How much influent alkalinity is needed to ensure 65 mg/L in the effluent for a nitrification process with an influent ammonia concentration of 17.8 mg/L?

To determine the influent alkalinity required to achieve a specific effluent alkalinity in a nitrification process, you first need to understand the stoichiometry of the nitrification reaction. Nitrification is a two-step biological process that converts ammonia (NH3) into nitrate (NO3-). During this conversion, alkalinity (often measured in mg/L of CaCO3) is consumed because hydrogen ions (H+) are produced, which can lead to a decrease in pH if not balanced by adequate alkalinity.

In this scenario, the desired effluent alkalinity is 65 mg/L, and the influent ammonia concentration is 17.8 mg/L. To maintain this required alkalinity during the process, it’s necessary to calculate how much influent alkalinity is needed to buffer the system adequately.

The calculation typically follows the principle that for every milligram of ammonia nitrogen (NH3-N) oxidized, approximately 7.14 mg of alkalinity (as CaCO3) is consumed to account for the formation of nitrate and the resultant impacts on pH. This is crucial for ensuring that biological nitrification occurs effectively without dropping the pH too low.

When calculating the total influent alkalinity needed, you would utilize