Sulfite-activated ferrate for water reuse applications

Ferrate is a promising, emerging water treatment technology. However, there has been limited research on the application of ferrate in a water reuse paradigm. Recent literature has shown that ferrate oxidation of target contaminants could be improved by "activation" with the addition of reductants or acid. This study examined the impact of sulfite-activated ferrate in laboratory water matrix and spiked municipal wastewater effluents with the goal of transforming organic contaminants of concern (e.g., 1,4-dioxane) and inactivating pathogenic organisms. Additionally, the formation of brominated disinfection byproducts by activated ferrate were examined and a proposed reaction pathway for byproduct formation is presented. In particular, the relative importance of reaction intermediates is discussed. This represents the first activated ferrate study to examine 1,4-dioxane transformation, disinfection, and brominated byproduct formation. Results presented show that the sub-stoichiometric ([Sulfite]:[Ferrate] = 0.5) activated ferrate treatment approach can oxidize recalcitrant contaminants by >50%, achieve >4-log inactivation of pathogens, and have relatively limited generation of brominated byproducts. However, stoichiometrically excessive ([Sulfite]:[Ferrate] = 4.0) activation showed decreased performance with decreased disinfection and increased risk of by-product formation. In general, our results indicate that sub-stoichiometric sulfite-activated ferrate seems a viable alternative technology for various modes of water reuse treatment.