Method for in-situ carbon sequestration and sink enhancement of lake basin floating mud

Abstract

The application discloses a device and a method for in-situ improving carbon sequestration and sink of lake floating mud, and the device comprises a floating mud capturing tank and a microbial electrochemical system; the floating mud capturing tank is arranged below a lake surface, a cathode of the microbial electrochemical system is floated on the lake surface, an anode shaft is vertically arranged in the floating mud capturing tank, M anodes of the same height are fixedly connected to a sleeve to form an impeller, the sleeve is sleeved on the anode shaft, and N impellers are formed by the anodes, the N impellers are rotationally connected to the anode shaft at different heights, all the anodes are electrically connected to the cathode through external resistors in parallel to form an external circuit, a voltage signal collector is arranged in the external circuit, and a control system is electrically connected to the voltage signal collector and connected to control the anodes. The device can humify unstable organic carbon in the floating mud, reduce the content of the unstable organic carbon, reduce the carbon emission potential of the floating mud, improve the solubility of the floating mud to greenhouse gases, and improve the carbon sequestration and sink ability of the lake floating mud.

Description

Technical Field

[0001] This invention belongs to the field of water environment ecological restoration technology, specifically relating to an in-situ device and method for enhancing carbon sequestration and absorption of floating mud in lakes and ponds. Background Technology

[0002] As a crucial node connecting river and lake systems, lakes and ponds are important water areas for the purification of low-pollution aquatic ecosystems and are the focus of water resource protection and aquatic ecosystem restoration in river network areas. Their water purification function cannot be ignored. Lake and pond floating mud is characterized by high organic carbon content and high microbial activity, making it a hotspot for carbon emissions from river and lake ecosystems. Floating mud also has strong fluidity and can be resuspended under hydrodynamic forces, instantly increasing the concentration of pollutants in the water, causing secondary pollution, and simultaneously reducing the depth of the euphotic layer, severely impacting the growth of submerged plants and ecosystem restoration. Therefore, the low-carbonization and stabilization of floating mud is an urgent problem that needs to be addressed in current research on river and lake ecological restoration.

[0003] Currently, dredging technology is the primary method for treating floating silt in lakes and ponds. However, dredging is typically limited to localized areas, and undredged silt is easily resuspended and transported back to dredged areas. Furthermore, dredging has short-term environmental impacts and disrupts the lakebed sediment ecosystem, hindering its ability to purify pollutants. Disturbance during dredging accelerates the emission of greenhouse gases such as methane and carbon dioxide from the silt. For lakes and ponds that have undergone several rounds of dredging or require ongoing endogenous pollution control even after recent dredging, the silt layer to be removed is thin and easily transported by water flow. Floating silt is a crucial component of endogenous pollution control in lakes and ponds and has become a major obstacle to the restoration of lake water environment and ecosystem functions. Therefore, there is an urgent need to develop new treatment methods.

[0004] Sedimentary microbial fuel cell (SMFC) technology is commonly used for the remediation of contaminated sediments. Currently, most existing SMFC processes employ flat-plate or honeycomb anode structures. When applied to deep sediments or floating sludge, the anode system faces significant resistance during on-site installation due to the need for deep burial within the sediment. Furthermore, most reported on-site applications of SMFC technologies utilize a single anode-cathode combination or a series / parallel connection of fuel cell stacks. These existing process structures, with the anode system fixed in the sediment, cannot accommodate the variations in the vertical thickness of the floating sludge layer caused by its flow characteristics and accumulation, thus affecting the remediation effectiveness.

[0005] Most importantly, existing SMFCs are mainly designed for the removal of organic matter from sediments. Since their anodes are placed in the sediments, they are not effective in sequestering and increasing carbon sequestration of greenhouse gases dissolved in floating sludge. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, the present invention aims to provide a device and method for enhancing carbon sequestration and absorption in lake and pond floating mud. This device utilizes a vertically distributed multi-anode-single-cathode microbial electrochemical system to in-situ improve the humification degree of the floating mud. In particular, the anode structure exhibits a vertical six-blade distribution within the floating mud, allowing it to be placed in situ based on its inherent characteristics and weight. Along a fixed main axis, individual anode structures can be connected in parallel within the floating mud. This process humifies unstable organic carbon within the floating mud, reducing its content, lowering its carbon emission potential, increasing its ability to dissolve greenhouse gases, and enhancing the carbon sequestration and absorption capacity of lake and pond floating mud.

[0007] To achieve the above objectives, the present invention specifically employs the following technical solutions:

[0008] A device for in-situ lifting of floating mud in lakes and ponds to enhance carbon sequestration includes a floating mud capture tank with an opening at the top and a microbial electrochemical system placed inside the floating mud capture tank.

[0009] The microbial electrochemical system includes an anode shaft, several sheet anodes, a cathode, and a control system.

[0010] The cathode floats on the lake surface, while the silt capture tank is located below the lake surface.

[0011] The anode shaft is vertically positioned inside the sludge capture tank.

[0012] M anodes of the same height are fixedly connected to a sleeve to form an impeller, and the sleeve is fitted onto the anode shaft.

[0013] The anode comprises N impellers, which are rotatably connected to the anode shaft at different heights.

[0014] M and N are independent natural numbers.

[0015] All the anodes are connected in parallel to the cathode via an external resistor to form an external circuit, in which a voltage signal collector is provided.

[0016] The control system is connected to control the anode, and the control system is electrically connected to the voltage signal collector.

[0017] The voltage signal collector is used to acquire and measure the voltage signal between the anode and cathode in real time, and feed the signal back to the control system.

[0018] Furthermore, the anode is composed of a stainless steel perforated mesh plate and a carbon felt attached to the surface of the mesh plate.

[0019] Furthermore, M is 2 to 6, preferably 5.

[0020] Furthermore, the spacing between adjacent impellers is 0 to 10 cm, preferably 1 cm.

[0021] Furthermore, the sleeve is a stainless steel perforated tube.

[0022] Furthermore, the impeller rotates at a speed of 0–10 r / min, preferably 3 r / min. It rotates within the floating mud as needed.

[0023] Furthermore, the dimensions of the anode are (5-50)cm × (5-50)cm.

[0024] Furthermore, the aperture of the stainless steel perforated mesh plate is 0.1 to 0.5 cm, preferably 0.2 cm.

[0025] Furthermore, the cathode is a carbon felt.

[0026] Furthermore, the mud-capping tank is placed at the bottom of the lake.

[0027] Furthermore, the sludge capture tank is cylindrical, with a length, width, and height of (0.8–3) m, (0.8–3) m, and (1.5–3) m, respectively.

[0028] The second objective of this invention is to provide a method for enhancing carbon sequestration and sinking of floating mud in lakes and ponds, comprising:

[0029] The floating mud capture tank in the aforementioned device for enhancing carbon sequestration and absorption of floating mud in lakes and ponds is placed in the area where lake currents converge at the bottom of the lake. Floating mud is collected by hydrodynamics. The voltage signal collector acquires the voltage signal from the external circuit and feeds it back to the control system. The control system, according to settings, controls the impeller to rotate when the voltage signal reaches its peak and begins to decline. When there are multiple impellers, the control system, according to settings, can selectively rotate impellers at specific heights, thereby achieving independent rotation of each impeller, promoting the floating mud's ability to dissolve greenhouse gases, and enhancing the lake's ability to sequester and absorb carbon.

[0030] The beneficial effects of this invention are as follows:

[0031] This invention utilizes hydrodynamics to automatically collect floating mud from lakes and ponds into a capture tank, where it undergoes in-situ humification treatment. This overcomes the problems of traditional mud dredging techniques, such as damage to the lakebed sediment ecosystem and secondary pollution. The novel device employs a multi-anode vertical arrangement adapted to the thickness of the floating mud accumulation in the capture tank, enabling in-situ humification treatment of floating mud captured at different times. By controlling the rotation speed of the impellers at different anode layers, the electron transfer rate of microorganisms within the captured floating mud is accelerated, increasing the degree of humification, promoting the stabilization of organic carbon within the floating mud, and enhancing the floating mud's ability to dissolve greenhouse gases. This improves carbon sequestration and development of a new bioelectric current-mediated aquatic carbon sink amplification model. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the anode and anode shaft of the present invention when N is 2 to 6.

[0033] Figure 2 This is a schematic diagram of the device for enhancing carbon sequestration and absorption of floating mud in lakes and ponds according to the present invention. 1 is the floating mud capture tank, 2 is the anode, 3 is the cathode, and 4 is the voltage signal collector.

[0034] Figure 3 This is a photograph of the actual device for improving carbon sequestration and absorption of floating mud in lakes and ponds according to the present invention.

[0035] Figure 4 The change in humic acid content after treatment of floating sludge in Example 1.

[0036] Figure 5 The change in fulvic acid content after treatment of floating sludge in Example 1.

[0037] Figure 6 The CH4 emission flux after the treatment of floating sludge in Example 1.

[0038] Figure 7 This represents the CO2 emission flux after the treatment of floating sludge in Example 1.

[0039] Figure 8 The CO2 emission flux after the electrode rotates during the sludge treatment process in Example 1.

[0040] Figure 9 The CH4 emission flux after the electrode rotates during the sludge treatment process in Example 1.

[0041] Figure 10 The CO2 emission flux is the result of the electrode stratification (upper, middle, and lower) rotation during the sludge treatment process in Example 1.

[0042] Figure 11 The CH4 emission flux after the electrodes are rotated in layers (upper, middle, and lower) during the sludge treatment process in Example 1. Figure 12These are the voltage signals of each device in Example 1 during the sludge disposal process.

[0043] Figure 13 The voltage signal is the voltage signal of the device for carbon sequestration and enhancement of floating mud in lakes and ponds with N=5 in Example 1 during the floating mud treatment process. Detailed Implementation

[0044] The technical solution of the present invention will be further described below with reference to specific accompanying drawings and embodiments.

[0045] A device for enhancing carbon sequestration and absorption of floating mud in lakes and ponds is employed, comprising a floating mud capture tank with an opening at the top and a microbial electrochemical system placed inside the floating mud capture tank;

[0046] The microbial electrochemical system includes an anode shaft, several sheet anodes, a cathode, and a control system.

[0047] The cathode floats on the lake surface, while the silt capture tank is located below the lake surface.

[0048] The anode shaft is vertically positioned inside the sludge capture tank.

[0049] M anodes of the same height are fixedly connected to a sleeve to form an impeller, and the sleeve is fitted onto the anode shaft.

[0050] The anode comprises N impellers, which are rotatably connected to the anode shaft at different heights.

[0051] M and N are independent natural numbers.

[0052] All the anodes are connected in parallel to the cathode via an external resistor to form an external circuit, in which a voltage signal collector is provided.

[0053] The control system is connected to control the anode, and the control system is electrically connected to the voltage signal collector.

[0054] The voltage signal collector is used to acquire and measure the voltage signal between the anode and cathode in real time, and feed the signal back to the control system.

[0055] The anode is composed of a stainless steel perforated mesh plate and carbon felt attached to the surface of the mesh plate.

[0056] M is 2 to 6, preferably 5.

[0057] The distance between adjacent impellers (the distance between them in the vertical direction) is 0 to 10 cm, preferably 1 cm.

[0058] The sleeve is a stainless steel perforated tube.

[0059] The impeller rotates at a speed of 0–50 r / min. It rotates within the floating mud as needed.

[0060] The dimensions of the anode are (5-50)cm × (5-50)cm.

[0061] The aperture of the stainless steel perforated mesh plate is 0.1 to 0.5 cm, preferably 0.2 cm.

[0062] The cathode is a carbon felt.

[0063] The mud-catching tank is located at the bottom of the lake.

[0064] The sludge capture tank is cylindrical, with a length, width and height of (0.8-3)m, (0.8-3)m and (1.5-3)m respectively.

[0065] Example 1

[0066] Surface mud samples were collected at Zhanghekou in Gehu Lake to conduct in-situ high-efficiency humification experiments.

[0067] like Figure 1-3 As shown, the above-mentioned device for enhancing carbon sequestration and absorption of floating mud in lakes and ponds was used, with N values ​​ranging from 2 to 6. A floating mud capture tank without a microbial electrochemical system was used as a control group.

[0068] During the experiment, when the voltage reached its peak value of 80mV and the voltage signal began to drop, the impeller was started to rotate at speeds of 3rpm and 10rpm respectively, and the voltage signal was collected and recorded in real time.

[0069] After the experiment, the contents of humic acid and fulvic acid in the floating mud before and after the experiment were compared, as well as the CH4 emission flux and CO2 emission flux after the experiment.

[0070] from Figure 4-7 It can be seen that, compared with the control group, the device for enhancing carbon sequestration and absorption of floating mud designed in this invention, utilizing multi-anode-single-cathode microbial electrochemistry (SMFC), can improve the humification of floating mud to a certain extent. Compared with the control group, SMFC-4 (N=4) significantly increased the content of humic acid (HA) and fulvic acid (FA) in the floating mud. Figure 4 and Figure 5 This invention converts unstable organic carbon in floating mud into inert organic carbon. Furthermore, the device of this invention improves the humification of floating mud while also suppressing greenhouse gas emissions from lake floating mud. In particular, the SMFC-5 and SMFC-6 treatment groups significantly (p<0.05) suppressed CH4 emission fluxes at 81 days, and exhibited carbon sink characteristics at 114 days. Figure 6 At 81 days, the SMFC-6 treatment group reduced CO2 emission flux, and at 114 days, it exhibited carbon sink characteristics. Figure 7Based on the above test results, the number of parallel anodes in the SMFC device can be set to 4 to 6 groups.

[0071] When the electrode was rotated as a whole, it was found that the CO2 emission flux was 2.3 mg·m³ when the electrode rotation speed was 3 rpm. -2 ·h -1 The CO2 emission flux was significantly lower than that of other treatment groups; when the electrode rotation speed increased to 10 rpm, the CO2 emission flux increased. Figure 8 Similarly, the greenhouse gas methane (CH4) exhibits the largest carbon sink characteristics at an electrode rotation speed of 3 rpm, with a CH4 emission flux of -12.2 μg·m⁻¹. -2 ·h -1 ( Figure 9 ).

[0072] Taking SMFC-3 as an example, the greenhouse gas emission fluxes after rotating the electrode layers (upper, middle, and lower layers) were investigated. Compared with the control group without electrodes, the CO2 emission fluxes of the electrode group were significantly reduced. Compared with the electrode group (0 rpm), the CO2 emission flux was lowest (0.5 mg·m³) when rotating the lower electrode layer. -2 ·h -1 Compared with the control group without electrodes, the CH4 emission flux in the electrode group was significantly reduced, and a carbon sink trend was observed. Compared with the electrode group (0 rpm), when the electrodes were rotated in layers, the CH4 emission flux was lowest when rotating the lower electrode (-7.8 mg·m³). -2 ·h -1 Data results indicate that initiating the rotation of the lower electrode can significantly reduce greenhouse gas emissions during the disposal of floating sludge. Figure 10 , Figure 11 When the device starts rotating the upper and middle layers, its voltage signal is in the range of 30-50mV; when the device starts rotating the lower layer, its voltage signal is in the range of 10-30mV.

[0073] Each SMFC processing group can output voltage signals, and the voltage value gradually decreases over time. Figure 12 The voltage value was increased by paralleling the SMFC anode system; comparatively, the SMFC-5 treatment group had a higher voltage value. Figure 13 ).

[0074] Therefore, when the voltage reaches its peak of 80mV and the voltage signal begins to drop, the impeller is started to rotate as a whole; when the voltage drops below 50mV, the impeller rotates in layers: the upper and middle layers rotate when the voltage is between 30-50mV, and the lower layer rotates when the voltage is between 10-30mV. The device's operating status is monitored in real time by controlling the voltage signal variation range, and the overall and layered rotation of the impeller within the device is implemented according to the voltage signal variation range, thereby controlling greenhouse gas emissions during the floating sludge treatment process and achieving in-situ carbon sequestration and enhancement of lake floating sludge.

Claims

1. A method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds, characterized in that, A device for in-situ lifting of floating mud in lakes and ponds to fix carbon and enhance carbon sequestration is provided. The device includes a floating mud capture tank with an opening at the top and a microbial electrochemical system placed inside the floating mud capture tank. The microbial electrochemical system includes a control system, a cathode, an anode shaft, and several plate-shaped anodes. The cathode floats on the lake surface, while the silt capture tank is located below the lake surface. The anode shaft is vertically positioned inside the sludge capture tank. M anodes of the same height are fixedly connected to a sleeve to form an impeller, and the sleeve is fitted onto the anode shaft. The anode comprises N impellers, which are rotatably connected to the anode shaft at different heights. M and N are independent natural numbers, where N is between 2 and 6. All the anodes are connected in parallel to the cathode via an external resistor to form an external circuit, in which a voltage signal collector is provided. The control system is connected to control the anode, and the control system is electrically connected to the voltage signal collector; The floating mud capture tank of the in-situ lifting and carbon sequestration device for lake floating mud is placed in the area where lake currents converge at the bottom of the lake. Floating mud is collected by hydrodynamics and subjected to in-situ humification treatment in the capture tank. The voltage signal collector obtains the voltage signal in the external circuit and feeds it back to the control system. The control system controls the impeller to rotate when the voltage signal reaches its peak value and begins to fall back down, according to the settings.

2. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 1, characterized in that, The anode is composed of a stainless steel perforated mesh plate and carbon felt attached to the surface of the mesh plate.

3. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 1, characterized in that, M is 2~6.

4. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 3, characterized in that, M is 5.

5. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 1, characterized in that, The distance between adjacent impellers is 1 cm.

6. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 1, characterized in that, The impeller rotates at a speed of 0~10 r / min.

7. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 1, characterized in that, The impeller rotates at a speed of 3 r / min.

8. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 1, characterized in that, The dimensions of the anode are (5~50)cm × (5~50)cm.

9. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 2, characterized in that, The perforated stainless steel mesh has a hole diameter of 0.1~0.5 cm.

10. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 9, characterized in that, The perforated stainless steel mesh has a hole diameter of 0.2 cm.

11. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 1, characterized in that, The cathode is a carbon felt.

12. The method for in-situ enhancement of carbon sequestration and absorption of floating mud in lakes and ponds according to claim 1, characterized in that, The sludge capture tank is cylindrical, with a length, width, and height of (0.8~3)m, (0.8~3)m, and (1.5~3)m, respectively.

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