A duplicate column study of arsenic, cadmium and zinc treatment in an anaerobic bioreactor based on a system operated by Teck Cominco in Trail, British Columbia Kawaja, Jonathan D. E.; Morin, Katy; Gould, W. Douglas
The study’s objective was to identify and profile the treatment mechanisms within an anaerobic bioreactor (ABR) designed to remove high concentrations of arsenic, cadmium and zinc from contaminated drainage. The experiment used duplicate 15.6 L ABR columns, containing limestone and an organic substrate. The design and operation parameters were based on a larger field scale system operated by Nature Works Remediation for Teck Cominco in Trail, British Columbia. After an acclimatization period, the experiment was conducted for six months at various hydraulic loadings intended to evaluate optimal and stressed conditions, as well as, the ABR’s ability to re-establish optimal conditions. The study suggested that cadmium and zinc were removed as metal sulphides after 20 hours residence time. The behaviour of arsenic was independent of cadmium and zinc, and the majority was removed within 7 hours residence time. This was attributed to its adsorption to iron. Correlations of arsenic and iron concentrations throughout the organic substrate demonstrated that adsorption was inconsistent and unreliable as a treatment mechanism without the subsequent oxic conditions at the column’s headwater. Considerations for the field were identified for treatment, management of hydraulic loadings, and maintenance of an ABR.
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