A device and method for removing Cr(VI) in water by using a bio-electrochemical system

Abstract

The present application belongs to the technical field of sewage remediation, and particularly relates to a device and method for removing Cr(VI) in water by using a bioelectrochemical system. The device is a three-chamber double-biological-cathode electrochemical treatment structure with a cathode chamber, an anode chamber and a cathode chamber. The anode chamber is separated from the cathode chamber by proton exchange membranes on both sides, and the two cathode chambers are connected by a communication pipe. The water inlet and outlet are arranged in a stereoscopic opposite oblique angle manner, so that the wastewater has more residence time and contact area with the electrode in the bioelectrochemical treatment system. The method of the present application uses the mode that iron (II) oxidizing bacteria functional flora adheres to the cathode electrode, has strong resistance to Cr(VI), removes Cr(VI) in the solution by using the biological mineralization of Fe(II) oxidizing bacteria flora in the form of adsorption and co-precipitation, and the removal rate can reach 99.98%. Cr(VI) is removed in the cathode, and stable power generation can be realized at the same time, which is more environmentally friendly and energy-saving.

Description

Technical Field

[0001] This invention belongs to the field of wastewater remediation technology, specifically relating to an apparatus and method for removing Cr(VI) from water using a bioelectrochemical system. Background Technology

[0002] Traditional methods for recovering and removing Cr from wastewater or groundwater include ion exchange, chemical precipitation, electrolysis, biological methods, and adsorption. These methods suffer from drawbacks such as high energy consumption, high chemical consumption, the generation of excess secondary products, and high concentrations of residual toxic sludge. For example, while chemical precipitation is simple to operate, it easily generates secondary pollution, requires additional power, and is costly; biological methods, although low-cost, have long treatment cycles and are also prone to secondary pollution.

[0003] Existing bioelectrochemical systems designed for Cr(VI) reduction lack the ability to provide electrons continuously and stably over a relatively long period. They have a shorter electron-providing cycle and lower stability than sludge, and require frequent replacements, which is detrimental to the stable reduction of Cr(VI) at the cathode and increases system costs.

[0004] Iron-oxidizing bacteria: These are a group of prokaryotes that can utilize iron as an electron donor and oxygen as an electron acceptor for metabolism. They can oxidize Fe... 2+ It generates energy by reducing sulfur compounds and fixing carbon dioxide in the environment. It can be used to effectively remove iron and manganese. By using iron-oxidizing bacteria and limestone as an adsorbent, iron and manganese can be removed from groundwater more effectively. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an apparatus and method for removing Cr(VI) from water using a bioelectrochemical system. The apparatus has a three-chamber dual-biocathode electrochemical treatment system. The cathode adopts the method of degrading Cr(VI) using iron-oxidizing bacteria functional flora. It can achieve long-term stable operation and has the advantages of high treatment efficiency, low cost, and harmless and environmentally friendly treatment products. Moreover, it can generate electricity on its own without the need for an additional power source.

[0006] The technical solution adopted is as follows:

[0007] A device for removing Cr(VI) from water using a bioelectrochemical system includes a cathode, an anode, a cathode chamber, and an anode chamber. Two cathode chambers are provided, and an anode chamber is provided between the two cathode chambers. The two sides of the anode chamber are separated from the cathode chamber by proton exchange membranes.

[0008] One cathode chamber has a cathode inlet at the lower left corner of its front and a connecting port at the lower right corner; the other cathode chamber has a connecting port at the lower left corner of its front and a cathode outlet at the upper right corner of its back, and the two connecting ports are connected by a connecting pipe; the anode chamber has an anode inlet at the lower left corner of its front and an anode outlet at the upper right corner of its back.

[0009] A vertically downward-facing anode is installed at the top center of the anode chamber, and anaerobic electrogenic microorganisms are attached to the anode. A vertically downward-facing cathode is installed at the center of each cathode chamber, and iron(II) oxidizing bacteria are attached to each cathode, forming a three-chamber dual-biocathode electrochemical treatment system. One cathode is connected to an external electrical device via a connecting wire, and the two cathodes are connected by a connecting wire. The electrical device can be a resistor, energy storage device, fan, or other electrical components.

[0010] Preferably, the cathode and anode are carbon brush electrodes.

[0011] Preferably, the pretreatment method for the carbon brush electrode before use is as follows: soak it in 0.5M dilute nitric acid, acetone, ethanol, and deionized water for one day respectively, and after each change of the washing solution, ultrasonically vibrate it for 1 hour.

[0012] Preferably, the top of the anode chamber is sealed, while the top of each cathode chamber is open.

[0013] Preferably, the cultivation method of the anodic anaerobic electrogenic microbial membrane is as follows: anaerobic sludge is used as the anode inoculum and cultured with an anode culture medium. The anode culture medium includes Na2HPO4·12H2O, KH2PO4, NaCl, MgSO4·7H2O, CaCl2, CH3COONa, and trace elements, wherein the trace elements include nitric acid triacetic acid, MgSO4·7H2O, MnSO4·H2O, NaCl, CuSO4·5H2O, KAl(SO4)2, H3BO3, FeSO4·7H2O, CaCl2·2H2O, CoCl2·6H2O, ZnSO4·7H2O, and Na2MoO4.

[0014] In particular, the cultivation of anaerobic electrogenic microbial films at the anode can also be carried out using domestic sewage or organic wastewater instead of the anode culture medium.

[0015] The specific concentrations of each component are (g·L) -1 ): 17.1 Na₂HPO₄·12H₂O, 3.0 KH₂PO₄, 0.3 NaCl, 0.494 MgSO₄·7H₂O, 0.01 CaCl₂, 0.641 CH₃COONa (equivalent to 500 mg·L⁻¹) -1 COD) and 1 mL·L -1 Trace elements, wherein the composition of trace elements is (g·L)-1 ): 1.7 aminotriacetic acid, 1.6 MgSO4·7H2O, 0.37 MnSO4·H2O, 1.50 NaCl, 0.01 CuSO4·5H2O, 0.02 KAl(SO4)2, 0.01 H3BO3, 0.10 FeSO4·7H2O, 0.10 CaCl2·2H2O, 0.10 CoCl2·6H2O, 0.10 ZnSO4·7H2O, 0.01 Na2MoO4.

[0016] During inoculation, the anaerobic sludge and the anolyte are mixed into a homogeneous solution. The mixed anolyte is replaced every three days until the anolyte potential drops to -0.35V±0.05V; the culture is then complete.

[0017] As a further preferred option, the volume ratio of anaerobic sludge to anode culture medium is 1:50.

[0018] Preferably, the cultivation method of the functional flora of iron(II) oxidizing bacteria is as follows: under the temperature conditions of 18-25℃, activated sludge is used as inoculum, and the activated sludge is mixed with fresh 9K medium. The components of 9K medium include FeSO4·7H2O, K2HPO4, (NH4)2SO4, KCl, and MgSO4·7H2O.

[0019] Adjust the pH to 2-3 with sulfuric acid at a concentration of 300 mL / min. -1 Aerate the culture medium in the air for one week until the bacterial solution turns red. Then mix the resulting culture medium with fresh 9K culture medium (volume ratio 1:9) and culture for another 7 days.

[0020] Repeat this step four times (i.e., mix with fresh 9K medium after 7 days of culture), and finally centrifuge to obtain purified functional bacterial groups of iron(II) oxidizing bacteria with Fe(II) conversion rate.

[0021] The obtained Fe(II) oxidizing bacteria functional group was inoculated onto the surface of the BES cathode electrode and operated continuously and stably until the output potential of the BES (bioelectrochemical system) stabilized.

[0022] Preferably, the concentration of Fe(II) in fresh 9K medium is 2.0–3.5 g·L⁻¹. -1 As a further preferred option, the concentration of Fe(II) is 2.5 g·L⁻¹. -1 ;

[0023] The specific concentrations of each component in the 9K medium are given in g·L⁻¹. -1 ): 12.41FeSO4·7H2O [equivalent to 2.5 g·L] -1Fe(II)], 0.1KCl, 0.5K2HPO4, 2.0(NH4)2SO4, 0.5KCl, 0.5MgSO4·7H2O;

[0024] Preferably, the volume ratio of the activated sludge to fresh 9K culture medium is 1:99.

[0025] A method for removing Cr(VI) from water using a bioelectrochemical system, employing the aforementioned apparatus for removing Cr(VI) from water using a bioelectrochemical system, includes the following steps:

[0026] (1) Connect the device and prepare for the work; the anaerobic electrogenic microorganisms attached to the anode grow well and the anode potential drops to -0.35V±0.05V. Fe(II) oxidizing bacteria functional group is inoculated on the cathode surface until the output potential stabilizes.

[0027] (2) After sufficient mature Fe(II) oxidizing bacteria functional biofilm is attached to the surface of the carbon brush electrode of the cathode, Cr(VI)-containing wastewater enters the cathode chamber through the cathode inlet. As the Cr(VI)-containing wastewater is gradually injected, it enters another cathode chamber through the connecting port and connecting pipe. After reaching the water level, it exits through the cathode outlet on the back. The Cr(VI)-containing wastewater achieves continuous inflow and outflow in the cathode chamber.

[0028] (3) After a sufficient mature anaerobic electrogenic microbial film is attached to the surface of the carbon brush electrode of the anode, the injected liquid enters the anode chamber through the anode inlet on the front and exits through the anode outlet on the back to achieve continuous water output.

[0029] (4) The anode is used to generate electrons and energy. The electrons generated by the anode are transported to the two cathodes through the external circuit. At the same time, they can also drive the electrical equipment in the external circuit to use or store electricity, and then diffuse to the two cathode chambers. The protons generated in the anode chamber diffuse to the two cathode chambers through the proton exchange membranes of each cathode chamber. When the voltage drops to 500mV±50mV, the culture medium in the anode chamber is replaced.

[0030] The injected fluid consists of sewage such as domestic sewage and organic wastewater.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The device used in this invention has a three-chamber, double-cathode chamber structure. The inlet and outlet are both set at an angle opposite each other in three dimensions, which allows the wastewater to have more residence time and contact area with the electrodes in the bioelectrochemical treatment system, thus enabling better oxidation-reduction reactions.

[0033] The method of this invention utilizes a functional flora of iron(II) oxidizing bacteria attached to the cathode electrode. This flora exhibits strong resistance to Cr(VI), and its normal physiological activities increase the removal efficiency and rate of Cr(VI). Based on the use of Fe(II) oxidizing bacteria as a biocatalyst for BES cathode to enhance BES power generation, the biomineralization effect of the Fe(II) oxidizing bacteria is used to remove Cr(VI) from the solution through adsorption and co-precipitation. Experimental data demonstrates that the device of this invention can achieve a Cr(VI) removal rate of 99.98% in water. The anode chamber can be injected not only with anode culture medium but also with domestic sewage, organic wastewater, etc., to treat such wastewater.

[0034] The method of this invention can achieve stable power generation and degradation of organic pollutants in the anode solution while removing chromium wastewater at the cathode. Moreover, the products of Cr(VI) degradation at the cathode are safe and environmentally friendly. The entire experimental device does not require an external power source, making it more energy-efficient. Attached Figure Description

[0035] Figure 1 This is a structural diagram of an apparatus for removing Cr(VI) from water using a bioelectrochemical system according to the present invention;

[0036] Figure 2 This is a comparison chart of the degradation rates of Cr(VI) in wastewater between the embodiments and comparative examples of the present invention.

[0037] In the figure, 1-first cathode; 2-anode; 3-second cathode; 4-anode outlet; 5-cathode outlet; 6-cathode inlet; 7-anode inlet; 8, 9-connection port between the two cathodes; 10-external electrical equipment; 11-first cathode chamber; 12-anode chamber; 13-second cathode chamber; 14-connecting pipe. Detailed Implementation

[0038] The accompanying drawings are for illustrative purposes only. To better illustrate this embodiment, some well-known structures and components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. Terms such as "upper," "lower," "left," "right," "front," and "back" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the purpose of facilitating the description of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0039] The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0040] Example 1

[0041] like Figure 1 As shown, a device for removing Cr(VI) from water using a bioelectrochemical system includes a cathode, an anode, a cathode chamber, and an anode chamber. Two cathode chambers are provided: a first cathode chamber 11 and a second cathode chamber 13. An anode chamber 12 is located between the two cathode chambers, and the two sides of the anode chamber 12 are separated from the cathode chamber by proton exchange membranes.

[0042] The first cathode chamber 11 has a cathode inlet 6 at the lower left corner of its front and a connecting port 8 at the lower right corner. The second cathode chamber 13 has a connecting port 9 at the lower left corner of its front and a cathode outlet 5 at the upper right corner of its back. The two connecting ports are connected by a connecting pipe 14. The anode chamber 12 has an anode inlet 7 at the lower left corner of its front and an anode outlet 4 at the upper right corner of its back.

[0043] A vertically downward-facing anode 2 is installed at the top center of the anode chamber 12. An anaerobic electrogenic microbial membrane is attached to the anode 2. A vertically downward-facing cathode (i.e., the first cathode 1 and the second cathode 3) is installed in the center of each cathode chamber. Each cathode is attached with iron(II) oxidizing bacteria functional flora, forming a three-chamber dual-biocathode electrochemical treatment system consisting of the first cathode chamber 11, the anode chamber 12, and the second cathode chamber 13. The first cathode 1 and the anode 2 are connected to an external electrical device 10 via a connecting wire. The two cathodes are connected in series via a connecting wire, so that both cathodes can have electron flow with the anode 2.

[0044] In this embodiment, the electrical device 10 is an energy storage device that can store the electricity generated by the device for use in the operation of other electrical appliances.

[0045] Preferably, the cathode and anode 2 are carbon brush electrodes. The pretreatment method for the carbon brush electrodes before use is as follows: soak them in 0.5M dilute nitric acid, acetone, ethanol, and deionized water for one day respectively, and after each change of the washing solution, ultrasonically vibrate them for 1 hour.

[0046] The top of the anode chamber is sealed. The cultivation method for the anaerobic electrogenic microbial film attached to the carbon brush electrode surface of anode 2 is as follows: Anaerobic sludge from the Qingdao Chengyang District Wastewater Treatment Plant was used as the inoculum for the BES anode at a temperature of 18-25℃. The composition of the anode is (g·L⁻¹). -1 ): 17.1 Na₂HPO₄·12H₂O, 3.0 KH₂PO₄, 0.3 NaCl, 0.494 MgSO₄·7H₂O, 0.01 CaCl₂, 0.641 CH₃COONa (equivalent to 500 mg·L⁻¹) -1 COD) and 1 mL·L -1 Trace elements, wherein the composition of trace elements is (g·L) -1The anolyte composition was: 1.7% aminotriacetic acid, 1.6% MgSO4·7H2O, 0.37% MnSO4·H2O, 1.50% NaCl, 0.01% CuSO4·5H2O, 0.02% KAl(SO4)2, 0.01% H3BO3, 0.10% FeSO4·7H2O, 0.10% CaCl2·2H2O, 0.10% CoCl2·6H2O, 0.10% ZnSO4·7H2O, and 0.01% Na2MoO4. For anode inoculation, a homogeneous solution was prepared by mixing activated sludge and anode culture medium at a volume ratio of 1:50. The mixed anode solution was replaced every 3 days until the anode potential decreased to -0.35V ± 0.05V, indicating that the anode had successfully acclimated electrogenic microorganisms and that the biofilm was growing well.

[0047] The top of each cathode chamber is open, and the cultivation method for a sufficient amount of mature Fe(II) oxidizing bacteria functional microbial biofilm adhering to the carbon brush electrode surface of the cathode is as follows:

[0048] Under temperature conditions of 18-25℃, activated sludge taken from the Chengyang Wastewater Treatment Plant in Qingdao was used as inoculum and inoculated onto the BES cathode. 5.0 g (5.0 ml) of activated sludge was mixed with 495 mL of fresh 9K medium. The composition of the 9K medium was (g·L⁻¹) -1 ): 12.41FeSO4·7H2O [equivalent to 2.5 g·L] -1 The following is a list of ingredients: Fe(II) oxidizing bacteria, 0.1 KCl, 0.5 K₂HPO₄, 2.0 (NH₄)₂SO₄, 0.5 KCl, 0.5 MgSO₄·7H₂O. The process for culturing and purifying the Fe(II) oxidizing bacteria is as follows: The pH was adjusted to 2-3 with sulfuric acid, and the solution was heated at 300 mL / min. -1 Aerate the culture medium in the air for one week until the bacterial solution turns red. Then mix the resulting 50 mL of culture medium with 450 mL of fresh culture medium and incubate for 7 consecutive days.

[0049] This step was repeated four times (i.e., after 7 days of cultivation, the bacteria were mixed with fresh 9K medium and then cultured again). Finally, the bacteria were centrifuged at 4800 rpm for 15 min to obtain purified Fe(II) oxidizing bacteria with a high Fe(II) conversion rate. The obtained Fe(II) oxidizing bacteria were inoculated onto the surface of the BES cathode electrode and continuously and stably operated until the BES output potential stabilized.

[0050] A method for removing Cr(VI) from water using a bioelectrochemical system, employing the aforementioned apparatus for removing Cr(VI) from water using a bioelectrochemical system, includes the following steps:

[0051] (1) Connect the device and prepare for the work; the anaerobic electrogenic microorganisms attached to the anode 2 have good biofilm growth, the potential of the anode 2 drops to -0.35V±0.05V, the Fe(II) oxidizing bacteria functional group is inoculated on the cathode surface until the output potential stabilizes;

[0052] (2) After sufficient mature Fe(II) oxidizing bacteria biofilm is attached to the carbon brush electrode surface of the cathode, 100 mg / L of Cr(VI)-containing wastewater is injected into the first cathode chamber 11. The wastewater enters the first cathode chamber 11 through the cathode inlet 6. As the Cr(VI)-containing wastewater is gradually injected, it enters the second cathode chamber 13 through the connecting ports 8 and 9 and the connecting pipe 14. After reaching the water level, the wastewater exits through the cathode outlet 5 on the back. The Cr(VI)-containing wastewater continuously enters and exits the cathode chamber, thus achieving the degradation of Cr(VI).

[0053] (3) After enough mature anaerobic electrogenic microbial film is attached to the carbon brush electrode surface of anode 2, domestic sewage enters anode chamber 12 through the anode inlet 7 on the front and exits through anode outlet 4 on the back. Domestic sewage can have the maximum contact with the carbon brush electrode of anode 2 to achieve electricity generation and degradation of domestic sewage, and can also continuously enter and exit water.

[0054] (4) The function of anode 2 is to generate electrons and energy. The electrons generated by the anode are transported to the two cathodes through the external circuit. At the same time, they can also drive the power consumption or storage of the power equipment in the external circuit, and then diffuse to the two cathode chambers. The protons generated in the anode chamber diffuse to the two cathode chambers through the proton exchange membranes of each cathode chamber. When the voltage drops to 500mV±50mV, the culture medium in the anode chamber is replaced.

[0055] Mechanism of action:

[0056] For Cr(VI)-containing wastewater, ferrous iron is added at a mass ratio of 2‰±0.5. The purpose of adding ferrous iron is:

[0057] 1) This allows the functional flora of iron-oxidizing bacteria attached to the carbon brush electrode of the cathode to carry out normal physiological metabolic activities.

[0058] 2) Formation of a redox pair with Cr(VI). Cr(VI)-containing wastewater enters the cathode chamber through the cathode inlet 6. Inside the cathode chamber, Cr(VI) in the wastewater is reduced to Cr(III) by electrons transferred from the anode 2 to the cathode electrode via the external circuit. Simultaneously, under the action of the iron-oxidizing bacteria on the surface of the cathode electrode, ferrous iron in the solution is oxidized to ferric iron, forming an Fe(III) / Fe(II) electron mediator pair within the cathode cavity. This electron pair not only increases the electron transfer capacity of the cathode chamber but also undergoes a redox reaction with Cr(VI), promoting the reduction efficiency of Cr(VI). Furthermore, the iron-oxidizing bacteria on the surface of the cathode carbon brush electrode produce potassium ferric sulfate minerals through their physiological metabolism. These minerals have a certain adsorption capacity for Cr(VI), and the potassium ferric sulfate produced by the iron-oxidizing bacteria can also co-precipitate with Cr(VI), mineralizing Cr(VI) into a solid, further improving the removal efficiency and rate of Cr(VI). As the amount of Cr(VI)-containing wastewater gradually increases, it enters the second cathode chamber 13 through the first cathode chamber. The removal of Cr(VI) is further enhanced by the iron-oxidizing bacteria functional group loaded on the carbon brush electrode of the second cathode 3. Finally, the wastewater is discharged from the cathode outlet 5. After the flow treatment of Cr(VI)-containing wastewater through the dual cathode chambers, the Cr(VI) content in the effluent is monitored by the diphenylcarbazide spectrophotometric method, and the final removal rate reaches 99.98%.

[0059] Comparative Example 1

[0060] A standard dual-chamber electrolytic cell was used for degradation, with a cathode chamber on one side and an anode chamber on the other. The cathode used a carbon brush electrode without attached iron-oxidizing bacteria as control group 1. The anode was the same as in Example 1, and 100 mg / L of Cr(VI)-containing wastewater was injected. The Cr(VI) content in the effluent was monitored using diphenylcarbazide spectrophotometry, and the final removal rate is shown in [Figure 1]. Figure 2 As shown.

[0061] Example 2

[0062] Cr(VI)-containing wastewater at a concentration of 120 mg / L was injected into the first cathode chamber 11 for degradation. The final removal rate is shown in the figure. Figure 2 As shown. Other parts not mentioned are the same as in Example 1.

[0063] Comparative Example 2

[0064] Similarly, Cr(VI)-containing wastewater at a concentration of 120 mg / L was injected for degradation, and the final removal rate is shown in the figure. Figure 2 As shown. Other areas not mentioned are the same as in Comparative Example 1.

[0065] Example 3

[0066] Cr(VI)-containing wastewater at a concentration of 50 mg / L was injected into the first cathode chamber 11 for degradation. The final removal rate is shown in the figure. Figure 2 As shown. Other parts not mentioned are the same as in Example 1.

[0067] Comparative Example 3

[0068] Similarly, Cr(VI)-containing wastewater at a concentration of 120 mg / L was injected for degradation, and the final removal rate is shown in the figure. Figure 2 As shown. Other areas not mentioned are the same as in Comparative Example 1.

[0069] like Figure 2 As shown, comparing the results of degradation of Cr(VI)-containing wastewater in Examples 1-3 and Comparative Examples 1-3 of the present invention, it can be seen that the device and method of the present invention achieves a very high removal rate of Cr(VI) in water, exceeding 99%, reaching 99.98%. In contrast, the conventional dual-chamber electrolytic cell setup typically achieves a removal rate of only about 63% to 65% for Cr(VI) in water, representing an improvement in degradation rate of 52.3% to 58.7%.

[0070] In the description of this invention, unless otherwise expressly specified and limited, the terms “installation,” “connection,” and “linking” should be interpreted broadly.

[0071] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for removing Cr(VI) from water using a bioelectrochemical system, comprising a cathode, an anode, a cathode chamber, and an anode chamber, characterized in that, The cathode chamber is provided in two parts, and the anode chamber is provided in the middle of the two cathode chambers. The two sides of the anode chamber are separated from the cathode chamber by proton exchange membranes. One cathode chamber has a cathode inlet at the lower left corner of its front and a connecting port at the lower right corner; the other cathode chamber has a connecting port at the lower left corner of its front and a cathode outlet at the upper right corner of its back, and the two connecting ports are connected by a connecting pipe; the anode chamber has an anode inlet at the lower left corner of its front and an anode outlet at the upper right corner of its back. A vertically downward anode is installed at the top center of the anode chamber, and an anaerobic electrogenic microbial membrane is attached to the anode. A vertically downward cathode is installed in the center of each cathode chamber, and an iron(II) oxidizing bacteria functional flora is attached to each cathode, forming a three-chamber dual-biocathode electrochemical treatment system consisting of a cathode chamber, an anode chamber, and a cathode chamber. One cathode is connected to an external electrical device via a connecting line, and the two cathodes are connected by a connecting line. The cathode and anode are respectively equipped with carbon brush electrodes; The top of the anode chamber is sealed, while the top of each cathode chamber is open. The method for culturing the functional flora of iron-oxidizing bacteria is as follows: under the temperature conditions of 18-25°C, activated sludge is used as inoculum, and the activated sludge is mixed with fresh 9K medium. The components of 9K medium include FeSO4·7H2O, K2HPO4, (NH4)2SO4, KCl, and MgSO4·7H2O. Adjust the pH to 2-3 using sulfuric acid, at a concentration of 300 mL / min. -1 Aerate the bacterial culture in the air for one week until the bacterial solution turns red. Then mix the resulting culture medium with fresh 9K culture medium and culture continuously for 7 days. Repeat this step four times. Finally, centrifuge to obtain purified functional bacterial groups of iron(II) oxidizing bacteria with Fe(II) conversion rate. The obtained Fe(II) oxidizing bacteria functional group was inoculated onto the surface of the BES cathode electrode and continuously and stably operated until the output potential stabilized. The method includes the following steps: (1) Connect the device and prepare the work; the anaerobic electrogenic microbial film attached to the anode grows well, the anode potential drops to -0.35V ± 0.05V, the cathode surface is inoculated with Fe(II) oxidizing bacteria functional group until the output potential stabilizes; (2) After sufficient mature Fe(II) oxidizing bacteria functional biofilm is attached to the carbon brush electrode surface of the cathode, Cr(VI)-containing wastewater enters the cathode chamber through the cathode inlet. As the Cr(VI)-containing wastewater is gradually injected, it enters another cathode chamber through the connecting port and connecting pipe. After reaching the water level, it exits through the cathode outlet on the back. The Cr(VI)-containing wastewater achieves continuous inflow and outflow in the cathode chamber. (3) After a sufficient amount of mature anaerobic electrogenic microbial film is attached to the surface of the carbon brush electrode of the anode, the injected liquid enters the anode chamber through the anode inlet on the front side and exits through the anode outlet on the back side to achieve continuous water output. (4) The anode is used to generate electrons and energy. The electrons generated by the anode are transported to the two cathodes through the external circuit. At the same time, they can also drive the power-consuming equipment in the external circuit to consume or store electricity, and then diffuse to the two cathode chambers. The protons generated in the anode chamber diffuse to the two cathode chambers through the proton exchange membranes of each cathode chamber. When the voltage drops to 500mV±50mV, the culture medium in the anode chamber is replaced.

2. The method for removing Cr(VI) from water using a bioelectrochemical system according to claim 1, characterized in that, The pretreatment method for the carbon brush electrode before use is as follows: soak it in 0.5M dilute nitric acid, acetone, ethanol and deionized water respectively, and then ultrasonically vibrate it after each change of the cleaning solution.

3. The method for removing Cr(VI) from water using a bioelectrochemical system according to claim 1, characterized in that, The cultivation method of anodic anaerobic electrogenic microbial film is as follows: anaerobic sludge is used as the anode inoculum and cultured with an anode culture medium. The anode culture medium includes Na2HPO4·12H2O, KH2PO4, NaCl, MgSO4·7H2O, CaCl2, CH3COONa, and trace elements, among which the trace elements include aminotriacetic acid, MgSO4·7H2O, MnSO4·H2O, NaCl, CuSO4·5H2O, KAl(SO4)2, H3BO3, FeSO4·7H2O, CaCl2·2H2O, CoCl2·6H2O, ZnSO4·7H2O, and Na2MoO4. During inoculation, the anaerobic sludge and the anolyte are mixed into a homogeneous solution. The mixed anolyte is replaced periodically until the anolyte potential drops to -0.35V ± 0.05V; the culture is then complete.

4. The method for removing Cr(VI) from water using a bioelectrochemical system according to claim 1, characterized in that, The volume ratio of anaerobic sludge to anode culture medium is 1:

50.

5. The method for removing Cr(VI) from water using a bioelectrochemical system according to claim 1, characterized in that, In fresh 9K medium, the concentration of Fe(II) was 2.0–3.5 g•L. -1 .

6. The method for removing Cr(VI) from water using a bioelectrochemical system according to claim 1, characterized in that, The volume ratio of the activated sludge to fresh 9K culture medium is 1:99.

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