Increase hardness and buffer capacity of drinking water

Process description

Raw waters, such as from reservoirs or wells in granite, sandstone or basalt areas, can be very soft (not infrequently below 3 °dH) and therefore corrosive. The constantly increasing amounts of drinking water desalted by reverse osmosis or distillation also have very low buffering capacity and without further treatment are very corrosive. By increasing the hardness to at least 3 °dH, corrosion in the pipe networks and at the consumer can be avoided. In practice, the degree of hardness is set to a value of up to 8 °dH in order to be able to mix drinking water from several waterworks into the distribution network.

Gas application

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 such a way that no scale precipitation occurs at the injection site.is precipitated.

In smaller waterworks, the increase of hardness is often achieved by filtration over a marble filter.

 CaCO_3(s) + CO₂ + H₂O ⇔ Ca²⁺ + 2 HCO₃^-

The CO₂ required for hardening is added to the water prior to filtration.

Benefits:

• No corrosive water
• Low operating costs
• No scale formation

Messer solution

For the rapid and complete dissolution of CO₂, Messer supplies diverse, widely tested technologies, varying from fine-bubble injection directly into the main flow to complete dissolution in a side stream under hydraulically defined conditions. In each project, we specify and offer injection technology that best fits the local conditions. Additionally, we calculate the required CO₂-dose