Water Hardness

Written by Jerry Ratzlaff. Posted in Properties

Hardness in water is defined as the presence of multivalent cations.  The hardness of water is a measure of the constituents in solution which tend to precipitate from the water when heated.  "Temporary" hardness is principally restricted to calcium (\(Ca^{+2}\)), magnesium (Mg(+2) and iron (\(Fe^+2\) or \(Fe^{+3}\)) which tend to combine with carbonates.

"Permanent" hardness results from the same metal ions combining with the non-carbonate ions. Units of hardness are mg/l, ppm or gpg as \(CaCO_3\).

Hard water poses large problems in the oil patch, especially in steam generation.  Produced water is typically very hard and, if untreated, will deposit scale on the tubes within the steam generator lowering its efficiency.  If unchecked long enough, the tubes could become plugged and cause operability of the generator to be affected.