Résumé - Abstract
Permeable reactive barriers (PRBs) that promote biologically mediated sulfate reduction are a long-term passive remediation strategy to treat mine drainage. Often these treatment systems are composed of low-cost, locally available organic materials such as compost, sawdust or wood chips. Emulsified vegetable oil (EVO) has been shown to be very effective in promoting bioremediation with the benefit of being injectable to renew depleted organic-carbon supplies over time. Four flow-through column experiments treating simulated mine-impacted groundwater are being conducted to evaluate the incorporation of EVO into an organic carbon PRB through two methods: soaking and injection. The effectiveness of treatment will be evaluated using traditional aqueous geochemical measurements. A comparison of the EVO mobility that results from soaking and injection will be constrained by quantifying various organic components in the effluent and solid components before, during and after the experiment is concluded. The primary mechanisms of contaminant immobilization will be evaluated through collection of solid phase samples that will undergo geochemical characterization and mineralogical techniques. Contaminant immobilization mechanisms will be further constrained by geochemical modelling of saturation indices and the use of iron isotope measurements conducted on the porewater samples. In addition to the aqueous and solid phase geochemical measurements sulfur and carbon isotope measurements from porewater will be used to evaluate the biogeochemical processes of dissimilatory sulfate reduction and methanogenesis occurring within the columns and inform the biogeochemical conceptual models of PRB treatment. The results of these experiments will demonstrate potential performance benefits of incorporating EVO into an organic matter PRB in treatment systems designed to remediate acid mine drainage.