Optimization of nitrate and selenate reduction in an ethanol-fed fluidized bed reactor via redox potential feedback control

Electron donors are a major cost-factor in biological removal of oxyanions, such as nitrate and selenate from wastewater. In this study, an online ethanol dosing strategy based on feedback control oxidation-reduction potential (ORP) was designed to optimize the performance lab-scale fluidized bed reactor (FBR) treating (5 mM each) containing The FBR evaluated at various ORP setpoints ranging between ?520 mV ?240 (vs. Ag/AgCl). Results suggested that both were completely removed ORPs ?360 mV, with methylseleninic acid, selenocyanate, selenosulfate ammonia being produced low ?480 likely due overdosing ethanol. At ?300 limited resulted apparent decline whereas remained stable. Resuming successfully restored complete reduction. An optimal ?400 identified for FBR, whereby nearly minimal consumption. Overall, controlling via feedback-dosing electron donor effective reducing