Turbidity refers to the degree light scatters as it passes through a body of water. Turbidity factors include clay, silt, small organisms, plankton or microbes. High turbidity will affect the appearance of water, impede light from passing through water and further influence the photosynthesis of aquatic plants. It can also influence the growth and reproduction of fish and even cause them to suffocate. Moreover, high turbidity interferes with water disinfection as well. The measurement of turbidity is based on the principle of light scattering. A nephelometer is the measurement instrument and the commonly used measurement unit for turbidity is Nephelometric Turbidity Unit, NTU.