What is the role of microorganisms in secondary treatment?

Microorganisms play a crucial role in the secondary treatment of wastewater, primarily through the process of decomposition of organic pollutants. During this stage, a diverse population of bacteria and other microorganisms breaks down complex organic matter present in the wastewater into simpler substances. This biological treatment process is essential for reducing the biochemical oxygen demand (BOD) of the water, which measures the amount of oxygen needed by microorganisms to decompose organic materials.

As the microorganisms digest the organic pollutants, they convert them into carbon dioxide, water, and new cell mass, effectively cleaning the wastewater. This process not only helps in reducing the concentration of organic contaminants but also improves the overall quality of the water before it is released into the environment or further treated. The effectiveness of this microbial action is a fundamental aspect of secondary treatment, making it one of the most efficient and widely used methods in modern wastewater treatment plants.