1 . Astronauts drink their own pee (尿)—after it's been cleaned.     1     Many experts, though, argue that recycling pee and other waste is an excellent and safe solution when there isn't enough fresh water to go around.

    2     All of the water that astronauts use to drink, brush their teeth, or make coffee comes out of one limited container that has to be resupplied—from Earth. To help conserve water, the waste from sinks, toilets, and even the pee from lab animals on board flows into a recycling system. First, the water goes through a series of filters(过滤器) to get rid of large particles(微粒) and impurities. Then, chemical reactions remove poisonous chemicals and kill any bacteria or viruses.     3    

Chris Hadfield, who lived on the space station for five months, says, "Before you feel uncomfortable with the thought of drinking your leftover wash water and your leftover pee, keep in mind that the water that we end up with is purer than most of the water that you drink on a daily basis at home."

Astronauts, however, tend to be more adventurous than the average person. On Earth, cities in very dry parts of the world have attempted to introduce wastewater purification systems.     4     Citizens recoiled(退缩) in disgust. Despite scientific evidence that the water is clean, many people just can't get over the fact that it once flowed through a toilet. In the 1990s, activists in San Diego and Los Angeles campaigned against "toilet to tap" water.     5     In a survey of 2,000 Americans, 26 percent agreed with the statement: "It is impossible for recycled water to be treated to a high enough quality that I would want to use it."