A
layer of toxic foam has been floating on river Yamuna’s surface near Kalindi
Kunj in Delhi over the last few days. The high pollution level has forced the
Delhi government to ban fishing in the Yamuna.

The
increased toxicity of river Yamuna harms the ecology all around. And this has
become a common occurrence. Every year during Chhath Puja, devotees stand
waist-deep in the toxic froth. The scenes made global headlines two
years ago attracting immediate yet short-lived attention to the problem.

Here,
we delve into why the phenomenon keeps repeating.

Phosphates
present in water

Foam
forms on surface of water even in natural circumstances. This is because dead
and decaying parts of plants contain fat molecules that do not mix with water.
This results in an invisible floating layer in the surface of water. However,
this does not explain the amount of foam currently visible in Yamuna.

Phosphates
are used as ingredients in many commercially available detergents. These reduce
the surface tension of water and make cleaning easer. However, these phosphates
persist in water that leads to the phenomenon of eutrophication.

Eutrophication

Eutrophication
is a process by which a water body becomes rich in nutrients and minerals
leading to the growth of algae on the water. The growth of algae in turn
becomes an impediment to the flow of oxygen and sunlight in the deep depths of
water thereby hurting aquatic life.

These
phosphates cause the foam that forms on the surface of Yamuna.

Concentration
of phosphates

The
concentration of phosphates in Yamuna varies from 6.9mg/l at Okhla to 13.42mg/l
at Khajoori Paltan (downstream Najafgar drain), according to a report by the
Delhi Pollution Control Committee.

What
are the authorities doing?

Last
year, the Bureau of Indian Standards prescribed that the quantity of Sodium
Tripolyphosphates at 5% for detergent bars, 2.5% for powder and zero for
household detergents for woolen and silk fabrics.

The
National Green Tribunal (NGT) has also directed the state administration to
launch an awareness campaign to educate people about the harmful effects of
using substandard soap and detergents.