Engineering Ferrate(VI) for Water and Wastewater Treatment: Translating Science into Technology

Over the past five decades, ferrate(VI) (FeO42-) for water and wastewater treatment has remained largely at the laboratory scale, with limited pilot- and full-scale implementation. This gap between sustained research and scarce real-world deployment places the technology in the Valley of Death─a high-risk stage of development─and highlights the need for an engineering-centric approach to enable practical application. This article presents an engineering framework to guide the development and translation of ferrate(VI) technology for water and wastewater treatment. From a system perspective, ferrate(VI) technology comprises three core subsystems: generation, treatment, and solid-liquid separation. Technology maturity depends on both the advancement of individual subsystems and their effective integration. Key obstacles and corresponding engineering strategies are identified for each subsystem. Among them, ferrate(VI) generation, despite commercial availability, remains the primary bottleneck due to limited industrial adoption driven by challenges related to chemical instability, residual impacts, and energy demand. As subsystem maturity progresses, system-level integration emerges as a critical challenge, requiring alignment among subsystems or with existing infrastructure under different implementation configurations. To advance ferrate(VI) technology across the Valley of Death, we emphasize maturity stage-aligned development, integrated system design, and application-specific decision frameworks.