Suspended solids (SS) are particles of organic and inorganic matter held in suspension in water by turbulence. Total suspended solids (TSS) is a standard measurement used in water quality monitoring.
Suspended solids are particulate materials including silt, clay, organic matter, algae, and bacteria that remain dispersed in the water column due to turbulent flow. Total suspended solids (TSS) is measured by filtering a known volume of water through a standard glass fiber filter (typically 0.45 or 1.5 micrometers pore size), drying the residue, and weighing it. TSS concentrations in natural waters range from less than 1 mg/L in clear mountain streams to over 10,000 mg/L in heavily sediment-laden rivers during floods. Elevated TSS reduces light penetration, inhibiting photosynthesis by submerged aquatic vegetation, and can smother benthic habitats. Suspended solids serve as carriers for adsorbed pollutants including phosphorus, heavy metals, and pesticides, making their removal an important step in water treatment. The National Pollutant Discharge Elimination System typically sets TSS limits of 30 mg/L for secondary-treated wastewater effluent. Measurement of TSS is one of the most routine and widely reported water quality parameters, used in discharge monitoring, treatment plant performance evaluation, and ambient water quality assessment.