Sulfate Radical-Induced Disinfection of Pathogenic <i>Escherichia coli</i> 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.