Water Analysis: Hongqiao, China

                                 Make up          8.0 CoC
Conductivity             304                   2432
pH                              7.6                     8.7
Ca Hardness             55.5                  444
Alkalinity                  73                      584
Chloride                    28                      224
Total Hardness        111                    888
Silica                          5.5                    44
Predicted LSI                                    2.4

This make up water sample from Hongqiao China was sampled and analyzed for use in a cooling tower application. By using the Langelier Saturation Index (LSI) we can predict the scale forming tendency of the water. Modern water treatment chemistry can prevent scale in waters with a LSI of 2.3-2.5. In waters with a pH greater than 8.5 that contain silica and magnesium hardness a mineral scale problem could occur. Under the right conditions Magnesium Silicate will form. This scale is a barrier to heat transfer and is one of the most difficult scales to remove. Silica levels are typically not a concern below 150ppm and can be handled as high as 200ppm with proper chemistry.




We can see from the above calculation that this tower can be operated safely at 8.0 Cycles of Concentration (CoC). At 8.0 CoC the water will have an LSI of 2.4 with a silica level of 44ppm. Both levels are within the acceptable range of modern water treatment chemistry. It is important to note that at a LSI of 2.4 the water is extremely scale forming. If the proper amount of water treatment chemical is not maintained at ALL times the system will rapidly develop scale. Many facilities in Asia do not utilize modern chemical feed and control equipment. Instead they manually dose chemical and control bleed valves. It is not possible to maintain tight enough control with manual methods to achieve the water savings possible at 8.0 CoC without eventually forming scale. For this reason an automated chemical feed and control system must be installed.



Why does this information matter? Higher CoC results in lower water and chemical consumption. Consider a 1,000 ton (RT) tower operating 24 hours a day, 365 days per year at full load. By increasing tower cycles from 1.0 to 8.0 cooling tower make up is reduced by 1,611,938 liters (425,829 gallons) per day! This significant savings can easily be realized with a sound water treatment program and routine monitoring.