What are the steps of wastewater treatment?

1. Screening: The wastewater is passed through a screen to remove large solid particles like rags, sticks, and stones that can damage the pumps or clog the pipes.
2. Primary Treatment: In this step, the wastewater is treated with chemicals, fats and oils are separated, and floating debris like leaves and twigs are removed.
3. Secondary Treatment: This is done in two stages. Firstly, anaerobic bacteria break down organic matter and suspended solids. Secondly, aerobic bacteria further break down these organic materials, converting them into carbon dioxide gas and water.
4. Tertiary Treatment: The clarified effluent is further treated to remove phosphorus and nitrogen, which helps reduce eutrophication of waterways.
5. Disinfection: The treated wastewater is then disinfected to kill disease-causing organisms. This is usually done with chlorine, ultraviolet light or ozone.
6. Sludge Treatment: The sludge produced from the primary, secondary, and tertiary treatments must be treated before it can be safely disposed of. This is done by aerobic or anaerobic digestion to reduce its volume and treat it to make it safe for disposal.