What does the threshold odor number (TON) measure?

The threshold odor number (TON) is a critical measurement in water treatment that quantifies the concentration of odorants present in water. Specifically, it represents the dilution factor needed to reduce the intensity of odor to the point of non-detection. To determine the TON, water is diluted with odor-free water until the odor just becomes perceptible to a panel of trained assessors.

This method provides a numerical value that indicates how strong the odor is in the original sample. A higher TON value signifies that a greater dilution is required for the odor to become undetectable, which suggests that the original water sample has a stronger odor. Conversely, a lower TON indicates a more easily detectable odor. Therefore, the concept directly addresses odor levels in water, making it a crucial parameter in assessing water quality and ensuring that it meets health and aesthetic standards for consumption and distribution.

Understanding TON is pivotal for water treatment professionals who aim to maintain water quality and monitor changes in odor that could indicate contamination or changes in the water source. The other options do not relate to the measurement of odor intensity and thus are not relevant in this context.