Wastewater disinfection with Peracids - A batch and pilot study

The objective of this project was to evaluate the effectiveness of peracids-specifically performic acid (PFA) and peracetic acid (PAA)]-for disinfection of wastewater effluents. The study further benchmarked PFA against PAA and chlorine, the latter applied as sodium hypochlorite (SH). Bench- and pilot-scale investigations were conducted to assess in activation of bacterial indicators (total and fecal coliform, E. coli, enterococcus), spore surrogates (Aspergillus brasiliensis), viral indicators (F+ coliphage [MS2] and murine norovirus), and formation of disinfection by-products (DBP). This abstract summarizes the finding from Water Research Foundation Project # 5219, 'Performic Acid Disinfection in Wastewater Effluent and Combined Sewer Overflows (CSOs) in Context of Disinfection By-Products and Future Ambient Water Quality Criteria for Viruses.' Ten wastewater treatment plants (WWTPs) across the United States and Canada participated in this study. Bench-scale testing was conducted using secondary effluent from all the 10 WWTPs and CSO samples from 2 WWTPs. A pilot study is currently being commissioned at Great Lakes Water Authority WWTP in Detroit, Michigan. Bench scale experiments evaluated three chemical disinfectants (PFA, PAA and SH) at two dose levels (2 and 4 mg/L), and across six contact times (0,1,3,5,10, 30 and 60 minutes). Samples collected at each time point were analyzed for residual disinfectant and microbial indicators. Spiking studies using Aspergillus brasiliensis, MS2, murine norovirus and DBP formation assays were conducted for four of the participating WWTPs. The pilot system is being prepared for commissioning in early February 2026 and is planned to operate for 16 weeks (Figure 1 – Pilot racks). Bench scale results indicate that PFA outperforms both PAA and SH, achieving greater microbial inactivation (Figure 2, Figure 3, Figure 4) and generating substantially lower DBPs formations (Table 1). Although preliminary cost estimates suggest PFA may be more expensive than SH, its lower dose requirements and strong virus inactivation performance suggest that PFA may offer a more attractive overall disinfection option.