Critical evaluation of hypersaline produced water treatment and reuse using innovative membrane-based desalination technologies

Produced water (PW) from oil and gas operations contains complex salts, metals, hydrocarbons, and radionuclides that pose challenges for treatment and reuse. This study evaluated water quality and treatment performance of three pilot-scale multistage membrane treatment trains employing different nanofiltration and reverse osmosis configurations in the Permian Basin. Approximately 470 analytes were measured, of which 105 were detected in feeds, 70 in permeates, and 43 in post-treated desalinated PW. Despite variable feed salinity of 26.1–116 g/L, the systems removed ~99% salts, 56.3-99.4% (average 91.6%) total organic carbon, and 95–>99.9% radionuclides. Membrane rejection was strongest for multivalent ions and transition metals, while monovalent halides and low-molecular-weight neutral oxygenates compounds showed more variable removal. Post-treatment further reduced residual salinity, organics, ammonia, boron, and radiological risk in permeates to meet the current water quality criteria for fit-for-purpose applications. Membrane rejection mechanisms for inorganic and organic constituents in hypersaline PW were investigated and a tiered monitoring framework using surrogate parameters and indicator compounds was developed to support process control, treatment evaluation, and risk assessment. Overall, this study addresses key knowledge gaps in field-scale evaluation of membrane-based PW treatment and provides science-based evidence to support treatment design, monitoring strategies, and fit-for-purpose reuse.