Optimization of continuous reactor at pilot scale for olive-oil mill wastewater treatment by Fenton-like process

Reclamation of olive-oil mill wastewater (OMW) from two-phase extraction procedure was carried out in a continuous stirred tank reactor (CSTR) at a pilot plant scale by Fenton-like process. The effect of operating conditions such as pH, space–time, H2O2 and Fe(III) doses, as well as [FeCl3]/H2O2] ratio on the efficacy of Fenton’s process was investigated. It is demonstrated that Fenton’s process can effectively degrade organic matter in OMW. In the start-up stage, Fenton reaction reached steady state within 3 h. Oxidation of organic materials in OMW was pH dependent and the optimal pH was found to be 3. The optimum [FeCl3]/[H2O2] ratio was in the range 0.026–0.058 w/w, with Fe(III) concentration between 0.35 and 0.40 g dm−3. The final values of COD and total phenols at the outlet of the pilot plant were close to 129 mg O2 L−1 ([COD]initial = 4017 mg O2 dm−3), and 0.5 mg dm−3 ([total phenols]initial = 66.2 mg dm−3), respectively. Finally, the produced water can be used for irrigation or discharged directly into the municipal wastewater system for ulterior tertiary treatment.

► OMW reclamation from two-phase process was carried out in a CSTR by Fenton system. ► The optimum [FeCl3]/[H2O2] ratio was in the range 0.026–0.058 w/w. ► [Fe3+] = 0.35–0.40 g dm−3 is necessary to achieve a higher COD removal (>97%). ► Water treated can be used for irrigation or discharged into urban wastewater system.