By the end of Ganesh festival over 3 lakh idols maybe immersed in 32 lakes in the city. People will be permitted to immerse idols in designated lakes till September 18. One of the highlights of the Ganesh festival this year has been a 30 per cent rise in the sale of eco-friendly idols. Over 27,000 such idols have been reported sold by agencies after the Karnataka State Pollution Control Board conducted awareness programmes against the use of conventional idols. Chemical idols are non-biodegradable,once immersed they not only disperse but also act as a blanket on bio-life,stopping sunlight and nutrition, said Mala Dhawan of A Hundred Hands NGO.