Simultaneous power generation and pollutant removals using microbial desalination cell at variable operation modes

Abstract

The performance of microbial desalination cells was investigated concurrently under different substrate strengths and variable external resistances. When the external resistance was fixed at 1,000 Ω, the maximum voltage was 710, 694 and 650 mV at substrate COD concentrations of 500, 1500 and 3000 mg/l respectively. The average COD removal efficiencies were 90.0 ± 5.2, 92.3 ± 4.3 and 53.4 ± 7.2% at substrate concentrations of 500, 1500 and 3000 mg/l respectively. The cell operated at high substrate strength achieved the lowest voltage generation and highest internal resistance. Columbic Efficiencies (CEs) increased with decreased COD loading rates. The cell operated at medium substrate strength achieved the best desalination efficiency due to substrate availability and the lowermost internal resistance. Further investigation was made at different external resistances of 10 to 10,000 Ω which were found to have a significant effect on COD removal and CEs. The high desalination efficiencies were accompanied by higher current densities. Scanning Electron Microscopy (SEM) analyses were conducted for the anode electrode to investigate the biofilm morphology. This study demonstrated interesting results regarding the operation modes that could contribute to the microbial desalination cells scale up.