Cape Town - The City of Cape Town is treating its dwindling water supplies for a harmless organic compound that is affecting its smell and taste, it said on Tuesday.Confirming the suspicions of many who had observed changes in the water as dam levels dropped to 27.3%, councillor Xanthea Limberg said the compound geosmin was responsible.To counter it, the city had increased dosing the water with powdered activated carbon during the treatment process. It assured residents that geosmin was completely harmless and that the city's water supplies were constantly monitored by sample analysis.“It must be emphasised that geosmin poses no threat to human health. Even minute concentrations can be detected by the incredibly sensitive human palate,” Limberg, who oversees water, sanitation, and informal settlements, said in a statement.According to an article in “Scientific American”, geosmin is one of the “storm scents” the nose detects as a musty, earthy smell when the rain falls on dry earth. It is a metabolic by-product of bacteria or blue-green algae. It contributes to the “rain smell” known as petrichor.Also associated with the smell of beetroot, geosmin has been detected in water drawn from the Theewaterskloof Dam, which supplies the city.However, water pressure might be reduced to limit water leaks. She urged residents to continue reducing water use.