On the capacity of ozonation to remove antimicrobial compounds, resistant bacteria and toxicity from urban wastewater effluents

Abstract

•Erythromycin and ethylparaben were rapidly eliminated within 2min at low O3 doses.•5 Transformation products (TPs) were identified retaining the ERY lactone ring.•EtP structural alterations took place at the ethyl ester chain yielding 15 TPs.•Phytotoxicity can be attributed to the organic matter and its oxidation products.•ERY- and EtP-resistant E. coli were eliminated after 15min of ozonation.

The degradation of erythromycin (ERY) and ethylparaben (EtP) in urban wastewater effluents at low concentration level during ozonation was investigated under different experimental conditions. Both substrates were rapidly eliminated within 2min at low ozone dose of 0.3mgL−1 and the experimental data were well fitted in the pseudo-first-order kinetic model. The ratio of HO- and O3-exposure (Rct) at the inherent pH was found to be 1.9×10−8. The degradation of ERY and EtP was pronounced at pH 8 compared to acidic pH conditions, while the degradation rate of both substrates was found to be matrix-depended. It was also shown that both O3- and HO-mediated pathways are involved in the degradation of EtP, whereas the saturated-rich structure of ERY renders it O3-recalcitrant. Under the optimum O3 dose, the BrO3− concentration was found to be lower than 10μgL−1. Five and fifteen transformation products were elucidated during ERY and EtP oxidation, respectively. The root and shoot inhibition can be attributed to the oxidation products formed upon dissolved effluent organic matter transformation. Escherichia coli harbouring resistance to ERY survived ozonation better than EtP-resistant E. coli. However, neither ERY- nor EtP-resistant E. coli were detected after 15min of ozonation.