Upgrading Refinery Wastewater Treatment with MBR to New Discharge Standards at Marathon Petroleum’s Detroit Refinery

The refining process consumes a large amount of water, mainly for cooling and steam generation systems, and produces wastewater from the various process steps. Refineries are now faced with both the challenges of discharge standards becoming more stringent and freshwater supply becoming increasingly scarce and costly. In the process, wastewater is primarily generated from the desalting process, where crude oil comes in contact with large quantities of clean water to strip salt out and meet the crude oil specification for the distillation tower. Refinery wastewater contains salts, petroleum hydrocarbons, oil and grease, suspended solids and other contaminates.Most refinery wastewater streams contain different levels of toxicity that are always challenging for biological treatment processes. The ability to treat wastewater to higher standards with the option to reuse the treated effluent as process water is becoming an attractive opportunity for refineries. Membrane Bioreactor (MBR) technology is a proven process for treating refinery wastewater to stringent requirements enabling the reuse of the effluent within the process.Marathon Petroleum Company LP (MPC) in Detroit, Michigan has a refinery with a capacity of 132,000 barrels per day. Originally, the facility included wastewater pretreatment that comprised of Induced Gas Flotation followed by Sand Filtration to finally discharge to the municipal sewage system. In 2011, a new discharge requirement was established to include volatile organic compound removal, with Benzene as the primary constituent. Due to these requirements, MPC decided to move forward with a four-month pilot study using MBR technology.After successfully demonstrating consistent effluent quality below discharge standards, MPC proceeded with the design and installation of a full-scale, 4 million gallons per day MBR. This paper will present the key topics related to MBR technology in refinery applications, pilot study results and system design and performance after 18 months of operation at the MPC Detroit refinery.