Reducing Cooling Tower Water Treatment Cost
The number of cycles of concentration (CoC) a cooling tower operates at will greatly impact the overall cost of the water treatment program. Higher CoC results in reduced water, chemical, and sewer cost. The goal of any sound water treatment program is to operate CoC as high as possible without causing system problems related to mineral scale. The water treatment industry utilizes an index called the Langelier Saturation Index (LSI) to predict when problems will occur. Generically, a well designed system can operate at an LSI of up to 2.5. By utilizing a softener to remove significant portions of the make water Calcium content higher CoC can be achieved before the LSI threshold is reached. This can result in substantial operational savings. Consider the simple model below.
| Make Up | 3.0 CoC | | | | |
| TDS | 800 | 2400 | | | | |
| pH | 8.0 | 8.8 | | | | |
| Calcium | 160 | 480 | | | | |
| Alkalinity | 140 | 420 | | | | |
| °C | | 45 | | | | |
| LSI | | 2.45 | | | | |
| Silica | 9 | 27 | | | | |
| Chloride | 90 | 270 | | | | |
| | | | | | |
| Predicted Value @ 88% Ca Hardness Removal | | |
| Make Up | 5.0 CoC | | | | |
| TDS | 800 | 4000 | | | | |
| pH | 8.0 | 9.2 | | | | |
| Calcium | 19 | 95 | | | | |
| Alkalinity | 140 | 700 | | | | |
| °C | | 45 | | | | |
| LSI | | 2.34 | | | | |
| Silica | 9 | 45 | | | | |
| Chloride | 90 | 450 | | | | |
| | | | | | |
| Assumptions: 1,000 Ton tower @ 70% load, 16 hours/day, 5 days/week, 52 weeks/year |
| | | | | | |
| Annual Blowdown Savings: 4,960,404 liters/1,310,400 gallons | | |
