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Reverse Osmosis Post-treatment: Neutralization / Remineralization


Why should Reverse Osmosis permeate water be remineralized?

Reverse Omosis is not efficient at removing dissolved carbon dioxide, so it passes through the membranes into the permeaste side and acidify the permeate stream by about 1 pH unit.

Moreover, RO is not selective process and if your feed water was low in calcium and magnesium compare to sodium, the permeate water will have very low concentration of calcium and magnesium.

Low mineralized water have few adverse effects:

- High corrosion potential
- Dietary deficiency causing risks of ischaemic heart and cerebrovascular disease (WHO, 2005a; WHO, 2006; Cotruvo, 2006)

The WHO recommends 10 mg/L of Magnesium and 30 mg/L of Calcium for drinking water.

Irrigation water should satisify EC vs. SAR conditions.

Remineralization processes:

Blend with clarified feed water + pH neutralization

CO2 addition + Calcite Limestone (CaCO3, MgO) percolation + Na2CO3

CO2 addition + Dolomite Limestone (CaCO3, MgCO3) percolation + Na2CO3

Addition of CaCl2 + NaHCO3


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