Sequential anaerobic/aerobic biological treatment of olive mill wastewater and municipal wastewater

Abstract

AbstractThis work investigated the efficiency of the combined anaerobic/aerobic biological co‐treatment of olive mill wastewater and primary municipal wastewater. A laboratory‐scale (6.5 L) upflow anaerobic sludge bed reactor received a mixture of olive mill wastewater and primary municipal wastewater at a loading rate ranging between 3 and 7 kg chemical oxygen demand (COD) m−3 day−1. The input COD concentration ranged between 1800 and 4400 mg L−1. The anaerobic reactor was operated at mesophilic conditions (35 °C). The effluent organic load was between 400 and 600 mg COD L−1, while the suspended solids removal efficiency varied between 75 and 95%. Average biogas production ranged between 3 and 4 L g−1 COD removed. The anaerobic reactor effluent was further treated in a laboratory‐scale activated sludge treatment plant. Aerobic treatment reduced the organic load even further to 85–175 mg COD L−1. However, the final effluent still retained a significant level of colour. Removal of colour was possible by ozonation or coagulation. Finally, the treated effluent was non‐ecotoxic, as indicated by the Daphnia magna toxicity test. This treatment method showed that it is feasible to treat olive mill wastewater in a municipal wastewater treatment plant by means of a high‐rate anaerobic reactor located between the primary clarifier and the aeration tank. Copyright © 2006 Society of Chemical Industry