Langelier Saturation Index Calculation:-

As an example, suppose the drinking water supplied to animals has the following analysis. The LSI index is calculated at two temperatures: 25^oC (room temperature) and 82^oC (cage wash cycle). The colder incoming water will warm to room temperature in the manifolds. Residual water in the rack manifold can be heated to 82^oC when the rack is in the cage washer.

• Water Analysis:
  
  • pH = 7.5
  • TDS = 320 mg/L
  • Calcium = 150 mg/L (or ppm) as CaCO₃
  • Alkalinity = 34 mg/L (or ppm) as CaCO₃
    
    
• LSI Formula:
  
  • LSI = pH - pH_s
  • pH_s = (9.3 + A + B) - (C + D) where:
    • A = (Log10[TDS] - 1)/10 = 0.15
    • B = -13.12 x Log10(^oC + 273) + 34.55 = 2.09 at 25°C and 1.09 at 82°C
    • C = Log10[Ca²⁺ as CaCO₃] - 0.4 = 1.78
    • D = Log10[alkalinity as CaCO₃] = 1.53

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• Calculation at 25^oC:
  
  • pH_s = (9.3 + 0.15 + 2.09) - (1.78 + 1.53) = 8.2
  • LSI = 7.5 - 8.2 = - 0.7
  • Hence No Tendency to Scale

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• Calculation at 82^oC:
  
  • pH_s = (9.3 + 0.15 + 1.09) - (1.78 + 1.53) = 7.2
  • LSI = 7.5 - 7.2 = + 0.3
  • Hence Slight Tendency to Scale

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Langelier Saturation Index Calculator

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