Ozone-based water treatment (O3, O3/UV, O3/H2O2) for removal of organic micropollutants, bacteria inactivation and regrowth prevention

Abstract Ozone-based water treatments were investigated to simultaneously remove organic micropollutants (OMPs) and bacteria from surface water samples collected in a river reservoir supplying a drinking water treatment plant. Among the 21 environmentally relevant OMPs selected, 15 were detected at low ( mg O 3 L-1 and HRT: 10 min). Under these conditions, the removals of spiked OMPs were also higher than 85% (except for PFOS), whereas bacteria (i.e., total heterotrophs at 37 and 22 oC, E. coli and enterococci) decreased to values lower than the permissible levels for drinking water, even upon storage for 3-days. However, lower ozone doses (1.5 mg O 3 L-1) could not prevent the regrowth of total heterotrophs incubated at 37 oC, which reached levels five times higher than those recommended. Because drinking water treatments should not only consider OMPs abatement but also microbial inactivation for long periods of time, the results herein obtained point out the importance of using ozone doses capable of accomplish both targets when using single ozonation.