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.
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.
Meanwhile, Delhi's air quality was recorded in the "poor" category on Wednesday. The central government's Air Quality Early Warning System for Delhi said "fire counts" reduced in Punjab on Tuesday but were "still significantly high and are likely to impact the air quality in Delhi-NCR and northwest India".
The share of stubble burning in Delhi's pollution had dropped to 10 per cent on Tuesday due to a change in the wind direction. At 10 am, the city recorded an air quality index (AQI) of 279 as wind speed picked up.