus subtilis (purchased from China General Microbiological Culture Collection Center, CGMCC 1.8801, Bacillus filamentosus) = 1:2:1 (volume ratio, the concentration of live bacteria is 10 8 CFU / mL) to obtain a mixed microbial culture liquid. In order to improve the survival rate and stability of microorganisms in the lake sediment environment, the sodium alginate-calcium chloride embedding method was used to immobilize the microbial culture liquid. The specific operation is as follows: the microbial culture liquid is evenly mixed with a certain concentration (2%) of sodium alginate solution in a volume ratio of 1:1, and then slowly dripped into a 2% calcium chloride solution through a syringe to form a gel ball with a diameter of about 2.5mm, which is allowed to solidify in the calcium chloride solution for 1 hour, and then taken out and rinsed with physiological saline 2-3 times to obtain an immobilized microbial agent.

[0042] Applied to in-situ covering of polluted lake sediments

[0043] Preparation before launching

[0044] Sediment pretreatment: The polluted lake sediment to be treated is simply leveled to remove large debris and garbage on the surface, so that the sediment surface is relatively flat, which is convenient for the uniform laying of subsequent covering materials.

[0045] Placement planning: According to the area, shape and pollution level of the lake, the placement area and amount of aluminum-based composite materials and microbial agents should be reasonably planned. Generally speaking, for areas with heavy pollution, the placement density should be appropriately increased. A preliminary estimate can be made based on the standard of 10kg of aluminum-based composite materials (thickness can reach about 5cm) and 200 microbial agent gel balls per square meter, and then fine-tuned according to the actual situation.

[0046] Delivery Operation

[0047] Placement of aluminum-based composite materials: Use manual or mechanical spreading to evenly cover the surface of the lake sediment with the prepared aluminum-based composite materials, and try to ensure that the coverage thickness is about 5 cm, to form a physical barrier layer. Use its adsorption properties to adsorb and fix the nitrogen, phosphorus and heavy metals released from the sediment to prevent them from further spreading into the water.

[0048] Placement of microbial agents: After the aluminum-based composite material is covered, the immobilized microbial agent gel balls are evenly spread on its surface according to the planned placement amount. The microbial agents will utilize the attachment sites provided by the aluminum-based composite material and their own metabolic activities to degrade and transform the nitrogen and phosphorus adsorbed on the composite material and in the surrounding water and sediment, and stabilize the heavy metals.

[0049] Example 2

[0050] Prepare the ingredients:

[0051] Activated alumina powder: Activated alumina powder with a particle size of 200 mesh and a purity of 99.99% is selected as the main aluminum source of the aluminum-based composite material.

[0052] Bentonite: Select sodium bentonite with a montmorillonite content of more than 80% (the montmorillonite content of the Ayong product in this embodiment is 90%), and grind it and pass it through a 200-mesh sieve.

[0053] Diatomaceous earth: Select high-quality diatomaceous earth, calcine it at 700℃ for 3h, and then crush it through a 150-mesh sieve.

[0054] Additives: polyethylene glycol (PEG-4000) as a dispersant, sodium carboxymethyl cellulose (CMC) as a thickener and stabilizer.

[0055] Premixing: Weigh the raw materials according to the mass ratio of activated alumina powder: bentonite: diatomaceous earth = 6:3:2, put them into a high-speed mixer, add 1% polyethylene glycol (PEG-4000) of the total mass of the raw materials, stir at a speed of 800r / min for 20 minutes to fully mix the raw materials to obtain a premix.

[0056] Kneading: slowly add an appropriate amount of deionized water to the premix, and at the same time add 0.5% of sodium carboxymethyl cellulose (CMC) accounting for the total weight of the raw materials, and continue to stir and knead until a muddy material with a certain plasticity, uniform humidity and no obvious particle agglomeration is formed.

[0057] Molding: The kneaded mud material is extruded into a cylindrical shape (2 cm in diameter and 5 cm in length) through an extruder to facilitate subsequent placement and covering operations.

[0058] Drying and sintering: Place the formed material in a ventilated drying oven and dry it at 60°C for 12 hours to remove moisture. Then transfer the dried material to a muffle furnace, heat it to 400°C at a heating rate of 5°C / min, and sinter it at this temperature for 3 hours to make the raw materials closely bonded, improve the strength and stability of the composite material, and finally obtain the finished aluminum-based composite material.

[0059] Preparation of microbial inoculants

[0060] The nitrifying bacteria (purchased from Beijing Bio-Bowei Biotechnology Co., Ltd., Bio-74091, Nitrobacter Sp.): Pseudomonas mendocina (purchased from China General Microbiological Culture Collection Center, CGMCC 1.8049, Pseudomonas mendocina): Bacillus subtilis (purchased from China General Microbiological Culture Collection Center, CGMCC 1.8801, Bacillus filamentosus) = 1:2:2 (volume ratio, the concentration of live bacteria is 10 8 CFU / mL) to obtain a mixed microbial culture liquid. In order to improve the survival rate and stability of microorganisms in the sediment environment of lake water bodies, the sodium alginate-calcium chloride embedding method is used to immobilize the microbial culture liquid. The specific operation is as follows: the microbial culture liquid is mixed evenly with a certain concentration (2%) of sodium alginate solution in a volume ratio of 1:1, and then slowly dripped into a 2% calcium chloride solution through a syringe to form a gel ball with a diameter of about 2.5mm, which is allowed to solidify in the calcium chloride solution for 1 hour, and then taken out and rinsed with physiological saline 2-3 times to obtain an immobilized microbial agent.

[0061] Applied to in-situ covering of lake water sediment

[0062] Preparation before launching

[0063] Sediment pretreatment: The polluted lake sediment to be treated is simply leveled to remove large debris and garbage on the surface, so that the sediment surface is relatively flat, which is convenient for the uniform laying of subsequent covering materials.

[0064] Placement planning: According to the area, shape and pollution level of the lake, the placement area and amount of aluminum-based composite materials and microbial agents should be reasonably planned. Generally speaking, for areas with heavy pollution, the placement density should be appropriately increased. A preliminary estimate can be made based on the standard of 10kg of aluminum-based composite materials and 200 microbial agent gel balls per square meter, and then fine-tuned according to the actual situation.

[0065] Delivery Operation

[0066] Placement of aluminum-based composite materials: Use manual or mechanical spreading to evenly cover the surface of the lake sediment with the prepared aluminum-based composite materials, and try to ensure that the coverage thickness is about 5 cm, to form a physical barrier layer. Use its adsorption properties to adsorb and fix the nitrogen, phosphorus and heavy metals released from the sediment to prevent them from further spreading into the water.

[0067] Placement of microbial agents: After the aluminum-based composite material is covered, the immobilized microbial agent gel balls are evenly spread on its surface according to the planned placement amount. The microbial agents will utilize the attachment sites provided by the aluminum-based composite material and their own metabolic activities to degrade and transform the nitrogen and phosphorus adsorbed on the composite material and in the surrounding water and sediment, and stabilize the heavy metals.

[0068] Experimental example

[0069] A lake with typical eutrophication and moderate area (about 5,000 square meters) was selected as the experimental site, and the lake was divided into three areas:

[0070] Treatment area: According to the technical solution described in Example 1, aluminum-based composite materials and microbial agents are placed to carry out in-situ covering treatment of the bottom mud.

[0071] Control area 1 (covering material only): an equal amount of aluminum-based composite materials was added, but no microbial agents were added. Other conditions were kept consistent with the treatment area, for comparative analysis of the effects of the microbial agents.

[0072] Control area 2 (blank control): No treatment is done, and it is kept in its natural state as a control reference for the original pollution situation.

[0073] Detection indicators and methods

[0074] (I) Water body detection indicators and methods

[0075] Total Nitrogen (TN):

[0076] Detection method: Alkaline potassium persulfate digestion-ultraviolet spectrophotometry. After collecting the water sample, add alkaline potassium persulfate solution and digest it under high temperature and high pressure to convert the nitrogen-containing compounds in the water sample into nitrates. After cooling, measure the absorbance at wavelengths of 220nm and 275nm on an ultraviolet spectrophotometer, and calculate the total nitrogen content based on the standard curve.

[0077] Testing frequency: Testing should be carried out before treatment and in the first week, second week, first month, third month and sixth month after treatment. Three parallel water samples should be collected each time and the average value should be taken.

[0078] Total Phosphorus (TP):

[0079] Detection method: ammonium molybdate spectrophotometry is used. After the water sample is digested, under acidic conditions, orthophosphate reacts with ammonium molybdate to form phosphomolybdic heteropoly acid, which is then reduced by ascorbic acid to form a blue complex. The absorbance is measured at a wavelength of 700nm on a spectrophotometer, and the total phosphorus content is obtained by comparing with the standard curve.

[0080] Detection frequency: Same as total nitrogen detection frequency, collect 3 parallel water samples each time and take the average value.

[0081] Ammonia nitrogen (NH3-N):

[0082] Detection method: Nessler's reagent spectrophotometry is used. Nessler's reagent is added to the water sample to react with ammonia nitrogen to form a light reddish brown complex. The absorbance is measured at a wavelength of 420nm, and the ammonia nitrogen content is calculated using the standard curve.

[0083] Detection frequency: Same as total nitrogen detection frequency, collect 3 parallel water samples each time and take the average value.

[0084] Heavy metals [select copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb)]:

[0085] Detection method: Inductively coupled plasma mass spectrometry (ICP-MS) is used. After appropriate acidification pretreatment, the collected water samples are directly injected into the inductively coupled plasma mass spectrometer to determine the content of each heavy metal element.

[0086] Testing frequency: Testing should be carried out before treatment and in the first, third and sixth months after treatment. Three parallel water samples should be collected each time and the average value should be taken.

[0087] (II) Sediment detection indicators and methods

[0088] Total nitrogen (TN), total phosphorus (TP)

[0089] Detection method: The total nitrogen content is determined by the Kjeldahl method. The sediment sample is heated with concentrated sulfuric acid and a catalyst to convert the organic nitrogen into ammonium nitrogen, and the nitrogen content is then determined by distillation, titration and other steps. The total phosphorus is determined by the acid dissolution-ammonium molybdate spectrophotometry method. The sediment sample is digested with an acid solution, and the subsequent operation is the same as the total phosphorus detection method for water bodies to determine the phosphorus content.

[0090] Testing frequency: Collect sediment samples for testing before treatment and in the first, third and sixth months after treatment. Each time, three parallel samples are collected and part of them are taken for analysis after mixing.

[0091] Heavy metals, detection of copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb):

[0092] Detection method: microwave digestion-atomic absorption spectrometry (AAS) or inductively coupled plasma emission spectrometry (ICP-AES). First, the sediment sample is subjected to microwave digestion treatment to convert the heavy metals in the sample into ions, and then the appropriate method is selected according to the specific instrument for detection, such as atomic absorption spectrometry or inductively coupled plasma emission spectrometry to determine the content of each heavy metal element.

[0093] Detection frequency: Same as the detection frequency of total nitrogen and total phosphorus in sediments. Collect 3 parallel samples each time and mix them before taking part for analysis.

[0094] Detection of organic matter content in sediment to characterize eutrophication:

[0095] The potassium dichromate volumetric method-external heating method is used. In the presence of concentrated sulfuric acid, an excess of potassium dichromate solution is used to oxidize the organic matter in the sediment, and the remaining potassium dichromate is titrated with a standard ferrous sulfate solution. The organic matter content is calculated based on the amount of ferrous sulfate consumed.

[0096] Testing frequency: Testing should be carried out before treatment and in the first, third and sixth months after treatment, with multiple measurements taken at different locations each time to take the average value.

[0097] The test results are as follows:

[0098] Table 1 Water body test results

[0099]

[0100]

[0101] It can be seen from the above data that the total nitrogen, total phosphorus, ammonia nitrogen and heavy metal contents in the water of the treatment area showed a significant downward trend over time, and were significantly reduced compared with control area 1 and control area 2 in each detection time period (verified by variance analysis, P<0.05), indicating that the aluminum-based composite material provided by the present invention and the microbial agent have a significant effect on reducing pollutants in water.

[0102] Table 2 Sediment detection results

[0103]

[0104]

[0105] The sediment test data showed that the total nitrogen, total phosphorus, heavy metal content and organic matter content in the treatment area continued to decrease over time, indicating that the nutrients and pollutants in the sediment were decreasing and the sediment environment was improving, while the changes in control area 1 and control area 2 were relatively small. This further proves that the sediment covering material and bacterial agent scheme of the present invention can effectively act on the sediment, reduce the release of pollutants into the water body, and achieve the beneficial effect of reducing lake eutrophication.

[0106] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A lake sediment in-situ controlled covering material, characterized in that: Including aluminum-based composite materials and microbial agents; The microbial agent contains nitrifying bacteria, Pseudomonas mendocinae and Bacillus subtilis.

2. The lake sediment in-situ controlled covering material according to claim 1, characterized in that: The ratio of nitrifying bacteria, Pseudomonas mendocinae and Bacillus subtilis in the microbial agent is 1:1.5-2.5:0.5-1.

5.

3. The method for preparing the lake sediment in-situ controlled covering material according to claim 1 or 2, characterized in that: The following steps are involved: Mixing activated alumina powder, bentonite, diatomaceous earth, polyethylene glycol and sodium carboxymethyl cellulose to obtain a muddy material; The mud-like material is subjected to extrusion molding, drying treatment and sintering treatment to obtain an aluminum-based composite material.

4. The method for preparing the lake sediment in-situ controlled covering material according to claim 1 or 2, characterized in that: The following steps are involved: The bacterial liquids of nitrifying bacteria, Pseudomonas mendocinae and Bacillus subtilis are mixed, fixed and embedded to obtain a microbial agent.

5. The preparation method according to claim 3, characterized in that: The diatomaceous earth is calcined at a high temperature of 600 to 800° C. for 2 to 3 hours before mixing.

6. The preparation method according to claim 3, characterized in that: The mass ratio of the activated alumina powder: bentonite: diatomaceous earth is 4.5-5.5: 2.5-3.5: 1.5-2.

5.

7. The preparation method according to claim 6, characterized in that: The amount of polyethylene glycol used is 0.5-2% of the total mass of the raw materials; The amount of sodium carboxymethyl cellulose used is 0.3-1% of the total mass of the raw materials.

8. The preparation method according to claim 7, characterized in that: The sintering process is carried out at a temperature of 300 to 500° C. and for a time of 2 to 3 hours.

9. The preparation method according to claim 3, characterized in that: The diameter of the material particles after extrusion molding is 1 to 3 cm and the length is 4 to 6 cm; The amount of aluminum-based composite material added is 5-20 kg / m 2 .

10. The preparation method according to claim 4, characterized in that: The fixed embedding adopts the sodium alginate-calcium chloride embedding method, and the diameter of the material after fixed embedding is 2 to 3 mm; The amount of microbial agent added is 100 to 300 particles / m 2 .

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