SULFREM - Sulfate removal from mine drainage

Description

Sulfate (SO42-) in mining environments is derived from either the oxidation of sulfide minerals, such as pyrite, or from the dissolution of sulfate minerals, such as gypsum. Once released, sulfate can occur at relatively high concentrations. The chronic effect of sulfate can cause serious harm to some freshwater species. In addition, elevated sulfate concentrations may have an indirect effect on aquatic ecosystems by increasing phosphorus availability and susceptibility to eutrophication, and by promoting mercury methylation. As a result, the regulation of sulfate discharge to water bodies has recently received increased attention in Sweden and new surface water quality criteria have been proposed. The SULFREM project develops a full-scale bioreactor technology for sulfate removal from mine water with a particular focus on mine waste water. The SULFREM technology removes sulfate through bacterial sulfate reduction to hydrogen sulfide, which precipitates as iron sulfide in solid form. For the full-scale installation, a SULFREM bioreactor will be connected to a denitrifying bioreactor already in operation at LKAB's Kiruna mine. The project consists of column experiments to determine optimal conditions for sulfate removal at low temperatures, as well as the design, construction, operation, and evaluation of a full-scale purification plant. Metal recovery from the bioreactor will be evaluated. Protective measures with SULFREM will enable mining companies to further reduce environmental impact, which in the future will allow for permits for new mines and continued operation at existing mining sites.