Reduction of Escherichia coli bacteria from contaminated water by combining hydrogen peroxide, ozone and ultraviolet light

This study demonstrates the reduction of Escherichia coli bacteria from contaminated water when the water is treated with advanced oxidation processes utilising the following combinations: hydrogen peroxide (H₂O ₂) and ozone (₃), ultraviolet light (UV) and hydrogen peroxide (H₂O₂), and ultraviolet light (UV) and ozone (₃). Approximately 1 × 10⁸ cell/mL of E. coli were spiked into water samples contaminated with 500 ppb of methyl tertiary butyl ether (MTBE) and benzene. Water samples were then treated in a bench-scale photoreactor using 15 W low pressure (LP) and 150 W medium pressure (MP) UV lamps. Hydrogen peroxide at 20, 50 and 100 ppm and ozone at 1, 2 and 5 ppm were used along with the UV irradiation to generate the hydroxyl radicals (.OH) needed to degrade organic contaminants such as MTBE and benzene and most likely destroy bacteria. The results of the study showed that, under the study conditions, no effect of benzene or MTBE was observed on the inactivation rate of the bacteria. Moreover, results showed that the combined effect of the LP 15 W UV lamp with 2 ppm ₃ or with 50 ppm H₂O₂ showed the highest inactivation rate of bacteria within 5 min. The H ₂O₂/₃ process showed high disinfection capability at high dosages of peroxide (50 ppm) and ₃ (2 and 5 ppm).