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Superfund Innovative Technology Evaluation (SITE)

Abstract

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EcoMat Inc. Biological Denitrification Process
Capsule Report
(540/R-01/501A)
Summary (540/MR-01/501)

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 7 1/2 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.

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Randy Parker

 

Risk Mangement Research | Air and Climate Change Research | Water Research | Ecosystems Restoration Research | Land Risk Management Research | Technology: Sustainable Technologies Research, Environmental Technology Verification Program (ETV), and Technology Assessments

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