Pilot-scale evaluation of sulfite-activated ferrate for water reuse applications

Ferrate is a promising, "green" (i.e., iron-based) pre-oxidation technology in water treatment, but there has been limited research on its potential benefits in a water reuse (wastewater recycling) paradigm. Recent studies have shown ferrate treatment processes can be improved by activation, the addition of reductants (i.e., sulfite) to the reaction. Prior bench scale experimentation suggests sulfite-activated ferrate may be a feasible option for water reuse applications; however, extent questions need to be addressed. This study evaluated the viability of sulfite-activated ferrate in water reuse treatment through continuous-flow experiments using synthetic and field-collected secondary wastewater effluents. The effluents were processed through the piloting system which included various physicochemical processes such as ferrate pre-oxidation, coagulation, clarification, and dual-media filtration. In each trial, the system was run continuously for eight hours with data collected via grab samples and online instrumentation with real-time resolution. Results demonstrate that reuse systems using activated ferrate pre-oxidation can produce effluents with water quality meeting most regulatory requirements without major impacts on downstream physicochemical processes. When compared to traditional ferrate pre-oxidation, activation showed several improvements such as lower byproduct yields. Operationally, activated ferrate does increase the development of headloss across the dual-media filter. In general, sulfite-activated ferrate is viable in a water reuse setting, resulting in several improved water quality outcomes. Results from this work create a pathway for adaptation at scale.