NTU stands for what measurement in water quality?

The correct interpretation of NTU in the context of water quality is Nephelometric Turbidity Units. This measurement specifically refers to the turbidity of water, which is an important parameter indicating the clarity or cloudiness of the water. Turbidity is typically caused by suspended particles such as clay, silt, and organic matter.

The turbidity is measured using a nephelometer, which quantifies the light scattered by the particles in the water. Higher NTU values indicate more turbid water, suggesting a higher concentration of suspended solids, which can influence water quality and aquatic life. Monitoring and controlling turbidity is crucial in various water treatment processes, as it can affect disinfection effectiveness and overall drinking water safety.

The other options refer to terms that are not standard measurements in water quality assessment, which is why they are not applicable in this context.