The Safe-Water-Challenge – which filtering design can you reliably maintain around the globe?

^^^

You can distill water faster than 6 hours per gallon.

Distillation is great. But how without using fuel, or while sleeping? Replenishing fuel may be a problem in many areas, and would force one quickly beyond the weight-constrain. Great backup-option though, if there is plenty of wood to burn.

Solar still. It runs on bright sunlight.

–B.G.–

Would love to see some solar-still designs that you have tested on the trail.
Distillation sounds like a great idea, although I have not yet have had experience with it for serious amounts of water. Has anyone here?

Sawyer squeeze or the inline gravity version? can use 2L soda bottle for durable, cheap "dirty" side or Evernew bottles if you want more compact. no moving parts, maintenance is using the included syringe to backflush it once in a while. 4 liters would take less than a half hour including filling up the dirty side with 2x2L bottles

if you are worried about viruses then you can boil it.

I am trying to understand your design challenge. I have a couple questions:

1) What are you trying to filter/purify? Bacteria? Viruses? Chemical contamination?

2) Are you saying every component of the system has to be able to be sourced around the globe? I am not sure anything can be sourced around the globe that could be reliably trusted to filter even bacteria. How could you trust an item you purchase in a third world country with the required fidelity/precision.

Jake D:
thanks for the suggestion. Gravity filtration is a good option I think. Proprietary micron-screens are hard to replace on the go, so I'd say the Sawyer-product is not qualifying, as it can break down without giving the user the ability to replace the filter itself.

The 2L soda-bottles as the "dirty side" I do like. Another option I was contemplating (not yet tested) was to use a 10L (2.5 gallons) solar-shower-bag, as it has the ability to fetch plenty of water, it takes up almost no space, is lightweight, has a hose-adapter and a valve to adjust the filtration-speed (gives the charcoal more time to do it's job on the water – opposed to the water that rushes by). The solar-shower-function would merely be a side-benefit. (fetching and hanging up water is a nice excuse for having a luxury-item like the solar-shower :) )

Ben,
thanks for your questions.

Question 1) "What are you trying to filter/purify? Bacteria? Viruses? Chemical contamination?"

yes, originally I had a fourth design-criterion in it (but I took it out because I thought it would get too complicated). But you are right, I am not only worried about micro-organisms, but also about chemical contamination. which is completely neglected with most filtration-systems. Generally, this criterion is "kind-of" implied when speaking about "water-filtration", which means that it makes water safe to drink. I do not subscribe to the theory that a little bit of chemical contamination is harmless, but obviously it is difficult to set a high standard in this regards, unless one is using reverse osmosis or distillation. Because chemical contamination can be quite hazardous in industrial areas, even if it is "diluted", I'd say the filtration system should protect one from chemical contamination, and not merely from the (viral, bacterial, fungal) pathogens.

To make it specific enough for this challenge, lets put the fourth criterion back in (also added into opening post):
Criterion 4) Filtration. The system integrates all of these three steps:
a) pre-filtering to get the dirt particles out,
b) pathogen filtering and
c) chemicals filtering (oil, heavy metals, radioactive isotopes, poisons etc.).
since it is difficult to set a quantitative standard for c), let's simply say it has to have at least one way of chemical purification.

Question 2) "Are you saying every component of the system has to be able to be sourced around the globe? I am not sure anything can be sourced around the globe that could be reliably trusted to filter even bacteria. How could you trust an item you purchase in a third world country with the required fidelity/precision."

Almost. What I mean is that those parts that are likely to break down and that can not be repaired would render the user helpless. Sturdy parts that can take normal levels of abuse can be considered items that may only be sourced by the original manufacturer. Parts that cannot be maintained as they are too high-tech, fragile parts and consumables like filter-cartridges are considered impossible to replace on the go. If items can be improvised, that's acceptable too.

How to trust an item in the 3rd world, is a really great question. I think I would trust a regular coffee-filter, or some chemicals from the pharmacy. But it depends. Do you have any specific items in mind?

Sawyer Squeeze advertises a 1 million gallon lifespan on it's filters. so replacing them is not likely needed. If you look on their site they do a lot of international stuff in less developed countries. http://www.sawyer.com/sawyersaves/default.html

Thanks Jake, that Sawyer point-zero-two purifier is really impressive on paper. Here is my preliminary evaluation.

1) Filtration. The regular point-one-filter is not very interesting, as it does not protect against viruses. Luckily they have a point-zero-two-filter, which seem to be able doing the job. It does not protect against chemicals, but at least it can be incorporated (as is) into a filtration-system that also absorbs chemicals. Not sure about the connectors, but the hose-adapters seem straight forward.

2) Performance. The flow-rate report advertises 3 gallons per hour ("full to empty" 5 gallon bucket at sea level). That is much better than "2 gallons in 6 hours". One could wait for it while taking a lunch-break, instead of having to do it at night while sleeping.

3) Weight. The filtering-element on it's own is 12 oz (340gr). This leaves some room for the other elements (prefilter, filtering for chemicals, water-bag, hoses). May or may not stay under one pound total.

4) Maintenance. Reverse-Flow/backwash is great for self-maintenance. Easy enough and takes only a few minutes. I am not sure how rugged the filter actually is. Some filters are known to crack. It would take some more information to decide how reliable it is under rough conditions, especially at freezing temperatures (when water freezes and expands within the hollow fiber membranes), or when dropped on stone from 1m height (standard-crash-test).

All in all, the Sawyer point-zero-two purifier remains on my radar as potentially one promising element in the overall-solution. Thanks for the suggestion!

"Some filters are known to crack. It would take some more information to decide how reliable it is under rough conditions, especially at freezing temperatures (when water freezes and expands within the hollow fiber membranes), or when dropped on stone from 1m height (standard-crash-test)."

Every portable filter I know of will crack/distort micron size when stored wet in freezing conditions.
Can you give me an example of one that does not?

http://www.lifesaversystems.com/

22 oz for the bottle, but I think it meets your other criteria.

"Every portable filter I know of will crack/distort micron size when stored wet in freezing conditions.
Can you give me an example of one that does not?"

Sure: sand, char-coal, coffee-filter do not crack. But of course you are right. Most will crack. The problem with high-tech is that they are usually not very rugged, virtually impossible to repair once they break, and expensive. I left the cost-factor out of the criteria, because I believe good products may deserve steep prices. But the real cost may be one's health if they break. So reliability (here maintainability) is the key! If a filter breaks easily, why rely on it? Would you?

Okay, sand charcoal, coffee filter, you trust this against viruses, bacteria, protozoa and chemicals? I know how primitive water filters work, but they cannot match micron sizes with a precision made filter.

Are you backpacking or dropping bricks onto your pack?

your criteria seem a bit ridiculous so enjoy your mental exercise but i'm out.

Also, you say that parts on the non-tech solutions do not need to be replaced. That is absolutely untrue, the clay vessels, charcoal, sand, etc need to be replaced, it’s just that the parts tend to be more accessible. I would recommend solar still designs like this – http://www.solaqua.com/solstilbas.html

Douglas Ide: "http://www.lifesaversystems.com/

22 oz for the bottle, but I think it meets your other criteria."

Thanks for the suggestion.

1) Filtration. Great in principle for filtering both pathogens and chemicals out! There also is a pre-filter disc, some sort of sponge.

2) Performance. 0.75L water-volume. It takes a few minutes to filter it, including waiting time and pumping action. 4L requires one to repeat procedure 6 times. It may be tedious to repeat the refilling and pumping, but it is doable (on the other hand it may be nice to quickly do small amounts without complicated set-ups when walking along a stream).

3) Weight. 22 oz (620gr). Somewhat over one pound. But nicely compact it is.

4) Maintenance.
a) cleaning is a bit delicate, due to potential contamination (once contaminated, one needs 3ml of Milton Fluid or other sterilizing fluid). The caking layer on the filter-surface is supposed to be washed off on a "regular basis".
b) The manual says "DO NOT allow the membranes to dry out", so that may become a problem if the bottle remains unused as safe drinking water is available otherwise.
c) It requires silicone grease. Can the grease be improvised by anything widely available?
d) It requires specialized activated-carbon cartridges. One cartridge lasts 250l. Can they be opened to be filled with widely-available carbon?
e) When abrasive material enters the bottle, the O-ring is suggested to be replaced. Where do I get those on the go?
f) Manual: "After first use the product should be protected against freezing".

All in all it seems not be very maintainable in the long run, regardless how well it works in the first few days/weeks. Personally, I am pretty sure I would take it along for a non-winter-hike under 2 weeks; I may or may not take it around the globe.

"your criteria seem a bit ridiculous…"

that's why it is called a challenge. If it'd be easy, it would hardly be worth doing it. Thank you for your effort, anyway.

Why do they seem ridiculous to you?

"Okay, sand charcoal, coffee filter, you trust this against viruses, bacteria, protozoa and chemicals? I know how primitive water filters work, but they cannot match micron sizes with a precision made filter."

You are right, I would not rely on sand-filters, except as a backup-solution. What I mean is that there are other methods also, like chemical treatment (which is quick, but difficult to replace), or silver-coatings (which is slow but permanent, and: it has a kill-spectrum of about 100%). Just trying to steer the thinking a bit more out of the box here.

"Also, you say that parts on the non-tech solutions do not need to be replaced. That is absolutely untrue, the clay vessels, charcoal, sand, etc need to be replaced, it's just that the parts tend to be more accessible. I would recommend solar still designs like this – http://www.solaqua.com/solstilbas.html"

Exactly. The point I am trying to make is that one should be able to repair a product, even when the highly-specialized replacement parts are not available. Consumables, such as activated carbon one should be able to replace, even without having the "exact same cartridge". Some think, one should be able to shave charcoal off the wood from yesterday's fire to refill the cartridge! Why not?!

The solar-still-design your pointed out I actually like a lot. In fact, that is one of the best tested designs I have seen for stationary solar stills! It's supposed to have great-throughput, is easy to maintain/build, works even with little sunlight. That I may rely on if I stayed somewhere for weeks. Will definitely test it.

"Why do they seem ridiculous to you?"

because you want to filter everything and anything and be able to source it anywhere on the globe. Oh and it also has to be under a pound. I am having a hard time thinking of any filter that can do any one of your criteria individually (expect under a pound), but you want it all. First name a filter that can filter everything you want to filter.

Well, I accept your criticism. It's true. I want it all. I don't want to compromise when it comes to drinking water. The criteria may be hard, but they seem necessary in order to have something reliable. I mean, when I have to rely on something 99% (1% are backup-solutions), I don't want a system that only delivers 66% or 33%. One may get lucky and not get sick, or not. Safe drinking water (enough and in time without going through impractical efforts) is a big problem in a lot of places. And taking the risk is just not acceptable, at least not for me. That's why I am so adamant finding a better system. But I can also understand why you have a hard time thinking of any filter that can do that. Who here wouldn't? I know I can't. I don't now if there are any commercial products that do. But some get pretty close.

Who thinks that a solution is possible and who thinks that it won't be possible?

How effective is charcoal at removing chemical contamination? Everything I have heard says charcoal remove off-odors and flavors but cannot be relied upon effectively remove chemical contamination. I would be surprised if it was effective at all at making radioactive contaminated water drinkable.

http://en.wikipedia.org/wiki/Activated_carbon

very.

Note: you are right regarding bacteria, viruses. AC is not satisfactory in that regard. That's exactly why one needs not just charcoal, but also silver or Aqua-Mira or else. For chemicals, AC is great, as most contaminants bond to the carbon.