Tertiary treatment is the final stage of wastewater processing. The aim of the tertiary process is to raise the effluent quality to domestic and industrial standards or to meet special requirements for discharging into a body of water (river,lake, ocean, etc).
Wastewater is treated by a primary
process before the tertiary stage. Each stage removes contaminates by physical, biological, and chemical filtration; as the effluent progresses through each stage a combination of techniques are used to further refine its quality. Nitrogen and phosphorous accumulated throughout primary and secondary treatment promote growth of microorganisms and must be removed to prevent algal growth from shocking its discharge environment (Figure 1).
Figure 1: Nitrogen and phosphorous in wastewater support growth of microorganisms and aquatic plants.
Tertiary also treats pathogenic contaminates by disinfecting effluent before discharge.
Types of Tertiary Processes