Lawrence Berkeley National Laboratory

Produced water (PW) from oil and gas production contains variable constituents that are difficult to remove with conventional treatment processes. The focus of this study was to explore the long-term performance of a membrane bioreactor (MBR) for the removal of organic constituents from PW and how performance and microbial community composition are affected by progressively increasing salinity and introduction of PW from different shale basins around the United States. Dissolved organic carbon removal from the PW remained consistent throughout the study, averaging 86% from the Denver-Julesburg basin PW and 66% removal from the Permian basin PW. Surfactant removal was less consistent, showing 87% removal of poly(ethylene glycols) (PEGs) at a total dissolved solid (TDS) concentration of 40 g/L but only 58% removal at a TDS concentration of 100 g/L. Diversity in the microbial community decreased during reactor establishment but increased at TDS concentrations above 80 g/L. The results of this study suggest that MBRs can be effective PW pretreatment processes even at high salinities.