Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania

TLDR

The safe disposal of oil and gas wastewater in the United States is a major challenge due to large volumes and high contaminant levels, and in Pennsylvania such wastewater is sometimes treated at brine facilities before being discharged into local streams. The study aimed to assess the impact of a western Pennsylvania treatment facility on water quality and isotopic signatures. Researchers measured water quality and isotopic compositions of the discharged effluents, surface waters, and stream sediments at the site. They found that treated effluents still elevated chloride and bromide downstream, while barium and radium were largely removed, yet 226Ra concentrations in sediments at the discharge point were ~200 times higher than upstream and exceeded regulatory limits, indicating a potential radium bioaccumulation risk.

Abstract

The safe disposal of liquid wastes associated with oil and gas production in the United States is a major challenge given their large volumes and typically high levels of contaminants. In Pennsylvania, oil and gas wastewater is sometimes treated at brine treatment facilities and discharged to local streams. This study examined the water quality and isotopic compositions of discharged effluents, surface waters, and stream sediments associated with a treatment facility site in western Pennsylvania. The elevated levels of chloride and bromide, combined with the strontium, radium, oxygen, and hydrogen isotopic compositions of the effluents reflect the composition of Marcellus Shale produced waters. The discharge of the effluent from the treatment facility increased downstream concentrations of chloride and bromide above background levels. Barium and radium were substantially (>90%) reduced in the treated effluents compared to concentrations in Marcellus Shale produced waters. Nonetheless, 226Ra levels in stream sediments (544–8759 Bq/kg) at the point of discharge were ∼200 times greater than upstream and background sediments (22–44 Bq/kg) and above radioactive waste disposal threshold regulations, posing potential environmental risks of radium bioaccumulation in localized areas of shale gas wastewater disposal.