Process method for eluting and removing granular nutritive salt in water body

Abstract

The invention belongs to the technical field of environmental governance, and particularly relates to a process method for eluting and removing granular nutritive salt in a water body. Comprising the following steps: S1, deeply plowing and stirring bottom mud under the action of mechanical force, air flow or water flow, so that pollutants in the bottom mud are released and dissolved in water, and cleaned large-particle-state silt is precipitated; and S2, pumping a mud-water mixture obtained by elution into a sewage / water separation tank, adding a modified biological flocculant and an auxiliary agent, carrying out mechanical stirring, coagulating and precipitating pollutants in the sewage / water separation tank, returning clean water to a water body, and treating the precipitated sludge in an elution sludge treatment unit. The invention provides a process method for eluting and removing granular nutritive salts in a water body, which can effectively remove the nutritive salts, control endogenous pollution by transferring small particulate matters, remarkably increase the volume weight of bottom mud on the surface layer, improve the anti-disturbance capability of the bottom mud and facilitate the construction of a stable mud-water interface.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental governance, and in particular relates to a process for eluting and removing particulate nutrient salts in water. Background Art

[0002] As an important component of river and lake ecosystems, sediments are the main recipients of water pollutants, especially nutrients. The long-term evolution of river and lake environments is often inseparable from the circulation of nutrients, so most rivers and lakes have high background values ​​of nutrients. The exchange and circulation of nutrients between the mud and water interface is one of the leading factors causing eutrophication of water bodies, and endogenous pollution of sediments plays an important role in deepening the eutrophication of rivers and lakes. The negative impact of endogenous pollutants in the water environment has become a link that must be paid attention to in the management of rivers and lakes.

[0003] Due to the historical contribution of endogenous pollution in sediment, it directly reflects the pollution history of water bodies to a certain extent. As a potential secondary pollution of the water environment, sediment can transfer substances with overlying water in various ways. The frequent exchange of nutrients at the sediment-water interface provides the basis for the surge in algae and plankton, which greatly hinders the reconstruction and recovery of underwater vegetation.

[0004] Therefore, effective control of endogenous pollution is of great significance to the restoration of the ecological environment of rivers and lakes.

[0005] The control of endogenous pollution of sediment can be achieved by removing and degrading pollutants and preventing their release into the overlying water. Conventional technologies such as environmental dredging of sediment, in-situ covering, and in-situ fixation technology all show certain effects in preventing the release of nitrogen and phosphorus substances. Among them, environmental dredging technology of sediment can reduce the endogenous load and reduce the release of nutrients by dredging the upper nutrient-rich sediment to an off-site treatment. However, there is controversy over the long-term inhibitory effect of dredging on the release of nitrogen and phosphorus, and the long-term effect of dredging technology on phosphorus release is still worth discussing. In-situ covering technology blocks the release of nitrogen and phosphorus by laying materials on the surface of the sediment. Specific covering materials and covering thickness can be selected according to the different pollutants blocked. In-situ fixation technology fixes pollutants in sediments by adding chemicals to the polluted water body to prevent their release into the overlying water. However, both covering and fixation technologies introduce new pollutants into the water body, which is still not conducive to the healthy development of the aquatic ecosystem. Under the existing technical conditions, it is still of practical significance to find new remediation technologies.

[0006] In recent years, the in-situ elution technology that has emerged in China has achieved good results in the sediment remediation project of the Jiugong section of Liangshui River in Beijing. This technology physically, mechanically or aeratedly agitates the surface polluted sediment, so that the pollutants enter the water phase and are pumped away for subsequent treatment. At the same time, the washed clean sediment is agitated and re-covered to form a new cover layer. Therefore, this technology has some characteristics similar to dredging technology to separate some pollutants and covering technology, which may have a certain inhibitory effect on the release of nitrogen and phosphorus in the sediment. Sediment resuspension has a huge impact on the overlying water environment and the growth of submerged plants. As a hydrodynamic process, sediment resuspension is accompanied by changes in physical and chemical conditions, which in turn affect the water environment. The aquatic ecosystem cannot effectively self-regulate, forming a vicious circle.

[0007] Based on this, we proposed a process for eluting and removing particulate nutrients in water, hoping to solve the shortcomings of the existing technology and provide a theoretical basis and preliminary reference for eluting and removing nutrients in water. Summary of the invention

[0008] The purpose of the present invention is to provide a process for eluting and removing particulate nutrient salts in water in view of the existing problems.

[0009] The present invention is achieved through the following technical solutions: A process for removing particulate nutrients from water, comprising the following steps: S1. Deeply plow and stir the bottom mud to achieve desorption and phase separation of pollutants, so that adsorbed pollutants in the bottom mud migrate to the water phase and dissolve, while the washed large-particle mud settles under the action of gravity; S2. Pump the eluted mud-water mixture into a sewage / water separation tank, add modified bioflocculant and additives for mechanical stirring, coagulate and precipitate pollutants in the sewage / water separation tank, return clean water to the water body, and the precipitated sludge enters the elution sludge treatment unit for treatment; The preparation of the modified bioflocculant comprises the following steps: (1) Cu2O, ZnCl2 and CeCl3 were added to an ethanol aqueous solution in the ratio of 10-12:7-9:1 in sequence. After being uniformly dispersed by ultrasonication, polyvinyl pyrrolidone was added. After stirring at 200-300 rpm for 20-30 min, Na2S2O3 solution was added dropwise at 100-200 rpm under room temperature. After the addition was completed, stirring was continued for 2-3 h. The mixture was filtered, washed with deionized water and anhydrous ethanol in sequence, and dried in a vacuum drying oven to constant weight. The mixture was then placed in a muffle furnace and calcined to obtain Ce-ZnO powder for later use. (2) Dissolve chitosan in 1% glacial acetic acid, disperse it ultrasonically at room temperature for 20-30 minutes, then add the silk fibroin solution, stir it at 300-400 rpm for 10-15 minutes, let it stand for 1-2 hours, then heat it to 80-90°C, add D,L-lactide, stir it at 200-300 rpm for 2-3 hours, add stannous octoate, react it at 200-300 rpm and 100-110°C for 20-30 hours, stop heating, add methanol / acetic acid solution with a volume ratio of 8:1, react it at 200-300 rpm for 40-60 minutes, cool it naturally to room temperature, and perform ultrafiltration, washing and drying in sequence to obtain a modified silk fibroin / chitosan complex; (3) The Ce-ZnO powder obtained in step (1) and the modified silk fibroin / chitosan complex obtained in step (2) are ultrasonically dispersed in sterile water in a mass ratio of 1:1-2, and after being evenly dispersed, the culture medium is added, and after being fully mixed, the Bacillus cereus strain is added, and then the mixture is placed in a constant temperature shaker for shaking and culture, and then transferred to a centrifuge for centrifugation at 5000-6000 rpm for 10-20 min. The supernatant is taken, and 3 times the volume of pre-cooled ethanol is added to the supernatant. The resulting mixture is placed in a refrigerator at 4°C for 40-72 h, and then placed in a centrifuge for centrifugation at 10000-12000 rpm for 10-12 min. The precipitate is collected and freeze-dried.

[0010] Further preferably, the concentration of the modified bioflocculant in step S2 is 40-60 mg / L.

[0011] Further preferably, the deep plowing and stirring of the bottom mud in step (1) is carried out under the action of mechanical force, air flow or water flow.

[0012] Further preferably, the concentration of the ethanol aqueous solution in step (1) is 50%; The mass volume ratio of CeCl3 to ethanol aqueous solution is 1 mg: 15-20 mL; The weight of the polyvinyl pyrrolidone is 0.25 to 0.35 times that of CeCl3; The concentration of the Na2S2O3 solution is 1 mol / L, and the amount added is 0.3 to 0.4 times that of the ethanol aqueous solution.

[0013] Further preferably, the number of deionized water washing in step (1) is 2 to 3 times, and the number of anhydrous ethanol washing is 2 to 3 times; The drying temperature in the vacuum drying oven is controlled to be 50-60°C; During the calcination, the calcination temperature is controlled to be 400-500° C. and the calcination time is 2-3 hours.

[0014] Further preferably, the mass volume ratio of chitosan to glacial acetic acid in step (2) is 1 mg: 8-12 mL; The mass fraction ratio of silk fibroin to chitosan in the mixed solution after adding the silk fibroin solution is 1:2-4; The mass of the D,L-lactide is 4 to 5 times that of chitosan; The mass of stannous octoate is 0.23 to 0.25 times that of chitosan; The mass of the methanol / acetic acid solution is 0.4 to 0.45 times that of chitosan.

[0015] Further preferably, the modified silk fibroin / chitosan complex is obtained by ultrafiltration, washing and drying in sequence as described in step (2): ultrafiltration is performed using a hollow fiber membrane with a pore size of 1000Da, the membrane is washed 3 to 5 times with anhydrous ethanol, and then placed in a vacuum drying oven, and dried to constant weight at 50 to 60°C to obtain a modified silk fibroin / chitosan complex.

[0016] Further preferably, the components and concentrations of the culture medium in step (3) are: yeast extract 5 g / L, peptone 2 g / L, mannitol 30 g / L, K2HPO4 0.7 g / L; The shaking culture temperature is 35-36°C, the shaking speed of the shaker is 120-200 rpm, and the culture is carried out for 1-2 days.

[0017] Further preferably, the components and corresponding weight percentages in the auxiliary agent described in step S2 are: sodium alginate 1-2%, fulvic acid 0.4-0.6%, calcium chloride 1-2%, polyethylene glycol 2-3%, and the balance is deionized water.

[0018] Further preferably, the additive amount of the additive is 1 / 100 to 2 / 100 of the total volume of the mud-water mixture.

[0019] Further preferably, the elution sludge treatment unit uses a plate and frame filter press to treat the sludge.

[0020] Compared with the prior art, the present invention has the following advantages: 1. The present invention provides a process for eluting and removing particulate nutrients from water bodies. Through physical disturbance, turbulence is generated, so that colloidal sediments roll, colloidal sediments colloidal sediments tumble, colloidal sediments colloidal sediments settle by gravity, inorganic particles are covered in situ, colloidal pollutants with smaller particle sizes are pumped out with water, filtered and transported after flocculation and precipitation, and the separated clean water flows back into the river. This process technology can effectively remove nutrients, control endogenous pollution by transferring small particles, improve water transparency, and significantly increase the bulk density of surface sediments, improve the anti-disturbance ability of sediments, and is conducive to building a stable mud-water interface, meeting the light requirements and substrate conditions for the germination and growth of submerged plants, and creating a good water environment for the natural recovery of aquatic ecosystems.

[0021] 2. The flocculant used in the present invention is a modified biological flocculant. The existing process often directly modifies the biological flocculant, and the modification process may destroy the key active sites of the biological flocculant or change its molecular conformation, thereby weakening its flocculation ability. The present invention, by hydrophobic modification of the carrier and loading the nutrients required by the biological flocculant, ensures the flocculation activity of the biological flocculant and forms a stable hydrophobic biological flocculant. It not only has stable performance and can continuously and stably play a flocculation role, but also will not cause secondary pollution to the environment, especially the water body, thereby achieving a win-win situation of environmental benefits and economic benefits.

[0022] 3. The present invention prepares an auxiliary agent by mixing sodium alginate, fulvic acid, 1-2% calcium chloride and polyethylene glycol in a specific ratio to promote the combination between the biological flocculant and the particles, thereby further improving the flocculation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a comparison chart of the results of the bulk density of the sediment of each embodiment and the comparative example; Figure 2 It is a comparison chart of the results of the moisture content of the sludge of each embodiment and the comparative example; Figure 3 It is a comparison chart of the results of organic matter in the sediments of each embodiment and comparative example. DETAILED DESCRIPTION

[0024] In order to further explain the present invention, it is described below in conjunction with the following specific embodiments.

[0025] Example 1

[0026] A process for removing particulate nutrients from water, comprising the following steps: S1. Deeply plow and stir the bottom mud under the action of mechanical force to achieve the desorption and phase separation of pollutants, so as to promote the migration and dissolution of adsorbed pollutants in the bottom mud to the water phase, while the washed large-particle mud and sand settle under the action of gravity; S2. The sludge-water mixture obtained by elution is pumped into the sewage / water separation tank, and modified biological flocculants and additives are added for mechanical stirring. The pollutants are coagulated and precipitated in the sewage / water separation tank, and the clean water returns to the water body. The precipitated sludge enters the elution sludge treatment unit for treatment.

[0027] The concentration of the modified bioflocculant is 40 mg / L.

[0028] The preparation of the modified bioflocculant comprises the following steps: (1) Cu2O, ZnCl2 and CeCl3 were added to an ethanol aqueous solution (50%) in the ratio of 10:7:1, with the mass volume ratio of CeCl3 to ethanol aqueous solution being 1 mg:15 mL. After uniform ultrasonic dispersion, 0.25 times the weight of CeCl3 in polyvinyl pyrrolidone was added. After stirring at 200 rpm for 20 min, Na2S2O3 solution was added dropwise at 100 rpm under room temperature while stirring. The concentration of Na2S2O3 solution was 1 mol / L, and the amount added was 0.3 times that of the ethanol aqueous solution. After the addition was completed, stirring was continued for 2 h. The mixture was filtered, washed twice with deionized water and twice with anhydrous ethanol, and then placed in a vacuum drying oven, dried at 50 °C to constant weight, and then placed in a muffle furnace and calcined at 400 °C for 2 h to obtain Ce-ZnO powder for use. (2) Chitosan was dissolved in 1% glacial acetic acid, with a mass volume ratio of chitosan to glacial acetic acid of 1 mg:8 mL. After ultrasonic dispersion at room temperature for 20 min, the silk fibroin solution was added. The mass fraction ratio of silk fibroin to chitosan in the mixed solution after the addition of the silk fibroin solution was 1:2. After stirring at 300 rpm for 10 min, the mixture was allowed to stand for 1 h and then heated to 80 °C. D,L-lactide (4 times the mass of chitosan) was added and stirred at 200 rpm for 2 h. 0.23 times of stannous octoate, react at 200 rpm, 100 ° C for 20 h, stop heating, add 0.4 times of chitosan mass in methanol / acetic acid solution with a volume ratio of 8:1, react at 200 rpm for 40-60 min, cool naturally to room temperature, use a hollow fiber membrane with a pore size of 1000 Da for ultrafiltration, wash with anhydrous ethanol for 3 times, place in a vacuum drying oven, and dry at 50 ° C to constant weight to obtain a modified silk fibroin / chitosan composite; (3) The Ce-ZnO powder obtained in step (1) and the modified silk fibroin / chitosan complex obtained in step (2) are ultrasonically dispersed in sterile water in a mass ratio of 1:1. After uniform dispersion, a culture medium is added. The components and concentrations in the culture medium are as follows: 5 g / L yeast extract, 2 g / L peptone, 30 g / L mannitol, and 0.7 g / L K2HPO4. After thorough mixing, the Bacillus cereus strain is added. The mixture is then placed in a constant temperature shaker at 35°C and 120 rpm for shaking culture for 1 day, and then transferred to a centrifuge and centrifuged at 5000 rpm for 10 min. The supernatant is taken, and 3 times the volume of pre-cooled ethanol is added to the supernatant. The resulting mixture is placed in a refrigerator at 4°C for 40 h, and then placed in a centrifuge for centrifugation at 10000 rpm for 10 min. The precipitate is collected and placed in a vacuum freeze dryer for drying.

[0029] The ingredients and corresponding weight percentages in the auxiliary agent are: sodium alginate 1%, fulvic acid 0.4%, calcium chloride 1%, polyethylene glycol 2%, and the balance is deionized water; The amount of the additive added is 1 / 100 of the total volume of the mud-water mixture.

[0030] Example 2

[0031] A process for removing particulate nutrients from water, comprising the following steps: S1. Deeply plow and stir the bottom mud under the action of mechanical force to achieve the desorption and phase separation of pollutants, so as to promote the migration and dissolution of adsorbed pollutants in the bottom mud to the water phase, while the washed large-particle mud and sand settle under the action of gravity; S2. The sludge-water mixture obtained by elution is pumped into the sewage / water separation tank, and modified biological flocculants and additives are added for mechanical stirring. The pollutants are coagulated and precipitated in the sewage / water separation tank, and the clean water returns to the water body. The precipitated sludge enters the elution sludge treatment unit for treatment.

[0032] The concentration of the modified bioflocculant is 50 mg / L.

[0033] The preparation of the modified bioflocculant comprises the following steps: (1) Cu2O, ZnCl2 and CeCl3 were added to an ethanol aqueous solution (50%) in the ratio of 11:8:1, with the mass volume ratio of CeCl3 to ethanol aqueous solution being 1 mg:17 mL. After uniform ultrasonic dispersion, 0.3 times the weight of CeCl3 in polyvinyl pyrrolidone was added. After stirring at 250 rpm for 25 min, Na2S2O3 solution was added dropwise at 150 rpm under room temperature. The concentration of Na2S2O3 solution was 1 mol / L, and the amount added was 0.35 times that of the ethanol aqueous solution. After the addition was completed, stirring was continued for 2.5 h. The mixture was filtered, washed twice with deionized water and twice with anhydrous ethanol, and then placed in a vacuum drying oven, dried at 55 °C to constant weight, and then placed in a muffle furnace and calcined at 450 °C for 2.5 h to obtain Ce-ZnO powder for use. (2) Chitosan was dissolved in 1% glacial acetic acid, with a mass volume ratio of chitosan to glacial acetic acid of 1 mg:10 mL. After ultrasonic dispersion at room temperature for 25 min, the silk fibroin solution was added. The mass fraction ratio of silk fibroin to chitosan in the mixed solution after the silk fibroin solution was 1:3. After stirring at 350 rpm for 12 min, the mixture was allowed to stand for 1.5 h and then heated to 85 °C. D,L-lactide (4.5 times the mass of chitosan) was added and stirred at 250 rpm for 2.5 h. Stannous octoate (0.24 times the mass of chitosan) was reacted at 250 rpm and 105°C for 25 h, the heating was stopped, a methanol / acetic acid solution (0.43 times the mass of chitosan) with a volume ratio of 8:1 was added, the reaction was continued at 250 rpm for 50 min, the mixture was naturally cooled to room temperature, ultrafiltration was performed using a hollow fiber membrane with a pore size of 1000 Da, the mixture was washed 4 times with anhydrous ethanol, and then placed in a vacuum drying oven and dried at 55°C to constant weight to obtain a modified silk fibroin / chitosan composite. (3) The Ce-ZnO powder obtained in step (1) and the modified silk fibroin / chitosan complex obtained in step (2) are ultrasonically dispersed in sterile water in a mass ratio of 1:1.5. After uniform dispersion, a culture medium is added. The components and concentrations of the culture medium are as follows: 5 g / L yeast extract, 2 g / L peptone, 30 g / L mannitol, and 0.7 g / L K2HPO4. After thorough mixing, the Bacillus cereus strain is added. The mixture is then placed in a constant temperature shaker at 35.5°C and 160 rpm for shaking culture for 1.5 days. The mixture is then transferred to a centrifuge and centrifuged at 5500 rpm for 15 min. The supernatant is taken and 3 times the volume of pre-cooled ethanol is added to the supernatant. The mixture is placed in a refrigerator at 4°C for 56 h, and then placed in a centrifuge for centrifugation at 11000 rpm for 11 min. The precipitate is collected and placed in a vacuum freeze dryer for drying.

[0034] The ingredients and corresponding weight percentages in the auxiliary agent are: 1.5% sodium alginate, 0.5% fulvic acid, 1.5% calcium chloride, 2.5% polyethylene glycol, and the balance is deionized water; The amount of the additive added is 1 / 100 of the total volume of the mud-water mixture.

[0035] Example 3

[0036] A process for removing particulate nutrients from water, comprising the following steps: S1. Deeply plow and stir the bottom mud under the action of mechanical force to achieve the desorption and phase separation of pollutants, so as to promote the migration and dissolution of adsorbed pollutants in the bottom mud to the water phase, while the washed large-particle mud and sand settle under the action of gravity; S2. The sludge-water mixture obtained by elution is pumped into the sewage / water separation tank, and modified biological flocculants and additives are added for mechanical stirring. The pollutants are coagulated and precipitated in the sewage / water separation tank, and the clean water returns to the water body. The precipitated sludge enters the elution sludge treatment unit for treatment.

[0037] The concentration of the modified bioflocculant is 60 mg / L.

[0038] The preparation of the modified bioflocculant comprises the following steps: (1) Cu2O, ZnCl2 and CeCl3 were added to an ethanol aqueous solution (50%) in the ratio of 12:9:1, with the mass volume ratio of CeCl3 to ethanol aqueous solution being 1 mg:20 mL. After uniform ultrasonic dispersion, 0.35 times the weight of CeCl3 in polyvinyl pyrrolidone was added. After stirring at 300 rpm for 30 min, Na2S2O3 solution was added dropwise at 200 rpm while stirring at room temperature. The concentration of Na2S2O3 solution was 1 mol / L, and the amount added was 0.4 times that of the ethanol aqueous solution. After the addition was completed, stirring was continued for 3 h. The mixture was filtered, washed with deionized water for 3 times, washed with anhydrous ethanol for 3 times, placed in a vacuum drying oven, dried at 60 °C to constant weight, placed in a muffle furnace, and calcined at 500 °C for 3 h to obtain Ce-ZnO powder for use. (2) Chitosan was dissolved in 1% glacial acetic acid, with a mass volume ratio of chitosan to glacial acetic acid of 1 mg:12 mL. After ultrasonic dispersion at room temperature for 30 min, the silk fibroin solution was added. The mass fraction ratio of silk fibroin to chitosan in the mixed solution after the addition of the silk fibroin solution was 1:4. After stirring at 400 rpm for 15 min, the mixture was allowed to stand for 2 h and then heated to 90 °C. D,L-lactide (5 times the mass of chitosan) was added and stirred at 300 rpm for 3 h. 0.25 times the mass of stannous octoate was reacted at 300 rpm and 110°C for 30 h, the heating was stopped, 0.45 times the mass of chitosan in a methanol / acetic acid solution with a volume ratio of 8:1 was added, the mixture was reacted at 300 rpm for 60 min, and the mixture was naturally cooled to room temperature. Ultrafiltration was performed using a hollow fiber membrane with a pore size of 1000 Da, and the mixture was washed 5 times with anhydrous ethanol and placed in a vacuum drying oven, and dried at 60°C to constant weight to obtain a modified silk fibroin / chitosan composite. (3) The Ce-ZnO powder obtained in step (1) and the modified silk fibroin / chitosan complex obtained in step (2) are ultrasonically dispersed in sterile water in a mass ratio of 1:2. After uniform dispersion, a culture medium is added. The components and concentrations of the culture medium are as follows: 5 g / L yeast extract, 2 g / L peptone, 30 g / L mannitol, and 0.7 g / L K2HPO4. After thorough mixing, the Bacillus cereus strain is added. The mixture is then placed in a constant temperature shaker at 36°C and 200 rpm for shaking culture for 1 to 2 days, and then transferred to a centrifuge for centrifugation at 6000 rpm for 20 min. The supernatant is taken, and 3 times the volume of pre-cooled ethanol is added to the supernatant. The resulting mixture is placed in a refrigerator at 4°C for 72 h, and then placed in a centrifuge for centrifugation at 12000 rpm for 12 min. The precipitate is collected and placed in a vacuum freeze dryer for drying.

[0039] The ingredients and corresponding weight percentages in the auxiliary agent are: sodium alginate 2%, fulvic acid 0.6%, calcium chloride 2%, polyethylene glycol 3%, and the balance is deionized water; The amount of the additive added is 2 / 100 of the total volume of the mud-water mixture.

[0040] Comparative Example 1 A process for removing particulate nutrients from water, comprising the following steps: S1. Deeply plow and stir the bottom mud under the action of mechanical force to achieve the desorption and phase separation of pollutants, so as to promote the migration and dissolution of adsorbed pollutants in the bottom mud to the water phase, while the washed large-particle mud and sand settle under the action of gravity; S2. The sludge-water mixture obtained by elution is pumped into the sewage / water separation tank, and a modified biological flocculant is added for mechanical stirring. The pollutants are coagulated and precipitated in the sewage / water separation tank, and the clean water returns to the water body. The precipitated sludge enters the elution sludge treatment unit for treatment.

[0041] The concentration of the modified bioflocculant is 50 mg / L.

[0042] The preparation of the modified bioflocculant comprises the following steps: (1) Cu2O, ZnCl2 and CeCl3 were added to an ethanol aqueous solution (50%) in the ratio of 11:8:1, with the mass volume ratio of CeCl3 to ethanol aqueous solution being 1 mg:17 mL. After uniform ultrasonic dispersion, 0.3 times the weight of CeCl3 in polyvinyl pyrrolidone was added. After stirring at 250 rpm for 25 min, Na2S2O3 solution was added dropwise at 150 rpm under room temperature. The concentration of Na2S2O3 solution was 1 mol / L, and the amount added was 0.35 times that of the ethanol aqueous solution. After the addition was completed, stirring was continued for 2.5 h. The mixture was filtered, washed twice with deionized water and twice with anhydrous ethanol, and then placed in a vacuum drying oven, dried at 55 °C to constant weight, and then placed in a muffle furnace and calcined at 450 °C for 2.5 h to obtain Ce-ZnO powder for use. (2) Chitosan was dissolved in 1% glacial acetic acid, with a mass volume ratio of chitosan to glacial acetic acid of 1 mg:10 mL. After ultrasonic dispersion at room temperature for 25 min, the silk fibroin solution was added. The mass fraction ratio of silk fibroin to chitosan in the mixed solution after the silk fibroin solution was 1:3. After stirring at 350 rpm for 12 min, the mixture was allowed to stand for 1.5 h and then heated to 85 °C. D,L-lactide (4.5 times the mass of chitosan) was added and stirred at 250 rpm for 2.5 h. Stannous octoate (0.24 times the mass of chitosan) was reacted at 250 rpm and 105°C for 25 h, the heating was stopped, a methanol / acetic acid solution (0.43 times the mass of chitosan) with a volume ratio of 8:1 was added, the reaction was continued at 250 rpm for 50 min, the mixture was naturally cooled to room temperature, ultrafiltration was performed using a hollow fiber membrane with a pore size of 1000 Da, the mixture was washed 4 times with anhydrous ethanol, and then placed in a vacuum drying oven and dried at 55°C to constant weight to obtain a modified silk fibroin / chitosan composite. (3) The Ce-ZnO powder obtained in step (1) and the modified silk fibroin / chitosan complex obtained in step (2) are ultrasonically dispersed in sterile water in a mass ratio of 1:1.5. After uniform dispersion, a culture medium is added. The components and concentrations of the culture medium are as follows: 5 g / L yeast extract, 2 g / L peptone, 30 g / L mannitol, and 0.7 g / L K2HPO4. After thorough mixing, the Bacillus cereus strain is added. The mixture is then placed in a constant temperature shaker at 35.5°C and 160 rpm for shaking culture for 1.5 days. The mixture is then transferred to a centrifuge and centrifuged at 5500 rpm for 15 min. The supernatant is taken and 3 times the volume of pre-cooled ethanol is added to the supernatant. The mixture is placed in a refrigerator at 4°C for 56 h, and then placed in a centrifuge for centrifugation at 11000 rpm for 11 min. The precipitate is collected and placed in a vacuum freeze dryer for drying.

[0043] Comparative Example 2 A process for removing particulate nutrients from water, comprising the following steps: S1. Deeply plow and stir the bottom mud under the action of mechanical force to achieve the desorption and phase separation of pollutants, so as to promote the migration and dissolution of adsorbed pollutants in the bottom mud to the water phase, while the washed large-particle mud and sand settle under the action of gravity; S2. The sludge-water mixture obtained by elution is pumped into the sewage / water separation tank, and modified biological flocculants and additives are added for mechanical stirring. The pollutants are coagulated and precipitated in the sewage / water separation tank, and the clean water returns to the water body. The precipitated sludge enters the elution sludge treatment unit for treatment.

[0044] The concentration of the modified bioflocculant is 50 mg / L.

[0045] The preparation of the modified bioflocculant comprises the following steps: (1) Chitosan was dissolved in 1% glacial acetic acid, with a mass volume ratio of chitosan to glacial acetic acid of 1 mg:10 mL. After ultrasonic dispersion at room temperature for 25 min, the silk fibroin solution was added. The mass fraction ratio of silk fibroin to chitosan in the mixed solution after adding the silk fibroin solution was 1:3. After stirring at 350 rpm for 12 min, the mixture was allowed to stand for 1.5 h and then heated to 85 °C. D,L-lactide (4.5 times the mass of chitosan) was added and stirred at 250 rpm for 2.5 h. Stannous octoate (0.24 times the mass of chitosan) was reacted at 250 rpm and 105°C for 25 h, the heating was stopped, a methanol / acetic acid solution (0.43 times the mass of chitosan) with a volume ratio of 8:1 was added, the reaction was continued at 250 rpm for 50 min, the mixture was naturally cooled to room temperature, ultrafiltration was performed using a hollow fiber membrane with a pore size of 1000 Da, the mixture was washed 4 times with anhydrous ethanol, and then placed in a vacuum drying oven and dried at 55°C to constant weight to obtain a modified silk fibroin / chitosan composite. (2) The modified silk fibroin / chitosan complex obtained in step (1) is ultrasonically dispersed in sterile water. After uniform dispersion, a culture medium is added. The components and concentrations of the culture medium are as follows: 5 g / L yeast extract, 2 g / L peptone, 30 g / L mannitol, and 0.7 g / L K2HPO4. After thorough mixing, the culture medium is added with Bacillus cereus. The mixture is then placed in a constant temperature shaker at 35.5°C and 160 rpm for shaking culture for 1.5 days. The mixture is then transferred to a centrifuge and centrifuged at 5500 rpm for 15 min. The supernatant is taken and 3 times the volume of pre-cooled ethanol is added to the supernatant. The mixture is placed in a refrigerator at 4°C for 56 h, and then placed in a centrifuge for centrifugation at 11000 rpm for 11 min. The precipitate is collected and placed in a vacuum freeze dryer for drying.

[0046] The ingredients and corresponding weight percentages in the auxiliary agent are: 1.5% sodium alginate, 0.5% fulvic acid, 1.5% calcium chloride, 2.5% polyethylene glycol, and the balance is deionized water; The amount of the additive added is 1 / 100 of the total volume of the mud-water mixture.

[0047] Comparative Example 3 A process for removing particulate nutrients from water, comprising the following steps: S1. Deeply plow and stir the bottom mud under the action of mechanical force to achieve the desorption and phase separation of pollutants, so as to promote the migration and dissolution of adsorbed pollutants in the bottom mud to the water phase, while the washed large-particle mud and sand settle under the action of gravity; S2. The sludge-water mixture obtained by elution is pumped into the sewage / water separation tank, and modified biological flocculants and additives are added for mechanical stirring. The pollutants are coagulated and precipitated in the sewage / water separation tank, and the clean water returns to the water body. The precipitated sludge enters the elution sludge treatment unit for treatment.

[0048] The concentration of the modified bioflocculant is 50 mg / L.

[0049] The preparation of the modified bioflocculant comprises the following steps: (1) Cu2O, ZnCl2 and CeCl3 were added to an ethanol aqueous solution (50%) in the ratio of 11:8:1, with the mass volume ratio of CeCl3 to ethanol aqueous solution being 1 mg:17 mL. After uniform ultrasonic dispersion, 0.3 times the weight of CeCl3 in polyvinyl pyrrolidone was added. After stirring at 250 rpm for 25 min, Na2S2O3 solution was added dropwise at 150 rpm under room temperature. The concentration of Na2S2O3 solution was 1 mol / L, and the amount added was 0.35 times that of the ethanol aqueous solution. After the addition was completed, stirring was continued for 2.5 h. The mixture was filtered, washed twice with deionized water and twice with anhydrous ethanol, and then placed in a vacuum drying oven, dried at 55 °C to constant weight, and then placed in a muffle furnace and calcined at 450 °C for 2.5 h to obtain Ce-ZnO powder for use. (2) Dissolve chitosan in 1% glacial acetic acid, the mass volume ratio of chitosan to glacial acetic acid is 1 mg:10 mL, stir at 350 rpm for 12 min, let stand for 1.5 h and then heat to 85 °C, add D,L-lactide 4.5 times the mass of chitosan, stir at 250 rpm for 2.5 h, add stannous octoate 0.24 times the mass of chitosan, react at 250 rpm, 105 °C for 25 h, stop heating, add 0.43 times the mass of chitosan in methanol / acetic acid solution with a volume ratio of 8:1, react at 250 rpm for 50 min, cool naturally to room temperature, use a hollow fiber membrane with a pore size of 1000 Da for ultrafiltration, wash with anhydrous ethanol 4 times and place in a vacuum drying oven, dry to constant weight at 55 °C to obtain modified chitosan; (3) The Ce-ZnO powder obtained in step (1) and the modified chitosan complex obtained in step (2) are ultrasonically dispersed in sterile water in a mass ratio of 1:1.5. After uniform dispersion, a culture medium is added. The components and concentrations of the culture medium are as follows: 5 g / L yeast extract, 2 g / L peptone, 30 g / L mannitol, and 0.7 g / L K2HPO4. After thorough mixing, the Bacillus cereus strain is added. The mixture is then placed in a constant temperature shaker at 35.5°C and 160 rpm for shaking culture for 1.5 days, and then transferred to a centrifuge for centrifugation at 5500 rpm for 15 min. The supernatant is taken, and 3 times the volume of pre-cooled ethanol is added to the supernatant. The resulting mixture is placed in a refrigerator at 4°C for 56 hours, and then placed in a centrifuge for centrifugation at 11000 rpm for 11 minutes. The precipitate is collected and placed in a vacuum freeze dryer for drying.

[0050] The ingredients and corresponding weight percentages in the auxiliary agent are: 1.5% sodium alginate, 0.5% fulvic acid, 1.5% calcium chloride, 2.5% polyethylene glycol, and the balance is deionized water; The amount of the additive added is 1 / 100 of the total volume of the mud-water mixture.

[0051] Comparative Example 4 A process for removing particulate nutrients from water, comprising the following steps: S1. Deeply plow and stir the bottom mud under the action of mechanical force to achieve the desorption and phase separation of pollutants, so as to promote the migration and dissolution of adsorbed pollutants in the bottom mud to the water phase, while the washed large-particle mud and sand settle under the action of gravity; S2. The sludge-water mixture obtained by elution is pumped into the sewage / water separation tank, and modified biological flocculants and additives are added for mechanical stirring. The pollutants are coagulated and precipitated in the sewage / water separation tank, and the clean water returns to the water body. The precipitated sludge enters the elution sludge treatment unit for treatment.

[0052] The concentration of the modified bioflocculant is 50 mg / L.

[0053] The preparation of the modified bioflocculant comprises the following steps: (1) Cu2O, ZnCl2 and CeCl3 were added to an ethanol aqueous solution (50%) in the ratio of 11:8:1, with the mass volume ratio of CeCl3 to ethanol aqueous solution being 1 mg:17 mL. After uniform ultrasonic dispersion, 0.3 times the weight of CeCl3 in polyvinyl pyrrolidone was added. After stirring at 250 rpm for 25 min, Na2S2O3 solution was added dropwise at 150 rpm under room temperature. The concentration of Na2S2O3 solution was 1 mol / L, and the amount added was 0.35 times that of the ethanol aqueous solution. After the addition was completed, stirring was continued for 2.5 h. The mixture was filtered, washed twice with deionized water and twice with anhydrous ethanol, and then placed in a vacuum drying oven, dried at 55 °C to constant weight, and then placed in a muffle furnace and calcined at 450 °C for 2.5 h to obtain Ce-ZnO powder for use. (2) The Ce-ZnO powder obtained in step (1) is ultrasonically dispersed in sterile water. After uniform dispersion, a culture medium is added. The components and concentrations of the culture medium are as follows: 5 g / L yeast extract, 2 g / L peptone, 30 g / L mannitol, and 0.7 g / L K2HPO4. After thorough mixing, the Bacillus cereus strain is added. The mixture is then placed in a constant temperature shaker at 35.5°C and 160 rpm for shaking culture for 1.5 days. The mixture is then transferred to a centrifuge and centrifuged at 5500 rpm for 15 min. The supernatant is taken and 3 times the volume of pre-cooled ethanol is added to the supernatant. The mixture is placed in a refrigerator at 4°C for 56 hours and then placed in a centrifuge for centrifugation at 11000 rpm for 11 min. The precipitate is collected and placed in a vacuum freeze dryer for drying.

[0054] The ingredients and corresponding weight percentages in the auxiliary agent are: 1.5% sodium alginate, 0.5% fulvic acid, 1.5% calcium chloride, 2.5% polyethylene glycol, and the balance is deionized water; The amount of the additive added is 1 / 100 of the total volume of the mud-water mixture.

[0055] Experimental Testing The bottom mud of a wetland in the western suburbs of Hefei City, Anhui Province was used as a simulated sample, and then the methods of the above-mentioned Examples 1 to 3 and Comparative Examples 1 to 4 were used to carry out the elution and removal test of particulate nutrient salts in water bodies. Then, the parameters were tested according to the method in Table 1.

[0056] Table 1 Test methods

[0057] Test results 1. Effect of elution on sediment bulk density Figure 1 The effect of elution on the change of sediment bulk density is demonstrated, wherein the bulk density of the sediment in Group C (untreated sediment) is 1.354 g / cm3, while the bulk density of Examples 1 to 3 and Comparative Examples 1 to 4 increases by 27.7%, 28.3%, 28.1%, 25.6%, 17.5%, 18.5%, and 13.5% respectively compared with Group C. Under the condition that the disturbance force remains unchanged, the increase in the bulk density of the surface sediment makes it more difficult for the sediment to be resuspended, and the lighter the degree of resuspension, and the bulk density of the sediment is linearly negatively correlated with the degree of resuspension. This shows that the elution removal process of the present invention effectively increases the anti-disturbance ability of the sediment, which is of great value for constructing a stable mud-water interface.

[0058] 2. Effect of elution on sediment moisture content and organic matter The results of the determination of the moisture content and organic matter of the sediment in each group are as follows: Figure 2~3 As shown, the moisture content of the bottom mud of group C is 57.21%, while Examples 1-3 and Comparative Examples 1-4 are respectively reduced by 11.89%, 13.69%, 12%, 8.85%, 7.18%, 6.01%, and 3.8% compared with Group C. The organic matter content of group C is 10.35%, and after the elution process, the organic matter content of each group of Examples 1-3 and Comparative Examples 1-4 is reduced to 5.82%, 5.65%, 5.46%, 6.92%, 7.31%, 7.06%, and 7.73%. The elution process can effectively transfer some small particles, and organic matter is easy to be enriched in the powder particles. Because the particle size of the powder particles is relatively small, the specific surface area is large, and the adsorption capacity is strong, under certain conditions, it can form a stable aggregate structure with humus and other substances. It can be seen from the results that the process of the present invention can significantly transfer small particles and can effectively control endogenous pollution to a large extent.

[0059] 3. Effect of elution on changes in nutrients in overlying water The effect of elution on the changes in N and P nutrients in the overlying water is shown in Table 2.

[0060] Table 2 Effect of elution on the removal rate of N and P nutrients in overlying water

[0061] (2) The effect of elution on the changes in N and P nutrients in interstitial water is shown in Table 3.

[0062] Table 3 Effect of elution on the removal rate of N and P nutrients in interstitial water

[0063] It can be seen from the results in Tables 2 and 3 above that the removal effect of sludge elution on N and P pollutants is obvious, which is significantly better than the control example.

[0064] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A process for removing particulate nutrients from water, characterized in that: The steps include: S1. Deeply plow and stir the bottom mud to achieve desorption and phase separation of pollutants, so that adsorbed pollutants in the bottom mud migrate to the water phase and dissolve, while the washed large-particle mud settles under the action of gravity; S2. Pump the eluted mud-water mixture into a sewage / water separation tank, add modified bioflocculant and additives for mechanical stirring, coagulate and precipitate pollutants in the sewage / water separation tank, return clean water to the water body, and the precipitated sludge enters the elution sludge treatment unit for treatment; The preparation of the modified bioflocculant comprises the following steps: (1) Cu2O, ZnCl2 and CeCl3 were added to an ethanol aqueous solution in the ratio of 10-12:7-9:1 in sequence. After being uniformly dispersed by ultrasonication, polyvinyl pyrrolidone was added. After stirring at 200-300 rpm for 20-30 min, Na2S2O3 solution was added dropwise at 100-200 rpm under room temperature. After the addition was completed, stirring was continued for 2-3 h. The mixture was filtered, washed with deionized water and anhydrous ethanol in sequence, and dried in a vacuum drying oven to constant weight. The mixture was then placed in a muffle furnace and calcined to obtain Ce-ZnO powder for later use. (2) Dissolve chitosan in 1% glacial acetic acid, disperse it ultrasonically at room temperature for 20-30 minutes, then add the silk fibroin solution, stir it at 300-400 rpm for 10-15 minutes, let it stand for 1-2 hours, then heat it to 80-90°C, add D,L-lactide, stir it at 200-300 rpm for 2-3 hours, add stannous octoate, react it at 200-300 rpm and 100-110°C for 20-30 hours, stop heating, add methanol / acetic acid solution with a volume ratio of 8:1, react it at 200-300 rpm for 40-60 minutes, cool it naturally to room temperature, and perform ultrafiltration, washing and drying in sequence to obtain a modified silk fibroin / chitosan complex; (3) The Ce-ZnO powder obtained in step (1) and the modified silk fibroin / chitosan complex obtained in step (2) are ultrasonically dispersed in sterile water in a mass ratio of 1:1-2, and after being evenly dispersed, the culture medium is added, and after being fully mixed, the Bacillus cereus strain is added, and then the mixture is placed in a constant temperature shaker for shaking and culture, and then transferred to a centrifuge for centrifugation at 5000-6000 rpm for 10-20 min. The supernatant is taken, and 3 times the volume of pre-cooled ethanol is added to the supernatant. The resulting mixture is placed in a refrigerator at 4°C for 40-72 h, and then placed in a centrifuge for centrifugation at 10000-12000 rpm for 10-12 min. The precipitate is collected and freeze-dried.

2. The method for removing particulate nutrients from water according to claim 1, characterized in that: The concentration of the modified bioflocculant described in step S2 is 40-60 mg / L.

3. The method for removing particulate nutrients from water according to claim 1, characterized in that: The concentration of the ethanol aqueous solution described in step (1) is 50%; The mass volume ratio of CeCl3 to ethanol aqueous solution is 1 mg: 15-20 mL; The weight of the polyvinyl pyrrolidone is 0.25 to 0.35 times that of CeCl3; The concentration of the Na2S2O3 solution is 1 mol / L, and the amount added is 0.3 to 0.4 times that of the ethanol aqueous solution.

4. The method for removing particulate nutrients from water according to claim 1, characterized in that: The number of times of washing with deionized water in step (1) is 2 to 3 times, and the number of times of washing with anhydrous ethanol is 2 to 3 times; The drying temperature in the vacuum drying oven is controlled to be 50-60°C; During the calcination, the calcination temperature is controlled to be 400-500° C. and the calcination time is 2-3 hours.

5. The method for removing particulate nutrients from water according to claim 1, characterized in that: The mass volume ratio of chitosan to glacial acetic acid in step (2) is 1 mg: 8-12 mL; The mass fraction ratio of silk fibroin to chitosan in the mixed solution after adding the silk fibroin solution is 1:2-4; The mass of the D,L-lactide is 4 to 5 times that of chitosan; The mass of stannous octoate is 0.23 to 0.25 times that of chitosan; The mass of the methanol / acetic acid solution is 0.4 to 0.45 times that of chitosan.

6. The method for removing particulate nutrients from water according to claim 1, characterized in that: The modified silk fibroin / chitosan complex is obtained by ultrafiltration, washing and drying in sequence as described in step (2): ultrafiltration is performed using a hollow fiber membrane with a pore size of 1000Da, and the mixture is washed with anhydrous ethanol for 3 to 5 times and then placed in a vacuum drying oven, and dried at 50 to 60°C to constant weight to obtain a modified silk fibroin / chitosan complex.

7. The method for removing particulate nutrients from water according to claim 1, characterized in that: The components and concentrations of the culture medium in step (3) are: yeast extract 5 g / L, peptone 2 g / L, mannitol 30 g / L, K2HPO4 0.7 g / L; The shaking culture temperature is 35-36°C, the shaking speed of the shaker is 120-200 rpm, and the culture is carried out for 1-2 days.

8. The method for removing particulate nutrients from water according to claim 1, characterized in that: The components and corresponding weight percentages of the auxiliary agent described in step S2 are: sodium alginate 1-2%, fulvic acid 0.4-0.6%, calcium chloride 1-2%, polyethylene glycol 2-3%, and the balance is deionized water.

9. The method for removing particulate nutrients from water according to claim 1, characterized in that: The amount of the additive added is 1 / 100 to 2 / 100 of the total volume of the mud-water mixture.

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