Role of UV in UV + H2O2 systems – DSP 39

Hydrogen Peroxide and UV are a popular combination for water treatment among float centers. What exactly does it do, though? Fortunately, Ashkahn is the wiz we need to explain the chemical reaction process that takes place when both these things are used to treat your water.

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Transcription of this episode… (in case you prefer reading)

Graham: Our question for today is from someone who is curious about the role of UV in UV plus H2O2 systems.

Ashkahn: Okidoky, so, “What does the UV do in the UV H2O2?”

Graham: First, what the heck is UV and H2O2, I guess?

Ashkahn: All right, UV stands for ultraviolet, which is ultraviolet light, which is a spectrum of light.

Graham: Which, in this case, is a UV light filter, is that what they call them?

Ashkahn: Filters.

Graham: No, just UV light mechanism.

Ashkahn: I think the bulb just produces that spectrum of light.

Graham: What’s the name for the actual container?

Ashkahn: Yeah, UV light unit.

Graham: Okay, anyway, so what’s the role of that UV unit?

Ashkahn: H2O2 means hydrogen peroxide. Let’s clear the acronyms out of the way here.

Graham: “In” refers to something being inside something else.

Ashkahn: This is an interesting question and it’s actually a really good one for everybody in the industry to get right, because this is one of those things where if you’re talking to someone from the health department world and you’re not phrasing this the right way, then you get side ways glances and you get people nervous about your operations and stuff like that.

Graham: Maybe even coming down a little harder on you than they should.

Ashkahn: Right.

Graham: You’re free to listen to this one a few hundred times. Make sure you’re really comfortable with it.

Ashkahn: Basically the UV and hydrogen peroxide when used together is really the only way you want to use hydrogen peroxide. Kind of the big lesson to take out of this is that it really seems that hydrogen peroxide is probably not strong enough by itself to meet the level of cleanliness that we’re looking for in the water. The key takeaway is don’t just use hydrogen peroxide by itself. Really, UV and hydrogen peroxide kind of form this system together. In that system, the UV is doing the heavy lifting.

Graham: If anything, you should almost consider it a UV system with hydrogen peroxide

Ashkahn: And they play different roles. They definitely help each other and they work well together. Basically UV is doing the actual killing of the virus. Technically, it doesn’t really kill them. UV, most effectively, as far as I know, basically stops the reproduction of various kind of pathogens and bacteria.

Graham: Bugs, almost everyone likes to call them.

Ashkahn: “Bugs” in the water. The UV light does a good job of just destroying the RNA and sometimes the DNA of these different bugs. So, while they may still be present in the water, they’re effectively not able to grow to point of being harmful to somebody, in most cases. That’s actually different than how chlorine and bromine work, for example. UV has the special way of killing stuff.

Graham: As a result, it works really effectively against things that even chlorine and bromine don’t work against. As long as you’re able to keep the right intensity of light, and pretty much as long as the UV is doing its stuff, the water that’s passing through that UV light comes out the other end, pretty safe.

Ashkahn: There’s a lot of details about UV lights working correctly and stuff like that. I wish we were able to go into this topic with more detail.

Graham: That’s another daily solution.

Ashkahn: So you have a UV light, it’s all working correctly and set up and powerful enough and all that sort of stuff. If it’s all doing the things that it should be doing, then it’s basically taking those bugs and destroying their ability to reproduce. Then the hydrogen peroxide comes in and does something slightly different, which is really helpful, which is that hydrogen peroxide seems to be a really good oxidizer, which is a word that you’ll hear a lot if you are ever dealing with this stuff or talking to health departments. These different words have really specific meanings to them — you can’t just say “disinfectant” and “cleaner” and “sanitizer” and” sterilizer” interchangeably. Those all kind of mean different things to health departments when you’re talking to them.

Graham: If you do think they mean the same thing, maybe we should take a second to actually describe.

Ashkahn: Disinfection is the one that you hear the most from health departments. That has a very both technical and often legal meaning behind it, which that a disinfectant (at least if we’re talking about the pool and spa world for a second) is often what health departments are trying to categorize this under. If you’re talking pool and spa stuff and you’re talking to a health department person and they say the word “disinfectant”, they’re actually looking for something registered by the EPA to be a disinfectant in your specific application.

Chlorine is a registered disinfectant for pools and spas, which means that the EPA has gone through a process where they have approved it for use. Then, most health departments, if not all of them in the United States, are legally required to only allow these EPA-registered disinfectants to be used for these applications. It often means that it’s killing a certain level of a quantifiable way of killing stuff, too. They will measure against certain bugs and they will measure a certain amount of how fast and how much it can kill those bugs. If it meets all those technical guidelines, then you can call it a disinfectant.

You can’t just call anything a disinfectant. Often ,what happens is that people will say, “Hydrogen peroxide is the disinfectant I’m using.” That’s where you start getting into trouble because it’s not a registered disinfectant, not even for pools and spas, and not for tanks.

Graham: The only one I know of is it’s registered as a hard surface disinfectant.

Ashkahn: It is registered as a hard surface disinfectant.

Graham: Yeah, exactly.

Ashkahn: Often mixed with other stuff.

Graham: So you see, with a little research you might find things of hydrogen peroxide as disinfectant. But that’s not for the applications that we’re talking about.

Ashkahn: Yeah exactly. So that’s one place where if you were to approach a health department and say, “Hey, I’m using hydrogen peroxide as my disinfectant here,” they would be like, “I can’t allow you to do that.” It’s funny, because you can actually just say, “I’m using hydrogen peroxide as an oxidizer in here.”

Graham: Then they’ll nod, “Oh yes, well that makes sense. Yeah.”

Ashkahn: It is amazing how much of it just comes down to the language that you’re using. Oxidizers, specifically, are something that burn up organic materials in the liquid that they’re in. A lot of these things are combinations. Like chlorine can kill stuff and is a good oxidizer, as well as ozone, too. I think ozone is a decent oxidizer.

UV is not a great oxidizer, it’s just shooting this light rays at things. The hydrogen peroxide works well in conjunction with it because it can take those things that the UV light has blasted and burn them up. Get that stuff out of the liquid. They work well as a pair for that reason. They also work well as a pair because UV and peroxide, when used in combination, when that UV light hits the hydrogen peroxide, it creates these things called hydroxo radicals.

Those hydroxo radicals are really good at killing stuff. They seem to be very effective. They’re very hard to measure. They only last milliseconds from what we’ve heard.

Graham: You can almost view it as a boost to your UV light rather than as a boost to your hydrogen peroxide. It’s not like you super charge your H2O2 and now you have these super H2O2 molecules floating around in your water.

Ashkahn: It’s a synergistic effect. The effect you get from it is better than some of the UV by itself and peroxide by itself. It actually creates this very strong sort of thing in there.

Graham: You can almost view it as, in my mind. as supercharging the UV experience. That’s how I view it, like the hydroxo radicals are created right there at the UV light.

Ashkahn: Sure, in that sense yeah. That’s an important distinction, because they only last for such a short period of time, that these things are probably only really affecting stuff that’s moving through your filtration system.

Graham: Pretty much right when it’s going through the UV light is also when the hydroxo radicals are doing their thing. It’s not like you end with that residual of hydroxo radicals that are floating around exactly.

Ashkahn: Puts a little bit more pressure on making sure the liquid moves through your filtration system. There is a greater importance to your turnovers and stuff like that when you’re relying on those hydroxo radicals and UV, in general. That’s the thing with UV. It’s not like chlorine and bromine are just in the water. You can take a sample of any section of water in a pool or spa and there is chlorine and bromine in it.

While as the UV light is only exposed to things that are passing straight through that UV unit. There is not UV waves emanating out into the rest of your basin or whatever. It’s puts different importance on different parts of your filtration system. But the really important thing to realize here is that it’s UV is leading the way there. When you think about these UV peroxide systems, you should consider UV as the front man for all of this and peroxide as the side-car person hanging and helping out.

Graham: Which is why I have this point, I always calls UV H2O2 systems. Those H2O2 UV systems, which I guess mathematically is the exact same thing. “UV H2O2 systems” puts the importance at the right part of that.

Ashkahn: Or, really just talking about peroxide without the UV as well. If you’re talking to a health department and you’re talking about how you’re using hydrogen peroxide, just make sure you’re talking about it as a system and these two things being used in conjunction with each other, and not just like peroxide, by itself, is what’s doing the whole job in there.

Graham: If you’re just using peroxide by itself, you should probably get a UV unit hooked up to that.

Ashkahn: This is based on a lot of the information we know about hydrogen peroxide in other applications. There hasn’t been a lot of testing in the float industry.

Graham: Yeah, it could totally come out that it is actually okay to use hydrogen peroxide by itself. Just making a huge leak from our current level of understanding. We don’t know what the ultimate conclusion will be but my guess is that we’ll find that it’s probably not okay just by itself. That’s my hunch as of right now.

Ashkahn: And most people, the people who are smarter than us and know more about it than us, they seem to have that conclusion. I’ve certainly never talked to someone who’s come away from this thinking like the peroxide is probably fine by itself. It’s usually the conclusion. There are hunches that you need the UV in there and definitely that’s the case for health departments too. They will certainly assume that. If you’re talking about H2O2 alone as being enough like that’s there again, those side long glances and disapproving crippling of their fingers. So yeah, what’s the role of UV? It’s a big one, big role.

Graham: Big role. There you have it.

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