Application of biological oxidation and solar driven advanced oxidation processes to remediation of winery wastewater

Biological oxidation and solar driven advanced oxidation processes (AOPs) applied as a single stages were tested at a pilot plant equipped with an immobilized biological reactor (IBR) and a photocatalytic system with compound parabolic collectors (CPCs) for the remediation of a winery wastewater (DOCaverage = 882 mg L−1; pH 4.1). Due to the variable nature of winery wastewater composition and quantity, the application of AOPs as a single or as preliminary stage can be an effective alternative to only conventional biological treatment. Regarding the AOPs systems tested (TiO2/H2O2/UV and Fe2+/H2O2/UV), the solar photo-Fenton reaction (optimized at pH 2.8 and 55 mg Fe2+ L−1) showed the highest efficiency, being necessary an UV dose of 100 kJUV L−1 and 338 mM H2O2 (15 mg H2O2 mg C−1) to achieve a COD value lower than 150 mg O2 L−1, which is agreement with the discharge limits into receiving waters imposed by the Portuguese Legislation (Decree-law n° 236/98). To achieve the same COD target value using only the IBR system or the combination of solar-photo-Fenton (22 kJUV L−1; 80 mM H2O2 consumed) and biological systems, approximately 10 and 6 days (time necessary for the biological oxidation) are required. The efficiency of the AOPs in the treatment of simulated and real winery wastewaters was also compared.