Increasing Tower Cycles Improves Economics

Most people know that increasing the cycles of concentration in a cooling tower saves water and reduces cost. The cycles of concentration can often times be increased by feeding acid, changing the make-up water source, partial softening, or a combination of all of these. The graph below depicts the difference in water requirements for a tower that evaporates 60 gallons/minutes (gpm) operating at various cycles of concentration. As you can see moving from 3 to 5 cycles, reduces the make-up requirements from 90 gpm to 75 gpm due to the reduction in blowdown. If your cost of water is $1.50/1000 gallons and your tower operates year round this equates to a water savings of $11,826 annually. Additionally, since you are reducing blowdown from 30 gpm to 15 gpm, you would only need to feed half as much chemical for scale and corrosion inhibition.
Depending on the cost of your chemical treatment program this could save an additional $10,000 to $25,000 annually. Finally, as you can see from the chart, operating much above 6 cycles of concentration does not have much impact on water usage.