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Hydraulic fracturing, or fracking, is an advanced technology that is used to enhance the flow of energy from a well after drilling is complete, which is why fracking is referred to as a “completion process.” This process is carried out by sending a mixture of water, sand and certain additives into a deep-rock formation at high pressure. Soon after the fracturing occurs, water returns to the surface as “flowback” or wastewater. At that point the wastewater needs to be recycled, treated or disposed of through underground injection.

Wastewater injection is an entirely different process that’s used for disposing of waste fluids from a number of industrial activities, a number of which are unrelated to energy development. The U.S. Environmental Protection Agency (EPA) classifies injection wells intosix classes. Class II covers injection wells associated with oil and natural gas production, including disposal wells. This category also covers wells used for enhanced oil recovery, or EOR (for more on EOR,点击这里). According to EPA, approximately 151,000 injection wells arecurrently operational, and of that figure,20%是处置井responsible for wastewater management.