Constructed wetland-microbial fuel cell system and treatment method

Abstract

The invention discloses a constructed wetland-microbial fuel cell system and a treatment method, and relates to the field of environmental pollution abatement, a treatment device comprises a box body and an outer resistor, the box body is of an inverted conical structure, and a substrate layer, an anode layer, a middle layer, a cathode layer and wetland plants are sequentially arranged in the box body from bottom to top; the area of the minimum horizontal section of the cathode layer is larger than that of the maximum horizontal section of the anode layer; the water inlet mechanism is connected with a first water inlet in the bottom of the box body, a first water outlet in the top of the box body is connected with a second water inlet in the bottom of the backflow filter column, and a second water outlet and a third water outlet are sequentially formed in the upper portion of the backflow filter column from top to bottom. The third water outlet is connected with a third water inlet in the bottom of the box body through a backflow mechanism, and a third water outlet valve is arranged at the third water outlet. According to the system and the treatment method, the removal rate and the electricity generation performance of nitrogen and phosphorus pollutants are improved, the size of a treatment device is reduced, and the space utilization rate is improved.

Description

Technical Field

[0001] The present invention relates to the field of environmental pollution control, and in particular to an artificial wetland-microbial fuel cell system and a treatment method. Background Art

[0002] Artificial wetland-microbial fuel cell technology is an emerging technology that combines traditional artificial wetlands with microbial fuel cells. This technology spontaneously converts chemical energy into electrical energy through the metabolic activities of microorganisms in the electrode, which not only improves the removal capacity of traditional artificial wetlands for complex organic pollutants, but also can sustainably produce clean electricity. Artificial wetland-microbial fuel cell technology has been applied to sewage treatment, chemical production and seawater desalination.

[0003] However, similar to traditional artificial wetlands, artificial wetland-microbial fuel cell systems still have two major drawbacks after long-term operation: poor nitrogen and phosphorus removal performance and decreased power generation performance. In recent years, the commonly used single-chamber CW-MFC device has continued to use a 1:1 cathode and anode area ratio design, increasing the distance between the cathode and anode to achieve a difference in dissolved oxygen content in the electrode area, thereby forming a potential difference, making the device larger and occupying a large space. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a constructed wetland-microbial fuel cell system and treatment method, which improves the removal rate and power generation performance of nitrogen and phosphorus pollutants, reduces the volume of the treatment device and improves space utilization.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides an artificial wetland-microorganism fuel cell system, comprising a water inlet mechanism, a treatment device, a reflux filter column, a water outlet box and a reflux mechanism, wherein the treatment device comprises a box body and an external resistor, wherein the box body is an inverted cone structure, wherein a matrix layer, an anode layer, an intermediate layer, a cathode layer and wetland plants are sequentially arranged in the box body from bottom to top, wherein the area of ​​the minimum horizontal cross section of the cathode layer is greater than the area of ​​the maximum horizontal cross section of the anode layer, and the two ends of the external resistor are respectively connected to the anode layer and the cathode layer; wherein the water inlet mechanism is connected to a first water inlet at the bottom of the box body, and a first water outlet at the top of the box body is connected to a second water inlet at the bottom of the reflux filter column, and a second water outlet and a third water outlet are sequentially arranged in the upper part of the reflux filter column from top to bottom, wherein the second water outlet is connected to the water outlet box, and the third water outlet is connected to the third water inlet at the bottom of the box body through the reflux mechanism, and a third water outlet valve is arranged at the third water outlet.

[0007] Preferably, the processing device further comprises a voltage acquisition module, and the voltage acquisition module is arranged in parallel with the external resistor.

[0008] Preferably, the water inlet mechanism comprises a water inlet box, a water inlet pipe and a water inlet pump, the bottom of the water inlet box is connected to the first water inlet through the water inlet pipe, and the water inlet pump is arranged on the water inlet pipe.

[0009] Preferably, the reflux mechanism comprises a reflux pipe and a reflux pump, the third water outlet is connected to the third water inlet through the reflux pipe, and the reflux pump is provided on the reflux pipe.

[0010] Preferably, a first water inlet valve is provided at the first water inlet, a first water outlet valve is provided at the first water outlet, a second water inlet valve is provided at the second water inlet, a second water outlet valve is provided at the second water outlet, and a third water inlet valve is provided at the third water inlet.

[0011] Preferably, a first metal mesh is disposed in the anode layer, and a second metal mesh is disposed in the cathode layer.

[0012] Preferably, the anode layer and the cathode layer use the same electrode material, which is carbon felt, graphite rod or glass fiber cloth.

[0013] Preferably, the filling heights of the anode layer and the cathode layer are the same.

[0014] Preferably, the matrix layer and the intermediate layer are filled with the same wetland filler, which is gravel, slag or zeolite.

[0015] The present invention also provides a treatment method based on an artificial wetland-microbial fuel cell system, comprising the following steps:

[0016] Step 1, sewage in the water inlet mechanism enters the box through the first water inlet, and the water circulation mode in the box is that water flows in from bottom to top and out from top;

[0017] Step 2: The treated sewage flows into the reflux filter column from the first water outlet and the second water inlet, and the water circulation mode in the reflux filter column is that the water flows in from the bottom and out from the top;

[0018] Step 3, opening the third water outlet valve, the treated sewage is accumulated in the reflux filter column and then flows out from the third water outlet, and enters the box through the third water inlet by using the reflux mechanism;

[0019] Step 4: After completing several cycles, close the third water outlet valve;

[0020] Step 5: After the outlet water accumulates inside the reflux filter column and reaches the second outlet position, it is discharged into the outlet tank.

[0021] Compared with the prior art, the present invention has achieved the following technical effects:

[0022] The treatment device and the reflux filter column in the present invention are flexibly combined, and the treated sewage can be refluxed through the treatment device several times according to the water treatment requirements to ensure that the sewage is in full contact with the filler, thereby improving the treatment effect on the sewage, especially improving the removal rate of nitrogen and phosphorus pollutants in the sewage. The box body is an inverted cone structure, and the area of ​​the cathode layer is larger than the area of ​​the anode layer. The contact area between the cathode layer and oxygen is increased without increasing the overall floor space, thereby increasing the dissolved oxygen content and cathode potential of the cathode layer. When the potential of the lower anode remains unchanged, the increase in the cathode potential will increase the overall potential difference of the treatment device, thereby increasing the power generation. Since the design of increasing the area of ​​the cathode layer guarantees the overall power generation performance of the treatment device, the distance between the cathode layer and the anode layer can be further compressed, thereby reducing the volume of the treatment device and improving space utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a schematic structural diagram of the artificial wetland-microbial fuel cell system provided by the present invention.

[0025] Explanation of the accompanying drawings: 100, artificial wetland-microbial fuel cell system; 1, water inlet tank; 2, water inlet pipe; 3, water inlet pump; 4, box body; 5, matrix layer; 6, anode layer; 7, middle layer; 8, cathode layer; 9, wetland plants; 10, external resistor; 11, voltage acquisition module; 12, first metal mesh; 13, second metal mesh; 14, reflux filter column; 15, water outlet tank; 16, reflux pipe; 17, reflux pump; 18, first water inlet; 19, first water outlet; 20, second water inlet; 21, second water outlet; 22, third water outlet; 23, third water inlet. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The purpose of the present invention is to provide an artificial wetland-microbial fuel cell system and a treatment method, which improves the removal rate of phosphorus pollutants and the power generation performance, reduces the volume of the treatment device and improves the space utilization rate.

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figure 1 As shown, this embodiment provides an artificial wetland-microbial fuel cell system 100, including a water inlet mechanism, a treatment device, a reflux filter column 14, a water outlet box 15 and a reflux mechanism, the treatment device includes a box body 4 and an external resistor 10, the box body 4 is an inverted cone structure, and a matrix layer 5, an anode layer 6, an intermediate layer 7, a cathode layer 8 and a wetland plant 9 are arranged in sequence from bottom to top in the box body 4, the horizontal cross-sectional area of ​​the cathode layer 8 increases from bottom to top, the horizontal cross-sectional area of ​​the anode layer 6 increases from bottom to top, and the area of ​​the smallest horizontal cross-sectional area of ​​the cathode layer 8 is larger than the largest horizontal cross-sectional area of ​​the anode layer 6. area, the two ends of the external resistor 10 are connected to the anode layer 6 and the cathode layer 8 respectively; the water inlet mechanism is connected to the first water inlet 18 at the bottom of the box body 4, the first water outlet 19 at the top of the box body 4 is connected to the second water inlet 20 at the bottom of the reflux filter column 14, and the upper part of the reflux filter column 14 is sequentially provided with a second water outlet 21 and a third water outlet 22 from top to bottom, the second water outlet 21 is connected to the water outlet box 15, and the third water outlet 22 is connected to the third water inlet 23 at the bottom of the box body 4 through the reflux mechanism, the third water inlet 23 is used for the entry of reflux water, and the third water outlet 22 is provided with a third water outlet valve.

[0030] The treatment device in this embodiment is flexibly combined with the reflux filter column 14, and the treated sewage can be refluxed through the treatment device several times according to the water treatment requirements to ensure full contact between the sewage and the filler, thereby improving the treatment effect of the sewage, especially improving the removal rate of nitrogen and phosphorus pollutants in the sewage.

[0031] By setting the box body 4 to an inverted cone structure, the area of ​​the minimum horizontal cross section of the cathode layer 8 is larger than the area of ​​the maximum horizontal cross section of the anode layer 6, and the contact area between the cathode layer 8 and oxygen is increased without increasing the overall floor area, and the utilization rate of oxygen by the aerobic cathode layer 8 on the surface is increased, thereby increasing the dissolved oxygen content and cathode potential of the cathode layer 8. When the potential of the lower anode remains unchanged, the increase in the cathode potential will increase the overall potential difference of the treatment device, thereby increasing the power generation. Since the design of increasing the area of ​​the cathode layer 8 guarantees the overall power generation performance of the treatment device, the distance between the cathode layer 8 and the anode layer 6 can be further compressed, thereby reducing the volume of the treatment device and improving space utilization.

[0032] The processing device in this embodiment further includes a voltage acquisition module 11 , which is arranged in parallel with the external resistor 10 , so as to perform real-time acquisition of the voltage of the processing device.

[0033] Specifically, the water inlet mechanism includes a water inlet box 1 , a water inlet pipe 2 and a water inlet pump 3 . The bottom of the water inlet box 1 is connected to the first water inlet 18 through the water inlet pipe 2 , and the water inlet pipe 2 is provided with a water inlet pump 3 .

[0034] Specifically, the reflux mechanism includes a reflux pipe 16 and a reflux pump 17 . The third water outlet 22 is connected to the third water inlet 23 via the reflux pipe 16 . The reflux pipe 16 is provided with the reflux pump 17 .

[0035] In this embodiment, the system operates in a continuous water inlet mode, the speed of the water inlet pump 3 is constant, and the speed of the reflux pump 17 is adjusted according to the required reflux ratio. By adjusting the reflux ratio, the in-situ enhanced removal of nitrogen and phosphorus in the sewage is achieved, and the treatment effect of the treatment device on nitrogen and phosphorus is improved.

[0036] In order to facilitate the control of the opening and closing of the first water inlet 18, the first water outlet 19, the second water inlet 20, the second water outlet 21 and the third water inlet 23, a first water inlet valve is provided at the first water inlet 18, a first water outlet valve is provided at the first water outlet 19, a second water inlet valve is provided at the second water inlet 20, a second water outlet valve is provided at the second water outlet 21, and a third water inlet valve is provided at the third water inlet 23.

[0037] In order to enhance the electron collection capability of the electrode, a first metal mesh 12 is provided in the anode layer 6 , and a second metal mesh 13 is provided in the cathode layer 8 .

[0038] In the present embodiment, the first metal mesh 12 and the second metal mesh 13 are both stainless steel meshes, and the wire diameter of the stainless steel mesh is 0.21 mm, the aperture is 1.1 mm, and the mesh number is 20.

[0039] In this embodiment, the electrode material used for the anode layer 6 and the cathode layer 8 is the same. Specifically, the electrode material is carbon felt, graphite rod or glass fiber cloth.

[0040] Specifically, the filling heights of the anode layer 6 and the cathode layer 8 are the same. In this embodiment, the ratio of the maximum horizontal cross-sectional area of ​​the cathode layer 8 to the maximum horizontal cross-sectional area of ​​the anode layer 6 is 2:1 to 2.56:1.

[0041] In this embodiment, the anode layer 6 and the cathode layer 8 are connected to an external resistor 10 of 1000Ω to 2500Ω via a titanium wire.

[0042] In this embodiment, the matrix layer 5 and the intermediate layer 7 are filled with the same wetland filler, specifically, the wetland filler is gravel, slag or zeolite.

[0043] A certain density of wetland plants 9 is planted in the cathode layer 8, and large aquatic plants are usually selected, such as cattails, reeds, calamus, etc.

[0044] This embodiment also provides a treatment method based on the artificial wetland-microbial fuel cell system 100, comprising the following steps:

[0045] Step 1. The sewage in the water inlet mechanism enters the box body 4 through the first water inlet 18, and the water circulation mode in the box body 4 is that water flows in from bottom to top; specifically, the first water inlet valve is opened, and the sewage in the water inlet tank 1 is transported to the box body 4 through the water inlet pump 3.

[0046] Step 2: Open the first water outlet valve and the second water inlet valve, and the treated sewage flows into the reflux filter column 14 from the first water outlet 19 and the second water inlet 20. The water circulation mode in the reflux filter column 14 is that the water flows in from the bottom and out from the top.

[0047] Step three, open the third water outlet valve and the third water inlet valve, the treated sewage accumulates in the reflux filter column 14 and flows out from the third water outlet 22, and enters the box 4 through the third water inlet 23 by the reflux mechanism; specifically, the reflux pump 17 is used to make the treated sewage flow back into the box 4.

[0048] Step 4: After completing several cycles, close the third water outlet valve and the third water inlet valve.

[0049] Step 5: Open the second water outlet valve. After the water accumulates inside the reflux filter column 14 and reaches the position of the second water outlet 21 , it is discharged into the water outlet tank 15 .

[0050] In this specific embodiment, the resistance value of the external resistor 10 is 1000Ω, the height of the processing device is 60cm, the filling heights of the matrix layer 5 and the intermediate layer 7 are both 20cm, the filling heights of the anode layer 6 and the cathode layer 8 are both 10cm, and the ratio of the maximum horizontal cross-sectional area of ​​the cathode layer 8 to the maximum horizontal cross-sectional area of ​​the anode layer 6 is 2.56:1. The cathode layer 8 and the anode layer 6 both use activated carbon particles with a particle diameter of 3mm to 5mm as electrode materials, and yellow calamus is selected to be planted on the upper part of the cathode layer 8, and the planting density is 100 plants / m 2 .

[0051] In this embodiment, the ambient temperature is controlled at 25°C to 28°C, the sewage flow rate is adjusted by the water inlet pump 3 and the reflux pump 17, the hydraulic retention time is 72 hours, and the outside of the treatment device is wrapped with tin foil to avoid light and prevent algae growth.

[0052] The system was operated continuously for 60 days, and the effluent quality was sampled and measured every 3 days. The voltage data was collected in real time using the voltage acquisition module 11. When the initial COD concentration of rural domestic sewage in a certain place was 300-400 mg / L and the return ratio was 300%, the maximum removal rate of TP in the sewage by the system was 63.64%, which was 11% higher than the phosphorus removal rate of the traditional artificial wetland system.

[0053] The design of increasing the cathode area also improves the power generation performance of the treatment device. In terms of voltage, when the reflux ratio is 300%, the highest average voltage is 567.93±0.84mV. In addition, when the reflux ratio is 200%, the highest power density is 347.84mW / m 3 When the reflux ratio is 200%, the system internal resistance is only 44.05Ω, which is significantly lower than that of the conventional cathode configuration CW-MFC device.

[0054] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An artificial wetland-microbial fuel cell system, characterized in that: It includes a water inlet mechanism, a treatment device, a reflux filter column, a water outlet box and a reflux mechanism. The treatment device includes a box body and an external resistor. The box body is an inverted cone structure. A matrix layer, an anode layer, an intermediate layer, a cathode layer and wetland plants are arranged in sequence from bottom to top in the box body. The area of ​​the minimum horizontal cross-section of the cathode layer is larger than the area of ​​the maximum horizontal cross-section of the anode layer. The two ends of the external resistor are respectively connected to the anode layer and the cathode layer; the water inlet mechanism is connected to the first water inlet at the bottom of the box body, the first water outlet at the top of the box body is connected to the second water inlet at the bottom of the reflux filter column, and the upper part of the reflux filter column is sequentially provided with a second water outlet and a third water outlet from top to bottom, the second water outlet is connected to the water outlet box, the third water outlet is connected to the third water inlet at the bottom of the box body through the reflux mechanism, and a third water outlet valve is arranged at the third water outlet.

2. The artificial wetland-microbial fuel cell system according to claim 1, characterized in that: The processing device further comprises a voltage acquisition module, and the voltage acquisition module is arranged in parallel with the external resistor.

3. The artificial wetland-microbial fuel cell system according to claim 1, characterized in that: The water inlet mechanism comprises a water inlet box, a water inlet pipe and a water inlet pump. The bottom of the water inlet box is connected to the first water inlet through the water inlet pipe, and the water inlet pump is arranged on the water inlet pipe.

4. The artificial wetland-microbial fuel cell system according to claim 1, characterized in that: The reflux mechanism comprises a reflux pipe and a reflux pump. The third water outlet is connected to the third water inlet through the reflux pipe, and the reflux pump is arranged on the reflux pipe.

5. The artificial wetland-microbial fuel cell system according to claim 1, characterized in that: A first water inlet valve is provided at the first water inlet, a first water outlet valve is provided at the first water outlet, a second water inlet valve is provided at the second water inlet, a second water outlet valve is provided at the second water outlet, and a third water inlet valve is provided at the third water inlet.

6. The artificial wetland-microbial fuel cell system according to claim 1, characterized in that: A first metal mesh is disposed in the anode layer, and a second metal mesh is disposed in the cathode layer.

7. The artificial wetland-microbial fuel cell system according to claim 1, characterized in that: The electrode material used for the anode layer and the cathode layer is the same, and the electrode material is carbon felt, graphite rod or glass fiber cloth.

8. The artificial wetland-microbial fuel cell system according to claim 1, characterized in that: The anode layer and the cathode layer have the same filling height.

9. The artificial wetland-microbial fuel cell system according to claim 1, characterized in that: The base layer and the middle layer are filled with the same wetland filler, which is gravel, slag or zeolite.

10. A treatment method based on the artificial wetland-microbial fuel cell system according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1, sewage in the water inlet mechanism enters the box through the first water inlet, and the water circulation mode in the box is that water flows in from bottom to top and out from top; Step 2: The treated sewage flows into the reflux filter column from the first water outlet and the second water inlet, and the water circulation mode in the reflux filter column is that the water flows in from the bottom and out from the top; Step 3, opening the third water outlet valve, the treated sewage is accumulated in the reflux filter column and then flows out from the third water outlet, and enters the box through the third water inlet by using the reflux mechanism; Step 4: After completing several cycles, close the third water outlet valve; Step 5: After the outlet water accumulates inside the reflux filter column and reaches the second outlet position, it is discharged into the outlet tank.

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