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Biotech Technology

Water Filtration With a Tree Branch 205

Posted by Soulskill
from the do-you-think-solutions-like-this-grow-on-trees dept.
Taco Cowboy writes "Dirty water is a major cause of mortality in the developing world. 'The most common water-borne pathogens are bacteria (e.g. Escherichia coli, Salmonella typhi, Vibrio cholerae), viruses (e.g. adenoviruses, enteroviruses, hepatitis, rotavirus), and protozoa (e.g. giardia). These pathogens cause child mortality and also contribute to malnutrition and stunted growth of children.' People have been working on engineering cheaper and cheaper filtration systems for years, but now a group of researchers has found a promising and simple solution: a tree branch. 'Approximately 3 cm^3 of sapwood can filter water at the rate of several liters per day, sufficient to meet the clean drinking water needs of one person.' 'Before experimenting with contaminated water, the group used water mixed with red ink particles ranging from 70 to 500 nanometers in size. After all the liquid passed through, the researchers sliced the sapwood in half lengthwise, and observed that much of the red dye was contained within the very top layers of the wood, while the filtrate, or filtered water, was clear. This experiment showed that sapwood is naturally able to filter out particles bigger than about 70 nanometers.' The team tested E. coli-contaminated water, and the branch was able to filter out 99 percent of the bacterial cells."
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Water Filtration With a Tree Branch

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  • First time? (Score:4, Insightful)

    by DogDude (805747) on Friday February 28, 2014 @12:32PM (#46368677) Homepage
    If this is true, then this is a really profound discovery that could help millions of people.

    What I'm wondering, is why no other society, that we know of, has discovered this low-tech, yet seemingly incredibly useful thing previously?
    • If this is true, then this is a really profound discovery that could help millions of people. What I'm wondering, is why no other society, that we know of, has discovered this low-tech, yet seemingly incredibly useful thing previously?

      Maybe because all of the other materials and equipment required to make it work.

      • by Anonymous Coward on Friday February 28, 2014 @12:48PM (#46368801)

        If this is true, then this is a really profound discovery that could help millions of people.

        What I'm wondering, is why no other society, that we know of, has discovered this low-tech, yet seemingly incredibly useful thing previously?

        Maybe because all of the other materials and equipment required to make it work.

        You mean like some sort of cutting implement to cut down the branch?

        I think the hatchet was invented at least 10 years ago?

      • Maybe because all of the other materials and equipment required to make it work.

        Fill a metal container with water, plug the opening with wood, heat, collect and condense steam.
        My brother and I used to do that sort of thing as kids (except the last bit). However if you take the wood out of the above method you have a normal still, villager's don't build stills because they require too much fuel.

        Another simple idea that I saw on Aussie TV a while back was simply to mix a bit of charcoal into clay and make it into a pot. The resulting pot is porous, fill it with raw sewerage and the w

    • Re:First time? (Score:5, Insightful)

      by i kan reed (749298) on Friday February 28, 2014 @12:37PM (#46368725) Homepage Journal

      Ideas can be publicized, studied in more detail, or put to good use, without being truly new.

    • Re:First time? (Score:4, Interesting)

      by Em Adespoton (792954) <slashdotonly.1.adespoton@spamgourmet.com> on Friday February 28, 2014 @12:37PM (#46368727) Homepage Journal

      24So the people grumbled at Moses, saying, "What shall we drink?" 25Then he cried out to the LORD, and the LORD showed him a tree; and he threw it into the waters, and the waters became sweet.

      • by K. S. Kyosuke (729550) on Friday February 28, 2014 @01:14PM (#46369019)

        1) Someone mentions a new discovery.
        2) Find a passage in the Bible containing the (rather common) keywords, without actually using your brain to check that the passage has identical informational value.
        3) ???
        4) Prophet!

    • by Anonymous Coward on Friday February 28, 2014 @12:47PM (#46368789)

      "Somebody probably thought of that" is more likely to be untrue than true. You probably are the first person to think of that. And even if you aren't you might be the first person to act on the idea. And even if you aren't you might be the first person to succeed where others have failed. And even if you aren't, you might learn something. So don't ever say that, "somebody probably thought of that."

      Filtering water through wafers of wood is not obvious to me. I do engineering for a living. If you are wondering why no one ever discovered something before, go back to paragraph one and repeat.

      • by K. S. Kyosuke (729550) on Friday February 28, 2014 @01:25PM (#46369155)
        It *is* obvious - after a fashion - since plants are generally doing just that; i.e., they use their root systems and cappilaries to absorb water including some impurities up to a certain size. The issue of "can we cut away a part of a plant tissue and filter water through it?" is probably more of a quantitative nature, rather than qualitative. As in, what is the filtering capacity? Does it clog? If it does, how often does it need to be changed? Does it rot? If so, how often does it need to be changed? The qualitative issues here seem to be "given that we're killing the plant, how does it affect the filtration process?" and "what preparation techniques can we employ to increase the practicality?". It's not that we don't have any filtration media, it's about how our knowledge and manufacturing processes make the individual filtration media more or less practical.
      • Tapping water from a tree is a well known survival technique. Getting water from vines even more so.

        I believe archaeologists have found ancient village sites with a pit filled with layers of sand, charcoal, wood and plant fibers (crushed material, pounded on rocks ?), etc. It was the village water purification system. Not exactly wafers but interestingly close.

        So with respect to things that humanity has been doing for millions of years, getting clean water in this case, I tend to be a little more open
        • by shaitand (626655)
          Charcoal is well known for it's use in purification. I'm curious if this works better than using charcoal and if the decay of the living tissue actually ends up making this less safe than just rendering that wood to charcoal.
      • by gtall (79522)

        The Cat Flap. Douglas Adams (in I think Dirk Gently's Holistic Detective Agency) makes the comment of consider the cat flap, that door within a door. When the first person invented it, everyone else who thought about it said, yeah, well, I could have thought of that...except they didn't.

    • Re:First time? (Score:5, Informative)

      by Em Adespoton (792954) <slashdotonly.1.adespoton@spamgourmet.com> on Friday February 28, 2014 @12:49PM (#46368813) Homepage Journal

      If this is true, then this is a really profound discovery that could help millions of people.

      What I'm wondering, is why no other society, that we know of, has discovered this low-tech, yet seemingly incredibly useful thing previously?

      Well, I learned this technique as part of my Aboriginal American studies when I was growing up -- I think it's more likely that our western culture has "lost" this knowledge than that nobody has discovered it before.

    • by knarfling (735361)
      Probably because the wood has to remain damp in order to be effective. Once the wood dries, it loses the ability to filter well. Water runs through crack and the pores don't filter properly.

      This is not something you could set up, let sit in storage for a few weeks, pull it out and expect it to be effective.

      It looks like it would be most effective on a small but not personal level. With a small group you could filter enough water to keep the wood damp for a long time, replacing the "filter" as needed. So
      • by Grishnakh (216268)

        Sounds great for villages in developing countries, but it doesn't look like it would scale very well.

        Um, isn't that the whole idea here? I don't think anyone's thinking of using tree branch slices for commercial-quality water filtration in Western countries. No one's going to start selling tree branch slice filters for Samsung and GE refrigerators and Pur faucet adapters. The whole idea here is to come up with ultra-cheap, low-tech, but effective methods of improving quality of life and health and sanita

        • Re:First time? (Score:4, Insightful)

          by MightyYar (622222) on Friday February 28, 2014 @02:20PM (#46369631)

          When people have to hike for miles to find wood for cooking fires, I'm not sure that fresh cut wood is all that practical.

    • There are other methods like slow sand filter, bio sand filter, and solar disinfection.

      https://en.wikipedia.org/wiki/... [wikipedia.org]

      https://en.wikipedia.org/wiki/... [wikipedia.org]

      https://en.wikipedia.org/wiki/... [wikipedia.org]

      Thou with SODIS use glass if you can do to the endocrine disruptors BPA and BPS
      being in most plastic bottles.

      https://en.wikipedia.org/wiki/... [wikipedia.org]

      • by drinkypoo (153816)

        Sadly, glass is less effective because of its tendency to block UV. You have to let the water get up to temp in a glass bottle. I bought a cute little doodad with some kind of phase change wax sealed in glass that changes color (sort of) when the water reaches an adequate temperature.

      • Thou with SODIS use glass if you can do to the endocrine disruptors BPA and BPS being in most plastic bottles.

        The very Wikipedia article you linked to says to use PTE bottles, because some glass bottles will absorb the UV before it gets to the water, and that the leaching of material from plastic bottles into the water has been studied and found not to be of concern.

    • Re:First time? (Score:5, Insightful)

      by hawguy (1600213) on Friday February 28, 2014 @01:18PM (#46369077)

      If this is true, then this is a really profound discovery that could help millions of people.

      What I'm wondering, is why no other society, that we know of, has discovered this low-tech, yet seemingly incredibly useful thing previously?

      For one thing, it doesn't filter viruses, so maybe it's already been evaluated and dicarded as a good solution. From TFA:

      Karnik says sapwood likely can filter most types of bacteria, the smallest of which measure about 200 nanometers. However, the filter probably cannot trap most viruses, which are much smaller in size.

      So it's of limited utility, since, as the summary says, common pathogens include viruses (e.g. adenoviruses, enteroviruses, hepatitis, rotavirus) -- for example, rotavirus is around 30nm in size, less than half the effective filtering size of the wood.

      So the water will probably still need chemical or UV treatment after filtering.

      Plus it's not clear how well it would work in the field, when the scientists built their filter:

      They cut small sections of sapwood measuring about an inch long and half an inch wide, and mounted each in plastic tubing, sealed with epoxy and secured with clamps.

      So while wood as a filter medium sounds attractive, if the user needs specialized equipment to get it to make a safe, water-tight seal, maybe it's not as useful in an area with limited resources.

    • Lack of information (Score:5, Informative)

      by Immerman (2627577) on Friday February 28, 2014 @01:53PM (#46369415)

      You can make a pretty decent biofilter simply by folding a piece of cotton cloth such as an old Indian sari a few times - it'll remove 99% of cholera and many other particularly nasty infectious agents. Yet people are still getting infected because they don't know about the simple solution - it's not a technology problem, it's a public information problem. And spreading public service announcements among a population where where most people don't even own a radio is a serious challenge. Doable, but expensive and there's no profit in it, so it usually falls to small humanitarian organizations that do their best to make the information go viral, and usually fail. Getting a meme to go viral is a lot more difficult when it can only spread through face-to-face interactions.

    • by shaitand (626655)
      I wouldn't jump to the conclusion that nobody has discovered this. The utility is likely somewhat reduced when you consider that A. places with trees everywhere generally have water about and B. tree branches rot.
  • The most common water-borne pathogens are bacteria ...,viruses ...,and protozoa

    Well, that pretty much covers it I guess. I was surprised the kingdom animalia didn't make it on the list, but then hey, I'm no biologist.

    In all seriousness, this is a very interesting discovery and I hope it leads to cheap and widely accessible drinking water.

    • Re: (Score:2, Insightful)

      by fustakrakich (1673220)

      ...I hope it leads to cheap and widely accessible drinking water.

      Coca Cola and Pepsi will do all they can to make sure that never happens. Water is big business. That is why access is so difficult.

      • Access to the sky for water is free in most states though a few totalitarian
        nut job states like Colorado make it illegal to collect water that falls on your roof....

        • by Pope (17780)

          So that it flows back down into the water supply and keeps downstream places hydrated.

    • by spune (715782) on Friday February 28, 2014 @01:14PM (#46369029)
      There already are low-cost, natural water filtration techniques being used across the world that produce clean water at a higher rate, like biosand filters. For water projects i have previously worked on, how quickly water is purified has been a significant practical concern for the folks who would benefit from the project. That was the reason that solar stills were dismissed, for example; they require more effort and materials to construct, but even then have a higher flow rate than the xylem filter. Also, how often the filter must be replaced is another big practicality issue.
    • by gnick (1211984)

      We can never let that happen. As a member of PETP, I demand to know whether the trees were properly anesthetized prior to being bled alive, used without consent as subjects for scientific testing, and mutilated. If these trees were young, were their parents consulted? Color me outraged.

    • by jpvlsmv (583001) on Friday February 28, 2014 @02:01PM (#46369477) Homepage Journal

      Water-borne pathogens in the kingdom Animalia are usually called "predators" rather than "pathogens". But yes, pathogens such as A. Mississippiensis can be filtered from the water with an appropriately-sized tree branch.

  • HA!

    I always love it when somebody discovers a natural, free way to accomplish a goal that someone else wants to sell me a solution to.

    • by Flatwater (2169620) on Friday February 28, 2014 @12:37PM (#46368721)
      Filtering out "99%" of harmful bacteria may be like filtering out 99% of bullets fired at you....
      • by CanHasDIY (1672858) on Friday February 28, 2014 @12:43PM (#46368759) Homepage Journal

        Filtering out "99%" of harmful bacteria may be like filtering out 99% of bullets fired at you....

        So, I take it you're not a fan of Lysol or Purell?

        What a silly thing to say; as if not filtering 99% of something harmful is a better idea...

        • In the case of Purell, its Triclosan that is an issue.

          http://www.huffingtonpost.com/... [huffingtonpost.com]

          Maybe they have removed it, maybe not.

          https://en.wikipedia.org/wiki/... [wikipedia.org]

          On its own its not the worst threat in the environment, but when you add it along with
          others the combined threat is pretty bad and would explain the reduction of quality of
          health compared to some other nations.

          • I think you missed the point - it's less about what's in Purell, and more about the whole "killing 99% of germs is better than not killing any of them" concept.

        • What a silly thing to say; as if not filtering 99% of something harmful is a better idea...

          OP does have a quite valid point...I worked in water testing lab years ago so I have some experience with this. The EPA standard [epa.gov] for coliform in drinking water is zero, that is to say one e. coli bacteria in a water sample (usually 100 ml) means the water is contaminated. (And generally when water is contaminated, there will be far more than just one bacteria per 100 ml.)

          So while, yes, removing 99% of the bacterial load is better than not, as a general rule a 99% effective "decontamination" process still

          • Regarding OP's analogy, if someone fired 100 bullets at me, and I had a way to automatically block 99 of them, I'd have to be an idiot to not use that method just because 1 bullet might get through.

            Yes, I might still get shot, but at least I won't be riddled with holes.

            • Yes, but, the OP didn't say that one shouldn't use the method...those were *your* words and *your* assumption. The analogy simply points out that '99% removal' may not be adequate in this particular case.

          • What I've always wondered is, how does the infection rate relate to the number of bacteria? Is "it only takes one" a true statement? I.e., if just one bacterium slips through the filter, are you as likely to get an infection as if a million slipped through? Or is there some "critical number" of bacteria, below which a normal immune system can easily handle things, but above which infection tends to set in?

            • It depends on a lot of factors. First of all, for e. coli, most strains are harmless and so 1 or 10,000 of those cells won't really affect you. However, the greater the number you ingest, the greater the chances that you'll get one of the pathogenic strains. For someone with a normal immune system, I'd expect the chance of just one cell causing an infection is exceedingly small, but for someone with compromised immunity it would obviously be much higher.

              But as I mentioned upthread, when water is contam

      • by alta (1263)

        Yes, it is. And I'd rather be hit by the one bullet than all 100 of them. I'd stand a much better chance of living.

        Especially since there's a much better chance of your body's natural defenses defeating that 1%

        • by denzacar (181829)

          Bullets don't divide and multiply every 15-20 minutes while just sitting there in the air waiting to hit you.
          Or in the case of bacteria, while swimming there in the water you're still slowly filtering.

          However, this method is probably still useful for filtering out various other harmful particles found in water.
          And if you got wood and tools to construct a filtering apparatus, you can probably boil that filtered water too.
          Yeah, yeah, I know, they were testing this as a solution for people who can't afford bur

          • And if you got wood and tools to construct a filtering apparatus, you can probably boil that filtered water too.

            As TFA points out, the problem with boiling water is fuel consumption, whereas filtering through a cold tree branch requires no fuel whatsoever, other than the physical energy exerted by the tree branch user.

      • I'm pretty sure that law enforcement (in the US) and military (anywhere) would frenetically jump at the idea of body armor capable of reducing the probability of bullet injury by 99%.
      • I worked with an organization who did biosand filters in the Dominican republic and Haiti, they actually wanted there filters to leave a small amount of the bacteria because then it aloud the people who were using the filters to build up an resistance in case they ever drank water that was not filtered.
      • No, but if you had 100 bullets coming at you and had the opportunity to hold a shield that would catch 99 of the bullets, would you really refuse holding it because it wouldn't catch 100% of the bullets? You don't stop the bullets by saying "don't come at me until I have a shield that will stop all the bullets."

      • by Hadlock (143607)

        Your immune system is virtually bullet proof under those circumstances

    • by Rhacman (1528815) on Friday February 28, 2014 @12:47PM (#46368791)
      Take what? Take their money to the bank when their plastic funnels and tree-branch-filtration kits sell like hotcakes to the very folks hoping to, ahem, "stick" it to the man?
    • Well, it's not completely free -- someone likely owns those trees. And people living in desert regions of the world don't have easy access to sapwood -- nor do people in parts of the world where the sapwood is of the wrong consistency in local trees (hardwoods, for example).

      • Well, it's not completely free -- someone likely owns those trees. And people living in desert regions of the world don't have easy access to sapwood -- nor do people in parts of the world where the sapwood is of the wrong consistency in local trees (hardwoods, for example).

        Yea, guess you've got me - I mean, it's not like a person can just, you know, stick a seed in the ground, tend to it properly, and bada-bing-bada-boom, a tree will grow, right?

        • Most people need clean water on a regular basis and cannot accommodate waiting for a tree to grow to quench their thirst.
          • Most people need clean water on a regular basis and cannot accommodate waiting for a tree to grow to quench their thirst.

            Where did I say it was a perfect solution? At least it's something more than "dur, you have to buy trees from someone."

            Do you have anything relevant and useful to add, or did you just come here to whine that the solution I offered isn't perfect?

        • by gnick (1211984)

          ...stick a seed in the ground...

          Have you checked the price of tree-worthy ground lately? Or materials to provide nutrients and hydration to said ground? I started digging a nursery on Broadway, but the local traffickers got all bent out of shape. Do you have a cow? Because I have a pocket full of very young trees I'd like to trade you.

          • ...stick a seed in the ground...

            Have you checked the price of tree-worthy ground lately? Or materials to provide nutrients and hydration to said ground? I started digging a nursery on Broadway, but the local traffickers got all bent out of shape. Do you have a cow? Because I have a pocket full of very young trees I'd like to trade you.

            Sorry, all full up on trees (half my state is a national forest, after all); although, if you have a few hundred feet of copper wire to spare, I'm sure we could work out some kind of barter.

            • by gnick (1211984)

              Only a few hundred? Great! I'll get them delivered. Just set up a small box down-town with a charging socket on a post and a sign that says, "Free for the first 2 months - Leaf and Volt owners only!" That way my delivery people know that they're bringing you the wire for free. They'll drive the wire to your collection station and attach them to let you know they're ready to be harvested. I'll throw in some batteries too if you're willing to invest in a pry-bar.

              As far as the delivery of the cow... I'm

      • by maharvey (785540)

        And people living in desert regions of the world don't have easy access to sapwood...

        People living in desert regions probably get their water from wells, which is relatively clean.

        People living in more temperate regions where there is excess water are more likely to drink the dirty surface runoff. It's not that water is scarce, it's that it is dirty. Where I live, trees are weeds... I have to pull tree sprouts up by the dozens every year to keep my yard from turning into a rainforest. But we don't drin

    • by tomhath (637240)

      somebody discovers a natural, free way to accomplish a goal

      Really? Doesn't look all that free or natural to me:

      1 inch-long sections were cut from a branch with approximately 1 cm diameter. The bark and cambium were peeled off, and the piece was mounted at the end of a tube and sealed with epoxy. The filters were flushed with 10 mL of deionized water before experiments. Care was taken to avoid drying of the filter.

      Approximately 5 mL of deionized water or solution was placed in the tube. Pressure was supplied using a nitrogen tank with a pressure regulator. For filtration experiments, 5 psi (34.5 kPa) pressure was used.

      • So... $0.25 worth of epoxy? I don't see anything there that couldn't be done for free or, at the very worst, an incredibly low cost. You can pressurize a container with a make-shift hand pump, for example.

      • OK, so for purposes of writing up a paper and reporting methods, yes, it's not all that free or natural. But in practice it is. You could cut a section from a branch to fit tightly in a tube or funnel, no epoxy needed and no real reason why it would have to be round if it's easier to make a different shape. Wood tends to swell slightly when wet, so it could make itself air tight. Then, while it's convenient to use nitrogen from a tank to provide pressure and simultaneously avoid contamination in a lab setti
        • You really need a good seal to maintain pressure and make it tight enough to keep out microorganisms. It's hard to see how you can do this for free.

          Certainly there are scaling problems with this too.

          Another thing about this process is that like many ideas for cleaning water it lacks the ability to keep the water clean after it's processed. The residual effect of chlorine and related materials is one of the reasons chlorine is so tough to beat - after you apply it a residual of hypochlorous acid keeps the wa

    • I always love it when somebody discovers a natural, free way to accomplish a goal that someone else wants to sell me a solution to.

      This filtration requires use of Monsanto's patented PureWood trees. Use of any other wood type for filtration will result in severe DMCA penalties.

    • by DaveV1.0 (203135)
      Yeah! Now all these people in the developing world have to do is chop down even more trees. Deforestation, YAY!. Oh, wait....

      Well, at least this will help people living in slums and favelas in places like Manila, Rio, etc. because sapwood is free, cheap, and highly available there. Oh.... wait...
      • Yeah! Now all these people in the developing world have to do is chop down even more trees. Deforestation, YAY!. Oh, wait....

        Well, at least this will help people living in slums and favelas in places like Manila, Rio, etc. because sapwood is free, cheap, and highly available there. Oh.... wait...

        OK, so are you going to suggest a better idea, or just troll (then whine in your sig when your troll-y posts are appropriately modded)?

  • by hort_wort (1401963) on Friday February 28, 2014 @12:35PM (#46368697)

    "It's so beautiful. It's hard to believe these spores could kill me."

  • Exactly how do you pour water THROUGH a branch? This sounds like the old boyscout prank of expecting someone to push a rope. Or maybe this is more like herding cats?

    • by srmalloy (263556)

      I would expect that you'd need something like a large pottery vase or jar with a tapered hole in the bottom. You cut the length of sapwood, wrap one end with a fiber cord until you can push it down into the hole and have it fit tightly with the branch sticking out the bottom (a rubber gasket would be better, but may not be readily available), then pour your 'raw' water into the vase and hang it over another container to catch the water that passes through the branch. A higher-tech solution would use some so

      • by Immerman (2627577)

        Sub-technological cultures... that would be things like communities of apes, right? Wait, no. Even they have a degree of language and other culturally-transmitted technology such as termite-fishing with sticks.

        Low-tech yes, sub-tech no. Don't contribute to the trap of thinking technology = modern high-tech technology. Language, money, stone axes, etc. all had their heyday as high technology, and assuming we don't wipe ourselves out there will come a day when today's smartphones and airplanes look every b

    • by ansak (80421) on Friday February 28, 2014 @12:54PM (#46368855) Homepage Journal
      The article quoted above points to a paper [plosone.org] that has some diagrams that shows how water would go through a branch -- no hoax here.

      In brief, find a stalk of sappy wood -- my Dad showed us every spring how to make a whistle out of alder branches that look what the picture shows -- peel it, whittle it to size and then plug it into the end of a tube and gravity feed water through it.

      simple...ank
    • by sdoca (1225022)
      If you'd RTFA, you'd know they put branch into a tube (fit tightly) and fed the water thru it that way.
    • by fisted (2295862)
      you do realize that passing water/nutrients through is the primary function of branches, right?
    • by neo-mkrey (948389)
      Mythbusters recently proved that you can't herd cats.
  • by Jason Pollock (45537) on Friday February 28, 2014 @12:40PM (#46368741) Homepage

    Trees are great at dealing with bacteria.

    We soon found that disease bacteria such as these were not recoverable from wooden surfaces in a short time after they were applied, unless very large numbers were used. New plastic surfaces allowed the bacteria to persist, but were easily cleaned and disinfected. However, wooden boards that had been used and had many knife cuts acted almost the same as new wood, whereas plastic surfaces that were knife-scarred were impossible to clean and disinfect manually, especially when food residues such as chicken fat were present.

    http://faculty.vetmed.ucdavis.... [ucdavis.edu]

    • by swb (14022)

      That's why I let my dog lick my plastic cutting boards clean and then run them through the dishwasher with the "heat dry" and "sanitize" settings.

      The dog licking is amazing. If I cut red meat on it and wash it in the dishwasher with the above settings, the board is still faintly stained. But when the dog is done, even before washing, there is NO staining.

      So far, nobody here has gotten sick...

      • by Pope (17780)

        Try giving it a rinse with white vinegar first instead of letting the dog lick it.

  • Bacteria filtration is awesome for the wood filters.
    Also, one has to be very careful not to let the wood dry out, because drying out damages the ability of the wood to pull water through, and if dried wood DOES let water through, it isn't filtered.

    --PM

  • After all its pretty well-known that from some trees you can get pretty good drinking water (as in: clean) so one would just naturally assume that somewhere between the roots and the trunk where you normally tap in, the thing would get filtered ... and alas there is not much in between except wood.

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