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Prevention of scale formation

Process description

Drinking water of good quality should neither be corrosive nor form scale. For this purpose, the pH of the water must be balanced to the calcium content in the water (see figure below). However, some treatments in the waterworks may cause the pH value in the water to rise above this equilibrium value. These equilibrium shifts occur, for example, after intensive aeration of ground water or after softening with rapid decarbonisation. The result is the formation of scale on downstream filters, pipelines and valves in the waterworks, or the pipeline network to the customers. To prevent this, pH control with acid is required.

Gas application

CO2 is the acid of choice for drinking water treatment. Dissolved in water, CO2 reacts as a weak acid that is excellently suited for the precise adjustment of the pH value of drinking water.

The figure above shows the typical flat neutralisation curve with weakly acidic carbon dioxide compared to a strongly acidic mineral acid. The flatter curve with CO2 shows that even in the vicinity of the neutral range, carbon dioxide addition only causes gradual, relatively small pH changes. As a result, hyper-acidification, such as occurs frequently with the use of mineral acids, is excluded. Elaborate control technology can also be dispensed with.

Advantages

  • Safe and simple pH control; hyper-acidification is not possible
  • No handling of dangerous, aggressive acids
  • No corrosion of surrounding plant technology
  • No increase in salt content; relevant for the chemical corrosion properties of the drinking water  
  • No investment costs for acid storage
  • Low operating costs

Messer solution

For the rapid and complete dissolution of CO2, Messer supplies diverse, 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 each project, we specify and offer the injection and control technology that best fits the local conditions. Additionally, we calculate your CO2-demand.