The purpose of tertiary treatment is to provide a final treatment stage to raise the effluent quality before it is discharged to the receiving environment such as sea, river, lake, ground, etc., or to raise the treated water quality to such a level to make it suitable for intended reuse. This step removes different types of pollutants such as organic matter, SS, nutrients, pathogens, and heavy metals that secondary treatment is not able to remove. Wastewater effluent becomes even cleaner in this treatment process through the use of stronger and more advanced treatment systems. It includes sedimentation, coagulations, membrane processes, filtration, ion exchange, activated carbon adsorption, electro dialysis, nitrification and de-nitrification, etc. Tertiary treatment is costly as compared to primary and secondary treatment methods.

Need of Tertiary treatment

Tertiary treatment may be provided to the secondary effluent for one or more of the following contaminant further.

• To remove total suspended solids and organic matter those are present in effluents after secondary treatment.
• To remove specific organic and inorganic constituents from industrial effluent to make it suitable for reuse.
• To make treated wastewater suitable for land application purpose or directly discharge it into the water bodies like rivers, lakes, etc.