Dissolved hydrocarbons

From Wikimarcellus

Dissolved hydrocarbons are found in both flowback and produced water. Some are pumped down the well during hydro-fracturing. These consist of glycols used in descaling and some light petroleum distillates used to enhance viscosity of the fracturing fluid. These are generally around 0,1% of the fracturing fluid volume.

Flowback water typically contains both free and dissolved hydrocarbons that come from the formations. These are dissolved in the frac water when it is pumped underground and held there under pressure during hydro-fracturing. Many of these are lighter than water and return to the surface with the flowback. Concentrations in the flowback water are usually low--below 100 parts per million. These can generally be removed by absorption using activated carbon during treatment. There are federal and state regulations preventing release of dissolved and free hydrocarbons into water steams, so they must be removed.