Disposal of Produced Water from Oil and Gas Exploration: Environmental Impacts on Waterways in Western Pennsylvania

Abstract

Produced water is the largest waste stream from oil and natural gas production. The large volume (15 to 20 billion barrels generated annually in the U.S.) and high salinity (5,000 to 270,000 mg/L TDS) of produced water could pose severe environmental impacts upon inadequate disposal. Treatment of produced water through wastewater treatment facilities is a commonly used disposal method in Pennsylvania. This study is based on direct field sampling of effluents released into the streams of the Conemaugh, Alleghany and Monongahela Rivers in Western Pennsylvania. Major and trace element analyses show facility effluent concentrations three times higher than seawater (100,000 mg/L TDS), bromide and trace element levels up to 4,000 times higher than values upstream of facilities. The study reveals a zone up to 500 meters downstream from the facility outfall in which the contamination largely exceeds values upstream of the outfall. High levels of naturally occurring radioactive material (NORM) is retained to stream sediments. Dissolved salts, metals and NORM are potentially contributing to long-term ecological effects on aquatic life. This study provides a systematic assessment of: (1) contaminant releases to the environment from oil and natural gas produced wastewater; (2) the fate of contaminants in surface water; (3) and the concerns regarding the long-term environmental impacts on waterways in Western Pennsylvania.