Oddly, one of the most frequently recommended
treatments for high pH—sodium
bicarbonate (also called bicarbonate
of soda or baking soda)—is the least
effective. Sodium bicarbonate reduces
high pH in water because it neutralizes
either acids or bases. (Compounds with
this property are called amphoteric.)
Sodium bicarbonate is, however, a weak
acid and large amounts must be added
to significantly reduce pH, especially in
waters with high total alkalinities (Table
1). For example, if water has a total
alkalinity of 200 mg/L as CaCO3 and
a pH of 10.0, then adding 100 mg/L of
sodium bicarbonate will reduce the pH
to only about 9.9. At this rate, a 2-acre
pond that is 4 feet deep would need
about 270 pounds of chemical per acrefoot,
or a little more than 2,000 pounds.
The same amount of sodium bicarbonate
(100 mg/L) added to water with an
initial alkalinity of 50 ppm as calcium
carbonate will reduce pH to about 9.6.
Oddly, one of the most frequently recommendedtreatments for high pH—sodiumbicarbonate (also called bicarbonateof soda or baking soda)—is the leasteffective. Sodium bicarbonate reduceshigh pH in water because it neutralizeseither acids or bases. (Compounds withthis property are called amphoteric.)Sodium bicarbonate is, however, a weakacid and large amounts must be addedto significantly reduce pH, especially inwaters with high total alkalinities (Table1). For example, if water has a totalalkalinity of 200 mg/L as CaCO3 anda pH of 10.0, then adding 100 mg/L ofsodium bicarbonate will reduce the pHto only about 9.9. At this rate, a 2-acrepond that is 4 feet deep would needabout 270 pounds of chemical per acrefoot,or a little more than 2,000 pounds.The same amount of sodium bicarbonate(100 mg/L) added to water with aninitial alkalinity of 50 ppm as calciumcarbonate will reduce pH to about 9.6.
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