Cooling Tower Blowdown

Problem: Frequent cooling tower blowdown due to poor solids dispersion generated a large volume of wastewater. This resulted in considerable waste management costs (disposal in Class II well). The cooling water system used a scale inhibitor sensitive to high pH; therefore, sulfuric acid was added to the system to maintain a lower pH. Additionally, the chemicals were added to the system in batches.

Solution: First, a substitute scale inhibitor was selected. The new scale inhibitor functions at a higher pH and has better solids dispersion qualities. A chemical dosing or metering system was installed so that chemicals were introduced into the cooling water system continuously, rather than in batches. Also, bromine was substituted for chlorine as a biocide.

Benefits: The changes made to the cooling water system resulted in reduced make-up water volume and reduced wastewater volume. The use of sulfuric acid was eliminated. The bromine biocide offered greater worker safety. The chemical dosing system resulted in more efficient use of chemicals and operation of the cooling water system. All of these improvements resulted in a savings of several thousands of dollars per year per cooling tower. (Note: The contributing operator did not provide specific dollar amounts).