Chemistry: It’s Why The Rio2016 Pool Water Is Green | @GrrlScientist
No, no, NO! Hydrogen peroxide does not turn water green (nor does it make water smell like farts)
Whenever I read about the 2016 Summer Olympics, water quality has almost always been mentioned as being the biggest concern. And no wonder, considering that an investigative report published by the AP in July 2015 found that the waterways around the host city, Rio de Janeiro, are filled with raw human sewage along with dangerously high concentrations of two types of disease-causing human adenoviruses, rotavirus, enterovirus, swarms of pathogenic bacteria and a plethora of other items, ranging from floating trash to discarded appliances and vehicles. Even the sand on Rio’s beaches is infected with high levels of disease-causing viruses. So it’s no surprise that a growing number of people refer to the Rio Olympics as the “poop olympics”.
But surely, the water in the swimming pools is safe, right? Although large, these pools are much smaller than the local waterways, so the water quality can be carefully controlled. Further, the pool water is not polluted (probably), and it benefits from constant filtration and appropriate doses of sanitizing chemicals. Of course, this scenario assumes that the person who is ultimately responsible for managing these pools actually knows what he is doing. But ongoing water quality issues and the variety of imaginative non-explanations for the poor water quality in the Olympics pools indicates that, although the athletes are the best in the world, the pool manager clearly is not. In fact, it is obvious that the Rio Olympics pool manager is as green as the water in his pools.
Worse, the neon-green water in the diving pool morphed into an ominously murky olive-green on Friday, when the pool was unexpectedly closed, because by that time, the building “smelled like a fart“. What is the problem?
According to a statement by FINA, the international governing body of aquatics:
“FINA can confirm that the reason for the unusual water colour observed during the Rio 2016 diving competitions is that the water tanks ran out of some of the chemicals used in the water treatment process. As a result the pH level of the water was outside the usual range, causing the discolouration. The FINA Sport Medicine Committee conducted tests on the water quality and concluded that there was no risk to the health and safety of the athletes, and no reason for the competition to be affected.”
Although I’m not an expert, I worked as a “pool boy” whilst a graduate student, and studied water chemistry in university, so I became fairly well-acquainted with both the practical and theoretical ways that pool water chemistry can be screwed up. And it is my opinion that the pool water at the Rio Olympics has been screwed up as the direct result of preventable human error. (Read: inexcusably stupid human error due to a startling lack of practical and theoretical knowledge of water chemistry.) I say this because, contrary to Rio 2016 spokesman Mario Andrada’s ignorant assertion, chemistry actually IS an exact science.
The Olympics pools’ ever-changing palette of green is not due to too many people in the water nor to not enough wind in the air, nor is it due to algae growth (puhleez, algae doesn’t grow this quickly), nor is it caused by excessive hydrogen peroxide being added to the water, nor even, as FINA claims, is it due to the pH level of the water being “outside the usual range”.
No. Nope. None of these.
True, these other issues are contributing factors, but they are not the direct cause. So let’s review the clues: first, the water is green. Second, there have been complaints that “the whole building smells like a fart”.
Based on this information, I think that the green pool water is the result of excessive copper sulfate in the water. Copper sulfate — copper(II) sulfate or copper sulfate pentahydrate — is a blue crystal that is used in tiny quantities to control the growth of green algae in large public pools and in municipal water supplies. Homeowners with smaller pools may also use it periodically for the same reason. Although copper sulfate is poisonous, it does not cause health problems for people — if used in small doses.
When copper(II) sulfate is added to water, it dissolves quickly. The copper ions combine with four chlorine ions in the water, creating a copper(II) tetrachloro complex, which is green, and if it’s present in high enough concentrations, it turns the water green. The sulfate ions are reduced to hydrogen sulfide, a stinky gas, which is the source of the rotten egg smell associated with raw sewage and farts.
Although I’ve not seen the pool officials admit that they are using copper sulfate in their pool water, other clues that make it appear obvious that they are. For example, aqueous copper ions stain pale hair green, as you see happening to Ryan Lochte’s silver-bleached locks:
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 (translation: he probably 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.
Now that the diving pool has been completely drained and the water replaced, I am curious to know where this toxic green broth went? Was it drained directly into the fetid Guanabara Bay, thereby adding to its plethora of problems?
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Originally published at Forbes on 15 August 2016.