Water

The initial phase of waste water treatment involves mechanical pre-treatment to remove any solids, settleable solids, suspended solids or floating substances.

The other aspect of initial wastewater treatment involves detoxification, i.e. the chemical removal of contaminants such as heavy metals, cyanides, hexavalent chromium, phosphates, etc. 

The secondary treatment phase involves the removal of organic pollutants. With the help of micro-organisms, organic contaminants such as BOD, COD, nitrogen and phosphate-containing compounds get converted to harmless residual substances.

Tertiary water treatment usually follows primary and secondary processing treatments, but can be applied directly to certain process waters.

Waste sludge is usually generated during primary and secondary processing. Solid impurities are separated, dissolved substances are insolubilized and precipitated and the excess biological sludge mass is discharged. To facilitate transport as well as make it safe for discharge, adequate sludge separation and concentration is necessary.