Abstract
The MacLeod Mine, near Wawa Ontario was an underground iron mine operated by Algoma Steel until 1998. Since closure, the mine voids have been filling with acidic water containing high iron concentrations due to the presence of pyrrhotite. In order to protect the local environment, this water must be pumped out and treated to strict environmental requirements before discharge. In 2017, a high-density sludge (HDS) treatment plant was constructed to meet these high discharge standards. While the traditional HDS process was applied, this plant contained a number of innovative designs for improved operational efficiency and reliability. These improvements included a clarifier designed to deal with viscous sludge, positive displacement pumps for the clarifier underflow sludge, a lime slaking and slurry system design that improves reliability through a gravity-feed, peristaltic pumps for lime dosing, and an innovative design for the Lime/Sludge Mix Tank. After five years of operation, the success rate of these innovations is discussed. Also discussed are lessons learned for future improvements after dealing with issues regarding operation, the raw water feed, and grit management, for example.