Sustainable management of produced water: Microbial ecology, bioremediation, and resource recovery

Oil and gas extraction generates more than 1 trillion gallons of produced water (PW) annually in the United States alone. PW complex composition, including high salinity, diverse organic pollutants, and elevated concentrations of heavy metals, presents significant environmental and operational challenges. Traditionally viewed as a disposal burden, PW is increasingly recognized as a potential resource, particularly with increasing freshwater scarcity and growing demand for critical minerals. This dissertation advances a circular bioeconomy framework for PW management by integrating microbial ecology and physiology, culture-based approaches, -omics techniques, and membrane processes to enable both bioremediation and recovery of valuable elements. A multi-regional microbiome survey of PW from Oklahoma, New Mexico, and Wyoming revealed that microbial community structure varies widely across reservoirs and is shaped more by geochemical parameters such as salinity, sulfate, depth, and pH than by geography. Building on this ecological insight, two halophilic bacteria were isolated and characterized, including Modicisalibacter sp. strain Wilcox, which can degrade aliphatic and aromatic hydrocarbons, detoxify and remove heavy metals under hypersaline conditions. This strain demonstrated exceptional performance across raw PW matrices with varying geochemistry. Further, a hybrid treatment train was developed, combining microbial bioremediation with nanofiltration (NF) and reverse osmosis (RO). For non-permissible samples, low-cost conditioning strategies such as salinity adjustment, dilution and blending allowed alignment of PW chemistry with microbial physiology, enabling complete BTEX removal and desalination suitable for beneficial reuse in low-salinity samples. For hypersaline feeds, coupling NF with membrane distillation (MD) is proposed to overcome osmotic limitations of RO. Finally, the project evaluated the tolerance and potential of strain Wilcox for biorecovery of lithium (Li) and lanthanum (La) in PW. Recovery efficiencies were controlled by pH and contact time, with Li and La following distinct uptake mechanisms. These findings support a tunable strategy for optimizing microbial recovery of critical minerals. Together, this work presents a scalable, mechanistic approach to PW management. By integrating microbial bioremediation, critical mineral recovery, and membrane desalination, this work demonstrated the potential to transform PW from a waste liability into a valuable resource, advancing the transition toward a sustainable, circular economy in the energy sector.