Tertiary treatment
- Slovak term: Slovenský termín
- As it relates to wastewater, tertiary treatment refers to the treatment steps added after the secondary treatment stage to remove specific constituents, such as nutrients, suspended solids, organics, heavy metals or dissolved solids (e.g. salts) (WHO 2006).
Explanation
Tertiary treatment refers to treatment processes downstream of secondary treatment, such as (a) additional solids removal by flocculation, coagulation and sedimentation and/or granular medium filtration; an (b) disinfection. When tertiary treatment processes are used, the overall sequence of wastewater treatment processes is generally described as "advanced wastewater treatment" (WHO 2006).
Tertiary treatment can sometimes be referred to as advanced treatment.
Example
High-rate processes are usually engineered systems built around complex infrastructure that have high flow rates and low hydraulic retention times. They usually include a primary treatment step to settle solids followed by a secondary treatment step to biodegrade organic substances, and they may include tertiary of advanced processes for the removal of specific contaminants (WHO 2006).
These systems are often expensive, especially when tertiary treatment processess are required to meet microbial reduction targets (WHO 2006).
References
- WHO (2006). Guidelines for the safe use of wastewater, excreta and greywater. Volume 2: Wastewater use in agriculture
