Sewage treatment plant
Also called: STP, Used water treatment · Topic: Geographical Issues: Pollution, Urban Waste, Slums and Land Degradation · NCERT: Beyond NCERT
Meaning
A sewage treatment plant (STP) cleans dirty water from homes and towns before that water goes back into a river, lake or the sea. This dirty water is called sewage, or used water. The plant removes solids, breaks down organic matter with the help of microbes, and kills germs. This lowers the water's BOD (biochemical oxygen demand), which is the oxygen microbes need to break down the waste. Water fit for bathing should have a BOD of 3 mg/l or less.
STPs matter because domestic sewage is a main cause of river pollution in India. Building them is not enough, though. In 2020-21, Indian cities produced about 72,000 MLD (million litres a day) of sewage, but only about 28% of it was treated. In the same year, existing STPs ran at only 49% of their capacity. The reasons are that homes were not connected to sewers and plants were costly to run.
Example
Untreated sewage from Kanpur, Varanasi and Patna pollutes the Ganga in Uttar Pradesh and Bihar. The Namami Gange Programme, approved in June 2014, gives sewage treatment in Ganga towns the top priority so that waste is cleaned before it reaches the river.
Don't confuse with
- Effluent treatment plant (ETP): it treats industrial wastewater, such as the waste from Kanpur's tanneries, at the factory itself. An STP treats household and municipal sewage.