activatedsludge

Activated sludge is a biological wastewater treatment process that uses a microbial culture to remove pollutants. In this system, wastewater is aerated in a tank containing a flocculent suspension of microorganisms. These microorganisms consume the organic matter in the wastewater as food, converting it into carbon dioxide, water, and new microbial cells. The mixed liquor, a combination of wastewater and activated sludge, is then sent to a settling tank. Here, the activated sludge flocs settle out by gravity, and the clarified effluent is discharged. A portion of the settled sludge is returned to the aeration tank to maintain a sufficient population of microorganisms for treatment, a process known as sludge recycling. The excess sludge removed from the system is called waste activated sludge. This process is highly effective in reducing biochemical oxygen demand (BOD) and suspended solids in wastewater. Factors such as aeration rate, temperature, and the sludge age (the average time a microbial cell remains in the system) are critical for optimizing the performance of activated sludge processes. Variations of the activated sludge process exist, including extended aeration, sequencing batch reactors (SBRs), and membrane bioreactors (MBRs), each offering different advantages in terms of footprint, treatment efficiency, and operational complexity.