But the heat will make the plastic molecules leach into the water faster.

I agree with Jasmin. Personally I'd prefer glass bottles/jars, however I understand the need for water may be more important for survival than to worry about leaching of nasty things from plastic.

I'd be nice to see more sustainable fixes (like glass) than temporary/non-sustainable ones (like plastic).

People should realize that some types of plastic block the necessary UV rays that have the greatest killing power so that the UV never hits the water. Heat from the sun is usually not sufficient to kill many of the most pathogenic microbes. All using this technique should switch to an alternative method since this is certainly not fool proof. Many other techniques are equally inexpensive and have a much greater efficiency (low% bleach, iodine tablets).

There is no way that low% bleach and iodine tablets are less expensive and efficient than sunshine. The last time I checked, I didn't have to pay anything for sunshine. Also no method is foolproof. The U.S. method is a good example of this and finds no harm in poisoning its own low income citizens with toxic water and air every day.

plastic bottles do cost money unless you go dumpster diving which I am sure isnt good if you plan on drinking out of it.
Simply put, would you like to tell a destitute individual to use this method of purification if he is still at high risk for getting cholera and dying. The efficacy of bleach and iodine is beyong reproach. Furthermore, iodine and bleach are not poison. Iodine is a essential component in T3 & T4 thyroid hormone (people used to get goiters b/c of the lack of iodine in salt) and bleach is made by our body in macrophages to kill intracellular and extracellular organisms. We actually have an enzyme called myeloperoxidase which generates the same thing (hypochlorus radicals). Dont tell me this is poisonous and dont decieve yourself.

No human body enjoys toxin overload. Overuse of iodine and bleach has been proven in numerous studies to enable bad germs to become drug resistant. Not only do the bad germs become drug resistant, but the good germs fighting the bad germs are destroyed in the process. I'm not saying this article is the answer to water problems in third world countries. What I am saying is that it is nice to have alternative ideas flying around and it's nice to give people credit for coming up with them. In response to your dumpster diving comment; in this article about third world countries, many citizens "dumpster dive" for survival; and I certainly have no problem with someone trying to survive.
I think the deceit can be left to those who have the knowledge to solve the world's problems, but lack the compassion to carry it through.

So natural substances are toxins? What studies? Very little is resistant to bleach and iodine, so little that publications that exhibit the phenomenon make big news. Once again, most plastics will prevent UV from ever hitting the water to kill the microorganisms , and heating water to below boiling temperatures will not kill microorganisms.

I don't believe that all natural substances are toxins, but I do believe that an overload of certain natural substances can turn into toxins. I don't recall saying anything about sunshine and plastic bottles being strong enough to kill all micro-organisms; and again to my knowledge there is no safe product in the world that is strong enough to eliminate every harmful bacteria in all water.

To me, articles like the one above are a way to begin the brainstorming process for alternative ideas that are less harmful. I think you would agree that if bleach and iodine were so readily available, inexpensive, efficient, healthy, and perfect for third world countries; they would each already be using it.

When I read this article I was under the impression that this method was meant for poverty stricken people in situations that prevented them from accessing potable water. Obviously this isn't meant for municipal projects. To people in these situations any material obtained is priceless. "Dumpster diving" may be a way of life. Most would not find iodine or bleach readily available. Therefore the system is perfect for such times. Oh yeah, I know bleach isn't poisonous because I accidentally drank an 8 oz glass once...........

John,

in response to 'so natural substances are toxic' - if you think about it you'll see the answer is hell yes.

The body makes and uses several "chemicals" that in the wrong amounts are toxic. I mean bleach not toxic? Chlorine bleach? John, Chlorine gas was used as a chemical weapon in WW One.

Its all in the amounts. Even drinking too much clean water can kill you.

There are certainly many "natural" substances that are toxic to the human body. The first things that come to mind are arsenic, lead, mercury..

But I suppose it depends on how you define "natural" in this context.

OK folks whatever. The methods I suggested are the cheapest and most efficient ways-FACT. The above method is not proven, prone to many problems as listed, and certainly not foolproof. Point being, if I was an aid worker, I have to ask myself would I give an poor indiviudal a glass of water purified in by an unproven method or a tried and true inexpensive method. When you have to make that decision (as I have), aka chosing between being the giver of probable disease that could cost someone their life, you can complain about toxins etc.

Has anyone ever studied the water of the Ganges River or read any of the books by scientist Masuru Emoto? Both are very interesting. The Ganges known as a holy river but also one of the most polluted in the world, yet the water continues to cleanse and refresh itself (possibly by the strong flow and oxygenation? Or something else?). Both attest to the effect of positive language and/or prayer over water. I have no religion at this time, but I find the information on this interesting. Can water react to emotion? If so, can it react to sunshine as a positive emotion?

John,

I find it hard to give much credit to what you say when you refuse to admit something as obvious as Iodine and Chlorine being toxic at certain levels.

If we must continue this:
http://www.goodsam-md.org/12810.cfm

Iron is another essential nutrient that we can easily overdose on. Just read the label on any bottle of vitamins.

If anyone has seen "Blue Vinyl" there is a PVC lobbyist that argues that dioxins are not toxic because they're just chlorine, which is found in salt, which we eat. I find it extremely frustating when educated people make completely false statements to justify their ends, assuming the rest of the world is too stupid to realize they're lying.

UV light as a sterilizer is nothing new, and hardly unproven. Yes, some types of glass and plastic can absorb UV light. Perhaps the article left out some details and it's good of you to point this out.

I think it's safe to say a village could more easily find plastic containers than a constant supply of chlorine or iodine. Even if we assume these materials had to be provided to them, once the UV method was established, the village could produce water almost indefinitely with no outside assistance, while chlorine or iodine would need to be resupplied or purchased periodically.

If you're going to demand sources from others, maybe you should provide something a bit more informative than "OK folks whatever" when people disagree.

so apparently my discussion on toxins has been overblown. DUH anything in excess is bad for you. but if used at low percentages that are used in water purification, these methods can be used chronically. Please realize that all of us can and do think and know that ingesting whole bottles of inorganic nutrients can kill you. we're argueing over something that goes understood by most thinking and breathing individuals. I dont debate the use of UV as a sterilizer, I use it daily in a cell culture hood. I do debate the concept of using random plastics and glass as containers to sterilize, and do debated the lack of sufficient heat. This is why we have autoclaves. Once again it isnt as effective and therefore much more dangerous because of the potential harm of ingesting a highly pathogenic strain of campylobacter, e.coli, or shigella, all of which may kill you in short order.

as a side note, chlorine and iodine arent considered as toxins according to the strict definition a la webster because they arent proteinaceous.

I found a disease you can't get from water. No joke people.

It's called NPD. NPD stands for Nasty People Disorder. I bet everyone is glad that if we drink water in a third world country; we won't die from it. Unfortunately though, we can't help those who already have it.

It reminds another design, the cone water, designed by a German industrial Stephan Augustine. Its mechanism is quite similar: the sun produces water drops.

thuan, thanks for the link. That site is chock full of neat things and ideas. ;)

Why would this work if you leave the plastic out in the sun wouldn't the molacules in the plastic(which melt in the heat) go in to the water?

Hi there, I am an industrial designer looking at sterilizing water for the third world and how it can be accomplished cheaply and so the water is as safe as possible. Is it viable for the water to be boiled and left to cool? I have a method to boil it cost effectively. Thanks

I'm just now catching up on back Treehugger articles. This one caught my eye as I do a lot of solar cooking. Plastic bottles scare me when used for cooking/sterilizing. Solar Cookers International (solarcookers.org)has a cheap solar cooker that can be used to sterilize water (with a black pan, no plastic) and I believe sell indicators that let you know if it has reached appropriate temps. They are a cool site with lots of info for working with solar in developing countries. I'm with the group that says NO to iodine and bleach in the body at artificial levels, but also with the group that says NO to sterilizing water in plastic (which sadly might mean iodine and bleach in some circumstances).

Let's get some things clear everyone.

UVB rays are the ones that burn, UVA rays are the silent killers that may cause skin cancer/wrinkles etc. UVB cannot travel through glass, only UVA can. So the questions remain 'are UVA rays alone sufficient enough to kill the germs in plastic bottles? Is this method safe enough for long term consumption or emergencies only?' If this method is that good, why isn't it used more often? Why are the Africans still drinking unsafe water?

Another point we should look at is relying too much on plastic bottles as a source of water purification, may increase the already heavy burden on the environment. Plastics take between 100-200 years to break down, in that time leaching chemicals into the soil and water. Making them also burns alot of energy. Recycling them isn't really effective because there are only 2-3 types of plastics that are able to be recycled. And even then, you are down-cycling as each generation of recycled plastic is not as pure or strong as the original - some may even require more chemicals to be added to purify or alter their structure.

As with what John said, I do think he has a valid point. If there was an emergency (like Katrina for example) and all you found was a plastic bottle and some dirty water and you haven't drank in 3 days. That method might save your life! Everyone should be made aware of easily accessible and simple ways to obtain emergency water during a crisis. But to use it as a method to sterilize water for everyday consumption might not be that safe, as it hasn't been established whether water in plastic when heated by sun's rays will kill all bacteria present in dirty water.

As for the natural substance thing.. poison ivy is natural. Oxygen is naturally everywhere. Dirty water is natural and so is clean water. It doesn't matter what the substance is, moderation is the key. Too much or too little and you may be screwed. Oxygen is vital for life, but at the same time, each breath you take also oxidizes you a little. But without oxygen you'd die in a minute. As with bleach and iodine, they're effective methods, how safe are they depends on how much you use. There are also different grades of bleach too! Using the fragranced ones will probably injure or kill you if consumed.

There's another water sterilizing method I've used before which is pretty good (although expensive). Colloidal silver. 5ml of it will sterilize 250ml (8oz) of water. I know it doesn't sound like alot but it does kill bacteria and viruses. Because it is a natural substance, viruses cannot become resistant to it. Depending on the manufacturer and the size of the silver (ppm), they've been proven to work against the smallest germs and drug resistant viruses. A US based company is trying to get cost effective colloidal silver to help malaria victims in Africa. Patients have shown to recover after taking it for 3 days. But you know, all these methods cannot get rid of ALL the bad substances in dirty water. Heavy metals usually have to be filtered. Or the water has to be distilled.