Abstract

The goal of this study was to develop a mesophilic anaerobic co-digestion (co-AD) process of olive mill wastewater (OMW) and sewage sludge (SwS) from municipal wastewater treatment. Different volumetric OMW:SwS ratios up to 100% OMW were fed in continuous 1.7-L bioreactors. The reactors fed with raw OMW (rOMW) performed better than those fed with OMW dephenolized by adsorption (dOMW). At a 23-day hydraulic retention time (HRT) the best performances were obtained in the reactor fed with 25% rOMW, with a 105% increase in methane yield in comparison to the 100% SwS test. At a 40-day HRT, the reactor fed with 40% rOMW attained a 268 NLCH4/kgVS methane yield (144% increase in comparison to 100% SwS). These results prove the feasibility of co-digesting with SwS the entire OMW production in regions characterized by intense olive oil production, with a strong increase in methane production.