A thick layer of toxic foam has covered Yamuna river in Delhi. The froth floating on the surface of the river is said to be a result of detergents containing high phosphate content. These detergents, reaching the river through untapped drains, are used in dyeing industries, dhobi ghats and households. Majority of the detergents in the country don’t have a certification by the ISO (International Organization for Standardization), which has capped the concentration of phosphates in the chemical substance.
— ANI (@ANI) November 4, 2020
These detergents and other organic matter gets deposited in the riverbed when the river is flowing normally. When more water is release upstream, it falls from a height on reaching the Okhla Barrage, leading to turbulence and churning which causes froth.
Experts believe another reason for the frothing could be the release of certain gases when a specific kind of bacteria become active in anaerobic conditions – when there is no or little oxygyen available.