The oil industry is effectively a water industry which delivers oil as a byproduct. In the North American onshore oil industry, eight barrels of water are brought to the surface for every barrel of oil. This produced water is often highly saline and contaminated by hydrocarbons: it is a hazardous waste which requires treatment, disposal, and potentially recycling.

Handling this produced water is an integral part of the oil and gas industry. The technologies used widely in this industry are membrane and thermal desalination technologies, filtration systems and biological treatment systems.