What does the threshold odor number (TON) represent?

The threshold odor number (TON) is a measure used to determine the intensity of odors in water. It specifically quantifies the number of dilutions required for a water sample to lose its distinct odor, meaning it becomes odorless. This is significant in water quality assessments because odor can indicate the presence of contaminants or substances that may affect the potability or aesthetic quality of the water.

When water is diluted to the point where no odor can be detected, that dilution factor represents the TON. A higher TON indicates a lower odor intensity, while a lower TON suggests a stronger odor presence. Recognizing the importance of TON helps operators understand the quality of the water they are managing and ensure it meets regulatory standards for consumption.

Other choices relate to different aspects of water quality but do not accurately describe the purpose of TON. For instance, while the maximum permissible odor in drinking water is an important consideration, it pertains to regulatory limits rather than the measurement process that we see with TON. Similarly, the number of dilutions for tastelessness would imply a measurement of taste rather than odor, and water acidity is assessed using a completely different parameter (pH) unrelated to odor measurement.