HYDERABAD: Millions of litres of untreated sewage water that enters water bodies in Hyderabad and other parts of Telangana not only contaminate the water or soil but also releases huge amounts of greenhouse gases (GHG) methane and nitrous oxide, which cause climate change, into the atmosphere.
To cut down GHG emissions from sewage water, the sewage should be treated in sewage treatment plants (STP) before being let into water bodies. Untreated sewage water reduces the dissolved oxygen content in the lake, killing any life-creating anaerobic environment and resulting in the formation of methane.
A study of the data at Nallacheruvu STP in Hyderabad by researchers from the University of Colorado, University of Minnesota and Humboldt State University in collaboration with International Water Management Institute points out that treating sewage water will help in cutting down GHG emissions drastically. The researchers found that after sewage is treated in an STP, methane emission is reduced to 219 milligrams of carbon dioxide equivalent per litre (mgCO2 Eq/l) from 643 mgCO2 Eq/l when sewage was not treated. Similarly, nitrous oxide emissions were seen to decrease from 187 mgCO2 Eq/l to 47 mgCO2 Eq/l.
It can be mentioned here that there are many studies which point out that treatment of sewage in STPs, where anaerobic method is used, results in the release of GHGs and emissions are lesser. STPs in Hyderabad use anaerobic method.However, the study conducted in Hyderabad pointed out that even if GHG emissions released due to treatment of sewage in STP and electricity utilised in the process are considered, the overall GHG emission is far less than what it would be if sewage water is left untreated. For example, methane emission, with a peak of 5,500 metric tonnes of carbon dioxide equivalent per year (MT CO2 Eq/year) when sewage water is not treated, decreased to about 3,500 MT CO2 Eq / year if the sewage is treated. This includes GHG emissions due to treatment process and electricity used.
The study conducted by scholars Leslie Miller-Robbie, Anu Ramaswami and Priyanie Amerasinghe in Hyderabad also pointed out that GHG emissions further decrease when the treated sewage water is used for farming.In Greater Hyderabad Municipal Corporation limits, around 700 million litres per day (MLD) of 1,450 MLD sewage water is let out without being treated. Across the state there are 73 urban local bodies, of which a majority do not have sewage treatment plants.