IRVINE RANCH WATER DISTRICT (IRWD) PILOT STUDY OF THE USE OF RECYCLED WATER IN COOLING TOWERS

In October 2002, a newly constructed, dual-plumbed, 14-story office building in Irvine passed its cross-connection test with local health agencies and was charged with disinfected tertiary treated recycled water. The mechanical engineer designed this high-rise building to use recycled water in the toilets, urinals, trap primers, and cooling towers. In July 2003, Irvine Ranch Water District (IRWD) sponsored a pilot study in conjunction with the management and owners of the building to study the benefits and report the findings for IRWD's future customers using recycled water in cooling towers. The pilot study included establishing a cooling tower water treatment service provided by a nationally known chemical service company. The cooling towers were connected to the recycled water supply. The pilot study encompassed two openlooped cooling towers (makeup water is added and blowdown water is discharged to the sewer) and one closed-circuit cooling tower (cooling water is drawn and discharged to one of the common sumps used by the other two cooling towers) located on the rooftop of the office building.Pilot study results concluded that the key chemical constituents in IRWD's recycled water are comparable to potable water and when cooling tower operation is properly maintained and controlled recycled water can be used as cooling water. Cost savings from using recycled water compared with potable water provides an incentive for customers in the IRWD service area to use recycled water and help California conserve vital water resources.