Produced water from oil and natural gas drilling sites that is treated at wastewater plants appears to create elevated levels of some of the “most toxic” chemicals, according to the U.S. Geological Survey (USGS).
Brominated disinfection byproducts are created from the treated wastewater through chemical reactions when the water is disinfected, according to the new USGS study. “Of the hundreds of known, or suspected, disinfection byproducts possibly created by disinfection processes, the brominated forms are among the most toxic,” researchers found.
“While these findings do not indicate an immediate threat to aquatic life or human health, the study provides new data on the water quality of streams receiving discharged wastewater that can be used to inform decisions about management and treatment of produced waters,” said primary author Michelle Hladik.
Waters co-produced when resources are extracted from deep geological formations, commonly called produced waters, are composed of naturally occurring materials characteristic of the geologic formations in which they originate. Water in the geologic formations often consists of a brine with high concentrations of bromide, iodide and other ions such as sodium and chloride, researchers said.
Produced waters originate from both unconventional and conventional drilling, USGS said. Operators today mostly manage their produced waters by recycling, road spreading, deep-well injection and by wastewater treatment plants. The brominated disinfection byproducts appear only to be from produced waters with high levels of bromide.
“Currently, and during the time of the study, most wastewaters from unconventional oil and gas activities such as hydraulic fracturing in the study area have been deep well injected and therefore not processed by wastewater treatment plants,” the researchers found. “However, this study did not attempt to quantify the relative proportions of produced waters originating from the various unconventional or conventional oil and gas extraction activities.”
Water samples were collected from river waters downstream from discharges at publicly owned and commercial wastewater treatment plants processing produced waters with high levels of naturally occurring bromide. The samples then were compared with water upstream of the plants, as well as with samples from wastewater treatment plants that didn’t process produced water.
Twenty-nine different disinfection byproducts were examined in the water samples; brominated disinfection byproducts were detected more frequently “at at much higher levels in river water impacted by disinfected produced waters than at other sites,” the researchers said.
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