UV LED used to purify water

[beezaur]

"Are there any inherent weaknesses to using a Pasteurization proccess in place of boiling to make emergency drinking water? . . ."

Sub_Umbra,

I don't think so. If I were recommending a process to the lay person who was freshly freaked out over a boil water order or disaster, I would not choose pasteurization for the reason you mention: people not getting the process right. But if you know what you are doing, I don't know why it would be unreliable.

I did a little reading about the MIOX/MSR mixed oxidant device. They claim it produces several types of chlorine, hydrogen peroxide, and ozone. Hydrogen peroxide destroys ozone, which is already pretty volatile. Ozone is pretty effective though, on the order of 10x as "powerful" as the baddest version of chlorine. Ozone is also used a lot to kill odors in surface water treatment facilities. A plant near my home makes summertime river water taste like well water with ozone (then they chlorinate it). Add to this the persistant residuals from the various flavors of chlorine, and you have an ideal device for the military. If you have reasonably clear water, and can only use one device, this deserves consideration.

I still favor filtration/UV disinfection as the ideal. That makes for really good tasting water when you are in the mountains, etc., and there are no harmful byproducts.

 

[2dim]

Somehow, in spite of all, something tells me I'll still have lingering regrets after visiting India again...my friend has parasite lumps surfacing under his skin, ten years later...yuch!!!

 

[cy]

so crypto cysts are not killed during the one minute cycle of http://uvaquastar.com/info_pages.php/pages_id/31

was led to believe it killed all micro-cooties with the 60 second dose.

tested the UVaquastar last week at Horsethief Springs near Telihina Oklahoma. drank the water with no problems.

 

[beezaur]

"so crypto cysts are not killed during the one minute cycle . . ."

I suspect they are not reliably inactivated.

Many times the studies promoted by treatment vendors are based on water that has already been settled (removes sand/silt), flocculated (turns unsettlable colloids into "snowflakes"), and clarified (allows the snowflakes to settle), or filtered, before the treatment in question is performed. This is representative of treatment in public water systems, but it is a far cry from dipping your bottle in the stream or lake and hitting the button.

There are all kinds of issues with dissolved and suspended things in the water, pH, temperature, etc. that can screw up either UV disinfection or chemical oxidation in the context of treating water that you have dipped from an untested source.

The best way to get around all this uncertainty is to filter the water before disinfecting it. The next best way is to disinvect the snot out of it with a really high dose. The problem with high UV doses is that it still might not work (particle shielding and low penetration to UV wavelengths). The problem with high chemical doses is byproducts and bad taste.

If you have a sub-micron filter, it will take out the resistant bugs, leaving only chemical and viral contaminants.

Scott

 

[cy]

beezaur, many thanks for your feedback. sure glad I've got this infomation. for I though it was perfectly safe to dip from a stream. run thru two cycles for safety and drink.

so the best strategy is filter first, then UV. if you are backpacking, weight is at a premium. to carry two systems adds mass.

 

[2dim]

[ QUOTE ]
If you have a sub-micron filter, it will take out the resistant bugs, leaving only chemical and viral contaminants.

[/ QUOTE ]

Good advice! So what's the smallest lightest combo most convenient combo for short to medium term trips? BTW, I've been producing any consuming apparently high quality coloidal siver water lately...anyone have experience with it as a purifier, preventative or cure-all for waterborne nasties and more? Can make different strengths, and gold also...

 

[Sub_Umbra]

I think that the Katadyn ceramic filters have silver in them.

 

[beezaur]

I should put a disclaimer on myself that design public drinking water systems is by necessity extremely conservative.

I just read in the latest edition of the American Water Works Association's journal of a case where over 200 women had tried to sue the city for their miscarriages. They were blaming the water utility's disinfection process. I have no idea about the technical aspects of the case, but it underscores the magnitude of problems from bad drinking water in public systems. You'd get way more than fired for causing that.

2dim,

Some people have turned themselves permenantly blue injesting colloidal silver.

Sub_Umbra is right about at least some of the Katadyn filters. Silver is also used in some high-end architectural finishes to prevent germs on handrails, in kitchens, stuff like that.

I think in the case of filters it is used to prevent bacterial growth and the associated problems (clogging, breakthrough). You can occasionally run chlorinated water through to get a lot of the same effect.

Scott

 

[2dim]

[ QUOTE ]
2dim,

Some people have turned themselves permenantly blue injesting colloidal silver.

[/ QUOTE ]

Thanks, but newer technology supposedly creates far smaller particle size, almost nano. The water stays clear during the process and afterwords, which is some indication and different from the old basic unit, essentially batteries and silver rods. Stopped using mine years ago... Lot's of interesting info on the web concerning health benefits. Some say adding silver coloid to water will purify it...that's what I'm questioning here. Although it's used in swimming pools and larger agricultural applications, I'm not so confident about immediate purification of drinking water, though it has kept my milk products fresh a lot longer. Surface disinfecting is OK, but not with the instant effect of something like bleach. Maybe good for soaking toothbrushes? Anyway, those I've given it to --mostly for colds/flu -- apparently had very quick results, like complete cures in one or two days.

 

[chanik]

A little late to this thread, but hey:

Crypto is very chemical tolerant so the MSR and drops have a long wait just to ensure crypto gets killed, but Crypto and Giardia are very sensitve to UV even encysted. Viruses are the challenge for UV systems. There is much confusion about this Oocyst thing since it was not thought so based on excystation. Subsequent tissue infectivity studies show that even at a low 10mJ, there is over 99.99% reduction. So the bugs can still swim, but they're sterile is the upshot. This epa chart summarizes the data:
http://www.epa.gov/nerl/news/forum2003/water/ware_poster.pdf

As for LEDs, the efficiency is very low compared to low pressure tubes. Remember, fluorescent lighting is still much better than LEDs for both efficiency and cost per lumens (70Lm/W is typical). And a 30W bulb is a couple bucks. What would 2100Lm worth of Luxeons cost? But it's not small and you can't focus a big diffuse, glowing gas column.

 

[cy]

chanik, many thanks for weighting in. was getting concerned about my uvaquastar being safe to use after two cycles. cyclo cysts concerts of course.

I've only done one live test. water tasted pretty funny, but I didn't get sick. I'm taking along a gold coffee filter next time to get rid of the floaties.

how current is the EPA chart? it indicated that data presented was the only set of data available for live testing VS test tube testing for cyspor cysts.

How many UVaquastars are out in the field? are these the beta units that we purchased?

 

[chanik]

We keep changing the thing in small ways, but we have about 800 out there now and another 1K backlog. Our next version with beter threads and tube holder will be out in May. The EPA chart is very current. We have more stuff in our Links section, but basically, in the last 5 years or so people have realized that UV is very effective against encysted protists. Uof Arizona, CDC and other labs have demonstrated Log4 reduction at doses as low as 3mJ for Giradia and Crypto oocycts.

Cheers

 

[beezaur]

Thanks for the info, chanik.

I wonder what was behind the study I quoted from my treatment chem book. They used 15 mW/s on Cryptosporidium parvum, and did not get good results until ~150 min.

I know some researchers have reported thresholds for some disinfectants against some organisms. Is there a "magic number" to stay above for raw surface water treatment?

The same reference (Faust & Aly, Chemistry of Water Treatment, 2nd Ed.) also gives lethal doses for inactivation of Polio and other viruses less than 1 mW-s/cm^2. I did not read the research report, so I don't know the details of that work. I assume turbidity is causing the difficulty you note.

Do you have links or info for the U of A and CDC work?

Scott

 

[cy]

Chanik, many thanks for the info. good to know there is good solid science and backed by a healthy number units in the field.

based upon this info, I'm planning on carring only the uvaquastar with a permenant gold mesh coffee filter. sure hope I can find a smaller one, then std coffee maker size.

don't think paper coffee filters will go very far. it's not fun to drink treated water with floaties in it.

 

[chanik]

Use the paper. They fold better than the gold filters and a box of 40 can be had from any grocery store for a buck or two. Plus they're emergency fire starter or toilet paper.

The cyrpto can still excystate and swim around at 150mJ, it just can't infect. That's the deal with radiation; first they go sterile, all the little cilia hairs fall out (humor), then they die. There are two numbers commonly spec'd in EPA and WQA and ANSI-55 class A for unsafe water which is 40mJ and class B for questionable tap water sorts of stuff: 16.2mJ The target is to better than 99.99% for every common pathogen you might be drinking. Polio is one of the toughest and takes more than 1mJ.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=241729

 

[cy]

ok, paper filters it is. planning on a 12 day trek this summer. every oz I can leave behind the better.

 

[KevinL]

chanik, thanks for the info, it is appreciated and helps give us extra confidence in the product. /ubbthreads/images/graemlins/smile.gif

Congratulations on getting things up and running, sounds like you've got a lot of customers queueing up for one.

 

[03lab]

Wow, great thread! Lots of useful information here. /ubbthreads/images/graemlins/thumbsup.gif