Continuous versus single H₂O₂ addition in peroxone process: Performance improvement and modelling in wastewater...

Ozonation combined with continuous addition of H₂O₂ was studied as potential strategy for the effective abatement of ozone-resistant micropollutants from wastewater effluents. Oxidant doses within and beyond immediate ozone demand completion were tested. Through experiments involving the continuous addition of H₂O₂ in a semi-continuous contactor, it was demonstrated that this new approach could lead to a 36 % reduction of the overall O₃ needs for a constant H₂O₂/O₃ molar ratio of 0.25 compared to single ozonation, representing a 28 % reduction in energy consumption. This improvement was mainly attributed to H₂O₂ addition during the secondary ozonation stage, where the direct ozone demand becomes less important. The OH-exposure per consumed ozone (i.e., R_OHO3 concept) calculation demonstrated that higher (0.5-1) and lower (0.25) oxidant relationships work better in improving the process performance during initial and secondary stages, respectively. Moreover, continuous versus total initial addition of H₂O₂ were compared and the first one showed better performance, representing differences in energy costs up to 21 %. Finally, two strategies for the real-time control of the O₃-recalcitrant MPs fate were tested, one based on the R_OHO3 concept and the other on UVA₂₅₄ monitoring. Both resulted in accurate predictions (R² > 0.96) for different compounds, effluents and processes.