In-situ three-dimensional bioremediation method for micro-polluted water body

Abstract

This invention discloses an in-situ three-dimensional bioremediation method for slightly polluted water bodies. The method involves collecting a mud-water mixture from the water body to be treated, enriching and culturing it, and collecting the settled sludge. Culture medium II is added to the settled sludge for acclimatization and cultivation to prepare a biological agent. This biological agent is then added to a mixed solution of polyvinyl alcohol-hydrated calcium silicate-fulvic acid (PVA-CSH-FA) or PVA-modified zeolite-FA to prepare an immobilized biological carrier that can slowly release or adsorb calcium ions from the water. Calcium peroxide packing is also prepared to provide oxygen. The immobilized biological carrier packing and calcium peroxide packing are respectively fixed in the upper and lower layers of an ecological sedimentation bed, which is then placed in the slightly polluted water body to achieve in-situ three-dimensional bioremediation. The calcium-precipitating bacterial biological agent obtained through enrichment and acclimatization in this invention, when immobilized and mixed with the carrier material, efficiently and simultaneously removes pollutants such as nitrogen, phosphorus, organic matter, and heavy metals from slightly polluted water bodies.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation technology, specifically to an in-situ three-dimensional bioremediation method for slightly polluted water bodies. Background Technology

[0002] Nitrogen is widely present in nature and is an essential element for the survival and growth of humans, animals, and plants. However, in aquatic ecosystems, excessive nitrogen levels can lead to serious ecological problems, such as black and odorous water bodies, biological poisoning, ecosystem destruction, and reduction of available water resources. Currently, the main technologies for controlling nitrogen pollution in water bodies are in-situ remediation and ex-situ remediation. Ex-situ remediation technologies, represented by mechanical dredging, suffer from high costs, damage to benthic ecosystems, and unstable remediation effects. Therefore, it is necessary to develop ecological and long-term in-situ remediation technologies.

[0003] Microbial in-situ remediation technology is a widely used sediment remediation technology. It involves screening or domesticating highly efficient microbial strains or indigenous microorganisms and adding them to contaminated sediment. The microorganisms decompose, transform, and degrade pollutants through their metabolic processes, thereby reducing the concentration of pollutants in the sediment and improving the river's ecological environment. By establishing highly efficient microbial communities, a complete and efficient degradation system can be formed to adapt to different endogenous pollution environments. It has the advantages of being highly operable, widely applicable, and environmentally friendly, making it one of the popular technologies for aquatic ecological restoration.

[0004] Therefore, providing an efficient, stable, and widely applicable in-situ remediation method for slightly polluted water bodies, achieving efficient removal of nitrogen, phosphorus, organic matter, and heavy metals, has become an urgent technical problem to be solved. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide an in-situ three-dimensional bioremediation method for slightly polluted water bodies. This method utilizes prepared immobilized biological cubic packing material, which is added to the wastewater to be treated to achieve efficient removal of nitrogen, phosphorus, organic matter, and heavy metals. It has the advantages of simple process, stable effect, low cost, and wide applicability.

[0006] The present invention is achieved through the following technical solution.

[0007] One aspect of the present invention provides an in-situ three-dimensional bioremediation method for slightly polluted water bodies, comprising the following steps:

[0008] Step 1, enrichment culture of biologically induced calcium precipitation bacteria:

[0009] Take a mixture of mud and water from the water body to be treated, add enrichment culture medium I at a volume ratio of 1:(4~5), periodically replace enrichment culture medium I, and measure the Ca. 2+ and NH4 +-N removal rates were consistently above 60% and 80% respectively, and settled sludge was collected;

[0010] Step 2, Preparation of biological inoculant:

[0011] Take the precipitated sludge obtained in step 1, add basic culture medium II at a volume ratio of 1:(2~3), and incubate at a constant temperature. Replace the basic culture medium II periodically until loose sludge appears at the bottom. Measure the Ca content in the culture medium. 2+ and NH4 + -N removal rates were consistently above 60% and 80% respectively. Loose sludge was collected to obtain biological agents.

[0012] Step 3, Preparation of immobilized biological carrier packing material:

[0013] Polyvinyl alcohol (PVA), calcium silicate hydrate (CSH) or modified zeolite and fulvic acid (FA) are mixed in a mass ratio of (10-20):(15-30):(0.005-0.010). Deionized water is added to the mixture. The biological agent obtained in step 2 is taken and added to the PVA-CSH-FA or PVA-modified zeolite-FA mixed solution in a volume ratio of (1~2):1. The mixture is poured into a mold and allowed to stand and solidify to obtain PVA-CSH-FA and PVA-modified zeolite-FA immobilized biological carrier fillers, respectively.

[0014] Step 4, Preparation of calcium peroxide filler:

[0015] Calcium peroxide powder, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) were mixed in a mass ratio of (150): (8-15): (15-22). Deionized water was added to the mixture, and the mixture was poured into a mold and cured into a film to obtain calcium peroxide filler.

[0016] Step 5, Deploy the ecological settling bed:

[0017] Immobilized biological carriers and calcium peroxide fillers are fixed in the upper and lower layers of the ecological sedimentation bed, respectively, and the ecological sedimentation bed is then placed into the slightly polluted water body to be treated.

[0018] Preferably, the enrichment culture medium I comprises:

[0019] 0.2~0.5g CaCl2, 0.10~0.6g CH3COONa, 0.2~0.6 g NH4Cl, 0.03~0.08g KH2PO 44 0.10~0.30g MgSO4, 0.20~0.40g NaHCO3, 2.0~4.0 mL trace element solution I, 1000ml deionized water, pH=6.8±0.3;

[0020] Each liter of trace element solution I contains, by mass concentration: 1.00~2.00 g EDTA, 0.30~0.80 g ZnSO4, 0.30~0.90 g MgSO4·7H2O, 0.20~0.80 g FeSO4·7H2O, 0.30~0.90 g CuSO4·5H2O, and 0.10~0.30 g CoCl2·6H2O.

[0021] Preferably, the basic culture medium II comprises:

[0022] 0.1~0.2g CaCl2, 0.02~0.06g CH3COONa, 0.01~0.03g NH4Cl, 0.03~0.07g KH2PO4, 0.10~0.30g MgSO4, 0.10~0.50g NaHCO3, 2.0~4.0 mL of trace element solution II, 1000ml of deionized water, pH=6.8±0.3;

[0023] Each liter of the trace element solution II comprises, by mass concentration: 1.00~2.00 g EDTA, 0.30~0.80 g ZnSO4, 0.30~0.90 g MgSO4·7H2O, 0.20~0.80 g FeSO4·7H2O, 0.30~0.90 g CuSO4·5H2O, and 0.10~0.30 g CoCl2·6H2O.

[0024] Preferably, in step 1, the enrichment culture is carried out at a temperature of 25-30℃ and a rotation speed of 100-150 rpm under aerobic conditions. The culture is carried out in cycles of 5-7 days, with half of the culture medium replaced and the calcium ion concentration gradually reduced to 100 mg / L, 80 mg / L, 70 mg / L, 60 mg / L, and 50 mg / L for staged enrichment.

[0025] Preferably, in step 2, the culture is carried out under aerobic conditions at a temperature of 25~30℃, a rotation speed of 120~150 rpm, and a pH of 6.8±0.3, with the basic culture medium II being replaced every 3~5 days.

[0026] Preferably, in step 3, deionized water is added to the mixture, heated to 80~90℃ to mix thoroughly, sterilized at 121℃ for 30 minutes, cooled to room temperature, and the pH is adjusted to 6.8±0.3.

[0027] As a preferred option, for calcium ion concentration Ca 2+ For water bodies with concentrations <50 mg / L, PVA-CSH-FA immobilized biological carrier packing was prepared to achieve slow release of calcium ions and microbial-induced calcium precipitation process.

[0028] Regarding calcium ion concentration Ca 2+ For water bodies with concentrations >50 mg / L, PVA-modified zeolite-FA immobilized biological carrier packing was prepared.

[0029] As a preferred method, the preparation method of modified zeolite includes:

[0030] 1) Clean the natural zeolite, dry it in an oven at 100~110℃ for 6~12 hours, soak the dried zeolite in a 10~20% hydrochloric acid solution, stir at 50~70℃ for 6~12 hours, rinse until the pH is neutral, and dry at 100~110℃ for 10~12 hours.

[0031] 2) Immerse the acid-treated zeolite in a 1-2 mol / L NaCl solution, stir at 30-60℃ for 12-24 hours, rinse until no chloride ions are present in the filtrate, and dry at 100-110℃ for 10-12 hours to obtain modified zeolite.

[0032] Preferably, in step 4, the material is poured into a cubic mold and left at room temperature for 1-2 hours to initially solidify; then dried at 50-60℃ for 12-24 hours to solidify and demold; the formed cubic filler is immersed in a 10-20g / L polylactic acid (PLA) solution for 3-5 minutes; and then dried again at 40-50℃ for 30 minutes to form a semi-permeable membrane with a thickness of 10-50μm.

[0033] Preferably, in step 5, for water bodies with high calcium ions and low calcium ions, the upper layer of the ecological sedimentation bed uses PVA-CSH-FA carrier packing and PVA-modified zeolite-FA carrier packing, respectively, with the upper layer of packing laid for 10-15cm; the lower layer of packing uses calcium peroxide packing, with the lower layer of packing laid for 7-12cm; and a porous ceramic sheet with a pore size of 0.1-1μm is laid between the two layers of packing, with the middle layer thickness being 5-7cm.

[0034] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0035] 1. This invention targets slightly polluted water bodies with varying calcium ion concentrations. By obtaining a mud-water mixture from the slightly polluted water body, enriching and acclimatizing it, a biological agent containing indigenous microorganisms is obtained. By cultivating and utilizing these indigenous microorganisms, nitrogen and phosphorus in the slightly polluted water body can be removed simultaneously without the need for external bacterial sources.

[0036] 2. The hydrated calcium silicate used in this invention can provide a stable calcium source for water bodies with low calcium ion concentrations through a slow-release effect, ensuring the smooth progress of the MIP process. Furthermore, hydrated calcium silicate has a porous structure and a large specific surface area, providing numerous attachment sites for microorganisms. The pores within its porous structure provide shelter for microbial growth, preventing microbial loss due to fluid erosion. Simultaneously, hydrated calcium silicate is an inexpensive and readily available industrial byproduct, resulting in low raw material costs.

[0037] 3. The fulvic acid used in this invention can improve electron transfer efficiency and promote the production of nitrates (NO3). - -N) to nitrite (NO2) - The conversion of NO2 (-N) to nitrogen (N2) further reduces NO2. - The accumulation of -N avoids the buildup of toxic intermediates and significantly improves the denitrification efficiency of the device for water bodies.

[0038] 4. This invention utilizes PVA-CSH-FA or PVA-modified zeolite-FA filler for in-situ three-dimensional bioremediation, taking advantage of the slow-release calcium ion properties of CSH and the calcium ion adsorption characteristics of modified zeolite to regulate and maintain the calcium ion balance in the water, thereby ensuring the smooth progress of the microbial induced calcium precipitation (MICP) process.

[0039] 5. This invention utilizes fatty acids (FAs) to enhance electron transfer efficiency and promote the secretion of extracellular polymeric substances (EPS), thereby improving biomineralization efficiency. FAs can promote the secretion of EPS, providing more nucleation sites for calcium carbonate crystals, thus lowering the energy barrier for precipitation and improving biomineralization efficiency. Furthermore, FAs can enhance the structural density and porosity of EPS, giving the bioprecipitate a larger specific surface area, thereby improving its ability to adsorb and precipitate heavy metals.

[0040] 6. The modified zeolite used in this invention has a significantly increased specific surface area and porosity compared to natural zeolite, providing more attachment sites for microorganisms. The zeolite modified with hydrochloric acid and sodium chloride exhibits higher adsorption capacity and faster adsorption rate in water with high calcium concentrations, effectively mitigating the negative impact of high calcium concentrations on microbial remediation systems. Furthermore, the modified zeolite maintains high adsorption performance even after multiple cycles, extending the material's service life.

[0041] 7. The calcium peroxide used in this invention can release oxygen, providing sufficient oxygen for aerobic microorganisms, thereby improving nitrification efficiency and promoting ammonia nitrogen conversion. Using a calcium peroxide packing layer as an oxygen supply reduces dependence on external aeration equipment and saves energy. Simultaneously, the aerobic environment created by CaO2 can inhibit anaerobic phosphorus release by polyphosphate-accumulating bacteria.

[0042] 8. The calcium precipitation bacteria biological agent obtained by enrichment and domestication in this invention is mixed with carrier materials using immobilization technology. It can efficiently remove pollutants such as nitrogen, phosphorus, organic matter and heavy metals from slightly polluted water bodies simultaneously through the MIP process. The calcium precipitation bacteria biological agent is obtained by enrichment and domestication. The agent is mixed with immobilized biological carrier materials to obtain filler, which has the advantages of high biological activity, strong adaptability and good treatment effect. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0044] Figure 1(a) shows NH4 in Example 1. + -N removal effect diagram;

[0045] Figure 1(b) is a schematic diagram of the TN removal effect in Example 1;

[0046] Figure 1(c) shows Example 1 PO4 3- -P removal effect diagram;

[0047] Figure 1(d) is a schematic diagram of the TOC removal effect in Example 1;

[0048] Figure 1(e) shows Example 1 Zn 2+ Removal effect diagram;

[0049] Figure 1(f) shows Pb in Example 1. 2+ Removal effect diagram;

[0050] Figure 2(a) shows NH4 in Example 2. + -N removal effect diagram;

[0051] Figure 2(b) is a schematic diagram of the TN removal effect in Example 2;

[0052] Figure 2(c) shows Example 2 PO4 3- -P removal effect shown;

[0053] Figure 2(d) is a schematic diagram of the TOC removal effect in Example 2;

[0054] Figure 2(e) shows Example 2 Zn 2+ Removal effect diagram;

[0055] Figure 2(f) shows Pb in Example 2. 2+ Illustration of the removal effect. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0057] This invention provides an in-situ three-dimensional bioremediation method for slightly polluted water bodies, comprising the following steps:

[0058] Step 1, enrichment culture of biologically induced calcium precipitation bacteria:

[0059] Take 10-15 L of the mud-water mixture from the water body to be treated, and add enrichment culture medium I at a volume ratio of 1:(4-5) for enrichment culture. Set the temperature to 25-30℃, the rotation speed to 100-150 rpm, and culture under aerobic conditions. Repeat this process every 5-7 days, replacing half of the culture medium and gradually decreasing the calcium ion concentration for phased enrichment. The enrichment culture medium I is replaced periodically, and the added calcium ion concentration is... 2+ The concentrations were successively decreased, with calcium ion concentrations set at 100 mg / L, 80 mg / L, 70 mg / L, 60 mg / L, and 50 mg / L; the Ca... 2+ and NH4 + -N removal rates were consistently above 60% and 80% respectively, and settled sludge was collected.

[0060] Enrichment medium I includes:

[0061] 0.2~0.5g CaCl2, 0.10~0.6g CH3COONa, 0.2~0.6 g NH4Cl, 0.03~0.08g KH2PO 44 0.10~0.30g MgSO4, 0.20~0.40g NaHCO3, 2.0~4.0 mL trace element solution I, 1000ml deionized water, pH=6.8±0.3.

[0062] Trace element solution I (per liter) comprises, by mass concentration: 1.00~2.00 g EDTA, 0.30~0.80 g ZnSO4, 0.30~0.90 g MgSO4·7H2O, 0.20~0.80 g FeSO4·7H2O, 0.30~0.90 g CuSO4·5H2O, and 0.10~0.30 g CoCl2·6H2O.

[0063] Step 2, Preparation of biological inoculant:

[0064] Take the precipitated sludge obtained in step 1 and add basal culture medium II at a volume ratio of 1:(2~3). Incubate at a constant temperature. Seal the conical flask with a waterproof sealing film and place it in a constant temperature shaking incubator at 25~30℃, 120~150 rpm, pH=6.8±0.3, under aerobic conditions. Replace the basal culture medium II every 3~5 days until loose sludge appears at the bottom. Measure the Ca content in the culture medium. 2+ and NH4 + -N removal rates were consistently above 60% and 80%, respectively. Loose sludge was collected to obtain biological agents.

[0065] Basic culture medium II includes:

[0066] 0.1~0.2g CaCl2, 0.02~0.06g CH3COONa, 0.01~0.03g NH4Cl, 0.03~0.07g KH2PO4, 0.10~0.30g MgSO4, 0.10~0.50g NaHCO3, 2.0~4.0 mL trace element solution II, 1000ml deionized water, pH=6.8±0.3.

[0067] Trace element solution II (per liter) includes, by mass concentration: 1.00~2.00 g EDTA, 0.30~0.80 g ZnSO4, 0.30~0.90 g MgSO4·7H2O, 0.20~0.80 g FeSO4·7H2O, 0.30~0.90 g CuSO4·5H2O, and 0.10~0.30 g CoCl2·6H2O.

[0068] Step 3, Preparation of immobilized biological carrier packing material:

[0069] Polyvinyl alcohol (PVA), hydrated calcium silicate (CSH) (or modified zeolite), and fulvic acid (FA) were mixed at a mass ratio of (10-20):(15-30):(0.005-0.010). Deionized water was added to the mixture, and the mixture was heated to 80-90°C to ensure thorough mixing. The mixture was then sterilized at 121°C for 30 minutes, cooled to room temperature, and the pH was adjusted to 6.8±0.3. A PVA-CSH-FA or PVA-modified zeolite-FA mixed solution was obtained and cooled to room temperature.

[0070] Take the biological agent obtained in step 2 and add it to the PVA-CSH-FA or PVA-modified zeolite-FA mixed solution at a volume ratio of (1~2):1. Stir gently and pour the PVA-CSH-FA or PVA-modified zeolite-FA mixed solution into a cubic silicone mold (side length 1-5cm). Let it stand and level. Immerse the mold in 50ml of borax solution (5%~10%) and let it stand for 3~6 hours. After solidification, demold to obtain the PVA-CSH-FA or PVA-modified zeolite-FA cubic immobilized biological carrier filler.

[0071] Two types of immobilized biological carriers are designed for two different types of water bodies:

[0072] For low calcium ion concentration (Ca 2+ For water bodies with concentrations <50 mg / L, PVA-CSH-FA immobilized biological carrier packing was prepared to achieve slow release of calcium ions and ensure the smooth progress of the microbial induced calcium precipitation (MICP) process.

[0073] For high calcium ion concentrations (Ca 2+ For water bodies with calcium concentrations >50 mg / L, PVA-modified zeolite-FA immobilized biological carrier packing was prepared to adsorb calcium ions in the water and maintain the calcium ion concentration balance in the water.

[0074] The methods for preparing modified zeolites include:

[0075] Take natural zeolite with a particle size of 0.5~2 mm, rinse with deionized water to remove surface dust and soluble impurities; dry in an oven at 100~110℃ for 6~12 hours until constant weight; soak the dried zeolite in a 10~20% hydrochloric acid solution, stir for 6~12 hours, control the temperature at 50~70℃, rinse with deionized water until pH 7.0±0.1, and dry in an oven at 100~110℃ for 10~12 hours; soak the acid-treated zeolite in a 1~2 mol / L NaCl solution, stir for 12~24 hours, control the temperature at 30~60℃; rinse with deionized water until no obvious chloride ions are found in the filtrate (tested with AgNO3); dry in an oven at 100~110℃ for 10~12 hours to obtain modified zeolite.

[0076] Step 4, Preparation of calcium peroxide filler:

[0077] Mix calcium peroxide powder, polyvinyl alcohol (PVA), and polyethylene glycol (PEG) at a mass ratio of (150):(8-15):(15-22). Add deionized water to the mixture and stir until homogeneous, ensuring no agglomeration. Pour the mixture into a cubic mold and allow it to stand at room temperature for 1-2 hours for initial curing. Dry in an oven at 50-60°C for 12-24 hours until the moisture in the slurry evaporates, and the molded cube filler is cured and demolded. Immerse the formed cubic filler in a 10-20 g / L polylactic acid (PLA) solution for 3-5 minutes. Dry again in an oven at 40-50°C for 30 minutes to form a semi-permeable membrane (10-50 μm thick), ensuring that the oxygen produced by the calcium peroxide reaction can escape and that calcium ions are not released into the water, thus obtaining the calcium peroxide filler.

[0078] Step 5, Deploy the ecological settling bed:

[0079] Immobilized biological carriers and calcium peroxide fillers are fixed in the upper and lower layers of the ecological sedimentation bed, respectively, and the ecological sedimentation bed is then placed into the slightly polluted water body to be treated.

[0080] For water bodies with high and low calcium ion levels, the upper layer of the ecological sedimentation bed uses PVA-CSH-FA carrier packing material and PVA-modified zeolite-FA carrier packing material, respectively; the lower layer uses calcium peroxide packing material to provide oxygen for microorganisms. The lower layer of packing material is laid at a depth of 7-12 cm, and the upper layer at a depth of 10-15 cm. The packing material is placed in high-density polyethylene mesh bags with a mesh size of 2-5 mm, and the four corners of the mesh bags are tied to the corners of the ecological sedimentation bed frame with high-strength nylon ropes. Porous ceramic sheets with a pore size of 0.1-1 μm are laid between the two layers of packing material to ensure oxygen can pass through and that the hydrogen peroxide produced by the calcium peroxide reaction will not harm the microorganisms; the thickness of the intermediate layer is 5-7 cm.

[0081] The main structure of the ecological sedimentation bed includes: the ecological sedimentation bed adopts a frame structure, the frame material is high-density polyethylene, the frame area size is (1.0m-1.5m) × (1.0m-1.5m), the total height is 30-50cm, and the frame thickness is 3-5cm; a permeable net (such as polypropylene mesh) is laid at the bottom of the frame to prevent the filler from leaking into the bottom mud.

[0082] The process of deploying ecological sedimentary beds into the water body to be treated includes: determining the deployment area based on the pollutant status of the water; slowly lowering the bed into the water using hoisting equipment (such as a crane or pontoon) to cover the bottom sediment; and securing the bed to the bottom using anchoring devices (such as concrete anchor blocks or ground piles) after it reaches the target area. High-strength nylon ropes are used to connect adjacent ecological sedimentary beds. The total coverage area of ​​the ecological sedimentary bed filler should be 5%-30% of the surface area of ​​the slightly polluted water body to be treated (depending on the eutrophication status).

[0083] The present invention will be further illustrated below through specific embodiments.

[0084] Example 1:

[0085] This embodiment provides a method for removing nitrogen, phosphorus, organic matter, and heavy metals from slightly polluted water bodies. The slightly polluted water body to be treated in this embodiment comes from a reservoir in Yan'an City. Following the technical solution of this invention, the method includes the following steps:

[0086] Step 1, enrichment culture of biologically induced calcium precipitation bacteria:

[0087] 10L of mud-water mixture was obtained from the slightly polluted water body to be treated and used for bacterial enrichment culture. The mud-water mixture and enrichment culture solution I were mixed at a volume ratio of 1:4 and placed in a constant temperature shaking incubator at 30℃ and 150 rpm under aerobic conditions. A cycle of 5 days was used. When the calcium ion removal rate reached 61.33%, the second stage was initiated, with half of the culture medium replaced and the calcium ion concentration reduced to 80 mg / L. When the calcium ion removal rate reached 65.85%, the third stage was initiated, with half of the culture medium replaced and the calcium ion concentration reduced to 70 mg / L. When the calcium ion removal rate reached 70.39%, the fourth stage was initiated, with half of the culture medium replaced and the calcium ion concentration reduced to 60 mg / L. When the calcium ion removal rate reached 66.71%, the fifth stage was initiated, with half of the culture medium replaced and the calcium ion concentration reduced to 50 mg / L. When the calcium ion removal rate reached 63.22%, and NH4+ was reduced at each stage... + -N removal rate is above 80%, enrichment is completed, and settled sludge is collected;

[0088] The enrichment culture medium I has the following formulation: 0.20 g CaCl2, 0.10 g CH3COONa, 0.60 g NH4Cl, and 0.08 g KH2PO4. 44 0.30 g MgSO4, 0.20 g NaHCO3, 2.0 mL trace element solution I, 1000 mL deionized water, pH=6.8±0.3.

[0089] The trace element solution I (per liter) comprises, by mass concentration: 2.00 g EDTA, 0.80 g ZnSO4, 0.90 g MgSO4·7H2O, 0.20 g FeSO4·7H2O, 0.90 g CuSO4·5H2O, and 0.30 g CoCl2·6H2O.

[0090] Step 2, Preparation of biological inoculant:

[0091] Take a 2cm section of sludge from the middle layer of the collected sludge sediment. Add basic culture medium II to the sludge at a volume ratio of 1:3 and mix well. Incubate under aerobic conditions at 25℃ and 150 rpm. After 4 days of incubation, remove the supernatant, and incubate the resulting precipitate again. Replace culture medium II every 5 days until loose sludge appears. Measure the Ca content in the culture medium. 2+ and NH4 + When the -N removal rate is consistently higher than 60% and 80% respectively, the loose sludge is collected to obtain the biological agent.

[0092] The basic culture medium II formula is as follows: 0.1g CaCl2, 0.02g CH3COONa, 0.03g NH4Cl, 0.07g KH2PO4, 0.30g MgSO4, 0.10g NaHCO3, 2.0 mL trace element solution II, 1000ml deionized water, pH=6.8±0.3.

[0093] The trace element solution II (per liter) comprises, by mass concentration: 1.00 g EDTA, 0.30 g ZnSO4, 0.90 g MgSO4·7H2O, 0.20 g FeSO4·7H2O, 0.30 g CuSO4·5H2O, and 0.10 g CoCl2·6H2O.

[0094] Step 3, Preparation of immobilized biological carrier packing material:

[0095] Take 10g of PVA, add deionized water to 90mL, heat to 80℃, stir until completely dissolved to form a clear solution, and cool to room temperature. Gradually add 30g of ground CSH particles to the cooled PVA solution, stirring slowly with a magnetic stirrer to ensure uniform mixing. Take 30ml of 5mg / L FA solution and add it to the above mixture, continuing to stir to ensure uniform mixing. Sterilize at 121℃ for 30min, cool to room temperature, and adjust the pH to 7.0.

[0096] Add the biological agent obtained in step 2 slowly to the PVA-CSH-FA mixed solution at a 1:1 ratio, stirring gently to avoid damaging the agent. Pour the mixed solution into a cubic silicone mold with sides of 3cm and let it stand until level. Immerse the mold in 50ml of a 5% borax solution and let it stand for 4 hours to obtain the PVA-CSH-FA cubic filler.

[0097] Step 4, Preparation of calcium peroxide filler:

[0098] Take 150g of calcium peroxide powder, 8g of PVA, and 17g of PEG, add deionized water to a final volume of 1.2L, and stir to form a homogeneous slurry, ensuring no agglomeration. Pour the prepared slurry into a cubic mold with sides of 3cm and let it stand at room temperature for 1 hour for initial curing. Dry in an oven at 50℃ for 24 hours until the moisture in the slurry evaporates and a solid structure is formed. Demold the slurry and immerse the formed cubic filler in a 10g / L polylactic acid (PLA) solution for 4 minutes. Dry again in an oven at 50℃ for 30 minutes to form a semi-permeable membrane with a thickness of approximately 20μm, obtaining the calcium peroxide filler.

[0099] Step 5, Deploy the ecological settling bed:

[0100] The ecological submerged bed adopts a frame structure made of high-density polyethylene. The frame dimensions are 1.0m × 1.0m, with a total height of 30cm and a frame thickness of 4cm. A layer of permeable polypropylene mesh is laid at the bottom of the frame to prevent the filler from leaking into the bottom sediment. The ecological submerged bed uses a double-layer filler. The upper layer of the ecological submerged bed uses PVA-CSH-FA carrier filler, laid at 10cm depth; the lower layer uses calcium peroxide filler to provide oxygen for microorganisms, laid at 7cm depth. The filler is placed in high-density polyethylene mesh bags with a mesh size of 4mm, and the four corners of the mesh bags are tied to the corners of the ecological submerged bed frame with high-strength nylon ropes. A porous ceramic sheet with a pore size of 0.5μm is laid between the two layers of filler to ensure that oxygen can pass through and that the hydrogen peroxide produced by the calcium peroxide reaction will not harm the microorganisms. The thickness of the middle layer is 5cm. The submerged bed is slowly lowered into the water body using hoisting equipment (such as a crane or pontoon) so that the ecological submerged bed covers the bottom sediment. After the submerged bed reaches the target area, it is fixed to the bottom of the water body using anchoring devices (concrete anchor blocks). High-strength nylon ropes are used to connect adjacent ecological sedimentation beds. The total coverage area of ​​the ecological sedimentation bed filler accounts for 7% of the surface area of ​​the slightly polluted water body to be treated.

[0101] As can be seen from Figures 1(a), 1(b), 1(c), 1(d), 1(e), and 1(f), as time progresses, NH4... + -N stabilized after day 27, while TN concentration stabilized after day 27, and PO4 concentration stabilized after day 27. 3- -P concentration stabilized after 30 days, TOC concentration stabilized after 27 days, and Zn concentration stabilized after 27 days. 2+ The concentration stabilized after 30 days. (NH4 in the treated slightly polluted water body) + -N, TN, PO4 3- -P, TOC, Zn 2+ and Cd 2+ The removal rates ultimately remained at 96.04%, 94.60%, 87.36%, 90.92%, 97.04%, and 94.35%, respectively, for the untreated slightly polluted water bodies containing NH4.+ -N, TN, PO4 3- -P, TOC, Zn 2+ and Cd 2+ The removal rates were ultimately maintained at 21.87%, 20.80%, 20.69%, 29.59%, 23.09%, and 27.82%, respectively, demonstrating a highly efficient and stable ability to remove nitrogen, phosphorus, organic matter, and heavy metals.

[0102] Example 2:

[0103] This embodiment provides a method for removing nitrogen and phosphorus from slightly polluted water bodies. The slightly polluted water body to be treated in this embodiment originates from an artificial lake in Weinan City. Following the technical solution of this invention, the method includes the following steps:

[0104] Step 1, enrichment culture of biologically induced calcium precipitation bacteria:

[0105] 15L of mud-water mixture was obtained from the slightly polluted water body to be treated and used for bacterial enrichment culture. The mud-water mixture and enrichment culture solution I were mixed at a volume ratio of 1:5 and placed in a constant temperature shaking incubator at 25℃ and 120 rpm under aerobic conditions. A 7-day cycle was used. When the calcium ion removal rate reached 64.47%, the second stage was initiated, with half of the culture medium replaced and the calcium ion concentration reduced to 80 mg / L. When the calcium ion removal rate reached 63.28%, the third stage was initiated, with half of the culture medium replaced and the calcium ion concentration reduced to 70 mg / L. When the calcium ion removal rate reached 72.34%, the fourth stage was initiated, with half of the culture medium replaced and the calcium ion concentration reduced to 60 mg / L. When the calcium ion removal rate reached 65.67%, the fifth stage was initiated, with half of the culture medium replaced and the calcium ion concentration reduced to 50 mg / L. When the calcium ion removal rate reached 62.28%, and NH4+ was reduced at each stage... + -N removal rate is above 80%, enrichment is completed, and settled sludge is collected;

[0106] The enrichment culture medium I is formulated as follows: 0.50 g CaCl2, 0.60 g CH3COONa, 0.20 g NH4Cl, 0.03 g KH2PO4, 0.10 g MgSO4, 0.40 g NaHCO3, 4.0 mL of trace element solution I, 1000 mL of deionized water, pH=6.8±0.3.

[0107] The trace element solution I (per liter) comprises, by mass concentration: 1.00 g EDTA, 0.50 g ZnSO4, 0.30 g MgSO4·7H2O, 0.80 g FeSO4·7H2O, 0.30 g CuSO4·5H2O, and 0.10 g CoCl2·6H2O.

[0108] Step 2, Preparation of biological inoculant:

[0109] Take a 1.5 cm section of sludge from the collected sediment and add it to the basal culture medium II at a volume ratio of 1:2. Mix well and culture under aerobic conditions at 30°C and 120 rpm. After 5 days of culture, remove the supernatant and culture the resulting precipitate again, changing the culture medium II every 5 days until loose sludge appears. Measure the Ca content in the culture medium. 2+ and NH4 + When the -N removal rate is consistently higher than 60% and 80% respectively, the loose sludge is collected to obtain the biological agent.

[0110] The basic culture medium II formulation is as follows: 0.2g CaCl2, 0.06g CH3COONa, 0.01g NH4Cl, 0.03g KH2PO4. 44 0.10 g MgSO4, 0.50 g NaHCO3, 4.0 mL trace element solution II, 1000 mL deionized water, pH=6.8±0.3.

[0111] The trace element solution II (per liter) comprises, by mass concentration: 2.00 g EDTA, 0.80 g ZnSO4, 0.30 g MgSO4·7H2O, 0.80 g FeSO4·7H2O, 0.90 g CuSO4·5H2O, and 0.30 g CoCl2·6H2O.

[0112] Step 3, Preparation of immobilized biological carrier packing material:

[0113] Take 20g of PVA, add deionized water to 180mL, heat to 90℃, stir until completely dissolved to form a transparent solution, and cool to room temperature; slowly add 18g of modified zeolite ground to 50-200 µm to the PVA solution, and stir until homogeneous. Take 40mL of 10mg / L FA solution, add it to the above mixture, continue stirring, sterilize at 121℃ for 30min to ensure thorough mixing, and cool to room temperature, adjusting the pH to 6.8.

[0114] The biological agent obtained in step 2 is slowly added to the PVA-modified zeolite-FA mixed solution at a ratio of 2:1, with gentle stirring to avoid damaging the agent. The mixed solution is poured into a cubic silicone mold with a side length of 5cm and allowed to stand until level. The mold is then immersed in 50ml of a 5% borax solution and allowed to stand for 6 hours to obtain the PVA-modified zeolite-FA cubic filler.

[0115] The modified zeolite was prepared using the following method:

[0116] Preparation of modified zeolite 1:

[0117] Natural zeolite with a particle size of 2 mm was rinsed with deionized water to remove surface dust and soluble impurities. It was then dried in an oven at 105℃ for 10 hours until constant weight was achieved. The dried zeolite was then immersed in a 15% hydrochloric acid solution, stirred for 10 hours at 60℃, rinsed with deionized water until the pH reached 7.0, and dried in an oven at 110℃ for 10 hours. The acid-treated zeolite was then immersed in a 2 mol / L NaCl solution, stirred for 12 hours at 30℃, rinsed with deionized water until no obvious chloride ions were found in the filtrate (tested with AgNO3). Finally, it was dried in an oven at 110℃ for 10 hours to obtain modified zeolite.

[0118] Preparation of modified zeolite 2:

[0119] Natural zeolite with a particle size of 1 mm was rinsed with deionized water to remove surface dust and soluble impurities. It was then dried in an oven at 111℃ for 6 hours until constant weight was achieved. The dried zeolite was then immersed in a 20% hydrochloric acid solution, stirred for 6 hours at 70℃, rinsed with deionized water until the pH reached 7.0, and dried in an oven at 105℃ for 11 hours. The acid-treated zeolite was then immersed in a 1.5 mol / L NaCl solution, stirred for 18 hours at 50℃, and rinsed with deionized water until no obvious chloride ions were found in the filtrate (tested with AgNO3). Finally, it was dried in an oven at 105℃ for 11 hours to obtain modified zeolite.

[0120] Preparation of modified zeolite 3:

[0121] Natural zeolite with a particle size of 0.5 mm was rinsed with deionized water to remove surface dust and soluble impurities. It was then dried in an oven at 100℃ for 12 hours until constant weight was achieved. The dried zeolite was then immersed in a 10% hydrochloric acid solution, stirred for 12 hours at 50℃, rinsed with deionized water until the pH reached 7.0, and dried in an oven at 100℃ for 12 hours. The acid-treated zeolite was then immersed in a 1 mol / L NaCl solution, stirred for 24 hours at 60℃, and rinsed with deionized water until no obvious chloride ions were found in the filtrate (tested with AgNO3). Finally, it was dried in an oven at 100℃ for 12 hours to obtain modified zeolite.

[0122] Step 4, Preparation of calcium peroxide filler:

[0123] Take 150g of calcium peroxide powder, 15g of PVA, and 22g of PEG, add deionized water to a final volume of 1.5L, and stir to form a homogeneous slurry, ensuring no agglomeration. Pour the prepared slurry into a 5cm cube mold and allow it to stand at room temperature for 2 hours for initial curing. Dry it in a 60℃ oven for 12 hours until the moisture in the slurry evaporates, forming a solid structure. Demold the slurry and immerse the formed cubic filler in a 20g / L polylactic acid (PLA) solution for 5 minutes. Dry it again in a 40℃ oven for 30 minutes to form a semi-permeable membrane with a thickness of approximately 50μm, obtaining the calcium peroxide filler.

[0124] Step 5, Deploy the ecological settling bed:

[0125] The ecological submerged bed adopts a frame structure made of high-density polyethylene. The frame dimensions are 1.5m × 1.5m, with a total height of 40cm and a frame thickness of 5cm. A layer of permeable polypropylene mesh is laid at the bottom of the frame to prevent the filler from leaking into the bottom sediment. The ecological submerged bed uses a double-layer filler. The upper layer of the ecological submerged bed uses PVA-CSH-FA carrier filler, laid at 15cm depth; the lower layer uses calcium peroxide filler to provide oxygen for microorganisms, laid at 12cm depth. The filler is placed in high-density polyethylene mesh bags with a mesh size of 5mm, and the four corners of the mesh bags are tied to the corners of the ecological submerged bed frame with high-strength nylon ropes. A porous ceramic sheet with a pore size of 1μm is laid between the two layers of filler to ensure that oxygen can pass through and that the hydrogen peroxide produced by the calcium peroxide reaction will not harm the microorganisms. The thickness of the middle layer is 7cm. The submerged bed is slowly lowered into the water body using hoisting equipment (such as a crane or pontoon) so that the ecological submerged bed covers the bottom sediment. After the submerged bed reaches the target area, it is fixed to the bottom of the water body using anchoring devices (concrete anchor blocks). High-strength nylon ropes are used to connect adjacent ecological sedimentation beds. The total coverage area of ​​the ecological sedimentation bed filler accounts for 10% of the surface area of ​​the slightly polluted water body to be treated.

[0126] As can be seen from Figures 2(a), 2(b), 2(c), 2(d), 2(e), and 2(f), as time progresses, NH4... + -N stabilized after day 24, while TN concentration stabilized after day 24, and PO4 concentration stabilized after day 24. 3- -P concentration stabilized after 30 days, organic matter concentration stabilized after 24 days, and Zn... 2+ The concentration stabilized after day 30, Cd 2+ The concentration stabilized after day 27. The treated slightly polluted water body contained NH4. + -N, TN, PO4 3- -P, TOC, Zn 2+ and Cd 2+The removal rates ultimately remained at 95.53%, 92.20%, 93.26%, 92.97%, 97.88%, and 94.06%, respectively, for the untreated slightly polluted water bodies containing NH4. + -N, TN, PO4 3- -P, TOC, Zn 2+ and Cd 2+ The removal rates were ultimately maintained at 30.26%, 29.02%, 34.63%, 23.24%, 15.62%, and 18.61%, respectively, demonstrating a highly efficient and stable ability to remove nitrogen, phosphorus, organic matter, and heavy metals.

[0127] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. An in-situ three-dimensional bioremediation method for slightly polluted water bodies, characterized in that, Includes the following steps: Step 1, enrichment culture of biologically induced calcium precipitation bacteria: Take a mixture of mud and water from the water body to be treated, add enrichment culture medium I at a volume ratio of 1:(4~5), periodically replace enrichment culture medium I, and measure the Ca. 2+ and NH4 + -N removal rates were consistently above 60% and 80% respectively, and settled sludge was collected; The enrichment culture medium I includes: 0.2~0.5g CaCl2, 0.10~0.6g CH3COONa, 0.2~0.6g NH4Cl, 0.03~0.08g KH2PO4, 0.10~0.30g MgSO4, 0.20~0.40g NaHCO3, 2.0~4.0 mL trace element solution I, 1000ml deionized water, pH=6.8±0.3; Each liter of trace element solution I contains, by mass concentration: 1.00~2.00 g EDTA, 0.30~0.80 g ZnSO4, 0.30~0.90 g MgSO4·7H2O, 0.20~0.80 g FeSO4·7H2O, 0.30~0.90 g CuSO4·5H2O, and 0.10~0.30 g CoCl2·6H2O; Step 2, Preparation of biological inoculant: Take the precipitated sludge obtained in step 1, add basic culture medium II at a volume ratio of 1:(2~3), and incubate at a constant temperature. Replace the basic culture medium II periodically until loose sludge appears at the bottom. Measure the Ca content in the culture medium. 2+ and NH4 + -N removal rates were consistently above 60% and 80% respectively. Loose sludge was collected to obtain biological agents. The basic culture medium II includes: 0.1~0.2g CaCl2, 0.02~0.06g CH3COONa, 0.01~0.03g NH4Cl, 0.03~0.07g KH2PO 44 0.10~0.30 g MgSO4, 0.10~0.50 g NaHCO3, 2.0~4.0 mL trace element solution II, 1000 mL deionized water, pH=6.8±0.3; Each liter of the trace element solution II comprises, by mass concentration: 1.00~2.00 g EDTA, 0.30~0.80 g ZnSO4, 0.30~0.90 g MgSO4·7H2O, 0.20~0.80 g FeSO4·7H2O, 0.30~0.90 g CuSO4·5H2O, and 0.10~0.30 g CoCl2·6H2O; Step 3, Preparation of immobilized biological carrier packing material: Polyvinyl alcohol (PVA), calcium silicate hydrate (CSH) or modified zeolite and fulvic acid (FA) are mixed in a mass ratio of (10-20):(15-30):(0.005-0.010). Deionized water is added to the mixture. The biological agent obtained in step 2 is taken and added to the PVA-CSH-FA or PVA-modified zeolite-FA mixed solution in a volume ratio of (1~2):

1. The mixture is poured into a mold and allowed to stand and solidify to obtain PVA-CSH-FA and PVA-modified zeolite-FA immobilized biological carrier fillers, respectively. Methods for preparing modified zeolites include: 1) Clean the natural zeolite, dry it in an oven at 100~110℃ for 6~12 hours, soak the dried zeolite in a 10~20% hydrochloric acid solution, stir at 50~70℃ for 6~12 hours, rinse until the pH is neutral, and dry at 100~110℃ for 10~12 hours. 2) Immerse the acid-treated zeolite in a 1-2 mol / L NaCl solution, stir at 30-60℃ for 12-24 hours, rinse until no chloride ions are present in the filtrate, and dry at 100-110℃ for 10-12 hours to obtain modified zeolite; Step 4, Preparation of calcium peroxide filler: Calcium peroxide powder, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) were mixed in a mass ratio of (150): (8-15): (15-22). Deionized water was added to the mixture, and the mixture was poured into a mold and cured into a film to obtain calcium peroxide filler. Step 5, Deploy the ecological settling bed: Immobilized biological carriers and calcium peroxide fillers are fixed in the upper and lower layers of the ecological sedimentation bed, respectively, and the ecological sedimentation bed is then placed into the slightly polluted water body to be treated.

2. The in-situ three-dimensional bioremediation method for slightly polluted water bodies according to claim 1, characterized in that, In step 1, the enrichment culture is carried out under aerobic conditions at a temperature of 25-30℃ and a rotation speed of 100-150 rpm. The culture is carried out in cycles of 5-7 days, with half of the culture medium replaced and the calcium ion concentration gradually reduced to 100 mg / L, 80 mg / L, 70 mg / L, 60 mg / L, and 50 mg / L for staged enrichment.

3. The in-situ three-dimensional bioremediation method for slightly polluted water bodies according to claim 1, characterized in that, In step 2, the culture is kept at a constant temperature under aerobic conditions of 25~30℃, 120~150 rpm, pH=6.8±0.3, and the basic culture medium II is replaced every 3~5 days.

4. The in-situ three-dimensional bioremediation method for slightly polluted water bodies according to claim 1, characterized in that, In step 3, deionized water is added to the mixture, heated to 80-90°C to ensure thorough mixing, sterilized at 121°C for 30 minutes, cooled to room temperature, and the pH is adjusted to 6.8±0.

3.

5. The in-situ three-dimensional bioremediation method for slightly polluted water bodies according to claim 1, characterized in that, Regarding calcium ion concentration Ca 2+ For water bodies with concentrations <50 mg / L, PVA-CSH-FA immobilized biological carrier packing was prepared to achieve slow release of calcium ions and microbial-induced calcium precipitation process. Regarding calcium ion concentration Ca 2+ For water bodies with concentrations >50 mg / L, PVA-modified zeolite-FA immobilized biological carrier packing was prepared.

6. The in-situ three-dimensional bioremediation method for slightly polluted water bodies according to claim 1, characterized in that, In step 4, the contents are poured into a cubic mold and left at room temperature for 1-2 hours to allow for initial curing; then dried at 50-60°C for 12-24 hours to cure and demold; the formed cubic filler is then immersed in a 10-20 g / L polylactic acid (PLA) solution for 3-5 minutes; and dried again at 40-50°C for 30 minutes to form a semi-permeable membrane with a thickness of 10-50 μm.

7. The in-situ three-dimensional bioremediation method for slightly polluted water bodies according to claim 1, characterized in that, In step 5, for water bodies with high calcium ions and low calcium ions, the upper layer of the ecological sedimentation bed uses PVA-CSH-FA carrier filler and PVA-modified zeolite-FA carrier filler, respectively, with the upper layer of filler laid to a thickness of 10-15cm; the lower layer of filler uses calcium peroxide filler, with the lower layer of filler laid to a thickness of 7-12cm; and a porous ceramic sheet with a pore size of 0.1-1μm is laid between the two layers of filler, with the middle layer having a thickness of 5-7cm.

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