Florida Wastewater Practice Test

Why is maintaining a proper DO level important in a biological treatment process?

1. To ensure proper chemical reactions

2. To support microorganism growth

3. To facilitate temperature control

4. To reduce odor emissions

The correct answer is: To support microorganism growth

Maintaining a proper dissolved oxygen (DO) level is crucial in a biological treatment process primarily because it supports the growth and activity of microorganisms. These microorganisms are essential for the breakdown of organic matter in wastewater. They rely on oxygen to perform aerobic respiration, which is the primary method by which they metabolize organic pollutants and convert them into carbon dioxide, water, and biomass. An optimal DO level promotes a healthy microbial community, allowing efficient treatment of wastewater. If the oxygen levels are too low, aerobic microorganisms may struggle to survive, leading to reduced treatment efficiency. This could result in incomplete degradation of organic material and potential release of harmful byproducts into the environment. While the other options may touch on important aspects of the wastewater treatment process, they do not directly relate to the core function of DO in supporting the microbial population essential for biological treatment. For instance, chemical reactions are indeed important but are not specifically targeted by DO levels; temperature control, while necessary for microorganisms, is influenced by other factors; and odor emissions are more associated with anaerobic conditions where foul-smelling gases are produced due to the lack of oxygen. Thus, the primary reason for maintaining appropriate DO levels is to ensure the microbial growth and activity vital for effective biological treatment.