Sulfate Radical-Induced Disinfection of Pathogenic Escherichia coli O157:H7 via Iron-Activated Persulfate

Abstract

Sulfate radical (SO4•-) has been increasingly applied as an efficient oxidant for water treatment in recent years. This study investigated the disinfection efficacy of SO4•- on Escherichia coli O157:H7, i.e., a pathogenic strain of E. Coli on the U.S. Environmental Protection Agency's Contaminant Candidate List. SO4•- was generated via persulfate (S2O82-) activation using ferrous iron (Fe2+). Results showed that S2O82- activation and subsequent SO4•- exposure induced the loss of pathogenic E. Coli viability. The disinfection, kinetics exhibited an induction phase followed by a rapid first-order decay phase. Dosages of S2O82- and Fe2+ significantly impacted the duration of the induction phase and the rate of disinfection; on the other hand, the solution pH preferentially impacted the induction time, and the dosage of Fe3+-reducing agent hydroxylamine (NH2OH) impacted the rate of disinfection. The disinfection kinetics depended on the CT equivalence of total SO4•- exposure. Results showed that SO4•- exposure initiated the loss of E. Coli O157:H7 cell viability 5 times faster than HO• exposure did. This unique feature of SO4•- is possibly associated with its highly selective reactivity with electron-rich moieties on the surface of E. Coli O157:H7 cell membranes.