Kinetic Evaluation of a Field-Scale Activated Sludge System for Removing Petroleum Hydrocarbons from Oilfield-Produced Water

Produced water is the single largest volume of wastewater generated by the oil and gas industry. Toxic petroleum hydrocarbons found in oilfield-produced waters have increasingly become the major environmental problem facing the U.S. and world oil and gas industry. Uncontrolled releases to the environment using outdated and inefficient technological control systems and methods have continually put surface and ground water environments at risk. In turn, this has placed the oil and gas industries with increasing environmental regulatory compliance costs. With the decline in oil and natural gas prices and the introduction of more stringent produced water surface discharge permit actions, many of these wells are nearing their economic limit. These low-volume marginal wells are being plugged and abandoned because the production, maintenance, treatment, and disposal costs are higher than the selling price. Therefore, in an effort to keep many of our nation's mature oil and gas fields productive, alternative technologies must be evaluated. This research project provided a comprehensive treatment of produced waters using an activated sludge system. The kinetic coefficients determined resulted in a total petroleum hydrocarbon removal efficiency of 99% at a produced water flow rate of 1890 L/day, and a mean cell residence time of 20 days. Kinetic coefficients were determined to be 0.69 (mg/MLSS)/mg total n-alkanes (TNA) and 0.01, 0.44, 2.00, and 0.27 day−1 for Y, kd, k, Ks, and μmax, respectively. © American Institute of Chemical Engineers Environ Prog, 2004