What aspect of tertiary treatment can include UV disinfection methods?

Tertiary treatment refers to processes that further enhance the quality of effluent from secondary treatment, often making it suitable for reuse or discharge into sensitive environments. One key aspect of tertiary treatment is the polishing stage, which aims to remove remaining contaminants and improve water clarity.

UV disinfection methods are commonly employed in this polishing phase. They are effective in inactivating pathogens through the use of ultraviolet light, thus reducing the microbial load in the treated water. This makes the effluent significantly safer for discharge or reuse, particularly in applications such as irrigation and indirect potable reuse.

The other options are primarily focused on specific contaminant removal processes, which may not typically involve UV disinfection. For instance, the elimination of heavy metals involves chemical processes or adsorption; removal of phosphates and nitrates usually employs biological or chemical treatment methods; and reduction of suspended solids typically stems from sedimentation and filtration processes. Hence, the use of UV disinfection fits specifically and appropriately within the context of polishing rather than these other treatment objectives.