Photo-Fenton like process as polishing step of biologically co-treated olive mill wastewater for phenols removal

In this study, UVC or sunlight assisted photo-Fenton like process (PFI) using iron(III) iminodisuccinate (Fe-IDS) as catalyst was investigated for the first time as post-treatment method of a Moving Bed Biofilm Reactor (MBBR) for the treatment of olive mill wastewater (OMW). Hydraulic retention time for the MBBR process was 24 h, while the treatment time for the PFI process was 3 h under UVC or solar light irradiation. Before the MBBR treatment, OMW was centrifuged and mixed with synthetic urban wastewater to simulate conditions in a real wastewater treatment plant (WWTP). The MBBR was highly effective in reducing Biological Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) (97 and 91%, respectively), but less effective (57%) in the removal of total phenols (TPHs). PFI was optimized for TPHs removal through response surface methodology. UVC driven PFI allowed to reach higher TPHs removal than sunlight driven PFI. Fe (III) dosage was set at 2 mg/L while optimum H2O2 dosage resulted to be 144 mg/L. In these conditions, the UVC driven process allowed to obtain a TPHs removal of 99%, reaching a final TPHs concentration of 0.07 ± 0.01 mg/L.