What alkalinity is roughly required to convert 1 mg/L of ammonia to nitrate?

• A. 3.0 ppm
• B. 10.0 ppm
• C. 2.0 ppm
• D. 7.2 ppm

Answer: (D)

Nitrification uses up buffering alkalinity as ammonia is oxidized to nitrate, releasing acidity. The stoichiometry works out to about 7.14 mg/L of alkalinity as CaCO3 being required for every 1 mg/L of ammonia-nitrogen oxidized to nitrate. So, to convert 1 mg/L of ammonia to nitrate, roughly 7.2 mg/L (ppm as CaCO3) of alkalinity is needed. That’s why 7.2 ppm is the best fit. The other values are not close to the required buffering amount for this nitrification load.