Activator and method for repairing organic contaminated site by targeted stimulation of indigenous microorganisms based on negative pressure infiltration promotion

Abstract

The invention relates to an activating agent and a method for repairing an organic contaminated site by targeted stimulation of indigenous microorganisms based on negative pressure infiltration promotion, which are characterized in that the activating agent containing nutrient substances, a sustained-release material and a surfactant is promoted to be uniformly distributed in the contaminated site through a negative pressure effect formed in soil by vacuumizing, so that the growth and activity of the indigenous microorganisms can be stimulated, and the effect of repairing the organic contaminated site by targeted stimulation of the indigenous microorganisms is achieved. The degradation of organic pollutants is accelerated. The defects that an existing in-situ organic pollutant site repairing technology is high in energy consumption, poor in effect, incapable of achieving secondary utilization of repaired soil, small in application range and the like are overcome, the provided activating agent can be combined with indigenous microorganisms in the site in a targeted mode, nutrient substances needed by growth are provided for the indigenous microorganisms, biodegradation of organic pollutants is promoted, and the effect of in-situ repairing of the organic pollutant site is achieved. And the activating agent is uniformly distributed in the polluted site under the negative pressure effect, so that more uniform and effective in-situ remediation is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of soil pollution bioremediation, and relates to an activator and a method for repairing organic polluted sites by targetedly stimulating indigenous microorganisms based on negative pressure-promoted infiltration. Background Art

[0002] With the impact of industrialization, urbanization and agricultural activities around the world, soil organic pollution has become a common and concerned issue. Under current circumstances, there are a variety of organic pollutants in the soil, including petroleum hydrocarbons (PHCs), benzene derivatives (BTEX), pesticides, polycyclic aromatic hydrocarbons (PAHs), etc., which pose a potential threat to soil biodiversity, ecological balance and human health. Especially in economically developed areas, the degree of soil organic pollution is more serious.

[0003] PAHs are a typical organic pollutant, usually including compounds such as benzo[a]pyrene, benzo[c]pyrene, and benzo[ghi]pyrene. They are a class of aromatic compounds containing multiple benzene ring structures. PAHs are mainly derived from the incomplete combustion of fossil fuels. They may leak into the environment during production, transportation, and storage in the chemical industry. PAHs are semi-volatile organic compounds (SVOCs). Low molecular weight PAHs will evaporate into the air under certain environmental conditions. However, as the molecular weight increases, the volatility of PAHs usually decreases. High molecular weight PAHs tend to be adsorbed on the surface of particles or in the soil and are not easy to evaporate into the air. At the same time, the larger the molecular weight of PAHs, the stronger the fat solubility, the lower the water solubility, the longer they exist in the environment, the higher the genetic toxicity, and the carcinogenicity increases with the increase of molecular weight. Therefore, there is an urgent need for a method to treat and remediate PAH-contaminated soil.

[0004] Among the commonly used in-situ remediation technologies for organic contaminated soil, thermal desorption technology is widely used, but the energy consumption is too high, which does not conform to the concept of green development, and the remediated soil cannot be reused. Extraction technology is not effective in treating SVOCs, and is mainly applicable to high permeability formations, which has certain limitations. Bioremediation is a green, non-secondary pollution remediation technology, and organic contaminated soil bioremediation has accumulated rich experience in practice. Bioventilation technology is to inject oxygen into the contaminated site to stimulate the activity of indigenous microorganisms and promote microbial degradation. It is mostly used for subsequent treatment of gas phase extraction technology. The effect is very poor when used alone, and it is only limited to the aeration zone. Biological aeration technology makes up for the shortcomings of the above technologies to a certain extent, expanding the treatment range to groundwater, but its uninterrupted aeration process will cause more volatilization of pollutants, thereby weakening the effect of in-situ biodegradation. Biostimulation is to promote the growth and activity of microorganisms in the soil by adding appropriate amounts of nutrients (such as nitrogen, phosphorus, sulfur, etc.), 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. The existing activator injection technologies mainly include sandblasting, injection well method, leaching method, injection method and mixing method. These technologies have certain limitations, such as small biomass, low remediation efficiency, uneven remediation effect, and small applicable site. Summary of the invention

[0005] The purpose of the present invention is to provide an activator and a method for targeted stimulation of indigenous microorganisms to repair organic contaminated sites based on negative pressure-enhanced infiltration, so as to overcome at least one of the defects of existing in-situ repair technologies for organic pollutant sites, such as high energy consumption, poor effect, inability to reuse the repaired soil, and small scope of application.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] On the one hand, 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 nitrogen sources and / or phosphorus sources, the slow-release materials are composed of a binding material that is soluble in hydrophobic organic pollutants as an outer shell, and an active ingredient wrapped by the outer shell, and the active ingredient is a slow-release oxygen material, a slow-release buffer solution, or a combination of both.

[0008] When used for soil remediation, the activator is generally prepared in the form of a solution, and the solvent can be water or the like.

[0009] Furthermore, the nutrient is selected from one or more of yeast extract, peptone, urea, nitrate, nucleic acid, beef extract, phospholipids, and phosphate, and the amount added satisfies: when the activator is added to the contaminated site to be repaired, the molar ratio of C:N:P in the contaminated site is 100:(5-20):(0.5-1.5). Exemplarily, the nutrient can be selected from peptone and beef extract. 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] Further, the bonding material is paraffin;

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

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

[0013] And / or, the particle size of the sustained-release material is 300-800nm, and the prepared sustained-release material is an embedded nano sustained-release material. The addition amount of the binding material and the active ingredient satisfies: the drug loading in the sustained-release material (ie, the mass fraction of the active ingredient contained in the sustained-release material with a core-shell structure) is 15-30%.

[0014] Furthermore, the amount of the slow-release material added satisfies: when the activator is added to the contaminated site to be repaired, the oxygen concentration of the contaminated site reaches 8-12 mg / L and is not toxic to microorganisms;

[0015] In addition, since the slow-release buffer solution is to control the pH value change of the site, its addition amount is ultimately to control the pH of the site within the range of 6 to 8. Exemplarily, in some cases, the addition amount of the overall slow-release material can be controlled to be 10-20 g / L (referring to the addition amount of the slow-release material in the activator).

[0016] Further, the surfactant is selected from one or more of rhamnolipid, polysorbate-80, oily substances, and lecithin, and its concentration in the activator is controlled to be 1.5-2.5 times the critical micelle concentration. The optimal dosage of different types of surfactants is different. In some embodiments, the optimal dosage of polysorbate-80 is 15 mg / L-30 mg / L (based on the activator). The concentration exceeding the optimal dosage range will have a negative impact on bioremediation.

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

[0018] Furthermore, the carbon source is one or a combination of several of glucose, starch, and glycerol. When selecting a carbon source, its type, concentration, and compatibility with the original pollutants must be carefully considered to ensure that the repair effect is not affected. For pollutant remediation processes involving co-metabolic degradation and anaerobic biodegradation by microorganisms, such as bioremediation of polychlorinated biphenyls and organochlorine pesticides, a carbon source needs to be added to reduce substrate inhibition and thereby improve the repair efficiency. For example, for the biodegradation of 10 mg / L organochlorine pesticide pollution, glucose can be added as a carbon source, and its optimal concentration is 5 g / L. The amount of carbon source added in this part belongs to the conventional setting in the field and does not belong to the innovative protection point of the present invention.

[0019] Furthermore, the ions contained in the inorganic salt include Zn, which can improve the activity of microbial enzymes. 2+ and Mn 2+ , and SO4 can act as an electron acceptor 2- and NO2 - One or a combination of the above, the added amount is sufficient to satisfy the content in the contaminated soil of 0.01-1 mg / L.

[0020] Furthermore, the growth factor is one or more of the 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 repair organic contaminated sites based on negative pressure-enhanced infiltration, comprising the following steps:

[0022] (1) burying grouting pipes in the contaminated site to be repaired, and installing plastic drainage parts connected to the liquid extraction pipeline at the center of two adjacent grouting pipes, wherein the liquid extraction pipeline is also connected to the vacuum assembly;

[0023] (2) turning on the vacuum assembly to transmit the negative pressure effect to the contaminated soil area through the plastic drainage piece, so that the pores in the contaminated soil area are in a negative pressure state;

[0024] (3) injecting any of the above mentioned activators through the grouting pipe by means of penetration grouting, and utilizing the negative pressure effect to allow the injected activator to fully penetrate the contaminated site;

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

[0026] Furthermore, the plastic drainage member may be a plastic drainage board.

[0027] Furthermore, the vacuum assembly includes a vacuum pump, a water-gas separator is provided between the vacuum pump and the liquid extraction pipeline, and the vacuum pump is also connected to the exhaust gas processor. It should be pointed out here that the water-gas separator and the exhaust gas processor are both conventional equipment structures in the field, and their specific structures do not belong to the protection points of the present invention, and are not described in detail here.

[0028] Furthermore, the contaminated site to be repaired is also filled with a sand cushion layer, and a sealing film is further covered on the sand cushion layer.

[0029] Furthermore, in step (2), the negative pressure state satisfies: the vacuum gauge reading of the contaminated site area is stabilized at -60 kPa to -80 kPa.

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

[0031] Furthermore, in step (4), the grouting 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 repair organic contaminated sites by negative pressure-promoted infiltration, which is used to implement the above repair method, comprising:

[0033] The sand cushion and sealing membrane are laid on the contaminated soil in sequence;

[0034] A grouting pipe, a plastic drainage piece and a monitoring sampling shaft buried in the contaminated soil and extending out of the sand cushion layer at the top, the grouting pipe is also connected to an external grouting pump, and the plastic drainage piece is also connected to the vacuum pump through a liquid extraction pipeline;

[0035] and an integrated monitoring system for monitoring pore water pressure, biochemical oxygen demand, resistivity and other indicators in contaminated soil areas.

[0036] In the fourth aspect, the present invention also provides a monitoring system for targeted stimulation of indigenous microorganisms to repair organic contaminated sites based on negative pressure-promoted infiltration, which includes integrated real-time monitoring of pore water pressure, biochemical oxygen demand, resistivity and other indicators using optical fiber, microfluidic chip, and high-density resistivity imaging system, and vertical sampling wells are set. This part belongs to the conventional method in the field and will not be repeated here.

[0037] The optical fiber of the present invention can be pre-buried by using a hanging cloth method, a jacking method, etc., and can monitor changes in pore water pressure, strain, temperature, landmark settlement, etc. in the site in real time.

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

[0039] The high-density resistivity imaging technology of the present invention should determine the electrode layout plan after the construction area is determined, and arrange the electrodes on the surface and in the boreholes to complete a three-dimensional grid array. The resistivity distribution of the site soil can be imaged in three dimensions. The resistivity change 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.

[0040] The vertical sampling well of the present invention can be constructed by traditional drilling methods. Its purpose is to obtain more detailed soil data, collect soil samples regularly, obtain indicators such as pollutant concentration through laboratory analysis, supplement field monitoring data, and provide a basis for a comprehensive evaluation of the restoration effect.

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

[0042] (i) The activator described in the present invention provides nutrients and surfactants. And according to the actual situation of the site, carbon sources, inorganic salts, and growth factors are selected. Among them, nutrients control protein synthesis and the generation of genetic material DNA, promote the growth and activity of microorganisms in the soil, and promote the bioremediation process of organic contaminated soil. Surfactants can improve soil structure, provide a better growth environment for microorganisms, change the surface tension of microbial cells, and improve the utilization rate of organic matter by microorganisms. Carbon sources can provide microorganisms with the required energy and carbon elements and promote metabolic activities. Inorganic salts can participate in the activity of microbial enzyme systems and serve as electron acceptors to accelerate the microbial degradation process. Growth factors can directly promote the growth and metabolic activities of microorganisms and improve their ability to degrade organic pollutants.

[0043] (II) The slow-release materials involved in the present invention are divided into two types: one is a slow-release oxygen material, whose active ingredient is CaO2 or MgO2, and its reaction principle is shown in formula (1) and (2). After the slow-release oxygen material is injected, it can continuously release oxygen for a considerable period of time, promote the reproduction and activity of microorganisms in the soil, and improve 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 is a slow-release buffer solution, the active ingredients of which include K2HPO4, KH2PO4, organic acid, citric acid, Al 3+Etc. Its function is to regulate the pH changes caused by oxygen release and microbial degradation products produced during the repair process. Paraffin wax can be used as a binder for the sustained-release material (used to prepare the shell of the sustained-release material). It has low water solubility but is soluble in hydrophobic organic pollutants. It can accurately bind to organic pollutants and release the active substances therein.

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

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

[0046] (III) The technical solution based on negative pressure to promote infiltration described in the present invention generates a negative pressure seepage field in the site by vacuuming, so as to promote the above-mentioned activator to be evenly distributed in the contaminated site. The specific principle is: when vacuuming begins, the gas in the sand layer (i.e., the sand cushion layer) is firstly pumped away to form a negative pressure, and the initial pore water pressure in the soil body forms a certain pressure difference with the pore water pressure of these boundaries, so a part of the water and gas in the foundation soil close to the sand layer will be sucked out due to the pressure difference, and gradually form a vacuum seepage field in the larger connected pores in the soil body. The water in the larger pores will initially seep, but during the continuous operation of the vacuum pump, the stress in the foundation soil will be redistributed, and the pore water in the small pores in the soil will be subjected to excess pore water pressure, and at the same time, seepage will occur under the action of negative pressure. Under this effect, a negative pressure seepage field will be formed in the contaminated site, which involves large and small pores in the soil, and will cause a certain degree of drainage and consolidation of the site soil, so it can be monitored by measuring surface settlement. It is not difficult to conclude that in the initial stage, when the pore water in the larger connected channels is discharged, the slope of the time-settlement curve of the soil is larger, and in the later stage, when the pore water in the small channels is discharged under the action of the pressure difference, the slope of the time-settlement curve becomes smaller. Through the real-time monitoring data of the distributed optical fiber, when the time-settlement curve turns, it means that the negative pressure seepage field has been initially formed. At this time, the activator is injected into the site through the grouting pipe, and the activator can be evenly distributed in the large and small channels in the site under the action of the negative pressure seepage field.

[0047] (IV) The technical solution based on negative pressure-enhanced infiltration described in the present invention can make up for the shortcomings of existing technologies for repairing organic contaminated sites. Compared with traditional thermal desorption, electric remediation and other technologies for low-permeability sites, the technical solution described in the present invention is more low-carbon. Compared with PVD elution technology, this technology does not have the eluent combining with pollutants to form colloids to block soil pores, but directly uses indigenous microorganisms to degrade pollutants in the site. It is a greener remediation method and there is no secondary pollution. Compared with traditional SVE and other extraction technologies, this technology has better treatment effects on SVOCs such as polycyclic aromatic hydrocarbons, and expands the treatment range to low-permeability sites. The treatment range of this technology is the range that can produce a negative pressure effect, up to 10-20m below the surface. It is a synergistic remediation technology for contaminated soil and groundwater.

[0048] (5) The monitoring method for in-situ remediation of organic contaminated sites provided by the present invention adopts a variety of existing cutting-edge technical means for integrated monitoring. First, a distributed optical fiber sensing network is deployed in the site. Optical fiber sensing has the advantages of high sensitivity and strong anti-interference ability, and can accurately capture the dynamic change process of soil pressure, providing a basis for analyzing the formation of negative pressure seepage field. At the same time, a microfluidic chip detection device is set in the site. The microfluidic chip is small in size and fast in response. It can provide dynamic change data of pollutant concentration, and can analyze indicators such as biochemical oxygen demand in soil in real time, 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 resistivity change 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, the present invention sets a vertical sampling well in the site, which can collect soil samples regularly, obtain indicators such as pollutant concentration through laboratory analysis, supplement the on-site monitoring data, and provide a basis for the comprehensive evaluation of the remediation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A schematic diagram of the method for targeted stimulation of indigenous microorganisms to repair organic contaminated sites based on negative pressure-enhanced infiltration according to the present invention;

[0050] Figure 2 The working principle diagram of the method for negative pressure-enhanced infiltration to target and stimulate indigenous microorganisms to repair organic contaminated sites;

[0051] Figure 3 The construction process flow chart of the method for negative pressure-enhanced infiltration and targeted stimulation of indigenous microorganisms to repair organic contaminated sites;

[0052] Description of the markings in the figure:

[0053] 1- grouting pipe, 2- grouting pump, 3- sealing membrane, 4- sand cushion, 5- vacuum pressure gauge, 6- sealing membrane buried trench, 7- plastic drain board, 8- water vapor separator, 9- vacuum pump, 10- exhaust gas processor, 11- monitoring sampling shaft, 12- integrated monitoring system. DETAILED DESCRIPTION

[0054] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0055] In order to overcome the defects of the existing in-situ remediation technology for organic pollutants, such as high energy consumption, poor effect, inability to reuse the remediated soil, and small scope of application, the present invention provides a method for remediating organic polluted sites based on negative pressure-promoted infiltration and targeted stimulation of indigenous microorganisms, which specifically includes:

[0056] (1) According to the actual situation of the contaminated site, select the activator, which includes nutrients, slow-release materials, and surfactants. In addition, carbon sources, inorganic salts, and growth factors can also be selected in the activator.

[0057] (2) Nutrients include nitrogen sources and phosphorus sources. According to the actual situation of the contaminated site, the nitrogen source can be selected from organic nitrogen sources (such as yeast extract, peptone, urea) and inorganic nitrogen sources (ammonium nitrogen, nitrate nitrogen). The phosphorus source can be selected from organic phosphorus sources (such as nucleic acids, phospholipids, beef extract) and inorganic phosphorus sources (phosphates, phosphate ions). The ratio of nitrogen source and phosphorus source follows 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, where the concentration of peptone is 6-12g / L and the concentration of beef extract is 1-4g / L.

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

[0059] (4) Surfactants can be selected from rhamnolipids, polysorbate 80, oily substances, lecithin, etc. If polysorbate 80 is selected, the optimal dosage is 100 mg / L-500 mg / L

[0060] (5) According to the site conditions, carbon sources (such as glucose, starch, glycerol, etc.), inorganic salts (Zn 2+ , Mn 2+、SO4 2- 、NO2 - Carbon sources provide energy and carbon elements for microorganisms, inorganic salts stimulate the growth and metabolism of indigenous microorganisms, and growth factors directly promote microbial activity.

[0061] (6) Use the above activator ratio and prepare it in the slurry storage tank of the organic contaminated site for standby use. Then deploy the negative pressure infiltration-promoting site remediation technical solution.

[0062] (7) A grouting pipe 1 is arranged in the polluted soil and groundwater, a grouting hole is arranged in the middle and lower part of the grouting pipe 1, and 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 substance is the activator proposed in the present invention;

[0063] (8) A vertical plastic drain board is installed at the central position equidistant from the surrounding grouting pipes, and a plastic drain board 7, a sand cushion layer 4, and a vacuum pump 9 are arranged in the contaminated site. A water vapor separator 8 and an exhaust gas processor 10 are installed to separate the water vapor of the extracted material and treat the exhaust gas, a negative pressure system is established for the contaminated site, and a sealing film buried trench 6 is opened; specifically, the spacing between the plastic drain boards is determined by the specific conditions of the contaminated site, and is generally 1.5-3.0 m.

[0064] (9) During the construction process, distributed optical fibers are buried along the plastic drain board 7 and the grouting pipe 1, and microfluidic chips are installed on the plastic drain 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 surface, and a monitoring sampling shaft 11 is set up. A vacuum pressure gauge 5 is installed at the grouting pipe 1, the monitoring sampling shaft 11, and the plastic drain board 7. The above detection data are uploaded to the integrated monitoring system 12 for analysis and processing.

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

[0066] (11) Turn on the vacuum pump 9 to apply negative pressure to the contaminated site, extract the formation 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 an obvious inflection point, and the readings of each vacuum gauge are -60 to -80 kPa and relatively stable, the first grouting is carried out. The grouting adopts the infiltration grouting method, and the grouting pressure is 50-250 kPa. During the grouting process, the vacuum pump 9 is continuously operated to maintain the vacuum pressure and seepage field in the formation. When the vacuum indication at the grouting point reaches -30 to -40 kPa, the vacuuming is stopped. When the vacuum indication at the grouting point is close to 0 and the vacuum indications in the field are all greater than -15 kPa, the grouting is terminated.

[0068] (13) Allow the site to stand for the indigenous microorganisms to multiply and degrade the pollutants. Use the monitoring system to monitor the biochemical oxygen demand of the site in real time to reflect the severity of the organic pollutants in the site. If the converted BOD5 (biochemical oxygen demand in five days) is greater than 60 mg / L, it means that the remediation has not been completed. At this time, if the dissolved oxygen content in the site is less than 6 mg / L, the activator needs to be re-injected.

[0069] Step (14) is 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 concentration meets the standard, remediation is stopped. If the concentration does not meet the standard, steps (11)-(13) are repeated.

[0070] Based on the above implementation modes, the present invention will be further described below in conjunction with more specific examples.

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

[0072] Embodiment 1:

[0073] For polycyclic aromatic hydrocarbons contaminated sites, this embodiment provides a method for repairing organic contaminated sites based on negative pressure-enhanced infiltration and targeted stimulation of indigenous microorganisms, which specifically includes:

[0074] (1) According to the actual situation of the contaminated site, select activators, which 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-sustained-release microsphere produced by embedding modification, in which the binder is paraffin, and the active ingredients are CaO2 and K2HPO4, respectively. The diameter of the sustained-release material ranges from 300 to 800 mm, and its concentration in the activator is 15 g / L. In the two prepared sustained-release materials, the mass ratio of the binder to the active ingredient is 5:1.

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

[0078] (5) According to the site conditions, carbon sources (such as glucose, starch, alcohol, etc.), inorganic salts (Zn 2+ , Mn 2+ 、SO4 2- 、NO2 -Carbon sources provide energy and carbon elements for microorganisms, inorganic salts stimulate the growth and metabolism of indigenous microorganisms, and growth factors directly promote microbial activity.

[0079] (6) Use the above activator ratio and prepare it in the slurry storage tank of the organic contaminated site for standby use. Then deploy the negative pressure infiltration-promoting site remediation technical solution.

[0080] (7) A grouting pipe 1 is arranged in the polluted soil and groundwater, a grouting hole is arranged in the middle and lower part of the grouting pipe 1, and 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 substance is the activator proposed in the present invention;

[0081] (8) A vertical plastic drain board is installed at the central position equidistant from the surrounding grouting pipes, and a plastic drain board 7, a sand cushion layer 4, and a vacuum pump 9 are arranged in the contaminated site. A water vapor separator 8 and an exhaust gas processor 10 are installed to separate the water vapor of the extracted material and treat the exhaust gas, a negative pressure system is established for the contaminated site, and a sealing film buried trench 6 is opened; specifically, the spacing between the plastic drain boards is about 2m.

[0082] (9) During the construction process, distributed optical fibers are buried along the plastic drain board 7 and the grouting pipe 1, and microfluidic chips are installed on the plastic drain 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 surface, and a monitoring sampling shaft 11 is set up. A vacuum pressure gauge 5 is installed at the grouting pipe 1, the monitoring sampling shaft 11, and the plastic drain board 7. The above detection data are uploaded to the integrated monitoring system 12 for analysis and processing.

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

[0084] (11) Turn on the vacuum pump 9 to apply negative pressure to the contaminated site, extract the formation 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 an obvious inflection point, and the readings of each vacuum gauge are about -60 to -80 kPa and relatively stable, the first grouting is carried out. The grouting adopts the infiltration grouting method, and the grouting pressure is about 150 kPa. During the grouting process, the vacuum pump 9 is continuously operated to maintain the vacuum pressure and seepage field in the formation. When the vacuum indication at the grouting point reaches about -30 to -40 kPa, the vacuuming is stopped. When the vacuum indication at the grouting point is close to 0 and the vacuum indications in the field are all greater than -15 kPa, the grouting is terminated.

[0086] (13) Allow the site to stand for the indigenous microorganisms to multiply and degrade the pollutants. Use the monitoring system to monitor the biochemical oxygen demand of the site in real time. If the converted BOD5 (biochemical oxygen demand in five days) is greater than 60 mg / L, it means that the remediation has not been completed. At this time, if the dissolved oxygen content in the site is less than 6 mg / L, the activator needs to be re-injected.

[0087] Step (14) is 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 concentration meets the standard, remediation is stopped. If the concentration does not meet the standard, steps (11)-(13) are repeated.

[0088] In general, the activator provided by the present invention can target and bind to the indigenous microorganisms in the site, provide them with the nutrients needed for growth, and promote the biodegradation of organic pollutants. At the same time, the present invention also designs a remediation method that can make the activator evenly distributed in the contaminated site under the negative pressure effect, so as to achieve more uniform and effective in-situ remediation. In addition, the present invention has also developed a set of integrated monitoring systems that can monitor the key indicators in the remediation process in real time, providing a basis for the evaluation and optimization of the remediation effect. Compared with traditional methods, the remediation scheme of the present invention is simple to operate and low in cost, while having a wide range of remediation, high efficiency, good effect, and no secondary pollution. It is worth mentioning that the method can also simultaneously complete the foundation improvement of the contaminated site, and can be widely used in the remediation of various organic contaminated sites. The present invention provides an innovative, efficient, and environmentally friendly in-situ organic contaminated site remediation scheme, which is of great significance for solving the shortcomings of current remediation technology.

[0089] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the scope of protection of the present invention.

Claims

1. An activator for targeted stimulation of indigenous microorganisms to repair organic pollutants, characterized in that: It includes nutrients, slow-release materials and surfactants, wherein the nutrients include nitrogen sources and / or phosphorus sources, the slow-release materials are composed of a binding material that is soluble in hydrophobic organic pollutants as an outer shell, and an active ingredient wrapped by the outer shell, and the active ingredient is a slow-release oxygen material, a slow-release buffer solution, or a combination of both.

2. The activator for targeted stimulation of indigenous microorganisms to repair organic pollutants according to claim 1, characterized in that: The nutrient is selected from one or more of yeast extract, peptone, urea, nitrate, nucleic acid, beef extract, phospholipids, and phosphate, and the added amount satisfies that when the activator is added to the contaminated site to be repaired, the molar ratio of C:N:P in the contaminated site is 100:(5-20):(0.5-1.5).

3. The activator for targeted stimulation of indigenous microorganisms to repair organic pollutants according to claim 1, characterized in that: The bonding material is paraffin; And / or, the slow-release oxygen material is one or both of CaO2 and MgO2; And / or, the sustained-release buffer solution contains K2HPO4, KH2PO4, organic acid, citric acid, Al 3+ One or more of the following; And / or, the particle size of the sustained-release material is 300-800 nm.

4. The activator for targeted stimulation of indigenous microorganisms to repair organic pollutants according to claim 1, characterized in that: The amount of the slow-release material added satisfies: when the activator is added to the contaminated site to be repaired, the oxygen concentration of the contaminated site reaches 8-12 mg / L; and the pH value of the contaminated site reaches 6-8.

5. The activator for targeted stimulation of indigenous microorganisms to repair organic pollutants according to claim 1, characterized in that: The surfactant is selected from one or more of rhamnolipid, polysorbate-80, oily substances, and lecithin, and its concentration in the activator is controlled to be 1-2.5 times the critical micelle concentration.

6. The activator for targeted stimulation of indigenous microorganisms to repair organic pollutants according to claim 1, characterized in that: It also includes one or more of carbon sources, inorganic salts, and growth factors; The carbon source is one or a combination of glucose, starch, and glycerol; The ions contained in the inorganic salt include Zn, which can improve the activity of microbial enzymes. 2+ and Mn 2+ , and SO4 can act as an electron acceptor 2- and NO2 - One or a combination of the above, wherein the concentration of the above in the activator is 0.01-1 mg / L; The growth factor is one or more of the vitamins or hormones that can directly promote the growth and metabolic activities of soil microorganisms, and the concentration of the growth factor in the activator is 10-20 mg / L.

7. A method for targeted stimulation of indigenous microorganisms to repair organic contaminated sites based on negative pressure-enhanced infiltration, characterized in that: The following steps are involved: (1) burying grouting pipes in the contaminated site to be repaired, and installing plastic drainage parts connected to the liquid extraction pipeline at the center of two adjacent grouting pipes, wherein the liquid extraction pipeline is also connected to the vacuum assembly; (2) turning on the vacuum assembly to transmit the negative pressure effect to the contaminated soil area through the plastic drainage piece, so that the pores in the contaminated soil area are in a negative pressure state; (3) injecting the activator as described in any one of claims 1 to 6 through a grouting pipe by means of infiltration grouting, and utilizing the negative pressure effect to allow the injected activator to fully penetrate the contaminated soil area; (4) After grouting is completed, the contaminated site is allowed to stand to complete the in situ bioremediation of the contaminated site.

8. The method of claim 7, wherein the method is characterized in that: The contaminated site to be repaired is also filled with a sand cushion layer, and a sealing film is further covered on the sand cushion layer.

9. The method of claim 7, wherein the method is characterized in that: In step (2), the negative pressure state satisfies: the vacuum gauge reading of the contaminated site area is stable at -60 kPa to -80 kPa; In step (3), the pressure of the infiltration grouting through the grouting pipe is controlled at 50-250 kPa; In step (4), the grouting is allowed to stand for 10-15 days.

10. A system for targeted stimulation of indigenous microorganisms to repair organic contaminated sites by negative pressure-promoted infiltration, which is used to implement the method according to claim 7, characterized in that: include: The sand cushion and sealing membrane are laid on the contaminated soil in sequence; A grouting pipe, a plastic drainage piece and a monitoring sampling shaft buried in the contaminated soil and extending out of the sand cushion layer at the top, the grouting pipe is also connected to an external grouting pump, and the plastic drainage piece is also connected to the vacuum pump through a liquid extraction pipeline; 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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