The water that exists in oil and gas (O&G) reservoirs and is brought to the surface during resource extraction, called produced water (PW), is the largest volume waste stream associated with O&G extraction, with over 3 trillion liters produced annually in the U.S. Because of its origins in O&G reservoirs, PW contains elevated levels of toxic petroleum hydrocarbons, salts, heavy metals, naturally occurring radioactive materials and any remaining drilling, stimulation or well maintenance chemicals. Many water-scarce western states can take advantage of the National Pollutant Discharge Elimination System (NPDES) which permits PW to be released to the environment for agricultural uses if it is “of good enough quality.“ Some states, including California, also permit releases of this water, after minimal treatment, for use in agriculture. The requirements for releasing this water are not clearly defined through permissible concentrations, however, and the locally and temporally varying composition of PW discharges is largely unknown.
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Produced water is a byproduct of the oil and gas industry. Common management strategies include deep well injection and evaporation ponds, which increase seismicity, groundwater contamination, and volatiles into the atmosphere. Projects in the Borch group look into treatment options, reuse potential, and crop health. High resolution mass spectrometry, metabolomics, technoeconomic analyses, toxicity studies and greenhouse studies have allowed in depth studies to understand the impact of produced water reuse.
One study looked at a treatment train including reverse osmosis and nanofiltration as potential treatment options for unconventional produced water. In this study a wide variety of organics and inorganics were analyzed with high resolution mass spectrometry techniques. Then this was compared with acute toxicity tests to see the reduction the treatment train has on toxicity and the produced water constituents.
From there, a greenhouse study was done to look into conventional produced water, a typically higher quality wastewater. Irrigation was done with untreated conventional produced water. Soil and crop analyses were done to understand the impact conventional produced water has on crops after one growing season. Analyses included metabolomics, metal analysis, organic analysis, agronomic trait measurements, soil heath measurements, and soil microbial and metagenome analysis.
Due to the success of a greenhouse study, this prompted a project furthering conventional produced water analysis. Numerous wells in eastern Colorado were examined for a larger sample size. In this study, the water quality was examined using high resolution mass spectrometry. Then technoeconomic analysis and acute toxicity analyses were employed to elucidate the impact conventional produced water could have on various end users, like crop and cattle irrigation.
A larger scaled field study was started in Orla, Texas to investigate the use of produced water as an irrigation water, with onsite treatment. Soil heath and water quality parameters are being measured in this on-going project.
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Advancing sustainable water use across the agricultural life cycle in the USA