Ontario Operator-in-Training (OIT) Practice Exam

In wastewater treatment, what is the significance of oxygen?

1. It is not used in the treatment process

2. It facilitates only anaerobic processes

3. It is required for certain treatment processes

4. It increases the water's pH

The correct answer is: It is required for certain treatment processes

Oxygen plays a vital role in wastewater treatment, particularly in biological treatment processes. The presence of oxygen is essential for aerobic microorganisms, which are beneficial bacteria that break down organic matter in the wastewater. These aerobic processes require oxygen to metabolize pollutants effectively, leading to the conversion of harmful substances into less harmful ones. This is crucial in reducing biochemical oxygen demand (BOD) and improving water quality before it is discharged or further treated. In contrast, the options focusing on the absence or mischaracterization of oxygen's role do not accurately reflect its importance. While some treatment processes can indeed occur without oxygen (anaerobic processes), aerobic treatment is a significant method used in many systems. Additionally, oxygen does not have a direct relationship with increasing the water's pH; rather, it contributes primarily to the biological degradation of pollutants in the wastewater. Understanding the role of oxygen helps to highlight the efficiency of aerobic treatment systems in achieving compliance with environmental regulations regarding effluent quality.