Even there was some study conducted on Water Pollution from mass Bathing in Ganga River During Kumbha Mela. If anyone can get hold of full report please post the link.
Water Pollution from mass Bathing in Ganga River During Kumbha Mela
Foreword
Mass bathing is frequently held in India. On certain religious occasions,
special importance is assigned to it and a very large number of people take
bath during a short period in specific stretches of rivers, lakes, tanks and sea
coast. 'Kumbh' and 'Ardh-Kumbh' are such occasions when millions take dip
at sacred spots.
Water quality is severely affected by mass bathing. Deterioration of river water
quality may injure health of the people taking the dip and also the population
downstream which use the river as a source of water for drinking and bathing.
To ascertain the deterioration of water quality, changes due to mass bathing
have to be observed through monitoring before, during and after the mass
bathing event and taking appropriate actions at all stages. The Central Board
for the Prevention and Control of Water pollution in the above context had
sent its team of scientists and
engineers to several religious congregations to monitor water quality changes.
http://www.cpcb.nic.in/upload/Publications/Publication_279_sec4_15.pdf