Oilfield wastewater treatment by combined microfiltration and biological processes

This work deals with the treatment of offshore oilfield wastewater from the Campos Basin (Rio de Janeiro State, Brazil). After coarse filtration, this high saline wastewater was microfiltrated through mixed cellulose ester (M CE) membranes, resulting in average removals of COD, TOC, O&G and phenols o f 35%, 25%, 92% and 35%, respectively. The permeate effluent was fed into a 1-L air-lift reactor containing polystyrene particles of 2 mm diameter, us ed as support material. This reactor was operated for 210 days, at three hy draulic retention times (HRT): 48, 24 and 12 h. Even when operated at the l owest HRT (12 h), removal efficiencies of 65% COD, 80% TOC, 65% phenols and 40% ammonium were attained. The final effluent presented COD and TOC value s of 230 and 55 mg/L, respectively. Results obtained by gas chromatography analyses and toxicity tests with Artemia salina showed that a significant i mprovement in the effluent's quality was achieved after treatment by the co mbined (microfiltration/biological) process. (C) 2001 Elsevier Science Ltd. All rights reserved.