In what units is turbidity expressed?

Turbidity is expressed in Nephelometric Turbidity Units (NTU) because this unit is specifically designed to quantify the cloudiness or haziness of a liquid caused by large numbers of individual particles that are generally invisible to the naked eye. The measurement is based on the scattering of light, which is how turbidity is assessed in a laboratory setting.

When light is passed through a sample, particles in the water scatter this light, and the amount of light scattered at a specific angle is measured to give a direct indication of turbidity. This method is standardized, making NTU a universally accepted unit for describing turbidity levels in water quality assessments.

Other units like parts per million (ppm) or milligrams per liter (mg/L) are used for different types of substances or measurements in water, such as concentrations of solutes or contaminants but are not suitable for measuring turbidity effectively. Standard units may refer to different measurement systems and do not specifically define turbidity. Therefore, Nephelometric Turbidity Units are the correct and most specific measure for assessing water turbidity.