Bicarbonate Alkalinity

Definition - What does Bicarbonate Alkalinity mean?

Bicarbonate alkalinity is the alkalinity of water due to the presence of bicarbonate ions (HCO3). The bicarbonate ion is the main alkaline factor in almost all water. Bicarbonate alkalinity is introduced into water by CO2 dissolving carbonate-containing minerals.

Alkalinity control is important in boiler feed water, cooling tower water and in the beverage industry. Excessive alkalinity, for example, can interfere with dying of textiles and it defeats the acidity of fruit flavors in beverages.

Corrosionpedia explains Bicarbonate Alkalinity

The bicarbonate (HCO3) ion is the principal alkaline constituent in almost all water supplies. Bicarbonate alkalinity is the water alkalinity due to the presence of bicarbonate ions in water. Alkalinity is a measure of the capacity of water or any solution to neutralize or buffer acids.

Three carbonate species (H2CO3, HCO3- and CO32-) contribute to total alkalinity, their relative proportions being dependent on pH and temperature. At near-neutral values of pH, dissolved bicarbonate is dominant.

In addition to other sources, the effluent from wastewater treatment plants can add alkalinity to streams as the wastewater from industry and domestic uses contains carbonate and bicarbonate from cleaning agents and food residues.

Because the most important compounds in water that determine alkalinity are the carbonate and bicarbonate ions, carbonate ions are able to react with and neutralize two hydrogen ions (H+) and bicarbonate ions are able to neutralize H+ or hydroxide ions (OH-) present in water.

Since carbon dioxide and water are converted to carbonic acid in water, which provides carbonate and bicarbonate for buffering, bicarbonate alkalinity can be reduced by aeration, which reduces free carbon dioxide. It can also be treated by feeding acid to lower pH. Strong base anion exchange also reduces alkalinity.

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