First of all Bob Fenner is a chemist, not only is he a chemist he was a chemistry teacher. I believe he knows chemistry quite well if he can teach it. Secondly, you keep focusing on the 254 nm, which is the peak wavelength, not the only wavelength produced. This data clearly states the 254 nm wavelength was applied, which there are specific lamps that only emit this wavelength. The wavelengths produced by average aquarium sterilizers range from 185-254 nm, which means shorter wavelengths are emitting O3 and reacting before the longer wavelengths can destroy the O3. All you are proving is that wavelengths at the peak of the lamp are not producing O3, we have already established that. Why do you think it is so improbable that the shorter wavelengths would find an O2 molecule? The water in our reef tanks should be close to saturation with O2, especially when plumbed after a protein skimmer ,which would be ideal placement and, saturated with O2.
uv sterelizer
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FWIW, I think you might find better fights to fight than this one, but I'm happy to oblige. I love chemical debates. 
First of all Bob Fenner is a chemist, not only is he a chemist he was a chemistry teacher.
Is he? My reading of his bio at wet web media (which admittedly might be wrong) said he had life science degrees, with a teacher certification to teach physics, biology and chemistry. IMO, that does not make someone an expert chemist. Ozone in seawater is an expert topic, not something one learns even as an undergraduate chemistry major, which he is not.
UV sterilizers do produce small amounts of ozone which increases oxidation of organics,dissolved oxygen,
I'd be happy to attack all of the inaccuracies in your recount of his comments if you like. Let's start with the comment about boosted O2. It is ridiculous, IMO. Yes, it could possibly happen if you made O3 in the air, drive it into seawater, and then the O3 broke down to make O2. But he seems to be forgetting that the ozone came by breaking down O2 to begin with.
So if by some chance I am wrong and one could make O3 in seawater with UV, then you broke down O2 in the water to do it. So even if every single O3 molecule broke down to O2, you would not get more O2 than you started with. And since some will break down to other things by very well known reactions that I detail in my ozone articles, you must necessarily have a lower O2 concentration than you started with.
Does that not make sense to you?
First of all Bob Fenner is a chemist, not only is he a chemist he was a chemistry teacher.
Is he? My reading of his bio at wet web media (which admittedly might be wrong) said he had life science degrees, with a teacher certification to teach physics, biology and chemistry. IMO, that does not make someone an expert chemist. Ozone in seawater is an expert topic, not something one learns even as an undergraduate chemistry major, which he is not.
UV sterilizers do produce small amounts of ozone which increases oxidation of organics,dissolved oxygen,
I'd be happy to attack all of the inaccuracies in your recount of his comments if you like. Let's start with the comment about boosted O2. It is ridiculous, IMO. Yes, it could possibly happen if you made O3 in the air, drive it into seawater, and then the O3 broke down to make O2. But he seems to be forgetting that the ozone came by breaking down O2 to begin with.
So if by some chance I am wrong and one could make O3 in seawater with UV, then you broke down O2 in the water to do it. So even if every single O3 molecule broke down to O2, you would not get more O2 than you started with. And since some will break down to other things by very well known reactions that I detail in my ozone articles, you must necessarily have a lower O2 concentration than you started with.
Does that not make sense to you?
Secondly, you keep focusing on the 254 nm, which is the peak wavelength, not the only wavelength produced. This data clearly states the 254 nm wavelength was applied, which there are specific lamps that only emit this wavelength. The wavelengths produced by average aquarium sterilizers range from 185-254 nm,
I don't deny that germicidal lamps may produce many wavelengths, including 185 nm, and when run in air, these will produce ozone. Some do not. This one specifically says it does not produce ozone when run in air:
http://www.negativeiongenerators.com/UV-C_spectrum.html
I don't deny that germicidal lamps may produce many wavelengths, including 185 nm, and when run in air, these will produce ozone. Some do not. This one specifically says it does not produce ozone when run in air:
http://www.negativeiongenerators.com/UV-C_spectrum.html
Why do you think it is so improbable that the shorter wavelengths would find an O2 molecule?
Because there are many other very highly absorbing molecules also present at vastly higher concentrations. Water absorbs 185 nm radiation, and is present at several hundred thousand times the concentration of O2. And many of the molecules in seawater are very strong absorbers of UV light and undergo their own chemistry. If you search through the literature of UV effects on seawater, you see them all and discussions of what happens to them, from oxidation of organics to iron.
Why do you suppose that searching through the literature turns up ZERO mention of ozone being generated in seawater, and lots and lots of papers detailing other chemistry taking place?
Do you believe Bob has an insight here that the researchers making a living at studying this phenomenon do not?
Did you choose to not believe the paper I posted, instead choosing to believe Bob's comment without any supporting evidence?
Because there are many other very highly absorbing molecules also present at vastly higher concentrations. Water absorbs 185 nm radiation, and is present at several hundred thousand times the concentration of O2. And many of the molecules in seawater are very strong absorbers of UV light and undergo their own chemistry. If you search through the literature of UV effects on seawater, you see them all and discussions of what happens to them, from oxidation of organics to iron.
Why do you suppose that searching through the literature turns up ZERO mention of ozone being generated in seawater, and lots and lots of papers detailing other chemistry taking place?
Do you believe Bob has an insight here that the researchers making a living at studying this phenomenon do not?
Did you choose to not believe the paper I posted, instead choosing to believe Bob's comment without any supporting evidence?
Why do you think it is so improbable that the shorter wavelengths would find an O2 molecule?
The real kicker here is not that some UV might not find O2, it is that if it does and breaks down to oxygen atoms, that these oxygen atoms, which are very highly reactive, will find its long, long way to another O2 before it reacts with something else.
In air, the O2 is 21% of what is there, and most of the remainder of what is there (N2, Ar, etc) is not reactive. So it is fairly easy for O to find an O2 before something else happens to kill it.
In seawater, that is not the case. O atoms will very rapidly react with a host of species in seawater, including organics, metals such as manganese, and even some nutrients such as nitrate and nitrite.
This article, for example, is a typical one that suggests that UV forms several things in seawater, none of which are ozone:
Nitrate photolysis in seawater by sunlight. Zafiriou, Oliver C.; True, Mary B. Dep. Chem., Woods Hole Oceanogr. Inst., Woods Hole, MA, USA. Marine Chemistry (1979), 8(1), 33-42.
Abstract
The photolysis of NO3- in seawater by sunlight was re-examd. by using abiotic seawater and naturally occurring concns. Photochem. formation of NO2- from NO3- was obsd. First-order NO3- photolysis rate coeffs. calcd. from NO2- appearance (cor. for concomitant NO2- photolysis) ranged from 0 to 2.3/yr, median 0.7/yr. The coeffs. did not correlate well with water chem., but decreased with increasing light dose. A first-order rate coeff. of 0.4/yr was calcd. for the primary photochem. process NO3- + h.nu. = NO2- + O(3P) under sea surface equatorial insolation and cloudiness conditions. However, no significant NO3- concn. decreases could be detected, suggesting an upper limit for the net first-order NO3- loss rate coeff. of 0.3/yr. The data thus imply some conversion in the reverse sense: NO2- + h.nu. NO3-. If the median rates est. applies to surface oceanic conditions, NO3- photolysis proceeds at roughly 0.02-0.5% of the rate of N incorporation during primary prodn. It is thus not a significant NO3--N sink. Since such reactive species as at. O, NO2, and OH radicals are produced, the reaction may have significant consequences in seawater. However, NO2- photolysis is almost certainly a more significant process.
The real kicker here is not that some UV might not find O2, it is that if it does and breaks down to oxygen atoms, that these oxygen atoms, which are very highly reactive, will find its long, long way to another O2 before it reacts with something else.
In air, the O2 is 21% of what is there, and most of the remainder of what is there (N2, Ar, etc) is not reactive. So it is fairly easy for O to find an O2 before something else happens to kill it.
In seawater, that is not the case. O atoms will very rapidly react with a host of species in seawater, including organics, metals such as manganese, and even some nutrients such as nitrate and nitrite.
This article, for example, is a typical one that suggests that UV forms several things in seawater, none of which are ozone:
Nitrate photolysis in seawater by sunlight. Zafiriou, Oliver C.; True, Mary B. Dep. Chem., Woods Hole Oceanogr. Inst., Woods Hole, MA, USA. Marine Chemistry (1979), 8(1), 33-42.
Abstract
The photolysis of NO3- in seawater by sunlight was re-examd. by using abiotic seawater and naturally occurring concns. Photochem. formation of NO2- from NO3- was obsd. First-order NO3- photolysis rate coeffs. calcd. from NO2- appearance (cor. for concomitant NO2- photolysis) ranged from 0 to 2.3/yr, median 0.7/yr. The coeffs. did not correlate well with water chem., but decreased with increasing light dose. A first-order rate coeff. of 0.4/yr was calcd. for the primary photochem. process NO3- + h.nu. = NO2- + O(3P) under sea surface equatorial insolation and cloudiness conditions. However, no significant NO3- concn. decreases could be detected, suggesting an upper limit for the net first-order NO3- loss rate coeff. of 0.3/yr. The data thus imply some conversion in the reverse sense: NO2- + h.nu. NO3-. If the median rates est. applies to surface oceanic conditions, NO3- photolysis proceeds at roughly 0.02-0.5% of the rate of N incorporation during primary prodn. It is thus not a significant NO3--N sink. Since such reactive species as at. O, NO2, and OH radicals are produced, the reaction may have significant consequences in seawater. However, NO2- photolysis is almost certainly a more significant process.
The abstract you included referred to sunlight at sea level, we have an ozone layer in our atmosphere protecting us from those harmful shorter wavelengths we've been discussing. Measuring the dynamics at sea level versus inside a UV sterilizer makes this abstract useless in our debate. The increased oxygenation comes from destroying the organic compounds and organisms that use O2 in our systems,enabling better saturation.
The increased oxygenation comes from destroying the organic compounds and organisms that use O2 in our systems,enabling better saturation.
Killing bacteria in a UV sterilizer provides more organic matter in the form of dead bacteria, just waiting to be oxidized by O2. Are you claiming that UV sterilizers are so good at oxidizing organics that despite generating new soluble and particulate organics from the killed microorganisms, that there is a net reduction of dissolved organic material? That seems somewhat unlikely to me, as even direct use of ozone in a marine system does not result in reduced total organics, but if they do...
The increased oxidation of organics by UV, which I agree certainly does happen, will simply accelerate the consumption of O2. That is the essence of oxidation. I think it doesn't make sense to say that you can accelerate the consumption of O2 by oxidizing organics, and that acceleration will somehow result in increased O2 in the tank. The O2 being used came from the tank water, and you used it. You might replace it with a skimmer or photosynthesis, etc, but it does not seem to be any sort of net addition of O2. It seems a likely net sink.
So, the only think left to support your (or Bob's) hypothesis of increased O2 is that the microorganisms that were killed are not using O2 any more, allowing O2 to rise. That presumes that suspended bacteria are a big part of the total O2 users in the tank, which I disagree with unless you are having a bloom of suspended bacteria, but even so, you have taken their bodies, ripped them apart in the sterilizer, and dumped them back into the system for more bacteria to metabolize the dead bits (including the high proportion of bacteria in the system which are attached to surfaces and not impacted by a sterilizer unless it provides more organic material for them to consume).
In short, you are claiming that killing bacteria and leaving the dead bodies in the water will reduce O2 consumption by their no longer taking it in as they live, and that will allow O2 to climb.
Why would you suppose that applies to bacteria and not large organisms? Most people would not think that killing a fish and leaving the dead body in the water to decompose will raise O2 just because it is no longer breathing. The assembly of dead bacteria is no different than the fish in this analogy, and I contend it is clearly a net consumer of O2 and would, if anything, tend to recue the O2 in the tank.
Killing bacteria in a UV sterilizer provides more organic matter in the form of dead bacteria, just waiting to be oxidized by O2. Are you claiming that UV sterilizers are so good at oxidizing organics that despite generating new soluble and particulate organics from the killed microorganisms, that there is a net reduction of dissolved organic material? That seems somewhat unlikely to me, as even direct use of ozone in a marine system does not result in reduced total organics, but if they do...
The increased oxidation of organics by UV, which I agree certainly does happen, will simply accelerate the consumption of O2. That is the essence of oxidation. I think it doesn't make sense to say that you can accelerate the consumption of O2 by oxidizing organics, and that acceleration will somehow result in increased O2 in the tank. The O2 being used came from the tank water, and you used it. You might replace it with a skimmer or photosynthesis, etc, but it does not seem to be any sort of net addition of O2. It seems a likely net sink.
So, the only think left to support your (or Bob's) hypothesis of increased O2 is that the microorganisms that were killed are not using O2 any more, allowing O2 to rise. That presumes that suspended bacteria are a big part of the total O2 users in the tank, which I disagree with unless you are having a bloom of suspended bacteria, but even so, you have taken their bodies, ripped them apart in the sterilizer, and dumped them back into the system for more bacteria to metabolize the dead bits (including the high proportion of bacteria in the system which are attached to surfaces and not impacted by a sterilizer unless it provides more organic material for them to consume).
In short, you are claiming that killing bacteria and leaving the dead bodies in the water will reduce O2 consumption by their no longer taking it in as they live, and that will allow O2 to climb.
Why would you suppose that applies to bacteria and not large organisms? Most people would not think that killing a fish and leaving the dead body in the water to decompose will raise O2 just because it is no longer breathing. The assembly of dead bacteria is no different than the fish in this analogy, and I contend it is clearly a net consumer of O2 and would, if anything, tend to recue the O2 in the tank.
The abstract you included referred to sunlight at sea level,
OK, that's a fair point, the most recent abstract did try to model the various wavelengths of sunlight. It may not convince you in relation to the 185 nm light that you are fingering as the hypothesized culprit, but it shows that oxidation of organics happens through photolysis without needing to invoke ozone.
FWIW, there are not many chemical scientists interested in studying the effects of UV sterilizers on seawater (aside from the first one I posted), so some extrapolation from what is known about ozone and its formation, and about other light sources and/or applications is needed.
OK, that's a fair point, the most recent abstract did try to model the various wavelengths of sunlight. It may not convince you in relation to the 185 nm light that you are fingering as the hypothesized culprit, but it shows that oxidation of organics happens through photolysis without needing to invoke ozone.
FWIW, there are not many chemical scientists interested in studying the effects of UV sterilizers on seawater (aside from the first one I posted), so some extrapolation from what is known about ozone and its formation, and about other light sources and/or applications is needed.
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No, I'm not claiming that they are that efficient, I know that they are not that efficient. Sterilizers can only destroy some of what passes through it and most of the aquariums bio mass is attached to a substrate. The "dead bodies" aren't in huge numbers causing the O2 to be depleted. The "dead bodies" are then easily skimmed as they rag doll their way up into your collection cup, being removed forever.
The "dead bodies" aren't in huge numbers causing the O2 to be depleted. The "dead bodies" are then easily skimmed as they rag doll their way up into your collection cup, being removed forever.
Recent studies seem to suggest that only a small fraction of the total organics in aquarium water can be skimmed out by typical skimmers. Even if that number is half, or 3/4 or 7/8, there's still the others left behind so I think this process is still going to cause a net loss of O2. Other reefers don't skim at all. If your hypothesis requires a skimmer to have a UV sterilizer succeed in adding O2 to an aquarium, that's probably worth mentioning when you advise folks.
Recent studies seem to suggest that only a small fraction of the total organics in aquarium water can be skimmed out by typical skimmers. Even if that number is half, or 3/4 or 7/8, there's still the others left behind so I think this process is still going to cause a net loss of O2. Other reefers don't skim at all. If your hypothesis requires a skimmer to have a UV sterilizer succeed in adding O2 to an aquarium, that's probably worth mentioning when you advise folks.
Recent studies seem to suggest that only a small fraction of the total organics in aquarium water can be skimmed out by typical skimmers. Even if that number is half, or 3/4 or 7/8, there's still the others left behind so I think this process is still going to cause a net loss of O2. Other reefers don't skim at all. If your hypothesis requires a skimmer to have a UV sterilizer succeed in adding O2 to an aquarium, that's probably worth mentioning when you advise folks. [/B][/QUOTE]
My hypothesis included skimming right from the beginning, and was reiterated later in the thread.
My hypothesis included skimming right from the beginning, and was reiterated later in the thread.
My hypothesis included skimming right from the beginning, and was reiterated later in the thread.
I guess I'll just agree to disagree with your and Bob's assertions and leave it at that, but to be fair, you said it increased skimming (another assertion that I think may not be accurate), and didn't say that increased O2 in your hypothesis was dependent on skimming. You even proposed the best placement of the UV was after the skimmer, not before it, so you could send maximal O2 into the UV to form ozone, rather than the reverse of sending the dead bacteria directly to a skimmer. Folks without skimmers may be among those most interested in raising O2 by other means, and so would not benefit in your hypothesis, and would suffer substantially in mine.
FWIW, someone without a skimmer could benefit in terms of O2 levels from ozone use by other means, such as ordinary ozone reactors.
I guess I'll just agree to disagree with your and Bob's assertions and leave it at that, but to be fair, you said it increased skimming (another assertion that I think may not be accurate), and didn't say that increased O2 in your hypothesis was dependent on skimming. You even proposed the best placement of the UV was after the skimmer, not before it, so you could send maximal O2 into the UV to form ozone, rather than the reverse of sending the dead bacteria directly to a skimmer. Folks without skimmers may be among those most interested in raising O2 by other means, and so would not benefit in your hypothesis, and would suffer substantially in mine.
FWIW, someone without a skimmer could benefit in terms of O2 levels from ozone use by other means, such as ordinary ozone reactors.
Randy,
Yes, at this point we should agree to disagree. The sterilizer should be plumbed lastly so the cleanest water returns to your system. UV DOES help reduce the DOC levels, so even someone without a skimmer would benefit(supplemented with carbon). As I stated in my very first post, I prefer ozone over UV by far. But upon re-educating myself on UV sterilization, it doesn't seem too shabby after all.
Yes, at this point we should agree to disagree. The sterilizer should be plumbed lastly so the cleanest water returns to your system. UV DOES help reduce the DOC levels, so even someone without a skimmer would benefit(supplemented with carbon). As I stated in my very first post, I prefer ozone over UV by far. But upon re-educating myself on UV sterilization, it doesn't seem too shabby after all.
hawkfishman
New member
i run mine full time on my fowlr, and for a couple days a month on my reef tank or when i see anything which hasn't happend in years.
Nanz
Premium Member
You might want to consider the cost of changing the UV bulb every 3-6 months because they are expensive. If they really did produce a noticable amount of Ozone they might be worth it but the way Randy describes it I have to agree it seems very unlikely that a UV sterilizer is going to produce much if any Ozone.
I cannot disagree with that and it makes more sense than anything else posted.
I cannot disagree with that and it makes more sense than anything else posted.
