Resilient Water Treatment Technologies and Challenges for the Removal of Emerging Contaminants - Perfluorinated Compounds

摘要

Due to their global presence, persistence, and adverse health effects, perflurinated compounds (perfluoroalkyl and polyfluoroalkyl substances PFASs) have become major chemical of concern for drinking water supplies worldwide. Presence of these PFCs in various geographical regions and environmental matrices across globe has been well documented in literature. This range from drinking water in New Hampshire, USA to arctic ice to surface waters in Asia, and Europe to aquatic life, and so on. Presence of long chain, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) have received greater attention from the drinking water utilities in recent years in United States. US EPA has recently issued a revised health advisory for PFOA and PFOS concentrations to 70ng/L. Corresponding health advisory for shorter chain (C4-C7) perflurinated compounds is 300-7000ng/L. This widespread nature of these contaminants has made a strong need for identifying appropriate and resilient water treatment technologies that can be incorporated in existing drinking water infrasturecures. Detection and accurately quantifying these chemicals of concern at such low level (ng/L) pose a bigger analytical challenge for researchers. There is a strong need to develop more cost-effective ways to determine such contaminants so that these PFCs can be monitored on a more regular basis. PFOA and PFOS's low volatility and high water solubility makes it harder to effectively and efficiently remove these contaminants using many conventional treatment technologies. This paper outlines major treatment technologies that can be incorporated in existing water infrastructure. Two major such technologies are adsorption (granulated and powdered activated carbon) and membrane filtration (reverse osmosis, nanofiltration etc). Concentrated brine generation during water treatment limits the use of membrane filtration in water scarce areas. Adsorption using activated carbon has proved to be effective in removing these perfluorinated compounds. Presence of such GAC/PAC systems in existing drinking water treatment trains make these technologies more attractive. New advances in carbon materials has further improved the removal efficiencies of PFOA and PFOS. However, disposal of spent media (carbon) may pose a greater threat as incinerating such material requires energy. To make such process energy efficient, more research is required to develop novel sorbents for PFOA and PFOS removal.