Tracing the role of endogenous carbon in denitrification using wine industry by-product as an external electron donor: coupling isotopic tools with mathematical modeling

Nitrate removal through enhanced biological denitrification (EBD), consisting of the inoculation of an external electron donor, is a feasible solution for the recovery of groundwater quality. In this context, liquid waste from wine industries (wine industry by-products, WIB) may be feasible for use as a reactant to enhance heterotrophic denitrification. To address the feasibility of WIB as electron donor to promote denitrification, as well as to evaluate the role of biomass as a secondary organic C source, a flow-through experiment was carried out. Chemical and isotopic characterization was performed and coupled with mathematical modeling. Complete nitrate attenuation with no nitrite accumulation was successfully achieved after 10 days. Four different C/N molar ratios (7.0, 2.0, 1.0 and 0) were tested. Progressive decrease of the C/N ratio reduced the remaining C in the outflow and favored biomass migration, producing significant changes in dispersivity in the reactor, which favored efficient nitrate degradation. The applied mathematical model described the general trends for nitrate, ethanol, dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. This model shows how the biomass present in the system is degraded to dissolved organic C (DOCen) and becomes the main source of DOC for a C/N ratio between 1.0 and 0. The isotopic model developed for organic and inorganic carbon also describes the general trends of d13C of ethanol, DOC and DIC in the outflow water. The study of the evolution of the isotopic fractionation of organic C using a Rayleigh distillation model shows the shift in the organic carbon source from the WIB to the biomass and is in agreement with the isotopic fractionation values used to calibrate the model. Isotopic fractionations (e) of C-ethanol and C-DOCen were -1‰ and -5‰ (model) and -3.3‰ and -4.8‰ (Rayleigh), respectively. In addition, an inverse isotopic fractionation of +10‰ was observed for biomass degradation to DOCen. Overall, WIB can efficiently promote nitrate reduction in EBD treatments. The conceptual model of the organic C cycle and the developed mathematical model accurately described the chemical and isotopic transformations that occur during this induced denitrification.Peer ReviewedPostprint (author's final draft

Determination of the isotopic enrichment factor during denitrification by ethanol

En este estudio se han realizado experimentos de tipo batch para calcular el fraccionamiento isotópico del NO3- durante la desnitrificación que tiene lugar en las aguas subterráneas con contenidos de nitratos superiores a los 240 mg/L en un sitio de la Cuenca del río Matanza-Riachuelo (CMR). En medio anóxico (caja de guantes con una atmósfera de argón), se utilizaron botellas de vidrio que se llenaron con 15 mg de sedimento, 75 mL de agua con un contenido de nitrato de 243 mg/L y se añadió 30 μL de etanol. Los valores isotópicos del NO3- durante el proceso desnitrificante variaron en un rango de +11.20 a +56.50 para δ15N-NO3- y entre +7.05‰ a +65.68‰ para δ18O-NO3-. Los valores del factor de enriquecimiento isotópico obtenidos fueron -27.5‰ para εN y de -33.7‰ para εO.Centro de Investigaciones Geológica

Determination of the isotopic enrichment factor during denitrification by ethanol

En este estudio se han realizado experimentos de tipo batch para calcular el fraccionamiento isotópico del NO3- durante la desnitrificación que tiene lugar en las aguas subterráneas con contenidos de nitratos superiores a los 240 mg/L en un sitio de la Cuenca del río Matanza-Riachuelo (CMR). En medio anóxico (caja de guantes con una atmósfera de argón), se utilizaron botellas de vidrio que se llenaron con 15 mg de sedimento, 75 mL de agua con un contenido de nitrato de 243 mg/L y se añadió 30 μL de etanol. Los valores isotópicos del NO3- durante el proceso desnitrificante variaron en un rango de +11.20 a +56.50 para δ15N-NO3- y entre +7.05‰ a +65.68‰ para δ18O-NO3-. Los valores del factor de enriquecimiento isotópico obtenidos fueron -27.5‰ para εN y de -33.7‰ para εO.Centro de Investigaciones Geológica

Determination of the isotopic enrichment factor during denitrification by ethanol

En este estudio se han realizado experimentos de tipo batch para calcular el fraccionamiento isotópico del NO3- durante la desnitrificación que tiene lugar en las aguas subterráneas con contenidos de nitratos superiores a los 240 mg/L en un sitio de la Cuenca del río Matanza-Riachuelo (CMR). En medio anóxico (caja de guantes con una atmósfera de argón), se utilizaron botellas de vidrio que se llenaron con 15 mg de sedimento, 75 mL de agua con un contenido de nitrato de 243 mg/L y se añadió 30 μL de etanol. Los valores isotópicos del NO3- durante el proceso desnitrificante variaron en un rango de +11.20 a +56.50 para δ15N-NO3- y entre +7.05‰ a +65.68‰ para δ18O-NO3-. Los valores del factor de enriquecimiento isotópico obtenidos fueron -27.5‰ para εN y de -33.7‰ para εO.Centro de Investigaciones Geológica

An interdisciplinary methodology to design integrated and innovative MAR systems in arid and semi-arid regions. Two case studies in Algeria and in Tunisia

Drought,  desertification, Managed Aquifer Recharge (MAR), Tunisia, Algeri

Evaluation of two carbon sources for inducing denitrification: batch and column experiments

Artificial recharge improves several water quality parameters. Denitrification is a good example of water treatment process that could be achieved through artificial recharge. To improve the removal of nitrate and other emerging organic contaminants (EOCs) a reactive barrier at the bottom of aninfiltration pond can be added. In the present study, the efficiency in removing nitrate of an artificial recharge system with a compost layer located in the Mediterranean area (Sant Vicenç dels Horts, Catalonia)is evaluated, as well as the feasibility of another carbon source to be used as reactive layer in the artificial recharge system planned in theMaghreb Region. We examined the effectiveness of two different materials, commercial compost and crushed palm tree leaves, in batch and column experiments. The results of batch experiments confirmed that both materials induced denitrification andthe flow-through experiments showed complete nitrate removal. The isotopic fractionation of nitrogen and oxygen of dissolved nitrate was calculated for both experiments in order to provide a tool to evaluate the efficacy of the treatments in future field scale studies.Peer ReviewedPostprint (published version

Evaluation of two carbon sources for inducing denitrification: batch and column experiments

Artificial recharge improves several water quality parameters. Denitrification is a good example of water treatment process that could be achieved through artificial recharge. To improve the removal of nitrate and other emerging organic contaminants (EOCs) a reactive barrier at the bottom of an infiltration pond can be added. In the present study, the efficiency in removing nitrate of an artificial recharge system with a compost layer located in the Mediterranean area is evaluated, as well as the feasibility of another carbon source to be used as reactive layer in the artificial recharge system planned in the Maghreb Region. We examined the effectiveness of two different materials, commercial compost and crushed palm tree leaves, in batch and column experiments.Peer ReviewedPostprint (published version

Multiple isotope and hydro-chemical techniques investigating dynamics and sources of dic within a multiple aquifer system of a groundwater fed lake catchment (Lough Gur, Ireland)

Lake groundwater discharge, isotope, biogeochemical processe

Isotopic fractionation associated to nitrate attenuation by ferrous iron containing minerals

Biotic and abiotic laboratory experiments of nitrate and nitrite reduction by Fe-containing minerals were performed and the isotopic fractionation of the different reactions was calculated in order to determine whether it is possible to distinguish biotic and abiotic reactions involving N compounds. Results of biotic experiments showed nitrate reduction up to 96 % with transient NO2- accumulation and no significant N2O production. No significant nitrate attenuation was observed in abiotic nitrate reduction experiments. Abiotic experiments of nitrite reduction showed a rapid decrease in nitrite concentrations in those experiments with added Fe2+ coupled with a significant N2O production. Preliminary results of the N and O isotopic fractionation of the biotic experiments of nitrate reduction show differences in the ε15NNO3 and ε18ONO3 when different minerals were added. The abiotic experiments of nitrite reduction contrarily, showed similar ε15NNO2 in all the experiments

Tracing the role of endogenous carbon in denitrification using wine industry by-product as an external electron donor: coupling isotopic tools with mathematical modeling

Nitrate removal through enhanced biological denitrification (EBD), consisting of the inoculation of an external electron donor, is a feasible solution for the recovery of groundwater quality. In this context, liquid waste from wine industries (wine industry by-products, WIB) may be feasible for use as a reactant to enhance heterotrophic denitrification. To address the feasibility of WIB as electron donor to promote denitrification, as well as to evaluate the role of biomass as a secondary organic C source, a flow-through experiment was carried out. Chemical and isotopic characterization was performed and coupled with mathematical modeling. Complete nitrate attenuation with no nitrite accumulation was successfully achieved after 10 days. Four different C/N molar ratios (7.0, 2.0, 1.0 and 0) were tested. Progressive decrease of the C/N ratio reduced the remaining C in the outflow and favored biomass migration, producing significant changes in dispersivity in the reactor, which favored efficient nitrate degradation. The applied mathematical model described the general trends for nitrate, ethanol, dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. This model shows how the biomass present in the system is degraded to dissolved organic C (DOCen) and becomes the main source of DOC for a C/N ratio between 1.0 and 0. The isotopic model developed for organic and inorganic carbon also describes the general trends of d13C of ethanol, DOC and DIC in the outflow water. The study of the evolution of the isotopic fractionation of organic C using a Rayleigh distillation model shows the shift in the organic carbon source from the WIB to the biomass and is in agreement with the isotopic fractionation values used to calibrate the model. Isotopic fractionations (e) of C-ethanol and C-DOCen were -1‰ and -5‰ (model) and -3.3‰ and -4.8‰ (Rayleigh), respectively. In addition, an inverse isotopic fractionation of +10‰ was observed for biomass degradation to DOCen. Overall, WIB can efficiently promote nitrate reduction in EBD treatments. The conceptual model of the organic C cycle and the developed mathematical model accurately described the chemical and isotopic transformations that occur during this induced denitrification.Peer Reviewe