India, Dec. 22 -- Froth in the Yamuna is caused by a mix of human-made surfactants (from places like Dhobi ghats) and natural surfactants (saponins from water hyacinth plants). This foam is exaggerated when the Okhla barrage gates are suddenly opened, creating high turbulence as the water falls from a significant height, a study has found.

The study, conducted by The Energy and Resources Institute (TERI) and commissioned by the Delhi government to identify the reasons behind high froth formation in the river, also flagged poor working of the city's existing sewage treatment plants (STPs) and common effluent treatment plants (CETPs) in not only handling toxic sewage and effluents, but also failing to address a number of these surfactants ...