What is the definition of feed water in water treatment systems?

The definition of feed water in water treatment systems specifically refers to the untreated water that is introduced into the system for processing. This source is typically tap water or raw water that has not yet undergone any purification or treatment processes. It is the initial stage in the water treatment process, where various contaminants and impurities present in the water need to be removed to produce clean and safe drinking water or water suitable for other uses.

In this context, the other options represent different stages or sources of water but do not accurately define feed water. For example, water after treatment refers to the final product, while water sourced from wells or industrial water supply may be specific types of feed water but do not encompass the general definition that applies to all water entering treatment systems. Therefore, describing feed water as tap water before treatment captures its essence as the starting point for purification processes.