| Polyacrylamide was tested as a flocculation aid by Syncrude Canada Ltd. because of its effectiveness in flocculating tailings without elevating salt concentrations. Residual acrylamide at low concentrations in polyacrylamide formulations has raised environmental concerns, because acrylamide has been considered to be toxic. This study investigated the activities of oil sands microbial consortia in the presence of polyacrylamide or acrylamide under sulfate-reducing or methanogenic conditions in laboratory microcosms. Low concentrations of acrylamide were degraded under aerobic, sulfate-reducing, methanogenic, and simulated environmental conditions by several environmental microbial consortia. Acrylamide at higher concentrations stimulated methanogenesis after an acclimation period. When supplied as a nitrogen source, polyacrylamide significantly enhanced methanogenesis, but under sulfate-reducing conditions, no conclusions could be drawn about polyacrylamide use as a nitrogen source. Acrylamide does not persist under any of the conditions tested in this study, and so likely would not pose an environmental risk when present in oil sands tailings. |
