Advanced oxidation process–biological system for wastewater containing a recalcitrant pollutant

Abstract

Two advanced oxidation processes (AOPs), ozonation and photo-Fenton, combined with a pilot aerobic biological reactor at field scale were employed for the treatment of industrial non-biodegradable saline wastewater (TOC around 200 mg L−1) containing a biorecalcitrant compound, α-methylphenylglycine (MPG), at a concentration of 500 mg L−1. Ozonation experiments were performed in a 50-L reactor with constant inlet ozone of 21.9 g m−3. Solar photo-Fenton tests were carried out in a 75-L pilot plant made up of four compound parabolic collector (CPC) units. The catalyst concentration employed in this system was 20 mg L−1 of Fe2 +  and the H2O2 concentration was kept in the range of 200–500 mg L−1. Complete degradation of MPG was attained after 1,020 min of ozone treatment, while only 195 min were required for photo-Fenton. Samples from different stages of both AOPs were taken for Zahn–Wellens biocompatibility tests. Biodegradability enhancement of the industrial saline wastewater was confirmed (>70% biodegradability). Biodegradable compounds generated during the preliminary oxidative processes were biologically mineralised in a 170-L aerobic immobilised biomass reactor (IBR). The global efficiency of both AOP/biological combined systems was 90% removal of an initial TOC of over 500 mg L−1.