Bengaluru: Varthur lake, considered one of the biggest water bodies in the city, has been filled with a pile of froth after recent rains mixed with untreated sewage were let out into it, raising health concerns among people living nearby.

Such was the effect of this piled up froth that it spilled over to a road adjacent to the lake, causing hindrance to traffic movement on the busy road even as an unbearable stench hung in the air.

Stating that the accumulation of froth is common in this lake, locals said this was the first time they were seeing it in such huge quantity and blamed authorities for letting in untreated sewage water.

"Froth has come on the road, it is troubling the localities, please save the lake as well as the citizens staying in the nearby area," a local resident said.

Another local said, "Where are all the government officials? Where are all the local bodies which are supposed to regulate, restrict and sanitise the flow of untreated water from the residential area, apartments.”

Officials stated that formation of froth was due to detergent content in the untreated sewage water let into the lake and said Bangalore Water Supply and Sewage Board's proposed treatment plant near the lake would solve the issue.

Karnataka State Pollution Control Board Chairman Vaman Acharya said there are no industries in the area and whatever was flowing into the lake was sewage from households.

Varthur lake, the second largest in Bengaluru, is at the tail end of a chain of lakes and sewage from different localities flows into it in large quantities.

A few locals even blamed rampant encroachment along the boundaries of the lake as one of the important reason for the lake being polluted.

M A Khan Head of K K High School nearby said, "We have been monitoring the lake water quality for the past 14 years. Over a period of time we have seen that the quality of water is depleting in the sense the content of salt and phosphate nutrients has increased."

"If you see the PPM (Permissible Particulate Matter) per millilitre is 2500 here in this lake and simultaneously we have seen that the oxygen demand of the lake has gone to zero at many places. Also biological oxygen demand has also gone, simultaneously the the dissolved oxygen level has also gone down. The lake has also become a eutrophic lake."

Another woman resident in the area said the stench was just "unbearable." "Foul smell is emanating from the froth," she said.