Biological and photo-fenton treatment of olive oil mill wastewater

Olive oil wastewaters (OOMW) are dark effluents which pose serious environmental problems. The aim of this work was to apply biological treatment with Pleurotus spp., and chemical treatment, through oxidation by Photo-Fenton, to OOMW. The biological treatment was not very efficient in colour reduction. In 25% OOMW dilution treated with P. sajor caju or P. ostreatus, high percentages of colour reduction (460 nm) were recorded after 6 days (70.3 and 54.7%) but, thereafter, great oscillations were observed. In terms of pH, a similar profile was recorded in 25-50% dilutions treated either with P. sajor caju or P. ostreatus. Both species grew in OOMW and were responsible for COD reduction, which was greater in the OOMW treated with P. sajor caju. The Photo-Fenton reaction was very efficient (> 90%) in colour reduction. The best combination of H2O2/Fe concentrations was found to be 6 ml of H2O2 (70%) plus 1 ml of FeSO4 (0,5M). In terms of toxicity reduction tested for Daphnia longispina, the biological and chemical treatments also had a different efficiency. Further research will be carried out to assess the combined application of both treatments, and it’s effectiveness in the improvement of the main concerning properties of this industrial effluent.