Micro-pollutants, Oxidants, Catalysts and the Water Matrix: A Harmonic Quartet or the War of the Roses?

Advanced oxidation processes (AOPs, e.g. heterogeneous and homogeneous photocatalysis, electrochemical oxidation, ozonation, ultrasound irradiation, Fenton and alike reactions, and many more) have been investigated for the treatment of emerging pollutants over the past 20 years (Klavarioti et al., 2009). In particular, the occurrence of persistence micro-pollutants in various water matrices, such as pharmaceuticals and personal care products, raises serious environmental concerns since these xenobiotics can re-enter the water cycle, i.e. escaping intact from the conventional wastewater treatment plants and finally ending up in surface and ground waters (Verlicchi et al., 2012). AOPs can effectively degrade organic pollutants typically found in environmental matrices (secondary treated effluents, surface waters, ground waters) at concentrations ranging from the ng/L to low mg/L level. This said, the specific treatment cost (i.e. the cost per unit mass of removed pollutant and/or per unit volume of effluent), as well as the environmental footprint are generally high; both are usually related to the treatment performance, which, in turn, depends on the specific treatment conditions and the quality of the water matrix.