What is the primary purpose of collecting influent composite samples at a POTW?

The primary purpose of collecting influent composite samples at a publicly owned treatment works (POTW) is to measure chemical oxygen demand (COD). COD is a critical parameter in wastewater treatment because it provides an estimate of the organic matter present in the wastewater. This information is valuable for evaluating the strength of the incoming wastewater, which helps treatment facilities determine the appropriate treatment process and adjust operational parameters accordingly.

Understanding the COD levels allows operators to anticipate the treatment system's performance, including the amount of oxygen required for efficient biological treatment processes. By monitoring COD, a POTW can manage the treatment process more effectively, ensuring compliance with environmental regulations and protecting water quality in receiving waters.

While monitoring flow rates, assessing solids concentration, and evaluating nutrient levels are also important aspects of wastewater management, the measurement of chemical oxygen demand directly relates to understanding the organic loading entering the treatment system, making it a primary focus when collecting influent composite samples.