A large petrochemical plant (plant) located in a water-limited area uses large amounts of water in their cooling towers and manufacturing process areas. The plant uses high-purity deionized (DI) water for feed to the process and to the boilers. Ion exchange-based DI water treatment cost is high because the total dissolved solids (TDS) concentration of the water supplied by the local water company is relatively high, at 750 mg/L as CaCO3. Due to the high water consumption of the process, any expansion of plant production is limited by the availability of additional water supply, which is scarce in the area. A water resource management study was conducted for the plant, the results of which – presented previously at another conference1 – indicated that in-plant wastewater reclamation and reuse would be both economically feasible and beneficial. Figure 1 is a general block flow diagram showing the wastewater reclamation system and its relation to plant wastewater and water systems. Secondary effluent from the organic wastewater treatment system (OWWTS) would be blended with cooling tower blowdown (CTB) prior to treatment by a membrane-based advanced treatment system for reclamation. The reclaimed water, which would be of superior quality to the existing water supply, would be used as feedwater to the existing DI water system.