Pre-treatment of olive mill wastewater by chitosan coagulation and advanced oxidation processes

In the present work the combined pre-treatment of actual olive mill wastewaters by coagulation with natural organic coagulant, such as chitosan, and the advanced oxidation processes, specifically photocatalysis (PC), Fenton (F) and photo-Fenton (PF), was investigated. The optimum removal of total suspended solids (TSSs, 81%) by chitosan coagulation was achieved at actual pH (4.3) for 400 mg L−1 coagulant dose. The maximum organic matter removals by F (85%) and PF (95%) processes were achieved after 2.0 and 1.0 h, respectively by using 15,000/1852 (w/w) ratio of H2O2/FeSO4. On the opposite, in PC experiments, after an initial decrease in the early minutes of the treatment, a subsequent increase versus irradiation time was observed for both UV absorbance at 280 nm and chemical oxygen demand (COD); probably a partial oxidation made some organics detectable only after treatment.