Biological treatment of high salinity and low pH produced water in oilfield with immobilized cells of P. aeruginosa NY3 in a pilot-scale.

• Immobilized P. aeruginosa NY3 removed oil and SS in real PW with high removal capacity. • The function of the used biofilms of P. aeruginosa NY3 could be recovered. • Recovered biofilms of P. aeruginosa NY3 possess higher oil removal ability than the original ones. Produced water (PW) in oilfield, as the largest waste streams in the oil and gas production, has posed a huge threat to the ecosystem. In this work, an environmentally friendly and recyclable biofilms have been developed for treating PW. We discovered that the cells of P. aeruginosa NY3 could be easily immobilized on the surface of polyurethane foam (PUF). Removal efficiency of oil and suspended solids (SS) by immobilized P. aeruginosa NY3 was keeping above 80% and 76% both in a laboratory scale and a pilot scale under suitable pH. Low pH and high value of SS had negative effect on the degradation of oil and SS by P. aeruginosa NY3. Recovery test showed that, the activity of biofilms P. aeruginosa NY3 after running in a pilot scale could be recovered in 5 days. Removal ability of oil in the real PW by the recovered biofilms of P. aeruginosa NY3 was even higher than that of the freshly prepared biofilms. These results indicated that, with a simple pH adjustment, immobilized P. aeruginosa NY3 could be recycled for removing oil and SS in the raw PW resulted from oil production. [ABSTRACT FROM AUTHOR]