Why in news? Indian Institute of Science’s Centre for Sustainable Technologies, unearth the reason for infamous Bellandur lake’s foam

Highlights:

What are the reasons for the foam?

• Organic material gets degraded in the absence of oxygen and settles down as sludge, due to influx of untreated sewage owing to large size of lake
• As the water level in the lake rises due to rains, the excess water containing large concentrations of the surfactants spills over into the lake’s outlet to depths as high as 25 feet, trapping air bubbles which turn into foam
• Household washing powders and shampoos plays a dominant role in driving this foaming

How to address the issue?

• Stopping the entry of untreated sewage
• Removing the accumulated sludge in the polluted lakes

About Bellandur lake

• Largest lake in Bengaluru
• Drains the southern and the south-eastern parts of the city
• Catchment area – 148 square kilometres (37,000 acres)
• Water from this lake flows further east to the Varthur Lake, from where it flows down the plateau and eventually into the Pinakani river basin