An electro-catalytic oxidation system, method and ecological joint treatment method for in-situ remediation of water body sediments

Abstract

The application discloses an electro-catalytic oxidation system and method and an ecological joint treatment method for in-situ remediation of water body sediments, which utilizes an intelligent pulse power controller to perform intermittent pulse electro-catalytic oxidation on the bottom mud at the water bottom, generates hydroxyl radicals through in-situ catalysis of an anode to degrade organic pollutants of the bottom mud, generates micro-bubbles in the interstices of the bottom mud through the electrolysis of water to improve the oxidation-reduction potential, and further reserves time for the soluble pollutants in the interstitial water of the bottom mud to sufficiently diffuse to the surface of the electrode, so as to avoid energy waste caused by concentration polarization. Through reverse power supply, the polarity of the anode and the cathode is instantaneously reversed, trace amounts of acidic substances and gas generated through in-situ electrolysis are utilized to strip off the calcium and magnesium scale attached to the surface of the cathode, and manual cleaning and maintenance under water are realized. In combination with the planting of submerged plants on the treated bottom mud, ecological joint treatment is realized, the root system of the submerged plants is utilized to perform long-term ecological fixation and water purification on the treated sediments.

Description

Technical Field

[0001] This invention specifically relates to an electrocatalytic oxidation system, method, and ecological joint treatment method for in-situ remediation of sediments in water bodies, belonging to the field of water environment engineering and ecological restoration technology. Background Technology

[0002] Sediments in lakes, rivers, and other water bodies are often endogenous sources of pollution, contributing to eutrophication and black / odorous water conditions. Traditional sediment treatment methods mainly include off-site environmental dredging and in-situ chemical treatment.

[0003] However, off-site dredging is a massive undertaking with high costs, and the subsequent dewatering and disposal of bottom sediment is extremely difficult; on-site application of chemicals has the problems of easy loss of chemicals with water flow, short duration of action, and potential ecotoxicity to aquatic organisms.

[0004] For water bodies aiming to construct grass-like lake ecosystems, traditional dredging completely destroys benthic habitats and the root base of aquatic vegetation. Although existing electrochemical technologies have precedents for application in soil remediation, directly inserting ordinary metal electrodes into the bottom sediment and applying electricity can cause severe anodic dissolution corrosion, releasing large amounts of metal ions into the water and causing secondary pollution. Furthermore, the cathode is highly susceptible to calcium and magnesium ion scaling, leading to system failure.

[0005] Therefore, there is an urgent need for an in-situ sediment remediation technology that is free from secondary pollution, low in energy consumption, and compatible with the ecological restoration of aquatic bodies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an electrocatalytic oxidation system, method, and ecological joint management method for in-situ remediation of sediments in water bodies.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An electrocatalytic oxidation system for in-situ remediation of sediments in aquatic bodies includes a power module that is suspended on the water surface using an ecological floating bed, and an electrode matrix module for insertion into the sediments at the bottom of the water.

[0009] The power module supplies power to the electrode matrix module via an intelligent pulse power controller;

[0010] The electrode matrix module includes an anode array and a cathode array;

[0011] The intelligent pulse power controller has a built-in reversal control unit, which is used to switch the positive and negative poles between the anode array and the cathode array.

[0012] The aforementioned anode and cathode arrays are arranged in an "S" shape, alternating along the direction of water flow or revetment.

[0013] Furthermore, the linear spacing between adjacent anodes and cathodes in adjacent anode and cathode arrays is 10-50 cm. This arrangement allows the electric field lines to penetrate the sediment between the electrodes uniformly, ensuring the uniformity of electrocatalytic oxidation and improving the remediation effect.

[0014] The aforementioned anode and cathode arrays are inserted into the underwater sediments to a depth of 20-60 cm. This depth can cover the core pollutant layer of the sediments, achieving effective degradation of pollutants.

[0015] The aforementioned anode array is a titanium-based mesh electrode made of shape-stable anode material. The surface of the titanium-based mesh electrode is coated with a ruthenium-iridium composite oxide coating or a lead dioxide coating with a coating thickness of 1-15 μm. The pore size of the titanium-based mesh electrode is 5-20 mm. Shape-stable anode material can effectively avoid anodic dissolution corrosion and prevent secondary pollution by metal ions. The mesh structure ensures the permeability of interstitial water in the sediment, which is conducive to the diffusion of pollutants to the electrode surface.

[0016] The cathode array is made of stainless steel or porous titanium alloy, which has good conductivity and corrosion resistance, and is suitable for long-term underwater operation.

[0017] The power module includes a solar photovoltaic panel and a battery pack. The solar photovoltaic panel and the battery pack are electrically connected, and the battery pack supplies power to the intelligent pulse power controller. Utilizing solar power is energy-saving and environmentally friendly, suitable for outdoor water restoration scenarios without mains power. The ecological floating bed is a high-density polyethylene modular splicing floating bed, corrosion-resistant, easy to assemble, and adaptable to the restoration needs of different water areas. Planting baskets are arranged around the ecological floating bed for planting aquatic plants, realizing the ecological nature of the floating bed. The intelligent pulse power controller is encapsulated in an IP68 waterproof enclosure to ensure operational stability in underwater environments.

[0018] An electrocatalytic oxidation method for in-situ remediation of sediments in aquatic bodies, applicable to the aforementioned electrocatalytic oxidation system, includes the following steps:

[0019] S1. System Deployment: Anchor the ecological floating bed to the water area to be restored, lower the electrode matrix module so that the anode array and cathode array are vertically inserted into the bottom sediment, complete the circuit connection and debug the intelligent pulse power controller.

[0020] S2. Intermittent Pulse Electrocatalytic Oxidation: The intelligent pulse power controller is activated to output pulsed DC power to the electrode matrix module. The voltage of the pulsed DC power is 5-36V, the apparent current density applied to the anode array is 5-50mA / cm², the pulse frequency is 50-1000Hz, and the duty cycle is 20-80%. An intermittent operation mode of "power-on operation - power-off rest" is adopted. After power-on operation for 2-6 hours, the system is powered off and allowed to rest for 1-3 hours. The power-off rest setting allows soluble pollutants in the interstitial water of the sediment to fully diffuse to the electrode surface, avoiding energy waste caused by concentration polarization. At the same time, the in-situ catalysis of the anode generates hydroxyl radicals, which can efficiently degrade organic pollutants in the sediment. The microbubbles generated in the interstitial water during the water electrolysis process can also increase the redox potential of the sediment and eliminate the anaerobic black and odorous environment.

[0021] S3. Reverse Electrostatic Descaling: The positive and negative poles of the anode and cathode arrays are switched by the reversing control unit. After 12-48 hours of forward electrocatalytic oxidation, reverse electrostatic discharge is applied for 10-30 minutes to instantly reverse the polarity of the anode and cathode. The trace acidic substances and gases generated by in-situ electrolysis are used to peel off and dissolve the calcium and magnesium scale attached to the cathode surface, achieving underwater maintenance-free cleaning and ensuring long-term high-efficiency operation of the electrodes.

[0022] In step S2, the voltage of the pulsed DC power supply is 24V, the apparent current density is 10-30mA / cm², the pulse frequency is 200-500Hz, and the duty cycle is 40-60%; the intermittent operation mode is to operate for 4 hours after power-on and then leave it to stand for 2 hours after power-off.

[0023] In step S3, after 24 hours of forward electrocatalytic oxidation, reverse current is applied for 15 minutes; this can minimize the impact on the electrocatalytic oxidation repair process while ensuring the descaling effect.

[0024] An ecological joint management method for in-situ remediation of aquatic sediments, based on the aforementioned electrocatalytic oxidation method, includes the following steps:

[0025] A1. System Deployment: Anchor the ecological floating bed carrying the power module and intelligent pulse power controller to the water area to be restored, and lower the electrode matrix module so that the anode array and cathode array are vertically inserted into the bottom sediment in an “S” shaped staggered arrangement to complete the system commissioning.

[0026] A2. Electrocatalytic oxidation remediation: The intelligent pulse power controller is activated to perform intermittent pulse electrocatalytic oxidation on the sediment according to the method described in claim 6. Hydroxyl radicals are generated in situ through anodic catalysis to degrade organic pollutants in the sediment. Microbubbles are generated in the sediment gaps during the water electrolysis process to increase the oxidation-reduction potential (ORP).

[0027] And through the reverse polarity control unit, reverse power descaling operation is performed, and it continues to run until the organic matter content of the deposits drops to the target threshold and the black and odorous state of the deposits is eliminated;

[0028] A3. Ecological Restoration Construction: Disconnect the system power supply, remove the electrode matrix module, and plant submerged plants in the revetment area and the restored sediment substrate. The roots of the submerged plants will be used to ecologically stabilize the treated sediment for a long time, preventing the sediment from being resuspended. At the same time, the submerged plants can absorb nutrients from the water and sediment, achieving long-term water purification and building a stable aquatic ecosystem.

[0029] In step A3, the submerged plants include one or two of Vallisneria natans and Myriophyllum spicatum, and are planted by sowing seeds or cuttings of plant branches; these submerged plants are highly adaptable, have well-developed root systems, and are effective in retaining sediment and purifying water.

[0030] The target threshold for the organic matter content of the sediment is a total organic carbon content of ≤30g / kg and a redox potential of ≥0mV. At this point, the sediment has eliminated the anaerobic black and odorous state and is suitable for the establishment and growth of submerged plants.

[0031] The advantages of this invention are:

[0032] The electrocatalytic oxidation system, method, and ecological joint remediation method for in-situ remediation of aquatic sediments of the present invention have the following beneficial effects:

[0033] 1. The electrocatalytic oxidation system of the present invention uses a titanium-based mesh electrode made of a stable anode material, which avoids secondary pollution of metal ions caused by anodic dissolution corrosion from the source. The cathode is made of stainless steel or porous titanium alloy material. Combined with the reverse electrode descaling technology, it can achieve underwater cleaning and maintenance without manual cleaning, which greatly reduces the operating and maintenance cost of the system.

[0034] 2. The electrocatalytic oxidation method of the present invention adopts an intermittent pulsed electrocatalytic oxidation mode, which not only improves the generation efficiency of hydroxyl radicals through pulsed direct current, efficiently degrades organic pollutants, and increases the redox potential of sediments, but also achieves full diffusion of pollutants in the interstitial water of sediments by power-off and settling, avoiding concentration polarization, reducing energy consumption, and achieving the optimal balance between remediation efficiency and energy consumption.

[0035] 3. The ecological joint treatment method of the present invention combines in-situ electrocatalytic oxidation remediation with submerged plant ecological restoration. First, the organic pollutants in the sediment are rapidly degraded and the black and odorous state is eliminated through electrocatalytic oxidation, creating a suitable habitat for the growth of submerged plants. Then, the submerged plants achieve long-term ecological fixation of sediments and long-term purification of water quality, realizing the synergistic effect of sediment pollution control and aquatic ecosystem restoration, and the restoration effect is more lasting.

[0036] 4. The system of this invention uses an ecological floating bed to carry the power supply and control modules. The modularly spliced ​​floating bed is suitable for the restoration needs of different water areas. The power module uses solar photovoltaic panels in conjunction with a battery pack for power supply, which is energy-saving and environmentally friendly. It does not require mains power connection and is suitable for sediment restoration of various outdoor lakes, rivers and other water bodies. The system is highly mobile, easy to construct, and has wide applicability and practicality. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the electrocatalytic oxidation system of the present invention.

[0038] Figure 2 This is a schematic diagram of the arrangement of the anode array and the cathode array.

[0039] The labels in the attached diagram have the following meanings: 1. Ecological floating bed, 2. Solar photovoltaic panel, 3. Battery pack, 4. Intelligent pulse power controller, 5. Waterproof box, 6. Anode array, 7. Cathode array. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0041] This embodiment presents an ecological joint management experiment on in-situ remediation of water sediments in a shallow urban lake in southern China that is eutrophic and has severely black and odorous bottom sediments. The experiment lasted for 30 days.

[0042] Building an electrocatalytic oxidation system

[0043] The electrocatalytic oxidation system of this embodiment includes an ecological floating bed 1, a power module, an intelligent pulse power controller 4, and an electrode matrix module;

[0044] Ecological floating bed 1: A modular splicing floating bed made of high-density polyethylene (HDPE) material, with planting baskets on the outside for planting aquatic plants. The floating bed is anchored to the lake water area to be restored by anchor ropes.

[0045] Power module: includes a monocrystalline silicon flexible solar photovoltaic panel 2 (peak power 300W) and a 24V / 100Ah lithium iron phosphate waterproof battery pack 3. The solar photovoltaic panel 2 and the battery pack 3 are electrically connected to supply power to the system.

[0046] Intelligent pulse power controller 4: It adopts an intelligent pulse power control motherboard based on STM32F4 series microcontroller, which is encapsulated in IP68 grade die-cast aluminum waterproof box 5 and has a reversal control unit inside;

[0047] Electrode matrix module: includes anode array 6 and cathode array 7. Anode array 6 is a titanium-based ruthenium-iridium (Ti / RuO2-IrO2) mesh electrode with a titanium mesh substrate thickness of 2mm, a rhomboid mesh size of 10mm×5mm, and a surface active coating thickness of 8μm. Cathode array 7 is a 316L stainless steel perforated mesh plate with a hole diameter of 8mm and a thickness of 2mm. Anode array 6 and cathode array 7 are arranged in an "S" shape along the water flow direction and are suspended below the ecological floating bed 1 by an adjustable length of insulated and corrosion-resistant cable. The straight-line distance between adjacent anodes and cathodes is 30cm, and the insertion depth into the sediment is 40cm.

[0048] Electrocatalytic oxidation method

[0049] S1. System deployment: Anchor the electrocatalytic oxidation system constructed above to the water area to be restored, check the circuit connection, and debug the intelligent pulse power controller 4 to ensure that all parameters can be set and operated normally.

[0050] S2. Intermittent pulsed electrocatalytic oxidation: The intelligent pulsed power controller 4 is activated, outputting pulsed DC power. The voltage is set to 24V, the apparent current density applied to the anode array 6 is 20mA / cm², the pulse frequency is 200Hz, and the duty cycle is 50%. The intermittent operation mode of "powering on for 4 hours and then powering off for 2 hours" is adopted. The anode generates hydroxyl radicals in situ to degrade organic pollutants in the sediment, and the microbubbles generated by water electrolysis increase the redox potential of the sediment.

[0051] S3, Reverse Power Descaling: Set the operating parameters of the reverse polarity control unit. After 24 hours of forward electrocatalytic oxidation, automatically perform 15 minutes of reverse power to peel off and dissolve the calcium and magnesium scale on the surface of the cathode array 7.

[0052] Ecological joint governance method

[0053] After continuously implementing the above electrocatalytic oxidation method for 30 days, the sediment indicators were tested. The redox potential of the sediment increased from -280mV to +45mV, the total organic carbon content decreased from 45.2g / kg to 26.8g / kg, the organic matter degradation rate reached 40.7%, the sediment completely eliminated the anaerobic black and odorous state, and met the habitat requirements for ecological restoration.

[0054] Disconnect the system power, remove the electrode matrix module, sow the roots of Vallisneria natans and the broken branches of Myriophyllum spicatum on the restored sediment substrate, and insert Myriophyllum spicatum cuttings in the revetment area along the lake shore to carry out ecological planting of submerged plants.

[0055] Repair effect

[0056] Experimental results showed that the black and odorous state of the sediments was completely eliminated after electrocatalytic oxidation remediation, and the oxidation-reduction potential and organic matter content reached the suitable conditions for the growth of submerged plants. The survival rate of planted Vallisneria natans and Myriophyllum spicatum increased by more than 80% compared with the untreated area. The roots of the submerged plants quickly took root in the sediments, achieving effective sediment fixation. At the same time, the submerged plants absorbed nutrients such as nitrogen and phosphorus from the water and sediments, and the water transparency increased by 60% compared with before remediation. The eutrophication level of the water body was significantly reduced, achieving a synergistic effect of sediment pollution control and water ecological restoration.

[0057] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. An electrocatalytic oxidation system for in-situ remediation of aquatic sediments, characterized in that, This includes a power module that uses an ecological floating bed to suspend the water surface, and an electrode matrix module for insertion into underwater sediments; The power module supplies power to the electrode matrix module via an intelligent pulse power controller; The electrode matrix module includes an anode array and a cathode array; The intelligent pulse power controller has a built-in reversal control unit, which is used to switch the positive and negative poles between the anode array and the cathode array.

2. The electrocatalytic oxidation system according to claim 1, characterized in that, The anode array and cathode array are arranged alternately along the direction of water flow or revetment.

3. The electrocatalytic oxidation system according to claim 2, characterized in that, The linear spacing between adjacent anodes and cathodes in adjacent anode and cathode arrays is 10-50 cm.

4. The electrocatalytic oxidation system according to claim 1, characterized in that, The anode and cathode arrays are inserted into the underwater sediments at a depth of 20-60 cm.

5. The electrocatalytic oxidation system according to claim 1, characterized in that, The anode array is a titanium-based mesh electrode made of shape-stable anode material. The surface of the titanium-based mesh electrode is coated with a ruthenium-iridium composite oxide coating or a lead dioxide coating with a coating thickness of 1-15 μm. The pore size of the titanium-based mesh electrode is 5-20 mm. The cathode array is made of stainless steel or porous titanium alloy.

6. An electrocatalytic oxidation method for in-situ remediation of aquatic sediments, applicable to the electrocatalytic oxidation system described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Anchor the ecological floating bed to the water area to be restored, lower the electrode matrix module so that the anode array and cathode array are vertically inserted into the bottom sediment, complete the circuit connection and debug the intelligent pulse power controller. S2. Start the intelligent pulse power controller and output pulsed DC power to the electrode matrix module. The voltage of the pulsed DC power is 5-36V, the apparent current density applied to the anode array is 5-50mA / cm², the pulse frequency is 50-1000Hz, and the duty cycle is 20-80%. The intermittent operation mode of "power-on operation - power-off rest" is adopted. After powering on for 2-6 hours, the device is powered off and left to rest for 1-3 hours. S3. The positive and negative poles of the anode and cathode arrays are switched by the reversing control unit. After running for 12-48 hours in the forward electrocatalytic oxidation, reverse current is applied for 10-30 minutes to peel off and dissolve the calcium and magnesium scale attached to the cathode surface.

7. The electrocatalytic oxidation method according to claim 6, characterized in that, In step S2, the voltage of the pulsed DC power supply is 24V, the apparent current density is 10-30mA / cm², the pulse frequency is 200-500Hz, and the duty cycle is 40-60%; the intermittent operation mode is to operate for 4 hours after power-on and then leave it to stand for 2 hours after power-off.

8. The electrocatalytic oxidation method according to claim 6, characterized in that, In step S3, after 24 hours of forward electrocatalytic oxidation, reverse electrolysis is performed for 15 minutes.

9. A method for in-situ ecological remediation of water sediments, based on the electrocatalytic oxidation method described in claim 6, characterized in that, Includes the following steps: A1. System Deployment: Anchor the ecological floating bed carrying the power module and intelligent pulse power controller to the water area to be restored, and lower the electrode matrix module so that the anode array and cathode array are vertically inserted into the bottom sediment in an "S"-shaped staggered arrangement to complete the system commissioning. A2. Electrocatalytic oxidation remediation: Start the intelligent pulse power controller, perform intermittent pulse electrocatalytic oxidation on the deposits according to the method described in claim 6, and perform reverse power descaling operation through the reverse polarity control unit, and continue to run until the organic matter content of the deposits drops to the target threshold and the black and odorous state of the deposits is eliminated; A3. Ecological Restoration Construction: Disconnect the system power supply, remove the electrode matrix module, and plant submerged plants in the revetment area along the shore and on the restored sediment base. Utilize the root system of the submerged plants to achieve long-term ecological fixation of the treated sediment and water purification.

10. The ecological joint governance method according to claim 9, characterized in that, In step A3, the submerged plants include one or two of Vallisneria natans and Myriophyllum spicatum, and are planted by sowing seeds or by cuttings of plant branches. The target threshold for sediment organic matter content is a total organic carbon content ≤30g / kg and a sediment redox potential ≥0mV.

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