The turbidity of natural waters is caused by the presence of fine impurities caused by insoluble or colloidal inorganic and organic substances of various origins. Qualitative definition is conducted descriptively: weak opalescence, opalescence, weak, noticeable and strong turbidity. In accordance with the hygienic requirements for the quality of drinking water, the turbidity should not exceed 1.5 mg / dm3. Turbidity of water is determined by turbidimetric method (by attenuation of light passing through the sample).
Turbidimetric determination is intended for waters having a changeable composition and the shape of fine impurities. Without preliminary filtering of the sample with a turbidimetric method, not only colloidal but also coarser particles