UV and Hydrogen Peroxide

[Cait]

Hi, I've been doing extensive research on alternative sanitizing methods and the only method that seems somewhat viable to me is the combination of UV and hydrogen peroxide. I understand hydrogen peroxide on its own is not a sanitizer, but it seems like the UV system changes the chemical structure somehow to create sanitizing capabilities?

I'm having a really hard time finding good information, so any input is greatly appreciated! This is our first season with a pool at a new house and we have a baby with eczema, so we are trying to avoid chlorine at all costs. Thanks in advance!

 

[JohnT]

Welcome to TFP!

Chlorine in pools gets a bad rap from poorly maintained water. In a normal chlorinated pool, the effective levels are just about exactly the same as what is in municipal tap water. If bathing in tap water isn't a problem, then a properly maintained pool won't be a problem.

I have well water, and can tell in a restaurant if the ice cubes in a glass of Coke are made with chlorinated water just from the smell, but I can't smell any chlorine in a glass of my pool water.

 

[Cait]

Thanks for the response! The house we recently purchased is on a well which we are thrilled about. We had installed filters on the showers in our previous home and used a filter for drinking water. So although bathing in municipal tap water isn't the end of the world, we had been going to lengths to avoid it and would much prefer to do the same in our pool.

 

[JVTrain]

My daughter has eczema. In the summer, her symptoms actually get better than during the winter. Much of this is due to seasonal humidity and more daily sunlight, from our experience, but the pool certainly does not exacerbate her symptoms. In fact, I think it also helps. In well maintained water, chlorine is the best and most reliable sanitizer.

 

[mrcarcrazy]

a family member has eczema. The pool actually helps it. Keep the levels under control and it will not exacerbate the issue. Chat with your Dermatologist for confirmation.

 

[Patrick_B]

All this testimony about eczema is absolutely anecdotal, but I have to say that my wife's grandson has the same notable improvements in the summer as well. We are obviously not medically qualified here, but it seems undeniable. Year after year we've seen this, and I don't think it is coincidence.


UV Does sanitize water, but it's not as safe as Chlorine because it can't get what might be out in the bulk water before it infects someone. If the pathogen is suceptible to UV sterilization, it must pass through the UV chamber to be killed.

 

[Cait]

Re: No chlorine in my pool to assist my ionizer nor am I sup

Welcome to TFP!

While not as disinfected as a pool with chlorine in it at all times, it's probably the next best "alternative", albeit at somewhat higher risk, for a residential low bather-load pool. If the goal was to reduce or eliminate chlorine, then it would be even better if it had a decent oxidizing (and supplemental disinfection) system such as boron-doped diamond electrodes or a properly scaled and functioning (i.e. corona discharge and drying the input air) ozonator.

Hi chem geek, I'm wondering if you think that hydrogen peroxide would be a good addition to this system (http://www.carefreeclearwater.com/products.html#model1200) as an oxidizer and supplemental disinfectant? I've seen so much conflicting information as to whether hydrogen peroxide has any disinfection capabilities and worry as you stated here that a copper/silver system would not provide enough protection. Thanks for any input!!

 

[Isaac-1]

One thing you need to be aware of is that you can't just mix and match sanitizing systems, in this case Hydrogen Peroxide is an effective Chlorine remover

 

[chem geek]

When UV interacts with hydrogen peroxide it breaks it in two to produce powerful but short-lived oxidizers called hydroxyl radicals. The irony here is that the UV in sunlight breaking down chlorine does something very similar creating both hydroxyl and chlorine radicals (technical details in this post). The chlorine radicals through a longer pathway become chloride ions. If the hydroxyl radicals don't react with any organics, then you end up with oxygen gas and chloride ions (i.e. salt). The big difference is that with chlorine the sunlight is producing these radicals in the bulk pool water so would affect areas not getting circulated while with the UV system in the pump room only the water getting circulated there is getting exposed to such radicals.

This is why we normally do not recommend either UV (with or without hydrogen peroxide) or ozone in an outdoor residential pool exposed to sunlight.

The main problem with the alternative sanitizer you are looking at is that you are focussed primarily on the oxidizing system that is in the circulation path but are neglecting to look at what is going on in the bulk pool water that has not been circulated. You still need to kill pathogens to prevent person-to-person transmission of disease and you still need to prevent bacterial and algae growth on pool surfaces where they never get circulated to the oxidizing systems. In other words, you need a bulk-water residual disinfectant. See this post for a short summary of this issue looking at different alternatives.

To have hydrogen peroxide be a residual disinfectant, you have to maintain a rather high level for it where regulations in Australia require (for the only single product approved using hydrogen peroxide) a minimum of 40 ppm and a target of 100 ppm and for some people this can be irritating.

We have no experience with how well hydrogen peroxide would control algae growth. Also, hydrogen peroxide will break down from the UV in sunlight so you would need it stabilized in some way or else it could become expensive trying to maintain its level.

Remember that with the way we promote using chlorine the active chlorine levels are equivalent to a pool with less than 0.1 ppm FC because of the use of Cyanuric Acid that has most of the chlorine bound to it and essentially inert with regard to its effects. If you wanted to minimize the amount of chlorine to even lower levels, you could use a supplemental algaecide such as Polyquat 60 added weekly or you could use a phosphate remover (or could use 50 ppm Borates, but it's unclear how much algae inhibition is available with it). This should let you maintain a lower FC/CYA ratio of 2-3% which would be equivalent to a pool with less than 0.03 ppm FC with no CYA. You won't be aware of the chlorine at all in that situation and the money you save in using less chlorine can help pay for the algaecide or phosphate remover.

 

[Cait]

Thank you everyone for your input!! I really didn't want to consider chlorine at all, but am slowly being swayed by reading all of the information on this site.

 

[Patrick_B]

As mentioned earlier, it gets a bad rap, because it is quite often horribly mismanaged. Done even reasonably well, there is nothing better for sanitizing a pool IMO. Glad you found the forum, and good to have you with us.

 

[Donldson]

I will add my own personal experience. I used to use a mineral alternative called the Pool Frog which added silver and copper and claimed I could keep the FC at 0.5ppm. I followed that and my pool felt, looked, and smelled like any other pool. Aftef a significant algae problem one Spring I found this site and since then I have maintained a proper FC/CYA ratio. My water is crystal clear, the only chlorine smell is from sunscreen reacting when first entering, and I have been accused of using no chlorine when in fact the FC was over 6ppm. It really is an entirely different experience.

I believe if you will consider giving it a shot it would be far easier to try a chlorine pool first. If you are not happy with it the switch to another sanitizer/oxidizer solution would be much simpler than the other way around. Be aware that none of the regulars here run such a system, so while people like Chem Geek can offer plenty of technical info for you we won't be much help in the actual implementation.

I do hope though that you will give the TFPC method a shot. The results really have to be experienced to understand just how different it is from a typical chlorine pool.

From my HTC One via Tapatalk

 

[Defgufman]

I will add my own personal experience. I used to use a mineral alternative called the Pool Frog which added silver and copper and claimed I could keep the FC at 0.5ppm. I followed that and my pool felt, looked, and smelled like any other pool. Aftef a significant algae problem one Spring I found this site and since then I have maintained a proper FC/CYA ratio. My water is crystal clear, the only chlorine smell is from sunscreen reacting when first entering, and I have been accused of using no chlorine when in fact the FC was over 6ppm. It really is an entirely different experience.

I believe if you will consider giving it a shot it would be far easier to try a chlorine pool first. If you are not happy with it the switch to another sanitizer/oxidizer solution would be much simpler than the other way around. Be aware that none of the regulars here run such a system, so while people like Chem Geek can offer plenty of technical info for you we won't be much help in the actual implementation.

I do hope though that you will give the TFPC method a shot. The results really have to be experienced to understand just how different it is from a typical chlorine pool.

From my HTC One via Tapatalk

I also have the Frog, and enjoyed watching the family get green hair in the summer. Since switching to TFP, we all are blond again
The chlorine works as advertised. My pool is perfect now and people are shocked that I do it with bleach.

 

[Cait]

I did look into the Frog as an option if I was going to use Chlorine, so I appreciate that feedback!

I'm still researching hydrogen peroxide and found this study which seems to indicate that combined with colloidal silver, could meet the WHO recommendations for disinfection: http://www.bioline.org.br/pdf?se08039

I didn't see anything on here about that combination (though understand probably no proponents here) so wondering if anyone has seen or looked into that?

 

[chem geek]

There is a world of difference in waiting for drinking water to be disinfected (which is what the WHO standards are about) vs. disinfecting a swimming pool because with drinking water you aren't continuously adding more bacteria and other pathogens to it. For swimming pools the goal is to have a bulk water disinfectant that kills pathogens fast enough to prevent person-to-person transmission of disease and to keep up with bather load. The WHO requirements just need bacteria to be killed faster than they reproduce while the EPA DIS/TSS-12 rules for pesticide products to be labeled as swimming pool disinfectants requires kill times with 6-log reductions (99.9999%) kill in 30 seconds for one bacteria species and under 2 minutes for another. Note that in the paper you linked to, the Nanosil hydrogen peroxide and silver combination needed to be in a concentration of at least 2% (20,000 mg/L) in order to completely kill Staphylococcus aureus and even then it took 15 minutes whereas a complete kill (6-log reduction) using chlorine at a 0.1 ppm FC active level (roughly 10% FC/CYA ratio) takes less than 2 minutes. You're pool can't have 20,000 mg/L of Nanosil in it -- more like 100 mg/L so would in effect NOT kill some of these bacteria (or would do so very, very slowly).

This paper showed that even hydrogen peroxide with silver ions did not kill quickly, but there are other papers such as this one that show at least a slow bacterial kill with silver ions. As I show in the table in this post, copper and silver ions kill much more slowly than chlorine and of course these copper and silver metal ions can both stain plaster surfaces if their concentration AND the pH are not carefully controlled. Note that silver has absolutely no effect on most viruses. This paper describes how and why Herpes Simplex Virus is not inactivated by hydrogen peroxide.

You can also read in this thread on another forum how for hot tubs hydrogen peroxide corroded components so is not recommended there.

It's your pool and you can do whatever you want with it. The EPA and state regulations are for commercial/public pools in the same way that there are regulations ensuring sanitary commercial kitchens in restaurants. At home, you can leave an uncooked chicken out for hours on wood and then cut your vegetables on that, eat, and perhaps get sick, but the government isn't going to fine you or shut your home down because it's your kitchen and you can do what you want in it.

Now to be fair, you'll run into all kinds of pseudo-science or hand-picked reports touting whatever product a vendor wants to sell. For chlorine, the main issue is with disinfection by-products, but we've looked into hundreds upon hundreds of scientific papers in peer-reviewed respected journals on these topics so with regard to chlorine DBPs you can read about that in the thread Asthma and Chlorinated Pools and the posts starting with this one on the trio of Barcelona papers.

 

[Cait]

Chem Geek, thank you for the detailed response and the links!

Looking at your table in the EcoSmarte thread about the chlorine/ copper/ silver kill times, I'm wondering since chlorine only kills certain viruses (VSV, Herpes, Vacciniavirus) at greater than 1500 minutes, wouldn't a pool UV filter kill those in similar if not less time? That is pretty scary just to consider that it takes that long for apparently any method to kill Herpes.

Thanks again!

 

[Patrick_B]

Here is the issue, and lets assume UV kills whatever instantly.

That pathogen has to pass through the UV chamber, and it could very likely not make it through there for a more than ample time before it infected someone. Due to a myriad of variables, it might swim around in the pool for who knows how long. True of any pathogen provided they can survive in a pool environment. Whether any of them can I won't even speculate on, as that's not something I am knowledgeable on at all. The problem with relying on UV as a primary to kill most pathogens is a problem for the reason I outlined. Something in the bulk water might remain there for who knows how long.

 

[Cait]

Thanks, Patrick. Just so I completely understand, you're saying that even though a UV filter might filter an equivalent amount of water to the pool volume in less time than chlorine takes to kill Herpes, etc., the virus may not actually make it to the filter (since some water may not make it there)?

 

[chem geek]

Looking at your table in the EcoSmarte thread about the chlorine/ copper/ silver kill times, I'm wondering since chlorine only kills certain viruses (VSV, Herpes, Vacciniavirus) at greater than 1500 minutes, wouldn't a pool UV filter kill those in similar if not less time? That is pretty scary just to consider that it takes that long for apparently any method to kill Herpes.

You misread the table. It's "< 1500" which means "less than 1500 minutes" and it is likely significantly less than 1500 minutes since I used conservative assumptions translating the 10 minute kill time by 0.645% sodium hypochlorite (which is at rather high pH) to what would go on in pools (specifically, I didn't attribute ANY oxidation capability to hypochlorite ion and that's unrealistic). Since the adenovirus, poliovirus, coliphage, and influenza were all done at chlorine levels much, much closer to what is in pools, those much smaller numbers (1.8 to < 95) are likely to be closer to the truth for the other viruses.

Also note that the times in the table are for 3-log (99.9% kill) reductions. Roughly speaking, figure that half the viruses are inactivated every 10 minutes or so where some are killed faster and some somewhat slower, but these kill rates are still significantly faster than the hours it takes to turnover the water where a single turnover only has 63% of the water pass through a UV or ozone disinfection system. Even if the UV system killed instantly and completely, it would take 7 turnovers to have 99.9% of the water go through the system and achieve the same 3-log (99.9% kill) reduction. Even with a fast 3 hour turnover (and most residential pools have longer turnovers), we're talking 21 hours and that's assuming the pump is on all the time (usually it isn't). So you can see how ridiculous it is to rely on an in-line system such as UV or ozone to try and kill pathogens in the pool water quickly. Their only real use, mostly for commercial/public pools, is to kill the protozoan oocyst Cryptosporidium parvum which is highly chlorine resistant and is introduced by bathers with the pathogen and associated diarrhea. They are also useful in controlling chloramines in higher bather load pools especially those not exposed to sunlight. They are also useful at oxidizing chemicals that chlorine doesn't or is slow to do so.

The following table shows how much pool water gets circulated with each turnover assuming perfect mixing:

Turnovers . % Pool Water
..... 1 ............ 63.2%
..... 1.2 ......... 69.9% ... about a 0.5-log reduction
..... 2 ............ 86.5%
..... 2.3 ......... 90.0% ... a 1-log reduction
..... 3 ............ 95.0%
..... 4 ............ 98.2%
..... 4.7 ......... 99.1% ... around a 2-log reduction
..... 5 ............ 99.3%
..... 6 ............ 99.75%
..... 7 ............ 99.91% ... around a 3-log reduction
..... 8 ............ 99.97%
..... 9 ............ 99.988%
..... 9.3 ......... 99.991% ... around a 4-log reduction
.... 10 ........... 99.995%
.... 11 ........... 99.9983%
.... 11.6 ........ 99.9991% ... around a 5-log reduction
.... 12 ........... 99.9993%
.... 13 ........... 99.99977%
.... 14 ........... 99.99991% ... around a 6-log reduction

So keep in mind that chlorine does 6-log reductions for fecal bacteria in under 2 minutes (and Pseudomonas in around 3 minutes) while it would take a UV or ozone or other in-line systems 14 turnovers of the water to accomplish that same reduction so at a fast 3 hours per turnover that's 42 hours running the pump 24/7! Note that bacteria double in population every 15-60 minutes in their maximum growth phase so just to barely keep the bacteria at bay one must have a 0.5-log reduction (68.4% kill) that is at least that fast and that's roughly 1.2 turnovers. Pools don't have such fast turnovers (spas do, however).

Finally, many pathogens require surfaces to grow or can just get stuck there and such pathogens NEVER get circulated to the in-line disinfection system. This is why a bulk-water residual disinfectant is required.

 

[Patrick_B]

Thanks, Patrick. Just so I completely understand, you're saying that even though a UV filter might filter an equivalent amount of water to the pool volume in less time than chlorine takes to kill Herpes, etc., the virus may not actually make it to the filter (since some water may not make it there)?

Precisely, or...perhaps not for some time which might be a long time. Free Chlorine is always everywhere in the water.