Wastewater from fracking sites is mostly natural brine, according to a recent university study in a story at phys.org:
"Naturally occurring brines, not man-made fracking fluids, account for most of the wastewater coming from hydraulically fractured unconventional oil and gas wells, a new Duke University study finds.
"'Much of the public fear about fracking has centered on the chemical-laden fracking fluids—which are injected into wells at the start of production—and the potential harm they could cause if they spill or are disposed of improperly into the environment,' said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment.
"'Our new analysis, however, shows that these fluids only account for between 4 and 8 percent of wastewater being generated over the productive lifetime of fracked wells in the major U.S. unconventional oil and gas basins,' Vengosh said. 'Most of the fracking fluids injected into these wells do not return to the surface; they are retained in the shale deep underground.'
" ... These brines carry their own risks, Vengosh stressed. They contain varying levels of salts, heavy metals and naturally occurring radioactive elements, and their sheer volume makes disposing of them a challenge.
Read the whole story here.