Foam in Lake Bellandur forms after rain due to raw sewage and precipitation patterns. This has been reported by the Indian Institute of Science (IIS).
Bellandur Lake in the Indian state of Bangalore is regularly covered with foam after heavy rains. This goes against both the observation of other lakes and common sense, because unlike rains, it should dilute the pollutants that make up the foam.
Dr. Chanakya and his colleagues studied the chemical composition of the water in this lake for a long time and were able to find out the nature of the anomaly. According to experts, this is primarily due to the untreated wastewater stream containing washing powders. With the gradual uptake of surfactant, they have time to decompose and bind to the underlying silt. Second, foam formation is associated with region-specific heavy downpours. During heavy rain, a large amount of water enters the lake in a short time, shaking the reservoir and washing the detergents accumulated in the silt. Spilling the lake onto the surrounding surface saturates the water with air, which is the direct cause of the foam whipping.
Finally, foam formation is facilitated by solid particles suspended in water, possibly containing special bacteria. These may give the foam the observed stability, but more laboratory testing is needed to confirm this claim.