Method of stimulating indigenous microbial remediation of an organically contaminated site with an activator, negative pressure based penetration enhancing target

Abstract

This invention relates to an activator and a method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites based on negative pressure infiltration. By utilizing the negative pressure effect created in the soil through vacuuming, the activator, containing nutrients, slow-release materials, and surfactants, is uniformly distributed throughout the contaminated site, stimulating the growth and activity of indigenous microorganisms and accelerating the degradation of organic pollutants. This invention overcomes the shortcomings of existing in-situ remediation technologies for organically contaminated sites, such as high energy consumption, poor effectiveness, inability to reuse the remediated soil, and limited applicability. The provided activator can target and bind to indigenous microorganisms in the site, providing them with the nutrients necessary for growth, promoting the biodegradation of organic pollutants, and ensuring uniform distribution of the activator within the contaminated site under negative pressure, thereby achieving more uniform and effective in-situ remediation.

Description

Technical Field

[0001] This invention belongs to the field of soil pollution bioremediation technology, and relates to an activator and a method for targeted stimulation of indigenous microorganisms based on negative pressure infiltration to remediate organically contaminated sites. Background Technology

[0002] With the impact of global industrialization, urbanization, and agricultural activities, soil organic pollution has become a widespread and concerning problem. Currently, soils contain various organic pollutants, including petroleum hydrocarbons (PHCs), benzene compounds (BTEX), pesticides, and polycyclic aromatic hydrocarbons (PAHs). These pose potential threats to soil biodiversity, ecological balance, and human health. Soil organic pollution is particularly severe in economically developed regions.

[0003] Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants, typically including compounds such as benzo[a]pyrene, benzo[c]pyrene, and benzo[ghi]pyrene. They are a class of aromatic compounds containing multiple benzene rings. PAHs mainly originate from the incomplete combustion of fossil fuels and can enter the environment through leaks and spills during production, transportation, and storage in the chemical industry. PAHs are semi-volatile organic compounds (SVOCs). Low-molecular-weight PAHs can volatilize into the air under certain environmental conditions; however, as the molecular weight increases, the volatility of PAHs generally decreases. High-molecular-weight PAHs tend to adsorb onto particle surfaces or soil and are less likely to volatilize into the air. Furthermore, the larger the molecular weight of PAHs, the stronger their lipid solubility and the lower their water solubility, resulting in a longer persistence in the environment, higher genotoxicity, and increased carcinogenicity. Therefore, there is an urgent need for a method to remediate PAH-contaminated soil.

[0004] Among the commonly used in-situ remediation technologies for organically contaminated soil, thermal desorption is widely applied, but its high energy consumption contradicts the concept of green development, and the remediated soil cannot be reused. Extraction technology is ineffective in treating SVOCs and is mainly applicable to highly permeable strata, thus having certain limitations. Bioremediation is a green remediation technology without secondary pollution, and rich experience has been accumulated in the practice of bioremediation of organically contaminated soil. Bioventilation technology involves injecting oxygen into the contaminated site to stimulate the activity of indigenous microorganisms and promote microbial degradation. It is mostly used as a follow-up treatment to gas-phase extraction technology, but its effect is poor when used alone and is limited to the vadose zone. Bioaeration technology compensates for the shortcomings of the above technologies to some extent, extending the treatment scope to groundwater, but its continuous aeration process causes more pollutants to volatilize, thus weakening the in-situ biodegradation effect. Biostimulation promotes the growth and activity of microorganisms in the soil by adding appropriate amounts of nutrients (such as nitrogen, phosphorus, and sulfur), thereby accelerating the degradation process of organic pollutants. In biostimulation, activators are usually used to activate the microbial community in the soil and promote the degradation of organic pollutants. Existing activator injection technologies mainly include sandblasting, injection wells, rinsing, injection, and hybrid methods. These technologies have certain limitations, such as low biomass, low remediation efficiency, uneven remediation effects, and limited applicable sites. Summary of the Invention

[0005] The purpose of this invention is to provide an activator and a method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites based on negative pressure infiltration, so as to overcome at least one of the defects of existing in-situ remediation technologies for organically contaminated sites, such as high energy consumption, poor effect, inability to reuse the remediated soil, and limited applicability.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In one aspect, the present invention provides an activator for targeted stimulation of indigenous microorganisms to repair organic pollutants, comprising nutrients, slow-release materials and surfactants, wherein the nutrients include a nitrogen source and / or a phosphorus source, the slow-release material consists of a binding material soluble in hydrophobic organic pollutants as a shell and an active ingredient encapsulated by the shell, the active ingredient being one or a combination of two of slow-release oxygen materials and slow-release buffer solutions.

[0008] When used for soil remediation, activators are generally prepared in solution form, and the solvent can be water or the like.

[0009] Furthermore, the nutrients are selected from one or more of yeast extract, peptone, urea, nitrates, nucleic acids, beef extract, phospholipids, and phosphates, and their addition amount satisfies the following condition: when the activator is added to the contaminated site to be remediated, the C:N:P molar ratio in the contaminated site is 100:(5-20):(0.5-1.5). For example, peptone and beef extract can be selected as the nutrients. Preferably, the concentration of peptone (in the activator) is 6-12 g / L, and the concentration of beef extract (in the activator) is 1-4 g / L.

[0010] Furthermore, the bonding material is paraffin wax;

[0011] And / or, the slow-release oxygen material is one or both of CaO2 or MgO2;

[0012] And / or, the sustained-release buffer solution contains K2HPO4, KH2PO4, organic acids, citric acid, Al 3+ One or more of the following;

[0013] And / or, the particle size of the sustained-release material is 300-800 nm, and the prepared sustained-release material is an encapsulated nano-sustained-release material. The amount of the binding material and the active ingredient added satisfies the following: the drug loading in the sustained-release material (i.e., the mass fraction of the active ingredient contained in the core-shell structured sustained-release material) is 15-30%.

[0014] Furthermore, the amount of the slow-release material added satisfies the following condition: when the activator is added to the contaminated site to be remediated, the oxygen concentration of the contaminated site reaches 8-12 mg / L, and it does not produce toxicity to microorganisms;

[0015] Furthermore, since the sustained-release buffer solution is used to control changes in the pH value of the site, its addition amount must ultimately meet the requirement of controlling the pH of the site within the range of 6-8. For example, in some cases, the total amount of sustained-release material added can be controlled to 10-20 g / L (referring to the amount of sustained-release material added to the activator).

[0016] Furthermore, the surfactant is selected from one or more of rhamnolipids, polysorbate-80, oily substances, and lecithin, and its concentration in the activator is controlled at 1.5-2.5 times the critical micelle concentration. The optimal dosage varies for different types of surfactants. In some embodiments, the optimal dosage of polysorbate-80 is 15 mg / L-30 mg / L (based on the activator dosage). Concentrations exceeding the optimal dosage range will negatively impact bioremediation.

[0017] Furthermore, the activator also includes one or more of the following: carbon source, inorganic salt, and growth factor.

[0018] Furthermore, the carbon source is one or a combination of glucose, starch, and glycerol. When selecting a carbon source, its type, concentration, and compatibility with the existing pollutants must be carefully considered to ensure that the remediation effect is not affected. For remediation processes involving both microbial co-metabolic degradation and anaerobic biodegradation, such as the bioremediation of polychlorinated biphenyls (PCBs) and organochlorine pesticides, a carbon source needs to be added to reduce substrate inhibition and thus improve remediation efficiency. For example, glucose can be added as a carbon source for the biodegradation of 10 mg / L organochlorine pesticide pollution, with an optimal concentration of 5 g / L. This setting of the carbon source addition amount is a conventional setting in the art and does not constitute an innovative point of protection of this invention.

[0019] Furthermore, the inorganic salt contains ions including Zn, which can enhance the activity of microbial enzymes. 2+ and Mn 2+ And SO4, which can act as an electron acceptor 2- and NO2 - One or more of these substances are added at a concentration of 0.01-1 mg / L in the contaminated soil.

[0020] Furthermore, the growth factor is one or more vitamins or hormones that can directly promote the growth and metabolic activities of soil microorganisms, and its content in the activator is 10-20 mg / L.

[0021] In a second aspect, the present invention also provides a method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites based on negative pressure infiltration, comprising the following steps:

[0022] (1) Bury grouting pipes in the contaminated site to be remediated, and install plastic drainage components connecting the liquid extraction pipes at the center of two adjacent grouting pipes, wherein the liquid extraction pipes are also connected to a vacuum assembly.

[0023] (2) Turn on the vacuum assembly and use the plastic drainage component to transfer the negative pressure effect to the contaminated soil area, so that the pores of the contaminated soil area are in a negative pressure state.

[0024] (3) The activator described above is injected through the grouting pipe using the permeation grouting method. The negative pressure effect is used to make the injected activator fully penetrate the contaminated site.

[0025] (4) After grouting is completed, the site is left to stand to complete the in-situ bioremediation of the contaminated site.

[0026] Furthermore, the plastic drainage component can be a plastic drainage board.

[0027] Furthermore, the vacuum assembly includes a vacuum pump, and a water-gas separator is provided between the vacuum pump and the liquid extraction pipeline. The vacuum pump is also connected to an exhaust gas processor. It should be noted that the water-gas separator and the exhaust gas processor are conventional equipment structures in the art, and their specific structures are not the focus of this invention and will not be described in detail here.

[0028] Furthermore, the contaminated site to be remediated is filled with a sand cushion layer, and then covered with a sealing film.

[0029] Furthermore, in step (2), the negative pressure state satisfies the following condition: the vacuum gauge reading in the contaminated site area is stable between -60 kPa and -80 kPa.

[0030] Furthermore, in step (3), the pressure of the permeation grouting through the grouting pipe is controlled at 50-250 kPa.

[0031] Furthermore, in step (4), after grouting, the mixture is left to stand for 10-15 days to allow the activator to fully exert its effect and stimulate the growth and activity of indigenous microorganisms.

[0032] In a third aspect, the present invention also provides a system for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites using negative pressure infiltration, which is used to implement the above-mentioned remediation method, including:

[0033] A sand cushion layer and a sealing membrane are laid sequentially on the contaminated soil;

[0034] The grouting pipe, plastic drainage component, and monitoring and sampling shaft are buried in the contaminated soil and extend out of the sand cushion layer. The grouting pipe is also connected to an external grouting pump, and the plastic drainage component is also connected to the vacuum pump through a liquid extraction pipe.

[0035] And an integrated monitoring system for monitoring indicators such as pore water pressure, biochemical oxygen demand, and resistivity in polluted soil areas.

[0036] In a fourth aspect, the present invention also provides a monitoring system for the targeted stimulation of indigenous microorganisms to remediate organically contaminated sites based on negative pressure infiltration. This system includes real-time monitoring of indicators such as pore water pressure, biochemical oxygen demand, and resistivity using optical fibers, microfluidic chips, and a high-density resistivity imaging system, and includes the installation of vertical sampling wells. This part is a conventional method in the field and will not be described in detail here.

[0037] The optical fiber described in this invention can be pre-embedded using methods such as hanging cloth or top-insertion, and can monitor changes in pore water pressure, strain, temperature, and ground settlement in the site in real time.

[0038] The microfluidic chip of this invention should be fixed to the grouting pipe and plastic drainage component by bonding or welding before construction, and the correct connection with external equipment should be ensured during construction. It can analyze indicators such as biochemical oxygen demand in the soil in real time.

[0039] The high-density resistivity imaging technology of this invention requires determining the electrode layout scheme after the construction area is identified. Electrodes are then placed on the ground surface and in boreholes to form a three-dimensional grid array. This allows for three-dimensional imaging of the resistivity distribution of the site soil. Changes in resistivity reflect characteristics such as soil porosity and water content, which is beneficial for real-time monitoring of the migration of pore water, activators, pollutants, slow-release materials, and the metabolic activity of indigenous bacteria.

[0040] The vertical sampling well of this invention can be constructed using traditional drilling methods. Its purpose is to obtain more detailed soil data, collect soil samples regularly, and obtain indicators such as pollutant concentrations through laboratory analysis to supplement on-site monitoring data and provide a basis for a comprehensive assessment of the remediation effect.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] (I) The activator described in this invention provides nutrients and surfactants. Carbon sources, inorganic salts, and growth factors are selected according to the actual site conditions. Nutrients control protein synthesis and the generation of genetic material (DNA), promoting the growth and activity of microorganisms in the soil and driving the bioremediation process of organically polluted soil. Surfactants improve soil structure, providing a better growth environment for microorganisms, altering the surface tension of microbial cells, and increasing the utilization rate of organic matter by microorganisms. Carbon sources provide microorganisms with the necessary energy and carbon, promoting metabolic activities. Inorganic salts participate in the activity of microbial enzyme systems, acting as electron acceptors and accelerating the microbial degradation process. Growth factors directly promote the growth and metabolic activities of microorganisms, enhancing their ability to degrade organic pollutants.

[0043] (II) The slow-release materials involved in this invention are of two types: one is a slow-release oxygen material, the active ingredient of which is CaO2 or MgO2, and its reaction principle is shown in formulas (1) and (2). After injection, the slow-release oxygen material can continuously release oxygen for a considerable period of time, promoting the reproduction and activity of microorganisms in the soil and improving the soil redox conditions. Compared with the traditional aeration remediation method, it has low energy consumption and reduces the volatilization of organic matter. The other type is a slow-release buffer solution, the active ingredients of which include K2HPO4, KH2PO4, organic acids, citric acid, and Al. 3+Its function is to regulate pH changes caused by oxygen releases and microbial degradation products during the remediation process. Paraffin wax can be used as a binder (for preparing the outer shell of the slow-release material). While it has low water solubility, it is soluble in hydrophobic organic pollutants, allowing it to precisely bind to and release the active substances within them.

[0044] 2MgO2+2H2O==2Mg(OH)2+O2 (1)

[0045] 2CaO2+2H2O==2Ca(OH)2+O2 (2)

[0046] (III) The negative pressure-based infiltration technology described in this invention generates a negative pressure seepage field in the site by vacuuming, promoting the uniform distribution of the activator in the contaminated site. The specific principle is as follows: When vacuuming begins, the gas in the sand layer (i.e., the sand cushion layer) is first removed, creating negative pressure. The initial pore water pressure in the soil then forms a pressure difference with the pore water pressure at these boundaries. Therefore, some water and gas in the foundation soil near the sand layer are drawn out due to the pressure difference, gradually forming a vacuum seepage field in the larger interconnected channels of the soil. Initially, seepage occurs in the larger channels, but as the vacuum pump continues to operate, stress redistributes in the foundation soil. Pore water in the smaller channels of the soil bears excess pore water pressure and simultaneously seeps under negative pressure. Under this effect, a negative pressure seepage field is formed in the contaminated site. This seepage field involves both large and small pores in the soil and causes a certain degree of drainage consolidation of the site soil. Therefore, it can be monitored by measuring surface settlement. It is easy to see that in the initial stage, when pore water is discharged from larger connected channels, the slope of the soil's time-settlement curve is relatively large, while in the later stage, when pore water is discharged from smaller channels under the action of pressure difference, the slope of the time-settlement curve becomes smaller. Through real-time monitoring data from distributed optical fibers, when the time-settlement curve turns inward, it means that a negative pressure seepage field has been initially formed. At this time, by injecting an activator into the site using grouting pipes, the activator can be evenly distributed in the pores of different sizes in the site under the action of the negative pressure seepage field.

[0047] (IV) The negative pressure-based infiltration technology described in this invention can overcome the shortcomings of existing technologies for remediating organically contaminated sites. Compared to traditional technologies such as thermal desorption and electrokinetic remediation for low-permeability sites, the technology described in this invention is more low-carbon. Compared to PVD leaching technology, this technology does not use leaching fluid to combine with pollutants and form colloids that clog soil pores. Instead, it directly utilizes indigenous microorganisms to degrade pollutants in the site, making it a greener remediation method without secondary pollution. Compared to traditional extraction technologies such as SVE, this technology has a better treatment effect on SVOCs such as polycyclic aromatic hydrocarbons and expands the treatment range to low-permeability sites. The treatment range of this technology is within the range that can generate a negative pressure effect, reaching a depth of 10-20m below the surface, making it a synergistic remediation technology for contaminated soil and groundwater.

[0048] (5) The monitoring method for in-situ remediation of organically contaminated sites provided by this invention integrates multiple existing cutting-edge technologies for monitoring. First, a distributed fiber optic sensor network is deployed in the site. Fiber optic sensing has advantages such as high sensitivity and strong anti-interference ability, and can accurately capture the dynamic changes in soil pressure, providing a basis for analyzing the formation of negative pressure seepage fields. At the same time, a microfluidic chip detection device is set in the site. The microfluidic chip is small in size and reacts quickly, providing dynamic change data of pollutant concentration and real-time analysis of indicators such as biochemical oxygen demand in the soil, providing support for evaluating the remediation effect. In addition, high-density resistivity imaging technology is used to perform three-dimensional imaging of the resistivity distribution of the soil in the site. The change in resistivity reflects the porosity, water content and other characteristics of the soil, which is conducive to real-time monitoring of the migration of pore water, activators, pollutants, slow-release materials and the metabolic activities of indigenous bacteria. In order to obtain more detailed soil data, this invention sets up vertical sampling wells in the site, which can collect soil samples regularly and obtain indicators such as pollutant concentration through laboratory analysis, supplementing the on-site monitoring data and providing a basis for a comprehensive evaluation of the remediation effect. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the method for remediating organically contaminated sites by targeted stimulation of indigenous microorganisms based on negative pressure infiltration according to the present invention;

[0050] Figure 2 Schematic diagram of the working principle of a method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites using negative pressure infiltration.

[0051] Figure 3 Construction process flow diagram of a method for remediating organically contaminated sites by targeting indigenous microorganisms with negative pressure infiltration;

[0052] Explanation of markings in the diagram:

[0053] 1- Grouting pipe, 2- Grouting pump, 3- Sealing membrane, 4- Sand cushion layer, 5- Vacuum pressure gauge, 6- Sealing membrane burial trench, 7- Plastic drainage board, 8- Water vapor separator, 9- Vacuum pump, 10- Exhaust gas processor, 11- Monitoring and sampling shaft, 12- Integrated monitoring system. Detailed Implementation

[0054] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0055] To overcome the shortcomings of existing in-situ remediation technologies for organic pollutant sites, such as high energy consumption, poor effectiveness, inability to reuse remediated soil, and limited applicability, this invention provides a method for remediating organic pollutant sites based on negative pressure-induced infiltration targeting and stimulation of indigenous microorganisms, specifically including:

[0056] (1) Select activators according to the actual conditions of the contaminated site. Activators include nutrients, slow-release materials, and surfactants. In addition, carbon sources, inorganic salts, and growth factors can also be selected in the activators.

[0057] (2) Nutrients include nitrogen and phosphorus sources. The optimal source should be selected based on the actual conditions of the contaminated site. Nitrogen sources can be organic (e.g., yeast extract, peptone, urea) or inorganic (ammonium nitrogen, nitrate nitrogen). Phosphorus sources can be organic (e.g., nucleic acids, phospholipids, beef extract) or inorganic (phosphate, phosphate ions). The ratio of nitrogen to phosphorus sources should follow the C:N:P molar ratio of 100:5:1 to 100:20:1 in the contaminated site. For example, peptone and beef extract can be selected as nutrients, with a peptone concentration of 6-12 g / L and a beef extract concentration of 1-4 g / L.

[0058] (3) The sustained-release material is a nano-sized sustained-release microsphere prepared by encapsulation modification, wherein the binder is paraffin, and the active ingredients include sustained-release oxygen material (CaO2 or MgO2) and sustained-release buffer solution (K2HPO4, KH2PO4, organic acid, citric acid, Al). 3+ (etc.), the diameter of the slow-release material is 300-800mm, and its concentration in the activator is 10-20g / L.

[0059] (4) Surfactants can be selected from rhamnolipin, polysorbate-80, oils, lecithin, etc. If polysorbate-80 is selected, its optimal dosage is 100 mg / L-500 mg / L.

[0060] (5) Depending on the site conditions, carbon sources (such as glucose, starch, glycerol, etc.) and inorganic salts (Zn) can also be selected. 2+ Mn 2+SO4 2- NO2 - Carbon sources provide energy and carbon for microorganisms, inorganic salts stimulate the growth and metabolism of native microorganisms, and growth factors directly promote microbial activity.

[0061] (6) Prepare the above-mentioned activator ratio in the slurry storage tank of the organically contaminated site for later use. Then, implement the negative pressure infiltration remediation site technical solution.

[0062] (7) A grouting pipe 1 is installed in the contaminated soil and groundwater. A grout outlet hole is provided in the middle and lower part of the grouting pipe 1. The upper part of the grouting pipe 1 is connected to the grouting pump 2 through a grouting branch pipe and a main pipe. In particular, the injected material is the activator proposed in this invention.

[0063] (8) Install vertical plastic drainage boards at the center position at equal distances from the surrounding grouting pipes, and lay plastic drainage boards 7, sand cushion layer 4, vacuum pump 9 on the contaminated site. Also install water vapor separator 8 and exhaust gas processor 10 to separate water vapor from the extracted material and treat the exhaust gas, establish a negative pressure system for the contaminated site, and open a sealing membrane burial trench 6. Specifically, the spacing of the plastic drainage boards is determined by the specific conditions of the contaminated site, and is generally 1.5-3.0m.

[0064] (9) During the construction process, distributed optical fibers are buried along the plastic drainage board 7 and the grouting pipe 1, and microfluidic chips are installed on the plastic drainage board 7 and the grouting pipe 1. A high-density resistivity imaging system is set up in the site. Finally, distributed optical fibers are laid on the ground surface, and monitoring sampling shafts 11 are set up. Vacuum pressure gauges 5 are installed at the grouting pipe 1, the monitoring sampling shaft 11, and the plastic drainage board 7. The above detection data are uploaded to the integrated monitoring system 12 for analysis and processing.

[0065] (10) Lay the sealing membrane 3 and set up protection to seal the edges of the sealing membrane so that the site to be treated is completely sealed under the sealing membrane.

[0066] (11) Turn on the vacuum pump 9 to apply negative pressure to the contaminated site, extract the ground water and gas, and the extracted substances enter the waste liquid collection and purification system for treatment.

[0067] (12) When the surface settlement-time curve during the vacuuming process shows a clear inflection point, and the readings of each vacuum gauge are between -60 and -80 kPa and relatively stable, the first grouting is carried out. The grouting adopts the permeation grouting method, and the grouting pressure is 50-250 kPa. During the grouting process, the vacuum pump 9 is continuously run to maintain the vacuum pressure and seepage field in the formation. When the vacuum gauge reading at the grouting point reaches -30 to -40 kPa, the vacuuming is stopped. When the vacuum gauge reading at the grouting point is close to 0 and the readings of all vacuum gauges in the site are greater than -15 kPa, the grouting is terminated.

[0068] (13) Let it stand until the indigenous microorganisms in the site multiply and degrade the pollutants. The biochemical oxygen demand of the site is monitored in real time through the monitoring system to reflect the severity of organic pollutants in the site. If the calculated BOD5 (five-day biochemical oxygen demand) is greater than 60mg / L, it means that the remediation is not yet complete. If the dissolved oxygen in the site is less than 6mg / L, the activator needs to be injected again.

[0069] (14) The steps are a stimulation process. After each stimulation, samples are taken from the vertical monitoring sampling well to test the concentration of residual pollutants in the soil. If the standard is met, the remediation is stopped. If the standard is not met, steps (11)-(13) are repeated.

[0070] Based on the above embodiments, the present invention will be further described below with reference to more specific examples.

[0071] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0072] Example 1:

[0073] For polycyclic aromatic hydrocarbon (PAH) contaminated sites, this embodiment provides a method for remediating organically contaminated sites based on negative pressure-induced infiltration targeting and stimulation of indigenous microorganisms, specifically including:

[0074] (1) Select activators according to the actual conditions of the contaminated site. Activators include nutrients, slow-release materials, surfactants, inorganic salts and growth factors.

[0075] (2) In this embodiment, peptone and beef extract are selected as nutrients, wherein the concentration of peptone is 10 g / L and the concentration of beef extract is 2.5 g / L.

[0076] (3) The sustained-release material is a nano-sustaining microsphere prepared by encapsulation modification, wherein the binder is paraffin, and the active ingredients are CaO2 and K2HPO4, respectively. The diameter of the sustained-release material is 300-800mm, and its concentration in the activator is 15g / L. In the two sustained-release materials prepared, the mass ratio of binder to active ingredient is 5:1.

[0077] (4) The surfactant selected is polysorbate-80, and its dosage is 20 mg / L;

[0078] (5) Depending on the site conditions, carbon sources (such as glucose, starch, alcohol, etc.) and inorganic salts (Zn) can also be selected. 2+ Mn 2+ SO4 2- NO2 -Carbon sources provide energy and carbon for microorganisms, inorganic salts stimulate the growth and metabolism of native microorganisms, and growth factors directly promote microbial activity.

[0079] (6) Prepare the above-mentioned activator ratio in the slurry storage tank of the organically contaminated site for later use. Then, implement the negative pressure infiltration remediation site technical solution.

[0080] (7) A grouting pipe 1 is installed in the contaminated soil and groundwater. A grout outlet hole is provided in the middle and lower part of the grouting pipe 1. The upper part of the grouting pipe 1 is connected to the grouting pump 2 through a grouting branch pipe and a main pipe. In particular, the injected material is the activator proposed in this invention.

[0081] (8) Install vertical plastic drainage boards at the center position at equal distances from the surrounding grouting pipes, and lay plastic drainage boards 7, sand cushion layer 4, vacuum pump 9 on the contaminated site. Also install water vapor separator 8 and exhaust gas processor 10 to separate water vapor from the extracted material and treat the exhaust gas, establish a negative pressure system for the contaminated site, and open a sealing membrane burial trench 6. Specifically, the spacing between plastic drainage boards is about 2m.

[0082] (9) During the construction process, distributed optical fibers are buried along the plastic drainage board 7 and the grouting pipe 1, and microfluidic chips are installed on the plastic drainage board 7 and the grouting pipe 1. A high-density resistivity imaging system is set up in the site. Finally, distributed optical fibers are laid on the ground surface, and monitoring sampling shafts 11 are set up. Vacuum pressure gauges 5 are installed at the grouting pipe 1, the monitoring sampling shaft 11, and the plastic drainage board 7. The above detection data are uploaded to the integrated monitoring system 12 for analysis and processing.

[0083] (10) Lay the sealing membrane 3 and set up protection to seal the edges of the sealing membrane so that the site to be treated is completely sealed under the sealing membrane.

[0084] (11) Turn on the vacuum pump 9 to apply negative pressure to the contaminated site, extract the ground water and gas, and the extracted substances enter the waste liquid collection and purification system for treatment.

[0085] (12) When the surface settlement-time curve during the vacuuming process shows a clear inflection point, and the readings of each vacuum gauge are around -60 to -80 kPa and relatively stable, the first grouting is carried out. The grouting adopts the permeation grouting method, and the grouting pressure is around 150 kPa. During the grouting process, the vacuum pump 9 is continuously run to maintain the vacuum pressure and seepage field in the formation. When the vacuum gauge reading at the grouting point reaches around -30 to -40 kPa, the vacuuming is stopped. When the vacuum gauge reading at the grouting point is close to 0 and the readings of all vacuum gauges in the site are greater than -15 kPa, the grouting is terminated.

[0086] (13) Let it stand until the indigenous microorganisms in the site multiply and degrade the pollutants. Monitor the biochemical oxygen demand of the site in real time through the monitoring system. If the calculated BOD5 (five-day biochemical oxygen demand) is greater than 60mg / L, it means that the remediation is not yet complete. At this time, when the dissolved oxygen in the site is less than 6mg / L, the activator needs to be injected again.

[0087] (14) The steps are a stimulation process. After each stimulation, samples are taken from the vertical monitoring sampling well to test the concentration of residual pollutants in the soil. If the standard is met, the remediation is stopped. If the standard is not met, steps (11)-(13) are repeated.

[0088] In summary, the activator provided by this invention can target and bind to indigenous microorganisms in the site, providing them with the nutrients necessary for growth and promoting the biodegradation of organic pollutants. Simultaneously, this invention also designs a remediation method that allows the activator to be evenly distributed throughout the contaminated site under negative pressure, thereby achieving more uniform and effective in-situ remediation. Furthermore, this invention has developed an integrated monitoring system that can monitor key indicators during the remediation process in real time, providing a basis for evaluating and optimizing the remediation effect. Compared with traditional methods, the remediation scheme of this invention is simple to operate, lower in cost, has a wide remediation range, high efficiency, good results, and produces no secondary pollution. It is worth mentioning that this method can also simultaneously improve the foundation of the contaminated site, and can be widely applied to the remediation of various organic contaminated sites. This invention provides an innovative, efficient, and environmentally friendly in-situ organic contaminated site remediation scheme, which is of great significance in addressing the shortcomings of current remediation technologies.

[0089] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites based on negative pressure infiltration, characterized in that, Includes the following steps: (1) Bury grouting pipes in the contaminated site to be remediated, and install plastic drainage components connecting the liquid extraction pipes at the center of two adjacent grouting pipes, wherein the liquid extraction pipes are also connected to a vacuum assembly. (2) Turn on the vacuum assembly and use the plastic drainage component to transfer the negative pressure effect to the contaminated soil area, so that the pores of the contaminated soil area are in a negative pressure state. (3) The activator is injected through the grouting pipe using the permeation grouting method. The negative pressure effect is used to make the injected activator fully penetrate the polluted soil area. (4) After grouting is completed, the site is left to stand to complete the in-situ bioremediation of the contaminated site; The activator includes nutrients, slow-release materials, and surfactants. The nutrients include nitrogen and / or phosphorus sources. The slow-release materials consist of a shell made of a binding material soluble in hydrophobic organic pollutants and an active ingredient encapsulated by the shell. The active ingredient is a combination of slow-release oxygen material and slow-release buffer solution. In step (2), the negative pressure state satisfies the following condition: the vacuum gauge reading in the contaminated site area is stable between -60 kPa and -80 kPa; In step (3), the pressure of the permeation grouting through the grouting pipe is controlled at 50-250 kPa; In step (4), the grouting is left to stand for 10-15 days after grouting; The nutrients are selected from one or more of yeast extract, peptone, urea, nitrate, nucleic acid, beef extract, phospholipids, and phosphates, and their addition amount satisfies the following: when the activator is added to the contaminated site to be remediated, the C:N:P molar ratio in the contaminated site is 100:(5-20):(0.5-1.5). The amount of the slow-release material added satisfies the following conditions: when the activator is added to the contaminated site to be remediated, the oxygen concentration of the contaminated site reaches 8-12 mg / L; and the pH value of the contaminated site reaches 6-8. The contaminated site to be remediated is also covered with a sand cushion layer, and then a sealing film is placed on top of the sand cushion layer.

2. The method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites based on negative pressure infiltration as described in claim 1, characterized in that, The bonding material is paraffin wax; And / or, the slow-release oxygen material is one or both of CaO2 or MgO2; And / or, the sustained-release buffer solution contains K2HPO4, KH2PO4, citric acid, and Al. 3+ One or more of them; And / or, the particle size of the sustained-release material is 300-800 nm.

3. The method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites based on negative pressure infiltration as described in claim 1, characterized in that, The surfactant is selected from one or more of rhamnolipin, polysorbate-80, oily substances, and lecithin, and its concentration in the activator is controlled to be 1-2.5 times the critical micelle concentration.

4. The method for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites based on negative pressure infiltration as described in claim 1, characterized in that, It also includes one or more of the following: carbon source, inorganic salt, and growth factor; The carbon source is one or a combination of glucose, starch, and glycerol; The inorganic salt contains ions including Zn, which can enhance the activity of microbial enzymes. 2+ and Mn 2+ And SO4, which can act as an electron acceptor 2- and NO 2- One or more of these, in a concentration of 0.01-1 mg / L in the activator; The growth factor is one or more vitamins or hormones that can directly promote the growth and metabolic activities of soil microorganisms, and its concentration in the activator is 10-20 mg / L.

5. A system for targeted stimulation of indigenous microorganisms to remediate organically contaminated sites using negative pressure infiltration, used to implement the method as described in claim 1, characterized in that, include: A sand cushion layer and a sealing membrane are laid sequentially on the contaminated soil; The grouting pipe, plastic drainage component, and monitoring and sampling shaft are buried in the contaminated soil and extend out of the sand cushion layer. The grouting pipe is also connected to an external grouting pump, and the plastic drainage component is also connected to the vacuum pump through a liquid extraction pipe. And an integrated monitoring system for monitoring indicators including pore water pressure, biochemical oxygen demand, and resistivity in contaminated soil areas.

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