What percentage of organisms in activated sludge is composed of bacteria?

The correct answer indicates that approximately 95% of the organisms in activated sludge are composed of bacteria. This high percentage reflects the crucial role bacteria play in the wastewater treatment process.

Activated sludge is a mixture of microorganisms, primarily bacteria, which decompose organic matter in wastewater. These bacteria are essential for the biological treatment of sewage, as they metabolize the organic pollutants, facilitating their breakdown into simpler substances. The significant biomass of bacteria is key to effective treatment, as they not only help in reducing the biochemical oxygen demand (BOD) but also contribute to the removal of nitrogen and phosphorus.

While other microorganisms such as protozoa, fungi, and viruses may also be present in activated sludge, their populations are considerably smaller compared to bacteria. Each type of microorganism has a specific role in the treatment process, but bacteria dominate in terms of sheer numbers and activity level. Understanding this composition is important for wastewater operators, as the abundance of bacteria relates directly to the efficiency and performance of the activated sludge process.