Cory Doctorow at 6:00 am Sat, May 11, 2013
Gmoke sez, "Susan Murcott and her team's factory making clay filters for Pure Home Water in Ghana. Over 100,000 served, so far."
They're shooting for 1,000,000.
Pure Home Water, Ghana: AfriClay Filters
People making and selling real comma useful things. How many of us are doing that?
(My ”””name””’ is name of UK water company, imaginatively spaced. Apt. huh?
Good questions. Anyway, my hats off to these guys doing it, making something happen. It shows someone is. Which I sometimes forget.
Civ III music.
I wonder how it compares to this infographic I see floated around:
I think it’s the same idea just implemented slightly differently. All these filters use the small pore size of ceramics to filter out dirt and bacteria. This massively improves the water quality but won’t get rid of harmful chemicals (so don’t use the water downstream of the illegal mining operation…) or viruses. This filter plus boiling should give completely safe water.
I see just one problem with this kind of filter: it needs pretty good pre-filtering and thorough cleaning after a few usages. These are are very much like Katadyn’s and other ceramic-based gravity filters, but using the clay mould instead of the ceramic “candles”.
Back in 2005, I shortly worked with a Canadian who tested a filter design in his master thesis for its application in the humid tropics. (Vivek, if you read this: how’s life going?) He used in-the-field test kits to determine water quality, and additionaly counted microbe colonies growing on 3M petri-films after inoculation.
It was a community filter, larger than these home-scale filters. You needed a mould to produce a large concrete tube, closed at the bottom, as I seem to remember. It hat a kind of tube connector, I think, not unlike a tab. However, I think it was meant to have constant throughput, so no way to close the tab.
You started filling the concrete basin with different kinds of locally available material, carefully selected and stacked. The water was flowing though rough gravel, finer gravel, small pepples, and then sand (different grain sizes, if available). I don’t remember exactly how they were stacked (i.e., if you repeat the stacking), but I think it would be sensible to do so. The point is to get out the suspended solids, and at the same time have a very large surface for microbes to settle. Like this, the whole thing would work just like an oversized aquarium filter, also de-nitrifying water, and even breaking down a lot of potentially harmful organic compounds.
Downsides were a) the metal mould you needed to produce the concrete tube, which was hard to construct (and unaffordable for the local communites), b) the fact that you needed constant very slow waterflow to keep the microbial community in the filter stable and c) that you needed to re-establish the whole thing again every now and then, when the filter developed a dead zone which was to large for the system to still work properly.
However, his tests showed you could drink the water right out of the thing. His project lasted for more than four months during the rainy season, when you normally had cholera outbreaks.
Adding the clay filter presented in the video above would even improve the quality, because you would get rid of the rest of microbes and very fine particles. However, clay would have been be hard to come by in the area, and plastic containers like the ones presented were unaffordable and even more difficult to come by (in 2005).
Later, I have seen how people not treat their water in West Africa. Ghana is comparably well developed, I wonder how much cedi they charge for the filter (and how much would that be in FCFA)? Is the project a real success? If anyone involved drops by: please leave a note.
It would be hard to maintain biofilm filters over the long haul. The clay would probably also be good at catching the nasty tropical parasites, which can be horrendous.
@boingboing-e41803c944b3d68e5215c8b9cefb0196:disqus , the filters have to be mainted continuoisly, and overhauled every four to 12 months, depending on solid load. Which is no problem, as all the material needed is available locally.
Try it out your aquarium filter, if you like. The main trouble is organic solids, and you can get rid of that by pre-filtering trough a bucket of gavel which you clean every now and then.
By the way, friends of mine are developing a biofilter system for denitrifying human waste products. Guess for which application?
(Hint: no spare material easily available, must work on the long haul.)
Re:parasites – worm eggs, e.g., were not found in the filtered samples in 2005/2006 (I, on the other hand, brought home Ascaris as well as Trichuris, as I could not tread water in the field all of the time.)
However, I agree that the clay filters would further improve the process. Sadly, they also need a lot of maintenance.
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