Evaluation of the ASTER~(TM) process in the presence of suspended solids

摘要

The ASTER~(TM) process has been used for bioremediation of cyanide (CN) and thiocyanate (SCN) containing effluents at demonstration and commercial scale. The process relies on a complex consortium of microorganisms and laboratory tests have shown that the biomass retention, in suspended floes or attached biofilm, significantly improved SCN" degradation rates. The current research evaluated the process performance in the presence of suspended solids (up to 5.5% m/v) ahead of implementation at a site where complete tailings removal is not possible. Experiments were performed in four 1 I CSTRs (with three primary reactors in parallel at an 8 h residence time, feeding one secondary reactor at a 2.7 h residence time). Stable operation at the design specifications (5.5% solids, 450 mg/l SCN~- feed, effluent SCN~- <1 mg/l) was achieved within 200 days, including a period of adaptation. A maximum SCN~- degradation rate of >57 mg/l/h was achieved, despite no obvious floe formation. Microbial ecology studies (16S rRNA clone library) revealed reduced diversity relative to reactors operated without suspended solids.