Produced water—the subject of a new EPA draft study—is a multifaceted environmental issue that presents golden opportunities and prompts difficult human health and ecological questions. The draft is the latest in a series of actions the Agency is taking to better understand how produced water is managed nationwide, explore additional management options, and consider the regulatory steps that would need to be taken to authorize those options under the Clean Water Act (CWA).
The EPA defines produced water as “the fluid brought up from the hydrocarbon-bearing strata during the extraction of oil and natural gas, and includes, where present, formation water [water occurring naturally in the underground formation], injection water [water added by the oil and gas (O&G) operator to facilitate O&G production], and any chemicals added downhole or constituents released from the formation.”
Produced water is by far the largest wastestream associated with the O&G sector. The great majority of produced water from onshore wells—the focus of the study—is injected underground either for disposal or to stimulate additional O&G production. Produced water disposed into deep underground formations will rarely be available for any future use. A small amount of produced water is beneficially used, for example, for irrigation. But if there is one major point the EPA makes in its draft, it is that there is a desire in the O&G industry and among states in arid regions to find ways to allow produced water to be discharged into surface waters. Much of the draft summarizes views on produced water the EPA collected from a substantial number of stakeholders, which the report segregated into six groups—state agencies, tribes, O&G industry members, nongovernmental organizations (NGOs), members of academia, and other entities (e.g., publicly owned treatment works (POTWs), technology vendors, and service providers).
“The EPA intends to consider the information obtained during the outreach activities, as well as any additional public input following publication of this study, as the Agency determines next steps for produced water management under the CWA,” states the Agency.
According to the Colorado School of Mines, in the United States, about 900,000 wells generate approximately 890 billion barrels of produced water each year. (That’s roughly equivalent to all the freshwater and salt water the U.S. Geological Survey reports was withdrawn in the United States for all purposes over a 3-day period in 2015.) The number of U.S. wells tends to fluctuate with the price of gas and the O&G technology being used; however, in its report, the EPA states that advances in O&G drilling and production techniques, hydraulic fracturing in particular, “have resulted in dramatic increases in the number of oil and gas wells drilled in the United States.” More wells do not necessarily mean more produced water. For example, older wells that generated very large quantities of produced water are being closed, and less produced water is occurring at newer wells operated with more advanced technologies.
Some produced water is relatively clean, but most has a high saline content (up to 10 times saltier than seawater); other common impurities include naturally occurring radioactive materials, waxes, greases, sand, scales, carbon dioxide, hydrogen sulfide, and metals. Also, water used for hydraulic fracturing returns to the surface with chemicals that expedite fracking. Because of their sheer numbers, fracking chemicals may present the biggest obstacle to discharging produced water to surface waters or making it available for other beneficial uses. For example, the Environmental Defense Fund (EDF) says that FracFocus, a database of fracking chemicals, as well as other literature, identifies more than 1,600 different chemicals potentially present in produced waters.
“Some advocates for beneficial reuse argue we know enough to safely treat and use the wastewater for crop irrigation,” says the EDF. “But the unfortunate reality is that our current scientific methods can only detect about a quarter of those 1,600 chemicals.”
Because of the generally high level of contamination, the most common destination for produced water is back underground. The Produced Water Society reports that in 2012, about 91 percent of produced water was injected underground. Slightly more than half of that was injected into producing formations for enhanced recovery, and slightly less than half was injected into noncommercial and commercial disposal wells. The other management options are transportation to an off-site commercial treatment and disposal facility (nearly 7 percent); evaporation (3.6 percent); and, with produced water with low salinity, beneficial uses such as dust and ice control on roads (0.6 percent). There are also applications of produced water for irrigating crops; this is occurring primarily in California, although limited use has occurred in other states.
Any future management of produced water approved by the EPA would need to be in compliance with the CWA. At present, the EPA has used its CWA authority to prohibit direct discharges from onshore O&G producers to surface waters; the prohibition does not apply west of the 98th meridian (Subpart E of 40 CFR 435).
Any revision to regulations that would allow the nationwide discharge of produced water into surface waters would begin with the EPA changing its effluent limitation guidelines (ELGs) for such discharges. ELGs are national wastewater discharge standards developed by the EPA on an industry-by-industry basis. When developing ELGs, the EPA identifies the best available pollution control technology economically achievable for that industry and then sets regulatory requirements based on the performance of that technology. The ELGs are incorporated into National Pollutant Discharge Elimination System (NPDES) permits for direct dischargers. Analogous pretreatment standards are developed for indirect discharges to POTWs. Also, if the technology-based limits are insufficient to ensure that the quality of the surface water is maintained for its designated use, the NPDES permit writer will add water quality requirements to the permit.
In addition, discharges from centralized waste treatment (CWT) facilities that accept produced water are regulated under ELGs. These regulations provide for discharge to surface waters and contain numerical limits for pollutants in such discharges.
More Management Options
“Nationally, there is broad support amongst the oil and natural gas industry and its service providers for additional wastewater management options to treat and discharge produced waters more broadly,” states the EPA.
The Agency adds that interest in the discharge of produced water to surface water varies across the country. For example, in states where deep wells for disposal are becoming hard to find or where there are concerns that overpressurization of receiving foundations can induce seismic activity, the option to treat and discharge into surface waters is desirable. But treatment and discharge are costly and often involve transportation costs. This option is not viewed as competitive in areas where there is adequate deep-well disposal capacity and low seismic risk.
Between April 2018 and November 2018, the EPA says it had 86 calls or meetings with almost as many stakeholders. The draft summarizes the “thoughts and opinions” of the participants; the EPA does not provide any interpretation of or opinions about the information it obtained. Following are the Agency’s summaries of some of the “major themes” the Agency heard.
- States generally saw treated produced water as a potential additional source of water that can augment surface and groundwater supplies. This thinking was particularly common among states that have significant O&G extraction activity, that are arid or semiarid, and where water scarcity is a current and growing problem.
- There was a preference for treatment and discharge close to where produced water is generated. This reduces the need for transportation, which can be costly and brings with it the risks of spills or illicit discharge. The risk of illicit discharge is also more evident in the absence of treatment and discharge.
- In states where water rights and water allocation law are established, there were questions about who would own produced water that is treated for discharge. Representatives of some state agencies indicated that there has been or is ongoing work to clarify ownership and water rights for discharged produced water.
- Some states indicated that little is known about produced water composition due to the variety of chemicals used by industry in fracturing, stimulation, and well maintenance. While producers are required to disclose the chemicals used in hydraulic fracturing in some cases, representatives of some state agencies said that these disclosures are often incomplete due to the proprietary nature of formulations. They indicated that many of these compounds have not been evaluated for human health and aquatic toxicity and that treatability has not been determined.
- Treatment residuals such as concentrated brines, crystallized salts, and sludges would also require management, which would add to costs.
- Many state representatives indicated that the timeline required to obtain NPDES permits could present a business impediment to broader discharge. A sector-specific general permit was viewed as a desirable option.
- Most industry reps supported additional discharge options for treated produced water. Those who did not see the need for additional discharge options and did not favor regulatory changes were some producers currently discharging under the Subpart E beneficial reuse provisions.
- Representatives pointed to other industries that are permitted to discharge wastewater and would like there to be equity in this respect. An example was petroleum refineries, which can discharge wastewater; yet, the O&G extraction industry that supplies petroleum to the refineries has limited discharge options.
- One major operator stated that it would not support the use of treated produced water outside the oilfield due to a lack of science about treatment efficacy and associated liability risks. There are some impediments to reuse, including perceived liability. Business competition was another perceived impediment to reuse.
- While use of CWT facilities is currently limited, as they exist only in certain areas of the country, producers indicated that they would use commercial facilities if they were available and cost-competitive with other disposal options.
- Industry representatives also indicated that discharging treated produced water could be a potential revenue source, as downstream users may pay for the water. However, this would depend on water rights and ownership of the water.
- If the costs and regulatory burden for managing produced water are too high, O&G may not be developed in certain areas.
- The primary concern raised by NGO representatives was the potential toxicity and human health and ecological implications of discharges of produced waters. This is due to the large number of chemical compounds used in hydraulic fracturing, well maintenance, and other exploration and production activities. There are also constituents naturally present in producing formations that are contained in the resulting produced water. NGO reps observed that there is little toxicity data for many chemicals.
- Some NGOs were also concerned that analytical methods do not exist for many of the chemical compounds used in exploration and production. In addition, they indicated that the high salinity of many produced waters can interfere with certain analytical approaches, complicating quantification of constituents in produced water. Such limitations could result in discharges that meet permit requirements yet still endanger human health and the environment.
- NGO reps were opposed to the EPA revising ELGs to allow for broader discharge of produced water, stating that it is not the EPA’s responsibility to solve industry’s water management problems.