REIMAGINING PRODUCED WATER AS A RESOURCE THROUGH BIOREMEDIATION

Oil and natural gas production operations generate large quantities of polluted wastewater known as produced water (PW), with approximately 21 billion barrels of PW generated annually in the United States alone. With population explosion, rising energy demand, water scarcity episodes as well as recent drought, the need to treat PW for beneficial re-use has become increasingly important. However, due of its toxic and carcinogenic constituents (hydrocarbons, phenols, benzoates, heavy metals, radionuclides) and high salinity, it is difficult to treat PW cost-effectively using traditional technologies. Hence, the primary goal of our research is to study microbes that can survive in PW and explore their potential for its cleanup. We have enriched and isolated several hydrocarbon-degrading halophilic microorganisms for this purpose, including Modicisalibacter sp. strain Wilcox and Arhodomonas recens which were isolated from PW from Wilcox formation in Oklahoma and Kuwait brine respectively. We set up microcosms containing mineral salts medium and in the presence of varied salt concentration to study their salt tolerance. We studied their ability to degrade different hydrocarbons and tolerate different heavy metals that are commonly found in PW at 2.5 M NaCl (14.5% salinity). Results showed that these bacteria can degrade a variety of aliphatic and aromatic compounds typically found in PW at salinities as high as 4.5 M NaCl (>26% salinity). Genome analysis predicted the presence of a repository of hydrocarbon degrading genes and genes for heavy metal resistance. Experiments show that strain Wilcox can tolerate high levels of several heavy metals (single or multi-metals) including Arsenic (100 mM), Manganese (100 mM), Cadmium (20 mM), Zinc (7 mM), and Lead (5 mM). Strain Wilcox can also remove metals like Lead, Zinc, Chromium, and Selenium from samples through bioaccumulation and biosorption mechanisms. These findings suggest that these bacteria have the potential to cleanup PW, and strain Wilcox could potentially be used in the bioextraction of valuable heavy metals from PW and other industrial wastewaters. Treated PW can be reused for fracking, nuclear plants cooling, and irrigation of marginal crops like switchgrass for biofuel production etc.