VSS
Volatile Suspended Solids

VSS -  Volatile Suspended Solids

The Volatile Suspended Solids (VSS) is a important characteristic measured to follow biomass growth in full-scale biological wastewater treatment systems.

Because biomass is mostly organic material, an increase in biomass can be measured by Volatile Suspended Solids (VSS) or particulate COD (total COD minus soluble COD). Other parameters that are used to indicate biomass growth are protein content, DNA, and ATP, a cellular compound involved in energy transfer. Of these growth measurement parameters, VSS is the parameter used most commonly to follow biomass growth in full-scale biological wastewater treatment systems because its measurement is simple and minimal time is required for analysis. It should be noted that the VSS measured includes other particulate organic matter in addition to biomass. Most wastewaters contain some amount of nonbiodegradable VSS (nbVSS) and possibly influent VSS that may be slowly degraded in the biological reactor. These solids are included with biomass in the VSS measurement. Nevertheless the VSS measurement is used as an apparent indicator of biomass production and also provides a useful measurement of reactor solids in genaral.

source: Metcalf and Eddy page 567