Ultra Violet Rays: What Are The Facts?

UV light has been used to sterilise water in fish tanks for years. Do a Google search, you'll be amazed!

I agree. Ultraviolet rays can disintegrate microbe cells and hence can make the water sterile. Ultraviolet reacts with Oxygen and makes Ozone which is also helpful in germ killing but it is bad for human health. There also may be some formation of H2O2 or Hydrogen peroxide, which is also effective germ killer. Cell membrane made of lipid proteins of microbes can be punctured by high ionic concentration in water caused by UV. UV also harms our skin if exposed to excessive UV and can cause skin cancer.

Ultraviolet reacts with Oxygen and makes Ozone? Interesting. I work in pharmaceutical manufacturing and we use UV light as both purification and ozone destruct in our water purification process. We sanitize with ozone every two weeks and return to UV sanitization during normal use. However, the UV clearly destroys ozone injected into the process. The unit, from US Filter, is called an ozone destruct.

Could UV both create and destroy ozone (O3)?

So some UV can have 40 times the energy of visible light. This is why UV can cause skin damage while visible light doesn't. However, UV is aborbed fairly quickly by water so I'm having trouble seeing how it can purify water.

Dear Roger,

No, not 40 times. UV light has only 2-5 times the ennergy of the visible light. Energy in eV is calculated by formula 12400 / wavelength (A) = E (eV). Red color light 600nm or 6000 A will have about 2.06 eV energy. 250nm or 1500 A mercury UV will have 9.6eV. Glass will block this 250nm UB and hence only Quartz or fuzed silica can permit it. UV also get absobed in air if it belongs to greater than 9eV as it will ionize Nitrogen and lose energy. No higher energy UV can travel very far as Photoelectric cross section is very high for it.

If ebergy reaches keV then it is called x-ray. Vacuum UV can have high energy up to 100eV. That way your gess is right. This is not so for UV lamps you generally see. Vacuum UV is generated by ark discharge of high voltage in Plasma state of gas and deeper electrons are used to get more energy in vacuum. How to have some gas and yet make UV in Vacuum is a technology issue. There are ziant UV sources of the size of a room.

Some UV sources are also used in making the epoxy resine harder. UV also comes in ark welding and hence, all welders need protection. You might have seen them coverting their eyes with dark glass.

It is the white LiF powder in the FL bulbs that converts UV into white light else lamp actually have UV inside. Some UV leaks out and is really bad thing. It generates Ozone in air, which kills our brain directly. Welders can be said to have almost no brain as they smell too much UV. They may become neuron starved brain.

So I'm not sure if it's a good idea to drink water after purification maybe just a little ? I'm still confused how it actually does it and what are its limitations sure the fish tank sound fine but for drinking water sounds dangerous and how dirty can be cleaned ? Certianly not sewerage but maybe light contamination ? I think the dentist used the same to harden fillings I thought it was black light but I guess it was ultra violet .Are there other uses ,who would have thought a basic light was so powerful.

No. You can drink it. Water is better for drinking after UV exposure.

Shyam,

I think you may have misunderstood me. I was treating UV as a range, not a particular value. The range can go from ~10nm to ~400nm. The energy for 10nm is about 124 eV wheras for visible tops out at about 3 eV.

What I said was "some" UV can have 40 times the energy of light. Clearly 124 eV is 40 times larger than 3 eV, so my statement was correct.

What I'm not sure about is the absorption of UV in water. I always thought that UV is absorbed fairly quickly in water, and if that's the case, how can it get to the algae/bacteria to kill it?

Dear Roger,

Even if you generate 124eV UV, it will not enter water depth and will be absorbed in just 1mm thick water or glass. High energy UV can't travel distances.

Perhaps if you are using such a high energy UV on thin layer of water, then it will be highly effective, but is also dangerous if you smell the air around it.

To let you have an estimate, a 100W UV pen lamp can cause greater than 1000ppm Oxone per hour. Permitted level is only 0.1ppm per hour. If you are keeping UV lamp ON for an hours will make you shacky / brainless dumb. Effect is long term neuron damage so just avoid smelling the ark discharges and do not keep the UV lamps ON for longer period in open air without air circuilation.

UV sure is not for fun. It is brain killer.

Yes, which is exactly my point, as far as I know, ALL uv is absorbed fairly quickly in water, with the higher energy UV being absorbed quickest. How can UV kill the bacteria if it is absorbed by the water? It must work since so many places recommend it. Is it that the UV lamp kills organisms in the water within an inch of it and water circulation eventually brings all the water near the UV source?

I think these UV purifiers act more like a channel within which the water is passed. Rather like a pipe with a UV light inside. Within fish tanks, I imagine that since there's circulation. Much of the water in the tank will pass by the UV light sooner or later.

One other thing, I'm guessing that there are a lot of microorganisms that are uneffected by UV. Many of these are parasites, which can protect themselves from environments they don't like. When things get better, they come out of a 'spore' state and start messing with ya again.

Vermin-

And what about that ummy smell that comes from every laser printer in the office? Is this why American business is so backwards? May explain the existence of the 'Peter Principal.'

Vremin-

<UV also comes in ark welding and hence, all welders need protection. You might have seen them coverting their eyes with dark glass.>

It is true welders wear dark glass to protect them from UV, but the real reason is so that they can see what they are doing. It's like looking at the sun. Been there.

<Welders can be said to have almost no brain as they smell too much UV. They may become neuron starved brain.>

Perhaps you can clarify what you mean by, "smelling too much UV". This is news to me. I always thought the danger was from inhailing gases from melted metal. What does UV smell like? Maybe that's what happened to me. VBG

The goggles actually have both purposes: Granted, you cannot see without them, but if you weld for even a short time without them your eyes will itch. In fact, many complain about the relatively new automatically darkening hoods: the delay time is enough (although much less than a millisecond) that people who use the hoods all day end up with itchy eyes. (For those non-welders among you: the conventional lenses are so dark that you can't see anything through them until you start the arc... including the location where you are intending to start the arc. Therefore, the auto-darkening hoods are really attractive.)

I am a welder part of the time, and think the reason I have no brain has little to do with smelling UV. Actually I think by "smelling UV" he meant "smelling ozone"

is there anything called welder's helmet or

specialised gogles with light sensor to block arc light

before it reaches the eyes?

Not unless any type of circuitry or glass material is faster than the speed of light.

Ultraviolet rays is electromagnetic radiation just passed the high visible part of the spectrum. They are harmful! If you watch a welder working from across the street, guaranteed, the next morning, you'll feel as if someone has sprinkeled sand in your eyes: they have been burned by the ultraviolet from the welder's torch. Each year, tens of thousands of new cases of skin cancer are reported; mostly due to UV sun exposure. 'Friendly, ol Sol wants to kill you.' UV radiation is quite capable of destroying the structure of DNA, thus it's ability to kill bacteria and virues. Water treatment, hospitals, and some foods are subjected to UV for the purposes of disinfecting by completely disrupting the little critters. Vermin-

specific wavelengths of ultraviolet light (I'm pretty sure it's 248 nm) both generates AND destroys ozone (O3) from molecular oxygen (O2) because 248 nm is the wavelength to split the O-O bond. Once the bond is split, atomic oxygen is present (at a very low concentration) but atomic oxygen will bond to molecular oxygen, making ozone. If the 248 nm photon happens to hit ozone, though, the third oxygen atom will be removed. That's how it can generate AND destroy ozone. Ozone itself will react with just about any carbon-carbon double bond, and it is an excellent way to remove bacterial contaminants from water. Many bottled water labels now include "purified by ozonolysis" or "ozone added" which simply mean that at one time, ozone was made in the water. It definitely is not present anymore when you start drinking it! ultraviolet rays can also do a lot of damage by themselves to DNA and proteins in the bacteria (or in human cells, too leading to problems from sunburn all the way to skin cancer), but the majority of the damage in water purification is probably oxygen-mediated, because it's much faster to tear the bacterial cell apart (with ozone) than it is to give it a mutation (that prevents it from making the next generation).

There is a wealth of information regarding this subject on the web. One of the best can be found at http://www.wastewaterdepot.com/uv_technical.html In recent news, the development of Deep UV LEDs (DARPA program)has lead to a new generation of products for use in water production. Is anyone aware of other applications for Deep UV LEDs?

Good morning every body. I have a pond with fishes and the water gets very green because the algae growth. Are this UV lamps good for controlling algae or is just good for controling desease in fish? I have used some chemicals and have just installed a sun shade for stopping the algae but I´m loosing the sun light reaching the pond. I work at a remote Hydro power plant so we have to buy bottles of potable water for drinking and cooking but we have to use UV purifiers and Filters for the Bathroom water and it has work fine for long time but water is not good for human comsuption ( no body has been reporte ill because our water yet )... But algaes are something different... any help? Regards Luis

Luis There is a non polluting product that you can put in the water to control algae .It colors the water so sunlight cannot feed the algae growth kind of like putting sunglasses on the pond.I hope thats helpful if you have trouble finding some I could find it for you .I think its reasonably priced and could be easily shipped .

Buenos dias Traditional. Thanks for your idea... Would you please send me the name or the address so I can buy some of it? Regards... I will let you know if it work, my mail is llizarraga@cableonda.net Luis

I'll check it out it's been awhile so give me a couple days

Thanks for your time and help. Luis

Dear Bob, Yes this new area now is a great help. Most of these LEDs are actually Quantum Dot devices capable to convert low energy light into very high energy by multiple photon energy combining process in a small cavity called Quantum Dot.

There is a company Called Nichia in Japan where this research was originated in special semiconductors. Now this technology is wide spread.

If you have a diomond LED then it will be 5eV as band gap is so high. Other semiconductor may have more energy gap.

More on Quantum Dot UV LEDs is here.

http://www.llnl.gov/str/Lee.html
http://www.fujipress.jp/finder/xslt.php?mode=prese nt&inputfile=LASSJ003200060006.xml