Sewage Treatment Plant (STP)

Sewage Treatment Plants are used to remove contaminants/sewage waste from households, commercial buildings and sometimes even get an inflow of commercial wastewater too.

Primary Treatment

This stage of treatment involves the movement of wastewater into the clarifiers. The wastewater flows sluggishly in the settlement basins. It is the design of these tanks that result in settling, that is, the organic solid matter collects at the bottom of the tank while the lighter matter floats to the top becoming easier for removal.

The organic matter that settles at the bottom is called a primary sludge blanket. After few hours have passed, the settled sludge in the clarification tanks moves into aeration basins for  activated sludge process.

Secondary Treatment

Treatment in the secondary stage employs aerobic aeration. Aeration basins contain aerators, these have a system of pipes or tubes attached to them. They are made of ceramic or rubber membranes that have small holes in them for air to pass through. When this air flows through the aerators, the small holes present, turn them into bubbles and they get mixed with the water column. This interaction of the oxygen with the bacteria in the sewage results in the bacteria digesting the organic matter that gives wastewater the characteristic appearance and smell.

Tertiary Treatment

Wastewater is passed through sand filters, which remove very fine particulate matter. The photochemical process comes in after this, where the water flows under ultraviolet (UV) lights, which eliminate any bacteria and viruses as well as remove any infections.