Remediation of groundwater contaminated with MTBE and benzene: the potential of vertical-flow soil filter systems |
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Authors: | van Afferden Manfred Rahman Khaja Z Mosig Peter De Biase Cecilia Thullner Martin Oswald Sascha E Müller Roland A |
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Affiliation: | a Centre for Environmental Biotechnology (UBZ), UFZ-Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany b Department of Environmental Microbiology, UFZ-Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany c Institute for Earth and Environmental Sciences, University of Potsdam, Potsdam, Germany |
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Abstract: | Field investigations on the treatment of MTBE and benzene from contaminated groundwater in pilot or full-scale constructed wetlands are lacking hugely. The aim of this study was to develop a biological treatment technology that can be operated in an economic, reliable and robust mode over a long period of time. Two pilot-scale vertical-flow soil filter eco-technologies, a roughing filter (RF) and a polishing filter (PF) with plants (willows), were operated independently in a single-stage configuration and coupled together in a multi-stage (RF + PF) configuration to investigate the MTBE and benzene removal performances. Both filters were loaded with groundwater from a refinery site contaminated with MTBE and benzene as the main contaminants, with a mean concentration of 2970 ± 816 and 13,966 ± 1998 μg L−1, respectively. Four different hydraulic loading rates (HLRs) with a stepwise increment of 60, 120, 240 and 480 L m−2 d−1 were applied over a period of 388 days in the single-stage operation. At the highest HLR of 480 L m−2 d−1, the mean concentrations of MTBE and benzene were found to be 550 ± 133 and 65 ± 123 μg L−1 in the effluent of the RF. In the effluent of the PF system, respective mean MTBE and benzene concentrations of 49 ± 77 and 0.5 ± 0.2 μg L−1 were obtained, which were well below the relevant MTBE and benzene limit values of 200 and 1 μg L−1 for drinking water quality. But a dynamic fluctuation in the effluent MTBE concentration showed a lack of stability in regards to the increase in the measured values by nearly 10%, which were higher than the limit value. Therefore, both (RF + PF) filters were combined in a multi-stage configuration and the combined system proved to be more stable and effective with a highly efficient reduction of the MTBE and benzene concentrations in the effluent. Nearly 70% of MTBE and 98% of benzene were eliminated from the influent groundwater by the first vertical filter (RF) and the remaining amount was almost completely diminished (∼100% reduction) after passing through the second filter (PF), with a mean MTBE and benzene concentration of 5 ± 10 and 0.6 ± 0.2 μg L−1 in the final effluent. The emission rate of volatile organic compounds mass into the air from the systems was less than 1% of the inflow mass loading rate. The results obtained in this study not only demonstrate the feasibility of vertical-flow soil filter systems for treating groundwater contaminated with MTBE and benzene, but can also be considered a major step forward towards their application under full-scale conditions for commercial purposes in the oil and gas industries. |
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Keywords: | Benzene Groundwater remediation Hydraulic loading rate MTBE Pilot-scale constructed wetland Vertical-flow soil filter Willow tree |
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