There is a critical need for innovative solutions to better manage industrial wastewaters. Currently, it is difficult for mines across the entire extractive resource industries, to design tailings impoundments, develop effective monitoring and treatment technologies, or robust closure plans, because they do not have sufficient knowledge of the reaction mechanisms and controls for the microbially driven processes that can lead to environmental impacts such as acidification, toxicity and oxygen consumption. Far less studied than acid mine drainage (AMD), mining wastewater systems receive a greater diversity of waste-derived sulfur constituents than AMD, their microbial communities are largely undescribed and these waters can experience significant seasonal variability. Here, the objectives of a pilot study were to establish the sulfur biogeochemistry and microbial community and metabolic networks of a Ni/Cu mine wastewater system in northern Ontario. Samples were collected from the tailings impoundment and its diverse wastewater inputs at two seasonal time points (September and November 2014) for joint, genome-resolved metagenomic analyses and geochemical characterization. 

Results identified wide ranging geochemical conditions across waste rock, tailings deposit, and adjacent mine wastewater inputs and the oxidation reservoir itself (i.e. pH: <3 - >11; %O2: 13 - >100; °C: 4 - 25).  In the oxidation reservoir, while total sulfur concentrations were very similar, (~10 mM), seasonal differences in the relative abundances of different sulfur oxidation intermediate species associated with lowered temperature, and increased %O2 and [NO3-] occurred.  Genome-resolved metagenomics analyses identified distinct communities with many novel organisms across the different sampling points. In all communities, extensive oxidative sulfur as well as nitrogen reduction (nitrate, nitrite) metabolism capabilities were present. Companion laboratory experimentation combining geochemistry with proteomics revealed correlative relationships between sulfur gene expression and observed solution sulfur geochemistry. These results highlighting the promise of genomics integrated investigation to generate new tools needed for the industry to better manage sulfur compounds will be presented.

Professor Lesley A. Warren
Claudette Mackay Lassonde Chair in Mineral Engineering
Department of Civil and Mineral Engineering
University of Toronto


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