Our Water Matters: Produced water

Defined by law as “fluid oil and gas waste,” produced water is “produced” in conjunction with oil, gas, and “flowback” when operators pressure-inject massive amounts of water laced with chemicals and sand deep into the ground to crack open or “fracture” shale and release hydrocarbons. According to the Groundwater Protection Council (GWPC), “Produced water may contain salts (total dissolved solids), organic and inorganic compounds, naturally-occurring radioactive material, chemical additives, and transformational byproducts, among others.” The GWPC estimates that the greater Permian Basin of western Texas and southern New Mexico generated about 846,829 acre-feet of produced water in 2023. The vast majority of this produced water is disposed of by reinjecting it into deep formations via “saltwater disposal” wells.

The staggering volumes of wastewater generated by oil and gas operations have led many to view produced water as a potential “new” source of water to help cover the enormous shortages projected to afflict the region in coming decades. Toward this end, the Texas Produced Water Consortium was established for “the purpose of bringing together information and resources to study the economics and technologies related to beneficial uses of produced water, including environmental and public health considerations.” According to its 2022 report, the Texas Consortium estimates that the “average treated produced water volume available for beneficial use over the next 38 years” could be between 256,000 and 511,000 acre-feet per year. “Put in perspective,” the report continues, “the 2022 State Water Plan for Water Planning Region F (covering most of the Permian) indicates an average annual need (potential shortage) of 80,751 ac-ft/year over the next 50 years.” 

The situation in New Mexico is similar. According to the New Mexico Produced Water Research Consortium, that state’s “oil and gas industry generated approximately 60 billion gallons of produced water, over 160 million gallons per day, equal to New Mexico’s total daily municipal water consumption.” With so much of this water being produced every year throughout the region, the question becomes: Is there enough known about potentially toxic chemicals present in produced water, and do technologies exist that can treat produced water to an adequate quality for other beneficial uses?

Dan Mueller is an engineer with the Environmental Defense Fund who specializes in fresh water supply, water quality, and treatment and beneficial reuse of impacted waters. As a member of the New Mexico Produced Water Research Consortium since its inception in 2019 and the Texas Produced Water Consortium since it was formed in 2021, he has been working to fill the knowledge gaps around the potential beneficial use of produced water for industrial processes, irrigation, livestock watering, discharge to surface waters, and aquifer storage and recovery. “There are significant and critical unknowns around the chemical and toxicological characterization of produced water and the efficacy and reliability of robust treatment processes to properly treat produced water to a quality appropriate for reuse that is protective of human health and the environment,” according to Mueller. “It is important that beneficial reuse of produced water or other options that include intentional release of what in essence is an industrial wastewater effluent does not inadvertently create more problems than it solves.” 

Treatment to an adequate quality for beneficial use is difficult because “produced water (particularly in the Permian Basin) has elevated total dissolved solids (TDS) many times greater than seawater, making the desalination of produced water challenging.” Mueller emphasized that “desalination technology for the most part was developed around treating brackish or saline waters (like seawater) and is much more expensive than other disposal options.” Other management challenges involve “difficult-to-treat and potentially toxic constituents of produced water, including inorganics, organics, and radionuclides” also known as “constituents of concern,” or CoCs, that are generated throughout the life of an oil and gas well. CoCs “vary both geographically and over time,” according to Mueller, “adding to the challenges in the design and operation of robust treatment processes.”

Mueller also pointed to the lack of “approved analytical methods … for approximately ¾ of the constituents potentially present in produced water” and verification methods to confirm treatment efficacy, reliability, and costs over the long term as other blind spots that must be addressed to protect human health and the environment.

New Mexico is pursuing five strategies to address some of these issues, including 1) state-of-the-science chemical analysis and spectroscopy to identify and quantify all constituents in produced water; 2) collaborative state-of-the-science Whole Effluent Toxicity (WET) testing; 3) human cell line testing to understand the human risks and toxicology involved in the discharge of treated produced water into the environment; 4) fate and transport modeling of treated produced water discharges for various uses; and 5) plant and soil bioaccumulation and toxicity testing in green houses at New Mexico State University. “This multi-pronged … strategy provides overlapping analysis and evaluation of the human and environmental health impacts of produced water treatment and reuse, to improve public confidence in the safety of using treated produced water for various fit-for-purpose uses,” according to the New Mexico Produced Water Research Consortium.

“Reliable and resilient water supply is critical to both society and the environment, and it is important to explore all possibilities and options to sustainably manage this precious resource,” Mueller stated. “It is equally important to recognize that science takes time. If the consortiums’ efforts move forward without full transparency … there will be even more scrutiny on conclusions drawn, particularly if issues arise after larger-scale produced water reuse that should have been identified by proper science-led efforts.” Produced water involves a lot of opportunities, said Mueller. “But it is important we get this right.”

Trey Gerfers is a San Antonio native and serves as general manager of the Presidio County Underground Water Conservation District. He has lived in Marfa since 2013.