Wastewater purification is the process of removing contaminants from used water so it can be safely discharged into the environment or reused. Main stages1. Preliminary treatment - Removes large debris like sticks, rags, and grit. - Uses screens and grit chambers.2. Primary treatment - Settles out suspended solids in primary clarifiers. - Removes some organic matter and floating oils/grease.3. Secondary treatment - Uses microorganisms to break down dissolved and fine organic pollutants. - Common methods: activated sludge, trickling filters, oxidation ponds.4. Tertiary (advanced) treatment - Removes remaining nutrients, pathogens, and trace pollutants. - May include filtration, nutrient removal, disinfection, membrane systems, or activated carbon.5. Sludge treatment - Handles solids removed during treatment. - Can include digestion, dewatering, drying, and disposal or reuse. Common purification methods- Physical: screening, sedimentation, filtration- Biological: aerobic and anaerobic digestion, activated sludge- Chemical: coagulation, flocculation, pH adjustment, chlorination Goals- Protect public health- Prevent water pollution- Enable water reuse- Recover useful resources such as biogas, nutrients, and reclaimed waterIf you want, I can also give you:- a simple diagram- a short exam answer- or a detailed explanation of each treatment stage