Electric ultrasonic-assisted PRB (permeable reactive barrier) in-situ microbial remediation device for composite pollutants in soil and underground water

Abstract

The utility model provides an electric ultrasonic-assisted PRB in-situ microbial remediation device for soil and underground water composite pollutants, which comprises a device main body and a deionized water conical flask, the deionized water conical flask is communicated with a peristaltic pump through a water inlet pipeline, and the water outlet end of the peristaltic pump is communicated to one side of the device main body through the water inlet pipeline. A water outlet pipeline is arranged on the other side of the device main body, the water outlet pipeline is communicated to the recovery liquid conical flask, the device main body comprises a PRB remediation device, an electric remediation device and an ultrasonic remediation device, and combined contaminated soil is arranged in the device main body. The PRB remediation device comprises a PRB first filling material layer and a PRB second filling material layer which are arranged at the downstream of the composite contaminated soil, the ultrasonic remediation device comprises an ultrasonic vibration rod arranged in the PRB first filling material layer, and the ultrasonic vibration rod is connected with an ultrasonic module power supply. According to the utility model, the physical-chemical-biological combined effect is utilized, so that the pollutant mass transfer repair efficiency is improved.

Description

Technical Field

[0001] This utility model relates to the field of groundwater and soil remediation technology, specifically an electric ultrasonic-assisted PRB in-situ microbial remediation device for complex pollutants in soil and groundwater. Background Technology

[0002] Surface water and soil systems are generally subject to the interaction of various pollutants. Among them, heavy metal chromium (Cr(VI)) pollution mainly comes from industrial production such as chromium mining, printing and dyeing, leather tanning, and electroplating, while organic pollutant tetracycline (TC) mainly comes from production activities such as medical activities, livestock farming, and pharmaceutical production.

[0003] Currently, the mainstream methods for remediating groundwater containing multiple pollutants include pump-treatment technology and permeable reactive barrier (PRB) technology. The former involves pumping contaminated groundwater to the surface through wells and treating it using physical, chemical, or biological methods. The treated water can then be reinjected into the ground or discharged into surface water bodies. However, its drawbacks include long remediation cycles, high labor costs, and a tendency for tailing effects to occur later in the remediation process. The latter, permeable reactive barriers, are installed underground. As contaminated groundwater passes through the barrier, pollutants are removed through adsorption, oxidation-reduction, precipitation, or biodegradation. This allows for long-term operation and low maintenance costs. Therefore, compared to the former, permeable reactive barriers have a promising future in soil and groundwater remediation due to their lower construction cost and long-term operation without external forces. However, permeable reactive barriers also face challenges such as clogging and passivation of the reactive packing material and the need to improve the remediation efficiency for multiple pollutants. Utility Model Content

[0004] To address the shortcomings of the existing technology, this invention provides an electric ultrasonic-assisted PRB in-situ microbial remediation device for complex pollutants in soil and groundwater. This device reduces the problem of clogging of the reaction filler, promotes the directional migration of in-situ pollutants to the remediation area, and improves the remediation efficiency of complex pollution.

[0005] The technical solution provided by this utility model is as follows: A device for in-situ microbial remediation of soil and groundwater complex pollutants using electrically powered and ultrasonically assisted PRB (Polymer Proton Remediation) includes a main body and a deionized water conical flask. The deionized water conical flask is connected to a peristaltic pump via an inlet pipe. The outlet of the peristaltic pump is connected to one side of the main body via the inlet pipe. An outlet pipe is provided on the other side of the main body and is connected to a recovery liquid conical flask. The main body includes a PRB remediation device, an electrically powered remediation device, and an ultrasonic remediation device. The main body contains complex contaminated soil. The PRB remediation device includes a first PRB filling material layer and a second PRB filling material layer located downstream of the complex contaminated soil. The ultrasonic remediation device includes an ultrasonic vibrating rod located in the first PRB filling material layer. The ultrasonic vibrating rod is connected to an ultrasonic module power supply.

[0006] Furthermore, the electric repair device includes two graphite electrodes and an external DC power supply. The graphite electrodes include an anode and a cathode, and the external DC power supply is connected between the anode and cathode graphite electrodes.

[0007] Furthermore, an external DC power supply is applied to both sides of the contaminated soil and the remediation area. An electrode chamber is set on the outside of the graphite electrode, with the cathode upstream and the anode downstream.

[0008] Furthermore, simulated groundwater aquifer areas are provided on both sides of the main body of the device, and electrode chambers are distributed on both sides of the groundwater aquifer areas. A layer of quartz sand is filled between the groundwater aquifer areas and the electrode chambers to isolate them with a filter screen.

[0009] Furthermore, the simulated groundwater aquifer area is 30cm×50cm×10cm, of which the PRB area is 30cm×15cm×10cm on the side near the anode, and the remaining part is filled with composite contaminated soil. The electrode chamber areas distributed on both sides of the groundwater aquifer area are 30cm×10cm×10cm. The groundwater aquifer area and the electrode chamber area are filled with a 30cm×3cm×10cm quartz sand layer, which is separated by a 0.5mm nylon filter screen.

[0010] Furthermore, the first filler layer of the PRB uses a combination of zero-valent iron, iron filings, manganese dioxide, and biochar.

[0011] Furthermore, the second filling material layer of the PRB uses a combination of vermiculite, zeolite, and biochar to immobilize microorganisms.

[0012] The beneficial effects of this utility model are:

[0013] (1) This invention generates microbubbles using ultrasound, which burst and release energy to disrupt the structure of pollutants and promote degradation. Simultaneously, the ultrasonic vibration induces microflows, promoting pollutant diffusion and mixing, increasing reaction efficiency, and forming microjets and shock waves that scour the surface of the reaction packing, removing deposits and reducing packing blockage. The high temperature and pressure generated when the bubbles burst can decompose or oxidize the blocking substances, maintaining the activity of the reaction packing.

[0014] (2) In this invention, an electric field is applied during the treatment process. Charged ions move towards the opposite electrode under the influence of the electric field. Under neutral pH conditions, this promotes the migration of negatively charged hexavalent chromium oxyacid ions and tetracyclines with dissociated hydroxyl groups towards the anode. This can accelerate the desorption of pollutants from the soil, directionally drive complex pollutants through the PRB reaction medium, and enhance the reaction efficiency of pollutants.

[0015] (3) This invention combines electric and ultrasonic-assisted technologies to produce a synergistic effect: enhanced migration, with the electric field driving pollutant migration and the ultrasonic waves promoting diffusion and mixing, thus improving migration efficiency; and increased reaction rate, with the ultrasonic waves increasing the contact between pollutants and packing material and the electric field accelerating the movement of charged pollutants, thus jointly improving the reaction rate. Furthermore, both technologies are easy to automate, reducing the cost of manual intervention.

[0016] (4) This utility model uses two layers of reaction fillers to oxidize and degrade organic pollutants, adsorb and co-precipitate pollutants. Vermiculite, zeolite and biochar all have the ability to adsorb complex pollutants and can also provide attachment sites for microorganisms. Among them, biochar can provide a reducing environment for microorganisms and promote biological reduction. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of this utility model;

[0018] In the diagram: 1—Deionized water conical flask, 2—Peristaltic pump, 3—Electrode chamber, 4—Graphite electrode, 5—External DC power supply, 6—Ultrasonic module power supply, 7—Quartz sand layer, 8—Composite contaminated soil, 9—PRB first filling material layer, 10—Ultrasonic vibrator, 11—PRB second filling material layer, 12—Recovery liquid conical flask. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the present invention. In order to better illustrate the specific embodiments of the present invention, some parts in the drawings may be omitted, enlarged or reduced, and do not represent the actual product size. It is understandable for those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this utility model, it should be noted that the terms "front", "rear", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0021] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," and "connected," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0022] like Figure 1 The device shown is an electric and ultrasonic-assisted PRB in-situ microbial remediation device for complex pollutants in soil and groundwater. It includes a small-scale remediation simulation device that simulates the flow of complex polluted soil and groundwater, and combines PRB, electric and ultrasonic assistance.

[0023] The device for remediating composite pollutants in soil and groundwater includes a main body and a deionized water conical flask 1. The deionized water conical flask 1 is connected to a peristaltic pump 2 via an inlet pipe. The outlet of the peristaltic pump 2 is connected to one side of the main body via an inlet pipe. An outlet pipe is provided on the other side of the main body and is connected to a recovery liquid conical flask 12. The main body includes a PRB remediation device, an electric remediation device, and an ultrasonic remediation device. Composite polluted soil 8 is placed inside the main body. The PRB remediation device includes a first PRB filling material layer 9 and a second PRB filling material layer 11 located downstream of the composite polluted soil 8. The ultrasonic remediation device includes an ultrasonic vibrating rod 10 located in the first PRB filling material layer 9. The ultrasonic vibrating rod 10 is connected to an ultrasonic module power supply 6.

[0024] The electric repair device includes two graphite electrodes 4 and an external DC power supply 5. The graphite electrodes 4 include an anode and a cathode, and the external DC power supply 5 is connected between the anode and cathode graphite electrodes.

[0025] An external DC power supply 5 is applied to both sides of the complex contaminated soil and the PRB area. An electrode chamber 3 is set outside the graphite electrode 4, with the cathode upstream and the anode downstream.

[0026] The main body of the device has simulated groundwater aquifer areas on both sides, and electrode chambers 3 are distributed on both sides of the simulated groundwater aquifer areas. A layer of quartz sand 7 is filled between the simulated groundwater aquifer areas and the electrode chambers 3, and is isolated by a filter screen.

[0027] Specifically, the device is made of acrylic. The simulated groundwater aquifer area is 30cm × 50cm × 10cm (height × length × width). A 30cm × 15cm × 10cm PRB area is arranged near the anode, and the remaining area is filled with composite contaminated soil 8. Electrode chambers 3, each 30cm × 10cm × 10cm, are located on both sides of the groundwater aquifer area and are used to install graphite electrodes 4 and add electrolyte solution. A peristaltic pump 2 and a conical flask containing deionized water 1 are placed next to the cathode. A conical flask for collecting the solution is placed next to the anode. Quartz sand 7, 30cm × 3cm × 10cm, is filled between the groundwater aquifer area and the electrode chamber 3 area, separated by a 0.5mm nylon filter screen.

[0028] The PRB area is arranged from left to right with the second layer of PRB filler measuring 30cm × 7.5cm × 10cm and the first layer of PRB filler measuring 30cm × 7.5cm × 10cm. The first layer of PRB filler material 9 uses a combination of zero-valent iron, iron filings, manganese dioxide, and biochar. The second layer of PRB filler material 11 uses a combination of vermiculite, zeolite, and biochar to immobilize microorganisms. The MnO2 added to the first layer of PRB reaction filler has strong oxidizing properties, which can oxidize and degrade organic pollutants (such as tetracycline) and promote the reduction of Cr(VI) to the less toxic Cr(III). MnO2 acts as a catalyst, accelerating the corrosion process of ZVI and iron filings, increasing the reaction rate, reducing the consumption of ZVI and iron filings, and extending the service life of the filler. Biochar has a high specific surface area and rich pore structure, which can adsorb tetracycline and Cr(VI) and can also act as a pH buffer to maintain remediation conditions. Iron filings can generate iron oxides and hydroxides, adsorb and co-precipitate pollutants, and provide mechanical support to prevent the filler particles from densely packing together, keeping the pores open and reducing clogging. In the second layer of the PRB reaction packing, desulfurizing Vibrio can directly reduce Cr(VI) and TC, or indirectly by reducing sulfate to produce reducing sulfides (such as FeS), thereby promoting the reduction of Cr(VI) and TC. Vermiculite, zeolite, and biochar all have the ability to adsorb complex pollutants and can also provide attachment sites for microorganisms. Among them, biochar can provide a reducing environment for desulfurizing Vibrio, promoting bioreduction.

[0029] Preparation of the composite contaminated soil 8: Soil from uncontaminated natural environments was selected. Large clumps of soil were broken up using a rubber mallet, and visible plant roots and impurities were removed. The soil was then air-dried in the dark for 7-14 days, ground through a 20-40 mesh sieve, and thoroughly mixed with a solution containing tetracycline (TC) and hexavalent chromium [Cr(VI)] at a water-to-soil ratio of 1:10-1:5. The soil was aged in the dark for 21-35 days, with water sprayed every 5-7 days to maintain a soil moisture content of 20%-40%, and continuous stirring was maintained. The final product was a composite contaminated soil containing Cr(VI) and TC (this method is also applicable to other composite contaminants requiring reduction and detoxification, and for which the target remediation material is negatively charged under given conditions).

[0030] According to Figure 1 The apparatus shown in the diagram consists of electrode chamber 3, peristaltic pump 2, deionized water conical flask 1, recovery liquid conical flask 12, and is filled with PRB first layer filling material 9, PRB second layer filling material 11, quartz sand 7, and composite contaminated soil 8.

[0031] The ultrasonic vibrating rod 10 at the center of the first PRB filling material layer 9 is connected to an external ultrasonic module power supply 6, with its frequency set to 20kHz and its intensity selected as 30W / cm. 2 -50 W / cm 2 The recommended work cycle is 1 hour, with 5-10 minutes of work time. Moderate ultrasonic intensity and intermittent operation can achieve better repair results. Excessive ultrasonic intensity and continuous operation result in high energy consumption with little improvement in repair efficiency, and may also reduce microbial activity.

[0032] The electrode chamber uses an external DC power supply 5, and the electrodes are graphite electrodes 4. The voltage is selected as 0.6V / cm-1.0V / cm. Excessive voltage will reduce the activity of microorganisms.

[0033] Peristaltic pump 2 injects deionized water at a flow rate of 1.8 mL / min-7.2 mL / min. Before the remediation begins, wait until the water is evenly filled into the soil and the liquid level in electrode chamber 3 is stable. During this period, maintain the soil moisture content at around 30%-50%.

[0034] This invention prepares composite contaminated soil 8 by controlling the flow rate of peristaltic pump 2 to simulate the flow of composite contaminated soil and groundwater. The device is positioned downstream of the simulated composite contaminated soil and groundwater, with an external DC power supply applied to both sides of the composite contaminated soil and the remediation area, with the cathode upstream and the anode downstream. The simulated groundwater first flows through the composite contaminated soil via peristaltic pump 2, then through the first PRB filling material layer 9, where ultrasonic vibrating rod 10 provides ultrasonic synergistic treatment, subsequently through the second PRB filling material layer 11 containing immobilized microorganisms, and finally flows into the conical flask 12 containing the recovery liquid.

[0035] The total remediation period was 5-15 days. Before and after remediation, 20.00 g soil samples were taken from the center of area 8 of the compound-contaminated soil. All collected soil samples were stored at -20℃. The method for detecting Cr(VI) in the soil was "Determination of Hexavalent Chromium in Soil and Sediments: Alkaline Solution Extraction-Flame Atomic Absorption Spectrophotometry" (HJ 1082-2019), and the method for detecting TC in the soil was "Simultaneous Detection Method of Tetracyclines, Fluoroquinolones, Sulfonamides, Macrolides and Chloramphenicol Antibiotics in Soil: High Performance Liquid Chromatography" (NY / T3787-2020). The device achieved a target remediation efficiency of over 85% for Cr(VI) and TC in compound-contaminated soil 8.

[0036] The concentrations of Cr(VI) and TC in the electrolyte were determined by absorption spectrophotometry and high performance liquid chromatography, respectively. Combined with the electrolyte volume, the total amount of Cr(VI) and TC after remediation in the recovered conical flask was obtained. The total amount of Cr(VI) and TC added to the composite contaminated soil 8 was compared with the total amount of Cr(VI) and TC added to the soil to obtain the adsorption and interception efficiency of PRB for pollutants. The target remediation efficiency was above 85%.

[0037] In this invention, PRB is used as the primary remediation agent, with electric and ultrasonic assistance. Utilizing a combined physical-chemical-biological effect, it achieves the reduction and directional migration of hexavalent chromium and tetracycline in complexly contaminated soil. This device offers advantages such as reduced PRB packing clogging and passivation, improved pollutant mass transfer remediation efficiency, and low long-term operation and maintenance costs.

[0038] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A device for in-situ microbial remediation of complex pollutants in soil and groundwater using electrically powered ultrasonic-assisted PRB (polyurethane) remediation, characterized in that, The device includes a main body and a deionized water conical flask (1). The deionized water conical flask (1) is connected to a peristaltic pump (2) through an inlet pipe. The outlet of the peristaltic pump (2) is connected to one side of the main body through an inlet pipe. The other side of the main body is provided with an outlet pipe, which is connected to a recovery liquid conical flask (12). The main body includes a PRB remediation device, an electric remediation device, and an ultrasonic remediation device. The main body contains composite contaminated soil (8). The PRB remediation device includes a first PRB filling material layer (9) and a second PRB filling material layer (11) located downstream of the composite contaminated soil (8). The ultrasonic remediation device includes an ultrasonic vibrating rod (10) located in the first PRB filling material layer (9). The ultrasonic vibrating rod (10) is connected to an ultrasonic module power supply (6).

2. The device for in-situ microbial remediation of soil and groundwater complex pollutants using electrically powered ultrasonic-assisted PRB according to claim 1, characterized in that, The electric repair device includes two graphite electrodes (4) and an external DC power supply (5). The graphite electrodes (4) include an anode and a cathode, and the external DC power supply (5) is connected between the anode and cathode graphite electrodes.

3. The device for in-situ microbial remediation of soil and groundwater complex pollutants using electrically powered ultrasound-assisted PRB according to claim 2, characterized in that, An external DC power supply (5) is applied to both sides of the contaminated soil and the remediation area. An electrode chamber (3) is set on the outside of the graphite electrode (4), with the cathode upstream and the anode downstream.

4. The device for in-situ microbial remediation of soil and groundwater complex pollutants with electric ultrasonic-assisted PRB according to claim 3, characterized in that, The main body of the device has simulated groundwater aquifer areas on both sides, and electrode chambers (3) are distributed on both sides of the simulated groundwater aquifer areas. A quartz sand layer (7) is filled between the simulated groundwater aquifer areas and the electrode chambers (3) to isolate them with a filter screen.

5. The device for in-situ microbial remediation of complex pollutants in soil and groundwater using electrically powered ultrasound-assisted PRB according to claim 4, characterized in that, The simulated groundwater aquifer area is 30cm×50cm×10cm, of which the PRB area is 30cm×15cm×10cm on the side near the anode, and the rest is filled with composite contaminated soil. The electrode chamber areas distributed on both sides of the groundwater aquifer area are 30cm×10cm×10cm. The groundwater aquifer area and the electrode chamber area are filled with a 30cm×3cm×10cm quartz sand layer, which is separated by a 0.5mm nylon filter screen.

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