Simple Tree Branch Filter Removes 99 Percent of E. Coli from Water

Simple Tree Branch Filter Removes 99 Percent of E. Coli from Water

Filter

MIT researchers have tested a water filter fashioned from a tree branch that may be the low-cost solution to water filtration in developing countries.

New research from MIT has revealed that nature may have an inexpensive solution for water filtration. By taking a small piece of a simple pine tree branch, peeling off the bark, and fastening it to the end of a tube through which water will be poured, you can create a filter good enough to remove 99.9% of E. coli from water.

At least, those were the results reported by MIT mechanical engineers in a paper published yesterday in PLOS One. "I listened to this talk about how water flows through plants, and it occurred to me that the flow of water has to pass through these membranes in xylem," said Rohit Karnik, coauthor of the study. Xylem is part of a plant's vascular system, which transports water and dissolved minerals throughout its body. "We tried freshly cut sapwood and found that it actually works," Karnik says. "We were able to show that it can filter."

According to Rick Andrew, global business development director of water systems at the National Sanitation Foundation International, these sapwood filters could potentially be the low-tech solution for water purification. He does have his reservations, however - tests will need to be conducted to determine how the filter holds up to heavily polluted water, which may clog it.

Source: PLOS One, via Popular Mechanics

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While I'm not greatly familiar with the science of tree branches, how fast will water actually pass through these filters? Great that it's cheap and works, but less great if you have to wait a week for a cup of water.

Jadak:
While I'm not greatly familiar with the science of tree branches, how fast will water actually pass through these filters? Great that it's cheap and works, but less great if you have to wait a week for a cup of water.

Relatively quickly. Trees can process vast amounts of water in a day. However I do not think it's very practical. The xylem could get very easily clogged. And on top of that, being a piece of once living material it can and will soon become a breeding ground for various bugs in of itself.

Plus you probably need rather immense pressure to filter the water. You can do this using a hand pump but I still don't expect much.

The fact that 99.9% of e. coli is removed implies that the pore size is sub micrometer. Without appropriate prefiltering it's a neat party trick but not practical.

I also think the amount of branches needed to actually filter enough drinking water would pretty much lead to insane deforestation if this was actually adopted on a wide scale.

crepesack :

Jadak:
While I'm not greatly familiar with the science of tree branches, how fast will water actually pass through these filters? Great that it's cheap and works, but less great if you have to wait a week for a cup of water.

Relatively quickly. Trees can process vast amounts of water in a day. However I do not think it's very practical. The xylem could get very easily clogged. And on top of that, being a piece of once living material it can and will soon become a breeding ground for various bugs in of itself.

Plus you probably need rather immense pressure to filter the water. You can do this using a hand pump but I still don't expect much.

The fact that 99.9% of e. coli is removed implies that the pore size is sub micrometer. Without appropriate prefiltering it's a neat party trick but not practical.

Actually, if they keep it wet it should last for a very long time. As long as wood stays wet it wont rot.

Rotting and being a substrate for bacteria are different things.

I'll admit, when I first read the title...

...but after reading through the article and understanding the thought processes behind it all...

The more you know, huh?

Umm, this is gonna sound weird but... this was a known fact already. I mean, that's awesome that they did full experimentation and it was rigorously tested and all (I loves me some rigorous testing). The USDA did tests regarding this years ago, after a fiasco that involved the forced switching from wood cutting boards/tables to those plastic ones. They force everyone to switch on assumption that it was better for cleaning and handling bacteria, only to have it tested later to show that significantly more bacteria was present post washing on the plastic. The conclusion was that despite the fact that wood is so porous, none of the bacteria could enter into the pores of the wood. The plastic though, yuck. Of course, if you never worked in the meat industry, you never heard about this. And if you worked in the meat industry, you still may not have heard about this. It's not known because it was a sweeping mandate for the whole industry and it was a bad, very unsanitary decision.

Baresark:
Umm, this is gonna sound weird but... this was a known fact already.

It wasn't an MITTM known fact so nobody cared enough to share it. I remember learning about it when a Pizza place was shut down in a town near my hometown after someone nearly died due to food poisoning. They tracked it down to a new plastic counter. The newspaper did an article on it and everything.

Anyway, it'll be a start to dealing with terrible drinking water conditions but its far from a permanent solution.

Baresark:
Umm, this is gonna sound weird but... this was a known fact already. I mean, that's awesome that they did full experimentation and it was rigorously tested and all (I loves me some rigorous testing). The USDA did tests regarding this years ago, after a fiasco that involved the forced switching from wood cutting boards/tables to those plastic ones. They force everyone to switch on assumption that it was better for cleaning and handling bacteria, only to have it tested later to show that significantly more bacteria was present post washing on the plastic. The conclusion was that despite the fact that wood is so porous, none of the bacteria could enter into the pores of the wood. The plastic though, yuck. Of course, if you never worked in the meat industry, you never heard about this. And if you worked in the meat industry, you still may not have heard about this. It's not known because it was a sweeping mandate for the whole industry and it was a bad, very unsanitary decision.

i remember watching a science show on this exact thing around 20 years ago and found that would contains natural antibacterial properties

Rhykker:

According to Rick Andrew, global business development director of water systems at the National Sanitation Foundation International, these sapwood filters could potentially be the low-tech solution for water purification. He does have his reservations, however - tests will need to be conducted to determine how the filter holds up to heavily polluted water, which may clog it.

I volunteer Lake Erie for the field test in question. Not only is it a high source of E. Coli, but it has other pollutants in it and, in fact, has been ON FIRE before.

This is all well and good but the species of tree in question does not grow in the climates which developing nations tend to have.

Euh, might just be me stating the obvious. But what happend to good old fashioned boiling? We allready have relatively cheap filters for this kind of thing that developing countries can use for mass production. And if you are talking about a village setting: just boil it for 10-20 minutes and any bacteria will be dead. Not automatically the spores but if you drink it after boiling that shouldn't be a problem... Boiling kills parasites, bacteria and even virusses. That filter will not stop virusses or take out toxins. Boiling will destroy those for you. (the toxins that are deactivated by heat anyways...)

So... boiling? no? Anyone?

Hell, give me a pig bladder and a couple of tubes and I'll build you a rudimentary dialysis machine. It's cool with the wood filter thing but I just don't see the point tbh...

iseko:
Euh, might just be me stating the obvious. But what happend to good old fashioned boiling? We allready have relatively cheap filters for this kind of thing that developing countries can use for mass production. And if you are talking about a village setting: just boil it for 10-20 minutes and any bacteria will be dead. Not automatically the spores but if you drink it after boiling that shouldn't be a problem... Boiling kills parasites, bacteria and even virusses. That filter will not stop virusses or take out toxins. Boiling will destroy those for you. (the toxins that are deactivated by heat anyways...)

So... boiling? no? Anyone?

Hell, give me a pig bladder and a couple of tubes and I'll build you a rudimentary dialysis machine. It's cool with the wood filter thing but I just don't see the point tbh...

Boiling needs fuel. Lots of fuel, either in the form of gas or wood, and it cannot really be performed on municipal levels. Passive filtering is much more energy-efficient and cheaper that that.

Also, please define what kind of "toxins" you are talking about and tell me why you automatically presume they are in the water. I really hope it's not the silly "new age" kind of "toxins" you are talking about...

GabeZhul:

iseko:
Euh, might just be me stating the obvious. But what happend to good old fashioned boiling? We allready have relatively cheap filters for this kind of thing that developing countries can use for mass production. And if you are talking about a village setting: just boil it for 10-20 minutes and any bacteria will be dead. Not automatically the spores but if you drink it after boiling that shouldn't be a problem... Boiling kills parasites, bacteria and even virusses. That filter will not stop virusses or take out toxins. Boiling will destroy those for you. (the toxins that are deactivated by heat anyways...)

So... boiling? no? Anyone?

Hell, give me a pig bladder and a couple of tubes and I'll build you a rudimentary dialysis machine. It's cool with the wood filter thing but I just don't see the point tbh...

Boiling needs fuel. Lots of fuel, either in the form of gas or wood, and it cannot really be performed on municipal levels. Passive filtering is much more energy-efficient and cheaper that that.

Also, please define what kind of "toxins" you are talking about and tell me why you automatically presume they are in the water. I really hope it's not the silly "new age" kind of "toxins" you are talking about...

If you have heavily contaminated water and the conditions are just right (goldilocks zone pun) certain bacteria produce toxins (i.e. S. aureus, C. Botulinum, B. cereus that last one is not going to do that in water to be fair, more like grain and rice). Some of these can't be deactivated by heat. Like the ones produced by S. aureus. If those are in the water, no amount of tree filtering or boiling is going to save you from the explosive diarhea that is about to follow. The ones from say C. botulinum can be deactivated by heat. Which is a good thing because those toxins are a lot nastier.

True, boiling is energy consuming and not very efficiŽnt. However, it all depends on the setting/context you are working in. If you are talking about 1 family then I'd say boiling. If you're talking city then I'd go with larger industrial complexes.
I assume they are targeting small communities with this project. Again you can add a lot of context but I'd still try and build something like a reed bed in lava stones or something. Trying to build a filtration system using trees for small communities is going to be A) hard to build for desireable production and B) high maintenance. Then again I'm just talking about knowledge in my head. Not done much research on the topic since its not really my field. It... just... doesn't seem feasible for large scale production. Not when you consider other more realistic alternatives.

Ps: same goes for the toxin productions. I know certain bacteria CAN produce toxins in water. But I'm more familiar with bacteria producing toxins in food. So I'm not saying that my examples (S. aureus..) will produce toxins in water.

iseko:

GabeZhul:

iseko:
Euh, might just be me stating the obvious. But what happend to good old fashioned boiling? We allready have relatively cheap filters for this kind of thing that developing countries can use for mass production. And if you are talking about a village setting: just boil it for 10-20 minutes and any bacteria will be dead. Not automatically the spores but if you drink it after boiling that shouldn't be a problem... Boiling kills parasites, bacteria and even virusses. That filter will not stop virusses or take out toxins. Boiling will destroy those for you. (the toxins that are deactivated by heat anyways...)

So... boiling? no? Anyone?

Hell, give me a pig bladder and a couple of tubes and I'll build you a rudimentary dialysis machine. It's cool with the wood filter thing but I just don't see the point tbh...

Boiling needs fuel. Lots of fuel, either in the form of gas or wood, and it cannot really be performed on municipal levels. Passive filtering is much more energy-efficient and cheaper that that.

Also, please define what kind of "toxins" you are talking about and tell me why you automatically presume they are in the water. I really hope it's not the silly "new age" kind of "toxins" you are talking about...

If you have heavily contaminated water and the conditions are just right (goldilocks zone pun) certain bacteria produce toxins (i.e. S. aureus, C. Botulinum, B. cereus that last one is not going to do that in water to be fair, more like grain and rice). Some of these can't be deactivated by heat. Like the ones produced by S. aureus. If those are in the water, no amount of tree filtering or boiling is going to save you from the explosive diarhea that is about to follow. The ones from say C. botulinum can be deactivated by heat. Which is a good thing because those toxins are a lot nastier.

True, boiling is energy consuming and not very efficiŽnt. However, it all depends on the setting/context you are working in. If you are talking about 1 family then I'd say boiling. If you're talking city then I'd go with larger industrial complexes.
I assume they are targeting small communities with this project. Again you can add a lot of context but I'd still try and build something like a reed bed in lava stones or something. Trying to build a filtration system using trees for small communities is going to be A) hard to build for desireable production and B) high maintenance. Then again I'm just talking about knowledge in my head. Not done much research on the topic since its not really my field. It... just... doesn't seem feasible for large scale production. Not when you consider other more realistic alternatives.

Ps: same goes for the toxin productions. I know certain bacteria CAN produce toxins in water. But I'm more familiar with bacteria producing toxins in food. So I'm not saying that my examples (S. aureus..) will produce toxins in water.

Fair points. Please excuse me for my dismissal related to the word "toxins", as I am an active skeptic and as such I meet with the pseudo-scientific version of the word far, far more often than the scientific one.

As for the actual topic, I think this will come down to economics and the cost/efficiency ratio in the end. I still think that passive filtering is much more cost-effective than boiling since the price of fuels in developing countries is much higher relative to the average income of a household.
It is also important to note that most of the developing world doesn't have tap-water. In fact the bigger problem is probably the lack of drinking water, period, and that can only be solved by investing in municipal water filtration and delivery services for which boiling is very, very ineffective while these wooden filtration plugs might provide a cheaper method of building up a water-system that the local governments can actually afford.

for all of you talking about it being not use able mass scale,
I would like to point out that science figured out how to replicate how geckos cling to pretty much whatever the hell they want (even glass)(seriously here is a BBC page on it http://www.bbc.com/news/science-environment-19875247) I am sure science can figure out how to replicate the filtering process of this tree given some time

I have my doubts as to how useful this will be in developing countries and the authors point it out too:

Second, the wood must be freshly cut to work as an effective filter. The team say that the conduits in wood that has dried become blocked and so don't work as filters. That's a potentially serious problem should these filters need to be supplied on a large scale-distributing them around the world while keeping them fresh will be hard.

The wood needs to be freshly cut and countries that don't have an abundance of pine forests are kind of screwed unless they are able to import fresh-cut trees or set up a tree farm.

Makes me wonder if someone could genetically modify some trees or tree-oids to work as better filters and grow in poor conditions.

GabeZhul:

iseko:

GabeZhul:
snip

If you have heavily contaminated water and the conditions are just right (goldilocks zone pun) certain bacteria produce toxins (i.e. S. aureus, C. Botulinum, B. cereus that last one is not going to do that in water to be fair, more like grain and rice). Some of these can't be deactivated by heat. Like the ones produced by S. aureus. If those are in the water, no amount of tree filtering or boiling is going to save you from the explosive diarhea that is about to follow. The ones from say C. botulinum can be deactivated by heat. Which is a good thing because those toxins are a lot nastier.

True, boiling is energy consuming and not very efficiŽnt. However, it all depends on the setting/context you are working in. If you are talking about 1 family then I'd say boiling. If you're talking city then I'd go with larger industrial complexes.
I assume they are targeting small communities with this project. Again you can add a lot of context but I'd still try and build something like a reed bed in lava stones or something. Trying to build a filtration system using trees for small communities is going to be A) hard to build for desireable production and B) high maintenance. Then again I'm just talking about knowledge in my head. Not done much research on the topic since its not really my field. It... just... doesn't seem feasible for large scale production. Not when you consider other more realistic alternatives.

Ps: same goes for the toxin productions. I know certain bacteria CAN produce toxins in water. But I'm more familiar with bacteria producing toxins in food. So I'm not saying that my examples (S. aureus..) will produce toxins in water.

Fair points. Please excuse me for my dismissal related to the word "toxins", as I am an active skeptic and as such I meet with the pseudo-scientific version of the word far, far more often than the scientific one.

As for the actual topic, I think this will come down to economics and the cost/efficiency ratio in the end. I still think that passive filtering is much more cost-effective than boiling since the price of fuels in developing countries is much higher relative to the average income of a household.
It is also important to note that most of the developing world doesn't have tap-water. In fact the bigger problem is probably the lack of drinking water, period, and that can only be solved by investing in municipal water filtration and delivery services for which boiling is very, very ineffective while these wooden filtration plugs might provide a cheaper method of building up a water-system that the local governments can actually afford.

Hehe no worries. I thought it was something like that.
Back OT: you're probably right. Like I said: far from my main field of research. I was just wondering if someone could explain to me the actual benefits of this technique over more conventional tried-and-true techniques. It seemed like a nice science experiment but not implementable in upscale production.
And your arguments are all true btw. They filter water in modern installations. I'm just doubting that this technique is going to be cost effective. It could be but I'm nothing if not a sceptic ;)

CriticalMiss:

Makes me wonder if someone could genetically modify some trees or tree-oids to work as better filters and grow in poor conditions.

Not a bad idea, though I have a feeling the anti-GMO crowd would flare up even against that.
Also, while this test was done on pine wood, it doesn't mean other types of wood wouldn't work, they just need to do more testing, and that's what the kind of do at MIT. :P

@iseko: We'll see. If it works, great. If it doesn't, at least it pointed the research at some interesting directions, which is also great. This is why the scientific method is awesome.

I love it when humanity spends truckloads of cash and countless hours of work to create some system or technology, only to discover nature beat ups to it millions of years ago. Bravo planet Earth!

Jadak:
While I'm not greatly familiar with the science of tree branches, how fast will water actually pass through these filters? Great that it's cheap and works, but less great if you have to wait a week for a cup of water.

crepesack :

Plus you probably need rather immense pressure to filter the water. You can do this using a hand pump but I still don't expect much.

There's a link to the actual article in the OP. PLOS One is a free journal.

http://www.plos.org/wp-content/uploads/2013/05/pone-9-2-boutilier.pdf

"In addition, the pressures of 1-5 psi used here are easily achievable using a gravitational pressure head of 0.7-3.5 m, implying that no pumps are necessary for filtration. The measured flow rates of about 0.05 mL/s using only 1cm 2 filter area* correspond to a flow rate of over 4 L/d, sufficient to meet the drinking water requirements of one person"

* and 2.6cm in length see page 5

I would suggest everyone who's genuinely interested reads it.

iseko:
far from my main field of research. I was just wondering if someone could explain to me the actual benefits of this technique over more conventional tried-and-true techniques. It seemed like a nice science experiment but not implementable in upscale production.

They filter water in modern installations. I'm just doubting that this technique is going to be cost effective. It could be but I'm nothing if not a sceptic ;)

[Edit: I just re read your post and I now realise you were replying to someone who had just explained all this. Doh! However, reading the article's discussion and conclusion is recommended.]

http://www.plos.org/wp-content/uploads/2013/05/pone-9-2-boutilier.pdf

Well no, the point of this is not industrial production, it's to provide a cheap source of filtering to little village in the middle of nowhere that is about as likely to get access to filtered mains water in the next 20 years as I am to get into government with my Kill All Humans party. It's not the magical cure all solution to water access in LDC's but it does try to address a specific problem.

Also apologies for double post.

So how does it stand up to the moss and charcoal standard of water filtration?

Old wilderness survival trick, will filter out pretty much all bacteria and lots of other toxins and pollutants.

The charcoal will neutralize a lot of toxins, and the moss is anti-bacterial. Take a container, like a tin can, make some holes in the bottom, add moss, add charcoal on top of moss, pour water through. Drink.

One day my log will have something to say about this. My log saw something that night.
OK, OK, low-content post. OT, a first I was thinking that might be a good solution for hikers, but there are better portable water filtration systems available than "rubber tube and hope you find an appropriately-sized pine branch. As far as third-world applications, it just doesn't seem that practical to me; it looks like it would require a great deal of maintenance for very little result.

This might be interesting in a Ray Mears kind of way, if you're out camping or something and want to filter your water being able to grab an appropriate tree branch would save on the kit you need to carry.

Zykon TheLich:

iseko:
far from my main field of research. I was just wondering if someone could explain to me the actual benefits of this technique over more conventional tried-and-true techniques. It seemed like a nice science experiment but not implementable in upscale production.

They filter water in modern installations. I'm just doubting that this technique is going to be cost effective. It could be but I'm nothing if not a sceptic ;)

[Edit: I just re read your post and I now realise you were replying to someone who had just explained all this. Doh! However, reading the article's discussion and conclusion is recommended.]

http://www.plos.org/wp-content/uploads/2013/05/pone-9-2-boutilier.pdf

Well no, the point of this is not industrial production, it's to provide a cheap source of filtering to little village in the middle of nowhere that is about as likely to get access to filtered mains water in the next 20 years as I am to get into government with my Kill All Humans party. It's not the magical cure all solution to water access in LDC's but it does try to address a specific problem.

Also apologies for double post.

I suppose. I've been reading up on this topic. Having this as an end-point water purification method seems valid enough for developing countries. More specifically small community villages. You would have to co-implement it with some other technologies. It also depends on the climate ofcourse. I'm about to do a suggestion that would not work in the sahara for example :).

Sedimentation bed -> first reed bed -> second reed bed -> filtration (using the proposed technique).

The sedimentation would remove larger particles. The reed beds are very efficient at removing chemical polution of all kinds really. Depending on the micro-organism they can even remove heavy metals and extremely toxic compounds. In the research paper for the filter they explicitly say that biological contamination is the main contributor for death by poluted water. However, chemical contaminants are still an issue that the filter cannot address. Having these prior steps would also help in prevention of premature filter clogging. Allthough the same principle kind of applies as you see with HEPA filters. The filter will work better with some clogging from contaminants. Right up until the point that the pressure difference becomes to great and you need to clean it.

A last step could be to produce drinkable water by filtration. You can split up your initially filtrated water (i.e. by the reed beds). The water you filtrate is used for drinking and cooking. The non filtrated water for washing etc. One problem is still that if you filtrate this water and then let it stand a week before consumption you risk secondary infections (since its not chlorated). So you'd have to produce drinking water on a consumption basis.

The main "irk" I have with this in general is that developing new technologies for developing countries is ofcourse a good thing. But then you would need to implement that technology over there and find people that can perform maintenance. I am not saying the local population are idiots. Far from it! But you are talking of communities that are isolated with a rudimentary school system at best. You'd need to train the local population to maintain these sytems. Give a man a fish, teach a man to fish kind of thing. I think the main struggle will be there. Not that it is impossible but still. Most of use have at least a basis of science that allows us to understand the basic principles behind this research. Those people (I am forced to use a generalization eventhough I know it is not strictly true everywhere) were taught nothing of the kind. Basic math and reading is usually where it ends. It does not matter how *simple* you make it. This is not something that you can build and then say: now leave it running for 20 years and whatever you do don't touch it.

I hope noone interprets this as offensive. Not really the point of this post... And written word can easily be misinterpreted.

TL;DR: I agree with the potential benefits of this technique but I'm still concerned with general implementation (of any technique).

Cerebrawl:
So how does it stand up to the moss and charcoal standard of water filtration?

Old wilderness survival trick, will filter out pretty much all bacteria and lots of other toxins and pollutants.

The charcoal will neutralize a lot of toxins, and the moss is anti-bacterial. Take a container, like a tin can, make some holes in the bottom, add moss, add charcoal on top of moss, pour water through. Drink.

You need activated coal for that. Remember: small communities, very isolated, poor, drinkable water for 50-100 people on a daily basis.

chickenhound:
I am sure science can figure out how to replicate the filtering process of this tree given some time

The filtering process is "pass the water through a membrane". We replicated that a very long time ago, and can do it far more effectively than trees if we want. The point to this is not the discovery of some amazing new technique, it's about the possibility of having a cheap and easy way of doing it using local resources, rather than actually needing to produce and ship around - and importantly pay for - the things science can already produce. It's like the Liter of Light idea. Science doesn't need to figure out how to make windows, mirrors or light bulbs, but not everyone has access to or can afford them so it's useful to find other cheap, effective solutions. Similarly, we can already filter water, but not everyone actually has access to or can afford existing solutions so figuring out you can do a decent job with a stick in a pipe could be very useful.

iseko:

The main "irk" I have with this in general is that developing new technologies for developing countries is ofcourse a good thing. But then you would need to implement that technology over there and find people that can perform maintenance. I am not saying the local population are idiots. Far from it! But you are talking of communities that are isolated with a rudimentary school system at best. You'd need to train the local population to maintain these sytems. Give a man a fish, teach a man to fish kind of thing. I think the main struggle will be there. Not that it is impossible but still. Most of use have at least a basis of science that allows us to understand the basic principles behind this research. Those people (I am forced to use a generalization eventhough I know it is not strictly true everywhere) were taught nothing of the kind. Basic math and reading is usually where it ends. It does not matter how *simple* you make it. This is not something that you can build and then say: now leave it running for 20 years and whatever you do don't touch it.

I hope noone interprets this as offensive. Not really the point of this post... And written word can easily be misinterpreted.

TL;DR: I agree with the potential benefits of this technique but I'm still concerned with general implementation (of any technique).

No, not offensive at all.

I think that's why this system is being proposed:

Stick piece of wood in end of hose. Change piece of wood every week. That's it. Pre filter with cloth to remove larger particles beforehand. As you said, they're not idiots.

The main issue I see is either in finding local trees with the same xylem properties as coniferous trees (by far the best option) or if that can't be done, getting the wood where it needs to go without the filtration properties deteriorating.

 

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