MtBE has been detected with increasing frequency in drinking water throughout New Hampshire. Since MtBE is a manmade material, its presence in the water would indicate that manmade contamination exists near or within the recharge area of the well. The chemical has been found in various types of drinking water sources including shallow wells, deep bedrock wells and surface water sources. There may be no apparent source for the contamination. It has been detected in the water of some of the most remote well locations. The source of the contamination frequently is not found.

MtBE degrades very slowly, is highly soluble in water, has a very small molecular structure and very low taste(40ug/L) and odor(20ug/L) thresholds.

MtBE is used to increase the octane rating in gasoline and also to reduce air pollution by increasing the oxygen content. The 1990 Clean Air Act Amendment prompted an increase in the level of MtBE in gasoline within the New England area. That level is currently 11 percent.

Although the U.S. EPA has not set a formal "health based" drinking water standard for MtBE, The NH Dept. of Health and Human Services, Bureau of Health Risk Assessment(BHRA) has recently developed a "health based" drinking water standard for MtBE of 13 micrograms per liter(ug/L) for community public water systems.

Live animal studies suggest that drinking water with high levels of MtBE may cause stomach irritation, liver and kidney damage, and effects on the nervous system. An increased amount of liver and kidney cancer was found in rats and mice after breathing high levels of MtBE. Based upon those studies, the BHRA now considers MtBE a possible human carcinogen.

The EPA's public water supply program has recently made a "non-health based" recommendation limiting MtBE in drinking water to 20-40 ug/L which is primarily based on preventing taste and odor complaints.

Unlike many other VOC's, MtBE is not easily removed from water. The two most widely used methods are Aeration and Carbon Adsorption.

It is the opinion of many qualified water treatment professionals, that when dealing with the removal of health related contaminants like VOC's, both methods should be used in series to create redundancy.

First, an appropriately sized aeration system should be installed to oxidize and safely vent out any volatile gasses, then, follow it with an appropriately sized carbon adsoption tank that is loaded with enough activated carbon to act as a second line of defense, "polishing" the water and catching anything that may not have been effectively removed by the aeration system. The first stage aeration system will also help to keep the second stage carbon adsorption system free from collecting and storing any potential waterborne radon and radon decay products that may cause possible increased radiation in the home and create a low level radionuclide waste problem.

The EPA recommends that before a treatment system is purchased, sufficient water quality testing should be done to identify the following:

1) The short term variability of the contaminant(s).

2) Whether the contaminant concentrations are rising or falling over the long term.

3) What other contaminants are in your general area and how many are predicted to affect your well in the future.

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