Problem 10.10: You are called to a cooling tower that has not
From Chapter 10 Problem Set. Level 3: System Integration.
Question
You are called to a cooling tower that has not had sidestream filtration, has been running without consistent biocide treatment, and has visible silt deposits in the basin. The customer wants you to “fix the chemistry.” Write a brief explanation (4–6 sentences) of why adjusting chemical feed rates alone will not solve this problem. Reference at least two amplification pathways.
Answer
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Adjusting chemical feed rates alone will not solve this problem because the suspended solids have created deposits that isolate surfaces from whatever chemistry is in the water. Increasing corrosion inhibitor concentration does not help when the inhibitor cannot reach the metal beneath the silt deposits - under-deposit corrosion will continue regardless of bulk inhibitor residual. Increasing biocide dose does not help when the biocide is consumed by EPS and organic debris in the deposits before it can reach the organisms sheltered within them. The deposits must be physically removed first: the basin needs to be cleaned, sidestream filtration must be installed to prevent reaccumulation, and a dispersant program should be used to lift existing deposits off surfaces. Only then will the chemistry operate in the environment it was designed for. The customer is asking to fix a mechanical problem with a chemical solution - and the amplifier effect guarantees that approach will fail.