Print Email Facebook Twitter Modeling biogeochemical processes and isotope fractionation of enhanced in situ biodenitrification in a fractured aquifer Title Modeling biogeochemical processes and isotope fractionation of enhanced in situ biodenitrification in a fractured aquifer Author Rodríguez-Escales, Paula Folch, Albert Vidal-Gavilan, Georgina van Breukelen, B.M. (TU Delft Sanitary Engineering) Date 2016-01-28 Abstract Enhanced in situ biodenitrification (EIB) is a feasible technology to clean nitrate-polluted groundwater and reachdrinking water standards. Aimed at enabling a better monitoring and management of the technology at the fieldscale, we developed a two-dimensional reactive transport model (RTM) of a cross section (26.5 × 4 m) of a fracturedaquifer composed of marls involving both biogeochemical processes and associated isotope fractionation.The RTM was based on the upscaling of a previously developed batch-scale model and on a flow model that wasconstructed and calibrated on in situ pumping and tracer tests. The RTM was validated using the experimentaldata provided by Vidal-Gavilan et al. (2013). The model considers several processes including (i) exogenous andendogenousmicrobial nitrate and sulfate respiration coupled to ethanol oxidation and linked tomicrobial growthand decay, and (ii) geochemical interactions (dissolution/precipitation of calcite), and (iii) isotopic fractionationof the reaction network (15N–NO3, 18O–NO3, 13C–DIC, 13C–ethanol, 13C–biomass, and 13C–calcite). Most of thecalibrated microbiological parameter values at field scale did not change more than one order of magnitudefrom those obtained at batch scale, which indicates that parameters determined at the batch scale can be used as initial estimates to reproduce field observations provided that groundwater flow is well known. In contrast, the calcite precipitation rate constant increased significantly (fifty times)with respect to batch scale. The incorporation of isotope fractionation into the model allowed to confirm the overall consistency of the model and to test the practical usefulness of assessing the efficiency of EIB through the Rayleigh equation approach. The large underestimation of the Rayleigh equation of the extent of EIB (from 10 to 50%) was caused by the high value of hydrodynamic dispersion observed in this fractured aquifer together with the high reaction rates. Subject DenitrificationGroundwaterCalcite precipitationReactive transport modelingUp-scaling To reference this document use: http://resolver.tudelft.nl/uuid:6299bc99-a1ca-408a-b3d6-a3819f0029df DOI https://doi.org/10.1016/j.chemgeo.2016.01.019 Embargo date 2018-02-01 ISSN 0009-2541 Source Chemical Geology, 425 (May), 52-64 Part of collection Institutional Repository Document type journal article Rights © 2016 Paula Rodríguez-Escales, Albert Folch, Georgina Vidal-Gavilan, B.M. van Breukelen Files PDF CHEMGE8711R3_accepted.pdf 2.7 MB Close viewer /islandora/object/uuid:6299bc99-a1ca-408a-b3d6-a3819f0029df/datastream/OBJ/view