title: Remediation of groundwater contaminated with MTBE and benzene: the potential of vertical-flow soil filter systems.
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.
authors.affiliation: Centre for Environmental Biotechnology (UBZ), UFZ-Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318 Leipzig, Germany. manfred.afferden@ufz.de
authors.forename: Manfred
authors.initials: M
authors.lastname: van Afferden
authors.forename: Khaja Z
authors.initials: KZ
authors.lastname: Rahman
authors.forename: Peter
authors.initials: P
authors.lastname: Mosig
authors.forename: Cecilia
authors.initials: C
authors.lastname: De Biase
authors.forename: Martin
authors.initials: M
authors.lastname: Thullner
authors.forename: Sascha E
authors.initials: SE
authors.lastname: Oswald
authors.forename: Roland A
authors.initials: RA
authors.lastname: Müller
mesh_terms: D001554:Benzene / Q000302:isolation & purification*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005374:Filtration / Q000379:methods*; D008738:Methyl Ethers / Q000302:isolation & purification*; D012987:Soil; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D008738:Methyl Ethers; D012987:Soil; D014874:Water Pollutants, Chemical; C043243:methyl tert-butyl ether; D001554:Benzene