Here's the abstract from PLOS One:
Effective point-of-use devices for providing safe drinking water are urgently needed to reduce the global burden of waterborne disease. Here we show that plant xylem from the sapwood of coniferous trees – a readily available, inexpensive, biodegradable, and disposable material – can remove bacteria from water by simple pressure-driven filtration. Approximately 3 cm3 of sapwood can filter water at the rate of several liters per day, sufficient to meet the clean drinking water needs of one person.And some relevant results and discussion:
As a model bacterium, we used fluorescently labeled and inactivated Escherichia coli bacteria that are cylindrical in shape with a diameter of ~1 µm. Use of fluorescently labeled bacteria enabled easy enumeration of their concentrations, and also allowed us to track the location in the xylem filter where they were trapped. Since filtration is dominated by size-exclusion at this length scale, we do not expect modification with the dye to significantly affect filtration characteristics. Filtration using three different xylem filters showed nearly complete rejection of the bacteria. Using a hemacytometer to count the bacteria, we estimate that the rejection was at least 99.9%...
Further investigation by SEM clearly showed individual bacterial cells accumulated on the pit membranes over the porous margo. These results confirm the pit membranes as the functional units that provide the filtration effect in the xylem filter...
...the pressures of 1–5 psi used here are easily achievable using a gravitational pressure head of 0.7–3.5 m, implying that no pumps are necessary for filtration...
The simple construction of xylem filters, combined with their fabrication from an inexpensive, biodegradable, and disposable material suggests that further research and development of xylem filters could potentially lead to their widespread use and greatly reduce the incidence of waterborne infectious disease in the world.
What a blessing that would be! A friend of mine, with her church women's group, adopted a home for girls in Kenya. The girls have all been saved from abusive situations, or from being sold into marriage as children. They have a nice facility, but each girl has approximately one pint of clean water a day. That's hard for spoiled Americans to imagine. We waste so much clean water! We have so much, we don't appreciate it. I can't even imagine having only two cups of clean water a day.
ReplyDeletedoesn't make nearly as much sense as using the local potters to make ceramic filters. How much wood do you suppose there is in those areas? The ceramic filters last years, remove most pollutants and can be cleaned.
ReplyDeleteBarbwire, get your Kenyan contact to look into the many groups producing local ceramic filters, or one that can teach the school how to make them as a business venture. Googling brought up even more than I knew about. They are effective, create local business, and clean water for years per vessel.
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