Transitioning from batch to flow hypersaline microbial fuel cells

Application of electro-active halotolerant bacteria in bioelectrochemical systems opens for the sustainable on line monitoring of saline wastewater treatment; however, this approach has been investigated only in lab-scale devices, mostly in batch configuration. The field application of the technology introduces several parameters that can influence bioelectrochemical and degradation performance. Herein, we report the detailed study of how continuous flow operation (3 ± 1 mL min−1) affects the bioelectrochemical performance of a flow hypersaline microbial fuel cell. Flow operation resulted in a 70% decrease of power density (passing from 2.1 ± 0.1 to 0.67 ± 0.01 mW m−2), where the washout of endogenous redox mediator played a critical role. Engineering of bacteria entrapment techniques mitigated the inhibitory effects of continuous flow, ensuring successful extracellular electron transfer. Specifically, bacteria entrapment in composite alginate capsules with activated carbon to enhance their conductivity was investigated, and the effects of different activated carbon loads are presented. A maximum power density comparable to batch operation was achieved for composite capsules with 0.15 gL-1 activated carbon (1.8 ± 0.9 mW m−2), as well as the possible correlation of electrochemical and COD removal performance, enabling future development of self-powered hypersaline flow microbial biosensor for contaminants monitoring.