Question

How many stages does a sewage treatment plant have?

Answer 1

1. The wastewater treatment process is divided into three parts. They are:
   • Primary stage (mechanical process)
   • Secondary stage (biological process)
   • Tertiary stage (chemical process)
2. Primary Treatment: Sewage is carried by sewers to a sewage treatment plant. Here, the large solids, like leaves, rags, and plastic, are first separated by strainers or screens. Then, the sewage may pass through settlement tanks, where most of the suspended solids sink to the bottom. The solids that settle at the bottom of settlement tanks are referred to as primary sludge.
3. Secondary Treatment: The next step involves the action of microorganisms to break down organic materials. This may be done in aeration tanks, which are open tanks. The sewage in these tanks is treated by aerobic bacteria. The procedure is carried out in closed tanks or chambers.
4. Tertiary Treatment: Wastewater is sometimes treated further before being released into water bodies. It might go through sand filters or man-made ponds with reeds and other organisms that clear up certain dissolved chemicals.