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Rough Science 4 Death Valley: Mike Bullivant's diary: Rover

Updated Tuesday, 29th August 2006

Charcoal and pumping under extreme conditions - Mike Bullivant is back facing some Rough Science.

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Mike filters water Copyrighted  image Icon Copyright: Production team

Day One

Here we go again…. this time with a change to the team. Mikey Leahy’s place has been taken by Iain Stewart (an Earth Scientist) who, even within a few minutes of meeting him, I knew was going to fit in well.

I arrived in LA from Perth (Western Australia) just under a week ago, and three days ago I had to pick the other four scientists and film crew up from Las Vegas where they’d flown to from Heathrow. We’ve all now spent a few days together, and it looks like it’s going to be a good team all-round.

Anyway, it’s the first day of filming, and there’s a lot to do. My challenge for programme one is to purify various samples of ‘impure’ water which Iain and Ellen are to collect from a variety of botanical and geological sources.

Sounds easy enough, but where to start, given the limited resources I have at my disposal? I settle on charcoal (made from burning wood). In fact, I think NASA actually use charcoal filters to purify the air and water systems in their spacecraft.

Charcoal is also used in domestic water filters. I suspect that ordinary charcoal will do, but there’s a chance I can make it an even more effective filter by ‘activating’ it – to do this I’ll need to blow air or ‘superheated’ steam through the hot charcoal, neither of which processes will be easy, or even possible, under Rough Science conditions.

My plan is to pack some two and a half centimetre diameter PVC tubing with plugs of charcoal and trickle the impure water samples (when I eventually get them) down the columns, under gravity. The charcoal is acting as more than just a physical filter to the impurities in the water.

It’s an extremely porous material, containing, as it does, lots of tiny cavities, channels and pores. These all go to increase the material's surface area quite significantly. Incredibly, just one gramme of activated charcoal can have an internal surface area equivalent to five or six tennis courts.

As the impure water works its way down the column, many of the impurities will bind weakly to the charcoal surfaces (a process called adsorption). The slower the trickle, the more efficient the purification process. The purified water should pass through unhindered, for collection at the bottom of the column.

Today’s goal will therefore be to make some charcoal.

Day Two

By the end of day two I’ve managed to show that you can remove the dyes from different food colourings using this process and these adsorbents, so I’m confident it’ll work when I come to purify Ellen’s and Iain’s water samples.

Only problem is that they’ve not been very successful in collecting any samples at all so far. Looks like it’s going to be a last-minute rush to get my part of the challenge completed, which is often the case when you’re relying on someone else to provide the raw materials for your contribution.

Guess I’ll just have to sit it out and wait… There's little else I can do.

Day Three

I’m all ready to go, having packed four columns with charcoal ready to take the different water samples – when Iain and Ellen arrive with their water samples!

But I have only a few hours in which to clean the samples up, and this process, I know, is going to take time. They have to percolate down the columns slowly in order for the separation of impurities to take place.

By 4 pm it’s clear that I’m not going to do it. This just isn’t going to work. In desperation, I try forcing the liquids down the columns under pressure in order to get at least something out at the bottom that we can blind test. In the circumstances, I'm just going to have to do the best I can in the short time available

(Producer's note: In the programme there wasn’t time to show the clever pumping system that Mike used to force water through the columns.)

In the end, things work out better than I expected. Most of the dirty water samples have been cleaned up quite dramatically, but only one – the solar still water - passes Iain's blind-tasting test. It would have worked much better if I’d had more time to work on them. Not a good start to the series, but then again, not entirely a total failure either.





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