Ozonation in view of micropollutant removal from biologically treated landfill leachate: Removal efficiency, [rad]OH exposure, and surrogate-based monitoring

Abstract

The presence of micropollutants (MPs) in landfill leachate is attracting growing attention. Although ozonation is an effective oxidative treatment technique, knowledge of the removal efficiency and mechanisms of MPs from leachate by ozonation is scarce. In this work, biologically treated leachate spiked with carbamazepine, bisphenol A, atrazine, and alachlor was subjected to ozonation in a semi-continuous mode. No dissolved ozone was detected before 0.95 gO3/g DOC was dosed, indicating the specific initial ozone demand (IOD) of the leachate. This ozone dose was sufficient for a 99% removal of carbamazepine and bisphenol A, both characterized by a high ozone reactivity (kO3 > 104 M−1s−1). However, the more ozone-recalcitrant atrazine and alachlor were removed lower than 40%, indicating that commonly applied ozone doses (similar to IOD) are not sufficient for effective ozone-recalcitrant MPs removal. Given the importance of OH in removing such recalcitrant MPs, the OH formation was characterized by the ROH,O3 concept. The OH formation yield indicated by ROH,O3 value , increased with the applied ozone dose and varied between leachate samples due to the variation in organic composition, suggesting that it is impractical to predict MPs removal with OH formation yield information alone. As such, a surrogate-based model was proposed for the prediction of MPs abatement using spectroscopic measurements. The developed UVA254-based model exhibited a good predictive power for the abatement of ozone-recalcitrant MPs (R2 > 90%) in landfill leachates with different organic characteristics. This study provides valuable information for understanding occurring reactions and predicting MPs removal during landfill leachate ozonation.