DISSOLVED SOLIDS

Dissolved solids in surface water come from the natural dissolution of rocks and minerals or from discharges from municipal or industrial sources. Dissolved solids are mainly composed of cations such as calcium, magnesium, sodium, and potassium; and the anions bicarbonate, carbonate, sulfate, and chloride. Excessively large concentrations of dissolved minerals in drinking water may result in physiological effects, unpalatable mineral tastes, and increased costs due to corrosion or the necessity for additional treatment.

Dissolved solids occur naturally in all surface water at varying concentrations. This variation is due to factors such as the chemical properties of drainage-basin soils and the minerals in deeper geologic strata. Groundwater may dissolve salts from marine sediments containing large salt deposits and then discharge them into surface water. The concentration of dissolved solids in surface water may also increase due to point-surface discharge. The total solids content of water can be determined indirectly by measuring both the suspended and the dissolved solids. The sum of the dissolved solids plus the suspended solids equals the total solids. The presence of solids in water can increase turbidity. Dissolved minerals such as magnesium and calcium contribute to the hardness of water.

Mark G. Robson

(see also: Sanitation; Water Quality; Water Treatment )

Bibliography

Koren, J., and Bisesi, M. (1995). Handbook of Environmental Health and Safety, 3rd edition. Boca Raton, FL: Lewis Publishers.

U.S. Geological Survey (1996). Occurrence of Dissolved Solids, Nutrients, Atrazine, and Fecal Coliform Bacteria During Low Flow in the Cheney Reservoir Watershed, South-Central Kansas. Available at http://www.ks.cr.usgs.gov/Kansas/pubs/reports/wrir.97–4153.html.