This paper describes the pilot testing and implementation of a major advanced wastewater reclamation project to recover secondary effluent from the biological organic wastewater treatment system (OWWTS) and cooling tower blowdown (CTB) for reuse in a large petrochemical plant. The treatment processes used include chemical oxidation by sodium hypochlorite, dual media filtration, granular activated carbon adsorption, ultrafiltration (UF), ultraviolet (UV) disinfection, cartridge filtration, reverse osmosis (RO), and degasification. The reclaimed water, which is quite pure, is used as feed water for the petrochemical plant’s ion exchange-based deionization (DI) system. Using this water as DI system feed saves more than 80 percent of the expensive DI system regeneration cost and drastically reduces water purchase cost and wastewater discharge fees. The treatment system was testing on a pilot-scale basis (110 m3/d) for nearly 18 months. Testing at various flux rates for UF/RO and an accelerated biofouling test for the hollow-fiber UF membranes were conducted. With excellent pretreatment, the thin film composite (TFC) polymide RO membranes were relatively clean and non-fouling after more than 2,000 hours of operation without the need for chemical cleaning. A total overall water recovery of 73.6 percent was achieved consistently in the pilot plant. The economic analysis indicated that a payback could be obtained in 4 years. A full-scale plant treating an effluent blended flow of 9,000 m3/d of OWWTS effluent and CTB has been constructed at the petrochemical plant. The design/build project took approximately 2 years to complete. However, the startup took much longer than anticipated due to some deficiencies in design and construction, and operational oversights. This paper discusses some of the lessons learned from the implementation of the full-scale project.