Lake Bellandur in Karnataka, near Bangalore, frequently develops a frothy layer after heavy rainfall. This phenomenon has drawn attention from researchers who study how polluted water and weather patterns interact in urban lakes. Reports from the Indian Institute of Science, IIS, have highlighted that the foam is not simply a result of rain diluting pollutants but rather a product of multiple interacting processes in the lake system.
Researchers have long examined the chemical makeup of Bellandur’s waters, uncovering a combination of untreated wastewater discharges and detergent residues that contribute to foam formation. Detergents and washing powders enter the lake through sewage streams whose flow is intensified during storms. Surfactants, the active cleaning agents in these products, persist in the sediment and gradually mobilize when rainwater destabilizes the silt, allowing these molecules to disperse into the water column. This release promotes foam as air bubbles become trapped on the surface and repeatedly gather more surface-active compounds.
The timing and magnitude of foam also appear linked to region-specific heavy downpours. When intense rainfall dumps large volumes of water into the lake in a short period, the lake experiences agitation that helps suspend detergents within the water. The rapid movement and mixing increase the chance that air introduced at the surface will form persistent foams instead of dissipating quickly. The local hydrology of Bellandur, combined with the input of pollutants, creates a situation where foam forms and persists more than would be expected in a clean or naturally balanced water body.
In addition, solid particles suspended in the water may play a role in stabilizing the foam. Some of these particles could carry bacteria or other microorganisms that interact with surfactants, potentially contributing to the foam’s observed stability. While this is a plausible mechanism, confirming the exact microbial contributions requires further laboratory testing and controlled experiments.
Overall, the foam at Lake Bellandur emerges from a convergence of untreated wastewater streams, detergent-derived surfactants, sediment-based reservoirs of pollutants, and rain-driven mixing. Ongoing studies, including work cited by IIS, emphasize the need for comprehensive water treatment, better drainage management, and targeted pollution control to reduce pollutant loads entering the lake and to limit the conditions under which foam forms and persists.