Unfolding the action mode of light and homogeneous vs. heterogeneous photo-Fenton in bacteria disinfection and concurrent elimination of micropollutants in urban wastewater, mediated by iron oxides in Raceway Pond Reactors

In this work, iron oxides have been proposed as low-cost heterogeneous photo-Fenton catalysts for the simultaneous disinfection and reduction of microcontaminant load from urban wastewater in raceway pond reactors at near-neutral pH. The objective was not finding the best operating conditions but understanding the mechanisms of FeOx driven disinfection and the implications presented by the matrix constituents, namely organic matter and (bi)carbonates, as well as the possibility to apply this system after different secondary treatments in continuous flow mode. Notable bacterial inactivations were obtained in both batch and continuous flow modes by any iron oxide used, with total inactivation (5 log reduction) in the case of Hematite. The heterogeneous photo-Fenton process was proven to be the driving bacterial inactivation force in urban wastewaters. Additionally, monitoring the elimination of 25 emerging contaminants in the secondary effluents was performed. The operation mode (batch-continuous) was assessed, attaining a minimum of 35% micropollutant removal.