A microbial electrochemical floating island device and a method for in-situ repair of riverbed sediment

Abstract

The present invention provides a microbial electrochemical floating island device and a method for in-situ repair of riverbed mud, which belongs to the technical field of riverbed mud management. The microbial electrochemical floating island device provided by the present invention includes a floating island skeleton, an air cathode and a sediment anode, wherein the air cathode is arranged on the floating island skeleton, and the air cathode is connected to the sediment anode through a wire, the wire is inserted into a fixed rope, and one end of the fixed rope is connected to the floating island skeleton; wherein the electrode materials of the air cathode and the sediment anode are obtained by pyrolysis of iron-rich sludge under anoxic or anaerobic conditions. The microbial electrochemical floating island device provided by the present invention is an in-situ repair device for riverbed mud, which can effectively reduce the release of nitrogen, phosphorus and organic matter in riverbed mud, repair the river water body while repairing the riverbed mud, improve the water quality of the river, and has high repair efficiency and is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of riverbed sediment treatment, and in particular to a microbial electrochemical floating island device and a method for in-situ repair of riverbed sediment. Background Art

[0002] With rapid economic development, untreated industrial wastewater, domestic sewage, farmland runoff, and other harmful substances are entering rivers directly, causing water and sediment pollution, such as black and odorous water bodies and eutrophication. Although measures such as controlling pollution sources have effectively reduced the entry of pollutants into water bodies in recent years, endogenous pollutants released from river sediments remain a major challenge in water remediation.

[0003] Artificial floating islands are widely used in river restoration because they require no additional land and offer attractive landscape benefits. However, due to limitations in plant growth, artificial floating islands are unable to repair river sediments, and their treatment efficiency is low. Summary of the Invention

[0004] The purpose of the present invention is to provide a microbial electrochemical floating island device and a method for in-situ repair of riverbed mud. The microbial electrochemical floating island device provided by the present invention can effectively reduce the release of nitrogen, phosphorus and organic matter in riverbed mud, repair the river water body while repairing the riverbed mud, with good comprehensive repair effect and high repair efficiency.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a microbial electrochemical floating island device, comprising a floating island skeleton, an air cathode and a bottom mud anode. The air cathode is arranged on the floating island skeleton, and the air cathode is connected to the bottom mud anode via a wire. The wire is inserted into a fixed rope, and one end of the fixed rope is connected to the floating island skeleton. The electrode materials of the air cathode and the bottom mud anode are obtained by pyrolysis of iron-rich sludge under anoxic or anaerobic conditions.

[0007] Preferably, the iron content in the iron-rich sludge is 0.8-1.2 wt%; the pyrolysis temperature is 400-800° C., and the holding time is 1-4 h.

[0008] Preferably, the air cathode and the bottom mud anode include the electrode material and a stainless steel mesh wrapped around the surface of the electrode material.

[0009] Preferably, the floating island skeleton is obtained by sintering skeleton preparation raw materials in an air atmosphere; the total content of silicon dioxide and aluminum oxide in the skeleton preparation raw materials is greater than 80wt%.

[0010] Preferably, the skeleton preparation raw materials include one or more of kaolin, water supply sludge, sewage sludge, riverbed mud, slag and fly ash; the firing temperature is 850-1050° C., and the holding time is 1-2 hours.

[0011] Preferably, the microbial electrochemical floating island device further comprises a fixed anchor device, and the fixed anchor device is connected to the other end of the fixed rope.

[0012] Preferably, the conductor is covered with a protective tube, and the conductor covered with the protective tube is inserted into the fixing rope.

[0013] Preferably, the microbial electrochemical floating island device further includes plants, and the plants are planted on the floating island skeleton.

[0014] The present invention provides a method for in-situ repair of riverbed sediment, comprising the following steps:

[0015] The bottom mud anode of the microbial electrochemical floating island device described in the above technical solution is placed on the surface of the bottom mud of the river to be repaired, and part of the air cathode is immersed in the water of the river to be repaired for in-situ repair treatment.

[0016] Preferably, the air cathode immersed in the water body of the river to be repaired accounts for 65-75% of the total volume of the air cathode.

[0017] The present invention provides a microbial electrochemical floating island device, comprising a floating island skeleton, an air cathode, and a sediment anode. The air cathode is mounted on the floating island skeleton and connected to the sediment anode via a wire inserted through a fixed rope, one end of which is connected to the floating island skeleton. The electrode materials of the air cathode and sediment anode are obtained by pyrolysis of iron-rich sludge under anoxic or anaerobic conditions. The microbial electrochemical floating island device provided by the present invention is an in-situ riverbed sediment remediation device that can effectively reduce the release of nitrogen, phosphorus, and organic matter from riverbed sediment, repairing the riverbed sediment while simultaneously repairing the river water, thereby improving river water quality, with high remediation efficiency and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the microbial electrochemical floating island device of the present invention, wherein 1 is the floating island skeleton, 2 is the air cathode, 3 is the bottom mud anode, 4 is the fixed rope with a wire inside (and the wire is covered with a protective tube), 5 is the fixed anchor device, and 6 is the plant;

[0019] Figure 2 This is the N1s XPS spectrum of the electrode material obtained by pyrolysis at 400℃ for 2h;

[0020] Figure 3This is the N1s XPS spectrum of the electrode material obtained by pyrolysis at 800℃ for 2h;

[0021] Figure 4 This is the N1s XPS spectrum of the electrode material obtained by pyrolysis at 800℃ for 1h;

[0022] Figure 5 This is the N1s XPS spectrum of the electrode material obtained by pyrolysis at 600℃ for 4h;

[0023] Figure 6 This is the N1s XPS spectrum of the electrode material obtained by pyrolysis at 600℃ for 1h;

[0024] Figure 7 is the CV curve of the electrode material;

[0025] Figure 8 This is a graph showing the relationship between the total content of pyridinic nitrogen and graphitic nitrogen in the electrode material and its conductive properties;

[0026] Figure 9 This is the Fe2p XPS spectrum of the electrode material;

[0027] Figure 10 It is a schematic diagram of a simulation experiment based on the microbial electrochemical floating island device of the present invention and a diagram of the treatment effect after 30 days of operation. DETAILED DESCRIPTION

[0028] The present invention provides a microbial electrochemical floating island device, comprising a floating island skeleton, an air cathode and a bottom mud anode. The air cathode is arranged on the floating island skeleton, and the air cathode is connected to the bottom mud anode via a wire. The wire is inserted into a fixed rope, and one end of the fixed rope is connected to the floating island skeleton. The electrode materials of the air cathode and the bottom mud anode are obtained by pyrolysis of iron-rich sludge under anoxic or anaerobic conditions.

[0029] The microbial electrochemical floating island device provided by the present invention includes a floating island skeleton. In the present invention, the floating island skeleton is preferably obtained by firing skeleton preparation raw materials in an air atmosphere; the total content of silica and alumina in the skeleton preparation raw materials is preferably greater than 80wt%, more preferably 81-90wt%. In the present invention, the skeleton preparation raw materials preferably include one or more of kaolin, water supply sludge, sewage sludge, riverbed mud, slag and fly ash, more preferably kaolin and water supply sludge; when the skeleton preparation raw materials are kaolin and water supply sludge, the mass ratio of kaolin to water supply sludge is preferably 3: (2-3), more preferably 3: 2. The present invention preferably uses the above-mentioned types of skeleton preparation raw materials, such as water supply sludge, sewage sludge, riverbed mud, etc., which can achieve their reuse, and can also avoid the secondary pollution caused by the use of traditional floats (such as plastic floats), achieving waste treatment with waste, and high economic benefits.

[0030] The present invention preferably mixes the skeleton raw materials with water to obtain a slurry; the slurry is placed in a mold and pressed into shape to obtain a molding compound; and the molding compound is fired in an air atmosphere to obtain a floating island skeleton. In the present invention, when the skeleton raw materials contain at least one of water supply sludge, sewage sludge, and bottom mud, the water supply sludge, sewage sludge, and bottom mud are preferably dried and crushed in sequence before use. The drying temperature is preferably 100-110°C, more preferably 105°C. The present invention does not specify the drying time, as long as sufficient drying is ensured. The present invention preferably crushes the dried sludge to a particle size of less than 63 μm. In the present invention, the mass ratio of the skeleton raw materials to water is preferably 1:(0.9-1.1), more preferably 1:1. The present invention does not specify the compression molding method, and methods familiar to those skilled in the art can be used. In an embodiment of the present invention, the dimensions of the molding compound are specifically 30 cm × 30 cm × 60 cm. In the present invention, the firing temperature is preferably 850-1050° C., more preferably 1000° C.; the holding time is preferably 1-2 hours, more preferably 1.5 hours.

[0031] In the present invention, a block material is obtained after the firing; the present invention preferably splices a plurality of the block materials to obtain the floating island skeleton. The present invention preferably utilizes substances such as silicon dioxide, polyferric sulfate or polyaluminum chloride contained in the skeleton preparation raw materials, which can be used to supplement elements such as aluminum and silicon. Ceramsite can be formed after firing in an air atmosphere. Organic matter, appropriate iron elements and water are conducive to the formation of a porous structure, so that the block material obtained after firing has a lower density and greater buoyancy. Specifically, the buoyancy of the block material of the present invention is greater than 45kg per square meter, and no other floating device is required to provide buoyancy. Moreover, the block material of the present invention has high strength, a compressive strength of up to 3.08MPa, and strong wear resistance and corrosion resistance, making it suitable for use as a floating island skeleton.

[0032] The microbial electrochemical floating island device provided by the present invention includes an air cathode and a sediment anode. The air cathode is arranged on the floating island skeleton and is connected to the sediment anode via a wire. In the present invention, the air cathode and sediment anode preferably include an electrode material and a stainless steel mesh wrapped around the surface of the electrode material; the stainless steel mesh is preferably a 304 stainless steel mesh, preferably with a pore size of 1mm and a wire diameter of 0.6mm. In the present invention, the air cathode and sediment anode are preferably in block shape; in an embodiment of the present invention, the dimensions of the air cathode and sediment anode are specifically 30cm×30cm×60cm.

[0033] In the present invention, the electrode materials for the air cathode and bottom mud anode are obtained by pyrolysis of iron-rich sludge under anoxic or anaerobic conditions. In the present invention, the iron content in the iron-rich sludge is preferably 0.8-1.2 wt%, more preferably 0.85 wt%; the iron-rich sludge is preferably iron-rich sewage sludge. After the iron-rich sludge is pyrolyzed to obtain the sludge carbon material, the sludge carbon material is preferably crushed and sieved in sequence, and sludge carbon material with a particle size greater than 1 mm (to ensure that it can be wrapped by the stainless steel mesh) is selected as the electrode material for the air cathode and bottom mud anode. The particle size of the electrode material is preferably as small as possible on the basis of being greater than 1 mm, for example, it can be 1.1-1.5 mm. In the present invention, the pyrolysis temperature is preferably 400-800°C, more preferably 500-600°C; the holding time is preferably 1-4 hours, more preferably 1-2 hours. In the present invention, the pyrolysis is carried out under anoxic or anaerobic conditions; the anoxic conditions preferably refer to an oxygen volume fraction of less than 0.5%. In the present invention, the surface of the electrode material obtained after pyrolysis of iron-rich sludge under anoxic or anaerobic conditions contains rich pyridinic nitrogen and graphitic nitrogen (i.e., nitrogen element exists in the form of graphitic nitrogen and pyridinic nitrogen), which can catalyze redox reactions and enhance conductivity. The iron element on the surface of the electrode material exists in the form of Fe2O3 and FeO. When it is used as an air cathode, the presence of Fe(III) makes the cathode open circuit voltage higher, reaching 400-500mV (5-10% higher than that of ordinary activated carbon air cathode); at the same time, when it is used as a sediment anode and placed on the surface of the riverbed sediment to be repaired, its carbon skeleton structure is conducive to the formation of Geobacter spp. r) and other conductive microorganisms grow (a biofilm composed of bacteria, fungi, etc. will form on the surface of the sediment anode), which can convert the chemical energy in the organic matter into electrical energy, thereby facilitating the improvement of the degradation rate of organic matter in the riverbed mud (the organic matter degradation rate can be increased by 20%); in addition, Fe(II) can promote autotrophic denitrification, which is conducive to improving the total nitrogen removal rate (the total nitrogen removal rate can be increased by 5%); Fe(III) can adsorb phosphorus in the riverbed mud and form a stable complex with phosphate (it can convert 30% of the adsorbed phosphorus in the riverbed mud into iron-bound phosphorus), preventing the phosphorus in the riverbed mud from being released into the water body and causing eutrophication pollution of the lake water body. Therefore, the present invention connects the air cathode and the sediment anode through a wire to form a microbial fuel cell system, which can enhance the removal of organic pollutants and nitrogen in the riverbed mud, while reducing the release of endogenous pollutants such as phosphorus (the removal efficiency of nitrogen, phosphorus and organic matter is improved by 5-30%), and is conducive to the restoration of the river ecological environment.

[0034] In the present invention, the conductor is inserted into a fixing rope, one end of which is connected to the floating island frame. The fixing rope is preferably made of a polymer material, preferably aramid or ultra-high molecular weight polyethylene fiber (UHMWPE, a fiber spun from polyethylene with a molecular weight of 1 million to 5 million). The present invention preferably uses fixing ropes made of these materials for their high strength and good wear resistance.

[0035] In one embodiment of the present invention, the conductor is encased in a protective tube, which is inserted into a retaining rope. The protective tube is preferably a polyethylene (PE) hose or a polytetrafluoroethylene (PTFE) hose. These types of protective tubes are preferred for their excellent corrosion resistance. The protective tube and retaining rope protect the conductor, making it less susceptible to damage.

[0036] As an embodiment of the present invention, the microbial electrochemical floating island device provided by the present invention also includes a fixed anchor device, which is connected to the other end of the fixed rope, that is, the two ends of the fixed rope are respectively connected to the floating island skeleton and the fixed anchor device; when the microbial electrochemical floating island device is used to perform in-situ repair treatment on the bottom mud of the river channel to be repaired, the fixed anchor device is fixed in the bottom mud of the river channel to be repaired.

[0037] As one embodiment of the present invention, the microbial electrochemical floating island device further includes plants planted on the floating island framework. In the present invention, the plants are preferably emergent plants; preferably, the emergent plants include one or more of white spiderwort, cattail, calamus, and lily of the valley. Planting plants on the floating island framework provides certain landscape benefits.

[0038] Figure 1 The schematic diagram of the structure of the microbial electrochemical floating island device of the present invention is shown in FIG1 , wherein 1 is the floating island skeleton, 2 is the air cathode, 3 is the bottom mud anode, 4 is the fixed rope with a wire inside (and the wire is covered with a protective tube), 5 is the fixed anchor device, and 6 is the plant; Figure 1 To illustrate the method for in-situ repair of riverbed sediment in the present invention.

[0039] The present invention provides a method for in-situ repair of riverbed sediment, comprising the following steps:

[0040] The bottom mud anode of the microbial electrochemical floating island device described in the above technical solution is placed on the surface of the bottom mud of the river to be repaired, and part of the air cathode is immersed in the water of the river to be repaired for in-situ repair treatment.

[0041] In the present invention, the air cathode submerged in the water of the river to be repaired preferably accounts for 65-75% of the total volume of the air cathode, more preferably 70%. The present invention preferably immerses the air cathode at this volume fraction in the water of the river to be repaired, which can catalyze oxygen reduction and facilitate pollutant removal. In the present invention, the fixed anchor device in the microbial electrochemical floating island device is preferably fixed in the bottom mud of the river to be repaired.

[0042] The present invention has no special restrictions on the conditions of the in-situ repair treatment, and it can be carried out under natural environmental conditions without the need to specifically set conditions such as temperature and humidity.

[0043] The method of the present invention has a wide range of applications, and can be used to repair riverbed mud in black and smelly water bodies or riverbed mud in old urban areas.

[0044] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] Example 1

[0046] according to Figure 1 Construct a microbial electrochemical floating island device, including a floating island skeleton, an air cathode, a bottom mud anode, a fixed anchor device, and emergent plants. The air cathode is arranged on the floating island skeleton, and the air cathode is connected to the bottom mud anode via a wire. The wire is provided with a protective tube (specifically a PE hose) through the outer shell and inserted into a fixed rope (made of ultra-high molecular weight polyethylene fiber). One end of the fixed rope is connected to the floating island skeleton, and the other end is connected to the fixed anchor device. The emergent plants are planted on the floating island skeleton.

[0047] The floating island skeleton is prepared as follows: water plant sludge is dried at 105°C and then crushed to a particle size of less than 63 μm. The resulting water plant sludge particles, kaolin, and water are mixed in a mass ratio of 2:3:1. The resulting slurry is placed in a mold and pressed into a mold to obtain a molding material (measuring 30 cm × 30 cm × 60 cm). The molding material is sintered in air at 1000°C for 1.5 hours to obtain a block material (with a total content of silica and alumina of 81 wt%). Two of the block materials are spliced ​​to form a floating island skeleton, with a buoyancy of 45.3 kg per square meter and a compressive strength of 3.08 MPa.

[0048] The air cathode and bottom mud anode are prepared as follows: iron-rich sewage sludge (iron content of 0.85 wt%) is pyrolyzed at 600°C for 1 hour under anaerobic conditions, and a sludge carbon material with a particle size of 1.1 to 1.5 mm is obtained by crushing and screening; a 304 stainless steel mesh (pore size of 1 mm, wire diameter of 0.6 mm) is wrapped on the surface of the sludge carbon material to obtain an air cathode and a bottom mud anode (both with dimensions of 30 cm × 30 cm × 60 cm);

[0049] The emergent plants include white spiderwort.

[0050] The method for in-situ remediation of riverbed sediment using the microbial electrochemical floating island device comprises the following steps:

[0051] The sediment anode of the microbial electrochemical floating island device is placed on the surface of the sediment of the river channel to be repaired, the fixed anchor device is fixed in the sediment of the river channel to be repaired, and 70% of the total volume of the air cathode is immersed in the water body of the river channel to be repaired, and in-situ repair treatment is carried out under natural environmental conditions.

[0052] Characterization and performance testing

[0053] Figures 2 to 8 These are the characterization diagrams and performance test diagrams of the electrode materials prepared by pyrolysis of iron-rich sewage sludge under different conditions. Figure 2 This is the N1sXPS spectrum of the electrode material obtained by pyrolysis at 400℃ for 2h. Figure 3 This is the N1sXPS spectrum of the electrode material obtained by pyrolysis at 800℃ for 2h. Figure 4 This is the N1sXPS spectrum of the electrode material obtained by pyrolysis at 800℃ for 1h. Figure 5 This is the N1sXPS spectrum of the electrode material obtained by pyrolysis at 600℃ for 4h. Figure 6 This is the N1sXPS spectrum of the electrode material obtained by pyrolysis at 600℃ for 1h. Figure 7 is the CV curve of the electrode material, Figure 8 The graph shows the relationship between the total content of pyridinic nitrogen and graphitic nitrogen in the electrode material and its conductive properties. Figures 2 to 8 It can be seen that the content of pyridinic nitrogen and graphitic nitrogen in the electrode material is proportional to its conductive properties. Electrode materials with higher pyridinic nitrogen and graphitic nitrogen content have better electron transfer properties, and using them in air cathodes can increase the open circuit voltage.

[0054] Figure 9 is the Fe2pXPS spectrum of the electrode material (pyrolysis temperature is 600℃, holding time is 1h), Figure 9 It can be seen that the iron on the surface of the electrode material mainly exists in the form of Fe2O3 and FeO.

[0055] Figure 10This is a schematic diagram of a simulation experiment based on the microbial electrochemical floating island device of the present invention and a diagram of the treatment effect after 30 days of operation. A control group of traditional floating islands (specifically, a commercial floating island device with plastic as the float) was also set up. Figure 10 It can be seen that after 30 days of operation, the removal rates of total organic carbon, total nitrogen and available phosphorus in the riverbed mud (total organic carbon content is 12.3wt%, total nitrogen content is 2075mg / kg, and available phosphorus content is 57.2mg / kg) are significantly improved compared with the traditional floating island control group. Specifically, the removal rates of total organic carbon, total nitrogen and available phosphorus in the control group are 40.7%, 6.3% and 1.1%, respectively, while when using the microbial electrochemical floating island device of the present invention, the removal rates of total organic carbon, total nitrogen and available phosphorus are 67.8%, 16.8% and 32.6%, respectively.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A microbial electrochemical floating island device, comprising a floating island skeleton, an air cathode, a bottom mud anode, and a fixed anchor device, wherein the air cathode is disposed on the floating island skeleton and connected to the bottom mud anode via a wire, the wire being inserted into a fixed rope, one end of the fixed rope being connected to the floating island skeleton, and the fixed anchor device being connected to the other end of the fixed rope; wherein: The electrode materials of the air cathode and the bottom mud anode are obtained by pyrolysis of iron-rich sludge under anoxic or anaerobic conditions; the iron content of the iron-rich sludge is 0.8-1.2 wt %; the pyrolysis temperature is 600° C. and the holding time is 1 hour; The floating island skeleton is obtained by firing skeleton preparation raw materials in an air atmosphere; the total content of silicon dioxide and aluminum oxide in the skeleton preparation raw materials is 81-90wt%; the skeleton preparation raw materials are kaolin and water supply sludge, and the mass ratio of kaolin to water supply sludge is 3:(2-3); the firing temperature is 1000-1050°C, and the insulation time is 1-2h.

2. The microbial electrochemical floating island device according to claim 1, characterized in that: The air cathode and the bottom mud anode include the electrode material and a stainless steel mesh wrapped around the surface of the electrode material.

3. The microbial electrochemical floating island device according to claim 1, characterized in that: The outer sleeve of the conductor is provided with a protection tube, and the conductor covered with the protection tube is inserted into the fixing rope.

4. The microbial electrochemical floating island device according to claim 1, characterized in that: Also included are plants, which are planted on the floating island skeleton.

5. A method for in-situ remediation of riverbed sediment, using the microbial electrochemical floating island device according to any one of claims 1 to 4, comprising the following steps: The sediment anode of the microbial electrochemical floating island device is placed on the surface of the sediment of the river to be repaired, and part of the air cathode is immersed in the water of the river to be repaired to perform in-situ repair treatment.

6. The method according to claim 5, characterized in that The air cathode immersed in the water body of the river to be repaired accounts for 65-75% of the total volume of the air cathode.

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