Tennessee Wastewater Operator Practice Exam

How does pH affect the AOB?

1. It increases the availability of NH3

2. It has no effect on AOB

3. It decreases the availability of NH3

4. It increases the growth rate of AOB

The correct answer is: It decreases the availability of NH3

The pH level of wastewater significantly influences the availability of ammonia (NH3), which is crucial for the growth and activity of ammonia-oxidizing bacteria (AOB). A lower pH (more acidic conditions) typically converts more ammonia into ammonium ions (NH4+), reducing the availability of NH3. AOB primarily utilize ammonia as their energy source, so when the pH is lower, the amount of un-ionized ammonia decreases, making it less accessible for these bacteria. The correct answer indicates that as pH decreases, the availability of NH3 also decreases, which potentially limits the growth and activity of AOB. Understanding this relationship is vital for optimizing conditions in waste treatment processes, where maintaining an appropriate pH can influence the efficiency of ammonia conversion to nitrate through the activities of AOB.