265nm led and 275nm led which is better for water purification?

Thread Starter

shiningfor2

Joined May 5, 2016
6
We are a water purification company, I bought both 265nm led and 275nm led from Shenzhen Shining Future LED Technology Co., Ltd.
they seems have same function.
now I need to choose buy which in bulk, any people can give me some suggests? much thanks
 

Alec_t

Joined Sep 17, 2013
10,616
According to Wikipedia "Particularly at wavelengths around 250 nm–260 nm,[7] UV breaks molecular bonds within microorganismal DNA, producing thymine dimers that can kill or disable the organisms."
Based on that, I would guess (I'm no expert in the field) that the shorter wavelength (265nm) would be more effective.
 

jpanhalt

Joined Jan 18, 2008
8,351
hello,
What does 265nm mean here??
It is just a shorter version of 275nm.

As for the TS, I suspect the science of water purification will answer your question. In the days of using low-pressure mercury lamps, we used 254 nm.

@Alec_t All things being equal, I agree. However, there are likely matrix effects. For example, if the contaminated water contains soluble compounds that absorb at 254 nm (the old standard) but not so much at 275 nm, the latter might be more effective at sterilization. However, those wavelenths are so close, I suspect differential absorption is not a big factor. Then, you have to consider the possible effect of photosensitizers in the water (also probably unlikely) that might change the optimal wavelength.

Since public safety is at issue, it seems to me to be a situation that has an empirical answer, rather than simply a theoretical one.

John
 
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hp1729

Joined Nov 23, 2015
2,304
We are a water purification company, I bought both 265nm led and 275nm led from Shenzhen Shining Future LED Technology Co., Ltd.
they seems have same function.
now I need to choose buy which in bulk, any people can give me some suggests? much thanks
The 265 nm part says + or - 3 nm so it is a pretty narrow coverage. How much water can a small LED disinfect?
What kind of power did the mercury vapor lamps put out? Equal to how many LEDs?
 

Thread Starter

shiningfor2

Joined May 5, 2016
6
According to Wikipedia "Particularly at wavelengths around 250 nm–260 nm,[7] UV breaks molecular bonds within microorganismal DNA, producing thymine dimers that can kill or disable the organisms."
Based on that, I would guess (I'm no expert in the field) that the shorter wavelength (265nm) would be more effective.
yes, much appreciated.
265nm is a bit expensive than 275nm, so we consider 275nm more worth it's value.
 

Thread Starter

shiningfor2

Joined May 5, 2016
6
It is just a shorter version of 275nm.

As for the TS, I suspect the science of water purification will answer your question. In the days of using low-pressure mercury lamps, we used 254 nm.

@Alec_t All things being equal, I agree. However, there are likely matrix effects. For example, if the contaminated water contains soluble compounds that absorb at 254 nm (the old standard) but not so much at 275 nm, the latter might be more effective at sterilization. However, those wavelenths are so close, I suspect differential absorption is not a big factor. Then, you have to consider the possible effect of photosensitizers in the water (also probably unlikely) that might change the optimal wavelength.

Since public safety is at issue, it seems to me to be a situation that has an empirical answer, rather than simply a theoretical one.

John
hi John, you mean 254nm is better at absorb soluble compounds, but 275nm not?
and the function also decided by photosensitizers?
before we also use 254nm mercury lamp.
 

Thread Starter

shiningfor2

Joined May 5, 2016
6
The 265 nm part says + or - 3 nm so it is a pretty narrow coverage. How much water can a small LED disinfect?
What kind of power did the mercury vapor lamps put out? Equal to how many LEDs?
this is hard to say, distance decide it's power effect, so does the mercury lamp.
but life time of mercury lamp is so short, it's a trend that 265nm 275nm led or similar led will instead of mercury lamp.
 

jpanhalt

Joined Jan 18, 2008
8,351
hi John, you mean 254nm is better at absorb soluble compounds, but 275nm not?
and the function also decided by photosensitizers?
before we also use 254nm mercury lamp.
Generally speaking, the shorter the wavelength of UVC, the more is absorbed. "Cut-off" is used to describe that effect for various solvents used in spectroscopy. I have not studied environmental water and can't say what sort of cut-off it may have in the UV; however, it should not take very much dissolved iron (to mention just one common solute) to reduce the UV transparency .

A "photosensitizer" can be viewed as a photo-activated catalyst for photochemical reactions. They can help facilitate reactions that would not normally occur.

Microbiocidal activity of UV is not a simple subject, and there are statements in the literature to the effect that UV wavelengths longer than 254 nm are more effective than 254 nm is itself. Remember, 254 nm was used originally mainly because there was a convenient source for light of that wavelength, and it was effective. It is not necessarily optimal.

As I said, your question touches on a matter of public health, and I would advise doing a thorough search of scholarly studies on the question rather than go by opinions. There may also be governmental regulations with which you will need to comply.

John
 

hp1729

Joined Nov 23, 2015
2,304
Generally speaking, the shorter the wavelength of UVC, the more is absorbed. "Cut-off" is used to describe that effect for various solvents used in spectroscopy. I have not studied environmental water and can't say what sort of cut-off it may have in the UV; however, it should not take very much dissolved iron (to mention just one common solute) to reduce the UV transparency .

A "photosensitizer" can be viewed as a photo-activated catalyst for photochemical reactions. They can help facilitate reactions that would not normally occur.

Microbiocidal activity of UV is not a simple subject, and there are statements in the literature to the effect that UV wavelengths longer than 254 nm are more effective than 254 nm is itself. Remember, 254 nm was used originally mainly because there was a convenient source for light of that wavelength, and it was effective. It is not necessarily optimal.

As I said, your question touches on a matter of public health, and I would advise doing a thorough search of scholarly studies on the question rather than go by opinions. There may also be governmental regulations with which you will need to comply.

John
Do you have a way of testing the effectiveness of the LEDs?
 

hp1729

Joined Nov 23, 2015
2,304
We are a water purification company, I bought both 265nm led and 275nm led from Shenzhen Shining Future LED Technology Co., Ltd.
they seems have same function.
now I need to choose buy which in bulk, any people can give me some suggests? much thanks
http://www.steripen.com/Aqua
There are other LED UV devices on the market but technical info is really slim.
Suggested is 18,000 microwatts per square cm, or some such thing. How do the LEDs you are considering compare?
I guess wattage depends on how much water you plan on doing at one time. The Steripen thing certainly does not look like it puts out more than 500 microwatts or so. Technical info is lacking. It is designed to do a half liter drinking bottle???
It doesn't look like something I could trust.
Maybe following a 1 micron filter and 10 times the wattage?

What might sound trustable ... pour the bottle through a 1 micron silver filter then a canister with maybe 20 to 40 such LEDs in it.
 
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hp1729

Joined Nov 23, 2015
2,304
I actually bought some 265nm, 275nm,310nm, 365nm led from Shenzhen Shining Future company and it's still working pretty nice.
The question is about effectiveness before it is about cost. Does it work? How much power is required?
If you work in a water purification business I would assume you have a way of testing these things.
 

GopherT

Joined Nov 23, 2012
8,012
The question is about effectiveness before it is about cost. Does it work? How much power is required?
If you work in a water purification business I would assume you have a way of testing these things.
No, sometimes it is just marketing, "this water has been treated with UV"
 

GopherT

Joined Nov 23, 2012
8,012
So the company doesn't really care if it is effective?

It is super popular to have UV lights and clear pipes under kitchen sinks in Japan. The pipes are plastic and the residence time is extremely short so most of the UV is absorbed by the pipe before it hits bacteria and the flux required to kill a reasonable percentage of bacteria is not possible to achieve - but people still have them installed as soon as they can afford them.
 
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