MTBE, Well Water and What To Do About This Ground Water Contaminant

Forty years ago, cities around the country began looking for ways to reduce air pollution and smog caused by vehicle traffic. One solution was MTBE, or methyl tertiary butyl ether, a colorless liquid added to gasoline across the country to make the fuel burn more efficiently. While this additive was effective in reducing air pollution, it quickly found its way into water across the region, prompting some states to ban MTBE altogether. MTBE has been found in the ground water of nearly every state and has contaminated about 20% of wells in New England.

MTBE leaked into soil and groundwater in a variety of different ways. Some originated from spills during refueling of cars and lawnmowers, or from fuel spills from boats in lakes and rivers. But the most common was from underground gasoline storage tanks typically found at gas stations. MTBE is highly soluble in water and degrades very slowly, so once it leaked into the soil or water, it was quickly carried throughout the water system.

Contamination of a drinking water supply causes a chemical or “fruity” taste to the water. People say they can detect MTBE and its turpentine-like taste when only a small amount is in a water supply, sometimes as little as 40 parts per billion.

Health effects of MTBE

Some studies on MTBE suggest that high levels of the chemical – far more than a person is likely to ingest – can cause cause stomach irritation, liver and kidney damage, and nervous system effects in animals. An increase in liver and kidney cancer was found in rats and mice that breathed high levels of MTBE or consumed high concentrations of the chemical. Some agencies consider MTBE to be a possible human carcinogen, but the American Cancer Society has not categorized it as a carcinogen and the Environmental Protection Agency has not set a formal health-based standard for MTBE.

What homeowners should know about MTBE

The good news is that today MTBE is rarely used as a gasoline additive, having been replaced largely by ethanol. Some states, like New Hampshire, have even banned MTBE in gasoline sold in the state. If you have MTBE-free well water and do not live near an area where contamination is likely, the chances of future contamination are low.

The bad news is that the MTBE that is already out there is very difficult to remove from water and it can travel quickly through ground water. Fortunately, there are home treatment options that work. If contamination is high, you may need to install a two-step process that removes the bulk of the contaminant in the first filtration step and then “polishes” the water during a second filtration step.

When removing organic contaminants like MTBE, activated carbon is a common water treatment option. Activated carbon has a large surface area, so it is able to remove a significant amount of the contaminant when water is flushed through the system. Once the carbon has filtered to its capacity, it can be refreshed or replaced easily, depending on the system. Some types of activated carbon are now being produced that specifically target MTBE.

Another option is the technique known as “air stripping.” Large amounts of air are injected large into the contaminated water, spraying it into tiny droplets. This vaporizes the contaminants so they are more easily removed. People often like that they don’t have to replace the filtration media with this method. However, it might not be a good choice for homes with high levels of iron and manganese, as it can increase the amount of rust staining on fixtures and laundry. Bacteria have also been known to develop in this type of filter, so it requires regular cleaning or periodic chlorination.

For more information about MTBE contamination in your area, contact the NH DES Oil Remediation and Compliance Bureau at 603-271-3644, the Massachusetts Department of Environmental Protection, or consult with a water system specialist at Skillings & Sons about testing and possible treatment options.