Effects of perfluoridation on removal of particles and organic matter

For the past decade, US water utilities have been working to optimize their treatment processes to meet increasingly stringent regulations. Of the many unit processes employed in conventional treatment, water fluoridation appears to have been overlooked as a potential obstacle to effective compliance with the new requirements, A review of treatment plant schematics collected for the Information Collection Rule found that many utilities add fluoride to the process train at points where it can interfere with particle and natural organic matter (NOM) removal. In this research, bench- and pilot-scale studies provided evidence that addition of fluoride to water prior to treatment with aluminum sulfate (alum) can severely affect removal of turbidity and NOM under enhanced coagulation conditions. Utilities disregarding these effects may face increased chemical costs, lower removal of organic matter and disinfection by-product precursors, elevated concentrations of aluminum in the finished water, shorter filter run times, and the potential for turbidity breakthrough in filters.