Which method is commonly used to reduce the BOD in wastewater?

The activated sludge process is a widely used method for reducing biochemical oxygen demand (BOD) in wastewater. This process involves aerating the wastewater to promote the growth of microorganisms that consume organic matter, which is a significant contributor to BOD levels. As these microorganisms metabolize the organic pollutants in the wastewater, they multiply, forming a floc that settles out during the subsequent clarification step.

The efficiency of the activated sludge process in reducing BOD is largely due to the combination of aeration and the growth of these aerobic bacteria, which thrive in the oxygen-rich environment created during the aeration phase. This method not only effectively reduces BOD but also helps in removing other harmful substances from the wastewater, making it a crucial step in many wastewater treatment plants.

In contrast, chemical coagulation and filtration methods may be used in treatment processes but do not specifically target the biological decomposition of organic material that contributes to BOD. Aerobic digestion, while effective in stabilizing organic waste and reducing volume, typically occurs after the main treatment processes, so it's not the primary method used for the initial BOD reduction in wastewater treatment.