Catalyst reveals the secret to using cow dung to clean up water for drinking. Maryke Steffens goes down to the paddock to put this unimaginable idea to the ultimate taste test.
Narration: Cow dung. It's not often the stuff of great ideas.
But for one scientist, the humble cowpat provided the inspiration - and the means - to create a simple yet life-changing device...
...that uses cow dung to make clean drinking water.
The man behind this bizarre idea is materials scientist Tony Flynn.
Tony Flynn: Quite a large slice of the developing world... what water there is, is very often contaminated.
Narration: Water-borne, diarrhoea-causing bacteria, such as E. coli, kill 1.6 million people every year.
But water filters are beyond most people's means.
So Tony decided to try and design a cheap and simple water filter that Anyone can make Anywhere.
And we're going to put that claim to the test.
First stop is a field outside of Canberra - for raw ingredients.
Maryke Steffens, reporter: Tony is this what we're looking for?
Tony Flynn: Yes, this type of clay occurs all around the world.
Maryke Steffens, reporter: Well, let's get some then!
Narration: We're making our filter from clay because it's easy to use and most importantly... it's free.
But clay isn't without its problems...
...which Tony ran into on his first filtering attempt.
When he tested his initial prototypes for water flow... not much happened. The problem was in the clay.
Tony Flynn: They were so dense the water wouldn't come through at all.
Maryke Steffens, reporter: So it just wasn't porous enough?
Tony Flynn: No.
Narration: Tony knew he had to find a way of creating more spaces in the clay so the water could filter through.
And inspiration wasn't too far away... at the local coffee shop.
Tony's idea was to add organic material - like used coffee grounds - which would burn up in the firing process and leave holes in the clay.
Tony Flynn: ...and these are materials that are widely available around the world and in the developing world.
Narration: But would it work?
Tony tried out coffee grounds, tealeaves, and rice hulls mixed with the clay...
... and this time, the water flowed.
Thin slices of the filters revealed the new gaps in the clay.
Tony Flynn: That's clay to which coffee has been added. The large holes were made by coffee grains.
Maryke Steffens, reporter: And so the bacteria just get trapped as they travel through this?
Tony Flynn: Yes because the bacteria are slightly bigger than the smaller holes that you can see here. It's that simple.
Narration: Now it's time to take the science from the lab into the field... and put my "cooking" skills to the test.
Maryke Steffens, reporter: OK, so I've got my clay, got my coffee grounds...how much of each goes into the mixture?
Tony Flynn: Well, equal parts. One handful of clay, one handful of coffee grounds.
They came from a bin at the local coffee shop.
Maryke Steffens, reporter: You didn't pick through the bin, did you?
Tony Flynn: No, they set them aside for me!
Maryke Steffens, reporter: What do you reckon?
Tony Flynn: Looks good. See how it clings together?
Maryke Steffens, reporter: Looks good?
Tony Flynn: Yep, looks good.
Maryke Steffens, reporter: Done! Leave it in the sun to dry.
Narration: The next step... after I clean up... is to collect fuel to fire the filter.
...and Fuel proved to be a Tony's biggest - and unexpected - obstacle.
Clay is normally fired in a kiln, fuelled by firewood... but Tony realised that wood can be as scarce as safe drinking water.
Tony Flynn: My problem was finding a fuel that was readily available, efficient and wouldn't use an already scarce resource.
Narration: Tony was stumped... until one day... he stepped right in a good idea.
Maryke Steffens, reporter: Cow poo?
Tony Flynn: Yes, cow manure.
Narration: Tony knew that a dung fire burnt at around 950 degrees C - just the right temperature for firing clay.
Tony Flynn: All we need is... a compliant cow and a match and you're in business.
Narration: So, after an hour or so of baking in the dung...
Maryke Steffens, reporter: A work of art!
Narration: But we still don't know how good are these filters really are when it comes to the ultimate test: removing bacteria from water.
To prove that his idea worked, Tony made a third batch of filters...
... and ran water spiked with E. coli through each of them.
And when the lab tests came back, all of the filters had removed most of the bacteria...
...but the clay and coffee combination worked the best.
Tony Flynn: It removed between 94.6 and 99.8% of e-coli in water. I was amazed, I really didn't know what to expect.
Narration: But will my filter pass the test?
Maryke Steffens, reporter: Right it's the moment of truth, we'll see if this thing actually does what it's supposed to.
Now this is the water that I washed my hands in just before. Tony what's it actually going to filter out?
Tony Flynn: It'll take out any bacteria that were on your hands or in the water, larger clay it will take out but not most of it.
Narration: The clay particles are too small, and so are viruses, which go straight through.
But is this enough?
Tony Flynn: It's not a golden bullet but it's a bullet nevertheless. It will help where there's nothing else available.
Narration: In the hour it takes to filter one litre of water, the coffee-clay filter does remove up to 99.8 percent of bacteria in water.
Maryke Steffens, reporter: Right, just enough for the two of us!
Narration: Tony's final step will be to get his water filter recipe out to communities who can use it...
...and of course raise a glass to everyone who helped along the way.
Maryke Steffens, reporter: Cheers!
Tony Flynn: Good health.
Maryke Steffens, reporter: Cheers girls!
- Reporter: Maryke Steffens
- Producer: Deborah Boerne
- Researcher: Lucy Andrew
PhD Student, Department of Engineering
Australian National University
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