revised_Application technology hardening in the Water utilities sector

Hardening with CO2 and lime

Adjusting hardness and buffer capacity


The natural water component CO2 is an indispensable auxiliary in the targeted hardening of drinking water. The most economical method for increasing water hardness is the use of lime milk or lime water with equilibrium amounts of CO2.


Ca(OH)2 + 2 CO2 ⇔ Ca2+ + 2 HCO3-

The injection of lime milk and CO2 must be designed in a way that overdosing is avoided in order to prevent precipitation of limestone.

In smaller waterworks the adjustment of hardness is often achieved by filtration over a marble filters.

 CaCO3(s) + CO2 + H2O ⇔ Ca2+ + 2 HCO3-

The CO2 required for hardening is added prior to filtration.


  • No corrosion
  • Low operating costs
  • No scale formation


For the rapid and complete dissolution of CO2, Messer supplies several widely tested technologies, varying from fine-bubble feed directly into the main water stream to complete dissolution in a side stream under hydraulically defined conditions. In a project we specify the feed method that fits the customer needs regarding local conditions best. If required Messer calculates the CO2-dosage as well.

revised_Customer process hardening in the Water utilities sector


Adjusting water hardness

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