Three years ago I wrote an blog based on my research around water and making it clean. Coming up in the next several days are a few follow ups on that idea, followed by my first solo attempt at building a cheap filter.
If you've been keeping up with me, I'm in Eastern Africa these days. Mostly spending my time in Uganda, but right now my brother is back in Burundi for the elections, so joined him as a technical consultant working on SMS stuff. I have gotten side tracked by water as a CAWST is training people to build a BioSand Filter in 3 locations in Burundi (associated with the Quaker church). Prior to coming down to Burundi I also met a fascinating guy in Uganda who's an electrical engineer and programmer who's house has, a house water catchment system, 5 level filters, multiple solar panels that run a whole house inverter, two internet connections, a boat with it's own set of solar outfitting, and out paces my hard drive storage capability (a feat I rarely see while traveling here).
Needless to say I've learned a bit from three years ago. I have a few thoughts to add about water and making it clean, with the added slant of think about low cost, simple, very user-friendly, locally built, technologies for the developing world which (hopefully) can be income generating.
I'll mention a bit about the tech I witnessed during the BioFilter training, then talk about some of the other problems and solutions I've found and considered, an then talk a bit about the reason I'm an "appropriate technology" fiend now.
The Center for Affordable Water and Sanitation Technology (CWAST) is a Canadian NGO that focus on the impacts of water on life. There hallmark is a device called a BioSand Filter, which was created by a Canadian Doctor in the 1990s. Since it was developed, it's gone through 10 revisions and it's a open patent and they use CreativeCommons for documentation. It's now a 120 pound concrete pedestal that uses a combination of biological predation, natural death, mechanical trapping, and adsorption to *Filter* water. I was skeptical when I first heard about it because I was used to a paradim of screening and adsorption via things like Reverse Osmosis, or Carbon based filtration, or clay filtration, etc. This is what you'll see in most modern filtration and purification (the difference being that filters don't remove viral and small bacterial particulates). A BioSand filter has no such items, as the pedestal is more or less filled with two types of larger rocks at the bottom, a bunch of sand above, and a diffuser plate above the standing water (to aerate the water). I was asking myself how this can produce clean water when things like Cryptosporidium, viruses, and cysts can be near .5 microns which even things like Reverse Osmosis don't always stop. The answer is that it plays the small and large waterborne pathogens against each other. The "Bio" portion of the filter is a biologically active layer that allows, nay encourages, these pathogens to eat each other. Like in the ocean, where light doesn't penetrate below a certain depth and things grow differently, the sand naturally layers into a non-biological layer where (with time) the carcases create that smaller and smaller space that physically filters more of the pathogens out and which leaves you with water that is extremely clear and more importantly more or less drinkable.
Now one of the big things I didn't cover in my previous blog post was the notion of the stages from dirty to clean water. Think about as if you were camping or not in an urban environment. To treat the water, you first need to get water that's not apparently coming out of a mine or industrial plant (maybe get the sticks and big stuff out of it), transport it, then you need to remove a majority of the particles (inorganic, organic, metals, and pathogens), but it's not clean as some of the real small stuff can cause problems yet so then you need to disinfect the water before you find a clean place to store it. One useful set of technical terms for this is: Source Protection, Sedimentation, Filtration, Disinfection, and Storage.
What a CAWST BioStand Filter does is specifically to Sediment and Filtrate the water. It's not disinfecting the water, although it will remove between 85% and 100% of Bacteria, Viruses, Protozoa, Helminths, Turbidity (Dirt), and Iron. Not perfect, but an order of magnitude improvement over drinking it straight from a bore hole, river, lake, or tap out here and it's not overly expensive (developmentally speaking). It means you aren't going to get nearly as sick (diarrhea reduces to 10% of previous levels).
That's just the tech. They also do a training on sanitation, including things like germ theory, how to use soap, the important of latrines/toilets, etc. This is both Source Protection (i.e. feces draining into the water supply) and Storage (A clean jerry can stays clean with clean hands, etc). There are methods of disinfecting the water cheaply (Solar Disinfection using natural UV in a P.E.T. bottle, or wrapping bottles in black and leaving them to heat to disinfection levels over hours, or boiling, or if you can get it Chlorine).
I didn't attend the entire training, as (big surprise) I was more interested in the tech. I did however spend a fair amount of time over the last several days reviewing the water info I previously understood and added to it. My point of view has dramatically changed. I am still a clean water nut, but now I want to find an use water tech that is cheap, ubiquitous, and darn simple.
Tomorrow I talk about why that last bit is extremely important to me these days.