REUSE OF TREATED EFFLUENT AS COOLING TOWER MAKEUP AT AN INDUSTRIAL COMPLEX IN PUERTO RICO

Water conservation and reuse opportunities were sought at DuPont's industrial complex in Puerto Rico due to production increases along with water supply and site discharge flow restrictions. A major renovation and upgrade of its wastewater treatment (WWT) system provided an opportunity to explore effluent recycle alternatives. A water survey and site water balance was completed in 1998. Treatability studies were conducted for the new WWT facility as well as potential effluent polishing technologies in 1999 and 2000, respectively. Sequencing batch reactors (SBR) and weak acid cation resin ion exchange were the basic technologies selected. This paper presents the case history of the evaluations that led to the overall plan for reusing treated wastewater in the industrial complex's cooling tower to replace fresh water makeup. The new WWT system has a design capacity of 225,000 gal/day (35.5 m3/hr) with a target recovered water flow of 173,000 gal/day (27.3 m3/hr). Up to 77% of the site's effluent will then be recovered and reused as cooling tower makeup resulting in a 45% reduction in future fresh water consumption for the complex. The discharge to the regional sewer will be comprised primarily of the filter backwash and the neutralized regenerate waste.