Anaerobic treatment of phenol by an expanded-bed reactor

An expected-bed anaerobic reactor using granular activated carbon as the biological attachment medium was operated continuously on a synthetically prepared phenol solution containing salts and vitamins for 588 days. Four steady-state operating conditions were obtained with the anaerobic reactor. The empty-bed liquid detention time was maintained at 1 day, and the feed phenol concentration was doubled successively after each steady state from 358 mg/L for the first phase to 2864 mg/L for the fourth phase. Steady-state removal efficiencies of phenol, COD, and DOC of more than 99.9, 92, and 93%, respectively, were achieved even for the highest loading conditions (phenol surface load 0.23 mg COD/cm/sup 2/d). Very low effluent suspended solids concentrations and very low bacterial growth rates were characteristic features of the expanded-bed reactor.