Sending wastewater from hydraulic fracturing operations to municipal sewage treatment plants is neither technologically or economically practical, but the Environmental Protection Agency is moving to prevent it in the future. The agency proposed a rule last week that would prohibit the discharge of fracking wastewater to publicly owned sewage plants. The agency says the action is needed because unconventional oil and gas extraction facilities have sent wastewater to sewage plants in the past, so the potential remains for some to do so in the future. At a single fracking well, millions of gallons of water may be injected deep underground to release natural gas or petroleum from rock formations. A significant part of that water returns to the surface. Many times saltier than seawater, wastewater from fracking includes organics, metals, and radioactive materials that municipal sewage treatment plants are not designed to remove. Fracking companies sometimes opt to store wastewater on-site for private treatment and reuse for future fracking operations, but the common choice is to dispose of it in underground injection wells.