What is UV254?

UV254 is a measurement of the amount of light absorbed by organic compounds, specifically aromatic, in a water sample.

How is UV254 measured?

Ultraviolet light at the 254 nm wavelength is passed through a quartz cell containing the sample water. The intensity of the attenuated light is measured with a sensor and divided by a pure water measurement before a logarithm is calculated. The measurement is reported as absorbance per path length (abs/cm).

Why is UV254 important?

UV254 is an important parameter for measurement throughout the drinking water treatment process. UV254 provides an indication of the concentration of organic matter, specifically those that contain aromatic rings or unsaturated bonds (double and triple) in their molecular structures.. Many organic compounds occurring naturally in the environment, such as humic substances, are aromatic and exist in high concentrations in surface water. These compounds are known to be a major precursor of DBP formation. Therefore, UV254 provides one of the best indications of a water’s potential to form DBPs upon chlorine addition and should be monitored throughout the treatment process to ensure organics are removed.

Where is UV254 measured?

  • Influent to drinking water treatment plant for source water quality fluctuations
  • Pre and post coagulation to optimize chemical dose for turbidity and organics removal
  • Pre and post carbon adsorption to monitor organics removal efficiency and optimize activated carbon dosing
  • Pre chlorination for DBP formation potential
  • Distribution system for general water quality and contamination events