Electrochemical enhanced biological slurry repairing method for refractory organic contaminated soil and application of electrochemical enhanced biological slurry repairing method

Abstract

The invention belongs to the technical field of ex-situ remediation of degradation-resistant organic contaminated soil in contaminated sites, and particularly relates to an electrochemical enhanced biological slurry remediation method for degradation-resistant organic contaminated soil and application. The method comprises the following steps: doping a heterogeneous catalyst in the preparation process of a slurry sample of polluted soil, uniformly mixing, applying a constant-current weak direct-current electric field, injecting an oxidant solution, enabling an anode to effectively release ferrous ions, and carrying out electrochemical reaction by taking the heterogeneous catalyst as a particle electrode, so as to oxidize and decompose refractory organic pollutants in a to-be-treated sample; and then applying a constant-voltage weak direct-current electric field to the sample and injecting a degrading bacterial agent, and treating residues under the action of electrical stimulation so as to realize comprehensive removal of refractory organic pollutants in the sample. According to the method, degradation of refractory organic pollutants is achieved, and meanwhile the ecological function of the restored soil is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of ex situ remediation of hard-to-degrade organic contaminated soil in contaminated sites, and specifically relates to an electrochemically enhanced bio-slurry remediation method for hard-to-degrade organic contaminated soil and an application thereof. Background Art

[0002] According to the principle of organic contaminated soil remediation technology, it can be divided into physical, chemical and biological technologies. Physical and chemical technologies are generally suitable for high-concentration pollution control, with quick results but high treatment costs and the risk of secondary pollution; biological technology is more suitable for medium and low-concentration pollution control, with advantages such as low cost, wide application range and environmental friendliness, but the remediation cycle is long, and it takes 1 to 2 months even when the remediation efficiency is the highest. Therefore, how to improve the efficiency of bioremediation and shorten the remediation cycle is the key to breaking through the technical bottleneck. The biological mud method can enhance the effectiveness of nutrients, electron acceptors and other additives, and improve the degradation efficiency of pollutants. However, there are still shortcomings such as slow mass transfer between functional strains and pollutants, low contact reaction efficiency, and low degradation efficiency of macromolecular pollutants. When applied to the remediation of difficult-to-degrade organic contaminated soil, the remediation efficiency and cycle still cannot meet the requirements. The remediation and management of contaminated sites in my country are mostly aimed at land transfer and development and utilization, and the selection of remediation technology tends to be "short, flat and fast" physical and chemical technologies. Based on the analysis of actual remediation projects of contaminated sites in my country from 2010 to 2018, the proportion of remediation using in-situ technology is about 56%, and 44% of contaminated sites are still mainly remediated ex situ. For soils that are difficult to degrade organic pollutants (semi-volatile organic pollutants, persistent organic pollutants contaminated soils), the ex situ remediation technologies used mainly include chemical oxidation / reduction, thermal desorption, cement kiln co-disposal and other high-chemical, high-energy input / high-carbon emission technologies, and biodegradation remediation technology is basically not used.

[0003] Electro-Fenton technology is an electrochemical method to generate Fe 2+ and H 2 O 2As a continuous source of Fenton reagents to degrade organic pollutants, it has been successfully applied to various sewage treatments. The electro-Fenton reaction can be used as a pretreatment technology for biological mud reactions to repair soil contaminated by refractory organic pollutants. However, the electro-Fenton process relies on the gain and loss of electrons to produce free radicals (hydroxyl radicals) to achieve the degradation of target pollutants. The quality of the medium's mass transfer performance directly affects the free radical yield and its contact reaction efficiency with pollutants, significantly affecting the remediation effect. Moreover, the Fenton reaction can generally only be carried out under acidic conditions, is greatly affected by pH, and has a narrow applicable pH range. In addition, the removal efficiency of hydroxyl radicals for soil adsorbed organic pollutants is very low, so it is not suitable for the remediation of high-concentration refractory contaminated soils. Due to its poor substrate specificity, the natural organic matter released in the mud will significantly consume hydroxyl radicals, which will not only lead to low removal efficiency of target pollutants, but also significantly damage the integrity of soil ecological functions. The research results show that the electro-Fenton-bioslurry method (electro-Fenton reaction for 6 hours, bioslurry reaction for 66 hours) can efficiently remediate pyrene (144.70 mg / kg) contaminated soil (removal rate of 91.02%); however, when the same reaction conditions are applied to high-concentration polycyclic aromatic hydrocarbons (PAHs, total concentration of about 5635.6 mg / kg, high-ring PAHs accounting for 85.8%) contaminated soil in actual sites, the removal rate is negatively correlated with the number of PAHs rings, and the overall removal rate is only 25.68%.

[0004] Electrochemical enhanced oxidation technology can continuously release ferrous ions from the iron anode to catalyze oxidants such as persulfate. It can also utilize the redox cycle and electron transfer promotion of the electrochemical reaction process to improve the catalytic activity of heterogeneous catalysts. It can effectively activate oxidants under low energy consumption conditions, and utilize the generated strong oxidizing substances such as sulfate radicals and hydroxyl radicals to achieve rapid and efficient decomposition of macromolecular pollutants in mud in a short time. At the same time, weak DC electric fields also have the effects of mass transfer enhancement and microbial degradation activity stimulation, which can achieve efficient biomineralization removal of organic pollutants and their degradation intermediates. Standardized soil restoration can maintain its ecological functions and realize resource utilization. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of limited mass transfer, low degradation efficiency of macromolecular organic pollutants, and long remediation cycle in traditional bioslurry methods, and to propose an electrochemically enhanced bioslurry remediation method for difficult-to-degrade organic contaminated soil.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The invention discloses an electrochemical enhanced bio-mud remediation method for hard-to-degrade organic contaminated soil. In the process of preparing mud samples of contaminated soil, a heterogeneous catalyst is added. After mixing, a constant-current weak direct current electric field is applied and an oxidant solution is injected, so that the anode effectively releases ferrous ions. At the same time, an electrochemical reaction occurs with the heterogeneous catalyst as a microparticle electrode, thereby oxidizing and decomposing the hard-to-degrade organic pollutants in the sample to be treated. Then, a constant-voltage weak direct current electric field is applied to the sample and a degradation bacterial agent is injected. Under the action of electrical stimulation, the residue is treated to achieve comprehensive removal of the hard-to-degrade organic pollutants in the sample.

[0008] The refractory organic pollutants in the soil are high-ring polycyclic aromatic hydrocarbons, petroleum, etc.

[0009] The heterogeneous catalyst is one or more of biochar, iron carbon, and iron oxide, and the blending amount is 0.5% to 2% of the dry weight of the mud soil; the oxidant solution is a potassium permonosulfate aqueous solution and / or a sodium peroxydisulfate aqueous solution, with a concentration of 10 to 200 g / L, and a total dosage of 1% to 10% of the mud volume; the current used to apply a constant current weak DC electric field is 30 to 300 mA, and the treatment reaction time is 30 to 180 min.

[0010] The degradation bacterial agent is an aqueous solution of one or more strains of Pseudomonas, Bacillus, Exiguobacterium, Arthrobacter, Rhodococcus, Micrococcus, and Coxsackie, and the colony count in the aqueous solution is 1×10 7 ~1×10 9 cfu / L, and the total dosage is 0.1% to 5% of the mud volume; when adding the degradation bacterial agent, a constant voltage weak DC electric field is applied, the working potential is 0.1 to 0.5V / cm, and the electrode polarity is switched, and the weak electric stimulation microbial degradation reaction time is 72 to 480h.

[0011] Further,

[0012] (1) An anode and a cathode are installed in a mud reactor and connected to the output terminals of a DC power supply respectively;

[0013] (2) installing the oxidant solution and the functional degradation bacteria solution injection pipe to the top cover interface of the mud reactor;

[0014] (3) Pre-prepare a slurry sample of high-concentration refractory organic contaminated soil, add a heterogeneous catalyst, mix well, and inject into a reactor;

[0015] (4) setting the DC power supply to a constant current mode and setting the electrochemical enhanced oxidation working current;

[0016] (5) starting the DC power supply and the oxidant solution injection pump;

[0017] (6) Complete oxidant solution pumping and electrochemical enhanced oxidation reaction, and adjust mud pH;

[0018] (7) Adjust the DC power supply to the constant voltage mode, switch the electrode polarity, and set the working potential for weak electrical stimulation of microbial degradation;

[0019] (8) starting the DC power supply and the degradation agent injection pump;

[0020] (9) Complete the pumping of functional degradation bacterial solution and weak electrical stimulation of microbial degradation reaction;

[0021] (10) Mud and water separation, water reuse for mud preparation, and soil resource utilization.

[0022] The top of the mud reactor (11) is provided with a mud injection pipe (2), an oxidant injection pipe (3), a degradation agent injection pipe (4), and a mounting hole for carrying a cathode (8) and an anode (9), and an agitator (1) is inserted; the oxidant injection pipe (3) is connected to the oxidant solution storage tank (6) through a pipeline, and the degradation agent injection pipe (4) is connected to the degradation agent storage tank (7) through a pipeline; a mud discharge pipe valve (13) is provided at the bottom of the mud reactor (11); the mud discharge pipe valve (13) is connected to a mud pump (14) and a horizontal spiral sedimentation centrifuge (15) in sequence through a pipeline;

[0023] The pipeline between the oxidant injection pipe (3) and the oxidant solution storage tank (6), and the pipeline between the degradation bacteria injection pipe (4) and the degradation bacteria storage tank (7) are provided with a high-flow peristaltic pump; the high-flow peristaltic pump has a flow rate of 0 to 1.2 m 3 / h adjustable.

[0024] The mud reactor is a vertical tank, made of stainless steel and lined with polytetrafluoroethylene, with a volume of 0.1 to 10 m 3 The top of the tank body is equipped with a top cover with different interfaces, and a paddle stirrer (steel-lined polytetrafluoroethylene stirring paddle) is provided for stirring the reaction process, with a stirring diameter of 50-200 cm, a stirring shaft diameter of 5-20 cm, a blade width of 4-30 cm, and a blade thickness of 1-5 cm; at the same time, the top cover is provided with an electrode mounting hole and an injection pipe interface, for the installation of electrodes, oxidant solution and bacterial solution injection pipes respectively; the anode is an iron electrode, and the cathode can be selected from graphite, titanium, boron-doped diamond and other materials, with an electrode diameter of 10-60 mm; the injection pipe is made of silica gel with an inner diameter of 10-25 mm; the anode and cathode pass-through wires are connected to a DC power supply, which has both constant current and constant voltage operation functions, a DC output current of 0-1A, a DC output voltage of 0-200V, and 0-rated value continuously adjustable;

[0025] The volume ratio of water to contaminated soil in the slurry in step (3) is 3:1 to 6:1; the water is tap water or recycled water;

[0026] The oxidant solution in step (6) is continuously pumped into the mud reactor (11) for a pumping time of 20 to 170 minutes; and the pH of the mud is adjusted to 7.0 to 7.5 after the electrochemical enhanced oxidation reaction.

[0027] In step (7), the electrode polarity is switched, that is, the initial anode becomes the cathode, and the initial cathode becomes the anode; the working potential of weak electrical stimulation microbial degradation is 0.1 to 0.5 V / cm.

[0028] The degradation bacterial agent in step (9) is pumped into the slurry reactor (11) by intermittent pumping, with an initial pumping time of 10 to 60 minutes, and then pumped once every 72 hours, with each pumping time of 10 to 60 minutes.

[0029] In step (10), the mud and water separation can be carried out by a horizontal spiral sedimentation centrifuge, a mud separator, etc.; the soil resource utilization includes backfilling, planting, greening, etc.

[0030] The present invention also provides an application of an electrochemical enhanced bio-slurry remediation method for refractory organic contaminated soil in the ex situ remediation of high-concentration organic contaminated soil in actual sites.

[0031] Compared with the prior art, the present invention has the following advantages and technical effects:

[0032] The present invention integrates the advantages of electrochemical enhanced oxidation technology and electric stimulation microbial degradation technology by means of staged reaction, and can overcome the problems of complex molecular structure, poor water solubility, and difficulty in being degraded by microorganisms of macromolecular organic pollutants in mud reactors. In the mud preparation process of hard-to-degrade organic polluted soil, a heterogeneous catalyst is added. In the first stage, constant current weak direct current is used to promote the release of ferrous ions from the iron anode, the redox cycle and electron transfer of the heterogeneous catalyst, and the injected persulfate (permonosulfate or peroxydisulfate) is efficiently activated. Based on the strong oxidative active species such as sulfate radicals and hydroxyl radicals generated, macromolecular organic pollutants are rapidly oxidized and decomposed; in the second stage, the mass transfer and interaction between nutrients, electron acceptors, functional degradation strains and pollutants in the mud reactor are effectively enhanced by a constant voltage weak potential direct current electric field, which significantly stimulates the degradation activity of microorganisms, and efficiently mineralizes and degrades residual organic pollutants and degrades intermediate products.

[0033] The iron anode continuously releases the activator (ferrous ion), avoiding the meaningless loss of oxidant caused by the simultaneous addition of a large amount of oxidant and activator, the self-quenching of a large amount of free radicals produced instantaneously, and the resulting low efficiency of pollutant decomposition. Under the promotion of redox cycle and electron transfer in the electrochemical reaction process, the heterogeneous catalyst can efficiently utilize the oxidant, significantly improving the efficiency of agent use and reaction efficiency. Under the mass transfer promotion of the electric field, the combination of homogeneous activation of the oxidant and heterogeneous activation can improve the contact reaction efficiency of free radicals with adsorbed and dissolved pollutants in the mud system, and significantly accelerate the oxidative decomposition of macromolecular organic pollutants. The efficient decomposition of highly toxic macromolecular pollutants creates good environmental conditions for subsequent electrically stimulated microbial degradation reactions, avoiding their toxicity to functional strains and inhibitory effects on degradation functions, and significantly improving the biodegradation efficiency and shortening the repair cycle without significantly increasing energy consumption. In addition, the repaired soil has no oxidants and highly toxic degradation intermediates remaining, which will not significantly affect the soil physical and chemical properties and fertility indicators, and can serve agricultural production, greening and other planting purposes again, realizing resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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:

[0035] Figure 1 Schematic diagram of an electrochemical enhanced biological mud reactor provided in an embodiment of the present invention. In which, 1-agitator; 2-mud injection pipe; 3-oxidant injection pipe; 4-functional degradation agent injection pipe; 5-large flow peristaltic pump; 6-oxidant solution storage tank; 7-functional degradation agent storage tank; 8-graphite cathode; 9-iron anode; 10-steel lined polytetrafluoroethylene stirring paddle; 11-mud reactor; 12-polytetrafluoroethylene lining; 13-mud discharge pipe valve; 14-mud pump; 15-horizontal spiral sedimentation centrifuge.

[0036] Figure 2 The changes of the iron ion content (a) and peroxymonosulfate concentration (b) in the reaction system over time under different DC current intensities.

[0037] Figure 3 To investigate the electrochemically enhanced oxidation degradation efficiency and residual amount of petroleum pollutants in contaminated soil.

[0038] Figure 4 To investigate the efficiency and residual amount of electro-stimulated microbial degradation of petroleum pollutants in contaminated soil. DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] The raw materials used in the following examples of the present invention are all commercially available.

[0045] The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil proposed in the present invention uses persulfate (monosulfate or disulfate) as an oxidant, which has the advantages of good stability, weak affinity for natural organic matter, and a wide applicable pH range, which are superior to Fenton's reagent. The sulfate radicals generated by activation have strong resistance to natural organic matter and ions in the soil. The scavenging ability of natural organic matter to hydroxyl radicals (~10 4 (mgC / L) -1 ·s -1 ) is higher than sulfate radical (~10 3 (mgC / L) -1 ·s -1) by an order of magnitude. Constant weak direct current is used to promote the release of ferrous ions at the iron anode, the redox cycle and electron transfer of the heterogeneous catalyst, and the simultaneous and efficient decomposition of adsorbed and dissolved macromolecular pollutants is achieved by combining homogeneous and heterogeneous oxidant activation; then it is switched to a constant voltage weak potential direct current electric field to enhance the mass transfer and interaction between nutrients, electron acceptors, functional degradation strains and pollutants in the mud reactor, stimulate the degradation activity of microorganisms, and achieve efficient mineralization and degradation of residual organic pollutants and degradation intermediates. Switching the electrode polarity can terminate the Fe 2+ Release, avoid affecting the physical and chemical properties of the soil, and protect the ecological functions of the soil.

[0046] The following examples serve as further illustrations of the technical solutions of the present invention.

[0047] Example 1

[0048] (1) Experimental soil

[0049] The test soil is clean silty clay, which is naturally air-dried after removing gravel and dead branches and passed through a 20-mesh sieve. Basic physical and chemical properties of the soil: pH = 7.6, conductivity 245.0μS / cm, organic matter content 58.6g / kg, cation exchange capacity 15.9cmol / kg. Soil particle composition: sand particles (>0.05mm) 11.3%, powder particles (0.002-0.05mm) 21.4%, clay particles (<0.002mm) 67.3%. Artificial simulated contaminated soil was prepared with Shengli Oilfield crude oil (alkanes 59.7%, aromatics 26.4%, and colloidal asphaltene 13.9%). The crude oil was dissolved in chloroform and evenly sprayed on the clean soil. The pollution concentration was set to 5000mg / kg. It was left in a fume hood for 45 days, and was stirred continuously during the period to ensure that the chloroform was completely volatilized and the pollutants were evenly distributed. The measured concentration of petroleum pollutants was about 4870mg / kg.

[0050] (2) Experimental setup

[0051] The schematic diagram of the mud reactor used in the electrochemical enhanced biological mud remediation method is shown in Figure 1 The top of the mud reactor (11) is provided with a mud injection pipe (2), an oxidant injection pipe (3), a degradation agent injection pipe (4), and mounting holes for carrying a cathode (8) and an anode (9), and an agitator (1) is inserted; the oxidant injection pipe (3) is connected to an oxidant solution storage tank (6) through a pipeline, and the degradation agent injection pipe (4) is connected to a degradation agent storage tank (7) through a pipeline; a mud discharge pipe valve (13) is provided at the bottom of the mud reactor (11); the mud discharge pipe valve (13) is connected to a mud pump (14) and a horizontal spiral sedimentation centrifuge (15) in sequence through pipelines;

[0052] The pipeline between the oxidant injection pipe (3) and the oxidant solution storage tank (6), and the pipeline between the degradation bacteria injection pipe (4) and the degradation bacteria storage tank (7) are provided with a high-flow peristaltic pump; the high-flow peristaltic pump has a flow rate of 0 to 1.2 m 3 / h adjustable.

[0053] The mud reactor is a vertical tank, made of stainless steel and lined with polytetrafluoroethylene, with a volume of 0.001m 3 The top of the tank body is equipped with a top cover with different interfaces, and a paddle stirrer (steel-lined polytetrafluoroethylene stirring paddle) is provided for stirring the reaction process, and the steel-lined polytetrafluoroethylene stirring paddle (stirring diameter 10cm, stirring shaft diameter 2cm, blade width 3cm, blade thickness 0.5cm); at the same time, the top cover is provided with an electrode mounting hole and an injection pipe interface, which are respectively provided for the installation of electrodes, oxidant solution and bacterial solution injection pipes; the anode is an iron electrode, and the cathode can be selected from graphite, titanium, boron-doped diamond and other materials, and the electrode diameter is 10-60mm; the injection pipe is made of silicone with an inner diameter of 10-25mm; the anode and cathode pass-through wires are connected to a DC power supply, and the DC power supply has both constant current and constant voltage operation functions, the DC output current is 0-1A, the DC output voltage is 0-200V, and 0-rated value is continuously adjustable; oxidant solution storage tank (500mL), iron anode (diameter 10mm), graphite cathode (diameter 10mm), degradation bacterial agent storage tank (500mL), etc.

[0054] (3) Experimental design and procedures

[0055] 1) Changes in permonosulfate content under homogeneous and heterogeneous activation conditions

[0056] 500 mL of 50 g / L potassium permonosulfate aqueous solution was added to the reactor, and 5 g of iron-carbon catalyst was added at the same time. The current of the reaction system was set to 100 mA, 150 mA, and 300 mA. The reaction was performed once under each current condition, and the reaction time was 70 min. The reaction solution was collected regularly to test the iron ion content and persulfate concentration, and to examine the change of the iron ion release of the anode over time and the activation of persulfate.

[0057] The iron content in the reaction solution was tested according to the "Determination of 65 Elements in Water Quality by Inductively Coupled Plasma Mass Spectrometry" (HJ 700-2014). The peroxymonosulfate concentration was tested by potassium iodide colorimetry. Specifically, 0.1 mL of the reaction solution after filtration (0.22 μm fiber filter membrane) was added to a solution containing 5 mL of potassium iodide (250 g / L) and 2.5 mL of NaHCO 3 The (25 g / L) solution was placed in a 15 mL centrifuge tube and after color development for 15 min, the color was measured using a UV-visible spectrophotometer at a wavelength of 352 nm.

[0058] like Figure 2As shown in the figure, the ferrous ion content in the system increases with the increase of current and the extension of power-on time, and the release amount is proportional to the current intensity; the concentration of persulfate in the system decreases with the extension of reaction time, and is almost consumed after 60 minutes of reaction. The results show that the release of ferrous ions by the iron anode combined with iron-carbon heterogeneous catalysis can effectively activate persulfate.

[0059] 2) Electrochemical enhanced bioslurry remediation method

[0060] The contaminated soil was prepared into a slurry (water-soil ratio 4:1, pH value 7.2), totaling 0.8L (containing about 0.28kg of contaminated soil), and 2.8g of iron-carbon catalyst (about 1% of the dry weight of the contaminated soil) was added. After uniform mixing, the slurry was injected into the reaction vessel through a slurry injection tube, and the top cover was installed; the working electrode was connected to a DC power supply, the steel-lined polytetrafluoroethylene stirring paddle was connected to the stirrer, and the permonosulfate injection tube and the bacterial liquid injection tube were connected to the top cover interface.

[0061] The first reaction stage: the DC power supply is set to constant current mode, and the electrochemical enhanced oxidation working current is set to 100mA; the DC power supply and the permonosulfate solution injection pump are started, the permonosulfate concentration is 50g / L, the flow rate is set to 0.8mL / min, the pumping time is 50min, and the total dosage (40mL) is about 5% of the mud volume; the electrochemical enhanced oxidation reaction time is 60min; after the reaction, the pH of the mud is adjusted to 7.5.

[0062] The second reaction stage: adjust the DC power supply to the constant voltage mode, switch the electrode polarity, set the weak electric stimulation microbial degradation working potential to 0.3 V / cm; start the DC power supply and the functional degradation bacterial solution injection pump, the degradation bacterial agent is a mixed bacterial solution of Rhodococcus, Bacillus, Exiguobacterium, Arthrobacter, and Coxsackie (each strain is activated in a conventional manner and then centrifuged to collect the precipitate, and then made into a suspension stock solution with sterile water, and the concentration is controlled at about 8×10 9 cfu / L), and the stock solution of each strain was diluted to about 2×10 8 cfu / L, and the colony count after mixing in equal proportions was about 2×10 8 cfu / L working solution; weak electrical stimulation microbial degradation reaction time is 240h, bacterial liquid pumping flow rate is set at 0.4mL / min, initial pumping time is 10min, and then pumping once every 72h (82min, 154min, 226min of reaction) The total dosage (16mL) is about 2% of the mud volume. After the reaction is completed, the mud-water mixture is transferred to a centrifuge tube, and the mud-water separation is carried out by a refrigerated centrifuge, and the pollutant content in the separated water and soil is tested respectively.

[0063] (4) Experimental results

[0064] like Figure 3As shown in the figure, after 60 minutes of electrochemical enhanced oxidation reaction, the removal efficiency of petroleum pollutants in the soil was about 36.5%, and the residual concentration was about 3092.5 mg / L; because the functional degradation microorganisms need time to adapt to the reaction environment and electric field conditions, the biodegradation efficiency of petroleum pollutants was low before 48 hours. With the batch addition of functional bacterial agents, the degradation efficiency continued to increase with the extension of treatment time. At the end of the experiment, the removal efficiency of petroleum pollutants in the soil can reach 91.0%, the residual concentration is about 438.3 mg / L, and no petroleum pollutants were detected in the separated water. The results show that the content of petroleum pollutants in the soil after remediation is lower than the first type of land screening value (petroleum hydrocarbon C10-C40: 826 mg / kg) in the "Standards for Soil Pollution Risk Control for Construction Land of Soil Environmental Quality (Trial)" (GB36600-2018), achieving the remediation goal; at the same time, the separated water does not contain pollutants and can be reused in the mud preparation process of contaminated soil.

[0065] Example 2

[0066] (1) Experimental soil

[0067] The clean soil used for the test was the same as that in Example 1. The crude oil from Shengli Oilfield was used to prepare artificial simulated contaminated soil, and the contamination concentration was set to 10000 mg / kg. The concentration of petroleum pollutants in the soil was measured to be about 9920 mg / kg.

[0068] (2) Experimental setup

[0069] Same as Example 1.

[0070] (3) Experimental design and procedures

[0071] The contaminated soil was prepared into a slurry (water-soil ratio 4:1, pH value 7.2), totaling 0.8L (containing about 0.28kg of contaminated soil), and 4.2g of iron-carbon catalyst (about 1.5% of the dry weight of the contaminated soil) was added. After uniform mixing, the slurry was injected into the reaction vessel through a slurry injection tube, and the top cover was installed; the working electrode was connected to a DC power supply, the steel-lined polytetrafluoroethylene stirring paddle was connected to the stirrer, and the permonosulfate injection tube and the bacterial liquid injection tube were connected to the top cover interface.

[0072] The first reaction stage: the DC power supply is set to constant current mode, and the electrochemical enhanced oxidation working current is set to 100 mA; the DC power supply and the permonosulfate solution injection pump are started, the permonosulfate concentration is 200 g / L, the flow rate is set to 0.5 mL / min, the pumping time is 80 min, and the total dosage (40 mL) is approximately 5% of the mud volume; the electrochemical enhanced oxidation reaction time is 90 min; after the reaction, the pH of the mud is adjusted to 7.5.

[0073] The second reaction stage: adjust the DC power supply to the constant voltage mode, switch the electrode polarity, set the weak electric stimulation microbial degradation working potential to 0.3 V / cm; start the DC power supply and the functional degradation bacterial solution injection pump, the functional degradation bacterial solution is a mixed bacterial solution of Rhodococcus, Bacillus, Exiguobacterium, Arthrobacter, and Coxsackie (each strain is activated in a conventional manner and then centrifuged to collect the precipitate, and then prepared into a suspension with sterile water, and the concentration is controlled at about 8×10 9 cfu / L), and the stock solution of each strain was diluted to about 4×10 8 cfu / L, and the colony count after mixing in equal proportions was about 4×10 8 cfu / L working solution; weak electrical stimulation microbial degradation reaction time is 240h, bacterial liquid pumping flow rate is set at 0.4mL / min, initial pumping time is 10min, and then pumping once every 72h (82min, 154min, 226min of reaction) The total dosage (16mL) is about 2% of the mud volume. After the reaction is completed, the mud-water mixture is transferred to a centrifuge tube, and the mud-water separation is carried out by a refrigerated centrifuge, and the pollutant content in the separated water and soil is tested respectively.

[0074] (4) Experimental results

[0075] like Figure 4 As shown in the figure, after 60 minutes of electrochemical enhanced oxidation reaction, the removal efficiency of petroleum pollutants in the soil was about 46.4%, and the residual concentration was about 5327.0 mg / L; after the electro-stimulated microbial degradation reaction, the removal efficiency of petroleum pollutants in the soil could reach 95.2%, and the residual concentration was about 476.2 mg / L, and no petroleum pollutants were detected in the separated water. The results show that the content of petroleum pollutants in the soil after remediation is lower than the screening value of the first category of land use in GB36600-2018, achieving the remediation goal; at the same time, the separated water does not contain pollutants and can be reused in the mud preparation process of contaminated soil.

[0076] Example 3

[0077] (1) Experimental soil

[0078] The test soil was collected from a contaminated site of an oil refinery. The soil contained high concentrations of petroleum hydrocarbons (C10-C40, 8300 mg / kg), polycyclic aromatic hydrocarbons (benzo(a)anthracene: 37.6 mg / kg, benzo(a)pyrene: 5.7 mg / kg, 836mg / kg, naphthalene: 58.9mg / kg) complex pollutants.

[0079] (2) Experimental setup

[0080] Electrochemically enhanced bioslurry reactor Figure 1As shown, it mainly includes a constant voltage / constant current dual-mode DC power supply (operating voltage range 0-200V), a stirrer (top entry, 0-150rpm adjustable), a large flow peristaltic pump (flow rate 0-1.2m 3 / h adjustable), oxidant solution storage tank (20L), iron anode (diameter 40mm), graphite cathode (diameter 40mm), steel-lined polytetrafluoroethylene stirring paddle (stirring diameter 50cm, stirring shaft diameter 5cm, blade width 4cm, blade thickness 1cm), mud reactor (0.6m diameter stainless steel lined polytetrafluoroethylene tank, volume about 120L (0.12m 3 )), functional degradation bacterial agent storage tank (20L), etc.

[0081] (3) Experimental design and procedures

[0082] The contaminated soil was prepared into slurry (water-soil ratio 4:1, pH value 7.5), totaling 100L (containing about 37.5kg of contaminated soil), and 0.75kg of iron-carbon catalyst (about 2% of the dry weight of the contaminated soil) was added. After uniform mixing, the slurry was injected into the reaction vessel through a slurry injection tube, and the top cover was installed; the working electrode was connected to a DC power supply, the steel-lined polytetrafluoroethylene stirring paddle was connected to the stirrer, and the persulfate injection tube and the bacterial liquid injection tube were connected to the top cover interface.

[0083] The first reaction stage: the DC power supply is set to constant current mode, and the electrochemical enhanced oxidation working current is set to 150mA; the DC power supply and the persulfate solution injection pump are started, the persulfate concentration is 200g / L, the flow rate is set to 0.07L / min, the pumping time is 120min, and the total dosage (8.4L) is approximately 8.4% of the mud volume; the electrochemical enhanced oxidation reaction time is 130min; after the reaction, the pH of the mud is adjusted to 7.5.

[0084] The second reaction stage: adjust the DC power supply to the constant voltage mode, switch the electrode polarity, set the weak electric stimulation microbial degradation working potential to 0.3 V / cm; start the DC power supply and the functional degradation bacterial solution injection pump, the functional degradation bacterial solution is a mixed bacterial solution of Rhodococcus, Bacillus, Exiguobacterium, Arthrobacter, and Coxsackie (each strain is activated in a conventional manner and then centrifuged to collect the precipitate, and then prepared into a suspension with sterile water, and the concentration is controlled at about 8×10 9 cfu / L), and the stock solution of each strain was diluted to about 8×10 8 cfu / L, and the colony count after mixing in equal proportions was about 8×10 8cfu / L working solution; weak electric stimulation microbial degradation reaction time is 360h, bacterial liquid pumping flow rate is set at 0.11L / min, initial pumping time is 10min, and then pumping is performed every 72h (82h, 154h, 226h, 298h of reaction). The total dosage (5.5L) is about 5% of the mud volume. After the reaction, the mud and water are separated by a horizontal spiral sedimentation centrifuge, and the pollutant content in the separated water and soil is tested respectively.

[0085] (4) Experimental results

[0086] As shown in Table 1, the removal efficiency of various pollutants after the first stage of electrochemical enhanced oxidation reaction is in the range of 51.9% to 64.2%; after the second stage of electro-stimulated microbial degradation reaction, the removal efficiency of various pollutants is in the range of 91.1% to 95.2%; the residual concentration of pollutants in the soil is lower than the first category of land use screening value of GB36600-2018, achieving the remediation goal. At the same time, the separated water does not contain pollutants and can be reused in the mud preparation process.

[0087] Table 1 Pollutant concentrations in the soil of a refinery contaminated site, soil residual concentrations after remediation, and remediation efficiency

[0088]

[0089] Example 4

[0090] (1) Experimental soil

[0091] The test soil was collected from a coking pollution site. The soil was contaminated with high concentrations of PAHs, mainly high-ring PAHs, including benzo(a)anthracene (82.7 mg / kg), benzo(a)pyrene (7.3 mg / kg), benzo(b)fluoranthene (57.9 mg / kg), dibenzo(a,h)anthracene (8.6 mg / kg), and indeno(1,2,3-cd)pyrene (42.5 mg / kg).

[0092] (2) Experimental setup

[0093] Same as Example 3.

[0094] (3) Experimental design and procedures

[0095] The contaminated soil was prepared into slurry (water-soil ratio 4:1, pH value 7.5), totaling 100L (containing about 37.5kg of contaminated soil), and 0.375kg of iron-carbon catalyst (about 1% of the dry weight of the contaminated soil) was added. After uniform mixing, the slurry was injected into the reaction vessel through a slurry injection tube, and the top cover was installed; the working electrode was connected to a DC power supply, the steel-lined polytetrafluoroethylene stirring paddle was connected to the stirrer, and the persulfate injection tube and the bacterial liquid injection tube were connected to the top cover interface.

[0096] The first reaction stage: the DC power supply is set to constant current mode, and the electrochemical enhanced oxidation working current is set to 150mA; the DC power supply and the persulfate solution injection pump are started, the persulfate concentration is 50g / L, the flow rate is set to 0.075L / min, the pumping time is 80min, and the total dosage (6L) is about 6% of the mud volume; the electrochemical enhanced oxidation reaction time is 90min; after the reaction, the pH of the mud is adjusted to 7.5.

[0097] The second reaction stage: adjust the DC power supply to the constant voltage mode, switch the electrode polarity, set the weak electric stimulation microbial degradation working potential to 0.3 V / cm; start the DC power supply and the functional degradation bacterial solution injection pump, the functional degradation bacterial solution is a mixed bacterial solution of Rhodococcus, Bacillus, Exiguobacterium, Arthrobacter, and Coxsackie (each strain is activated in a conventional manner and then centrifuged to collect the precipitate, and then prepared into a suspension with sterile water, and the concentration is controlled at about 8×10 9 cfu / L), and the stock solution of each strain was diluted to about 4×10 8 cfu / L, and the colony count after mixing in equal proportions was about 4×10 8 cfu / L working solution; weak electric stimulation microbial degradation reaction time is 240h, bacterial liquid pumping flow rate is set at 0.055L / min, initial pumping time is 10min, and then pumping is performed every 72h (82h, 154h, 226h of reaction). The total dosage (2.2L) is about 2% of the mud volume. After the reaction, the mud and water are separated by a horizontal spiral sedimentation centrifuge, and the pollutant content in the separated water and soil is tested respectively.

[0098] (4) Experimental results

[0099] As shown in Table 2, the removal efficiency of various pollutants after electrochemical enhanced oxidation reaction is in the range of 45.6% to 51.7%; after electrical stimulation of microbial degradation reaction, the removal efficiency of various pollutants is in the range of 91.5% to 94.9%; the residual concentration of pollutants in the soil is lower than the first category of land use screening value of GB36600-2018, achieving the remediation goal. At the same time, the separated water does not contain pollutants and can be reused in the mud preparation process.

[0100] Table 2 Pollutant concentrations in the soil of a coking contaminated site, soil residual concentrations after remediation, and remediation efficiency

[0101]

[0102] 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 electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil, characterized in that During the preparation of mud samples of contaminated soil, heterogeneous catalysts are added. After mixing, a constant current weak DC electric field is applied and an oxidant solution is injected, so that the anode can effectively release ferrous ions. At the same time, the heterogeneous catalyst acts as a microparticle electrode to undergo an electrochemical reaction, thereby oxidizing and decomposing the difficult-to-degrade organic pollutants in the sample to be treated. Then, a constant voltage weak DC electric field is applied to the sample and a degrading bacterial agent is injected. Under the action of electrical stimulation, the residues are treated to achieve comprehensive removal of the difficult-to-degrade organic pollutants in the sample.

2. The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil according to claim 1, characterized in that: The refractory organic pollutants in the soil are high-ring polycyclic aromatic hydrocarbons, petroleum, etc.

3. The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil according to claim 1, characterized in that: The heterogeneous catalyst is one or more of biochar, iron carbon, and iron oxide, and the blending amount is 0.5% to 2% of the dry weight of the mud soil; the oxidant solution is a potassium permonosulfate aqueous solution and / or a sodium peroxydisulfate aqueous solution, with a concentration of 10 to 200 g / L, and a total dosage of 1% to 10% of the mud volume; the current used to apply a constant current weak DC electric field is 30 to 300 mA, and the treatment reaction time is 30 to 180 min.

4. The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil according to claim 1, characterized in that: The degradation bacterial agent is an aqueous solution of one or more strains of Pseudomonas, Bacillus, Exiguobacterium, Arthrobacter, Rhodococcus, Micrococcus, and Coxsackie, and the colony count in the aqueous solution is 1×10 7 ~1×10 9 cfu / L, and the total dosage is 0.1% to 5% of the mud volume; when adding the degradation bacterial agent, a constant voltage weak DC electric field is applied, the working potential is 0.1 to 0.5V / cm, and the electrode polarity is switched, and the weak electric stimulation microbial degradation reaction time is 72 to 480h.

5. The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil according to any one of claims 1 to 4, characterized in that: (1) An anode and a cathode are installed in a mud reactor and connected to the output terminals of a DC power supply respectively; (2) installing the oxidant solution and the functional degradation bacteria solution injection pipe to the top cover interface of the mud reactor; (3) Pre-prepare a slurry sample of high-concentration refractory organic contaminated soil, add a heterogeneous catalyst, mix well, and inject into a reactor; (4) setting the DC power supply to a constant current mode and setting the electrochemical enhanced oxidation working current; (5) starting the DC power supply and the oxidant solution injection pump; (6) Complete oxidant solution pumping and electrochemical enhanced oxidation reaction, and adjust mud pH; (7) Adjust the DC power supply to the constant voltage mode, switch the electrode polarity, and set the working potential for weak electrical stimulation of microbial degradation; (8) starting the DC power supply and the degradation agent injection pump; (9) Complete the pumping of functional degradation bacterial solution and weak electrical stimulation of microbial degradation reaction; (10) Mud and water separation, water reuse for mud preparation, and soil resource utilization.

6. The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil according to claim 5, characterized in that: A mud injection pipe (2), an oxidant injection pipe (3), a degradation agent injection pipe (4), and a mounting hole for carrying a cathode (8) and an anode (9) are arranged on the top of the mud reactor (11), and a stirrer (1) is inserted; the oxidant injection pipe (3) is connected to an oxidant solution storage tank (6) through a pipeline, and the degradation agent injection pipe (4) is connected to a degradation agent storage tank (7) through a pipeline; a mud discharge pipe valve (13) is arranged at the bottom of the mud reactor (11); the mud discharge pipe valve (13) is connected to a mud pump (14) and a horizontal spiral sedimentation centrifuge (15) in sequence through a pipeline; The pipeline between the oxidant injection pipe (3) and the oxidant solution storage tank (6), and the pipeline between the degradation bacteria agent injection pipe (4) and the degradation bacteria agent storage tank (7) are provided with a large flow peristaltic pump.

7. The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil according to claim 5, characterized in that: The volume ratio of water to contaminated soil in the slurry in step (3) is 3:1 to 6:

1.

8. The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil according to claim 5 or 6, characterized in that: The oxidant solution in step (6) is continuously pumped into the mud reactor (11) for a pumping time of 20 to 170 minutes; and the pH of the mud is adjusted to 7.0 to 7.5 after the electrochemical enhanced oxidation reaction.

9. The electrochemical enhanced bioslurry remediation method for refractory organic contaminated soil according to claim 5 or 6, characterized in that: The degradation bacterial agent in step (9) is pumped into the slurry reactor (11) by intermittent pumping, with an initial pumping time of 10 to 60 minutes, and then pumped once every 72 hours, with each pumping time of 10 to 60 minutes.

10. An application of the method according to claim 1, characterized in that: The method is applied in ex situ remediation of high-concentration organically contaminated soil in actual sites.

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