Clean Up and Treatment
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Cleaning Up MTBE
Can we clean up releases of MTBE in soil and water?
Although often difficult and time consuming, MTBE contamination can be cleaned up (EPA 510-F-97-015, January 1998) in the soil and water using existing technologies such as air stripping, granular activated carbon (GAC), advanced oxidation, and soil vapor extraction (SVE). These technologies are discussed below. The latter three have been used successfully at individual homes with impacted drinking water wells. Some home treatment units can also remove MTBE in tap water. You can obtain a list of home treatment units that are certified by a non-profit agency, The National Sanitation Foundation. The EPA does not certify home treatment units since it only regulates public water supplies.
When soil is contaminated with MTBE, treatment may be even easier than for other gasoline compounds since pure MTBE has a high vapor pressure and does not sorb ("stick") easily to organic carbon in soil. When MTBE is dissolved in water, MTBE treatment may be more difficult and time consuming than for other gasoline compounds.
The levels to which contaminated ground water is cleaned up can vary as well as the methods used. If the ground water is used for drinking, it is often times treated more rigorously to avoid unpleasant tase and odor and to protect against potential health effects, thereby restoring it to potable condition.
Although MTBE does not readily degrade in soil and water under most natural conditions, some laboratory and field studies have shown promising results using bacterial cultures to degrade the MTBE.
How are the technologies used to remove MTBE from soil and/or water?
SVE technology pulls air through the soil to volatilize (vaporize) contaminants. MTBE vapors that are extracted or vacuumed from the soil must be collected, properly treated, and disposed of to prevent further contamination.
GAC treatment technique pumps contaminated water through a bed of activated carbon to remove organic compounds. Since MTBE does not sorb ("stick") well to organics such as carbon, high volumes of the contaminated water must repeatedly pass through a GAC system before MTBE is effectively removed. Though less effective for MTBE, many individual homeowners use small carbon canisters to remove a variety of contaminants, including MTBE, from impacted private wells.
Air stripping is a process in which contaminated water is passed through a column filled with packing material while upward-flowing air removes chemicals from the water. In general, these vapors should not be released directly into the air and therefore, should be appropriately treated. MTBE does not readily separate from water into the vapor phase, often necessitating high air to water ratios.
Activated oxidation technologies use appropriate combinations of ultraviolet light, chemical oxidants, and catalysts to transform contaminants. Oxidation technologies have been demonstrated to oxidize a wide range of organic chemicals, including MTBE.
Is it expensive to clean up MTBE?
MTBE can complicate remedial activities because of its greater water solubility and resistance to natural biodegradation. Thus, the costs can be higher than those associated with the treatment/remediation (EPA 510-F-97-015, January 1998) for benzene or other gasoline components.
You can access additional documents on how MTBE-contaminated soil and ground water can be cleaned up from the Office of Underground Storage Tanks Web site.