Rio Officials: Hydrogen Peroxide Caused Green Pools

In the latest episode of the soap opera “As the World Turns ... Green,” we now have a more definitive explanation from Rio Olympics officials as to why pools used for diving and water polo turned from blue to green: hydrogen peroxide.

Officials said 160 liters (or more than 42 gallons) of hydrogen peroxide was mistakenly added to the pools on Aug. 5, The New York Times reported. The hydrogen peroxide neutralized the chlorine and allowed the growth of “organic compounds” that might have included algae, according to the report.

Gustavo Nascimento, director of venue management for the Rio Olympics, told reporters Saturday that hydrogen peroxide works as a pool-cleaning agent except when it combines with chlorine. After divers and water polo athletes began using the pools at the start of the Games, the neutralized chlorine spurred the proliferation of organic compounds, The Times reported.

“The electronic monitoring system that measures the amount of chlorine in the water was betrayed by this chemistry,” Nascimento said.

This information came after Rio Games spokesman Mario Andrada, in an attempt to try to explain the mishap last week, said, “We first learned that chemistry is not an exact science.”

Related: Officials Offer Explanation for Rio's Green Pool Water

Chemistry is an exact science, as some noted, including one Forbes contributor who writes that hydrogen peroxide does not turn water green and that the likely cause was too much copper sulfate, which may be why some thought the aquatic center smelled like, um, passed gas:

So basically, the pool manager added excessive quantities of copper sulfate to the pool water (perhaps this was a “decimal place error”?). Then, when he tried to deal with that problem (actually, I think he panicked), he ended up adding too many other chemicals, which made things worse by screwing up pH and other water parameters, causing the athletes to suffer a variety of physical problems, including burning eyes and itchy skin.

Workers completed the Olympic-sized task of draining all 3.725 million liters (more than 984,000 gallons) of the green water at the Maria Lenk Aquatics Center and replacing it with clean water from a nearby practice pool. The process took 11 hours but was completed in time for Sunday’s synchronized swimming, a sport in which seeing a partner’s movements under water is crucial.

The new water gave us a chance to see performances such as this that became viral on Sunday:

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