Explained: Why the Yamuna froths up in Delhi NCR and why it is dangerous

The primary reason behind the formation of the toxic foam was high phosphate content in the wastewater because of detergents used in dyeing industries, dhobi ghats and households, according to experts.

A snow-like froth on Yamuna river in Delhi-NCR, where snowing is topographically next to impossible, on one hand made for some dramatic visuals, and on the other triggered a political slugfest between the ruling AAP and the BJP.

This is not a new sight.

Yamuna’s toxic foam is a problem that has plagued Delhi before. But as devotees prayed to the sun god, standing knee-deep in the water surrounded by toxic froth this week, the health scare from Delhi’s chronic pollution problem became a cause of concern.

We explain the science behind this froth:

Sick rivers frothing at the mouth

Yamuna is easily one of the most polluted rivers in the country. The 22-kilometre stretch of the Yamuna between Wazirabad and Okhla, which is less than two percent of its length of 1,370 kilometres from Yamunotri to Allahabad, accounts for around 80 percent of the pollution load in the river.

The primary reason behind the formation of the toxic foam was high phosphate content in the wastewater because of detergents used in dyeing industries, dhobi ghats and households, according to experts.

The CPCB report submitted in August last year notes that foam formation takes place at two locations – downstream of the ITO and Okhla barrages. The water falling after discharge from the Okhla barrage causes the surfactants and foaming agents present in the wastewater or in the sludge on the river bed to get agitated, forming foam.

What are the sources of pollution that cause foam formation?

These effluents find their way into the water through untreated wastewater from unauthorised colonies and partially treated effluent discharged from Common Effluent Treatment Plants (CETPs) and sewage treatment plants (STPs) within Delhi. On an average, 24 out of the 35 STPs in the National Capital did not meet the prescribed standards for wastewater over the last year, according to government data.

Of the 13 CETPs in industrial areas across Delhi, only six comply with the DPCC standards for wastewater on an average.

Delhi generates around 720 million gallons of wastewater a day. The 35 STPs located at 20 locations across Delhi can treat up to 597 MGD of sewage and have been utilising around 90 per cent of their capacity.

AAP leader and Delhi Jal Board vice chairman Raghav Chadha claimed that Haryana and Uttar Pradesh have been 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 fall from a height at the Okhla barrage which leads to the formation of foam,” he said.

Besides, paper and sugar industries in Meerut, Muzaffarnagar, Shamli and Saharanpur in Uttar Pradesh also release untreated wastewater containing surfactants into the Yamuna through the Hindon Canal at Okhla Barrage near Indira Kunj, Chadha said.

While the Delhi government has been working to upgrade its sewage treatment plants to meet the revised standards of the Delhi Pollution Control Committee (DPCC), Uttar Pradesh and Haryana should do their bit in keeping the river clean, he said.

Why froth now?

Sushmita Sengupta, senior programme manager of the Water Programme at the Centre for Science and Environment (CSE) answered that question in conversation with The Indian Express. She said that the reason the froth shows up around this time of the year, even though water pollution is a year-long problem, is that river is in a lean phase and the water flow is less. Pollutants, therefore, do not get a change to get diluted over time.

Is there a solution?

In a report submitted to the Union Jal Shakti Ministry in July, the Delhi government had said that the Yamuna cannot become fit for bathing in the absence of a minimum environment flow in the river. Environmental flow is the minimum required water that needs to remain present in a river, wetland, or coastal zone to maintain ecosystems and their benefits where there are competing water uses and where flows are regulated.

For the Yamuna river, this minimum environmental flow is around 23 cubic metres per second (cumec), as per conservative estimates made in a study conducted by the National Institute of Hydrology, Roorkee.

However, the existing water sharing mechanisms (1994 interstate Memorandum of Understanding) do not provide for this extra release of the water, drying out the river to dangerous levels in leaner months of December to March.

A barrage cum dam at Hathnikund (HKB), some 230 km upstream of Delhi, is considered the root cause behind this restricted flow. The inter-state water-sharing agreement signed in 1994 restricts the river flow downstream of the barrage to mere 160 cusecs (cubic feet per second), which by no stretch of imagination can be called its minimum environmental flow.

An analysis of the average flow data in the river at Hathnikund prior to the commissioning of HKB showed an average daily flow of 3,500 cusecs during the lean season months of December, January and February. This thus in all fairness is the ‘minimum’ environmental flow to which all ecological processes related to the river Yamuna are naturally adapted and to deprive the river of even this level of flow cannot be justified under any circumstances.

Increasing the flow back to normal, along with controlling the amount of effluents that enter the river, in the lean season is the only way of sustaining downstream ecosystems.

But as the ministry/National Mission for Clean Ganga has observed, the water-sharing agreement of 1994 among the riparian states of Uttarakhand, Himachal Pradesh, Uttar Pradesh, Haryana, Rajasthan and Delhi is not due for revision before 2025. So the situation is unlikely to improve before then.

What are the health hazards?

Short-term exposure can lead to skin irritation and allergies. If ingested, these chemicals may cause gastrointestinal problems and diseases like typhoid. Long term exposure to heavy metals in industrial pollutants can cause neurological issues and hormonal imbalances, according to Hindustan Times. 

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.

With inputs from agencies

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