Water and Wastewater Terms Beginning L

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Langelier Index (LI)

An index reflecting the equilibrium pH of a water with respect to calcium and alkalinity. This index is used in stabilizing water to control both corrosion and the deposition of scale.

Langelier Index = pH – pH_s

where,

pH = Actual pH of the water

pH_s = pH at which water having the same alkalinity and calcium content is just saturated with calcium carbonate