<i>E. coli</i> Inactivation by Metals and Effects of Changes in Water Chemistry

Abstract

Microbiologically unsafe drinking water remains a leading cause of child morbidity and mortality in the world despite high investment in water-treatment infrastructure. This study explores the antimicrobial potential of Ag, Cu, Zn, Ni, and Co, at concentrations below the World Health Organization drinking standards, to inactivate a nonpathogenic strain of E. coli in synthetic groundwater (SGW). Disinfection capabilities of Ag and Cu are also tested against bacteria in natural surface water (NSW) to test the effect of a natural and more-complex water chemistry. The influence of changes in pH, Cl−, HCO3−, Mg2+, and Ca2+ concentrations on bacterial inactivation in SGW are also studied. The MINTEQ equilibrium model is used to study the speciation of the metals in solution. The Chick–Watson model is employed for kinetic modelling of the data. The results show that greater than 99.99% bacterial inactivation occurs within 12&nbsp;h of contact time by Ag and Cu. Concentration and time played a major role in the disinfection process. Co and Ni are ineffective disinfectants. Higher inactivation of E. coli by Ag and Cu is recorded in SGW than in NSW. The inactivation efficiencies of the metals studied follow the trend Ag&gt;Cu&gt;Zn&gt;Ni≈Co.