Images of Chhath Puja devotees taking a dip in Delhi’s Yamuna river amid clouds of foam issuing from the surface of the water, reminded many of Bengaluru’s Bellandur lake. In 2015, the foam on the lake’s surface caught fire prompting international headlines.
But even as Delhi suffers from another year of severe air pollution, pictures of devotees offering prayers amid toxic foam are an annual event. The frothing of the river is most visible in the 22-km stretch of Yamuna, flowing from Wazirabad and Okhla. This part of the river is less than 2 per cent of its length from Yamunotri to Allahabad, and accounts for around 80 per cent of the pollution load.
The Delhi government, however, deployed boats to remove the toxic foam formed over the Yamuna’s surface. But it was not just boats, as employees were assigned to sprinkle water to dissipate the toxic foam. An employee of the Delhi Jal Board made a video of the exercise. But does this really help removing the froth formed over the river.
Is froth over rivers normal?
According to a report by The Quint, all rivers form a thin layer of foam under normal circumstances. This is due to dead and decaying plants, which on decomposition, may not dissolve in water but break the surface allowing air to enter and create bubbles. All foam and froth, however, is not the same.
What is toxic foam then?
The presence of phosphates and surfactants in untreated sewage from Delhi, Haryana and Uttar Pradesh is a major reason behind frothing in the Yamuna. AAP leader and Delhi Jal Board vice-chairman Raghav Chadha said Haryana and Uttar Pradesh were releasing around 155 million gallons of untreated wastewater a day in the river through Najafgarh and Shahdara drains. “This water, containing a lot of organic waste, chemicals and detergents, falls from a height at the Okhla barrage leading to the formation of foam,” he said.
Why does the Yamuna produce toxic foam in October-November?
According to a report in The Indian Express, Sushmita Sengupta, senior programme manager of the water programme at Centre for Science and Environment (CSE), said water pollutants such as surfactants and phosphates from households and industries travel through the Yamuna all year. Since the flow of the river is less during winter months, the pollutants do not get diluted and form thick and toxic foam.
Sprinkling water — Is there any science behind it?
Not exactly. While a healthy river can clean itself with water diluting the presence of phosphates, the case is not so with the Yamuna.
But at a very basic level, Delhi Jal Board may not be completely wrong. The toxic foam containing high proportions of ammonia can be dissolved with exposure to water. A Univerity of Waterloo study found, “The relatively high solubility is attributed to the hydrogen bonding that takes place between the ammonia and water molecules. The dissolving of ammonia in water forms a basic solution. A small amount of the dissolved ammonia reacts with water to form ammonium hydroxide, which dissociates into ammonium and hydroxide ions. All of these processes are reversible.” But this does not directly imply that the toxic foam can simply be “washed away” as the solution will continue to remain in the Yamuna itself.
How harmful is toxic foam?
Foaming due to pollution can result in algae blooms and harm aquatic life due to low dissolved oxygen from decomposition processes. Bathing in or ingesting waters where frothing has been caused by pollution can lead to health hazards like itchy skin and eyes and gastrointestinal problems.
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