Sewage Treatment Plants:

The sewage treatment plant or the STP is where chemical reactions are taken place. The smaller solid particles are made to settle down by centrifugation. Most of the STPs convert the solid waste that settles down into methane gas by means of sludge digesters. The methane gas produced is used as an energy source for the treatment plants. Other STPs store the sludge residue within the plant itself.

Chennai is separated into five zones- Kodungaiyur (1, 2), Koyambedu (3), Nesapakkam (4) and Perungudi (5). Each zone has 3 STPs and so in total, Chennai has 12 STPs.

Treated water:

The water that is left behind gets treated with chlorine and is then released into the water bodies of Chennai- Cooum, the Buckingham Canal, and the Adyar River. It is fully taken care to ensure that the released water does not disrupt the water bodies.