The sunny success of the natural gas industry brings with it the shadow of vast quantities of toxic wastewater. As hydraulic fracturing of shale, or fracking, results in shale gas production in the US reaching an all-time high, it also produces the byproduct of salty wastewater called brine, or “produced water.”

The shale is drilled in long horizontal wells, and some 45 million liters of water are used in each well to release gas, says the Groundwater Protection Council, a group of state oil and gas regulators and environmental protection agencies. Much of the water pumped into the wells comes back up with the extracted gas, and that returning water has a very different chemistry than the water initially sent into the wells, the Council says.

This so-called “produced water” “typically includes salts from dissolution of the underlying rock, naturally occurring radioactive substances, and chemicals added during the drilling and fracking process,” according to a new article in Chemical & Engineering News.

Yet no one knows for sure how much produced water is generated by the fracking industry or what its chemical composition actually is. Learning more about the volume and composition of the water and then finding potential safe uses for it are key. These uses might include re-using the water in new wells, using the water in thermoelectric power plants, and other uses. Some filtering of the water to somewhat “clean” it may also be necessary.

Read the full details here.