Because the water contains suspended solids and colloidal particles, the original colorless and transparent water becomes turbid, and the degree of turbidity is called turbidity. The unit of turbidity is expressed in degrees, which is equivalent to 1mg SiO 2 (or 1 mgdiatomite) contained in 1L water, and the degree of turbidity is1degree. Diatomite suspension 1JTU = 1mg/L The turbidity displayed by modern instruments is NTU in turbidity unit, also known as TU. 1TU= 1JTU. In recent years, the turbidity standard prepared by urotropine-hydrazine sulfate is considered to have good reproducibility internationally, and has been selected as the unified standard FTU by various countries. 46660.88868888686