Effects of Chloride Ion on Performance and Microbial Community in an Anaerobic Fluidized Bed Microbial Fuel Cell

Saltwater is detrimental to biological wastewater treatment processes. Anaerobic reduction is a promising technology for treating complex organic wastewater but is limited by relatively long reaction times and high demand for electron donors. In microbial fuel cells (MFCs), the salinity contained in saltwater promotes the redox reaction between the electrodes to accelerate the removal of chemical oxygen demand (COD) and generate electricity. In this study, a system combining an anaerobic fluidized bed (AFB) with an MFC was constructed to treat high-salinity wastewater. As a result, the anode attained good removal efficiency of 98.6% for COD and 52.1% for NH4+-N when the Cl- concentration was <6500 mg/L. Electricity generation was maintained when the Cl-concentration was similar to 12,000 mg/L; a maximum output of 841.3 mV and 35.4 mW/m(2) was achieved. Investigation of the biological characteristics confirmed that the high biomass in the AFB ensured good contaminant removal efficiency. Furthermore, the ratio of proteins to polysaccharides in extracellular polymeric substances decreased sharply at a Cl(-)concentration of 6500 mg/L. Genomic sequencing analysis of anode bioparticles showed that Halanaerobiaceae bacterium sp. and Methanolinea tarda sp. were predominant in the bacterial and archaeal communities, respectively. This study suggested that the AFB-MFC system has good potential for contaminants removal and electricity generation in treatment of high-salinity wastewater.