Improving Anaerobic Co-digestion of Sewage Sludge with Thermal Dried Olive Mill Wastewater

Anaerobic co-digestion of olive mill wastewater (OMW) and sewage sludge (SS) is a promising technique in terms of biogas production and quality. An OMW mixture was subjected to pre-treatment (thermal drying), which can reduce the total COD by 72.8% of 10% OMW mixture. OMW mixtures at concentrations of 2, 5, and 10% were tested. OMW addition can improve biogas production if the mixture exceeds 5% (v/v) concentration in the feed. The digestion of SS produced 31Nm(3)/Kgvs and with an addition of OMW increased biogas production in the range of 0.337-0.42Nm(3)/Kgvs (2-10%v/v in the feed), where the best addition was 10% with 0.42Nm(3)/Kgvs of biogas. VS removal was estimated, it was over 55.2% of 10% OMW about 2.2 times of digestion of SS. Also, COD removal efficiency exceeded 72.2% of 10% OMW which is 1.2 times of 100% SS.