In biological wastewater treatment, what is the main role of microorganisms?

In biological wastewater treatment, the main role of microorganisms is to break down organic matter. These microorganisms, including bacteria, fungi, and protozoa, utilize organic compounds in wastewater as a source of energy and nutrients. Through various metabolic processes, they convert complex organic materials, such as sewage and food waste, into simpler substances, effectively reducing the concentration of harmful pollutants.

This biological degradation is essential in treating wastewater, as it helps to stabilize the organic material and convert it into biomass and inorganic byproducts that can be more easily managed and removed from the water. The efficient breakdown of organic matter not only helps in reducing odors and the potential for disease but also contributes to the overall effectiveness of the treatment process.

While aeration, removal of dissolved solids, and nutrient provision are important components of wastewater treatment systems, they serve different purposes. Aeration provides oxygen for aerobic microorganisms, removal of dissolved solids focuses on separating particulates from the water, and nutrient provision ensures that microorganisms have the necessary elements for growth and activity. However, the primary function of those microorganisms is indeed the breakdown of organic matter, making option B the correct choice.