The 434,000 B/D Baton Rouge, Louisiana Refinery of Exxon Company, U.S.A. is the largest in the United States and one of the most complex in the world (Figure 1). Over 500 products are made from petroleum including motor gasolines, aviation fuels, diesel and other distillate fuels, and lubricants, greases and waxes. Until the mid 1960's cooling water was provided by cooling towers and once-thru river water. This once-thru river water averaged about 135,000 gpm and picked up about 80% of the oil discharged in the plant effluent. It was therefore logical after reducing plant oil losses to a minimum to replace once-thru river water with recirculating cooling water systems. The existing cooling towers were supplied with low-hardness well water makeup (4-26 ppm CaCO3), ran less than 2 cycles of concentration and required only chlorination for essentially trouble-free operation. It was normal for the admiralty brass tube bundles to run six or seven years, then require only high pressure hosing at the tube ends before returning to service. However, the drilling of wells to keep up with population growth and industrial expansion in the Baton Rouge area had caused an appreciable drop in well water levels. Therefore, it was decided that makeup for the new cooling towers would be clarified, partially- softened Mississippi River Water (see Table 1). It was further decided that some existing systems would be changed from well water to clarified water makeup to decrease the consumption of well water to try to improve water levels.
