Oil and Water?
Among the industrial non-obvious water users, oil refineries are right up there! As if we needed more bad environmental news about using fossil fuels…
Water use can be as little as none and as much as 2.5 gallons of water per gallon of product—it varies depending on which process is used. Water loss is primarily due to cooling towers (as it is in many industrial sectors).
This article (it’s lengthy!) explains.
http://www.sciencedirect.com/science/article/pii/S0016236117309511