What is the main purpose of tertiary treatment?

The main purpose of tertiary treatment is to further improve wastewater quality by removing remaining contaminants. After primary and secondary treatment processes, which focus on removing solids and organic matter, tertiary treatment acts as an additional step to address any residual pollutants. This stage often involves advanced filtration methods, chemical treatments, or biological processes specifically designed to eliminate pathogens, nutrients, and other contaminants that may not have been adequately removed in the earlier treatment stages.

As wastewater treatment regulations become more stringent, the importance of tertiary treatment grows, particularly in protecting water quality for discharge into sensitive environments or for reuse in irrigation and industrial processes. This level of treatment can lead to a significant reduction in pollutants such as nitrogen, phosphorus, and bacteria, which are critical for meeting effluent standards. Hence, option C directly aligns with the goal of achieving higher quality effluent that meets these health and environmental safety standards, making it the correct answer to the question.