How toxic is oilfield wastewater? New paper highlights gaps in our understanding.

Collaborative research is a critical element for identifying unforeseen risks associated with using the oil industry’s wastewater outside the oilfield. That’s the recommendation of a new peer-reviewed paper accepted this week in the Journal of Integrated Environmental Assessment and Management (IEAM).

The paper comes at a crucial moment for the oil and gas industry, which generates some 900 billion gallons of salty, chemical-filled water (also called produced water) each year. Traditionally, companies dispose of this wastewater deep underground where it is less likely to cause contamination. But economics and water scarcity are forcing questions about other ways to treat, reuse and even repurpose this wastewater. In fact, the Environmental Protection Agency (EPA) will release a report very soon that could make it more common for companies to discharge their wastewater into rivers and streams.

The IEAM paper outlines the conclusions of a multi-day toxicity workshop where experts from the oil and gas industry, academia, government and the environmental community collectively identified key knowledge gaps associated with this waste stream and determined tools, technologies and methods needed to help close those gaps.

How toxic is it?

That’s one of the critical questions researchers are trying to answer before allowing potentially risky practices (like using wastewater to recharge our aquifers or irrigate our crops) to become the norm. In order to protect communities and environments from harm, policy makers should understand who, or what, may be at risk from varying levels of produced water exposure. Right now, we just don’t have the data we need to prevent unforeseen risks, and that’s a problem because we don’t want to “solve” one problem, only to create several more. As the saying goes, an ounce of prevention is worth a pound of cure, and clean water isn’t something to gamble with.

In the IEAM paper, experts identified specific tools and practices that can be modified or developed to properly evaluate produced water toxicity, and to develop effective management programs.

Key lessons learned

1. Don’t pass the salt
Produced water can be 10-times saltier than seawater, unfortunately most of the methods we use to detect chemicals simply don’t work in water with such high salt content. Furthermore, researchers warn that toxicity assessments for produced water must not ignore salt. In addition to developing tools that can work despite the presence of salt, we also need to evaluate how salt might influence the toxicity of other chemicals and determine what level of toxins might remain even after treatments that reduce or remove salt.

2. Evaluate whole mixtures and individual chemicals
As the paper notes, there are existing scientific methods which have been used to assess other complicated mixtures (like municipal wastewater) that can also be applied to produced water. Take Whole Effluent Toxicity (WET) Methods, for example. These WET tests have historically helped us evaluate how different mixtures may impact certain aquatic organisms like fish or algae.

Importantly, permits that require effluent to pass WET tests can stop treated wastewater from being released if it is still toxic, even though it meets limits for specific chemicals. It is difficult to measure everything in a complex waste stream. Therefore, WET tests are a valuable safety check used to help catch unforeseen issues. However, these methods alone are not enough to really understand whether or not a sample of treated produced water is clean enough or safe enough for its intended purpose.

That’s why it’s important to combine traditional tests with other emerging methods that can help identify and predict toxic effects. These newer methods are designed to evaluate the toxic effects of chemicals and mixtures on things like cells rather than whole organisms like fish or rats. EPA uses these types of methods through the ToxCast and interagency Tox21 chemical testing programs. This creates an opportunity to apply the improved methods to produced water as well. This is critically important because these new tools can help us better model how a sample might affect a variety of organisms over time in a more efficient way than traditional tests.

3. Not all wastewater is created equal
Produced water is not a monolith. It varies from well-to-well and even over time from the same well. Therefore, we need to design research programs that account for the ways different water samples could impact different environments in different scenarios.

4. Evaluating impacts on land and water
The majority of available research and toxicity assessment tools primarily focus on detecting or predicting impacts on water quality and aquatic organisms – and less so for crops or soils. Given that some produced water reuse options involve land application, there is a need to develop tools to better investigate potential impacts produced water may have on land and soil.

5. Better together
Chemists, agronomists, toxicologists, engineers and others must work collaboratively to collect and share vital data about chemical toxicity as well as potential risks of different management methods. Assessing risk requires information on chemical hazards and exposure pathways that don’t live with any one research group. Collaboration – including making produced water samples available for study — is therefore key to closing these data gaps.

Why it matters now

The forthcoming EPA report could open up risky new scenarios for expanding discharges of produced water across the country. Some drought-prone states, like New Mexico and Oklahoma, are also actively considering a wide range of opportunities for reuse in the future. It is clear that there are vital knowledge gaps that need closing. The IEAM paper, which reflects the knowledge of industry experts, environmental regulators and scientists, confirms we have tools to advance the science before policy decisions are made. We can and should prioritize this research before significantly expanding produced water reuse outside the oilfield.

By Cloelle Danforth and Nichole Saunders.

Jennifer McPartland contributed to this post.

This post originally was published on the Energy Exchange Blog.

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