Anaerobic digestion experiments of olive mill wastewater (OMWW) without pretreatment were carried out and signs
ofinhibition in the biological process were observed after a time equalto 1.5 times the Hydraulic Residence Time (HRT)
due to the presence of a high inhibitors concentration in OMWW. Based on these findings, OMWW was subjected to
an aerobic pretreatment in order to reduce the concentration of phenolic compounds and decrease Total Chemical
Oxygen Demand (TCOD), achieving a reduction of 78% and 90% of the initial polyphenols concentration and 18% and
21% TCOD reduction when the substrate was aerated for 5 and 7 days respectively.
Finally, anaerobic digestion experiments using OMWW aerated for 5 and 7 days as substrate were conducted to
determine the influence of aeration time on methane yields and TCOD reduction. The results yield 5 days as the
aeration time that achieves best results, given that this stabilizes the anaerobic process, can reduce the TCOD by 65%
and generates almost 0.39m3 methane/kg removed TCOD.
Anaerobic digestion of OMWW will be economically feasible if the waste is pretreated by aerobic digestion, since
the period of return of investment obtained under these conditions does not exceed 6 years.
© 2014 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers.
Keywords: Aerobic pretreatment; Anaerobic digestion; Olive mill wastewater; Economic viability; Polyphenols inhibition;
Methane yield