Conductive material-loaded bio-electrochemical system device for removing trichloroethylene contaminant, and method

Abstract

The present invention belongs to the technical field of wastewater treatment. Disclosed are a conductive material-loaded bio-electrochemical system device for removing a trichloroethylene contaminant, and a method. Wastewater to be treated containing trichloroethylene is introduced into a bio-electrochemical system device inoculated with a dechlorination mixed microbiota; microorganisms colonize the surface of a cathode carbon brush to form an electroactive dechlorinating biofilm; electrons flow through an external circuit to a cathode so as to be used by the microorganisms; nano-magnetite and activated carbon enhance the reductive dechlorination of trichloroethylene by enhancing electron transfer. The present invention can completely convert trichloroethylene to ethylene and completely reduce 500 μM of trichloroethylene within 12-15 days, couples electrochemical technology with microbial dechlorination technology, and has the advantages of low cost, environmental friendliness and in-situ repairability.

Description

A bioelectrochemical system and method for removing trichloroethylene contamination using a conductive material-loaded biochemical system. Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a bioelectrochemical system device and treatment method for removing trichloroethylene pollution by loading conductive materials. Background Technology

[0002] Trichloroethylene is a typical halogenated pollutant widely used in industrial solvents, degreasers, paint removers, detergents, and pesticides. Due to improper disposal and management, trichloroethylene has become one of the most frequently detected organic pollutants in groundwater. Trichloroethylene is persistent and bioaccumulative, accumulating in organisms along the food chain and causing serious impacts on the entire ecosystem. It has been listed as a key pollutant by the U.S. Environmental Protection Agency, the European Union, and the Ministry of Ecology and Environment of China, and is subject to strict regulation.

[0003] Currently, the remediation of chlorinated hydrocarbon contaminated sites using traditional physicochemical treatment techniques suffers from drawbacks such as high treatment costs, limited treatment scope, and secondary pollution. Utilizing bioelectrochemical systems to enhance microbial reduction dechlorination is considered a promising approach. Bioelectrochemical systems can directly or indirectly provide electron donors for the bioreduction dechlorination process. However, the efficiency of extracellular electron transfer remains a key limiting factor in the application of bioelectrochemical systems for reduction dechlorination, and the dechlorination rate enhanced solely by bioelectrochemical systems remains limited.

[0004] Conductive materials, acting as electron transport channels, have been shown to significantly enhance electron transport in BES (Biosorbent Electrolyte Reduction). Conductive materials mainly include iron-based materials (such as biochar, activated carbon, and graphite) and carbon-based materials (such as magnetite, hydrated iron, and zero-valent iron). Magnetite is widely distributed in nature and possesses high conductivity. Magnetite can enhance electron transport in a manner similar to cytochrome OmcS, thereby reducing electron flow resistance. Simultaneously, magnetite can break the constraint that cells require close contact for direct electron transport, allowing more energy to be used for cell growth. Biochar is another common conductive material, offering advantages such as easy availability and low cost. The porous structure and high specific surface area of ​​biochar facilitate microbial colonization on its surface. Biochar can also function as conductive fimbriae and polyhemoglobin c, potentially playing an important role in electron transport. However, the effectiveness of conductive materials in enhancing the reductive dechlorination process in BES remains to be elucidated.

[0005] Summary of the Invention

[0006] The purpose of this invention is to explore the application potential of conductive materials, such as nano-magnetite and biochar, in the removal of trichloroethylene in bioelectrochemical systems, and to provide a stable and efficient reaction device and method for removing trichloroethylene.

[0007] The inventive concept of this invention is to construct a bioelectrochemical system device with added conductive materials to completely reduce trichloroethylene to ethylene. Compared with a simple bioelectrochemical system device, this promotes extracellular electron transfer and increases the dechlorination rate.

[0008] The specific technical solution adopted in this invention is as follows:

[0009] In a first aspect, the present invention provides a bioelectrochemical system device for efficiently removing trichloroethylene by loading conductive materials. This bioelectrochemical system device for removing trichloroethylene pollution includes an electrically connected potentiometer and a bioelectrochemical system reactor loaded with conductive materials. Conductive materials are dispersed on the cathode surface of the reactor. Electroactive microorganisms and dechlorinating microorganisms are enriched in the reactor, forming an electroactive dechlorinating biofilm on the cathode surface. The dechlorinating bacteria use the cathode as an electron donor to completely reduce trichloroethylene in wastewater to environmentally harmless ethylene. The conductive materials enhance the reduction of trichloroethylene by microorganisms by increasing electron transfer.

[0010] As a preferred embodiment of the first aspect, the bioelectrochemical system device loaded with conductive material adopts a unipolar chamber structure, wherein a carbon brush is provided as a working electrode and a counter electrode, and a silver / silver chloride electrode is provided as a reference electrode. Microorganisms colonize the surface of the cathode carbon brush, and electrons flow to the cathode through an external circuit for use by the microorganisms.

[0011] As a preferred embodiment of the first aspect above, the conductive material is nano-magnetite or biochar or a mixture of both.

[0012] As a preferred embodiment of the first aspect above, the conductive material is uniformly dispersed on the surface of the cathode carbon brush at a concentration of 0.5 g / L.

[0013] Secondly, the present invention provides a wastewater treatment method utilizing the bioelectrochemical system device with a loaded conductive material as described in the first aspect, as follows:

[0014] Wastewater containing trichloroethylene is fed into the aforementioned bioelectrochemical system, where an electroactive dechlorination biofilm is formed on the cathode surface. Nano-magnetite and activated carbon enhance the reductive dechlorination of trichloroethylene by increasing electron transfer.

[0015] As a preferred embodiment of the second aspect above, the concentration of trichloroethylene in the wastewater is 500±50μM.

[0016] As a preferred embodiment of the second aspect above, the dissolved oxygen concentration of the wastewater in the bioelectrochemical system device loaded with conductive material is controlled to be below 0.2 mg / L.

[0017] As a preferred embodiment of the second aspect above, in the bioelectrochemical system device loaded with conductive material, the cathode potential is set to -0.30V (vs SHE), and the temperature is controlled at 28–30°C.

[0018] This invention introduces a bioelectrochemical system device containing trichloroethylene into a mixture of dechlorination bacteria. Microorganisms colonize the surface of the cathode carbon brush, forming an electroactive dechlorination biofilm. Electrons flow through the external circuit to the cathode for use by the microorganisms. Nano-magnetite and activated carbon enhance the reduction and dechlorination of trichloroethylene by increasing electron transfer.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) This invention utilizes conductive materials to enhance the reduction and dechlorination of the bioelectrochemical system, which can completely convert trichloroethylene into ethylene, thereby improving the dechlorination rate and completely reducing 500μM trichloroethylene within 12 to 15 days.

[0021] (3) This invention combines electrochemical technology and microbial dechlorination technology, and has the advantages of low cost, environmental friendliness and in-situ remediation. Attached Figure Description

[0022] Figure 1 shows a bioelectrochemical system device for removing trichloroethylene contamination using a loaded conductive material, provided by the present invention.

[0023] Wherein: 1-potentiometer, 2-Teflon-coated butyl rubber stopper, 2-aluminum cap, 3-carbon brush cathode, 4-conductive material, 5-silver / silver chloride reference electrode, 6-carbon brush anode

[0024] Figure 2 shows the operating effect of a bioelectrochemical system device for removing trichloroethylene pollution from an unmodified state, as described in the comparative example of this invention.

[0025] Figure 3 is a diagram showing the operational effect of a bioelectrochemical system device for removing trichloroethylene contamination using loaded nano-magnetite in an embodiment of the present invention.

[0026] Figure 4 is a diagram showing the operating effect of a bioelectrochemical system device for removing trichloroethylene pollution using loaded biochar in an embodiment of the present invention.

[0027] Figure 5 shows the cathode biofilm microbial community composition (at the genus level) of the unmodified and conductive-loaded bioelectrochemical system device used to remove trichloroethylene contamination in an embodiment of the present invention during the reduction dechlorination process. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Technical features in the various embodiments of the present invention can be combined accordingly without mutual conflict.

[0029] Figure 1 shows a bioelectrochemical system device for removing trichloroethylene pollution using a conductive material-loaded reactor, provided by this invention. The device mainly comprises a potentiometer and a bioelectrochemical system reactor loaded with the conductive material. The bioelectrochemical system reactor is the core of the entire treatment device. The device adopts a single-chamber structure, with sampling ports on the reactor shell. The upper sampling port is used to collect headspace gas to monitor the concentration of trichloroethylene and low-chlorine intermediates during the reduction dechlorination process, while the lower sampling port is used to collect water samples. The device is connected to the potentiometer to control the cathode potential. Carbon brushes are used as the cathode and anode, respectively, and a silver / silver chloride electrode serves as the reference electrode. Nano-magnetite or biochar is uniformly dispersed on the cathode surface, and the device is sealed with an aluminum cap and a Teflon-coated butyl rubber stopper.

[0030] In this embodiment, the wastewater to be treated used to implement the method of the present invention has the following components: 1.0 g / L NaCl; 0.2 g / L KH2PO4; 0.3 g / L NH4Cl; 0.3 g / L KCl; 0.015 g / L CaCl2·2H2O; 0.06 g / L MgCl2·6H2O; 1.87 g / L sodium lactate; 0.035 g / L L-cysteine ​​sulfate; 0.048 g / L Na2S·9H2O; 2.383 g / L HEPES; 0.84 g / L NaHCO3, and the trace element composition is as follows: 1.5 mg / L FeCl2·4H2O; 0.19 mg / L CoCl2·6H2O; 0.1 mg / L MnCl2·4H2O; 0.07 mg / L ZnCl2; 0.036 mg / L The concentrations of trichloroethylene in the wastewater were: Na₂MoO₄·2H₂O (0.024 mg / L), NiCl₂·6H₂O (0.002 mg / L), CuCl₂·2H₂O (0.006 mg / L), Na₂SeO₃·5H₂O (0.008 mg / L), and Na₂WO₄·2H₂O (0.008 mg / L). The concentration of trichloroethylene in the wastewater was approximately 500 μM. The concentrations of trichloroethylene and low-chlorinated intermediates were determined by gas chromatography.

[0031] The reductive dechlorinating bacteria used in this invention were initially enriched in sediments of the Three Gorges Reservoir in the Yangtze River. They were cultured in the dark under anaerobic conditions at 30°C and continuously passaged using trichloroethylene and sodium lactate as electron acceptors and electron donors, respectively. The anaerobic culture medium consisted of 1.0 g / L NaCl; 0.2 g / L KH₂PO₄; 0.3 g / L NH₄Cl; 0.3 g / L KCl; 0.015 g / L CaCl₂·2H₂O; 0.06 g / L MgCl₂·6H₂O; 1.87 g / L sodium lactate; 0.035 g / L L-cysteine ​​sulfate; 0.048 g / L Na₂S·9H₂O; 2.383 g / L HEPES; 0.84 g / L NaHCO₃, and trace elements: 1.5 mg / L FeCl₂·4H₂O; 0.19 mg / L CoCl₂·6H₂O; 0.1 mg / L MnCl₂·4H₂O; 0.07 mg / L ZnCl₂; 0.036 mg / L... The culture medium consisted of Na₂MoO₄·2H₂O (0.024 mg / L), NiCl₂·6H₂O (0.002 mg / L), CuCl₂·2H₂O (0.006 mg / L), Na₂SeO₃·5H₂O (0.008 mg / L), and Na₂WO₄·2H₂O (0.008 mg / L). The medium was deoxygenated by boiling and aerating with nitrogen for 15 minutes. 10 mL of bacterial culture was inoculated into every 90 mL of medium.

[0032] It should be noted that the reductive dechlorinating bacteria utilized in this invention are microorganisms widely found in nature and capable of reducing organohalides. This invention does not limit the specific species or flora; such reductive dechlorinating bacteria can be obtained through laboratory domestication and enrichment, or from anaerobic microbial communities in an environment containing organohalides, and there are no restrictions on this. The main microorganisms include Pseudomonas, Geobacter, and Desulfovibrio.

[0033] The comparative example is the unmodified bioelectrochemical system device, and the operating effect diagram is shown in Figure 2.

[0034] Example 1: A bioelectrochemical system device loaded with nano-magnetite, the operation effect is shown in Figure 3.

[0035] Example 2 is a bioelectrochemical system device loaded with biochar, and the operation effect diagram is shown in Figure 2.

[0036] In Examples 1 and 2, the conductive materials nano-magnetite and activated carbon are uniformly dispersed on the surface of the cathode carbon brush at a concentration of 0.5 g / L, forming an electroactive dechlorination biofilm on the cathode surface. The nano-magnetite and biochar enhance the microbial reduction of trichloroethylene by enhancing electron transfer.

[0037] For comparison with Figures 2-4, the conductive material significantly improved the dechlorination rate of the bioelectrochemical system, especially in Period 2 and Period 3 (31-55 days and 56-74 days, respectively). The average dechlorination rate of the bioelectrochemical system loaded with nano-magnetite and biochar in the examples was significantly higher (p<0.05) than that of the unmodified bioelectrochemical system in the comparative example, by 1.57 and 1.32 times, respectively.

[0038] Furthermore, the microbial community structure of the cathode biofilms in the comparative examples and Examples 1 and 2 was analyzed, and the results are shown in Figure 5. Compared with the unmodified bioelectrochemical system in the comparative examples, the relative abundance of electroactive microorganisms and organohalogenated respiratory bacteria on the cathode biofilm of the bioelectrochemical system loaded with nano-magnetite or biochar was increased. The electroactive microorganism *Pseudomonas* was the main electroactive microorganism, capable of directly taking up electrons from the cathode. *Geobacter* and *Desulfovibrio* were capable of direct extracellular electron transfer and were major contributors to dechlorination.

[0039] The processing method and operating conditions in this comparative example are the same as in the embodiment, the only difference being that the reactor cathode is not loaded with conductive material. This comparative example aims to demonstrate that loading conductive material onto the cathode can improve the reductive dechlorination rate.

[0040] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A bioelectrochemical system device for removing trichloroethylene pollution by loading conductive material, comprising an electrically connected potentiometer and a bioelectrochemical system reactor loaded with conductive material, wherein conductive material is dispersed on the cathode surface of the reactor, electroactive microorganisms and dechlorination microorganisms are enriched in the reactor, an electroactive dechlorination biofilm is formed on the cathode surface, the dechlorination bacteria use the cathode as an electron donor to completely reduce trichloroethylene in wastewater to environmentally harmless ethylene, and the conductive material enhances the microbial reduction of trichloroethylene by enhancing electron transfer.

2. The device of claim 1, wherein: The conductive material is nano-magnetite or biochar or a mixture of both.

3. The bioelectrochemical system device of claim 1, wherein: The reactor adopts a single-chamber structure, with carbon brushes as the cathode and anode, and a silver / silver chloride electrode as the reference electrode. Nano-magnetite or biochar is uniformly dispersed on the cathode surface, and microorganisms colonize on the cathode carbon brush surface. Electrons flow to the cathode through an external circuit for use by the microorganisms.

4. The bioelectrochemical system device of claim 2, wherein, The conductive material is uniformly dispersed on the surface of the cathode carbon brush, and the concentration of the conductive material is 0.5 g / L.

5. The bioelectrochemical system device of claim 1, wherein: The cathode potential is set to -0.30V (vsSHE), and the temperature is controlled at 28-30℃.

6. A sewage treatment method using the bioelectrochemical system device for removing trichloroethylene pollution according to any one of claims 1 to 5, characterized by, Specifically, the wastewater containing trichloroethylene is passed into a bioelectrochemical system device loaded with conductive material and inoculated with a mixed dechlorination microbial community. Electroactive microorganisms and dechlorination microorganisms are enriched to form an electroactive dechlorination biofilm on the cathode surface. Using the cathode as an electron donor, trichloroethylene is completely dechlorinated into ethylene, thus achieving wastewater treatment.

7. The wastewater treatment method according to claim 5, characterized in that, The concentration of trichloroethylene in the wastewater to be treated is 500±50μM.

8. The wastewater treatment method according to claim 5, characterized in that, The dissolved oxygen concentration of the wastewater to be treated is controlled to be below 0.2 mg / L.

9. The wastewater treatment method according to claim 5, characterized in that, The cathode potential is set to -0.30V (vs SHE), and the temperature is controlled at 28-30℃.

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