Water enters the LifeStraw apparatus (bottom of picture), hollow fibers trap pathogens while clean water passes through (see inset), and filtered water is sucked up by the user at the top.

Image courtesy Vestergaard Frandsen

LifeStraw Technology

LifeStraw is a tube about 9.25 inches (23.5 centimeters) long and about an inch (2.5 centimeters) around [source: Wilhelm]. The outer shell of the unit is made of a durable plastic, with a string attached so users can wear it around their necks. To use it, a person simply sticks the LifeStraw directly into the water source and drinks as he or she would from a straw.

The first iteration of LifeStraw used iodine to kill bacteria, but the 2012 version contains no chemicals. Instead, the product incorporates mechanical filtration. When you suck on your LifeStraw, water is forced through hollow fibers, which contain pores less than 0.2 microns across -- thus, a microfiltration device. Any dirt, bacteria or parasites are trapped in the fibers, while the clean water passes through. When you're done drinking, you simply blow air out the straw to clear the filter. You can down a quart of water in eight minutes using the LifeStraw.

Vestergaard Frandsen says a personal LifeStraw unit should be able to purify about 1,000 liters (264 gallons) of water -- 2.7 liters (0.7 gallons) a day -- meaning that it will last a year before it needs to be replaced. There are no replacement parts; users must get a new unit each year.

LifeStraw Family is a larger unit that can purify enough water for several people at once. This higher-capacity product can handle a family of five for three years, or roughly 18,000 liters (4,755 gallons), according to the company. The product consists of a blue bucket with a prefilter insert, a long plastic tube and a filter cartridge with a tap attached to draw out the water. No electricity or battery power is required. Gravity guides water through a series of filters. The user pours water into the prefilter and bucket at the top of the unit. The water then moves down the tube and runs through the same type of hollow fiber technology that the personal LifeStraw uses, but these pores are actually 0.02 microns across, which makes it an ultrafiltration device. (It also means the family unit can filter out viruses, while the personal one can't.) The user can then pour the newly purified water from the tap. The person can clean the filter by closing the tap and pressing a red squeeze bulb to release the collected residue and can use a rag to wipe the prefilter bucket. LifeStraw Family can filter about 9-12 liters (2.4 to 3.2 gallons) of water per hour [source: Wilhelm].

On the next page, we'll look at what LifeStraw can and can't do.