Killing the Ganges with Justin Rowlatt

India's greatest river, the Ganges, is one of the world's dirtiest. The river is revered by Hindus, but it is also the sewer that carries away the waste from 450 million people.Pollution from industry, agriculture - and even waste from religious ceremonies - has turned its sacred waters into a toxic and deadly cocktail. The Indian prime minister has staked his political reputation on cleaning it up, but can the Ganges be saved?