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Jonathan Greene,
PE, ThermoRetec Houston
Tim Barnhill, ThermoRetec Houston
Overview:
According to
a U.S. Geological Survey, approximately 42 million people use
water from their own private water supplies. Although the EPA
does not certify the effectiveness of home treatments, some of
the technologies available for MTBE remediation have proven to
be efficient and cost-effective for the small drinking water
flows (2-10 gpm) in private households. These include: air
stripping and granular activated carbon (GAC) adsorption. Most
processes are capable of reducing MTBE concentrations to less
than 5 ug/L, well below the national advisory concentration of
20-40 ug/L.
Treatment
Levels:
The EPA’s
public water supply program has recommended that MTBE be
limited to 20-40 ug/L. This is based on taste and odor
complaints. However, some states have regulated concentrations
ranging from 5 ug/L (California), 40 ug/L (Rhode Island,
Vermont, Missouri), 70 ug/L (Massachusetts, New Jersey), to
200 ug/L (Wyoming, North Carolina).
Proven
Technologies:
-
Air stripping is a technology that has
proven to productively remove MTBE from municipal and
private household drinking water. An air stripper consist of
contaminated water flowing down a column filled with packed
material while a stream of air flowing upward strips the
MTBE from the water. Some air stripping specific system
technologies consist of spray towers, bubble diffusion
strippers, aspirated air strippers, low profile air
strippers, and packed towers. Low profile air strippers show
to be the most cost effective at lower flow rates cleaning
at a rate of 97.5% removal of MTBE. Low profile air is easy
to maintain, install, modify flow rates, and modify water
quality conditions. This technology will usually cost more
than GAC units do to its need for operation and maintenance.
-
Granular activated carbon (GAC)
adsorption is a technology most widely being used to remove
different types of organic compounds such as MTBE from
private household water systems. This method involves
pumping water through a bed or canister of activated carbon,
which causes the MTBE to be absorbed. Many of the canisters
that house the GAC filtering system can be purchased in an
array of different shapes and sizes. The two types of
carbon being used are coconut-shell carbon and coal-based
carbon. In some cases coconut-shell carbon has proven to be
the most effective carbon, however, both are capable of
removing MTBE to non-detectable levels. In certain test, the
coconut-shell activated carbon is able to last longer and
absorbs a greater capacity of MTBE than coal-based carbon.
Both have better efficiency and effectiveness when the
levels of MTBE are below 300 ug/L. Some home units even have
up to 6-year warranties that require little or no care.
Conclusion:
With all the
attention that MTBE is getting now days, it is easy to forget
about the actual problem that has put MTBE and other gasoline
contaminants on the forefront. It’s easy to look at certain
gasoline chemicals and realize how harmful they can be to
humans. The fact is, these chemicals were never intended to
reach water supplies at any harmful levels. The key issue to
stopping the continuation of water contamination is to not
allow it to get in the ground in the first place. Until there
are not anymore gasoline spills, leaking underground or
aboveground gasoline storage tanks, excessive use of
watercrafts etc.., this problem will exist. Fortunately, with
the uses of low profile air strippers and granular activated
carbon in private homes, owners can efficiently and
cost-effectively clean the water they drink.
Reference:
Environmental
Fact Sheet WD-WSEB-3-19, 2000. MTBE in Drinking Water,
New Hampshire Department of Environmental Services.
Hoerner,
David J. and Mark R. Stouffer, 2000. MTBE solution in a
nutshell.
website
Website. -
Clean Air & Clean Water, The Facts on Managing MTBE-Blended
Gasoline Releases to Water Supplies.
Website
- MTBE Water
Contamination: About MTBE, Lewis Saul & Associates,
P.C.
Website-Water
Quality with Laura E. Loverde, Solving the MTBE Problem.
http://www.wholly-water.com/technology.htm
National
Ground Water Association: Press Release, 2000. NGWA
Supports Phaseout of MTBE. Westerville, OH.
Oxygenated
Fuels Association, 1999. MTBE: Treatability and Remediation.
Arlington, Virginia. April.
Schrader
Environmental Systems.
website
The
California MTBE Research Partnership, 2000. Executive
Summary- Treatment Technologies for Removal of Methyl Tertiary
Butyl Ether (MTBE) from Drinking Water: Air Stripping,
Advanced Oxidation Processes, Granular Activated Carbon,
Synthetic Resin Sorbents, 2nd ed. National Water Research
Institute, Fountain Valley, CA.
U.S.
Environmental Protection Agency, 1998. MTBE Fact Sheet #2,
Remediation Of MTBE Contaminated Soil And Groundwater.
Office of Solid Waste and Emergency Response. January.
U.S.
Environmental Protection Agency, 2000. Private Drinking Water
Wells. Office of Water.
www.epa.gov/safewater/pwells1.html
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