What is the activated sludge process?

The activated sludge process is a biological wastewater treatment method where microorganisms in aerated tanks consume organic matter from wastewater. Air is supplied to maintain aerobic conditions and keep biomass suspended. The mixture flows to secondary clarifiers where biomass settles, and part is returned as return activated sludge (RAS) to maintain microbial population. It achieves 85-95% BOD removal and is widely used for municipal wastewater treatment.