The River Ganga

All along the Ganga [Ganges], the major problem of waste disposal has defied the best efforts of the Ganga Action Plan set up in 1986 to solve it.  The diversion and treatment of raw sewage in the seven main cities was planned.  In Varanasi however, the 17th century sewers, the inadequate capacity of the sewage works, the increased waterflow during the monsoons and the erratic electricity supply (essential for pumping) have all remained problems.  In addition, although most Hindus are cremated, an estimated 45,000 uncremated or partially [sic] cremated bodies are put in the Ganga each year.  A breed of scavenger turtles which dispose of rotting flesh was introduced down river but the turtles disappeared.

Surprisingly, although the Ganga may be one of the world's most polluted rivers...scientists had discovered the river's exceptional property in the last century.  The cholera microbe did not survive 3 hrs in Ganga water whereas in distilled water it survived 24 hrs!

That is from the India Handbook, eighth edition, p.249, and here is a photo and some background information.  It should be noted, however, that cholera along the river has not ceased to be a problem.