A scientific report carried out last month said the waters were so contaminated with high levels of bacteria and viruses from human sewage that athletes could become ill and unable to compete at the Games, the first to be held in South America.
The International Olympic Committee (IOC) has ordered testing for disease-causing viruses after taking advice from the World Health Organisation, while the International Sailing Federation has said it will carry out its own tests for viruses in Guanabara Bay where the sailing events will be held.
Nuzman began his media conference in central London by saying that improving the quality of the water at the Olympic venues was a key priority.
Last week, two international sailors, from South Korea and Germany, training in Rio contracted infections which they said came from the waters.
Asked if he could guarantee that no athlete would become ill because of the well-publicised contamination, Nuzman replied: “The health of the athletes is the No.1 point we are working on.
“We are working very closely with the State government and the researchers and I am sure we will have no claims (that the water is dirty) during the Games.
“I have no doubt we will have no problems with the sailing at Guanabara Bay. Other Olympic cities have had problems with the waters and fixed them in time and Rio will do the same.
“This is a very serious matter and we are doing our absolute best to protect the athletes’ health.
“Marina da Gloria needs improvement but will be totally clean by the end of the year with the construction of a new pipe structure that will take sewage and rain water elsewhere.”
Other open air venues will stage triathlon, swimming, windsurfing, canoeing and rowing.
“The health and wellbeing of the athletes is our first priority. There will be no compromise,” he added.
Turning to doping, Nuzman favours an idea being discussed in sporting circles that the support team behind any athlete found guilty of doping — such as the trainer, physiotherapist, masseuse — should serve the same ban as the athlete.
“As an Olympic athlete myself, who took part in volleyball in the 1964 Tokyo Olympics, I have zero tolerance for doping.
“The whole team behind the athlete should be banned if there is a positive test. Not the country but his personal team.”
(Reporting by Mike Collett; Editing by Ken Ferris)