Is Ganga Water Clean Enough?

Maha Kumbh, the largest religious congregation on earth, is being held in Allahabad from Monday till the 10th of March. Over 2 crore people are expected to take a dip in the Holy Ganga. But how clean is the Ganga really?
Allahabad's importance as the host city for the Maha Kumbh is largely due to the confluence of holy rivers at the Prayag Sangam.
But what was holy and pure in ancient ages, is now a pool of filth, largely due to various industrial pollutants and effluents being poured into the river Ganga.