Rio 2016 Olympics - Embarrassing green water in the pools at Rio's Olympic aquatics centre, which left some athletes with itchy eyes, was because of an unplanned dump of hydrogen peroxide, Olympic organisers say.
A contractor added 80 litres of hydrogen peroxide to the diving and water polo pools more than a week ago, but organisers said they only found out on Tuesday when the water in the diving pool turned green during the women's 10m platform final.
The addition of hydrogen peroxide neutralised the chlorine and allowed algae to bloom, organisers said.
"This is a way of cleaning swimming pools but you're not supposed to combine it with chlorine," director of venue management Gustavo Nascimento said.
"We were not consulted, our contractor's failure is our failure."
The green pools became a huge headache for organisers of the Games, who have been the butt of "swamp" jokes among millions of spectators, both in the stands and from those watching on television.
Some water polo players complained about itchy eyes, while German diver Stephen Feck commented on Facebook yesterday that the whole venue smelt like "somebody has fart".
The electronic monitoring system for the pools at the Maria Lenk Aquatics Centre was functioning but was fooled by the chemical reaction to think that the chlorine was still working, Mr Nascimento said.
He said the fact 120 athletes were using the diving pool also increased the amount of "organics" in the water.
To treat the water, which organisers said did not pose any risk to athletes, they had been stabilising the chemistry and trying to make the algae more dense to clean it up.
However, they were were racing against time to avoid disrupting competition schedules.
Mr Nascimento said 10 hours would be spent draining and replacing the water in the pool to be used for the synchronised swimming event, which begins on Sunday, where competitors needed to see each other under water.
"Of course it's an embarrassment," Mr Andrada said.
"This was probably the only issue that we were unable to solve quickly."