What waste treatment element follows the primary settling tank in the activated sludge process?

In the activated sludge process, after the primary settling tank, the next significant component is the aeration tank. In this stage, the effluent from the primary settling tank enters the aeration tank, where it is exposed to air. This aeration process facilitates the growth of microorganisms that degrade organic matter and nutrients present in the wastewater. By providing a suitable environment for microbial activity, the aeration tank plays a crucial role in reducing biochemical oxygen demand (BOD) and improving the overall quality of the wastewater.

In contrast, the secondary settling tank comes after the aeration tank in this process, where the microorganisms are allowed to settle out after the biological treatment. The grit chamber, on the other hand, is an earlier component designed to remove heavier solids and grit from the incoming wastewater prior to primary treatment. Disinfection occurs later in the treatment process, typically after the secondary settling tank, to eliminate pathogens before the treated effluent is released into the environment or reused. Thus, the aeration tank is correctly positioned right after the primary settling tank in the sequence of the activated sludge process.