An integrated system for the bioremediation of wastewater containing xenobiotics and toxic metals

Abstract

An integrated system for the biotreatment of acidic wastewaters containing both toxic metals and organics is presented. It consists of two bioprocess stages (i) an anaerobic, SRB stage (containing alkaline-tolerant sulfate-reducing bacteria) that at pH 8 (chosen to acclimatize the bacteria in the biomedium) produces high concentrations of total sulfide ions (more than 400 mg/L) which are added to the wastewater to precipitate the heavy metals out at pH 2 as metal sulfides, and (ii) an aerobic, acidophilic stage containing heterotrophic bacteria (WJB3) that degrade organic xenobiotics. The anaerobic system was comprised of a 4-L fluidized bed bioreactor with immobilized SRB, a mixing tank, and a precipitation tank. The effluent from the bioreactor with a high concentration of sulfide ions was fed into a mixing tank where model wastewaters containing toxic metals and phenol at pH 2 were also fed at increasing loading rates until free metal ions could be detected in the precipitation tank outlet. Then the effluent from the precipitation tank outlet was fed into a 2.5-L aerobic bioreactor in which phenol was degraded. In this research, 100% removal efficiencies were obtained with wastewaters containing more than 400 mg/L metal ions and 900 mg/L phenol at a 6-h HRT of the mixing tank. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.