In the activated sludge process, which components must be maintained in optimum balance?

• A. Oxygen supply
• B. Microbial population
• C. All of these
• D. Temperature only

Answer: (C)

In the activated sludge process, steady performance comes from balancing three interacting factors: oxygen availability, the size and activity of the microbial population, and temperature. Oxygen must meet the microbes’ demand for oxidizing the organic matter; too little slows degradation and can lead to poor treatment, while too much wastes energy and can disrupt the process. The microbial population—essentially the biomass present—has to be kept at the right level to match the substrate load and the available oxygen; too few microbes underutilize the treatment capacity, and too many increase oxygen demand and can cause settling problems. Temperature affects how fast the microbes work and how much oxygen can dissolve in water; optimal temperatures keep vital metabolic rates high without stressing the organisms, whereas extreme temperatures slow activity or harm biomass. Because these factors influence each other, maintaining them in optimum balance is crucial for a stable, efficient activated sludge system.