Ozone Disinfection Efficiency for Indicator Microorganisms at Different pH Values and Temperatures

Disinfection efficiency of ozone was determined in various types of water at different pH (6, 7 and 8) values and temperatures (15, 25 and 35 °C) for E. coli and Salmonella. Three different applied ozone concentrations (1.5, 1.7, and 2 mg/L) in the gas phase were applied, and samples were taken at different time intervals to determine microbial survival using spread plate count (SPC) and ozone residual. Highest microbial inactivation was observed in distilled water with applied ozone concentration of 2 mg/L in the gas phase. Survival of E. coli was higher at pH 8 and 15 °C as compared to lower pH values and temperatures as depicted by the inactivation kinetics of the test microbes used in the study. Salmonella showed 5 and 6 log removal after contact time of 45 and 60 sec, respectively, at 2 mg/L. Disinfection of mixed culture showed relatively more survival of E. coli; as 3 and 4 log removal of E. coli and 4 and 5 log removal of Salmonella was observed after 45 and 60 sec.