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Briefly describe the wastewater streams typically generated in the petroleum industry.

Solution. Throughout the life cycle of crude oil, through extraction, transportation, and refining, roughly 5 to 7 gal of water are used for every 1 gal of crude oil processed. Of this total, roughly l to 2.5 gal of water are used for every 1 gal of crude oil stock. In the United States, 1 to 2 billion gal of water are used per day in the refining industry. Water consumption varies for different regions and different qualities of crude oil. These water estimates do not include unconventional shale formations, where water usage is generally much higher. Water consumption in refining is a result of evaporation and drilling, blowdown, process discharge, and some incorporation into finished products. All water that is incorporated into the refining process is treated or filtered onsite before it is either reused on site or discharged into the environment.

Wastewater streams include separation process wastewater, tank bottoms, cooling tower condensate blowdown, source water treatment, and storm water. American Petroleum Institute (API) separators are commonplace in most refineries and separate sludge and hydrocarbon components out of process wastewater. Refineries today have installed dike systems to keep process wastewater from draining into storm sewers.