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EXPLAINED: How The Yamuna Foams Up And What It Says About State Of Pollution In Delhi

The frothing in Yamuna is due to the release of effluents into the river (File photo: Reuters)

The frothing in Yamuna is due to the release of effluents into the river (File photo: Reuters)

The alarming regularity with which the Yamuna froths up in Delhi points to the heavy discharge of effluents into the river and can pose health hazards

The Delhi government has blamed UP and Haryana, while environmentalists point fingers at the discharge of effluents into the river. But the frothing of the Yamuna at Delhi seemingly continues annually in defiance of all announcements and efforts at combating it. Here’s what’s behind the dramatic presence of thick foam on the river.

What Is Behind The Foaming Of The Yamuna?

From dyes discharged by garment units to the release of industrial effluents, a variety of factors are blamed for the thick froth layer over the Yamuna’s waters. The passage past Delhi is said to mark the most polluted stretch for the river it flows down from Yamunotri to Allahabad.

The Delhi Pollution Control Committee (DPCC) had told the National Green Tribunal last year that the “presence of dhobi ghats, direct release of sewage containing phosphatic detergents, industrial effluents and the turbulence caused near the barrages" were the chief factors causing the foaming of the waters.

There are also reports that specifically blame the discharge by illegal denim dyeing units, said to be high in ammonia and phosphates compounds, for the frothing, which continues despite steps like a ban on the sale of soaps and detergents that do not meet Bureau of Indian Standards (BIS) norms in Delhi. Also, DPCC was asked by NGT to take action against the dyeing units with more than 150 of these having been served closure notices so far, reports add.

The Parliament was told last year that ammonia levels in the river had “increased to 1.8 ppm and ranges from Below Detection Limit (BDL) to 38.8 ppm for the year 2019".

How Do Effluents Find Their Way Into The Yamuna?

The Jal Shakti Ministry told Parliament earlier this year that the Yamuna has “almost no fresh water downstream of Wazirabad barrage in Delhi except monsoon season", pointing to “a critical path of 22km" in Delhi where 18 major drains discharge into the river.

It cited DPCC data to note that while the estimated sewage generation in Delhi is about 3,273 million litres per day (MLD), the installed sewage treatment capacity for the national capital was about 2,715 MLD, of which about 2,432 MLD is treated in Delhi. About 941 MLD of sewage thus finds its ways into the river through various drains, it added.

It also pointed out that while there are 13 Common Effluent Treatment Plants (CETPs) of 212 MLD capacity for 17 industrial clusters in Delhi, “all these CETPs are non-compliant".

Amid the latest froth attack on the Yamuna, AAP MLA and Delhi Jal Board (DJB) Vice Chairman Raghav Chadha said the pollutants causing it can be traced to the neighbouring UP and Haryana.

“The foam in the Yamuna is at Okhla Barrage area, which comes under Uttar Pradesh irrigation government, it’s Uttar Pradesh government’s responsibility. But like every year, they failed this year too. The polluted water is not Delhi’s, it’s a ‘gift’ to Delhi by Uttar Pradesh and Haryana government," said Chadha, adding that about 105 MGD of effluents from Haryana and about 50 MGD from the Ganga in UP had merged at Okhla Barrage, spurring the formation of froth.

How Hazardous Is The Froth?

Accumulation of froth on rivers and water bodies is reported in cities across India, including in Chennai and Bengaluru. While experts point out that human activity and release of pollutants is not the only factor behind the formation of foam, the occurrence in Indian cities is overwhelmingly linked to toxic discharge.

Environmentalists say that leaves, twigs or other organic substances that end up and start decaying in a water body release compounds known as surfactants that can lead to the creation of bubbles, but while such foam is “usually harmless", excess frothing is sign that there is too much phosphorus in the water, which in turn points to pollution from human activities.

But how to distinguish between natural foam and that caused due to pollution? Experts say that natural foam would normally be tan or light brown in colour, has an earthy smell and dissipates fairly quickly when not agitated whereas foam from human activity is usually white in colour, bears a soapy odour and persists for a longer period of time. Clearly the Yamuna froth checks all the boxes for the presence of pollutants as the trigger behind it.

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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first published:November 10, 2021, 11:28 IST