What is the main role of microorganisms in wastewater treatment?

The main role of microorganisms in wastewater treatment is to decompose organic matter and reduce biochemical oxygen demand (BOD). During the treatment process, these microorganisms, such as bacteria and fungi, feed on organic pollutants in the wastewater, breaking them down into simpler compounds. This process significantly reduces the concentration of harmful substances and the overall toxicity of the wastewater, making it safer for the environment when it is discharged or further treated.

Reducing BOD is critical because it measures the amount of oxygen that microorganisms will consume while decomposing organic matter. High BOD levels indicate a greater presence of organic pollutants, which can lead to oxygen depletion in receiving water bodies, adversely affecting aquatic life. Thus, effective microbial activity is essential for maintaining the health of ecosystems surrounding treated wastewater.

The other choices pertain to activities that are not the primary focus of microorganisms in wastewater treatment. While energy generation and sludge volume increases can occur as a byproduct of microbial activity, their main and most vital function remains the decomposition of organic matter. Similarly, although pH stabilization might be influenced by microbial processes, it is not their primary role.