Why Did The Olympic Pools In Rio Turn Green?

As most of the world is now aware, the 2016 Olympics in Brazil have had some trouble with the water quality in their swimming pools. Bright green water in the diving pool first appeared on August 9, 2016 and the following day the problem spread to the adjacent water polo pool. The media has been actively reporting on this embarrassing situation for the Olympic organizers and many people have been speculating as to why this happened - myself included. On August 10th I was contacted by a Toronto Star reporter who asked the same question that I have been hearing non stop since this debacle began: "Why did the Olympic pools in Rio turn green?" I provided some basic information which was printed the following day which you can read here: Toronto Star article on green pool water at the Olympics.



This article however only touches very briefly on the surface of the potential problem so I decided to write this to help people understand the nature of green pool water. Most importantly, the reason that everyone is speculating as to what caused the problem is because there have been no actual water testing variables released to the public. This alone is actually very telling. Every pool technician in the world would have the same approach to solving the problem of a green pool, whether Olympic in nature, or just a regular backyard oasis. What are the chemical levels in the pool? What is the free chlorine level? What is the pH? What is the total alkalinity? What is the total chlorine level? How much copper is in the water? What is the level of phosphates in the water? If they were to release this information, which could be acquired by any teenager with a few bottles of test strips, then most swimming pool owners would easily be able to spot the problem on their own. The fact that they have not released this information to me is a clear indication that there is zero mystery as to why this happened. Whatever the cause, they know exactly what happened, and they are not releasing this information to save face. This article is intended to provide some additional information for interested readers who want to know more about why the Olympic pools turned green.







Are The Olympic Pools Safe To Swim In?

Over and above the spectacle of an emerald green pool at the Olympics the real question that everyone wants to know is "Are the Olympic Pools Safe To Swim In? The answer to this is something that we simply will not know until the test results from the water are released...if they ever are. In a properly balanced swimming pool everything other than cryptosporidium will be dead in the water in less than 60 seconds. Crypto requires 10 PPM free chlorine maintained for 24 hours in order for the chlorine to kill this stubborn and resilient parasite. If I were going to swim in that green water this would be my primary concern. The green color is not likely a problem itself, but an indication that there has been a breakdown of the maintenance process which opens the door for potentially harmful things to also be in the water. In order to understand this further you should be aware of the potential reasons that pool water can turn green. While we can not say for sure why this has happened until water testing values are made public, it can be assumed that the water is green for one (or more) of the following reasons:







What Might Have Caused The Green Water?

Lack of chlorine in the water - This is swimming pool maintenance 101. Almost every pool owner has accidentally let their chlorine drop to zero and witnessed green water first hand. Without free chlorine in the water then there is nothing to prevent the growth of bacteria and algae. The algae has a physical symptom of visibly green water which is usually the point that the problem is discovered. At minimum a residential pool should have 1 PPM of free chlorine in the water at all times. Commercial pools (including Olympic venues) would normally have levels much higher than this. It is possible that the pools in Rio simply did not have enough chlorine in them but it could also be that the cyanuric acid level in the pool was too low and as a result the UV from the sun burned off the chlorine that was there.



Chlorine in the water but not able to work - Sometimes you can have a free chlorine level in pool water however algae and bacteria can still multiply. There are a few reasons that this could happen. In the event that the cyanuric acid level is too high you would experience "chlorine lock" where the chlorine is not able to do its job of killing bacteria and organic debris. Cyanuric acid level too high would be less likely than other reasons that the pools turned green but is still technically possible. While stabilizer induced chlorine lock is a possible explanation for the chlorine being able to work effectively in the water there is a much more likely explanation for this specific situation that relates to the pH of the water.



pH values too far out of range - It has been reported by multiple sources that the Olympic pool water had an elevated pH due to an error with the automation system. If this is the case the system designed to dose the pool with acid when the pH of the water increased ceased to function. Multiple sources have stated that the acid tanks used to regulate the water pH ran dry and this was either not noticed in time, or possibly that they had no more acid available on site to use (as reported by FINA, the International Swimming Federation: Statement from FINA). If the pH of the water were to increase above the level of 8.2 (some reports say that the pools reached a pH of 9.0, unconfirmed) then the chlorine in the water would simply not be able to do its job. Chlorine is most active at much more acidic pH levels than you would want to swim in, close to 5.0, yet still sufficiently active in the 7.2 - 7.8 ideal pH range for pools. Above 8.2 the chlorine is almost completely inactive in the water so even if there was sufficient chlorine for normal circumstances it would not be able to stop algae (and bacteria) from potentially growing in the water. This, in my professional opinion, is what I think happened to the Olympic pools.



Phosphate (or nitrate) levels too high - Phosphates are a very common problem with swimming pools these days. Phosphates are present in rural source water, wells, fertilizer, rain water, detergents and soaps. In a swimming pool phosphates act as a food source for algae which counteracts the desired sanitizing effects of chlorine. At extremely low levels of phosphate, anything over 500 parts per billion, chlorine will have a difficult time keeping up with the rate of algae growth in the water. Over 2000 PPB, phosphates will promote algae growth that can outpace a how much chlorine a salt water chlorine generator can manufacture even running on maximum. Phosphates are responsible for many pools turning green and if this was the cause for the Olympic pools this would be something that could be verified in 5 minutes with a simple phosphate testing kit. Nitrates in the pool could have a similar impact on the water quality as phosphates in that they both deplete chlorine reserves rapidly by encouraging algae growth. Again, removal of the phosphates would be the remedy since removing phosphates would also limit the problems from any nitrates in the water.



Copper turned the water green - This is one of the more popular theories that has been floating around the past few days. While it is certainly possible that this was the problem, and water tests would easily confirm this, I feel like this is less likely than a chlorine related failure. Copper can be introduced to a swimming pool as part of source water, a mineral injection system, copper based algaecides, or as copper somewhere in the pool system (the heater or plumbing lines) degrading. Copper has antimicrobial properties and can assist in keeping pool water safe, but higher levels of copper combined with heavy doses of oxidizer can result in green water. Copper in pool water should not be in concentrations higher than 0.3 PPM or staining of the pool may result. This is the main reason that I do not believe copper to be the source of the green water at the Olympics. If the copper level was high enough, and especially if the copper in the water was reacting with oxidizers, I would expect that there would also be reports of swimmers hair turning green. Since there have been no reports of this, at least that I have found, then this makes a copper related cause for the green pools less likely. It is worth noting that iron can cause green tinting to pool water also and this would be easily confirmed by a simple water test.



Poor water filtration - Clear water is at least 50% dependent on effective filtration so the chance that the filtration system is undersized or not operating correctly is possible. The diving pool in particular, the first to turn green, was an existing pool and not one built expressly for these Olympic games. That means that the existing system might not be large enough to filter the water effectively with such a dramatic increase in bather load.







Polo Players Complain About Stinging Eyes

Two days into the green pool disaster at the Olympics and reports are now saying that polo players are complaining of stinging eyes and strong chlorine smell in the water. This further validates that the problem is sanitizer based, not mineral based, as Olympic pool operators have clearly responded to the problem by heavily dosing with chlorine. Also worth noting is that PH out of ideal ranges could also cause eye irritation or contribute to it. If they thought copper was the problem (and they know since SOMEONE knows the water test values) then they would not be super chlorinating the water to fix the problem. This is a clear indication to me that either a lack of chlorine, or a reduced effectiveness of chlorine, has caused them to react by heavily shocking the water. The polo pool had started to turn green the evening before so they likely raised the chlorine level in an attempt to prevent the second pool from becoming completely green.







Opinion From A Pool Expert For The Cause Of Green Water At The Olympics

The only thing I can say with certainty is that there is zero "mystery" as to why the pool water at the Olympics is turning green. If they genuinely felt baffled by the appearance of green water then I would assume they would invite other experts to analyze their findings - which has not been the case. By not releasing water testing results this points directly towards a problem that they are aware of, and hoping to make go away. Not exactly a cover up situation but not exactly forthcoming either. Even if they do release the testing results it will likely be held off until the green pool problems are resolved. Right now this problem is receiving entirely too much international attention and they are playing their cards close to prevent from incriminating, or further embarrassing, themselves.



I think that the people who are operating the Olympic pools failed to take into account the bather load increase that the pool would experience during the games. They most likely let the chlorine drop to zero, or let the acidity control system run out of acid which allowed the pH to climb unrestricted which resulted in the chlorine being unable to kill bacteria and algae. The fact that the pool is located outdoors and it had rained the morning that the pool first turned green, further reinforces my belief that chlorine, or a lack of it, is primarily responsible for this problem. While the pool water may very well be safe, as a water chemistry expert you would not find me, or my family, swimming in that water.







UPDATE To Green Olympic Pools

A few days after the initial reports of green pool water at the Olympics in Rio surfaced, and a few days after the above article was released, there have been a few noteworthy updates. The Olympic Committee has now released information that over 80L of hydrogen peroxide was added to each the diving pool and the water polo pool. This is significant for a number of reasons.



Hydrogen peroxide will lower chlorine levels - Chlorine has both an oxidizer as well as a sanitizer property. The oxidizer is effective at oxidizing bacteria and organic debris in the water, but unable to hold a residual value. Oxidizer like hydrogen peroxide would be suitable for a one time oxidizing shock but it would not last in the water. In the presence of chlorine however the chlorine would act as a stronger oxidizer and actively oxidize the hydrogen peroxide. This would result in no hydrogen peroxide in the pool, as well as no chlorine. The fact that it rained after this treatment would be a further likely condition that would promote algae growth since it is possible that the chlorine had been depleted by the peroxide.



Olympic swimmers hair turning green - Olympic swimmer Ryan Lochte who was robbed at gunpoint just a few days after gold in the 4 x 200m relay, also has the distinction of green hair during these Olympic games. While it used to be bleached to a silver color, it has changed to green over the course of the first 10 days of the Olympics. This is possibly the single strongest indicator that has been discovered about the poor water quality management of the pools in Rio. Green hair in a pool is a result of copper in the water. Specifically copper that has been exposed to high levels of oxidizer (hydrogen peroxide) and also high water pH when copper is present. In either of these cases the copper will turn a distinct bright green color and has the potential to turn hair green. This clearly indicates that there is in fact copper present in the Olympic pools and that copper has been oxidized and precipitated out of the water.





As of August 15, 2016 the Olympic pools have now been partially drained and refilled in an attempt to resolve the ongoing problem of green water. It remains to be seen whether this will finally resolve the problem or simply be another step along the way of this ridiculous story.















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