Stabilisation of iron mine tailings through biocalcification

Abstract

Mine tailings consist of fine-grained particles that are deposited into large impoundments. Seasonal temperature and moisture fluctuations can result in dust emissions, an environmental hazard. Accordingly, there is a need for efficient and economical means for controlling dust emissions. Biogeotechnics provides one innovative approach to modifying soil properties. For example, Sporosarcina pasteurii has been studied for its ability to promote biocalcification in sand-sized particles by way of ureolysis. The application of this process to fine-grained materials, however, poses unique challenges. The goal of this work was to demonstrate biocalcification in fine-grained mine tailings to promote the formation of a crust that increased the surface strength of the tailings. Soil box experiments coupled with multiple lines of evidence collected using novel analytical techniques were used to confirm (a) the successful formation of the surface crust by way of ureolysis mediated by inoculated S. pasteurii and native urea-degrading microbes and (b) the impact of the crust on the surface strength of tailings. The crust formation and increased surface strength demonstrated in tailings inoculated with S. pasteurii and with native microbes provide a foundation for further research to advance the application of biogeotechnics in fine-grained materials for purposes such as dust mitigation.