University of Toronto Department

Biogeochemical Deflouridation

Kerry Tokaryk

Education

Ph.D. Candidate, Biogeochemistry, University of Toronto, Canada

B.Sc. Applied Mathematics & Geophysics (Environmental Modelling), University of Western Ontario, Canada

Research

At concentrations above 1 mg/L, fluoride in drinking water can be dangerous to human health, leading to dental and skeletal fluorosis, a disease that can cause mottling of the teeth, calcification of ligaments, crippling bone deformities, and many other physiological disorders that can, ultimately, lead to death. Exposure to fluoride is not a small problem. According to UNICEF, fluorosis is endemic in at least 25 countries around the world, and is most prevalent in India, China and Africa. It is not known how many people are currently afflicted with the disease, but conservative estimates are in the tens of millions of people. There is no treatment for fluorosis, which leaves prevention as the only means of controlling the disease. Worldwide, a major challenge, and the primary objective of Kerry’s research, is to develop effective and inexpensive techniques for the remediation of fluoride in groundwater.

Bioremediation approaches to defluoridation have not yet been investigated. An attractive aspect of fluoride bioremediation, particularly accelerated natural attenuation, is that defluoridation might be achieved quite effectively and with minimum intervention. There are three elements of accelerated natural attenuation of fluoride that need to be evaluated to assess bioremediation potential: (i) the impact of bacteria on fluoride chemical speciation in groundwater; (ii) the role of bacteria-mineral composites in fluoride immobilization; and (iii) the effects of bacteriogenic mineral formation on the solid-phase partitioning of fluoride. To address these issues, Kerry’s thesis will be divided into four separate, yet interrelated, sets of experiments that will investigate: 1) fluoride sorption to bacterial surfaces; 2) fluoride sorption to bacteria-mineral composites; 3) fluoride immobilization during microbial carbonate precipitation; and 4) fluoride immobilization by bacteriogenic iron oxides. This series of studies will not only be significant in that it will, for the first time, use a geomicrobial approach to address the issue of defluoridation, but it will also forge new ground in the unexplored area of anion bioremediation.

Research Sites

Talcher-Angul region, Orissa, India

Äspö Hard Rock Laboratory, Sweden

Deep River, Ontario, Canada