Stacked Bioelectrochemcal Systems For Enhancing Power Generation And Organic Pollutant Transformation And Degradation

Bioelectrochemical system(BES)is a kind of newly developed wastewater treatment and energy recovery technology that could in-situ transfer chemical energy of organic pollutant into electricity while simultaneously treating wastewater.However,the insufficient power generation and wastewater treatment performance of traditional BES has limited its practical applicationj.In this doctoral dissertation,granular activated carbon(GAC)packed bed electrode and the composite electrode which combined carbon brush with carbon mesh were studied and compared to select out more effective electrode configuration.By employing the preferred electrode,a novel scaled-up stacked BES reactor was constructed to treat simulated domestic wastewater,and a novel three-electrode-chamber stacked BES reactor was designed and constructed to treat nitrobenzen-involved organic wastewater.On the basis of these researches,the improvemnt of power generation and organic pollutant degradation in BES was achieved.The adsorptive effect of GAC packed bed anode on power production was studied.The result demonstated that the adsorptive effect of GAC helped to reduce mass transfer resistance of anode while treating low concentration wastewater and thus enhancing power production of BES.On the other hand,the composite anode had higher electrochemical activity and power density than the traditional carbon brush or carbon mesh anode.The carbon mesh in the composite anode helped to reduce oxgygen contamination to the anode and thus improve the coulombic efficiency and stability of power production in BES.After comprehensively compared the performance of GAC packed bed anode with the composite anode,GAC packed bed electrode was more preferable for BES practical application due to its higher power generation performance(612 mW/m~2)and lower material cost(?3.6-10/kg).By employing GAC packed bed electrode,a novel stacked BES(SBES)reactor with a total volume of 72 L was constructed to treat simulated domestic wastewater.The maximum power density and COD removal loading rate were respectively 42.1 W/m~3and5.2 kg COD/(m~3 d),which exceeded the performance of most scaled-up BES reactors with the similar dimension.Current reversal phenonmena was discovered in the parallel circuit connection of SBES and the mechanism of its occurrence when applying larger external resistance(>100?)was unveiled.The long-term existence of reversal current would reduce the electrochemical performance of some BES modules in the stack,leading to a lower power density of SBES in parallel circuit connection(50.3 W/m~3)than the individual circuit connection(59.2 W/m~3).A novel three electrode stacked BES reactor was developed to treat the nitrobenzen-involved organic wastewater.The wastewater was pumped into the anaerobic biocathode,anode and aerobic biocathode in sequence in stacked BES.The total nitrobenzene and COD removal efficiencies of stacked BES achieved 82%and 81%respectively,both of which were higher than the removal efficiencies of traditional dual-chamber BES(61%and 58%).At the same time,the transient circuit control was applied to effectivley enhance the electrochemical performance of stacked BES and thus improve the reductive transformation efficiency of nitrobenzen(84%)in the anaerobic biocathode.The total nitrobenzene and COD removal efficiencies of stacked BES at transient circuit connection concequently increased to 92%and 87%,which achieved effective mineralization removal of nitrobenzen and other organic pollutants in the wastewater.