MTBE dissolves easily in water, and because it is a very small molecule, it moves quickly through soil and groundwater. Unfortunately, it is also difficult to remove during water treatment.
In 1996, the City of Santa Monica, California, learned that much of its drinking water supply was contaminated with MTBE levels as high as 610 parts per billion. In response, the city shut down two of its well fields, which represented 50 percent of the city's drinking water supply, and was then forced to purchase replacement water.
To remove MTBE from contaminated water supplies, public water systems may need to use additional treatment technologies, which can make drinking water more costly. According to the EPA, there are three treatment technologies that are effective in removing MTBE:
Air stripping is a process by which air is forced through contaminated water until MTBE becomes a gas and separates from the water.
Filtration with granular activated carbon causes MTBE to stick to carbon particles, separating MTBE from the water.
Advanced oxidation causes MTBE to react with oxygen, changing it to a form that is less harmful or easier to remove.