Around 10 to 30% (and up to 60%) of the water that is initially injected into the ground during the fracking process returns to the surface with the extracted gas. This water is referred to as “flowback” and is likely to contain naturally occurring elements such as salts and heavy metals, from the ground, and can contain trace amounts of the chemicals from the fracking fluid.
This water must be treated to avoid environmental repercussions. Particularily serious problems arise when companies try to cut expenses and do not treat their water and dispose of it improperly. The wastewater that is treated is typically either treated on site and used for injection into another well or can be hauled off for treatment to be added back to surface water. Since total dissolved solids (TDS) have been found to negatively impact aquatic ecosystems, the Pennsylvania Department of Environmental Protection (DEP) currently requires that the flowback be treated until it has a TDS concentration of 500 parts per million or less before the water can be mixed with other surface water.
Because there are such large volumes of water used for each frack, there can be up to 1.5 million gallons of resulting flowback. Because these volumes of wastewater are so large, it makes it increasingly more likely for a spill to occur. Wastewater can spill on site by leaking out of storage containers or when adding/extracting the liquid from the storage containers. Additionally spills can occur when the fluid is being transported to an alternate site for treatment. Because the wastewater is incredibly salty and contains various chemicals it is likely to have detrimental effects on the ground to which it is exposed. Even in the best case scenario it has been predicted that each individual well in the Marcellus Shale region is likely to release at least 200 m3 of contaminated fluids. Figure 2 summarizes the ways fracking can lead to water pollution.
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©S. Doherty 2016