Oil Produced Water treatment for oil removal by an integration of coalescer bed and microfiltration membrane processes

• The total efficiency was 93.0–100%, with O&G in permeate=0.1–14.8 mg L−1.
• The permeate quality results were good for disposal, injection or reuse purposes.
• The final efficiency varied in three stages: descendent, ascendent and constant.
• Jp was higher at higher Δpm=>operation conditions outside the liming flux region.
• Flux decline was higher when velocity, O&G in the feed stream or WRR were higher.

This article presents an experimental investigation of Oil Produced Water (OPW) treatment for oil removal by integration of two processes: coalescer bed and microfiltration membranes (MFs). The objective is to overcome operational problems and limitations that both the processes present when used separately.The coalescer bed was formed by cationic exchange resins, working in upflow condition. The MF unit used a polyetherimide hollow fiber submerged module with a permeation area of 0.5 m2.The investigations were conducted by using synthetic OPW with oil concentrations of 200–400 mg L−1 and oil droplet diameters from 3 to 8 μm. In the coalescer bed the fluid velocity ranged from 4.4 to 17.4 m h−1 and the bed height was 5 cm. The water recovery rate in MF was kept in the range of 0.75–0.90 by using a transmembrane pressure varying from −12 to −30 kPa.The coalecer bed worked in steady state conditions, reaching an efficiency of 35–52%. The overall efficiency of the integrated process reached 93–100% and the oil contents ranged from 0.1 to 14.8 mg L−1. These results indicate that the effluent in the integrated process has quality not only for injection, but also for reuse purposes.