Solar treatment of cork boiling and bleaching wastewaters in a pilot plant

This paper reports on cork boiling and bleaching wastewaters treatment by solar photocatalytic processes, TiO2/UV and Fe2+/H2O2/UV (TiO2-only for bleaching wastewater), in a pilot plant with compound parabolic collectors. The photo-Fenton reaction (k = 0.12 L/kJUV, r0 = 59.4 mg/kJUV) is much more efficient that TiO2 photocatalysis and TiO2 + S2O82− (k = 0.0024 L/kJUV, r0 = 1.36 mg/kJUV), leading to 94% mineralization of the bleaching wastewater after 31.5 kJUV/L, consuming 77.1 mM of H2O2 (3.0 mmol/kJUV) and using 20 mg/L of iron. For the cork boiling wastewater, after a slow initial reaction rate, the DOC degradation curve shows a first-order kinetics behaviour (k = 0.015 L/kJUV, r0 = 20.8 mg/kJUV) until 173 kJUV/L (≈300 mg C/L). According to the average oxidation state (AOS), toxicity profiles, respirometry and kinetic results obtained in two solar CPCs plants, the optimal energy dose estimated for phototreatment to reach a biodegradable effluent is 15 kJUV/L and 114 kJUV/L, consuming 33 mM and 151 mM of H2OT:/PGN/ELSEVIER/WR/web/00007490/2, achieving almost 49% and 48% mineralization of the wastewaters, respectively for the cork bleaching and boiling wastewaters.