What is the typical BOD removal efficiency for activated sludge systems?

Activated sludge systems are biological wastewater treatment processes that utilize microorganisms to break down organic matter within the waste. The biochemical oxygen demand (BOD) is a critical parameter in assessing the performance of these systems, as it measures the amount of oxygen that microorganisms will consume while decomposing organic matter in water.

The typical BOD removal efficiency for activated sludge systems is high, generally ranging from 75 to 95 percent. This level of efficiency is achievable due to the optimal conditions that activated sludge systems provide for microbial growth and activity, including adequate aeration, appropriate retention times, and effective mixing. The process fosters a healthy population of microorganisms that can effectively metabolize the organic pollutants, leading to the substantial reduction of BOD levels in the treated effluent.

In comparison, the other choices represent lower removal efficiencies that do not reflect the typical performance of well-operated activated sludge systems. For instance, a 50-75 percent efficiency might be seen in less optimized processes or under certain operational challenges but does not represent the expected performance of a properly managed system. Generally, activated sludge systems are designed and operated to achieve higher BOD removal rates, making the 75-95 percent range a more accurate depiction of their capabilities.