What are the three main stages of wastewater treatment?

The three main stages of wastewater treatment are primary treatment, secondary treatment, and tertiary treatment.

Primary treatment is the initial phase where physical processes are employed to remove large solids and particulates from wastewater. This typically involves screening and sedimentation, allowing heavier solids to settle at the bottom of a treatment tank.

Secondary treatment focuses on the biological processes that help degrade dissolved organic matter. In this stage, microorganisms consume organic pollutants, resulting in a considerable reduction of biochemical oxygen demand (BOD) in the treated water. Processes may include activated sludge, trickling filters, or bio-towers, which enhance the breakdown of remaining contaminants.

Tertiary treatment is the final stage, designed to further improve water quality before it is released into the environment or reused. This stage may include advanced filtration methods, nutrient removal, disinfection processes (like chlorination or UV treatment), and other technologies aimed at removing residual pollutants and pathogens.

Understanding these three stages is crucial for effective wastewater management, ensuring that the treated water meets safety and environmental standards before discharge or reuse.