New approaches to solar Advanced Oxidation Processes for elimination of priority substances based on electrooxidation and ozonation at pilot plant scale

Abstract The main objective of this work is to compare various Advanced Oxidation Processes based on solar photo-Fenton at circumneutral pH (by adding EDDS as iron complexing agent), such as solar photo-electro-Fenton process and solar ozonation in combination with Fenton like processes (O 3 /Fe 2+ /H 2 O 2 , O 3 /Fe 3+ /H 2 O 2 and Solar/Fe 3+ /O 3 /H 2 O 2 ), for the elimination of four microcontaminants (MCs) (Terbutryn, chlorfenvinphos, pentachlorophenol and diclofenac) at 200 μg/L each and in different water matrices. These compounds were selected as Priority Substances listed in European Commission directives (2013/39/EC and 2008/105/EC Directives). Research was carried out at pilot plant scale in a 30 L electrochemical system (cells made by an anode of boron-doped diamond thin film on a niobium mesh (Nb-BDD) and a carbon-polytetrafluoroethylene (PTFE) GDE as the cathode), a 20 L ozone reactor and three different solar photoreactors (39 L, 45 L and 120 L) based on compound parabolic collectors (CPC) and connected to the non-solar oxidation systems. Results showed successful elimination of at least 80% of MCs for all the technologies tested. However, solar photo-Fenton at circumneutral pH showed better performance than solar photo-electro-Fenton and even electro-Fenton processes. In addition, the combination of ozone with solar radiation showed promising results since almost a complete elimination of MCs was attained with a significant lower ozone consumption than when applying ozone in the dark (with or without the assistance of Fenton´s reagent).