Microbial Electrochemical Coupling System For Wastewater Treatment And Contaminants Detection

Since the 1990s,the industrialization process has achieved rapid development,which was brought environmental pollution,especially the unreasonable and substandard discharge of industrial wastewater.It poses a serious threat to the animals,human beings and the entire ecosystem.Traditional physical and chemical methods can achieve the removal and detection of pollutants in industrial wastewater,but they often require the sophisticated instruments and professional technicians.The high cost of investment and the inability to achieve in situ detection limit its practical applications.Therefore,it is critical to explore a promising wastewater treatment and detection technology to control the environmental pollution.In recent years,Microbial Electrochemical System（MES）as a new environmental-friendly technology that can simultaneously achieve energy recovery and pollutant removal has increased more attention in wastewater treatment,new energy development,and biosensors.However,the traditional MES exhibits some shortages such as decline in power generation and operating energy consumption when treating actual industrial wastewater with complex components,which limits its practical application in actual wastewater treatment.Therefore,in this study,improvements have been made in electrode materials and system configuration,etc.MES was integrated with immobilization technology,membrane bioreactor,Fenton reaction,and other high-efficiency wastewater treatment processes to form a microbial electrochemical coupling system for improving the wastewater treatment efficiency and reducing system operation energy input.The research results and conclusions of each treatment as follows:（1）A biocathode Microbial Fuel Cell（MFC）system was developed to reduce hexavalent chromium（Cr（VI））for the electroplating wastewater treatment.The traditional biocathode system mainly uses electrode reversal or chemical method for electrode modification,which is complex and high-cost.In this system,the isolated strain Corynebacterium vitaeruminis LZU47-1 was immobilized on the cathode carbon felt electrode to form the dense biofilm for acting as the biocathode to enhance Cr（VI）reduction.The operation parameters are optimized to improve both the treatment efficiency and power output.A real electroplating wastewater containing 40mg L^-1 Cr（VI）was treated in this system under the optimized condition（p H=5）.After48 h operation,98.63%Cr（VI）was removed.Electrical power recovery and Cr（VI）reduction were achieved simultaneously.The maximum power density was 252.36m W m^-2 in this system.Scanning electron microscopy and X-ray photoelectron spectroscopy（XPS）analysis of the deposion on the cathode surface showed Cr（VI）was removed in the form of Cr₂O₃.（2）Based on the low efficiency and high energy consumption of a single MFC in the actual petrochemical wastewater treatment,a two-stage MFC and membrane bioreactor（MBR）couple system was developed.Different from the conventional two-stage MFC-MBR coupled wastewater treatment system,in this system,MFC not only acts as a wastewater treatment unit,but also acts as a biosensor to control the steps of the two-stage system,optimizes the process,enhances the petrochemical wastewater treatment,reduces the MBR membrane pollution,and reduces the energy consumption of the system.Compared with the traditional two-stage MFC-MBR system,the removal efficiency of parameters like chemical oxygen demand（COD）and total nitrogen（TN）in this system is increased by about 20%.The transmembrane pressure of MBR was reduced 50%,and the energy recovery of the system was increased 5 times.（3）Sediment Microbial Fuel Cell（SMFC）is a single-chamber configuration that is different from traditional MFC,which can only process a single liquid phase.SMFC can simultaneously achieve the solid and liquid phase removal of pollutants.Therefore,we developed a SMFC driven cathodic electro-Fenton reaction system for the simultaneous removal of non-steroidal anti-inflammatory drugs in water and sludge.The low removal efficiency of a single SMFC and the high energy consumption of the electro-Fenton reaction were overcome.In this system,the anode is activated sludge for the biodegradation and biosorption of the pollutants,and the cathode is the Fe-Mn doped biochar gas diffusion electrode to perform electro-Fenton reaction for the removal of the pollutants in the water phase.Scanning electron microscopy couple with X-ray photoelectron spectroscopy confirmed the functional cathode was formed.The concentrations of hydrogen peroxide and hydroxyl radicals were 3.5 mg L^-1 and 2 mg L^-1,respectively,indicating that the electric Fenton reaction occurred.The total removal efficiency of ibuprofen,naproxen and diclofenac was99.1%,98.5%and 80.6%,respectively.（4）SMFC as a special configuration of MFC,which has similar functions to MFC.It can not only used for wastewater treatment,but the generated current can also work as a biosensor signal to detect the concentration of pollutants.Compared with MFC,SMFC is more suitable for actual production due to its special structure.A Cr（VI）biosensor based on SMFC has been developed according to the MFC cathode can reduce Cr（VI）.In this system,Cr（VI）in the cathode is used as sensing element to receive electrons for current generation and the concentration of Cr（VI）affects the magnitude of the electric current.Under the optimal conditions of p H=6.4 and temperature of 25℃,a good linear relationship（R²=0.9935）was observed between the Cr（VI）concentration in the range of 0.2-0.7 mg L^-1 with the generated current.Furthermore,the system exhibits extremely high stability,accuracy and sensitivity in actual wastewater detection,which provides a feasible method for in situ and real-time monitoring of Cr（VI）in industrial wastewater.In this study,we reformed the electrode materials and reactor configuration of the traditional MES system,combined with some technical such as synthetic biology and advanced oxidation processes to forme a microbial electrochemical coupling system.The coupling sysytem enhanced the efficiency of the wastewater treatment,increased the power generation of the MES system and improved the detection accuracy of the biosensor based on the MES system,which was better realize the resource and energy treatment of wastewater.