The geochemistry of fluoride and chemical reactions that control fluoride fate and transport in the natural environment have been widely studied and are well understood. Geochemical and reactive transport models using software like PHREEQC and Geochemists’ Workbench® are useful for evaluating processes affecting fluoride fate and transport in natural environments but have important limitations when applied to regulated sites.
Industrial processes produce fluoride waste streams that often exist at geochemical extremes. Examples include gypsum stack ponds from phosphate fertilizer production that contain fluoride-bearing water at acidic pH; and spent potlining landfills from aluminum production or coal combustion residual landfills with porewaters that are typically at alkaline pH. Fluoride-bearing solids such as silicofluorides and elevated dissolved metal concentrations that may form fluoride complexes are also frequently present, and there is typically no thermodynamic data available.
Addressing fluoride concerns requires specialized expertise. Results of costly desktop fluoride geochemical and reactive transport modeling have inherent uncertainty. There is no substitute for analysis of field measurements to inform conceptualization of fluoride source, transport, and fate. Informing remediation decision making on concrete measurements as opposed to investing in refining costly theoretical models can lead to cost and time savings by identifying and focusing remediation efforts on key problem areas.
EHS Support is a global leader in fluoride remediation. Our Fluoride Fate and Transport SGP, which is part of our long-term growth plan, is focused on addressing anticipated client needs, including research in regulatory trends and changes, as well as scientific advancements. As part of our investment in studying fluoride fate and transport, we are developing empirical sampling strategies and data assessment techniques that work where more complex theoretical models fail. In short, we aim to provide higher confidence in information used for remediation decision making to minimize cost overruns and preserve resources.
Andrew Fowler
Senior Geologist/Geochemist at EHS Support
