Abatement of ozone-recalcitrant micropollutants during municipal wastewater ozonation: kinetic modelling and surrogate-based control strategies

Abstract

Although ozonation is nowadays recognized as one of the most efficient technologies for micropollutants abatement in municipal wastewater effluents, several of the compounds potentially present in those waters exhibit a strong resistance to direct ozone oxidation. In addition, the real-time control of the removal process is still challenging. In this work, the abatement of ozone-recalcitrant micropollutants during wastewater ozonation of six different wastewater effluents was explored using the pesticide acetamiprid as hydroxyl radical (¿OH) probe. By means of this data, the oxidation efficiency (i.e., hydroxyl radical exposure per consumed ozone) could be described by means of a two-stage model based on the ROHO3 concept. This was possible using a semi-continuous bubbling ozone contactor in all experiments, which permitted the inclusion of the ozone mass balance in the model. ROHO3 values of (1.53-7.60)·10-7 s for initial ozonation stage and (0.61-2.95)·10-6 s for the secondary stage were obtained allowing the characterization and comparison of the process performance in a wide range of effluent qualities, including water matrices with a high content of dissolved and particulate organic matter (total organic carbon (TOC), dissolved organic carbon (DOC) and turbidity tested ranges: 6.7-50 mg C L-1, 6.6-27.6 mg C L-1 and 0.3-28.6 NTU, respectively). Finally, a surrogate strategy involving ¿OH exposure estimation by means of ultraviolet absorbance at 254 nm (UVA254) measurements was proposed based on the ROHO3 concept, and by means of its application the removal of atrazine and ibuprofen in six different wastewaters could be rightly predicted (R2 > 0.98).