Ferrate(VI) Transformation of Nitrogen in Secondary Wastewater Effluent: Implications for Water and Nutrient Management

Ferrate(VI) is a promising chemical agent for wastewater treatment. While targeting various contaminants, it can inevitably react with different water matrix constituents such as nitrogen (N) species. However, the reactions of ferrate(VI) with wastewater N compounds remain poorly understood. This study explores ferrate(VI)-mediated transformations of different N species in a secondary wastewater effluent. Ferrate(VI) oxidation minimally abated total dissolved nitrogen (TDN), while oxidizing dissolved organic nitrogen (DON) into dissolved inorganic nitrogen (DIN), primarily nitrate nitrogen (NO₃^--N), without noticeably altering ammonia nitrogen (NH₃-N) levels. Consequently, ferrate(VI) treatment increased the fraction of bioavailable, soil-leachable NO₃^--N while lowering the portion of less bioaccessible DON. This study reveals the ability of ferrate(VI) to retain overall nitrogen, improve its bioavailability, mitigate the precursors of harmful nitrogenous disinfection byproducts, and enhance nitrogen leachability in soil. These insights highlight the complex impacts of ferrate(VI)-enabled wastewater treatment on human and environmental health, water supply, and nutrient management in agriculture reuse.