Filtros Bio-arena

I am now a full day into my third week here in San Juan del Sur. Week one was a whirl of activities, since it was spring break for many universities in the US, which meant many “Alternative Spring Break” groups here to volunteer. Week two was a bit of an awakening; I realized that I would be here through July, which itself is a long ways away. Several feelings have set in at this point: one is a feeling of purpose since I came here to achieve a goal (and learn about myself and this new country, city, people, etc.), another is a feeling of frustration due to the language barrier that is making ten minute conversations into hour long ones and forcing me to designate larger and larger portions of the day to simply talking with people. The last feeling will take a bit longer to settle in my gut, but it is a sense of routine that underlies my ability to call this place home for the next little while. I’ve joined a gym (yes, San Juan del Sur has a gym, but it reminds me of what inmates must use in prison—concrete walls and floors with second or third hand equipment), I’ve been jogging in the morning, and most importantly, I formulating how the next few weeks and then how the next few months will look.

As a precursor of blog entries to come, initially, I am going to head to each of the communities in “El Campo” (about which I’ve written before) which have biosand filters and testing the filters’ abilities to purify water, their use and incorporation in the daily lives of community members, and survey the families about their health and about their filters. Since the filters were installed, it seems that there is no pulse on whether or not they are doing was they are supposed to, so this needed step could really be an eye-opener.

Very quickly, it’s worth explaining a little about the filter technology: slow sand filtration has been around for a while. In the mid 1990s, a researcher in Canada (who ever said they weren’t good for anything?) developed a new way to build these filters such that after about three weeks of proper use, a bio-layer forms in the top 2 or so centimeters of sand on the filter. This “schmutzdecke” (literally “dirt layer”) contains organisms which add another tool to the filter’s arsenal against parasites and contaminants. Sand by itself can filter water by two methods, both of which are mechanical: straining and adsorption. Straining is easily understood: think finished pot of pasta in the strainer. Adsorption is when contaminants are trapped in the small holes and pores on the surface of the sand grains themselves. The final element (or rather the first element) is the predatory capabilities of organisms in the biological layer; the algae, bacteria, and zooplankton that live there hunt and kill the pathogens in the raw water. However, since this “schmutzdecke” is living, it needs the same things that most other living things need: love (well, proper maintenance) and oxygen. This means that there must always remain 5 centimeters of water above the sand. That’s pretty much it. The nice things about the biosand filter are essentially threefold:
1) The materials (concrete, sand, and PVC piping) can all be found locally, in country—no special technology needed.
2) Very little maintenance is required, only a little stir in the “schmutzdecke” every few months or so. No new parts needed…ever.
3) The flow rate is great: about 1 liter every two minutes, which means that it is almost like running water when you pour dirty water in the top.
The drawbacks are that the filtration capabilities are not 100%. One study pinned the filtration at 98.5% (that is: number of E. coli colonies before minus number of E. coli counts after divided by number of E. coli counts before), which ain’t bad, but it doesn’t look like ours are at that point.

So there you have it. Biosand Filters. Filtros Bio-arena.