Effect of external resistance on microbial electrochemical desalination, sewage treatment, power and resource recovery

Microbial desalination cell (MDC) has attracted attention as an eco-friendly technology to treat sewage and seawater with concurrent recovery of bioelectricity. External resistance (R-ext) is one of the main factors that control it's performances. This study optimized the performance of an MDC for removing COD and salinity at five different R-ext of 150, 100, 50, 25, and 10 Omega. Columbic efficiency (CE) was measured to find the best R-ext for MDC operation. Voltage polarization demonstrated that the MDC possessed an internal resistance (R-int) of 25-30 Omega and maximum power recovery of 302.25 mW/m(2). The highest and lowest recovery of stable electricity was 20.7 mA and 3.6 mA at R-ext of 10 and 150 Omega, respectively. The COD removal increased from 21% at R-ext of 25 Omega to 57% at R-ext of 150 Omega . The CE decreased from 58.3% to 4.32% with the gradual increase of R-ext from 25 to 150 Omega suggesting the dominancy of exoelectrogens in biofilm at R-ext <= R-int. The achieved desalination rate was 47% and 18% at R-ext of 10 and 25 Omega, respectively. The performances of investigated MDC showed a great potential for recovering electricity with significant removal of organics from domestic sewage and salt from seawater.

Automated summary

Microbial desalination cell (MDC) is an eco-friendly technology for treating sewage and seawater with bioelectricity recovery. This study optimized MDC performance by varying the external resistance (R-ext), achieving efficient removal of COD and salinity.