How much alkalinity is returned to the Mixed Liquor Suspended Solids (MLSS) for each pound of nitrate used in the denitrification process?

The correct answer is based on the fundamental biochemistry of the denitrification process in wastewater treatment. When denitrification occurs, nitrate (NO3-) is converted to nitrogen gas (N2) under anaerobic conditions. This process requires a carbon source, and alkalinity plays a crucial role in maintaining the pH balance during the conversion.

For each pound of nitrate that is denitrified, approximately 3.6 pounds of alkalinity is returned to the Mixed Liquor Suspended Solids (MLSS). This figure arises from calculations that consider the stoichiometry of the denitrification reaction and the compensatory chemical processes that occur during the treatment.

Denitrification not only transforms nitrates but also impacts the overall buffering capacity of the system. The return of 3.6 pounds of alkalinity for every pound of nitrate helps to counteract any potential acidification that could take place as a result of microbial activity and the consumption of organic carbon during the denitrification. Thus, understanding this ratio is vital for operators to manage pH levels and ensure optimal conditions for microbial growth and treatment efficiency within the treatment process.