Texas Wastewater Class B Practice Exam

What is one consequence of not maintaining appropriate dissolved oxygen levels?

1. Increased sludge production

2. Reduced efficiency of microorganisms

3. Lower water temperatures

4. Decreased flow rates

The correct answer is: Reduced efficiency of microorganisms

Maintaining appropriate dissolved oxygen levels in wastewater treatment processes is crucial for the efficiency of microorganisms that break down organic matter. Microorganisms, particularly aerobic bacteria, rely on dissolved oxygen to effectively metabolize organic materials in wastewater. If oxygen levels fall below optimal ranges, these microorganisms become less active and their efficiency in decomposition significantly reduces. This leads to incomplete breakdown of waste, resulting in higher concentrations of untreated materials in the effluent, which can adversely affect water quality and treatment efficacy. While increased sludge production can occur if microorganisms are stressed or if there is incomplete treatment, the direct and immediate impact of low dissolved oxygen is primarily on microbial efficiency. Other options, such as lower water temperatures and decreased flow rates, do not have a direct relationship with dissolved oxygen levels in the same way as microorganism efficiency does, making them less relevant in this context.