Name: William Loehr
* Position: Economist
My consulting work takes me to many rural areas and developing countries--such as Nepal, Egypt, Macedonia and Poland--where water supplies are not always dependable. I carry with me a small water filter, capable of removing organic substances from 100 liters of water before needing to be cleaned. These filters help ensure a healthy visit under the most primitive conditions.
Other filters can clean hundreds of liters depending on how much suspended matter the water has in it. While the filters can remove almost all organic material (such as the parasite giardia, a real stomach troublemaker), they cannot remove all chemicals. There are add-on filters that remove many chemicals, but even without those, the regular filters make the water as safe as most drinking water in the United States. Filters with pores as small as 0.2 micron are probably good enough, but there are filters with even smaller pores.
I use Katadyn's Minifilter model, which is seven inches long and weighs 8.2 ounces. With periodic cleaning, it will filter 2,000 gallons of water. Katadyn makes larger filters, one of which has 0.2-micron pores and cleans up to 13,000 gallons. Other filters are made by First Need and Pur, to name just a few. They are available from specialty backpacking stores; I bought mine through the Recreational Equipment Inc. catalogue based in Seattle.