Between 10 to 50 per cent of the fracking fluid flows back to the surface with the gas when the well is depressurised, this is known as backflow. The rest of the fluid remains underground.
At the surface, tanks will collect the back flow. It is generally re-used in future fracking, or desalinate and disposed of as waste water through the sewage system, or trucked away and disposed of via a wastewater injection well. It is important that flow back water is handled correctly (avoiding accidental spillages on surfaces) and, as appropriate, dispose of correctly.
Flowback water can become contaminated through contact with shale, dissolving salts from it and also picking up traces of natural radioactivity. Shale formations are naturally slightly radioactive. It is important that any radioactive content be taken into account in the procedures for handling the flowback and production fluids at the surface.
During the drilling phase, about 3000 tonnes of drill cuttings of rock (equivalent to a cube of solid rock 10 m x 10 m x 10 m) will have been produced per well. This must be trucked away and disposed of.
Procedures for the disposal of waste fluids and solids are subject to geographical considerations and local and national mining waste disposal regulations.