DNA Explainer: What is the reason behind toxic white foam floating on Yamuna in Delhi?

Chhath Puja celebrations in Delhi have brought to light the extreme levels of pollution in the Yamuna river flowing in the national capital. During Chhath Puja snan (holy dip) in Yumana, pictures of white froth immerged leading to a war of words between the ruling party and the opposition.

Meanwhile, what remains ignored in this senseless political rhetoric is the 'pathetic' state of the river which is the lifeline of Delhi as its water is being harnessed from both of its banks for domestic, industrial and irrigation purposes. To meet the ever-growing water demand of the city, the river is tapped at three points - Wazirabad, ITO and Okhla barrages.

As per reports, the 22-kilometre stretch of the Yamuna between Wazirabad and Okhla accounts for around 80% of the pollution load in the river. The stretch is said to be less than 2% of its length of 1,370 kilometres spanning from Yamunotri to Allahabad in Uttar Pradesh.

However, the formation of toxic foam in the Yamuna is nothing new. Every year, during the Chhath Puja, images of devotees standing in a waist-deep toxic froth in the Yamuna river make headlines. But nothing much has been done so far to understand the cause and rectify it.

How froth is formed?

Under natural circumstances, the formation of foam on the surface of the water is very common. This phenomenon takes place on many lakes and streams. 

Foam bubbles are produced when organic matter decomposes. Dead and decaying parts of plants contain fat molecules that do not mix with water.

These are lighter than water so they float on the surface and then gradually accumulate and form an invisible floating layer on the water surface. 

The foam-producing molecules have one end that repels water and another that attracts water. This works to reduce the surface tension on the water. 

The foam made from organic matter in rivers and lakes can last for a long time. But the amount visible in Yamuna cannot be explained by such natural phenomenon.

What causes the froth?

The high level of phosphates in the Yamuna river is what causes such foam to build up say, scientists.

Phosphates and surfactants in untreated sewages from Delhi, Haryana and UP is another reason behind frothing in the river.

Phosphates are an ingredient used in many detergents. These compounds make cleaning a lot easier.

While phosphates and surfactants in the Yamuna river comprise 1%, the remaining 99% is air and water.

When the water gets disturbed by waves, natural waterfalls or artificial falls from river barrages, the fatty layer gets beaten into a froth.

Delhi Jal Board Vice Chairman Raghav Chadha claims waste material falls from a height at the Okhla barrage leading to the formation of foam. 

Industrial effluents, organic matter from decomposing vegetation and the presence of filamentous bacteria cause foam.

Health hazards 

Short-term exposure to such froth in the Yamuna river 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.