What unit is used to measure true color in water after filtration?

The correct answer is measured in NTU, which stands for Nephelometric Turbidity Units. However, true color in water is typically quantified using true color units rather than NTU. While NTU is primarily used to measure turbidity (which indicates the cloudiness of water), it is not the standard unit for measuring true color after filtration.

True color measurements are often reported in units such as PCU (Platinum-Cobalt Units) or in color units that reflect the actual color of the water sample. The misconception here stems from the broader concept of water quality where turbidity might be confused with color.

In summary, while turbidity is a crucial parameter assessed in water analysis, the appropriate unit for measuring true color is not NTU but rather units like PCU. This distinction highlights the varying metrics used in water quality analysis to accurately gauge different attributes.