pH Drift Cascade in a Cooling Tower

One mechanism from Chapter 11: The Pillars of Water Treatment.

flowchart TD
  Trigger["Acid feed fails or CO2 stripping (pH 8 to 8.8)"]
  Trigger --> Carb["Carbonate equilibrium shifts toward CO3 2-"]
  Carb --> Scale["CaCO3 supersaturation, LSI positive, scaling rises"]
  Trigger --> Bio["Free chlorine shifts to OCl-, biocide weakens"]
  Bio --> BioGrow["Biological pressure increases"]
  Trigger --> Phos["Calcium phosphate precipitation risk (if phosphate inhibitor)"]
  Scale --> Foul["Surfaces foul"]
  BioGrow --> Foul
  Phos --> Foul
  Foul --> SolidsAmp["Suspended solids accumulate and amplify"]
  SolidsAmp --> UDC["Possible under-deposit corrosion"]

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Diagrams · The Big Picture · Chapter 11