Dose vs dwell time of Chlorine Dioxide (AquaMira, KearWater, etc)

[Elliott Wolin]

Chlorine dioxide manufacturers state that the product can be used at less than full strength if a longer dwell time is used. They usually specify an inverse relationship, half-dose for double the time, etc.

Anyone know the limits to this? Is this true just for AquaMira, or for all Cl02 products (pills, KlearWater, etc)?

I've used about 1/3 full dose when the water will sit overnight. Following the inverse rule in principle I could have used 1/16 dose for an 8-hour dwell time. I'm reluctant to go this far.

Possible mechanisms to set limits to the inverse relationship (n.b. I know little about how the product actually works, except that the highly-polar oxygen disrupts something in the nasties):

1) Product gets used up. Need minimum amount per volume of water.

2) Product deteriorates. You have enough product, but it loses its effectiveness before enough dwell time has elapsed.

3) Product escapes. Enough time, enough product, but it evaporates away or diffuses out of the container before the job is done.

4) Product separates. Like oil and water, eventually the product separates out before it does its work. Possibly remixing periodically would help.

5) Things I haven't thought of…

[EndoftheTrail]

Anyone know the limits to this? Is this true just for AquaMira, or for all Cl02 products (pills, KlearWater, etc)?

The above is true for Aqua Mira, KlearWater, Micropur and other chlorine dioxide products. The active ingredient is the same in all cases.

I've used about 1/3 full dose when the water will sit overnight. Following the inverse rule in principle I could have used 1/16 dose for an 8-hour dwell time. I'm reluctant to go this far.

Not an expert, but I wouldn't get too scientific about this. Methinks you would need some minimum dosage… in other words, 1/2 the dosage and double the time works… but would 1/16th dosage really kill everything — even with 16 times treatment duration??? Another factor to consider is that once the oxidation finishes, any further "sitting around time" will probably be useless.

1) Product gets used up. Need minimum amount per volume of water. 2) Product deteriorates. You have enough product, but it loses its effectiveness before enough dwell time has elapsed. 3) Product escapes. Enough time, enough product, but it evaporates away or diffuses out of the container before the job is done. 4) Product separates. Like oil and water, eventually the product separates out before it does its work. Possibly remixing periodically would help.

Methinks this is where pre-trip inspection comes in — as with all other gear pieces. Make sure the chemicals are still in good order, that you have sufficient quantity on hand, and that the container(s) are tightened up. Klearwater aside, I don't think you should be pre-mixing chemicals in advance.

5) Things I haven't thought of…

Yes, definitely. Once you use up your current batch of chemicals, switch to Micropur! A lot lighter than liquids, no worries about leakage or spillage, and no fussing with counting drops, pre-mixing or wasting time waiting for pre-mixing to finish. Just drop one tablet per liter or quart — it's also easy to break a tablet in half when needed.

Micropur has a higher concentration of chlorine dioxide — which allows it to label its effectiveness against bacteria, protozoa (crypto) and viruses! Normal treatment time is same as the others — 15-20 minutes — but up to 4 hours for water that's just above freezing. But if you read your Aqua Mira label, it mentions ONLY bacteria! Per another poster who talked with A.M. — their liquid solution is weaker but should still be effective against viruses and protozoa if given a longer treatment time — but they are not allowed to advertise or label about these two classes of baddies.

[Elliott Wolin]

Ben,

A few clarifications/comments:

The list of mechanisms in my post are mechanisms that might affect the dose/time relationship AFTER the product has been added to the water to be treated. I am talking about what happens IN the water to be treated while the product is in it. I assume use of a fresh product and that all manufacturers rules are followed (e.g. no pre-mixing of AquaMira at home!).

E.g. the product might naturally deteriorate in use in water, it might separate out, evaporate, etc.

As for MicroPur, I carry some for emergencies, but it is a bit too expensive for my tastes when there is a large group out for a week or two. At BPL it costs about 40 cents/liter at full strength, compared to about 10 cents per liter for AquaMira. On one of our big trips we may have used as much as 4 liters/day/person times 5 people times 14 days, totalling 280 liters. At full strength AquaMira costs $28, whereas MicroPur costs over $100. We treated lots of water at 1/2-1/3 strength overnight, so we used up about one AquaMira kit, or about $12 worth.

Later…just noticed that AquaMira now comes in 2 oz bottles for not much more than the 1 oz bottle. On their web site the double-sized version costs only $2 more than the standard size! This is almost half the cost! And they say it has a 4-year shelf life.

[EndoftheTrail]

Given that one Micropur tablet has about four times the strength of a standard A.M. mixed dosage — for the same overnight treatment time, you can easily break one tablet into fourths — and treat the same water for approx. $25 instead of $100. Not only is Micropur now cheaper, you can dispense with the tedious counting of droplets and mixture waiting time! Just split the tablets, drop them in, and you're done.

[Elliott Wolin]

Hi Ben,

I understand you are saying that one Micropur tablet supplies four times the concentration of the standard 7+7 drops of AquaMira in one liter of water. If so, then one tablet of Micropur is equivalent to 28+28 drops of A-M. And if the A-M instructions are correct, then one tablet of Micropur should treat 4 liters of water in under 30 mins.

Wow…if so then Micropur is the way to go, hands down.

But why are the dose recommendations so different for A-M and Micropur? Micropur instructions say to use 1 tablet per liter in clear 20 degrees C water and wait 30 mins.

[EndoftheTrail]

Hi Elliot:

The difference in concentration was posted by another poster (forgot his name) when we were having a similar forum exchange between Micropur vs. AM. He was an AM user and decided to call AM directly and find out. He then posted the 4X concentration difference. He also mentioned that unlike Micropur, AM was prohibited from mentioning viruses or protozoa.

My Micropur instructions only states "4 hours". Period. However, it also mentions effectiveness against not only bacteria, but also viruses and protozoa. In contrast, AM states 20 minutes — but mentions only bacteria! This could perhaps explain the supposed dosage difference.

Another reason (and I am only guessing here) could be a difference in style between a Swiss versus an American company. Maybe it is the Swiss style to simply mention the longest treatment time (i.e. 4 hours for water just above freezing) — rather than printing out a short treatment time that would work only in 'ideal' water temperature — and then burying the 4 hours somewhere in the fine print — as many American companies would do.

I didn't talk to AM but I did talk to a Micropur rep. who confirmed to me that 20 minutes is more than good enough — unless the water is near freezing. If you are interested in switching to Micropur, I recommend that you confirm with them about using 1/4th dosage for overnight water treatment — just to be sure.

[Kenneth Reppart]

I've been wondering the same thing so if someone can confirm with Micropur about the reduced dosing that'd be great! I dont know if I want to get into splitting tablets but just confirming that I could drop a tablet into a 2L platypus and wait 40-60 minutes would be great info.

[Roger B]

This is the old thread that discussed the variation in doses Micropur doses

hope this helps the discussion

[EndoftheTrail]

Elliot and Ken:

I've read from different sources that one can safely half the dosage by doubling treatment time. However, I don't know specifically about using just a quarter dosage.

Since I mentioned it (I think it will work) — I figure I will email the question to Katahdyn for a more authoritative answer. I will post when I hear back from them.

[Elliott Wolin]

Hi all,

Just called AquaMira. Some notes:

– they claim ALL ClO2 tablets are made by the SAME manufacturer (not sure if he meant in the US, or licensed for sale in the US, or worldwide). All that's different is packaging and labeling.

– tablets release 4 ppm ClO2 in one liter of water

– drops release 2 ppm ClO2 in one liter of water

– he wouldn't elaborate on why 4 ppm is needed in one case and 2 ppm in another, something about EPA regulations and how you market it (disinfectant vs purifier vs …)

– drops and tablets have the same active product

– tablets dissolve and begin to release ClO2 in less than 20 secs (may have misunderstood this…do they dissolve so rapidly?)

– tablets may have a different ClO2 release profile vs time than drops

– ClO2 is a dissolved GAS in the water, so it can evaporate away

– even if the container is sealed (best practice), the gas may diffuse out through the container walls (I wonder if it will diffuse through Platypus container walls)

– they will not comment on dose/dwell-time as they have to follow EPA guidelines exactly as far as recommendations are concerned

– they did state that the dose/dwell-time relationship is NOT linear, but wouldn't say where it cuts off

This leads me back to my original gut feeling, not to push this too far. I'll probably stick with 1/2 dose for twice as long, perhaps 1/3 dose for overnight. It would be nice to know if Platypus containers are permeable to CLO2.

Also, it seems possible that since tablets release twice the dose, and they are marketed differently from drops (which may explain the different dose recommendations), the dose can be halved for clear not-too-cold water with the same dwell time in some cases. It's up to you whether you want to do this, though.

Any further information from other manufacturers would be appreciated.

Finally, the A-M web site has a gigantic EPA document/report on ClO2 that may answer many questions. I hope to have a look.

[George Matthews]

What I tend to always think about when I used to pump filter water and now when I mix AquaMira is:

Is this good or bad water?

If 10% of water is bad, but we treat 90% of the time
[a scientific wild a$$ guess]

Probabilities
======TREAT====NO TREAT
GOOD== .81 ==== .09
BAD=== .09 ==== .01

I, for one, do not want to risk drinking untreated bad water (especially when backpacking with family or friends) so I will continue to use the drops and will try the tablets this year (thanks Ben).

Another thought: for a group – instead of treating water overnight, boil water using a wood burner like Bushbuddy to reduce cost.

Elliott – I like your question. I'd like to see the BPL staff treat known bad water with continuing 1/2 doses with double dwell times to see what actually works. Of course, after about 16 hours it becomes irrelevant to light backpacking, but I'd still like to know.

Another question: if you break down water to its molecules and go further to its atoms and keep going to its particles – now think about all that space between these things. Isn't water really more nothing than something? : )

[Elliott Wolin]

Unfortunately I understand it is very difficult to test for the presence of Giardia cysts, which may be why information is sometimes contradictory. The base information may be the same, but people use different safety factors, etc.

[EndoftheTrail]

Elliott:

I just heard back from Katadyn. They advise against breaking up a tablet and prolonging treatment time in order to treat greater quantities of water. I think this is consistent with their very conservative way of communicating and labeling. Still, it's what they say and I would recommend following it.

Reading your post and thinking about it… since Micropur provides twice the PPM than A.M. — if you choose to continue with your technique of splitting up dosage, then I think that's all the more reason for choosing Micropur — both for its increased concentration and for its greater ease of use…

[Elliott Wolin]

It's odd, but all the EPA and Army stuff I've been reading are in favor of smaller doses and longer contact times, even explicitely recommending it. So I don't understand why manufacturers recommend against it.

You must use a closed container that is impermeable to diffusion of ClO2 through the walls, and can't have too much organic junk in the water, though.

I am looking into this further and hope to have a lot to say in the future, after I collect a bunch more information. I'm hoping to make some sense out of the conflicting information.

[EndoftheTrail]

I have two guesses:

1. Manufacturers have no incentive to encourage / publicize decreasing dosage by increasing treatment time. Remember the old shampoo directions that tell people to wash and rinse twice? Whatever it takes to encourage usage.

2. CYA. No manufacturer will get into trouble by recommending a higher than absolutely necessary dosage — so long as the higher-than-really-necessary dosage is within safe limits.

To me, be it liquid drops or solid tablets… at the end of the day, the thing that matters is the actual PPM that makes it into the water. Micropur acts similar to alka seltzer — the tablet immediately begins to bubble away as soon as it comes into contact with water — and dissolves pretty quickly. All dissolved, the PPM "delivery" is just as effective as the liquid A.M.

I think the same rep. would probably tell you not to tinker with A.M dosage either — and giving you a big spew about how the dosage is scientifically calibered to water volume and so on and so forth. But between you and me, I would have absolutely no problems with halving the dosage of either in order to treat twice the water. Unlike you, I don't think I would go so far as cutting dosage to 1/4th to treat four times the water — even if it might still work just fine. But wherever I draw the line, if I am reluctant to do that with Micropur, I would be even more reluctant doing so with the weaker A.M.

[Joe Pickering]

Folks,

I'm traveling to China on 22 Feb for 2 weeks and am worried about the water over there. I plan on using AM drops (7+7 per liter) with a contact time of 2 hours and a MSR Miniworks EX 0.2 micron ceramic filter.

I'll be filtering tap water and bottled water (apparently they are counterfeiting bottled water) exclusively. I will use the MSR filter on camping/backpacking trips with the Boy Scouts as well, so the investment isn’t just for China.

I have two questions:
1) Will the AM drops (7+7 per liter, contact time 2 hours) kill the potential baddies in the water?
2) Should I increase the contact time to 4 hours or more or switch to the Micropur tablets?
3) Is the MSR filter going to add additional protection?

Thank you,
Joe

[EndoftheTrail]

Where in China are you going? Also, are you staying in urban areas or heading out to remote villages or wilderness?

For urban areas, you are NOT going to need a filter or AM or anything else. Water from major hotels is safe — you can either drink the boiled water provided — or buy bottled water which is available everywhere. Tap water is OK for brushing and washing. Buy your bottled water at large to medium size stores and you WON'T have to worry about quality. Check the seals if that helps put you at ease. Just don't buy the stuff from some scruffy-looking kid off the sidewalk — it's not that hard to refill and pop a seal back on.

For multi-day hikes out in the wilds, then yes, you should treat your water. I highly recommend that you invest in a First Need purifier (available at REI and many other places) — as this pump is lighter, faster, and more effective than the MSR Miniworks EX. Unlike MSR, First Need will protect you against viruses as well — so no need for chlorine dioxide treatment at all.

Finally, for treating large quantity of water, you can use the First Need as a gravity purifier. If you are still nervous about urban water, you can rig the unit to purify water effortlessly at night — and have safe water available each morning.

[Elliott Wolin]

Hard to say about ClO2 contact time and dose in China.

Instructions for ClO2 usage are based on US EPA guidelines, the kinds and concentrations of pathogens found in the US, etc. Tap water in China I understand is clear but not potable. Most, if not all, people boil or buy water there, and I've heard that little teacup sized heating elements are all over. Also, some hotels have built-in water purification, at least I've heard that the best ones do.

The EPA guidelines are based on a trying to attain a pathogen reduction factor appropriate for US surface water. This reduction factor may not be enough in China.

Possibly a hybrid approach would work: use the filter to eliminate the big stuff (protozoa, bacteria) and use ClO2 for the viruses. ClO2 is very effective on viruses, much less so on protozoa (esp. on crytosporidium).

In particular, EPA research shows a factor of 10,000 (4-log) reduction in typical US viruses with a CT (concentration times dwell time) of 17 mg-min/l for 15 degree C (cool) clear water. A-M supposedly supplies 2 mg/l at 7+7 drops, so a CT of 17 is reached after only 8.5 minutes. Log-4 reduction is considered adequate in the US for viruses. And tablets supposedly give 4 mg/l so the same CT is reached in 4.25 minutes. This includes a safety factor to account for varying pH.

But who knows if 4-log reduction for viruses is enough in China (higher concentration of viruses in Chinese water compared to US surface water?), nor if ClO2 works as well on typical Chinese viruses as on US viruses (I suspect it does).

Of course zillions of US tourists visit China, and I haven't heard of massive giardia attacks. They must find good water somewhere…

[Joe Pickering]

Thank you, Ben and Elliott.

I'll be in Taipei (technically Taiwan), Shanghai, and Beijing. No wilderness excursions planned.

This is part of an EMBA course requirement. The professor who manages the trip and travels with us has indicated that people have gotten sick on previous trips by drinking the municipal water supply and/or bottled water (of course this is a subjective observation). Counterfeiting water is relatively easy in China, even in shops.

The water supply in these areas is poor (think late 1800s, early 1900s in the US).

This is the first trip in years when the program will be in western hotels, except for Beijing. So I expect little difficulty with both methods when using a muni or bottled water supply, but being new to this I wanted to check.

Most travelers are dosed with antibiotics and vaccinations (I had to have 6 or 8). They also carry anti-diarrheal meds with them so there would be few issues.

My primary concerns are sickness while I’m over there (poor medical care), avoiding downtime due to illness, and longer-term effects due to chemicals and other stuff in the water (in addition to viruses and bacteria). So, I'm am looking to be reasonably safe rather than sorry.

joe

[EndoftheTrail]

Joe:

Knowing this is an EMBA program in metropolitan areas, you'll have even less to worry about.

If this is your first time in China, be prepared to be amazed at how modern things are over there (not so true in tertiary-level provincial towns but definitely in all major and secondary cities). You may well be surprised at how "open" everything is. All the times I went through Hongqiao and Pudong airports, I have yet to see Chinese customs opening visitors' bags! 98% of the time, you are as free or freer than here in the US. In Shanghai, you will see thousands of western expats working. And no, they don't carry filters or A.M. with them. Not after the second day anyway.

BUT — dare you veer into the remaining 2% realm of taboo — like trying to pass out bibles in the streets or start your own political party… then suddenly, it'll be like Mao or Stalin all over again!

You'll have totally normal-like internet and blog access 98% of the time — but try to access BBC.com or CNN.com — and suddenly you are blocked!

It's normal and abnormal at the same time. Totally schizo. You'll have a blast!

[EndoftheTrail]

Joe:

Continuing on my tangent…

When in Taipei and Shanghai, be sure to head to the subways and observe the amazing difference in crowd behavior between these two Chinese cities! Watch how folks in Taipei use the escalators there — then compare with the denizens of Shanghai.

[Joe Pickering]

Thank you, Ben. I appreciate your insight.

I will be paying close attention as China is one of the three developing areas of the world I am most interested in. I was hoping to learn a little more Chinese that I currently know, but I do have a 23 hour plane trip ahead of me (PHL – SanFran – Taipei, Taipei – HK – Shanghai, Shaghai – Beijing, Beijing – Chicago – PHL)!

joe

[EndoftheTrail]

Joe:

Are you just stopping over in TPE and HKG on your way to Shanghai — or actually spending time in all these places? Anyway, have tons of fun — and be sure to report back your observations! :)

[Joe Pickering]

Ben,

I'll be in TPE for 4-5 days and HKG for just a few hours. Shanghai is another 4-5 days, Beijing is 2-3 days.

I'll make sure to post back.

Thank you to everyone for all the assistance!

joe

[Stumphges]

Hey Joe,

I live in Shanghai and I would suggest leaving your equipment at home. The bottled water is fine, just buy the Nestle or Watson's stuff – it's all distilled. You're not really going to be in China anyway. "There's Shanghai, and then there's China" as they say.

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