Oil skimming followed by coagulation/flocculation processes for oilfield produced water treatment and zero liquid discharge system application

The study focused on the treatment of real oilfield produced water from the East Baghdad field affiliated to the Midland Oil Company (Iraq) using an oil skimming process followed by a coagulation/flocculation process for zero liquid discharge system applications. Belt type oil skimmer was utilized for evaluating the process efficiency with various operating conditions such as temperature (17-40 °C) and time (0.5-2.5 hr.). Polyaluminum chloride (PAC) coagulant and polyacrylamide (PAM) flocculant was used to investigate the performance of the coagulation/flocculation process with PAC dosage (5-90 ppm) and pH (5-10) as operating conditions. In the skimming process, the oil content, COD, turbidity, and TSS decreased with an increase in temperature and time. The best temperature and time for oil skimming are 40 °C and 2.5 hr. which gives 95.8%, 94.9%, 31.5%, and 33.2% removal for oil content, COD, turbidity, and TSS respectively. In the coagulation/flocculation process, the optimum PAC dosage and pH are 55 mg/l and 6.4 which gives 100%, 96.5%, and 97.7% removal for oil content, turbidity, and TSS respectively.