Toward Robust ARB Inactivation in Wastewater: Comparing Performic Acid, Peracetic Acid, and Chloramination Using ICT, Resistance, and Reactivation Metrics

Antimicrobial resistance (AMR), particularly vancomycin-resistant enterococci (VRE), poses a critical global health threat. Although wastewater disinfection limits pathogen dissemination, conventional chlorine-based disinfection can be ineffective against antibiotic-resistant bacteria (ARB) and may induce viable but nonculturable (VBNC) states. This study compared performic acid (PFA), peracetic acid (PAA), and sodium hypochlorite (NaOCl) for inactivation of VRE and total enterococci (TE) in high-ammonia secondary effluent. Batch disinfection experiments were conducted using an integrated concentration-time (ICT) framework, assessing microbial survival under standard (24 h) and extended (3-5 days) incubation, to quantify posttreatment recoverability (reactivation/regrowth). PFA achieved rapid and consistent inactivation within the effective linear range, whereas PAA exhibited slower, variable kinetics with distinctive shouldering. NaOCl proved the least reliable and displayed a "lower dose advantage." Reactivation was strongly dependent on inactivation magnitude. At the doses investigated, only PFA consistently achieved > 2.5-log reductions associated with minimal recovery. By comparison, PAA and NaOCl did not reach inactivation levels adequate to suppress reactivation within the tested ICT ranges, indicating VBNC states and regrowth. Within the tested ICT ranges in GLWA secondary effluent, these findings suggest PFA is a promising alternative disinfectant for controlling ARB and provide a reactivation-aware framework for setting exposure targets based on durable, not just immediate, inactivation.