Repair method based on black and odorous bottom mud in-situ chemical oxidation-biological synergy

Abstract

The invention provides a restoration method based on black and odorous bottom mud in-situ chemical oxidation-biological synergy, and belongs to the technical field of environmental engineering. Comprising the following steps: adding a composite chemical oxidant into the black and odorous bottom mud to be repaired, reacting for a preset time, and adding a composite microbial agent into the same area; the complex microbial inoculant comprises microbial flora, growth factors and a composite carrier; wherein the microbial flora comprises pseudomonas putida, thiobacillus denitrificans, halomonas salina and rhodococcus erythropolis. The composite chemical oxidant provides rapid initial pollution reduction, and the composite microbial inoculant has efficient colonization ability, can perform long-term biodegradation and synergistic remediation, ensures the durability of the effect, solves the problem of mutual inhibition of chemical and biological processes, and is environment-friendly. The method is in-situ remediation, large-scale earthwork is not needed, the total cost is reduced, the method is completed mainly by adding chemicals, and the method is easy to apply and popularize in actual engineering.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering technology, and in particular to a remediation method based on in-situ chemical oxidation-biological synergy of black and odorous sediment. Background Technology

[0002] Black and odorous sediment refers to black or dark-colored sediments in polluted water bodies (such as rivers, lakes, and ponds) that are accompanied by a foul odor due to the long-term accumulation of organic pollutants and lack of oxygen. This type of sediment is one of the core pollution sources of black and odorous water bodies, and its formation is closely related to eutrophication, industrial wastewater, domestic sewage, and agricultural non-point source pollution. Black and odorous sediment is usually in a reducing environment and contains high concentrations of organic matter, nitrogen, phosphorus, and sulfides. Under anaerobic conditions, the decomposition of organic matter produces foul-smelling gases (such as ammonia and hydrogen sulfide), while the sediment continuously releases nutrients into the water body, exacerbating eutrophication, leading to decreased water transparency, depletion of dissolved oxygen, and damage to aquatic ecosystems.

[0003] Existing sediment remediation technologies mainly include dredging (ex-situ) and in-situ remediation. Dredging is costly and presents challenges in sludge disposal. In in-situ remediation, while single chemical oxidation methods (such as adding calcium peroxide) can rapidly oxidize sulfides and some organic matter, the effects are not long-lasting, and high concentrations of oxidants may inhibit subsequent microbial activity. Single bioremediation methods (such as adding bacterial agents) are slow to take effect, and microorganisms struggle to colonize and function in highly polluted environments.

[0004] In recent years, the combined chemical and biological approach has begun to attract attention. However, most methods involve the simple sequential addition of common oxidants and microbial agents, which presents the following problems: (1) Oxidants are released too quickly and become ineffective after reacting with pollutants, failing to create a long-term stable microenvironment for subsequent bioremediation; (2) Microbial agents are easily lost or die due to unsuitable carriers, resulting in poor colonization. Therefore, there is an urgent need to develop an in-situ remediation method that can achieve efficient coupling of oxidation and biological processes, provide long-lasting effects, and is cost-effective. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid, efficient, long-lasting, and relatively low-cost in-situ remediation method for black and odorous sediment. This method achieves highly efficient synergy between chemical oxidation and biodegradation by designing specific composite chemical oxidants and composite microbial agents.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a remediation method based on in-situ chemical oxidation-biological synergy for black and odorous sediment, comprising the following steps: (1) Add a compound chemical oxidant to the black and odorous sediment to be remediated; (2) After the compound chemical oxidant has reacted for the predetermined time, add the compound microbial agent to the same area; The compound microbial agent includes microbial flora, bioactivator and compound carrier; The microbial community includes *Pseudomonas putida*, *Thiobacillus denitrificationus*, *Haloxylon ammodendron*, and *Rhodococcus rubrum*.

[0007] Preferably, the composite chemical oxidant comprises a chemical oxidant and a polymer coating layer; Preferably, the chemical oxidant is selected from at least one of calcium peroxide, magnesium peroxide, persulfate, or permanganate; The polymer coating material is selected from at least one of polycaprolactone, polylactic acid, polyhydroxyalkanoate, or cellulose derivatives.

[0008] Preferably, in step (1), the dosage of the composite chemical oxidant is 500~1000 g / m³. 2 .

[0009] Preferably, the reaction time in steps (1) and (2) is 5 to 10 days.

[0010] Preferably, the compound microbial agent is composed of 40-45% of the bacterial culture of the microbial community, 1.0%-3.0% sodium alginate, 0.5%-2.0% biochar, 0.5%-2.0% calcium nitrate, 0.5%-2.0% yeast extract, 1.0%-5.0% corn steep liquor, 2.0-5.0% skim milk powder, and water.

[0011] Preferably, the ratio of viable counts of *Pseudomonas putida*, *Thiobacillus denitrificans*, *Haloxylon ammodendron*, and *Rhodococcus rubrum* in the bacterial culture solution is 2-4:1-3:1-3:2-4, and the viable count of a single bacterial culture solution is 1-2 × 10⁻⁶. 8 CFU / mL; Preferably, in step (2), the dosage of the compound microbial agent is 5~10 g / m³. 2 The bacterial activity was (1~5)×10 9 CFU / g.

[0012] The composite microbial agent of this invention comprises a microbial community, growth factors, and a composite carrier for supporting the microbial community. The microbial community of this invention is a functionally complementary community, mainly composed of aerobic denitrifying bacteria, nitrifying bacteria, and organic pollutant-degrading bacteria, capable of degrading a broad spectrum of organic pollutants and simultaneously removing sulfides and nitrates. Yeast extract and corn steep liquor serve as nutrient sources to ensure microbial growth; calcium nitrate not only forms a gel with sodium alginate but also acts as a supplementary electron acceptor, diffusing with the microbial agent to deep anoxic zones that are difficult for oxidants to reach, ensuring the denitrification process continues over a larger spatial area, preventing nitrogen accumulation, and simultaneously providing nutrients for aerobic denitrifying bacteria; the composite carrier of this invention consists of sodium alginate microparticles and biochar. Furthermore, sodium alginate provides a hydrophilic gel environment to protect the microbial cells; biochar has a porous structure, adsorption properties, and conductivity, enabling it to enrich pollutants and nutrients, promote microbial membrane formation and interspecies electron transfer, and greatly improve the survival rate, colonization ability, and metabolic activity of the microorganisms.

[0013] This invention utilizes a composite chemical oxidant to provide rapid initial pollution reduction, while a composite microbial agent leverages its efficient colonization capabilities for long-term biodegradation. Together, they ensure the durability of the effect. Through a model of "slow-release oxidation leading to environmental improvement, followed by long-term degradation by functional microbial communities," a synergistic remediation effect of "1+1>2" is achieved.

[0014] The oxidant coating layer and the bacterial agent carrier used in this invention are both biodegradable materials, which are environmentally friendly. The remediation method of this invention is in-situ remediation, which is mainly completed by adding agents. The dosage can be flexibly adjusted according to the degree of pollution. It does not require large-scale earthwork, which reduces the overall cost and is easy to promote and apply in actual engineering. Detailed Implementation

[0015] The strains used in this invention are *Pseudomonas putida* D52045, *Thiobacillus denitrification* D24929, *Haloxylon ammodendron* D73532, and *Rhodococcus rubrum* ATCC 25544, which were purchased from Nuoan Gene Technology (Wuhan) Co., Ltd.

[0016] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0017] Example 1

[0018] A remediation method based on in-situ chemical oxidation-biological synergy of black and odorous sediment includes the following steps: adding 1000 g / m³ of composite chemical oxidant to the black and odorous sediment to be remediated. 2 After 5 days of reaction, 8 g / m² of compound microbial agent was added to the same area. 2 .

[0019] The preparation method of the composite chemical oxidant is as follows: 10g of polycaprolactone (PCL, molecular weight 80,000) was dissolved in 200mL of dichloromethane to form a 5% oil phase solution. 100g of calcium peroxide powder (particle size 100 mesh) was added to the oil phase and emulsified and dispersed in a high-speed homogenizer for 2 minutes to form a uniform suspension. The suspension was slowly poured into 1000mL of an aqueous solution containing 2% polyvinyl alcohol, and stirred continuously at 400rpm for 8 hours to allow the dichloromethane to completely evaporate. After the reaction was completed, the product was filtered, washed with deionized water, vacuum dried at 35℃ for 12 hours, and sieved to obtain a gray granular product with a particle size of 1mm.

[0020] The compound microbial agent is formulated as follows: 40% of the bacterial culture of the aforementioned microbial flora, 2.0% sodium alginate, 1.0% biochar, 1% calcium nitrate, 1% yeast extract, 2% corn steep liquor, 5.0% skim milk powder, and the balance being water.

[0021] The preparation method is as follows: (1) Slowly sprinkle sodium alginate powder into water to avoid clumping, heat to 55±2℃, and stir continuously for about 2 hours until a uniform, transparent, particle-free colloidal solution is formed. Cool to below 30℃, and while stirring (200 rpm), add biochar powder, yeast extract, corn steep liquor powder and skim milk powder in sequence. Then use a high-speed shear disperser at 5000 rpm for 5 minutes to form a uniform suspension slurry. Finally, add calcium nitrate, stir until completely dissolved, and cool to 10℃. (2) The *Pseudomonas putida*, *Thiobacillus denitrificans*, *Haloxylon ammodendron*, and *Rhodococcus rubrum* were cultured to the late logarithmic growth phase, and then resuspended in sterile physiological saline to adjust the viable count of the single bacterial culture to 1 × 10⁻⁶. 10 CFU / mL was then mixed in a 3:2:2:3 ratio to prepare a high-concentration compound bacterial solution. Under low-speed stirring (150 rpm), the compound bacterial solution was slowly and evenly added dropwise to the slurry. The mixture was then kept at a low temperature and gently stirred for 20 minutes. Finally, it was spray-dried (inlet air temperature 120℃, outlet air temperature 60℃, feed rate 20 L / h) to obtain the compound bacterial agent (bacterial activity 1×10⁻⁶). 9 CFU / g).

[0022] Example 2

[0023] Unlike Example 1, this example provides a remediation method based on in-situ chemical oxidation-biological synergy for black and odorous sediment, which includes the following steps: adding 800g / m³ of composite chemical oxidant to the black and odorous sediment to be remediated. 2 After 7 days of reaction, 5 g / m² of compound microbial agent was added to the same area. 2 .

[0024] The formulation of the compound microorganism in this embodiment is as follows: 45% of the bacterial culture of the aforementioned microorganism, 1.0% sodium alginate, 0.5% biochar, 0.5% calcium nitrate, 2.0% yeast extract, 3.0% corn steep liquor, 5.0% skim milk powder and water.

[0025] The ratio of viable counts of *Pseudomonas putida*, *Thiobacillus denitrificans*, *Haloxylon ammodendron*, and *Rhodococcus rubrum* in the bacterial culture solution is 4:1:1:4.

[0026] Comparative Example 1

[0027] Unlike Example 1, the polymer coating material selected for the preparation of the composite chemical oxidant is sodium carboxymethyl cellulose with a viscosity of 1000 mPa·s.

[0028] Comparative Example 2: Unlike Example 1, in preparing the compound microbial agent, A. carrageenan was used to replace biochar in an equal amount; B: Replace yeast extract with an equal amount of malt extract.

[0029] Comparative Example 3: Unlike Example 1, the microbial community in the preparation of the compound microbial agent is composed of: Thiobacillus denitrificationis, Pseudomonas putida, Saccharomyces cerevisiae and Bacillus licheniformis = 3:2:2:3.

[0030] Experimental Example 1

[0031] Sediment: Taken from a typical polluted river, the sediment was uniformly mixed and then distributed into multiple identical cylindrical reaction tubes (50cm in diameter, 100cm in height) for testing. The sediment filling height was 40cm, and the water volume was 50cm. The sediment was black and had a strong odor. Samples were taken 15 days after the addition of the compound microbial agent to test the removal rates of COD, TN, and TP in the water, as well as the content of AVS (sulfides) and organic matter in the sediment. The results are shown in Tables 1 and 2.

[0032] Control group 1: Unlike the method in Example 1, no composite chemical oxidant was added.

[0033] Control group 1: Unlike the method in Example 1, no compound microbial agent was added.

[0034] Example 1 group: The method provided in Example 1 is used.

[0035] Comparative Examples 1-3: The methods provided in Comparative Examples 1-3 were used respectively.

[0036] Table 1 Water quality indicators

[0037] Table 2. Sediment Indicators

[0038] As shown in Tables 1 and 2, the method of this invention can significantly improve water quality, reduce the content of AVS (sulfides) and organic matter in the sediment, and decrease sediment thickness. The results of the control group and the example group show that the combined use of the composite chemical oxidant and composite bacterial agent of this invention is more advantageous than the single treatment group, and the two have a synergistic effect. The experiments of the comparative and example groups demonstrate that the specific combination of the oxidant coating layer, bacterial strains, and bacterial agent carrier used in this invention can further enhance the remediation effect, and the combination of similar materials yields even better results.

[0039] Experimental Example 2

[0040] At the wastewater treatment (aquatic agriculture) pilot plant of the Hubei Provincial Rural Safe Drinking Water Engineering Technology Research Center of Hubei University (Hubei University Landscape Pond), a 200-square-meter impermeable pond was selected. An in-situ remediation experiment of black and odorous bottom sediment was conducted using the method provided in Example 1. Water and sediment indicators were measured on days 8, 18, and 25 after the addition of the compound bacterial agent. The results are shown in Table 3.

[0041] Table 3 Water Quality Indicators

[0042] Table 4. Sediment Indicators

[0043] As shown in Tables 3 and 4, the remediation method of this invention can significantly improve water quality and reduce the content of AVS (sulfides) and organic matter in the sediment after a short reaction time, and can continue to be effective for a considerable period of time without causing odor recurrence.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A remediation method based on in-situ chemical oxidation-biological synergy of black and odorous sediment, characterized in that, Includes the following steps: (1) Add a compound chemical oxidant to the black and odorous sediment to be remediated; (2) After the compound chemical oxidant has reacted for the predetermined time, add the compound microbial agent to the same area; The compound microbial agent includes microbial flora, growth factors, and a compound carrier; The microbial community includes *Pseudomonas putida*, *Thiobacillus denitrificationus*, *Haloxylon ammodendron*, and *Rhodococcus rubrum*.

2. The method according to claim 1, characterized in that, The composite chemical oxidant includes a chemical oxidant and a polymer coating layer.

3. The method according to claim 2, characterized in that, The chemical oxidant is selected from at least one of calcium peroxide, magnesium peroxide, persulfate, or permanganate. The polymer coating material is selected from at least one of polycaprolactone, polylactic acid, polyhydroxyalkanoate, or cellulose derivatives.

4. The method according to claim 3, characterized in that, In step (1), the dosage of the composite chemical oxidant is 500~1000 g / m³. 2 .

5. The method according to claim 4, characterized in that, The reaction time in steps (1) and (2) is 5 to 10 days.

6. The method according to claim 1, characterized in that, The compound microbial agent consists of 40-45% of the bacterial culture of the aforementioned microorganisms, 1.0-3.0% sodium alginate, 0.5-2.0% biochar, 0.5-2.0% calcium nitrate, 0.5-2.0% yeast extract, 1.0-5.0% corn steep liquor, 2.0-5.0% skim milk powder, and water.

7. The method according to claim 6, characterized in that, The ratio of viable counts of *Pseudomonas putida*, *Thiobacillus denitrificans*, *Haloxylon ammodendron*, and *Rhodococcus rubrum* in the bacterial culture solution is 2-4:1-3:1-3:2-4, and the viable count of a single bacterial culture solution is (1-2) × 10⁻⁶. 8 CFU / mL.

8. The method according to claim 7, characterized in that, In step (2), the dosage of the compound microbial agent is 5~10g / m³. 2 The bacterial activity was (1~5)×10⁻⁶. 9 CFU / g.

9. A composite microbial agent for in-situ chemical oxidation-biological synergy in the remediation method according to any one of claims 1 to 8.

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