In this instructable we will show the process for creating clay-sawdust ceramic filters while explaining the science behind them.
This type of filter is a common solution to the problem of obtaining clean water in many parts of the world, especially rural parts of developing nations. It is a fairly simple process that involves only materials that are available in most parts of the world.
A friend of ours is away in Kenya working on various projects having to do with sustainability including filtering water for drinking. Where he is now, "water guard" tablets are used to kill bacteria, but it does nothing to improve the clarity or taste of the water so he has been experimenting with different filtering techniques. He has a local source of both clay and sawdust, making this sort of filter a viable option.
Note that this filter can only filter particles and color out of the water. It cannot filter bacteria or viruses. Water filtered through this filter is not meant for drinking, and should be boiled before being consumed.
This instructable is the culmination of a project for the Spring 2011 Stuff of History class at the Olin College of Engineering in Needham, MA.
This type of filter is a common solution to the problem of obtaining clean water in many parts of the world, especially rural parts of developing nations. It is a fairly simple process that involves only materials that are available in most parts of the world.
A friend of ours is away in Kenya working on various projects having to do with sustainability including filtering water for drinking. Where he is now, "water guard" tablets are used to kill bacteria, but it does nothing to improve the clarity or taste of the water so he has been experimenting with different filtering techniques. He has a local source of both clay and sawdust, making this sort of filter a viable option.
Note that this filter can only filter particles and color out of the water. It cannot filter bacteria or viruses. Water filtered through this filter is not meant for drinking, and should be boiled before being consumed.
This instructable is the culmination of a project for the Spring 2011 Stuff of History class at the Olin College of Engineering in Needham, MA.
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Signing UpStep 1: Raw Materials
The raw materials needed are:
Dry clay. Clay dust is probably easiest. (Warning! Clay dust is extremely harmful to your lungs! Only use outside, under a hood, or in another well ventilated area!)
Fine Sawdust. Best obtained by sieving sawdust. A #30 (600 Micon) size sieve works best, although other sizes can work. Smaller is not advised, as it will be a slow process to sieve and will slow the filtration rate. Larger can be used, up to the size of a window screen, although the filtration quality will suffer some.
Water. The purity of the water should not matter much.
A mold. The clay-sawdust mixture lacks plasticity, so using a mold to shape the pots is best.
Kiln/Furnace. We used an electric programmable furnace, although anything that can reach the required temperatures at a controllable rate will work.
Dry clay. Clay dust is probably easiest. (Warning! Clay dust is extremely harmful to your lungs! Only use outside, under a hood, or in another well ventilated area!)
Fine Sawdust. Best obtained by sieving sawdust. A #30 (600 Micon) size sieve works best, although other sizes can work. Smaller is not advised, as it will be a slow process to sieve and will slow the filtration rate. Larger can be used, up to the size of a window screen, although the filtration quality will suffer some.
Water. The purity of the water should not matter much.
A mold. The clay-sawdust mixture lacks plasticity, so using a mold to shape the pots is best.
Kiln/Furnace. We used an electric programmable furnace, although anything that can reach the required temperatures at a controllable rate will work.
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Charcoal is easier to powder, sieve to size, and would produce less outgassing of non-carbon materials. This might help control cracking and voids.
I'm talking about real charcoal - not briquets, which are made up of a combo of mined coal and wood patricles This produces a more mineral rich ash than charcoal from wood.
It is messy, but then again we are talking about working outside with sawdust and mud anyway.
Also, an easy source of clay is unscented cat litter; it's 100% clay.
Can supply to any NGOs, part of the world, ex-India, @ US $ 12 per filter. Candle costs approximately $ 0.7 US $ each, can be retrofitted in any filter
See www.cleanwater.co.in
A good way of disinfecting water is to fill it in clear pet plastic bottles and lay them in the bright sun. The ultraviolet light kills the germs.
http://en.wikipedia.org/wiki/Solar_water_disinfection
The main goal of this project was to make the water less turbid, since they already have a way of killing the bacteria and things in the water, but had no way of actually filtering particles out of the water.
If you have a kiln you can make a good drinking water filter
by adding some Silver solution to the filter production.
1) POTTERS FOR PEACE:
http://s189535770.onlinehome.us/pottersforpeace/?page_id=9
2) POTTERS WITHOUT BORDERS:
http://potterswithoutborders.com/wordpress/
Again, this is a good thing. Look at the above links and spread the word!
http://info.anu.edu.au/ovc/media/Media_Releases/2005/January/190105filters
http://s189535770.onlinehome.us/pottersforpeace/?page_id=9
you can kill viruses and bacteria by soaking the filter in colloidal silver solution for 45 seconds and let dry.
Potters for peace build potteries in south america to be operated by the local population, they have full explanationof how to build an operate a comercial press
operation and all the specs for making these filters on a large basis.
per the water issue- the purity of the water is important, do not use clorinated water, it will casue high talc clays to fail to fire correctly- fire to cone 010 (1860f)
use a mid fire or high fire high iron clay. the sawdust needs to be only wood, no plywood or melanite, as it will cause no ends of problems when it fires (carbon entraptment) ratio should be aorund 60 % sawdust by weight, mixed with 40% (by weight) of dry clay and mix with as little water as possible. a pugmill is better than a blunger in this instance, though you can hand mix in a wheel barrow with a shovel (before adding the water)
www.pottersforpeace.com
this clay needs to be pressed to ensure crack prevention.
It uses colloidal silver applied after firing to disinfect, though this plus the solar disinfection technique requires even less
Great instructable mate.
and there is a wikipedia article!
http://en.wikipedia.org/wiki/Clay_pot_filter
"Tests with the deadly E-coli bacterium have seen the filters remove 96.4 to 99.8 per cent of the pathogen — well within safe levels. Using only one filter, a litre of clean water can be produced in just two hours."
source: http://info.anu.edu.au/ovc/media/Media_Releases/2005/January/190105filters
I noticed that you're using Dry Clay as the clay base in this project. Is this terra cotta or is "Dry Clay" actually a specific type? Also, will this project be waterproof when you're finished?
We tried to select a clay that would be porous on it's own, so some of this information may change depending on the type of clay.
Unfortunately, we didn't have time for this project to test different types of clay. It would be a really cool thing to look into for the future, however.
Also how would we waterproof them? I would like to know. :]
The higher you fire the clay - the more vitrified (glass like) the clay body becomes - and therefore less porous.
Terracotta clays (low fire) are the ones you see used in garden pots - have an orange cast and are porous to some extent. You should be using Terracotta or earthenware clays. You can use stoneware clays also - firing them to low temperatures will also make them porous. Porcelain clays are expensive and very weak at low temperatures and therefore unsuitable for this process.
The most important aspect is to not fire the clay to hot - else it will vitrify and no longer be porous.
Clay comes in bags - already wet, ready to use - or as a powder with all water removed (cheaper to post). Any dry clay can be made into clay by wetting it (slaking) and wedging (massaging) it into a mass. So if you have a lump of dry clay - just add water. If your clay is old and not completely dry then let it dry before adding water - its easier for dry clay to slake its thirst and absorb the water than partially dry clay.
Sawdust acts to make gaps in the clay body - which burn out in the firing - leaving voids, or holes, for water to flow through.
Another material with similar properties to sawdust is Paper. If you mush the paper up in water until it is almost dissolved (or leave it a few days in water) then add it to the clay - the clay will be easier to work than with sawdust. I suspect the availablility of materials, in this case, is what really counts.
More info on Paperclay can be found with a google search.
The electron microscope images are very cool. Congrats on an excellent instructable
Needless to say, I think I would prefer you approach if I found myself in that environment.