Sewage treatment facilities use physical, chemical, and biological processes for water purification. The processes used in these facilities are also categorized as preliminary, primary, secondary, and tertiary. Preliminary and primary stages remove rags and suspended solids. Secondary processes mainly remove suspended and dissolved organics. Tertiary methods achieve nutrient removal and further polishing of wastewater. Disinfection, the final step, destroys remaining pathogens. The waste sludge generated during treatment is separately stabilized, dewatered, and sent to landfills or used in land applications.
How is wastewater processed at a sewage treatment facility?
What are the common pollutants present in wastewater?
Wastewater contains a wide range of contaminants. The quantities and concentrations of these substances depend upon their source. Pollutants are typically categorized as physical, chemical, and biological. Common pollutants include complex organic materials, nitrogen- and phosphorus-rich compounds, and pathogenic organisms (bacteria, viruses, and protozoa). Synthetic organic chemicals, inorganic chemicals, microplastics, sediments, radioactive substances, oil, heat, and many other pollutants may also be present in wastewater.