Taco Cowboy writes "Dirty water is a major cause of mortality in the developing world. The most common water-borne pathogens are bacteria (e.g. Escherichia coli, Salmonella typhi, Vibrio cholerae), viruses (e.g. adenoviruses, enteroviruses, hepatitis, rotavirus), and protozoa (e.g. giardia). These pathogens cause child mortality and also contribute to malnutrition and stunted growth of children.
In search of a low-cost and simple solution for filtering dirty water in developing nations, researchers have rediscovered the humble tree. A piece of freshly cut sapwood from pine trees can remove 99% of Escherichia coli bacteria in water.
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.
White pine growing on Massachusetts, USA was used. The pine was identified as pinus strobus based on the 5-fold grouping of its needles, the average needle length of 4.5 inches, and the cone shape.
1 inch-long sections were cut from a branch with approximately 1 cm diameter. The bark and cambium were peeled off, and the piece was mounted at the end of a tube and sealed with epoxy. Approximately 5 mL of deionized water or solution was placed in the tube. Pressure was supplied using a nitrogen tank with a pressure regulator. For filtration experiments, 5 psi (34.5 kPa) pressure was used. The filtrate was collected in glass vials.
For bacteria filtration, the feed solution was prepared by mixing 0.08 mg of inactivated Escherichia coli in 20 mL of deionized water (~1.6×107 mL1) after which the solution was sonicated for 1 min. The concentration of bacteria was measured in the feed solution and filtrate by enumeration with a hemacytometer (inCyto C-chip) mounted on a Nikon TE2000-U inverted epifluorescence microscope. Before measurement of concentration and filtration experiments, the feed solution was sonicated for 1 min and vigorously mixed.
The flow rate was proportional to applied pressure."
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