PFA technology: Production, safety and wastewater deployment analysis

Performic acid (PFA) is receiving increasing attention as a fast-acting disinfectant for municipal wastewater effluents and combined sewer overflows (CSOs), where short contact times and highly variable matrices constrain conventional treatment. However, its practical adoption is limited by intrinsic chemical instability, safety considerations, and dependence on point-of-use generation. This critical review integrates peer-reviewed literature and patent evidence to evaluate how PFA production and delivery architectures govern field deployability. We compare five technology families including on-site precursor blending, distillation and reactive separation, co-delivery formulations, microfluidic on-demand generation, and electrochemical synthesis using structured evidence base and readiness-aware scoring framework. Performance is interpreted through the lens of time-integrated residual exposure, reflecting rapid oxidant decay and matrix-dependent demand. Reported full-scale and pilot studies indicate that PFA can achieve rapid bacterial inactivation at low exposure values, and, in some cases, strong target-dependent viral inactivation, often with lower halogenated by-product formation than chlorination, but outcomes are highly sensitive to mixing, particulate shielding, and early-time oxidant consumption. Comparative analysis shows that on-site blending remains the only widely validated municipal-scale approach, while microreactors and reactive separation offer higher attainable strengths at the expense of scale-up and operational complexity, and electrochemical routes remain constrained by low titers and limited dynamic response. By linking disinfection performance to production logistics, safety, and control requirements, and environmental acceptability, this review provides an exposure-anchored framework for technology selection and identifies priority research needs for advancing PFA toward robust, scalable, and regulation-ready deployment in wastewater and CSO disinfection.