The effluent from secondary treatment systems primarily contains what type of material?

The effluent from secondary treatment systems is primarily characterized as transformed wastewater with lower pollutant levels. Secondary treatment, often involving biological processes, aims to significantly reduce the organic matter and nutrients from the wastewater, making it much cleaner than it was after primary treatment.

In this stage, microorganisms break down and consume organic pollutants, which lowers the biochemical oxygen demand (BOD) and total suspended solids (TSS). The result is an effluent that has substantially reduced levels of pollutants, allowing it to meet regulatory requirements for discharge into waterways or for further treatment processes.

Understanding this process clarifies the transformation that occurs during secondary treatment, distinguishing it from raw sewage, which has not undergone any treatment; solids, which would indicate leftover sediments; and untreated stormwater, which is entirely different and not related to the wastewater treatment process.