UV for killing bacteria in water

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I have sold, installed and serviced many hundreds of UV lights, some under state DEP supervision.
UV does not kill, it prevents reproduction.
UV lights come in Class A and B versions. You want a Class A. Only A can be used for the control of cysts and crypto and IIRC none are rated for virus control.
Plastic will not last long in the strength, dose and specific narrow band UV light produced by any UV light used for potable water treatment; measuring that in hours to a few days would be my guess. It will burn your skin and eyes much faster and worse than the arc from any welder.
They all use crystal quartz for both the lamp sleeve and the lamp. It is the photochemically clear material.
UV is approved for bacteria remediation in all US States. It works very well IF it is applied correctly, there are numerous pretreatment requirements, and IF the light is maintained properly on a timely basis.
All UV lights must be properly sized for the peak demand gpm of water flow they are expected to treat.
And some of the statements and advice in this thread is WAY OFF and dangerous. I don't have time to wade through it all and comment on it.
Gary Slusser Quality Water Associates
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So UV will still work since bacteria longevity is hours to days right?

Thanks. Good to know this.

What strength are you talking here? It would have to be extremely strong. But even if weaker UV is potentially dangerous to skin and eye, like sunlight, don't look at it and don't expose yourself to it too long. Fasten it with the light off and shield it and go away. Nothing difficult to achieve.

"Applied correctly." I have a 1 gallon tank. I plan to tape it to the side of my drinking water tank near the top tilted slightly downward to capture as much water as possible and completely shield the light leaving enough air to cool. Any further suggestions.

Thanks for your input Gary.
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On Aug 11, 2:28 pm, snipped-for-privacy@gmail.com wrote:

Yes to 99.9999. Bacteria tend to have a much shorter life span than that.

Class A = 40 mJ/cm2

That won't work, UV lights are built to allow the water to flow through them and the light is contained inside the chamber.

You're welcome.
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Super. Thanks!!!!!!!
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I retested for high bacteria count in the bay area's drinking water very carefully this time (to the hour and perfect temperature) with a different test kit and results came out very negative .. which of course is good news for the bay area.
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Except that the main germicidal wavelngths of UV (UVC of wavelength around 240-280 nm) are highly blocked by the ozone layer even when the ozone layer is weakened, and these wavelengths also have a high rate of being blocked by plastics that are transparent when thick enough to make bottles from such plastics.
- Don Klipstein ( snipped-for-privacy@misty.com)
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Don Klipstein wrote:

The blockage may be high, but the resulting radiation is sufficient. At least according to all the studies I've been able to find.
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Just buying a UV light and be done with it. I'm lazy.
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snipped-for-privacy@gmail.com wrote:

I just hope you don't rely on germicidal effects from those "blacklights" whose UV is mainly in the longwave roughly-60% of the UVA range - which does not even cause much suntanning of human skin. (At higher intensities, such longwave UV wavelengths still have ill effects on a couple parts of the human eye and some organic pigments/dyes.)
Killing bacteria with UV depends highly on sufficient exposure to UV wavelengths that are in or very near the UVC range. The main germicidal UV wavelength from "germicidal UV lamps" is 253.7 nm, AKA 254 nm, from low pressure mercury vapor combined with an inert gas, usually argon, sometimes krypton, sometimes neon, sometimes a mixture of argon with either neon or krypton.
- Don Klipstein ( snipped-for-privacy@misty.com)
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snipped-for-privacy@gmail.com wrote:

Right. But an 80-mile long extension cord is out of the question for the little brown babies in remote regions of Kenya.
Maybe a battery-operated one?
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On Aug 10, 5:23pm, snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

What about UV lights? Do they have the desirable germicidal effect? Thanks.
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snipped-for-privacy@gmail.com wrote:

That depends on what the UV lights are. There are a few varieties of UV!
Longer wave 65% or so of UVA, 340 to 400 nm or so: This is the "blacklight range", as in the main wavelength range for dim violetish color lamps to cause organic fluorescent substances to glow.
This wavelength range has its "traditional base" being the 365-366 nm cluster of wavelengths of high pressure mercury vapor lamps. Blacklight "fluorescent lamps" (those are actually true fluorescent lamps) of BL and BLB types have a phosphor that absorbs the 254 and 185 nm main wavelengths from glowing low pressure mercury vapor to produce fluorescence in longer-wave UV around 360 nm.
There are many UV LEDs with peak wavelength around 395 nm, and fewer with shorter wavelengths but still mostly at least 350 nm. When an LED has nominal peak wavelength 350-375 nm, it tends to dimly visibly glow with a violetsh-white color - due to weak out-of-main-band spectral content combined with the visible-violet-fringe of the main UVA emission band. When a UV or "near-UV" or "nearly-UV" LED has peak wavelength in the 380 to 410 nm range, especially of 395 or 400 or 405 nm common wavelengths, such an LED is typically quite violetish in color and often not especially dim. 400 nm is the "official border" between UVA and "visible light", LEDs with peak wavelength slightly below 400 nm have their main emission bands having some significant spectral content at wavelengths above 400 nm, and "near-UV" of wavelengths only slightly shorter than 400 nm is dimly visible.
The main human health hazards from longer-UVA wavelengths are:
* To the lens of the eye (mainly impacting farm hands and long-haul truck drivers working heavily within roughly 35 degrees latitude from the equator).
* To the retina of the eye, mainly from focused intense images of strong sources of such UV such as staring into a UV LED.
Next shorter wavelength significat subdivision of UV: Tanning UVA. That is roughly 315-340 nm. Keep in mind that "tanning UVA" is not completely harmless to human skin, and can also be harsh on the retina, lens and cornea of the human eye.
Next after that is UVB - 280 to 315 nm. That is a harsher range of UV. UVB content in sunlight reaching Earth's surface is mostly 300-315 nm.
Ill effects to the human eye from shorter wavelengths of UV tend to be more concentrated to more-foreward parts of the human eye. UVB has some prospect to do bad things to the lens of the human eye, but is worst to the cornea. UVB is notably harsh on human skin and blamed for many skin cancers, especially ones of the more-malignant class of "malignant melanomas".
Next down in UV categorization by wavelength is non-vacuum portion of UVC. That is 200-280 nm. "Germicidal UV" is mainly the longwave 50-60% or so of this range, and the shortest UVB wavelengths are indeed are slightly to somewhat germicidal. The 254 / 253.7 nm wavelength from low pressure mercury vapor (combined appropriately with a "noble gas" or a mixture of "noble gases") is the main wavelength for such purpose from lamps made for such purpose.
The main human health hazards from UV wavelengths that short are to the conjunctiva and outer regions of the cornea of the eye, and to the epidermis of the skin. Carcinogenesis to human skin from UVC appears to be a significant problem from significant exposure, and appears to be likely confined to the epidermis - where the more malignant skin cancers of "malignant melanoma" type tend to originate. Just to point out an alarmist thing to watch for - there is such a thing as non-melanin-producing malignant melanoma. That is an uncommon but deadly known "subvariant" skin cancer whose critical early warning sign is otherwise-unexplained growth of a reddish area on the skin, mole-like small or almost that small in size when it is in an earlier stage when having a dermatologist removing it has a good chance of saving your life from removing such a deadly cancer at such a sufficiently early stage.
UV wavelengths in the UVC range also include the 10 to 200 nm range as well as the 200-280 nm range. The sub-200-nm wavelength range is "vacuum ultraviolet" "AKA VUV", absorbed by air and oproducing ozone in the a process. Few transparant solid materials pass significantly even a part of this wavelength range. The main wavelength of low pressure mercury vapor in this range is 184.9 AKA 185 nm.
- Don Klipstein ( snipped-for-privacy@misty.com)
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On Aug 10, 8:24pm, snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

Skin cancer is over blown. No one ever died from it. Lots of people who've spent most of their lives outdoors live to be over 100. Get out more. Furthermore I ain't gonna be sunbathing by my water tank. So skin exposure isn't even an issue, nor eye problems. I'll black it out from view if it get annoying. .. off to get me some UV.
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Dear Stevep...:
On Aug 10, 9:34pm, snipped-for-privacy@gmail.com wrote: ...

http://www.cancer.org/docroot/PED/content/ped_7_1_What_You_Need_To_Know_About_Skin_Cancer.asp
*Lots* of people have died from it. It spreads from the skin to other organs. But a reasonable (non-zero) amount of sun exposure is health and good for you.
David A. Smith
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Nope. Zero. It's a myth you've got suckered into believing. No one has died from cancerous skin! Billions of people survive from damaged skin daily. Most of us have damaged skin and cancerous skin. And it doesn't spread fast either. By itself, skin cancer is so trivial that it's meaningless.

No it doesn't. Inner organs are deep within us. It would have to traverse inches of flesh, bone, cartilige, muscel etc to reach organs which is ridiculous. Furthermore, there's no way to prove it. It's a theory of some nut of which only dummies believe. Furthermore how can anyone know mere skin caused the liver to die when odds are that the liver cancer grew at the same rate as the skin? Think.
I asked my wife, a nurse for decades and she's seen all kinds of cancer patients and even she said nope, only "a few" (a tiny %) complications. But even this just "belief" run amock because again, who can know for sure what the source of the terminating cancer was, maybe the organ itself ? ?
I also laugh when people call skin and blood organs even though the "medical society" claim so. Pretty soon they'll call hair and finger nails an organ. Is an oyster or turtle shell an organ? LoL.

Vitamin D (as in sunlight) in moderation (WAY MORE THAN ZERO) is very good for you.
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wrote:

And the proof of that is that dogs don't get sick after drinking from puddles! I sure hope nobody follows that advice, cause we aren't dogs.
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Where did he say bottled puddle water? Your logic escapes me.
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jack wrote:

Right. A Dog's digestive system relies on a different mix of chemicals than a human's. This different mix (I think it's fuming Nitric Acid), kills almost everything. That which is still active, is barfed up and the dog re-eats around the offending material.
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HeyBub wrote:

Nope, it's hydrochloric, same as in all other mammals.

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snipped-for-privacy@gmail.com wrote:

Hmmm, I installed under the sink 6 stage filtering unit. Last stage is UV light tube. According to my sister and brother(both chemists, brother works for city water demartment) The filtered water is at least 99% pure. It produces enough water per day for drinking and cooking. Best thing is it does not have chlorine smell or funny taste. Even our dog and cats drink that water.
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