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In 1854, English physician John Snow halted a deadly outbreak of cholera by simply removing the handle from the water pump of the affected London neighborhood. In doing so, he proved that cholera, like many other diseases, is easily transmitted through water sources contaminated with what we now know to be microscopic organisms (bacteria and viruses). Denying the people of Broad Street access to the contaminated water was an eective effective way for Snow to stop the spread of Vibrio cholerae, but such drastic measures are usually not necessary today. Instead, water can be treated to remove the suspended bacteria before it is passed along to the general population. Though there are many dierent ways to build a water treatment plant, most rely on the same general process:
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