Challenges for Drinking Water Plants from Energy Extraction Activities
Fossil-fuel associated wastewaters have the potential to affect drinking water quality through surface water disposal. These wastewaters are elevated in certain components, such as bromide, which can affect drinking water quality for consumers. In Pennsylvania, the recent expansion of drilling in the Marcellus Shale has significantly increased the volume of produced water that must be managed. It is essential to determine the potential of this produced water to affect surface water. Assessment of the characteristics of this produced water, as well as other fossil-fuel associated wastewaters, will enable evaluation of the effects of surface water disposal practices on drinking water.
The objective of this work is to identify the challenges for drinking water plants from management of wastewaters associated with energy extraction activities. Focusing on regional activity in Pennsylvania, a state with significant energy and water resources, this work has reached three conclusions. First, increases in the volume of oil and gas produced water disposed of to surface water from 2008 to 2010 increased the total dissolved solids and bromide loads in Pennsylvania, which affected concentrations of those constituents at the drinking water intakes. Changes to the management of this produced water in 2011 significantly decreased the total dissolved solids and bromide loads, and thus the concentrations at the drinking water intakes. Second, regional fossil-fuel wastewaters can be differentiated by their anion ratios, and the use of anion ratios in conjunction with concentration data enables evaluation of the extent of mixing between oil and gas produced waters and freshwater. This method can be used to track water quality changes in areas experiencing fossil fuel activity and provide insight into causes of observed changes. Finally, high bromide concentrations at drinking water intakes in 2010 were not attributed solely to low flow conditions in the river. River conditions were similar in 2010 and 2012, but significant load reductions improved water quality in 2012. The decrease in bromide loading is likely associated with a voluntary ban on the use of surface-discharging treatment plants for shale gas produced water disposal in the region.