Oil and gas wastewater spread on roads releases harmful toxins

WASTEWATER from oil and gas facilities can be spread on roads for dust suppression or de-icing, but an analysis of wastewater has revealed high concentrations of radium and other contaminants.

Dust kicked up from unpaved roads is a health hazard that can cause respiratory and cardiovascular problems. Almost 200 different dusts suppressants are available, most of which use chloride salts or brine that can aggregate with the dust particles and bind the clay to the road. However, in some regions with low budgets, oil and gas wastewater is used as it is provided for free by industries.

"Oil and gas wastewaters are known to have high salt, organic and radioactivity concentrations," said Travis Tasker, a graduate student in environmental engineering at Pennsylvania State University and lead author of the study examining the wastewater. "When we found out that this wastewater was being spread on roads, we wanted to evaluate its potential to cause biological toxicity and accumulate in road material or migrate into water resources."

Spills from oil and gas wastewater treatment plants are known to release contaminants into the environment, but the study showed that use on roads could be a bigger problem than spills. Thirteen states in the US allow roads to be treated with oil and gas wastewater, with significant spreading occurring in Ohio and Pennsylvania. The team of researchers collected water samples from townships in Pennsylvania and found that radium, which is radioactive and a known carcinogen, produced a median radioactivity of 1,230 picocuries/L, which is significantly higher than the federal drinking water standard of 5 pCi/L. Dissolved solids, including inorganic salts, had a median concentration of 293,000 mg/L compared to the 500 mg/L standard for drinking water.

The team also performed a series of simulated rainfall events to determine the level of contaminants being washed off the roads into the surrounding soil and water. The salts from the wastewater were washed off the road aggregate during the rainfall experiments. Radium was partially washed off, but after multiple applications of wastewater the road became saturated and nearly all the radium was leached off the road.

More than 130m L/y of oil and gas wastewater were spread on Pennsylvania roads between 2008 and 2014, and the researchers estimated that four times more radium was released to the environment than from oil and gas wastewater treatment facilities, and 200 times more than spill events.

The authors propose that wastewater should be treated to reduce the levels of contaminants before being spread on roads.

Environmental Science & Technology http://doi.org/crzz