SURFACE DISPOSAL OF PRODUCED WATERS IN WESTERN AND CENTRAL PENNSYLVANIA: POTENTIAL FOR ACCUMULATION OF ALKALI-EARTH ELEMENTS IN SEDIMENTS

The Appalachian Basin has long been a producer of hydrocarbons with over 80,000 active conventional oil and gas wells creating 6.2 million barrels of wastewater per year. Waters co-produced during hydrocarbon production are of notably poor quality (Total Dissolved Solids and total radium can exceed 300,000 mg/L and 10,000 pCi/L, respectively). The development of hydraulic fracturing has led to an additional 29 million barrels of wastewater needing treatment per year. The sudden increase in production has led to a shortfall in the region’s capacity to treat the associated increase in produced waste waters. Many publicly owned treatment works (POTWs) were used to help dispose of the excess produced waters. We assessed whether disposal practices for produced waters from both shale gas and conventional operations in Pennsylvania could result in the accumulation of alkali earth elements which are associated with produced waters. Results indicate that wastewater treatment facilities did not result in elevated concentrations of Ba or Ra in fluvial sediments (p>0.05). Although other alkali-earth elements (Sr, Ca and Na) concentrations increased, the numerous inputs of these elements into treatment plants preclude attributing them solely to produced waters. Application of brines from conventional oil and gas wells for roadway deicing resulted in accumulation of Ra (1.3x), Sr (3.0x), Ca (5.3x), and Na (6.2x) in sediments proximal to roads (p<0.05). This study provides a vital initial assessment of the impacts of produced water disposal practices on adjacent sediments. However, more work is needed to fully understand the unintended consequences of produced waters management.