Problem 11.8: A cooling tower has high calcium hardness and
From Chapter 11 Problem Set. Level 3: System Integration.
Question
A cooling tower has high calcium hardness and a phosphate-based corrosion inhibitor. Scale pressure is rising. Lowering pH would help with CaCO₃ control, but may destabilize other parts of the treatment strategy.
Give two alternative responses besides simply feeding more acid. For each, explain the consequences across all four pillars.
Answer
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Strong answers may include two or more of the following:
Increase blowdown to reduce concentration of calcium and alkalinity
Improve solids removal and deposit control
Optimize dispersant or polymer feed
Shift to a different corrosion inhibitor strategy
Improve control stability and monitoring rather than making a large acid adjustment
The best answers trace the consequences through all four pillars:
- reduced scale pressure
- possible effects on corrosion protection
- indirect effects on biology through cleaner surfaces
- changes in solids accumulation and transport