Anaerobic biodegradation of olive mill wastewater: batch and UASB reactor performance

Batch biodegradability tests were carried out to determine the digestibility of olive mill waste water (OMW), the COD removal and potential methane (CH4) yield. The tests were prepared with anaerobic sludge and different volumes of OMW (0 ml, 10 ml unfiltered, 20 ml unfiltered and 10 ml of filtered sample). The biodegradability of the mixtures based on the gas production rate was 43, 58, 53, and 59%, respectively. Anaerobic treatment of OMW was also investigated in an up flow anaerobic sludge blanket (UASB) reactor at organic loading rates (OLRs) between 1.6 and 8 kg COD m−3 d−1 at a hydraulic retention time of 15 h. The results showed stable COD removal efficiencies (∼85%) for OLRs up to 7.6 kg m−3 d−1. Gradual improvement in the biogas production rate was observed with higher OLRs. The highest CH4 yield was about 0.37 L CH4 g−1 of COD removed.