Which parameter is most critical in assessing the performance of a sewage treatment system?

Biochemical oxygen demand (BOD) is the most critical parameter in assessing the performance of a sewage treatment system because it measures the amount of oxygen that microorganisms will consume while decomposing organic matter in the water. A higher BOD indicates a greater presence of organic material, which means that the sewage treatment system must efficiently treat this material to prevent pollution and ensure that the effluent meets regulatory standards before discharge.

Monitoring BOD provides insight into the overall effectiveness of the treatment process. It helps determine how much organic pollution is in the influent and allows operators to adjust processes accordingly, ensuring that the treatment system is functioning effectively to reduce the organic load. Therefore, BOD serves as a key indicator of the health of the treatment process and its ability to remove contaminants.

While temperature, pH level, and total suspended solids (TSS) can influence the treatment process and are important parameters in their own right, they do not provide as direct a measurement of the treatment's success in reducing organic loads as BOD does. Instead, they can be seen as secondary metrics that can affect or be affected by the biological treatment processes that BOD evaluates.