A total of 48,000 kilograms of defoamer chemical was used in Yamuna over 63 days between October and December last year, as per Delhi Jal Board’s response to a question raised in the Delhi legislative assembly. The board further mentioned that around ₹80 lakh was spent on the procurement of chemicals in the drive to remove froth near Kalindi Kunj.
“At Kalindi Kunj, the chemical dilution was carried out in a 1:10 ratio, as per the prevailing practice in the last three years, based on the assessment of foam quantity and water quality. In addition, the use of chemicals was kept to a minimum, and mechanical methods such as the froth arrester system and aeration by boat (for froth rupture) were used for foam control,” the DJB has said in the response.
Notably, use of defoamer chemicals in anti-froth drives has previously been criticized by the Bhartiya Janata Party (BJP) while it was in opposition. Delhi witnesses an annual controversy around the festival period when images of devotees standing in glacier-like froth chunks during Chhath Puja go viral.
On being askedif the water samples were being tested during the 63-day anti-froth drive, the DJB said, “The on-site temporary lab was removed the day after Chhath festival. But the samples continued to be tested at the Okhla laboratory.”
Soap-like surfactant molecules in the polluted waters turn into froth as a result of falling from a height at the nearby Okhla barrage. The issue worsens during the winter months when the temperature drops and the froth bubbles become much more stable. The surfactant molecules are produced as a result of biological, physical and chemical causes—detergents and surfactants in untreated domestic sewage, pollutants from industries and dhobi ghats, as well as materials released by decomposition of dying water hyacinth weeds in the Okhla barrage.
It was also the longest-ever anti-froth drive in Yamuna.
On December 16, a Yamuna activist wrote to LG VK Saxena and Delhi government, flagging excessive usage of defoamers in the Yamuna for a prolonged period. In the letter, activist Pankaj Kumar said that in previous years, defoamers were used only for a brief period around Chhath Puja, but this year, its usage had continued from October 15 till date – spanning nearly 60 days, which can have long-term adverse impacts on the river’s ecology and its aquatic life.
Official on condition of anonymity said that in previous years 12-15 tonnes of chemical has been used-- making the chemical use in 2024 three to four times higher than the previous years.
Interestingly, the 63 days trend also shows that more quantum of defoamers was being sprinkled when the foam levels were less during October 15-November 15 period when the flow in the river was better due to larger quantities of water being released from Hathnikund barrage. The daily utilisation decreased when the frothing increased later.
Kumar added that besides harming the aquatic life, “constant spraying will cause reduced oxygen transfer due to hydrophobic films on the water surface, leading to oxygen depletion, disruption of natural microbial activity, and accumulation of non-biodegradable silicone oils and silica particles in sediments, altering soil chemistry and harming benthic organisms”.