| A study of the removal of arsenate from contaminated water has been conducted based on a field scale anaerobic bioreactor in Trail, BC. Arsenic, zinc and iron are effectively removed by the bioreactor but the mechanism of removal is not well understood. Bench-scale models of this bioreactor were used for detailed analysis and results indicated that the addition of iron, copper and zinc increased arsenic removal efficiency. Solid samples from the bench scale bioreactors and from the Trail reactor were analyzed using X-ray absorption near edge structure (XANES), aqua regia digestion and the toxicity characteristic leaching procedure (TCLP). XANES results indicated that all samples from anaerobic bioreactors contained amorphous orpiment. TCLP results indicated low arsenic leachability in all samples. The results of this research suggest that in the Trail bioreactor, arsenic is removed by sulfide precipitation and that iron, zinc, and copper may play an important role in arsenic immobilization.;Key words: Arsenic, bioreactor, water treatment, wetland, XANES. |
