How is the efficiency of aerobic treatment typically measured?

The efficiency of aerobic treatment is best measured by the reduction in biochemical oxygen demand (BOD). BOD is a key indicator of the organic matter present in wastewater, representing the amount of oxygen that microorganisms will consume while decomposing organic matter under aerobic conditions.

When evaluating the performance of an aerobic treatment system, a significant decrease in BOD indicates that the process is effectively breaking down organic pollutants and thus shows the ability of the treatment system to remove contaminants. A lower BOD level in the treated effluent signifies that the wastewater has undergone successful treatment and is more suitable for discharge into receiving waters or for further processing.

Other factors like residual sludge, clarity of the effluent, and nitrogen levels may provide some insights into the treatment system's performance, but they do not directly measure the organic loading or the effectiveness of the aerobic treatment in terms of how much organic matter has been decomposed. Therefore, focusing on BOD reduction gives a clear, quantifiable view of treatment efficiency.