Alkalinity Supplementation in Ammonium Nitrogen Removal
Industrial processes that produce high ammonia loading in wastewater are common. Biological nutrient removal (BNR) systems employ sequential nitrification/denitrification to convert ammonium into harmless N2 gas.
In nitrification, aerobic nitrifying bacteria convert ammonia to nitrate:
Ammonia → Nitrite → Nitrate
Denitrification then uses microorganisms to convert nitrates to harmless N2 gas, in the absence of dissolved oxygen (DO). Nitrification produces acid, therefore alkalinity must be added – supplemented – to buffer the acids produced.
FloMag®H magnesium hydroxide slurry can be used to provide the 7.14 parts of alkalinity that are required for each part of ammonia to be removed. Alkalinity is the capacity of water to buffer or resist changes in pH in response to introduction of acid or base. Nitrification rates rapidly decrease as pH falls below 7.0, and stops at a pH of approximately 6.0.
FloMag®H magnesium hydroxide, Mg(OH)2, represents a good supplementation agent for nitrification due to its higher alkalinity per gallon, as compared with alternative alkalinity agents. Because alkalinity is released slowly, there are no large pH excursions to kill nitrifying microorganisms. Magnesium hydroxide provides both alkalinity and pH stability for the biological nitrification process.