ABSTRACT
In general, the main parameters or substances which need to be removed from wastewaters are suspended solids, soluble organic matter, heavy metals, toxic organic chemicals, nitrogen and phosphorus.
Suspended solids are usually measured as total suspended solids (TSS) and volatile suspended solids (VSS). The TSS are the total solids which are deposited on a filter of specified pore size (typically around 1 mm) and are composed of both organic and inorganic solids. The VSS are the fraction of the TSS which volatilise at a specified temperature, typically 550°C. The VSS are in general considered to represent the fraction of the TSS which is organic in nature. The difference between TSS and VSS is called fixed suspended solids (FSS), which is considered the inorganic fraction of the TSS. As an example, starch, cellulose or microorganisms contribute to the VSS, whereas calcium carbonate (CaCO3) is part of the FSS.
