Water quality for the Olympic Games
In response to questions about health risks from sewage pollution at venues where Olympic athletes will be in water like swimming events among others, WHO recommends that national authorities follow the WHO Guidelines for Safe Recreational Water Environments to protect public health

http://www.who.int/water_sanitation_health/bathing/statement-rio-water-q...

Water Quality Report (INEA)

Rainwater Monitoring Systems

Rio Water Quality Monthly Report