What is defined as water flowing into a treatment plant that has not been treated?

The term that describes water flowing into a treatment plant that has not been treated is influent. Influents are typically composed of wastewater from various sources such as residential, industrial, and commercial facilities. Understanding influent is critical for wastewater treatment operations because it directly impacts the design, capacity, and effectiveness of the treatment processes in place.

Effluent refers to the treated water that exits the treatment plant and is usually released back into the environment or repurposed. Runoff pertains to water that flows over land surfaces and may carry pollutants into water bodies, but it is not specific to a treatment plant context. Sludge refers to the accumulated solids generated during the treatment processes, not the incoming water itself.