Suspended solids present in natural waters consist of particles of clay, sand, silt, suspended organic and inorganic substances, plankton and other microorganisms. The concentration of suspended particles is associated with seasonal factors and runoff regime and depends on the melting of snow, the rocks that make up the channel, and also from anthropogenic factors such as agriculture, mining, etc.
Suspended particles affect the transparency of water and the penetration of light, temperature, dissolved surface water components, the adsorption of toxic substances, as well as the composition and distribution of sediments and the rate of sedimentation. Water, in which there are many suspended particles, is not suitable for recreational use for aesthetic reasons. In accordance with the requirements for the composition and properties of water bodies of water at the points of domestic, drinking and cultural use, the content of suspended solids as a result of the discharge of sewage should not increase by more than 0.25 mg / dm3 and 0.75 mg / dm3, respectively.
For water bodies containing more than 30 mg / dm3 of natural mineral substances, the concentration of suspended solids in water is allowed to increase within 5% .
Determination of the amount of suspended particles is important to carry out when monitoring the processes of biological and physicochemical treatment of wastewater and in assessing the state of natural reservoirs. Coarse impurities are determined by the gravimetric method after they are separated by filtration through the "blue tape" filter (preferably for samples with a transparency less than 10 cm).