What is the function of activated sludge in sewage treatment?

The function of activated sludge in sewage treatment is primarily to decompose organic waste using microorganisms. Activated sludge refers to a mass of microorganisms that are employed in the aeration tanks of wastewater treatment facilities. As raw sewage flows into these tanks, the microorganisms in the activated sludge consume organic matter, breaking it down through metabolic processes. This biological treatment method effectively reduces the concentration of organic pollutants in the wastewater, making it less harmful before it is discharged into the environment or subjected to further treatment.

The process is facilitated through aeration, which provides oxygen to the microorganisms, enhancing their growth and activity. As the microorganisms consume the organic material, they multiply, creating a floc, or a mass of bacteria and other microorganisms that can be settled out in secondary clarifiers. The leftover sludge can then either be returned to the aeration tanks to maintain adequate microbial populations or removed for further treatment and disposal.

This biological decomposition is a critical step in the sewage treatment process, ensuring that harmful organic compounds are broken down and do not enter waterways or harm ecosystems. Other options, such as the removal of heavy metals, transportation of sewage, or chemical treatment, represent different processes or technologies utilized in wastewater management, but they do not encompass the specific role of activated sludge.