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Toward Robust ARB Inactivation in Wastewater: Comparing Performic Acid, Peracetic Acid, and Chloramination Using ICT,
Nuha Alfahham1,2, Katherine Y Bell3, Reem Suleiman4
1Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.
Summary
Performic acid (PFA) effectively inactivates antibiotic-resistant bacteria in wastewater, unlike chlorine-based disinfectants. This study shows PFA minimizes regrowth by achieving durable inactivation, crucial for public health.
Area of Science:
- Environmental microbiology
- Water treatment technologies
- Public health
Background:
- Antimicrobial resistance (AMR), especially vancomycin-resistant enterococci (VRE), is a major global health concern.
- Conventional wastewater disinfection using sodium hypochlorite (NaOCl) may be ineffective against antibiotic-resistant bacteria (ARB) and can induce viable but nonculturable (VBNC) states.
Purpose of the Study:
- To compare the efficacy of performic acid (PFA), peracetic acid (PAA), and NaOCl in inactivating VRE and total enterococci (TE) in wastewater.
- To evaluate the potential for microbial regrowth after disinfection under varying incubation periods.
- To establish a framework for setting disinfection targets based on durable inactivation.
Main Methods:
- Batch disinfection experiments were conducted using an integrated concentration-time (ICT) framework.
- Evaluated inactivation of VRE and TE in high-ammonia secondary effluent.
- Assessed microbial survival and recovery after standard (24 hours) and extended (3-5 days) incubation.
Main Results:
- PFA demonstrated rapid and consistent inactivation kinetics, achieving significant log reductions.
- PAA showed slower, variable inactivation with noticeable "shouldering," while NaOCl was the least reliable.
- Only PFA consistently achieved >2.5-log reductions, leading to minimal post-treatment recovery, unlike PAA and NaOCl which did not prevent regrowth.
Conclusions:
- PFA is a promising alternative disinfectant for controlling ARB in wastewater, offering more reliable and durable inactivation than PAA or NaOCl.
- The findings highlight the importance of considering microbial regrowth and VBNC states when assessing disinfectant efficacy.
- A reactivation-aware framework is proposed for setting wastewater disinfection targets based on sustained inactivation levels.
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