Tennessee Wastewater Operator Practice Exam

When DO concentrations are low, what happens to the growth of certain types of filaments compared to floc-forming bacteria?

1. Floc-forming bacteria grow faster

2. Both grow at the same rate

3. Floc former growth slows down

4. Filaments do not grow

The correct answer is: Floc former growth slows down

In wastewater treatment, dissolved oxygen (DO) concentrations play a critical role in the growth dynamics of different microorganism populations. When DO concentrations are low, floc-forming bacteria, which require adequate oxygen for their metabolic processes, experience a slowdown in growth. This is primarily because these bacteria are aerobic and depend on oxygen for their respiration and energy needs. In contrast, certain types of filamentous bacteria can thrive in low-oxygen environments, often utilizing anaerobic or microaerophilic conditions. As the floc-forming bacteria struggle to adapt to the reduced oxygen levels, filamentous bacteria can proliferate, often leading to a shift in the microbial population. This shift can result in the increased presence of filamentous organisms, which can affect the settling characteristics of the biomass, leading to issues such as bulking in the final effluent. The dynamic of competition for resources under varying DO levels highlights the importance of maintaining optimal oxygen conditions to ensure a balanced microbial community, which is essential for effective wastewater treatment.