Electrothermal coupling remediation method for water and soil integrated treatment of organic combined pollution site and application

Abstract

The invention discloses an electrothermal coupling remediation method for water and soil integrated treatment of an organic polluted site, and belongs to the technical field of in-situ remediation of polluted sites. An electric field is arranged in a to-be-treated area, electric heating equipment is arranged between a cathode and an anode of the electric field, and a surface active agent added near the cathode and the anode, an oxidizing agent and a microbial electron acceptor are subjected to electrodialysis migration under the pulse electric impact effect of the electric field; and under the heating condition, desorption and dissolution of adsorbed pollutants are promoted, mixing collision with an activated oxidizing agent is promoted, electron acceptors conveyed by electromigration and heat synergistically improve the abundance and degradation activity of indigenous microorganism flora, soil residual and water-phase dissolved organic pollutants are synchronously degraded, and then electricity is utilized. And remediation is conducted in a dialysis, electromigration and thermal action coupling mode till the remediation target of the soil and the underground water is achieved, and water and soil integrated treatment on the organic pollution to-be-treated area is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-situ remediation of contaminated sites, and in particular relates to an electric-thermal coupling remediation method and application thereof for integrated water-soil management of organic composite contaminated sites. Background Art

[0002] Organic compound pollution is one of the common types of pollution in chemical contaminated sites, and it is often characterized by complex hydrogeological conditions, large differences in pollutant components, and frequent water-soil interactions. Among the compound organic pollutants, hydrophobic organic pollutants (HOCs) have strong adsorption in the soil, poor biodegradability, and are not easy to flow with pore water, resulting in a slow natural attenuation process and low contact reaction efficiency with remediation agents, making it difficult to achieve efficient remediation. At the same time, non-aqueous liquids such as benzene series and halogenated hydrocarbons are also common groundwater pollutants in chemical contaminated sites. Among them, light non-aqueous liquids migrate in the underground environment in the form of multiphase flow of liquid and gas, and soil-adsorbed pollutants can be driven by groundwater flow to migrate. High-density heavy non-aqueous liquids can penetrate the surface soil into deeper strata and form pollution pools. During the migration process, they are easily adsorbed by unsaturated low-permeability soil layers, and migrate upward under capillary action to cause lateral diffusion. The pollution pool formed in the saturated zone will also affect the high-permeability area through reverse diffusion. It can be seen that soil and groundwater are closely linked in ecological functions and are mutually causal in the pollution process. Separating the soil and groundwater remediation processes can easily lead to cross-contamination. If only groundwater is remediated, pollutants in the soil will re-enter the groundwater with precipitation leaching, groundwater level fluctuations, and leaching of non-aqueous phase liquids; if only soil is remediated, pollutants in groundwater will enter the soil with water level fluctuations or capillary action. The treatment of organic contaminated sites usually remediates soil and groundwater separately, so the synergy is poor, the consumption of chemicals and energy in the remediation process is too large, the potential secondary pollution problem is serious, and it is not green and sustainable. HOCs in low permeability formations have low in-situ remediation efficiency due to their strong adsorption and difficulty in biodegradation; non-aqueous phase liquids such as benzene series and halogenated hydrocarbons in groundwater are also difficult to miscible with water-soluble chemical / biological reagents due to their high hydrophobicity and strong fluidity. The remediation efficiency is low and there are problems such as tailing and rebound after remediation.

[0003] At present, the technologies that can be used for the integrated in-situ remediation of organically contaminated soil and groundwater mainly include gas injection-extraction method, microbial method, multiphase extraction method, in-situ chemical oxidation method, thermal remediation method, etc. However, the gas injection-extraction method mainly focuses on enhancing the volatilization and in-situ biodegradation of pollutants, and can be regarded as an enhanced in-situ microbial remediation technology. Both methods have problems such as long remediation cycle and unstable remediation effect; the remediation effect of multiphase extraction technology when applied to clay layers is limited, and the remediation effect for HOCs is poor; the chemical oxidation method has problems such as limited mass transfer in clay layers and difficulty in effectively activating oxidants in situ, which leads to large spatial differences in remediation efficiency; thermal remediation has high energy consumption, and when applied to the remediation of HOCs, it still needs to be supplemented by in-situ chemical oxidation technology, which further increases the remediation cost. Therefore, the coexistence of pollutants with different characteristics will significantly increase the complexity of site pollution, and it is difficult to achieve integrated water and soil management through a single technology. The electrokinetic remediation technology is not affected by soil heterogeneity and non-uniformity, and can be used for the simultaneous in-situ remediation of organically contaminated soil and groundwater. However, since the technology itself is difficult to achieve the desorption and degradation of HOCs, it is often coupled with surfactants, oxidants, and functional degradation microorganisms. For example, CN112872012B proposes injecting surfactants into the contaminated soil in a cathode transmission mode, arranging an advanced oxidation filler area with a mixture of biochar and persulfate as filler outside the anode, and when petroleum hydrocarbons are enriched in the advanced oxidation filler area, the inert anode is removed and the Fe anode is inserted in situ, and the inert cathode is moved toward the anode according to the migration of petroleum hydrocarbons, and then the power is turned on to continue the oxidation degradation. Although this method can effectively repair petroleum hydrocarbon contaminated soil, it does not have the pertinence of water and soil co-governance when pollutants of different characteristics coexist, and does not consider the migration effect of electrodialysis (movement from anode to cathode) on petroleum hydrocarbons, persulfates, etc. enriched in the advanced oxidation filler area. The average degradation rate of petroleum hydrocarbons in the advanced oxidation area is only 47%. In addition, in actual engineering applications, the construction of advanced oxidation zones requires a large amount of biochar, and the biochar that adsorbs petroleum hydrocarbons after use needs to be disposed of as hazardous waste. The movement of the inert cathode to the anode requires additional electrode well construction, all of which will significantly increase the energy consumption and cost of remediation. Summary of the invention

[0004] The purpose of the present invention is to provide an electric-thermal coupling remediation method and application for integrated water-soil management of organic composite contaminated sites.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The invention discloses an electrothermal coupling remediation method for integrated soil and water treatment of organic composite contaminated sites. An electric field is set in the area to be treated, and an electric heating device is set between the anode and cathode of the electric field. The pulse electric shock effect of the electric field is used to make the surfactant, oxidant and microbial electron acceptor added near the cathode and anode undergo electromigration and electrodialysis migration respectively, and promote the desorption, dissolution and mixed collision of adsorbed pollutants with activated oxidants under heating conditions. The electron acceptors transported by electromigration and thermal action synergistically improve the abundance and degradation activity of indigenous microbial flora, and the organic pollutants in the residual state in the soil and dissolved state in the water phase are synchronously degraded. Then, the remediation is carried out by coupling electrodialysis, electromigration and thermal action until the remediation goal of soil and groundwater is achieved, thereby realizing integrated soil and water treatment of the organic polluted area to be treated.

[0007] Further,

[0008] (1) A regular polygonal drilling range is set outside the repair area, and anode electrode wells are distributed at each vertex of the regular polygon. A cathode electrode well is drilled in the center of the regular polygon. A well pipe is inserted into each electrode well, and an electrolyte injection pipe and electrodes are inserted into the pipe in sequence. The electrodes are respectively connected to a pulsed DC power supply;

[0009] (2) drilling an electric heating well between the cathode electrode well and the anode electrode well, installing the electric heating well pipe, inserting the electric heating pipe and connecting it to the temperature control box;

[0010] (3) injecting a mixed solution of a surfactant and an oxidant into the electrolyte injection tube in the anode electrode well, and injecting a microbial electron acceptor aqueous solution into the electrolyte injection tube in the cathode electrode well;

[0011] (4) setting the pulsed DC electric field working potential and starting the pulsed DC power supply;

[0012] (5) After the surfactant and the oxidant migrate to the cathode electrode well, the pulsed DC power supply is cut off;

[0013] (6) Set the working temperature of the electric heating tube and start the temperature control box;

[0014] (7) After the oxidant is fully activated, cut off the power supply of the temperature control box;

[0015] (8) Repeat steps (3) to (7) until the repair target is reached.

[0016] The number of vertices of the regular polygon in step (1) is 3 to 9; the anode electrode well is a drilled hole at the vertex of the regular polygon, and the well spacing is 50 to 300 cm; the cathode electrode well is located in the central area of ​​the regular polygon; the depth of the electrode well exceeds the deepest pollution by 0.3 to 1.0 m; the electrode well pipe is a PVC slotted pipe with a bottom seal, and the gap between the well pipe and the drilled hole is filled with granular carbon or iron sand.

[0017] The apertures of the cathode and anode electrodes are 90 to 150 mm; the electrode well pipe is a PVC slotted pipe with a bottom seal (pipe diameter 73 mm to 141 mm, slot width 1 to 5 mm), and the gap between the slotted pipe and the drilled hole is filled with granular carbon or iron sand (3 to 10 mm); the anode is made of titanium or titanium alloy, the cathode is made of titanium, stainless steel or graphite, and the electrode diameters are all 30 to 50 mm; the electrolyte injection pipe is made of PVC or PBDE, with a pipe diameter of DN10 to DN40; the electrode and the electrolyte injection pipe can be inserted into the electrode well through a porous rubber plug with a thickness of 5 to 10 cm, the wellhead is sealed and the electrode and the electrolyte injection pipe are fixed, or concrete is directly used to seal the wellhead and fix the electrode and the electrolyte injection pipe; the pulsed DC power supply is a high-voltage and high-power power supply with continuously adjustable output, AC380V input, rated power 5 to 50kW, voltage 0 to 600V, and pulse frequency 100 to 10000Hz.

[0018] The electric heating well described in step (2) is located in the middle of the straight-line distance between the cathode electrode well and the anode electrode well, is a drilled hole, and has the same depth as the electrode well; the well pipe of the electric heating well is a stainless steel pipe with a sealed bottom, and the gap between the well pipe and the drilled hole is filled with bentonite, montmorillonite or kaolin.

[0019] The electric heating well hole (diameter 70-280mm) has the same depth as the electrode well; the electric heating well pipe is a bottom-sealed stainless steel pipe (DN50-DN250, outer diameter 60.3mm-273mm), which is 10-50cm longer than the electric heating pipe; the gap between the electric heating well pipe and the drilled hole is filled with bentonite, montmorillonite or kaolin; the electric heating pipe is a single-end heated stainless steel tubular electric heating element (voltage 380V, power 6-24kW), welded to the flange and equipped with a waterproof cover, with a pipe diameter of 30-80mm, and the heating medium is air; each electric heating well contains 1-6 electric heating pipes; the temperature control box has a rated voltage of 380V, a load power of 150KW, and multi-circuit intelligent adjustable constant temperature heating.

[0020] In step (3), the surfactant is a bio-based surfactant; the oxidant is potassium peroxymonosulfate or peroxydisulfate; the concentration of the surfactant in the mixed solution of the surfactant and the oxidant is 1 to 5 times the critical micelle concentration, and the concentration of the oxidant is 100 to 300 g / L;

[0021] Among them, the bio-based surfactant is one or more of anionic surfactants (including rhamnolipids, sophorolipids, etc.), non-ionic surfactants (including saponins, sorbitan fatty acid esters, etc.), and amphoteric surfactants (including betaine, amino acid type, etc.).

[0022] The microbial electron acceptor aqueous solution is a nitrate aqueous solution and / or a sulfate aqueous solution, with a nitrate concentration of 5-15 mg / L and a sulfate concentration of 50-250 mg / L.

[0023] The working potential of the pulsed DC electric field in step (4) is 100 to 200 V / m.

[0024] The time for the oxidant and surfactant to migrate to the cathode electrode well in step (5) is 5 to 45 days.

[0025] The working temperature of the electric heating tube in step (6) is 40-70°C.

[0026] The time required for complete activation of the oxidant in step (7) is 24 to 240 hours.

[0027] The present invention also provides an application of the electric-thermal coupling repair method in the integrated water-soil treatment of organic polluted sites.

[0028] Compared with the prior art, the present invention has the following advantages and technical effects:

[0029] Pulsed direct current has both the AC characteristics of effective heating and the DC characteristics of electrodynamic migration. In a pulse system using an on / off power supply, the power supply is also turned off during the off time, so energy consumption can be reduced by about 50%. While promoting the desorption of HOCs, it can also significantly shorten the time required for subsequent electric heat conduction heating, further reducing the overall remediation energy consumption. Using a mixed solvent of stable persulfate and environmentally friendly bio-based surfactant as the anolyte can avoid the meaningless loss of oxidants and surfactants on the one hand, and can also promote the desorption of HOCs from soil and improve the water solubility of HOCs and non-aqueous phase liquids through the "amphipatic" characteristics of the surfactant (containing both hydrophilic and lipophilic groups), thereby improving the contact reaction efficiency between dissolved organic pollutants in water and water-soluble persulfate. After the surfactant forms micelles in the aqueous solution, it can significantly increase the solubility of the originally insoluble or slightly soluble substances. However, at this time, the solute is not simply dissolved in the water, but is mixed or wrapped in the middle of the micelles formed by the surfactant. Under the combined effect of increased solubility and gas-liquid interface hindrance, the volatilization of the non-aqueous phase liquid is significantly inhibited, thereby avoiding the problems of polluted gas collection and deep disposal, tailing and rebound after repair. Under the action of low-temperature electrothermal conduction heating, persulfate is efficiently homogeneously activated, and organic pollutants dissolved in soil pore water and groundwater are effectively degraded. At the same time, the electron acceptors transported by electromigration are coupled with thermal effects, which significantly improve the growth and reproduction of indigenous microorganisms in the soil, the abundance of bacterial flora and the degradation activity, etc., and effectively degrade organic pollutants adsorbed in the soil. Therefore, the electrothermal coupling remediation method proposed in the present invention can realize green, low-energy, and efficient water-soil integrated management of organic polluted sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0031] Figure 1 The present invention discloses a laboratory simulation research device for injecting a mixed solution of a bio-based surfactant and persulfate (electrodialysis injection) and a microbial electron receptor (electromigration injection) into a pulse electric field; in the figure, (a) a schematic diagram of the device: 1-single pulse DC power supply, 2-peristaltic pump, 3-cathode, 4-cathode electrolysis chamber, 5-electrodialysis overflow outlet, 6-electrolyte storage tank, 7-nylon screen (20 mesh), 8-soil storage chamber, 9-anode electrolysis chamber, 10-anode, 11-anode electrolyte pump inlet tube, 12-anode electrolyte storage tank; (b) a cross-sectional schematic diagram of the device, a top view and the location of the sampling point.

[0032] Figure 2 The pulsed electric field of the present invention is used to electrodialyze the transport of bio-based surfactants and persulfate, and to electromigration transport of microbial electron acceptors; in the figure, (a) petroleum hydrocarbons (C 10 -C 40 ) content changes; (b) changes in persulfate content in the cathode electrolyte; (c) changes in sulfate and nitrate content in the anolyte; (d) spatial distribution of persulfate in the soil.

[0033] Figure 3 The present invention is a laboratory simulation research device for activating persulfate by electric heat conduction heating; in the figure, (a) schematic diagram of the device: 1-temperature control box, 2-electric heating rod, 3-electronic thermometer with an insertion depth of 12 cm, 4-electronic thermometer with an insertion depth of 6 cm, 5-soil storage chamber; (b) top view of the device.

[0034] Figure 4 The figure shows the oxidative degradation efficiency of organic pollutants in soil by persulfate activated by electric heat conduction heating of the present invention; in the figure, (a) deep soil temperature (12 cm); (b) shallow soil temperature (6 cm); (c) persulfate decomposition rate in deep soil; (d) persulfate decomposition rate in shallow soil; (e) variation of residual concentration of petroleum hydrocarbons in deep soil over time; (f) variation of residual concentration of petroleum hydrocarbons in shallow soil over time.

[0035] Figure 5This is a laboratory simulation research device for treating organic contaminated soil using the electrothermal coupling remediation method of the present invention; in the figure, (a) schematic diagram of the device: 1-temperature controller, 2-single-pulse DC power supply, 3-peristaltic pump, 4-anode electrolyte storage tank, 5-cathode electrolyte storage tank, 6-anode electrode well, 7-electric heating rod, 8-cathode electrode well, 9-electrolyte injection tube; (b) top view of the device and schematic diagram of the relative positions of sampling points.

[0036] Figure 6 This is the laboratory simulation repair effect of the electric-thermal coupling repair method of the present invention; in the figure, (a) the residual concentration of petroleum hydrocarbons in the soil; (b) the residual concentration of dichloromethane in the soil.

[0037] Figure 7 Schematic diagram of the layout of the actual application of the electrothermal coupling remediation method of the present invention in an organic contaminated site; in the figure, (a) is a schematic diagram of the on-site layout of the implementation process; and (b) is a schematic diagram of the plane layout.

[0038] Figure 8 The schematic diagram of the construction of the electrode well and the electric heating well when the electrothermal coupling remediation method of the present invention is actually applied in an organic contaminated site; in the figure, (a) electrode well; (b) electric heating well.

[0039] Fig. 9 This is the soil remediation effect of the electrothermal coupling remediation method of the present invention when it is actually applied in an organic polluted site; in the figure, (a) the residual concentration of trichloroethylene in the soil within the remediation range; (b) the residual concentration of petroleum hydrocarbons in the soil within the remediation range.

[0040] Fig.10 This is the groundwater remediation effect of the electrothermal coupling remediation method of the present invention when it is actually applied in an organic polluted site; in the figure, (a) dichloromethane concentration in groundwater within the remediation range; (b) trichloroethylene concentration in groundwater within the remediation range. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0043] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0044] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0045] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0046] The raw materials used in the following examples of the present invention are all commercially available.

[0047] The present invention uses electrodialysis to make the mixed solution of biological surfactant and oxidant migrate from the anode electrode well to the cathode electrode well, and the microbial electron acceptor migrate from the cathode electrode well to the anode electrode well, so that the material transmission efficiency is significantly improved under the electric shock of the high-power pulse power supply, and at the same time, a certain preheating effect is played on the soil; the soil adsorbed HOCs on the surfactant migration path are effectively desorbed, and the water solubility of the desorbed HOCs and the non-aqueous phase liquid in the soil pore water and groundwater is synchronously improved, and they are fully mixed and contacted with persulfate; the pulse power supply can also avoid the negative effects such as electrode polarization caused by continuous electrode reaction under continuous power supply conditions and sudden changes in soil acid-base conditions; on the basis of pulse electric field soil preheating, the low-temperature electric heat conduction heating time is significantly shortened, and the energy consumption is effectively reduced; under the heat effect, the HOCs desorption efficiency and the water solubility of pollutants in the soil pore water and groundwater are further improved, the persulfate is effectively activated, and the water-phase dissolved organic pollutants are oxidized and degraded; the electron acceptor and the heat effect synergistically improve the flora abundance and diversity of soil indigenous microorganisms, thereby improving the biodegradation efficiency of soil adsorbed organic pollutants. Under the combined effects of pollutant desorption and solubilization - sufficient mixing and contact of reactants - low-temperature thermal activation of persulfate - enhanced degradation by soil microorganisms, efficient and integrated water and soil management of organic contaminated sites can be achieved.

[0048] The following examples serve as further illustrations of the technical solutions of the present invention.

[0049] Example 1

[0050] Laboratory simulation research device for pulsed electric field injection of bio-based surfactant and persulfate mixture (electrodialysis injection) and microbial electron receptor (electromigration injection) Figure 1 As shown. The artificial petroleum hydrocarbon (C 10 -C 40 , 2600mg / kg) contaminated soil was loaded into the soil storage chamber. Before the experiment, the soil was adjusted to a saturated moisture content (46%) with deionized water. The soil filling height was 8cm and the density was 1.98g / cm 3 (about 3.2kg); a 20-mesh nylon screen is used to block the soil storage chamber and the electrolysis chamber to prevent soil particles from entering; the electrolyte in the anode chamber is an aqueous solution of a rhamnolipid surfactant with a concentration of 3 times the critical micelle concentration (pH = 9), and the electrolyte also contains 100g / L persulfate; the electrolyte in the cathode chamber is a mixed aqueous solution of sulfate (100mg / L) and nitrate (5mg / L) (pH = 5); a cylindrical titanium electrode with a length of 10cm and a diameter of 3cm is inserted into the anode and cathode electrolysis chambers through the reserved holes in the top cover and connected to the corresponding output ends of a single-pulse DC power supply; the experimental device is sealed with glass glue and the power supply is started; a parallel experiment is set up with a working potential of 150V / m and an injection time of 20 days.

[0051] In view of the strong adsorption of petroleum hydrocarbons, the time of significant change in the content of petroleum hydrocarbons in the cathode electrolyte was determined as the basis for rhamnolipid to reach the cathode electrolyte chamber; the persulfate content in the cathode electrolyte was tested by ultraviolet spectrophotometry; the sulfate and nitrate ions in the anolyte were tested by ion chromatography. The results showed that ( Figure 2 ), on the 5th day after the start of the experiment, high concentrations of petroleum hydrocarbons (18.3 mg / L) and persulfate (2.2 g / L) were detected in the cathode electrolyte at the same time, and high concentrations of nitrate (1.3 mg / L) and sulfate ions (3.8 mg / L) were detected in the anode electrolyte on the 1st and 2nd days after the start of the experiment, respectively; on the 5th day, the persulfate content in the soil was in the range of 9.0-38.8 g / kg (average content 26.2 g / kg); by the 15th day, the persulfate content in the soil was in the range of 41.7-50.8 g / kg (average content 46.5 g / kg), and the spatial difference was significantly reduced.

[0052] Example 2

[0053] Laboratory simulation research device for activation of persulfate by electric heat conduction heating Figure 3As shown, it consists of an organic glass soil chamber (40×40×20cm), an electric heat conduction heating device (with continuous temperature control and time control functions), a heating rod (15cm long, 2cm in diameter) and a digital thermometer. The artificial simulated contaminated soil and the filling method used in the experiment are the same as those in Example 1, except that the soil moisture content is adjusted to the saturated moisture content (46%) with a persulfate (100g / L) aqueous solution, and the final persulfate content in the soil is about 45.2g / kg. The working temperature of the heating rod is set to 60°C, and the changes in soil temperature at different positions (4, 9, 14, 19cm from the heating rod) and depths (6cm, 12cm) are monitored using an electronic thermometer. The residual concentration of petroleum hydrocarbons in the soil is determined.

[0054] The thermal properties of soil mainly depend on water content, porosity and composition. The thermal conductivity of each component is in the order of air < ​​dry soil < water < saturated soil. Therefore, when the air in the soil pores is replaced by water, the thermal conductivity will increase, that is, the heating effect of saturated soil is better than that of unsaturated soil. The water loss of the surface soil (6cm) is much more serious than that of the bottom soil (12cm), and it increases with the decrease of the distance from the heating rod. The results show that ( Figure 4 ), when the soil in the effective heating area (radius 9cm) changes from saturated to unsaturated, the temperature increment drops rapidly after 1.5h and shows a fluctuating downward trend; the soil can reach a stable temperature after 3h of heating, and the temperature continues to decrease with the increase of the distance from the heating rod. The persulfate activation efficiency in the effective heating area can reach 61.9% to 86.1% and 82.4% to 99.1% in shallow and deep soils, respectively, which can effectively degrade petroleum hydrocarbons in the soil, and its residual concentration is in the range of 696 to 808 mg / kg and 578 to 683 mg / kg, respectively, which is lower than the first category of land screening value (826 mg / kg) of the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)" (GB36600-2018).

[0055] Example 3

[0056] Based on the pulse electric field injection parameters and electrothermal conduction heating parameters obtained in Example 1 and Example 2, a simulation study on treating organic contaminated soil using an electrothermal coupling remediation method was carried out. The experimental device is as follows: Figure 5 As shown. Anode electrode wells are arranged in a regular hexagonal distribution in the restoration area (soil storage chamber) (the distance between anode wells is 50 cm), and cathode electrode wells are arranged in the central area. 10 -C 40, 2600 mg / kg) and dichloromethane (800 mg / kg) composite contaminated soil was placed in a soil storage chamber (120 cm in diameter and 50 cm in height) with a filling height of 45 cm. Before the experiment, the soil was adjusted to a saturated moisture content (46%) with deionized water and a soil density of 1.98 g / cm 3 (about 1000kg); the anode and cathode electrode well pipes are DN65 (outer diameter 73mm) PVC slotted pipes (slit width 2mm), 50cm long, sealed at the bottom, and wrapped with 20-mesh nylon mesh on the outside to prevent soil particles from entering the electrode well; the electrode well is sealed with a perforated rubber plug (thickness 5cm); the cathode and anode are titanium electrodes (length 52cm, diameter 3cm), the electrolyte injection pipe is made of PVC (length 30cm, diameter DN15), and is installed in the electrode well through the reserved hole of the perforated rubber plug; the cathode and anode are connected directly The corresponding output end of the current power supply; the electrolyte injection tube is connected to the peristaltic pump; the electric heating well pipe is a DN50 (outer diameter 60.3mm) stainless steel pipe, 50cm long, and sealed at the bottom; the electric heating well is sealed with a perforated rubber plug (thickness 5cm); an electric heating tube is arranged in each electric heating well, which is a single-end heated stainless steel tubular electric heating element (voltage 380V, power 12kW), welded to the flange and equipped with a waterproof cover, with a tube diameter of 30mm and a length of 40cm. The heating medium is air, and it is installed in the electric heating well through the reserved hole of the perforated rubber plug.

[0057] Specifically:

[0058] (1) Drill anode electrode wells distributed in a regular polygon at the periphery of the repair area, drill cathode electrode wells in the center of the regular polygon, install well pipes, insert electrodes and electrolyte injection pipes, and connect pulsed DC power supply;

[0059] (2) drilling an electric heating well between the cathode electrode well and the anode electrode well, installing the electric heating well pipe, inserting the electric heating pipe and connecting it to the temperature control box;

[0060] (3) a mixed solution of surfactant and oxidant is injected into the anode electrode well, and an aqueous solution of microbial electron acceptors is injected into the cathode electrode well;

[0061] (4) setting the pulsed DC electric field working potential and starting the pulsed DC power supply;

[0062] (5) After the surfactant and the oxidant migrate to the cathode electrode well, the pulsed DC power supply is cut off;

[0063] (6) Set the working temperature of the electric heating tube and start the temperature control box;

[0064] (7) After the oxidant is fully activated, cut off the power supply of the temperature control box;

[0065] (8) Repeat steps (3) to (7) until the repair target is reached.

[0066] The step (3) is the first operation stage: the electrolyte in the anode well is an aqueous solution of a rhamnolipid surfactant with a concentration of 3 times the critical micelle concentration (pH = 9), and the electrolyte contains 100 g / L of persulfate; the electrolyte in the cathode well is a mixed aqueous solution of sulfate (100 mg / L) and nitrate (5 mg / L) (pH = 5).

[0067] The step (4) is to set the pulsed DC electric field working potential to 150 V / m and start the DC power supply.

[0068] In the step (5), the injection time of the oxidant and the surfactant is 7 days; during this period, the electrolyte in the anode electrode well is replenished by the electrolyte injection tube, and the accumulated electrodialysis flow of the cathode electrode well is extracted by the extraction tube.

[0069] The step (6) is the second operation stage: cutting off the pulse DC power supply, setting the working temperature of the electric heating tube to 60° C., and starting the temperature control box.

[0070] In the step (7), the time required for the oxidant to be fully activated is 18 hours.

[0071] After the experiment, soil samples were collected in three layers (first layer: 0-15cm; second layer: 15-30cm; third layer 30-45cm) for testing. The results showed that the average content of petroleum hydrocarbons (324-638mg / kg) and dichloromethane (32.7-75.5mg / kg) in the soil was 470mg / kg and 53.5mg / kg respectively. Figure 6 ), which are lower than the first-class land use screening value in GB36600-2018 (petroleum hydrocarbon C 10 -C 40 : 826mg / kg, dichloromethane: 94mg / kg).

[0072] Example 4

[0073] The actual field application of the electric-thermal coupling remediation method for integrated water and soil treatment of organic contaminated sites was carried out. A real organic contaminated site was selected for the test. The soil in the test area was contaminated with trichloroethylene (2.6-9.8 mg / kg) and petroleum hydrocarbons (1356-2854 mg / kg), and the groundwater was contaminated with dichloromethane (1350-2436 μg / L) and trichloroethylene (952-1469 μg / L). The stable groundwater level in the test area was about 1.4 m, and the maximum soil contamination depth reached 5 m, with the pollution mainly concentrated at 3-5 m.

[0074] For details on how to implement site applications, see Figure 7 , the schematic diagram of the construction of the electrode well and the heating well is as follows Figure 8As shown. In the test area, 30 drilling rigs were used to drill holes of anode electrode wells (diameter 120mm, hole spacing 300cm) distributed in a regular quadrilateral. A total of 9 anode electrode wells were drilled to form 4 regular quadrilateral areas; cathode electrode well holes were drilled in the center area of ​​each regular quadrilateral, with a hole diameter of 120mm; electric heating well holes were drilled in the middle of the straight-line distance between the cathode electrode well and the anode electrode well, with a hole diameter of 100mm; the depth of the anode electrode well, cathode electrode well, and electric heating well holes were all 5.5m; the well pipes of the anode and cathode electrode wells were DN100 (outer diameter 114.3mm) PVC slotted pipes (slit width 2mm), 5.5m long, sealed at the bottom, and wrapped with 20-mesh nylon mesh on the outside to prevent soil particles from entering the electrode well; the gap between the well pipe and the drilled hole was filled with 3mm granular carbon; the cathode and anode were both titanium electrodes (length 5.7m, diameter 5cm), and the electrolyte The injection pipe is a PVC pipe with a diameter of DN25 (external diameter 33.4mm, length 2m); the electrode and electrolyte injection pipes are installed in the electrode well through the reserved holes of the perforated rubber plug (thickness 10cm), and the electrode well is sealed with the perforated rubber plug; the cathode and the anode are connected to the corresponding output ends of the DC power supply; the electrolyte injection pipe is connected to the injection pump; the well pipe of the electric heating well is a DN80 stainless steel pipe (external diameter 88.9mm, length 5.5m), and the bottom is sealed; the gap between the well pipe of the electric heating well and the drilled hole is filled with bentonite; one electric heating pipe is arranged in each electric heating well, which is a single-end heated stainless steel tubular electric heating element (voltage 380V, power 24kW), welded on the flange and equipped with a waterproof cover, with a pipe diameter of 60mm, a length of 5m, and the heating medium is air; the electric heating pipe is installed in the electric heating well through the reserved holes of the perforated rubber plug (thickness 10cm), and the electric heating well is sealed with the perforated rubber plug.

[0075] Specifically:

[0076] (1) Drill anode electrode wells distributed in a regular polygon at the periphery of the repair area, drill cathode electrode wells in the center of the regular polygon, install well pipes, insert electrodes and electrolyte injection pipes, and connect pulsed DC power supply;

[0077] (2) drilling an electric heating well between the cathode electrode well and the anode electrode well, installing the electric heating well pipe, inserting the electric heating pipe and connecting it to the temperature control box;

[0078] (3) a mixed solution of surfactant and oxidant is injected into the anode electrode well, and an aqueous solution of microbial electron acceptors is injected into the cathode electrode well;

[0079] (4) setting the pulsed DC electric field working potential and starting the pulsed DC power supply;

[0080] (5) After the surfactant and the oxidant migrate to the cathode electrode well, the pulsed DC power supply is cut off;

[0081] (6) Set the working temperature of the electric heating tube and start the temperature control box;

[0082] (7) After the oxidant is fully activated, cut off the power supply of the temperature control box;

[0083] (8) Repeat steps (3) to (7) until the repair target is reached.

[0084] The step (3) is the first operation stage: the electrolyte in the anode well is an aqueous solution of a rhamnolipid surfactant with a concentration of 3 times the critical micelle concentration (pH = 9), and the electrolyte also contains 150 g / L of persulfate; the electrolyte in the cathode well is a mixed aqueous solution of sulfate (150 mg / L) and nitrate (10 mg / L) (pH = 5).

[0085] The step (4) is to set the pulsed DC electric field working potential to 100 V / m and start the DC power supply.

[0086] In the step (5), the injection time of the oxidant and the surfactant is 21 days; during this period, the electrolyte in the anode electrode well is replenished by the electrolyte injection tube, and the accumulated electrodialysis flow of the cathode electrode well is extracted by the extraction tube.

[0087] The step (6) is the second operation stage: cutting off the pulse DC power supply, setting the working temperature of the electric heating tube to 60° C., and starting the temperature control box.

[0088] In the step (7), the time required for complete activation of the oxidant is 96 hours.

[0089] After the test, in accordance with the Technical Guidelines for Investigation of Soil Pollution Status of Construction Land (HJ 25.1-2019), the Technical Guidelines for Risk Control and Soil Remediation Effect Evaluation of Polluted Land (HJ 25.5-2018), and the Technical Guidelines for Groundwater Remediation and Risk Control of Polluted Land (HJ 25.6-2019), soil and groundwater samples were collected within the test area for testing to evaluate the remediation effect. Fig. 9 As shown in the figure, the average contents of trichloroethylene (0.26-0.62 mg / kg) and petroleum hydrocarbons (329-569 mg / kg) in the soil within the remediation range were 0.44 mg / kg and 431 mg / kg, respectively, both lower than the screening values ​​for Class I land use in GB36600-2018 (trichloroethylene 0.7 mg / kg, petroleum hydrocarbons C 10 -C 40 :826mg / kg); Fig.10As shown, the average contents of dichloromethane (128.6-392.7μg / L) and trichloroethylene (42.8-174.6μg / L) in groundwater within the remediation scope were 299.4μg / L and 107.7μg / L, respectively, which continuously and stably met the Class IV water quality standards of the "Groundwater Quality Standard" (GB / T 14848-2017) (dichloromethane: ≤500μg / L, trichloroethylene: ≤210μg / L).

[0090] In summary, the present invention proposes for the first time to solve the above-mentioned problems by using electric mass transfer-soil flushing-chemical oxidation combined remediation technology. It does not require the construction of additional remediation functional areas, all structures are completed at one time, and the mass transfer effect of electric remediation is fully utilized to complete the transfer of multiple functional reagents, and can achieve efficient desorption and solubilization of pollutants, uniform in-situ activation of oxidants, and improved degradation activity of indigenous microorganisms. Specifically, based on the low-energy mass transfer and thermal effect of the pulsed DC electric field, the surfactant can promote the desorption of HOCs on the migration path and improve its water solubility, and the oxidizing agent can be efficiently dispersed, and the soil can be preheated without causing a large amount of decomposition of the oxidant. At the same time, based on the electrical migration effect of the DC electric field, the electron acceptors required for microbial degradation of organic pollutants are transported to the stratum. Non-toxic and biodegradable bio-based surfactants and their compound reagents have a good solubilization effect on HOCs such as polycyclic aromatic hydrocarbons. Compared with other oxidants, persulfate has high stability, good water solubility, and weak affinity for natural organic matter. When compounded with bio-based surfactants, it will not produce degradation consumption when not activated. Electrical heat conduction is not affected by formation permeability and heterogeneity, and has been successfully used as an in-situ thermal activation method for persulfate in the remediation of organically contaminated soils.

[0091] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An electrothermal coupling remediation method for integrated water and soil management of organic composite contaminated sites, characterized in that: An electric field is set up in the area to be treated, and an electric heating device is set between the anode and cathode of the electric field. The pulse electric shock of the electric field is used to make the surfactant, oxidant and microbial electron acceptor added near the cathode and anode undergo electrodialysis migration, and the desorption, dissolution and mixed collision of adsorbed pollutants with activated oxidants are promoted under heating conditions. The electron acceptors transported by electromigration and thermal action synergistically improve the abundance and degradation activity of indigenous microbial flora, and the organic pollutants residual in the soil and dissolved in the water phase are degraded synchronously. Then, the remediation is carried out by coupling electrodialysis, electromigration and thermal action until the remediation goal of soil and groundwater is achieved, thereby realizing integrated water and soil management in the organic pollution area to be treated.

2. The electric-thermal coupling remediation method for integrated water-soil management of organic composite contaminated sites according to claim 1 is characterized in that: (1) A regular polygonal drilling range is set outside the repair area, and anode electrode wells are distributed at each vertex of the regular polygon. A cathode electrode well is drilled in the center of the regular polygon. A well pipe is inserted into each electrode well, and an electrolyte injection pipe and electrodes are inserted into the pipe in sequence. The electrodes are respectively connected to a pulsed DC power supply; (2) drilling an electric heating well between the cathode electrode well and the anode electrode well, installing the electric heating well pipe, inserting the electric heating pipe and connecting it to the temperature control box; (3) injecting a mixed solution of a surfactant and an oxidant into the electrolyte injection tube in the anode electrode well, and injecting a microbial electron acceptor aqueous solution into the electrolyte injection tube in the cathode electrode well; (4) setting the pulsed DC electric field working potential and starting the pulsed DC power supply; (5) After the surfactant and the oxidant migrate to the cathode electrode well, the pulsed DC power supply is cut off; (6) Set the working temperature of the electric heating tube and start the temperature control box; (7) After the oxidant is fully activated, cut off the power supply of the temperature control box; (8) Repeat steps (3) to (7) until the repair target is reached.

3. The electric-thermal coupling remediation method for integrated water-soil management of organic composite contaminated sites according to claim 2 is characterized in that: The number of vertices of the regular polygon in step (1) is 3 to 9; the anode electrode well is a drilled hole at the vertex of the regular polygon, and the well spacing is 50 to 300 cm; the cathode electrode well is located in the central area of ​​the regular polygon; the depth of the electrode well exceeds the deepest pollution by 0.3 to 1.0 m; the electrode well pipe is a PVC slotted pipe with a bottom seal, and the gap between the well pipe and the drilled hole is filled with granular carbon or iron sand.

4. The electric-thermal coupling remediation method for integrated water-soil management of organic composite contaminated sites according to claim 2 is characterized in that: The electric heating well described in step (2) is located in the middle of the straight-line distance between the cathode electrode well and the anode electrode well, is a drilled hole, and has the same depth as the electrode well; the well pipe of the electric heating well is a stainless steel pipe with a sealed bottom, and the gap between the well pipe and the drilled hole is filled with bentonite, montmorillonite or kaolin.

5. The electric-thermal coupling remediation method for integrated water-soil management of organic composite contaminated sites according to claim 2 is characterized in that: The surfactant in step (3) is a bio-based surfactant; the oxidant is potassium permonosulfate complex salt or peroxydisulfate; the concentration of the surfactant in the mixed solution of the surfactant and the oxidant is 1 to 5 times the critical micelle concentration, and the concentration of the oxidant is 100 to 300 g / L; the microbial electron acceptor aqueous solution is a nitrate aqueous solution and / or a sulfate aqueous solution, the nitrate concentration is 5-15 mg / L, and the sulfate concentration is 50-250 mg / L.

6. The electric-thermal coupling remediation method for integrated water-soil management of organic composite contaminated sites according to claim 2 is characterized in that: The working potential of the pulsed DC electric field in step (4) is 100 to 200 V / m.

7. The electric-thermal coupling remediation method for integrated water-soil management of organic composite contaminated sites according to claim 2 is characterized in that: The time for the oxidant and surfactant to migrate to the cathode electrode well in step (5) is 5 to 45 days.

8. The electric-thermal coupling remediation method for integrated water-soil management of organic composite contaminated sites according to claim 2 is characterized in that: The working temperature of the electric heating tube in step (6) is 40-70°C.

9. The electric-thermal coupling remediation method for integrated water-soil management of organic composite contaminated sites according to claim 2 is characterized in that: The time required for complete activation of the oxidant in step (7) is 24 to 240 hours.

10. Use of the method according to claim 1 in the integrated water and soil treatment of organic compound contaminated sites.

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