Why did the #RioOlympics diving pool turn green overnight?

August 12, 2016

The Olympic diving pool turned green overnight


olympic pool turned green Credit: Mirror.co.uk 

It's the 2016 Olympic Games in Rio de Janeiro. The world's biggest stage for sports and national pride. And unless you are avoiding the news and TV coverage of the games, you probably saw that the Olympic diving pool turned green. Like, really green. More shocking is that it turned green overnight. How crazy is that?

Tag lines and click-bait images are all over social media, along with hashtags and other trending topics. Explanations are flying around from all sorts of people, from Rio officials declaring it's just algae; to other officials saying it's from unbalanced water chemistry; to the British gold medalist divers themselves, saying it could be caused by ink dripping off the banners that decorate the diving tower. Officials even said in a statement that the problem happened so quickly due to "heat and a lack of wind."

This incident is a good excuse for us to cover the relationship between pH, alkalinity, and sanitizer levels, and we hope you find the information valuable. Think of this as our professional opinion; an educated guess, if you will. Without pointing any blame for wrongdoing, we just hope to learn from this incident. And by the way, this is not just a problem unique to the diving tank in Rio, because a day later, the adjacent water polo pool started turning green too.

Why 'they' say the water turned green overnight

It seems to us that people are frantically searching for an answer, and we understand that. After all, this is a globally-visible gaffe, and the timing could not have been worse. Until we have accurate information on the chemistry and everything else going on in the pump room, the truth is unknown. Here are a few of the answers given to the media, along with our opinion.

  1. water turned green overnightAlgae. Some of the photos show what appears to be algae blooms (though algae experts dispute that). You may be wondering if algae can grow that fast, and surprisingly the answer is yes. Algae grows very fast in the right conditions. The bigger question is how the pool flipped so fast to create those right conditions. And is it just algae that's turning the water so green?
  2. Unbalanced water chemistry. This is only part of the story. Of course there is an imbalance of chemistry, but the real question is why? Most pools of this caliber use automated feeders. More on that below. Could the feeders have malfunctioned or broken?
  3. Ink from the banner/wall. As clever and fun as this answer is, we doubt it. You can look at the picture and the banner does appear to have faded below the water, but the tint of green is wrong, and that's a lot of water. Ink doesn't dilute like that anyway. We thoroughly appreciate the idea though.
  4. Heat and lack of wind. Hahaha, what? If that's the case, how come indoor pools can stay blue? They have way more heat and way less wind. We say no way.
  5. High bather load. Well, organic loading can definitely contribute to a problem...but Maria Lenk has hosted meets with far more people. To get the kind of loading it would take to flip a pool that size would likely way more people. So this is doubtful.
  6. Low alkalinity. This one makes a lot of sense. Alkalinity buffers pH. That is, it helps keep the water's pH stable. If the alkalinity is low, the pH can become unstable, and easily move up and down, depending on what other chemicals are in play.
  7. Lack of chlorine. Highly likely. After all, chlorine (or whatever sanitizer they're using in Rio) kills algae. If they ran low, or their feeder broke, or anything like that, this could definitely contribute to the problem.

We at Orenda think there might be other factors in play as well...

Don't forget about metals

copper metal stain

Yes, metals. Specifically copper. One of the trends we are seeing in the pool industry is use of copper-based algaecides, particularly in residential pools. It's an inexpensive way to "prevent" algae blooms from happening. That being said, copper can (and does) turn water green when it is oxidized

But even if they're not using a copper-based algaecide in Rio, copper could still be the main culprit. You see, diving pools, during competition, raise their temperature so the divers don't get cold and shiver. If you ever watch a diving meet, notice they take a hot shower after each dive, jump in the hot tub, and then dry themselves with their shammy towels. Shivering is a sure-fire way to lose flexibility when you need it most...so the water is kept warm. We know this because we asked divers and their coaches.

Heating a pool requires metal components. Usually, hot water is transferred through copper pipes. Look at your hot water heater at home...you won't see PVC pipes carrying the hot water...you will most likely see copper.

Our theory

As stated clearly before, we do not have all the facts. Our theory is only based on the information available. We want to learn why the Olympic diving pool turned green overnight just as much as anyone.

To keep the water looking great for the Olympics, we think operators may have raised the chlorine and lowered the pH. These two actions could have led to every subsequent problem. Here's how...

Raised chlorine and lowered pH makes water look really clear...for a while. Lowering the pH dramatically increases the efficiency of chlorine. But since most chlorine (like calcium hypochlorite or sodium hypochlorite) raise the pH, it takes acid to lower it. Adding acid does not just lower the pH, it also lowers the alkalinity. If alkalinity drops, so does the stability of the pH, so it can fluctuate rapidly. This is backed up by numerous reports indicating that the alkalinity has dropped at the pool.

We have reason to believe the pH has been low in the pool, due to complaints from Olympic water polo players of eye irritation. Water polo players train every day without goggles. When their eyes burn, something is off. They are a very accurate "canary in the mine" for bad chemistry. In this case, we believe it's not high chlorine that is causing that burn, but more likely the acidity of the water. Why? Because we think they are low (or possibly lack) chlorine.

Lack of sanitizer can be caused by a number of things. Do they have an automated feeder? Is it working properly? We just don't know. Also, chemical feeders monitor pH and chlorine...not alkalinity. Typically you set it to keep the pH stable, so it will add in acid (-pH) or sodium bicarbonate (+pH) to keep the pH between 7.2 and 7.4. But feeders can also be set to keep chlorine at a certain level, which could have happened in Rio. That, or they could have run out of chlorine, or had other issues.  Either way, it appears that not enough chlorine was getting into the pools, and hopefully it has been resolved since.

As for the green water, we think copper is the most likely culprit, though there appears to be some algae in the photos as well. It's hard to say if there is actually algae, but it's possible. Copper is likely, given that many algaecides are copper-based. Copper is driven out of solution in a low pH, low alkalinity environment, which may have caused the water to have turned green overnight.

Now what?

Without all the facts, we cannot give an accurate diagnosis...and certainly not a prescription. If it is copper staining, however, get alkalinity and pH back under control, get chlorine to the right levels, and use a metal sequestering agent.  It may take a few backwashes to clean out the system, but it should be able to turn back to clear blue water.

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