Dissolved oxygen is an important parameter that determines health and rejuvenation capacity of any riverine ecosystem. The amount of dissolved oxygen in a river depends on atmospheric supply of oxygen, photosynthetic process, and oxygen-consuming metabolic and chemical processes.
If dissolved oxygen falls below the threshold of 2 milligram per liter, it can lead to mass killing of fish and harm other aquatic life.
The excessive amounts of human waste and toxic effluents that find their way into the Ganga river are not only polluting the water but also causing deficit of dissolved oxygen in the riverbeds in some of the most polluted stretches of the river, a new study has found.
The study was conducted during the summer months of three consecutive years – 2016 to 2018. Researchers chose a middle reach of the river (518 km) between Kanpur and Varanasi, which is considered to be the most polluted region.
The dissolved oxygen in subsurface water and at the interface of sediment and water was lowest in the Jajmau region in Kanpur, the most polluted stretch of Ganga where over 202 MLD of industrial effluents are directly released into the river.
High amount of organic carbon and oxygen-demanding chemicals such as ammonia, iron and manganese are flushed into the river from different sources. So far, most of the agencies focus mainly on biological oxygen demand (due to organic matter) including those in wastewater treatment.
The results suggest that for rejuvenation of Ganga, authorities should focus also on the reduction of chemical oxygen demand along with the biological oxygen demand to enhance the ecological assimilation capacity of the river.
This is a ‘India Science Wire’ Story; edited by Clean-Future Team