Their paper contends the wastewater contains potentially harmful pollutants, including salts, organic hydrocarbons, inorganic and organic additives and naturally occurring radioactive material. These pollutants can be dangerous if they are released into the environment or if people are exposed to them. They can be toxic to humans and aquatic life and can damage ecosystem health by depleting oxygen or causing algal blooms, or they can interact with disinfectants at drinking water plants to form cancer-causing chemicals.
Condensed from their paper:
Natural gas is found in underground layers of rock and shale gas formations are generally tighter and much less permeable than other formations, causing the gas to flow less easily. The Marcellus is the largest shale gas area in the United States by geographic area, spanning New York, Pennsylvania, Ohio, Maryland, Virginia, and West Virginia. Shale gas sources generally require more complex and expensive technologies for production and are termed 'unconventional' compared to more conventional drilling for oil. Other sources of unconventional gas include coal seams and impermeable sandstone formations. As of 2008, unconventional production accounted for 46 percent of total U.S. natural gas production.
Like food production, energy production is not pretty. Credit: NRDC
Hydraulic fracturing involves the injection of liquid under pressure to fracture the rock formation
and prop open the fractures, allowing natural gas to flow more freely from the formation into the
well for collection. The development of hydraulic fracturing technology, along with advances
that allow the horizontal drilling of wells, has facilitated the expansion of shale gas development
over the past 20 years. Prior to these innovations, shale gas development was not viewed as
economically feasible, but recently such development has exploded. The first economically
producing wells in the Marcellus were drilled in 2003; in 2010, 1,386 Marcellus wells were
drilled in Pennsylvania alone (up from 763 drilled in 2009).
The liquids used in the hydraulic fracturing process consist primarily of water, either fresh or
recycled, along with chemicals used to modify the water’s characteristics (for example, to reduce
friction or corrosion) and sand or other agents, referred to as “proppants,” that hold open the
fractures in the formation.
Wastewater, flowback and production phase water, contain potentially harmful constituents and the NRDC says the current regulatory approach is in adequate and their paper outlines limitations of current state and federal policies.
"In Fracking’s Wake: New Rules are Needed to Protect Our Health and Environment from Contaminated Wastewater", Rebecca Hammer and Jeanne VanBriesen, Ph.D., PE, NRDC