Reducing Water Use By Increasing Cooling Tower Cycles of Concentration

Abstract: Water is the cooling medium in many industrial processes and for air conditioning in commercial and institutional buildings. The majority of this water is recirculated via evaporative cooling towers. In many facilities evaporative cooling towers consume up to 35% of total input water. Part of the water used is removed from the cooling tower system as blowdown to prevent scale formation. Blowdown amount is controlled by the cycles of concentration (COC) required to prevent scale formation. The majority of cooling towers are supplied with hard makeup water which typically results in a COC between 2 and 4. Increasing COC to 8 to 10, or more, substantially reduces blowdown and thus fresh water use.

Reported will be the use of softened makeup water to increase cooling tower COC to a minimum of 8. Concentrated soft water is very corrosive and the patented water treatment chemistry invented to control corrosion in cooling tower systems operated at high COC will be discussed. Case history data will be present on several cooling tower systems converted to use of softened makeup water. Water usage, analysis results, and corrosion coupon data will be presented along an economic evaluation of the process.