What characterizes the 'activated sludge' process in wastewater treatment?

The activated sludge process is a biological treatment method used in wastewater management that primarily relies on microorganisms to degrade organic pollutants. During this process, aerated tanks facilitate the growth of bacteria and other microorganisms that consume organic material present in the wastewater, effectively breaking it down into simpler compounds, which can then be further treated. This decomposition process not only reduces the biological oxygen demand (BOD) of the wastewater but also converts harmful substances into less harmful forms.

The presence of microorganisms in a mixed liquor, which is a combination of wastewater and activated sludge (the concentrated biomass of microorganisms), is essential for the effectiveness of this method. When the mixture is aerated, the oxygen supplied supports the respiration and metabolic activities of these organisms, promoting more efficient treatment of the wastewater. The outcome is a significant reduction in the concentration of organic pollutants, making the treated water safer for discharge or further processing.

The other options involve processes that are not characteristic of the activated sludge method. Chemical filtration is a different approach meant for specific contaminants, while heating wastewater is not a standard process for organic matter breakdown but rather used in some industrial applications. Additionally, filtering out heavy metals typically involves different treatment technologies, such as chemical precipitation, not the biological methods employed in the activated sludge process.