Effects of cod:sulfate ratio on sulfate removal from oil shale retort water using microbial fuel cells

Abstract

This paper reports the effects of COD:sulfate ratio on sulfate removal and electricity generation from oil shale retort water treatment using microbial fuel cells (MFCs). Field-collected retort water was augmented with organics to obtain a range of initial COD:SO42- ratios (0.5:1 to 2:1), and treated in two different MFC designs (tubular and two-chambered). The two-chambered MFCs exhibited COD and sulfate removal 1 to 2 orders of magnitude higher than those of the tubular MFCs. The tubular MFCs did not exhibit a significant dependence of sulfate removal on the COD:SO42- ratio while the two-chambered MFCs showed a positive trend. The tubular MFCs generated a maximum power density of 19 mW/m2 (COD:SO42-= 1.5:1), and the two-chambered MFCs produced 120 mW/m2 (2:1). The results suggest that organic carbon loading to the MFCs should be determined based on the sulfate concentration and reactor design to achieve optimal sulfate removal and electric power output.