What does NTU measure in water quality testing?

NTU, or Nephelometric Turbidity Units, is a measurement used in water quality testing to quantify the amount of light scattered by particles suspended in a water sample. This scattering of light occurs when light beams pass through the water, and the particles present cause the light to deviate from its original path, resulting in turbidity.

Turbidity is an important indicator of water quality because it can affect aquatic life, water treatment processes, and the overall health of the water supply. The greater the concentration of suspended particles, the higher the turbidity levels—that is, more light is scattered, resulting in higher NTU readings. Monitoring turbidity is essential, especially in drinking water systems, as it can directly correlate with the presence of pathogens and other contaminants, potentially compromising safety if not managed properly.

The other options do not accurately reflect what NTU measures. The chemical composition of water refers to the specific substances present but is not associated with turbidity. The temperature of water is a separate parameter measured using different instruments, and while NTU can indirectly indicate the potential for bacteria presence by indicating higher turbidity, it does not measure bacteria directly.