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The Trail Biochemical Reactor

On Wednesday, 16 October 2013, Laurentian-SETAC had the pleasure of hosting Dr. Allan Mattes as a Southern Ontario Pub Night guest speaker at Shakespeare’s Arms in Guelph, Ontario. Dr. Mattes, a Principal and Research Director at Nature Works Remediation Corporation, is also a recent Ph.D. graduate of University of Guelph, where he obtained his degree in Geomicrobiology, with a focus on the chemistry and biochemistry of arsenic. His talk, entitled “The Trail biochemical reactor and the removal of arsenic with a focus on the specific role of iron” drew quite a crowd and kept us all entertained for the duration of the presentation. We learned that Dr. Mattes, in collaboration with other Nature Works Principals, designed a biochemical reactor (BCR) that efficiently removes dissolved metal(loid)s from leachates at the site of a major lead-zinc smelter in Trail, BC. This BCR was initially intended to treat zinc (Zn) and sulphate through the formation of zinc sulphide, but high concentrations of arsenic (As) were also treated by the BCR; however, the mechanisms of removal of As were unknown. This led to the construction of a smaller scale BCR, with the purpose of elucidating the mechanisms involved in As removal. As part of his Ph.D. thesis, Dr. Mattes conducted an extensive analysis of As adsorption of the three substrate components (sand, limestone, and pulp and paper biosolids) of the smaller scale BCRs, and determined that iron oxidizing bacteria played an important role in As removal. Subsequently, he isolated, identified, and characterized these bacteria. His work demonstrated that As removal from leachates, through BCRs, is complex and it involves various mechanisms, such as the formation of the insoluble kottigite (Zn2(AsO4)3·7H2O) under aerobic conditions, co-precipitations on metal sulphides, and the formation of orpiment (As2S3)  in anaerobic conditions. The presentation was followed by a complex discussion on the composition of the bioreactor and on how the project came about. Everyone enjoyed the engaging talk, the delicious food, the cozy atmosphere and especially the fine brew. Submitted by Oana Birceanu

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