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How To Build A Bio Water Filter

drinking clean water

Everyone who talks about survival eventually talks about water filtration. You see all kinds of reviews on this water filter and that—whichever is the favorite of the person doing the writing. Yet, almost all of them have one failing in common; the filter element eventually has to be replaced. While there are a few filters on the market that are backflushable to clean them out, there are only a few.

Of course, if there’s a general breakdown in society, for whatever reason, availability to filters or filter cartridges will be essentially cut off. That means that whenever your filter supply runs out, you’re going to be left with a huge problem. Since the water probably won’t be safe to drink, you’ll have to boil or distill enough for your needs, a slow process.

The biggest risk in drinking most water is that of waterborne pathogens. Bacteria, protozoa, and other microscopic parasites can be found in almost any water supply, some of which can kill you, and many of which can make you wish you were dead.

The other problem that you might end up facing is chemicals in the water. Basically, filtering systems ignore this problem, concentrating on dealing with the much more common problem of those pathogens. About the only effective ways of dealing with chemicals is by neutralizing them or by distillation. Even with distillation, it is possible to end up with some chemicals in the water, if the chemicals’ vapor point is lower than that of water.

Bio-filters, a Great Alternative

Another option, instead of buying expensive commercial filters and stockpiling them, is to build a bio-filter. This simple filtering system is used worldwide to purify water for drinking. While it may not get out every pathogen in the water, it will get out enough that you can safely drink the water, allowing your body to destroy the few that manage to get through the filter.

Actually, a bio-filter works almost the same way that a sewage treatment plant does. The standard for water treatment plants is that the water that leaves it must be clean enough to drink. To accomplish that, they use a multi-stage approach to removing anything harmful from the water. Likewise, a bio-filter uses a multi-stage approach to removing impurities and pathogens from the water, so that the water that remains is drinkable. The only difference is that you can make it yourself.

Bio-filters have three separate layers:

  • Gravel
  • Sand
  • Activated charcoal

Each of these layers removes different things, leaving the water that comes out of them clean enough to drink safely, even if you got that water from an ugly looking pond near your home.

The first layer, gravel, is there to remove large pieces of debris from the water. This would include things like small sticks, leaves, the odd tadpole and bugs. The water then moves on to the sand layer, which removes smaller particulate matter that managed to pass through the gravel. Finally, the water passes through a layer of activated charcoal to remove bacteria and some chemicals.

Ultra Efficient Water Filter Fits In Your Pocket!

It is the activated charcoal that is the secret to a bio-filter’s success. Activated charcoal or activated carbon (the same thing) is “activated” by blowing air through it. That air causes thousands of pores to open up on the surface of the charcoal, making convenient places for absorption of chemicals via bonding and capture of bacteria. The microporosity of activated carbon means that just one gram of it has over 500 m2 of surface area. That huge surface area is what makes it so effective.

Building the Bio-Filter

To build a bio-filter, all you need are the three ingredients mentioned above, along with some food grade five gallon buckets. You’ll also need some screen, a few plastic plumbing fittings and a hole saw.

There are several ways of going about this, but the way I like to do it is by using plumbing fittings between the stages of the filter. By using a fitting, you can have better control over the water flow and help make sure that the materials don’t migrate from one bucket to the next.

bio-filter fittings

To assemble your fittings and build your filter, do the following:

  • The fitting that is going to go on the inside of the bucket needs to have fiberglass screen stretched over it. That can be held in place with a rubber band or O-ring. However, gluing it makes it more secure.
  • Cut a hole in the bottom center of two buckets, which is the right diameter for the threaded part of the fitting to go through. Cut the same size hole in the side of the third bucket, which is just above the bottom.
  • Attach the fittings together, with the bottom or side of the bucket between them. The screened side of the fittings should be up. Use an O-ring between the fittings to create a seal.
  • For the bottom bucket, the one that has the fitting through the side, you may want to add a valve, an angled fitting or a fitting with a flexible tube for the outlet. Whichever you choose should allow you to have the filtered water go into a fourth bucket, pitcher or other container.
  • Cut a hole in the center of the lids for two of the buckets, which is slightly larger than the fitting. You don’t need a tight fit here, rather one that will make it easy to stack your buckets.
  • To protect the screen from the weight of the sand and gravel, put a cover over it. The easiest way to make this cover is with some small plastic cups. Drill a number of holes in the sides of the cups, so that the water can get through. Then glue the cup upside-down over the fitting.
  • Before putting your gravel, sand and activated charcoal in the filter, it needs to be rinsed thoroughly to remove all dirt and silt. When you can put on these materials, without any dust fogging the water, then it is rinsed thoroughly enough.
  • You will need to fill each bucket 2/3 to 3/4 full of the filter materials. The activated charcoal goes in the bottom bucket, which should be the one with the fitting on the side. Put one of the lids with the hole in it on this bucket. Set the bucket for the sand on top of it, and the bucket for the gravel on top. The top bucket’s lid does not need any hole in it. A plain lid can be used to keep any debris from falling into this bucket.

The finished filter will be able to process quite a few gallons of purified water per day. For the best possible water, you’ll need to aerate it after filtration. Aeration is a simple process, which adds air to the water. You can accomplish this by pouring the water back and forth a few times between a couple of buckets or pitchers.

complete bio-filter

Finished bio-filter, shown by a 750 liter (200 gallon) storage tank. The plastic tube on the front of the tank shows the current water level as being about 1/3 full.

© 2008-2014 Off The Grid News

56 comments

  1. Where do you get activated charcoal.

    • http://www.buyactivatedcharcoal.com/how_to_make_activated_charcoal
      According to a activated charcoal supplier you can use regular charcoal in place of activated Charcoal, it will need changed out more often.

      • Thanks for the info. I was wondering whereto get or to make activated charcoal.
        I see that they talk about a powder-how would you keep this from turning into a solid?
        It also appears that I can use woodfire charcoal?? Will any wood work?

        • Any hardwood can do, but pine and sycamore should not be used. The best are the Oak followed by hickory. Please do not use brush as it may be contaminated by poison Oak, or other noxious brush. Also when you are preparing to burn the oak make sure to use wood that did not have poison Oak vines growing up them as it will have residue that may cause poison ivy rash in your throat.

      • Does this filter last forever? Do you need to clean or change any of the gravel, charcoal , or sand ever? Thanks.

    • Try store that sells aquarium supplies.

    • you get the charcoal from pet store that is used for aqeriums.

    • Any pet store that has aquarium supplies.

    • I just want all to be aware that charcoal / activated carbon does NOT remove or reduce (unless by fluke) bacteria, cysts or pathogens that may be present in the water as this article would suggest (http://screencast.com/t/qtzruwX8y).

      Charcoal / activated carbon helps remove off-color, refines the general taste of water, and is primarily suited for chlorine taste and odor reduction – which is why GAC filters are so common in municipal water applications.

      Safe reduction or removal of the above dangerous contaminants should really be done utilizing “torturous path” ceramics – Doulton, Berkey, Katadyn, Aquamira, etc. This technology has been around for over 150 years because it works so well! This can also be accomplished with UV sterilization (SteriPEN, Viqua, Trojan, etc).

      I just wanted your readers to be aware! Have a great day!

  2. Your home made water filter sounds good, but like buying filters in an emergency, where does one buy “actvated charcoal”? Can it be made at home too?

  3. You can do the same thing with regular charcoal It just has to be changed out more often and can be made in your front yard.

  4. Do you know how regular charcoal is made? You DON’T want to use the kind you dump in your grill to cook food! It is laden with chemicals that would leach into your water.

  5. please notify me of all new posts

    • I am now 60, but when I was fourteen, a long time ago, we cut logs and hauled them to a charcoal Kiln where they were set afire then smothered down to burn the wood cellulose into charcoal. From there the big trucks would haul them to the manufacturer. The EPA killed the industry in the late 60s saying that it caused pollution. Funny thing is, there was less drought and more snow then. Of course sense our rain and snow are now radiated, maybe this is a good thing.

      • That is what one of my country school elementary teachers taught us about the local economy history. I can only guess that a large amount of timber was brought to a roaring fire and then buried in the earth. I always thought that you would end up with as much unburned wood as you would charcoal and ash.??
        Guess I need to answer my question by digging a hole, lighting some firewood and then burying it.

        • Earth mound method:
          Build a ‘chimney’ out of log cabin stacked sticks (~2.5cm diameter, ~30cm long).
          Fill with tinder/kindling/clean-burning stuff to start a fire.
          Pile wood around the chimney.
          Cover pile with earth; leave chimney open.
          Start fire in the chimney.
          Once fire is going well, cap the chimney.
          Patch holes in earth mound as they appear.
          Let contents burn for a day or three.

          Drum method:
          Build a fire and heat containing structure.
          Support a metal drum inside.
          Attach piping to the drum lid such that it will extend the length of the drum without being more than a few cm from the drum.
          Cap piping.
          Drill small holes along the pipe (this should remind you of a gas burner when done, but should not have as many holes).
          Fill drum loosely with wood.
          Put lid on drum with piping under the drum.
          Build fire underneath drum.
          Let it burn (the off-gases from the wood in the drum will continue cooking the charcoal after the fire dies down).
          The drum with the lid and piping should be on its side with the piping running along the bottom to act something like a burner.

          Both methods require that the charcoal be allowed to cool before unsealing it; otherwise, it will just become a wood fire.

          ALL INFORMATION IS PROVIDED FOR EDUCATIONAL PURPOSES ONLY AND IS NOT INTENDED AS A RECOMMENDATION OF ACTIVITIES TO BE PURSUED. In short, if you try anything I described and you get hurt or it doesn’t work, it’s your fault, not mine.

          • In summary, the objective is to expose the ‘material’ to enough heat to char it, and the ‘material’ must be deprived of oxygen to avoid it flaming (& turning to ash), and be certain that the container (if using a seal-able container: drum, etc) is slightly vented to avoid explosive pressure build up. If not enough initial heat with the earth mound method, you will still end up with some charcoal and some uncharred ‘material’.

  6. How often do you change the sand and gravel?
    Also how do you know when to change the charcoal?

  7. It is the activated charcoal that is the secret to a bio-filter’s success. Activated charcoal or activated carbon (the same thing) is “activated” by blowing air through it.

    Does that mean using something like an air compressor with an air-gun attachment that forcefully blows air out and basically blowing through the charcoal by hand? One effect, of course, would be to blow all the black dust away from the charcoal. Maybe when there is nothing but air going off the charcoal, then the process of opening the pores (otherwise full of dust) would be accomplished and the ability to trap micro-organisms and chemicals would be maximized and the charcoal would be officially “activated”.

    That is how I read the above info. Does that make sense to anyone (especially to those “in the know” and most especially if my theory is bass-ackwards and dead wrong)?

    Please advise…(;~))

    • Activated carbon differs from traditional carbon only in that it is riddled with small low-volume pores to increase the surface area – consequently this makes it more effective than traditional carbon because it’s able to capture more contaminants.

      Adding a compressor post-production process will not increase your media’s filtration ability.

      Refer to my previous reply above, however, in regards to contaminants because activated carbon is NOT meant for microbial, bacterial or cyst reduction of any kind. CTO and chlorine products in general are it’s primary target, as well as a few other various taste and aesthetic related qualities.

      Hope that helps!

  8. The finished filter will be able to process quite a few gallons of purified water per day.

    If one stayed on it and supplied water from a lake or pond all day long, how many gallons would result?

    Or, how many gallons per hour will the system in the top picture with the three 5 gallon buckets produce?

    Thanx!

  9. Good article but I agree it lacks specifics. How much water can be produced per day? Is burnt or “toasted” wood charcoal? How often does on change the filtering agents? Would it help to distill the water by boiling and condensation before filtering it? Perhaps over the wood one is toasting for charcoal.

    • I would disinfect after filtering. SODIS is a good method (Solar Disinfection) – it can be done in glass or clear plastic (not tinted) bottles in the sun for 8 hours. This is a cheap way of doing UV disinfection, of course you could use a UV light stage with your filter, but that requires power which you may not have off the grid. Cholrine (bleach) can be use but you need to make sure you are not using too much, about 4 drops per gallon of filtered water.

  10. This looks like a slow sand filter with an added step of the activated charcoal. What makes this filter a “bio-filter”. It appears that it will work well (depending on sand size) for parasites, and probably most bacteria. How is for filtering viruses?

    Also you did not discuss disinfection. Are you disinfecting your water after filtration.

    I build bio-sand water filters currently (www.cawst.org) please provide details on how this filter works. Thanks!

  11. If you must purchase your charcoal, what good is it if you cannot purchase in TEOTWAWKI? 1 method I saw for making charcoal is to cook wood in a slightly vented metal can over an open flame.
    How safe are the mediums and the filtered water if you wash it with potentially contaminated water?
    If my Berkey failed, I would filter this way along with Solar UV purification.

    In the video, he did not prime the filters. Berkey filters recommend initially priming (flushing out trapped air) with pressurized water in order to obtain a reasonable gravity flow rate. If I had to prime a filter, I guess I could haul 5 gallons of water and a hose up a tall tree (or rooftop) to get pressure. But at (up to) 5000 gallons per filter, would only need to do this every few years.

  12. Like so many of your articles I find this one incomplete and not very useful. You start out by stating that commercially available filters would be useless after a while because of the lack of replacement cartridges. Then you proceed to build a filter that requires activated charcoal which like the filter cartridges would not be readily available after I used up my supply. Other people above have said that regular charcoal would work but regular BBQ charcoal is usually not a good choice because of chemicals added to make it burn better. Make your own?? Most people wouldn’t know how. Some wood is toxic does anyone know which to avoid. Smoke from smoldering wood is toxic. In the middle ages charcoal makers were a strange group of people because of brain damage from breathing the fumes from charcoal making. It wasn’t just hatters that were mad from chemical poisoning.

  13. I recomend buying enough activated charcoal in advance to have it on hand when change out becomes necessary. I also suggest learnng about wihich wood is appropriate to use for charcoal making, and practice. Then after all that, me your flters, and disinfect the water before drinking.

    You can be sure that there will be very limited power available, if any for “normal” people. Practice doing without one day a month. Turn off the TV two days a month. My kids went four years without TV in the UK. They survived and were better for it.

    Get the book series “Foxfire” . It teaches us how others without modern conveniences were able to survive and thrive.

    • I do know that All kinds of Oak and Hickory are good to use as filters. Ash is also, but is hard to find sense the Asian elm blight almost wiped it out. Do not use sycamore, locust, any unidentified brush This brush may contain poison Ivy and poison Oak which, if used to filter water could cause internal rash that would be hard to treat and , any kind of wood pallets (because what it has transported is unknown) Use no soft wood. They contain rosins that are poisonous.

  14. I have known for a long time that if you want to make charcoal you get the fire going then choke off the air. hardwoods, especially All Oak wood is good. Ash is good, so is Hickory. Do not use brush, as you do not know if it has poison Oak or other poisonous brush in it. Do not use any soft wood because the rosin is not good for you, and for gosh sake do not use Pallets, as you do not know what kind of residue they have on them left from shipment. They could have everything from cement particles to toxic residue embedded that you can not see.

  15. I would not recommend charcoal replacing activated charcoal. If you had nothing else and had to do it, but they are not the same.

    • And what do you do when it is not available?

      • In that case, I would not hesitate in turning my Firewood into Charcoal. Would come in useful for making gunpowder as well.

        • Buddy that is what the Elite with the real money and power is planning, maybe as early as this fall the hejaz pilgrimage comes back from Saudi Arabia with the virus that will combine with one or more now on the way here and kill billions (Man Made) or when Ison commit which is actually about the size of the moon comes in. The evil they have planned for the rest of us is beyond comprehension.

    • The way activated charcoal works is that it has many microscopic pores in it that capture impurities and trap them, it also bonds with or adsorbs some contaminants and impurities. Activated carbon also has a mild positive electrical charge added to it which attracts negative ions in the contaminants drawing them to the surface of the carbon and removing them from the water. When the carbon has bonded with all the contaminants and impurities it can hold it is considered to be no longer “activated”.

      Activated charcoal can be made from almost anything that will char (wood, coconut shell, etc.) or has a high carbon content (bituminous coal). The smaller the pores the smaller the amount you need and the longer it lasts. Currently coconut shell is considered to be the best material to use. However any material will work. (DO NOT use charcoal briquets as they are glued together and may contain impurities you don’t want).

      Two suggestions for if you make your own charcoal:
      `1) you can char it in an oxygen starved environment:
      Put your wood or whatever material you choose in a metal container and throw it on a fire
      Important: put a small hole on top of the container to let out moisture etc. and to keep it from exploding, also don’t get excited if the escaping gases light on fire or even through out a jet of flame as this is normal -woodgas.
      2) Or you can just start a fire, wait until it’s burning well and then smother it with dirt. The next day after it cools you can dig up your charcoal.

      Also the charcoal will work best the smaller you can make it. So crushing or grinding it is a good idea (more surface for the water to go through).

      If the charcoal is getting old and not working as well (or at least every 6 months) you can reactivate it by baking it in a single layer at 300F for at least one hour.
      After reactivating it’s best if you repeat it every 2 months and only do it approximately 3 or 4 times as you’ll lose 5–15 % of adsorptive capacity every time.

  16. The plastic components in this system all contain dangerous phthalates and bisphenol A (BPA) which contribute to all manner of illness, cancer and endocrine disruption – thus defeating the very intent of obtaining and drinking pure water.

  17. I totally agree with gmo2ashes. Isn’t it easier and probably healthier to just buy a water filtration system. In a long run it is not as expensive as people think it is.

  18. Plastics that have the triangular arrows emblem on the them with any of these 3 numbers in the middle of the triangle and these letter(s) or word under the triangle should be avoided:

    Number 3 with a letter V under the triangle (PVC or Vinyl can contain phthalates)
    Number 6 with the letters PS under the triangle (Polystyrene Foam – only unsafe if used to
    heat foods or beverages)
    Number 7 with the word Other under the triangle (Can contain bisphenol A (BPA)

    Any plastics with these numbers in the triangle and these words or letters below it are safe to use:

    1 – PETE
    2 – HDPE
    4 – LDPE
    5 – PP

    What are the health effects of Phthalates and BPA?

    Many doctors and scientists are concerned about phthalates and BPA because they can act in ways similarto hormones naturally found in our body. Hormones help control how our body works. Most of the health information we know about these chemicals comes from animal studies.
    In studies using rats, phthalates cause problems with male reproductive organs. In children, scientists
    have found an association between phthalates and changes in reproductive hormones and increased
    allergies, runny nose, and eczema. In adults, phthalates are associated with changes in sperm quality.
    Bisphenol A may cause changes in cells in breasts, the uterus, and the prostate which can increase risk of cancers. In addition, BPA has been associated with increases in developmental disorders of the brain and nervous system in animals. These developmental disorders in animals are like problems such as ADHD (attention deficit hyper-reactivity disorder) in humans.

    Information taken from:
    http://aoec.org/PEHSU/documents/bpa_patient_july_8_08.pdf

  19. This setup is useful, but not against disease. It’s good for removing large particulate matter (floating sand, plant material, dirt) but too large grained for small life (protozoa, viruses, bacteria.) It’ll make the bad tasting (but not bad for you) water taste better, reduce grit and make ‘wild’ water easier to drink. You can use this to remove the solids before sending the water into a container for SODIS or boiling/distillation. Or use in conjunction with chemical treatments but to ONLY use charcoal filters on possibly contaminated water is taking too many risks.

  20. Hi, Darren
    I agree with you. A water filter is an essential water treat device at home. I have installed an under sink water filter in my kitchen and I have enough water to consume. I don’t need to stand the bad odor and taste of chlorine.

    • Kitchen filters are convenient but rely on pressurized water (I’m suppose some can be remounted into a gravity fed system). My son added a faucet mounted PUR which he claims to make the water taste better. I barely notice any taste difference between PUR, Berkey or Faucet. My observation is that for the cost of replacement filters, my Berkey’s 5000 gallon capability is the best choice & gravity fed if/when utility fails. Am tempted to add on the Flouride filter to the Berkey.

      • In north Texas where we lived they had windmills hooked to sealed wooden tanks that were mounted on poles as tall as the roof of the house. The windmill pumped the water into the tank which ran the gravity fed system in the house. I would say our pre-power ancestors were pretty smart, too bad we lost that ability.

  21. This is one way to filter water, not the only way. if you are relying on one way to do most things necessary for survival or sustainability then you are in bigger trouble than you know. this is a great way to get “unknown” water filtered for the garden or pretreated before and additional filter is used for drinking. if you are making charcoal then boil water while you do it, make a still and collect the steam, put water in glass jars and let the UV from the sun kill off a few nasties in there.

    Be prepared but prepare if your prep fails.

  22. People please know that you can only drink distilled water for a short time. Like only 3 days before it starts affecting your kidneys. Good for a short time but bad for long periods.

    • This is not true. You can drink distilled water whenever you like. As long as your diet contains sufficient electrolytes to keep your body from having an electrolyte imbalance. Anything resembling a normal healthy diet will work in this regard.

  23. An interesting article that does have a few holes in it. Thankfully, there are a lot of informed and educated comments that help fill in the blanks. A question I have is where would one get food-grade 5 gallon buckets for free or cheap? I’ve heard that one can get them from bakeries but I’m not really sure. Any advice or info would certainly be VERY helpful.

    • I used to get food grade buckets from donut shops and/or grocery stores that have bakeries. The filling for donuts used to come in food-grade plastic buckets. Some stores will sell them to you, others may give them to you.

  24. ヴィトン バッグ モノグラム チャンルー キムタク http://www.753m.com/

  25. My well water is not safe to drink so I’ve been drinking distilled water for 28 years (gallon jugs from the grocery)…. if it’s so bad why am I still alive (I’m 74)?
    For 7 years I lived on a farm with a very deep well… because it had hydrogen sulfide in it, the system was to pump it into a cistern to let that evaporate, then pump it into the house. The cistern was old, leaking, brick, and I considered it not safe. So I added 12 drops (not 4) of bleach to a gallon jug of water, let it sit for 24 hours, then put it thru a small carbon filter.
    A gallon jug of bleach would last a long time using 12 drops at a time. Having several on hand for many
    uses is a good idea anyway. For such small amounts aquarium charcoal should be good.

  26. 1. Anything but pool filter sand is too course, will not hold beneficial bacteria for this filter, nor remove cysts etc.
    2. Sanitize final filtered water with diluted pool shock mixed at a tsp per gallon of water then this bleach solution is used in small amounts to sanitize filtered h2o. (Survivalblog.com water treatment facility). Effective ness of bleach begins to drop off as soon as becomes liquid. Dry pool shock kept dry in glass containers will last indefinitely.
    3.this system must be started and ran daily to build the bio feature. Ie: use the water, pond,collected rain water etc. consistently to maintain beneficial flora.
    4. Container can be purchased commercially, reasonably, then filled, with components, total cost about $200
    5 Proven design found to be very effective in 35 3rd world countries in decreasing diarrheal diseases, >70%.
    Checkout above site!

  27. Thanks for investing so much of your valuable time to educate us!
    Please share your experienced perspective on implementing Citric Acid in filtration.

  28. In an effort to answer these questions we can look into some details about how it is made and more importantly, why do we need it and how is it used. Many of those questions can be answered when we disclose where it is used, which is somewhat impressive, read this article (http://www.bulkactivatedcarbon.net) for all the desired info.

  29. thanks for sharing us your knowledge. we really need to have a good water purification system now that millions of people are dying from different diseases they acquired from drinking unfiltered water

  30. Water is essential for health, hygiene and the productivity of our community. water treatment process may vary on the water condition that you have in your area. its better to invest on a good water treatment. it will benefit you by providing safety to you and your family.

  31. The cheapest place to buy quality activated charcoal that I’ve found is blackwatercarbon.com. They sell it by the pound.

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