What is the oxygen requirement to consume 1 pound of ammonia?

The correct choice reflects the stoichiometric relationship between ammonia (NH₃) and its conversion to nitrate (NO₃⁻) in the aerobic treatment process, particularly in biological treatment systems. When ammonia is oxidized by microorganisms, it typically undergoes nitrification, a two-step process performed by different types of bacteria.

In the first step, ammonia is oxidized to nitrite (NO₂⁻), followed by the oxidation of nitrite to nitrate. The overall reaction for the complete nitrification of ammonia to nitrate requires a specific amount of oxygen.

The theoretical oxygen demand is calculated as follows: for every one pound of ammonia nitrogen, approximately 4.57 pounds of oxygen are needed to fully convert it into nitrate. This amount reflects the requirements for both steps of the nitrification process and takes into account nitrogen and oxygen balances in the reactions involved.

The answer of 4.57 pounds of oxygen aligns with established biochemical principles and empirical data related to wastewater treatment processes, particularly when examining the needs of microbial populations in systems designed to remove nitrogen from wastewater.