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.