Flowback and produced water are considered hazardous waste and must be disposed of safely. According to the EPA, produced waters are typically disposed of in deep wells or “non-potable coastal waters.”
Flowback and produced water can contain salt, industrial chemicals, hydrocarbons, and radioactive materials.
- Salt. Flowback and produced water are highly salty. This is because salts are added to the fracturing fluid and also released from the geologic formation. Produced water is so famous for salinity that the hydrocarbon industry often refers to it simply as “saltwater” or “brine.”
In the Marcellus Shale, flowback water has been measured to contain 32,300 mg per liter of sodium. For comparison, EPA guidelines call for a maximum of 20 mg/L in drinking water, although the agency is considering increasing that somewhat.
Industrial chemicals. Flowback and produced water contain chemicals that have been injected into the well to facilitate drilling. For example, in the Marcellus Shale, flowback water contains high concentrations of sodium, magnesium, iron, barium, strontium, manganese, methanol, chloride, sulfate and other substances.
Hydrocarbons. Produced water can contain hydrocarbons – including the toxics benzene, toluene, ethylbenzene, and xylene – which can be freed during the drilling process.
Radioactive materials. Water returned to the surface during drilling can carry naturally occurring radioactive materials, referred to by the industry as “NORM.” Flowback and produced water from several large U.S. shale formations has been found to contain the radioactive element radium. When produced water is salty and rich in chlorides, radium tends to be present in higher concentrations.
The EPA allows a maximum of 5 picocuries of radium per liter of drinking water. Produced water has been found to contain radium levels as high as 9,000 picocuries per liter [pCi/g].