Anaerobic digestion challenge of raw olive mill wastewater

Abstract: Olive mill wastewater (OMW) was digested in its original composition (100% v/v) in an anaerobic hybrid. High concentrations (54–55kg COD m−3), acid pH (5.0) and lack of alkalinity and nitrogen are some OMW adverse characteristics. Loads of 8kg COD m−3 d−1 provided 3.7–3.8m3 biogas m−3 d−1 (63–64% CH4) and 81–82% COD removal. An effluent with basic pH (8.1) and high alkalinity was obtained. A good performance was also observed with weekly load shocks (2.7–4.1, 8.4–10.4kg COD m−3 d−1) by introducing piggery effluent and OMW alternately. Biogas of 3.0–3.4m3 m−3 d−1 (63–69% CH4) was reached. Developed biomass (350days) was neither affected by raw OMW nor by organic shocks. Through the effluents complementarity concept, a stable process able of degrading the original OMW alone was obtained. Unlike what is referred, OMW is an energy resource through anaerobiosis without additional expenses to correct it or decrease its concentration/toxicity. [Copyright &y& Elsevier]