An aerial view shows the Marina da Gloria, which will host the sailing at the 2016 Rio Olympics, in Rio de Janeiro, Brazil, April 25, 2016. [Photo/Agencies]

The Rio government has admitted it won't be able to meet a 2009 pledge to reduce pollution in the bay by 80% ahead of the Games.

But officials say a vast network of nets, known as eco-barriers, have been strategically placed to prevent rubbish and waste entering the bay.

A fleet of eco-boats will also be used to scoop up trash from the water's surface.

Concerns have also been raised about water quality at the Rodrigo de Freitas lake, which will host rowing and canoeing events. The government said a cleanup operation of the lake had ensured it will meet international standards for the events.

Legacy 

As part of Rio's Olympic legacy pledge, many venues built for the Games will be turned into public schools, sports facilities and leisure centers.

Organizers say the Games will improve the quality of life for Rio's citizens through infrastructure works like new public transport links and better waste management.

In addition, thousands of people will benefit from job training, creating pathways for new careers.

According to IOC president Thomas Bach, the greatest legacy could be the healing of wounds inflicted by political and economic troubles.

"Despite the difficulties that Brazil faces, the flame is an eternal reminder that we are all part of the same humanity," Bach said during the torch-lighting ceremony in Greece last week. "That will be the great legacy for the Rio Games for Brazil and the world."