UV LED for disinfection of water

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Markos

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Nov 24, 2016, 9:15:38 AM11/24/16
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Does anyone have experience with commercial products that uses UV LED
for disinfection of water for human consumption?

I found these products but I have no references about efficiency:

http://www.s-et.com/water-disinfection.pdf

http://www.aquisense.com/water-treatment

Any tip?

Thanks,
Markos

Patrik D'haeseleer

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Nov 25, 2016, 1:22:25 AM11/25/16
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Seems legit. Do keep in mind that you need very short-wave UV C light to kill bacteria, and LEDs get exorbitantly expensive in those wavelengths. These are definitely not your typical 10 cent near-UV LEDs. These could easily cost a couple hundred dollars per LED.

Patrik

Markos

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Nov 28, 2016, 7:35:11 AM11/28/16
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Hi Patrik,

I tried to know the prices in these 2 companies but until now I have had no answer.

As a cheaper alternative, I'm thinking about using the mercury vapor lamp that are used inside the bulbs used in street lighting.

As described at:
http://www.pcbheaven.com/projectpages/Hack_Hg_Lamp_to_UV_Light_/

But I think I'll have to use some system to cool the lamp which, depending on the power, dissipate too much heat.

My idea is to keep that lamp, in horizontal position, above a water reservoir with a small depth to allow UV penetration to the bottom of the reservoir.

That way I would not need to use a quartz tube to insulate the bulb from the water.

What do you think?

Thanks,
Markos

Abizar Lakdawalla

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Nov 28, 2016, 1:00:43 PM11/28/16
to diy...@googlegroups.com, Patrik D'haeseleer

Hi Markos
Check amazon etc for  fluorescent UVC germicidal lamps. They cost in the $10's range for 20 to 40W. You would still need the fluorescent drivers, either ballasts from regular fluorescent tubes or the electronics from CFLS.
Good luck
Abizar


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Patrik D'haeseleer

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Nov 28, 2016, 2:10:50 PM11/28/16
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UVC disinfection for water sterilization has been around for quite a while. In fact, you can buy anything from industrial-scale UV water sterilizers, all the way down to portable "Steripens" for backpackers.

As you discovered, one issue is how low efficiency the UVC bulbs are, which means you pay a lot in electricity cost, and you have to dissipate a lot of heat. Another important limitation is that you need to expose the bacteria to a sufficiently high dose over time to be effective. So it's much easier to expose a bottle of drinking water to constant UV light for a minute, like the Steripen does, than to slap a big LED on the side of your water mains and expect it to be effective.

If you are going to tinker with mercury vapor lamps yourself, BE VERY CAREFUL! Shortwave UVC light is as good as absent from natural sunlight, and can burn out your retinas in a matter of seconds - especially if you work with a strong point source like the 125W bulb in the link that you posted! 

(For the same reason, NEVER work at a biosafety cabinet with the sash raised while the UVC germicidal light is on! The glass sash will block most of the UVC, but you can still get a bad sunburn on your arms, or develop the equivalent of snow blindness from the UVC reflected off the stainless surfaces.)

MC Ants

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Nov 29, 2016, 7:53:15 AM11/29/16
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I used to be really into reef aquariums and now I work in municipal water. UV disinfection for aquariums and ponds have been around for around 25 years and basically consist of a UV bulb in a quartz sleeve and water being pumped into the chamber, usually in a coil fashion to maximize contact time. The industrial size treatment we use for the city are essentially the same principal, but on a ginormous scale. There are also built in wipers to clean the quartz sleeve, as any buildup that obstructs the UV will essentially inactivate the disinfection.

I currently use a UV-C CFL from Amazon to disinfect materials that can't be autoclaved. As Patrick said, it can be very dangerous. UVC + O2 = Ozone which can also be hazardous. I have some visible UV LEDs I used for another project that work well, but I haven't seen UVC LEDs for sale yet. What is your final goal? Maybe we can help with some additional ideas.

Mitchel Hansen

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Nov 29, 2016, 10:28:29 AM11/29/16
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Hey Markos,

I work for AquiSense and got a notification for this thread. We could have a conversation about efficiency of our reactor design and the LEDs we use. Keep in mind that our parent company NIkkiso, manufactures UVC LEDs and we regularly have conversations with customers about using our design or just buying a few LEDs and trying to figure out a design for their own needs. Feel free to contact us and our application engineers can talk specifics on efficiency and price of the project you're looking for. in...@aquisense.com 

Markos

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Dec 2, 2016, 9:06:43 PM12/2/16
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Dear,

Thanks for the comments and clarification.

I already have a household UV system associated with active carbon filters and polypropylene but intend to mount another system but thinking about a cheaper and affordable solution for domestic use in poor communities.

I thought LEDs UVC would be a competitive alternative with mercury vapor lamps, but it isn't yet.

The prices of commercial UV systems, where the UV lamp and quartz tube are inside a flow cell of "stainless steel" are not cheap, I mean, it's not an affordable alternative for home use in poor communities in many countries.

So I started thinking about alternative ways, cheap, efficient and easy to be assembled by adapting components already commonly used in these communities.

So I thought I'd adapt within a clay filter (http://www.ceramicastefani.com.br/ingles/filtro-stefani/filtro/12/classic-filter-) a mercury vapor lamp inside a quartz tube (closed at one end) dipped in the bottom half of filter.

This could be done by sticking the quartz tube to the top half of the filter.

The water in the bottom half would be being irradiated by UV continuously.

Would have to assemble an electric contact between the upper and the lower reservoir as a mechanism of protection by cutting electricity to
lamp and thus turning off the lamp whenever anyone tries to lift the upper part of the filter.

The clay material of the filter would be inert to UV and not liberate photodegradation products as could happen with plastic material.

I believe
that, depending on the size and power of the lamp chosen, it could cost ~30% of the price of a commercial system (with stainless steel flow cell).

But
another question is how to evaluate the minimum residence time of irradiation to ensure a efficient disinfection without expend too much energy unnecessarily.

I don't have a microbiology lab so I was wondering if would be possible to use some natural dye (eg: from vegetable) to determine the minimum irradiation accompanying the photobleaching (https://en.wikipedia.org/wiki/Photobleaching) of the dye.

That would be a simple chemical indicator to determine the minimum time of irradiation for lamps with different potencies and reservoirs of different sizes, ensuring sterilization and saving energy.

Any tip?

Thanks for the attention,
Markos
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