California Wastewater Treatment Operator Practice Exam 2026 – All-in-One Guide to Master Your Certification

Total Suspended Solids (TSS) in a wastewater treatment plant primarily come from both settleable and non-settleable solids found in the influent wastewater. However, non-settleable solids are particularly significant as they can remain suspended in the water column and contribute to the TSS levels that are measured in treatment processes.

Non-settleable solids include fine particles, colloids, and biological matter that do not readily settle out under normal gravitational forces. These solids can originate from various sources, including organic matter from food waste, dirt, and other inorganic particulates. Their presence can significantly affect the treatment process, as higher levels of TSS can influence the effectiveness of filtration and biological treatment methods.

While settleable solids are also a component of TSS, they do not remain suspended in the same way as non-settleable solids do, which is precisely why the focus is on the latter as a source. Microorganisms and algae can contribute to the overall biomass and organic content in the wastewater, but their direct link to TSS as a source predominantly pertains to non-settleable particles within the treatment spectrum.