Water and oil. Two very different substances but which are closely linked in the oil and petrochemical industry. The first thing we think about when someone mentions oil is the price. Hasn’t petrol been expensive recently? There are, however, other not so immediately obvious aspects which the majority of us do not know about until someone explains them to us. Do you know how many litres of water are needed to extract and refine oil? From every 10 litres of crude oil extracted, 7 are contaminated water. Further down the process, to refine this crude oil, 80 million cubic metres of water a year are required in a medium-sized plant. In Barcelona, for reference, the volume of mains water consumed in the city in one year is 95 million cubic metres.