Tennessee Wastewater Operator Practice Exam

What is the primary method of ammonia removal in a facultative pond with a pH of 8.5 and an abundant green algae presence?

1. Denitrification

2. Volatilization to atmosphere

3. Nitrification

4. Absorption by algae

The correct answer is: Volatilization to atmosphere

The primary method of ammonia removal in a facultative pond with a pH of 8.5 and abundant green algae is volatilization to the atmosphere. At a higher pH, like 8.5, ammonia exists mostly as ammonia gas (NH3) rather than as ammonium ion (NH4+). This gaseous form readily escapes into the atmosphere, especially in conditions that favor its volatilization, such as a warm environment and continuous mixing due to wind or water movement. In this specific scenario, the presence of abundant green algae contributes to the overall dynamics of the pond. While algae can participate in nutrient uptake, the high pH shifts the balance significantly toward gaseous ammonia, making volatilization the most effective removal mechanism. The efficiency of this process increases with surface turbulence and increased exchange with the atmosphere. While processes like denitrification, nitrification, and absorption by algae may contribute to ammonia dynamics in different contexts, they are not the primary removal mechanism in a facultative pond under the described conditions. Denitrification, for instance, mainly occurs in anoxic environments and would not significantly factor into the removal of ammonia in this aerobic setting.