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Superfund Innovative Technology Evaluation
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Site Technology Capsule, EcoMat Inc.'s Biological Denitrification Process
EPA/540/R-01/501a
2003
EcoMat, Inc. of Hayward, California (EcoMat) has developed an ex situ
anoxic biofilter biodenitrification (BDN) process. The process uses
specific biocarriers and bacteria to treat nitrate-contaminated water
and employs a patented reactor that retains biocarrier within the system,
thus minimizing solids carryover. Methanol is added to the system as
a carbon source for cell growth and for inducing metabolic processes
that remove free oxygen and encourages the bacteria to consume nitrate.
Methanol is also important to assure that the nitrate conversion results
in the production of nitrogen gas rather than the intermediate (and
more toxic) nitrite. EcoMat's BDN and post-treatment systems were evaluated
under the SITE Program at a former public water supply well in Bendena,
Kansas. Nitrate concentrations in the well groundwater have historically
been measured from approximately 20 to 130 ppm, well above the regulatory
limit of 10 mg/l. Low concentrations of VOCs, particularly carbon tetrachloride
(CCl4), are a secondary problem. The overall goal of EcoMat (the developer)
was to demonstrate the ability of their process to reduce the levels
of nitrate in the groundwater and restore the well as a drinking water
source. The SITE demonstration occurred between May and December of
1999 and was conducted in cooperation with the Kansas Department of
Health and Environment (KDHE). The study consisted of four separate
sampling events over 71/2 months. During these events EcoMat operated
their system to flow between three and eight gallons per minute. During
that same time period nitrate-Nitrogen (nitrate-N) concentrations in
the well water varied from greater than 70 mg/l to approximately 30
mg/l. Since the post-treatment system implemented by EcoMat varied for
each of the four events, data from the four events were analyzed separately.
Formal statistical analyses were used to address specific test objectives
using a significance level of 0.10. Events 1 and 2 were found to be
successful in meeting performance goals for significantly reducing levels
of nitrate-N and nitrite-N after BDN and after post treatment. Events
3 and 4 were not shown to be successful in significantly reducing levels
of nitrate-N and nitrite-N after BDN and after post treatment. Dissolved
oxygen (DO) measurements indicated that the deoxygenating step of EcoMat's
BDN process was not optimized throughout the demonstration. The desired
DO levels of < 1 mg/l following the deoxygenating step in the process
were measured only during the first two events. The effectiveness of
the post-treatment systems was variable for different parameters. None
of the post treatment system combinations used during the demonstration
was effective in removing residual methanol to the demonstration objective
of < 1 mg/l. However, the increased level of filtration incorporated
following the first two events appear to have had a substantial beneficial
impact on solids carryover.
Contact:
Randy Parker
parker.randy@epa.gov
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