Produced water (PW) from oil and gas production contains variable constituents which 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 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 US. 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 polyethylene glycols (PEGs) at total dissolved solids (TDS) concentration of 40 g/L but only 58% removal at 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.

Iodidimonasis a genus recently described in bioreactors treating oil and gas produced water and in iodide rich brines. Besides the ability to oxidize iodine, little is known about the metabolic capabilities that enableIodidimonassp. to occupy this unique ecological niche. We isolated, characterized, and sequenced three strains belonging to theIodidimonasgenus from the sludge of a membrane bioreactor treating produced water. We describe the genomic features of these isolates and compare them with the only other four isolate genomes reported from this genus, as well as a metagenome-assembled genome from the source bioreactor. To survive in the produced water,Iodidimonasisolates had several genes associated with mitigating salinity, heavy metal and organic compound stress. While the isolates could utilize a wide variety of carbon substrates, they failed to degrade aliphatic or aromatic hydrocarbons, consistent with the lack of genes associated with common hydrocarbon degradation pathways in their genomes. We hypothesize these microbes may lead a scavenging lifestyle in the bioreactor and similar iodide-rich brines.ImportanceOccupying a niche habitat and having few representative isolates, genusIodidimonasis a relatively understudied Alphaproteobacterial group. This genus has garnered attention due to its ability to corrode pipes in iodine production facilities and generate iodinated organic compounds during treatment of oil and gas produced water. The iodinated organic compounds are likely to be carcinogenic and may pose issues with recycling the treated water. Hence, detailed characterization of the metabolic potential of these isolates is not only of economic importance, but also sheds light on adaptation of this microbe to its environmental niche.