Induced nitrate attenuation by glucose in groundwater: Flow-through experiment

Journal of Contaminant Hydrology

et al. 2017

Self Cite

Anaerobic batch and flow-through experiments were performed to assess the capacity of two organic substrates to promote denitrification of nitrate-contaminated groundwater within managed artificial recharge systems (MAR) in arid or semi-arid regions. Denitrification in MAR systems can be achieved through artificial recharge ponds coupled with a permeable reactive barrier in the form of a reactive organic layer. In arid or semi-arid regions, short-term efficient organic substrates are required due to the short recharge periods. We examined the effectiveness of two low-cost, easily available and easily handled organic substrates, commercial plant-based compost and crushed palm tree leaves, to determine the feasibility of using them in these systems. Chemical and multi-isotopic monitoring (δN, δO, δS, δO) of the laboratory experiments confirmed that both organic substrates induced denitrification. Complete nitrate removal was achieved in all the experiments with a slight transient nitrite accumulation. In the flow-through experiments, ammonium release was observed at the beginning of both experiments and lasted longer for the experiment with palm tree leaves. Isotopic characterisation of the released ammonium suggested ammonium leaching from both organic substrates at the beginning of the experiments and pointed to ammonium production by DNRA for the palm tree leaves experiment, which would only account for a maximum of 15% of the nitrate attenuation. Sulphate reduction was achieved in both column experiments. The amount of organic carbon consumed during denitrification and sulphate reduction was 0.8‰ of the total organic carbon present in commercial compost and 4.4% for the palm tree leaves. The N and O isotopic fractionation values obtained (ε and ε) were -10.4‰ and -9.0‰ for the commercial compost (combining data from both batch and column experiments), and -9.9‰ and -8.6‰ for the palm tree column, respectively. Both materials showed a satisfactory capacity for denitrification, but the palm tree leaves gave a higher denitrification rate and yield (amount of nitrate consumed per amount of available C) than commercial compost.

Section: Denitrification Rate and Organic C Reactivitycontrasting

confidence: 99%

Feasibility of two low-cost organic substrates for inducing denitrification in artificial recharge ponds: Batch and flow-through experiments

Grau-Martínez

Torrentó

Journal of Contaminant Hydrology

et al. 2017

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“…Therefore, it was decided to evaluate the feasibility of adding an external electron donor source to promote NO3attenuation when operating at a ~16 L/s flow rate. experiments and other denitrification studies (Carrey et al, 2014;Margalef-Marti et al, 2019;Vidal-Gavilan et al, 2013). The maximum NH4 + concentration of 0.02 mM was measured at H3 after 7 d, while it decreased by the outlet (H6) to 0.01 mM in both campaigns, pointing to a nonsignificant contribution of DNRA.…”

Section: Performance Of the Cw Before Application Of Stubblementioning

confidence: 66%

Feasibility of using rural waste products to increase the denitrification efficiency in a surface flow constructed wetland

Margalef-Marti

Merchán

et al. 2019

Journal of Hydrology

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A surface flow constructed wetland (CW) was set in the Lerma gully to decrease nitrate (NO3 -) pollution from agricultural runoff water. The water flow rate and NO3concentration were monitored at the inlet and the outlet, and sampling campaigns were performed which consisted of collecting six water samples along the CW flow line. After two years of operation, the NO3attenuation was limited at a flow rate of ~2.5 L/s and became negligible at ~5.5 L/s. The present work aimed to assess the feasibility of using rural waste products (wheat hay, corn stubble, and animal compost) to induce denitrification in the CW, to assess the effect of temperature on this process, and to trace the efficiency of the treatment by using isotopic tools. In the first stage, microcosm experiments were performed. Afterwards, the selected waste material was applied in the CW, and the treatment efficiency was evaluated by means of a chemical and isotopic characterization and using the isotopic fractionation (ε) values calculated from laboratory experiments to avoid field-scale interference. The microcosms results showed that the stubble was the most appropriate material for application in the CW, but the denitrification rate was found to decrease with temperature. In the CW, biostimulation in autumn-winter promoted NO3attenuation between two weeks and one month (a reduction in NO3between 1.2 and 1.5 mM was achieved). After the biostimulation in spring-summer, the attenuation was maintained for approximately three months (NO3reduction between 0.1 and 1.5 mM). The ε 15 NNO3/N2 and ε 18 ONO3/N2 values obtained from the laboratory experiments allowed to estimate the induced denitrification percentage. At an approximate average flow rate of 16 L/s, at least 60 % of NO3attenuation was achieved in the CW. The field samples exhibited a slope of 1.0 for δ 18 O-NO3versus δ 15 N-NO3 -, similar to those of the laboratory experiments (0.9-1.2). Plant uptake seemed to play a minor role in NO3attenuation in the CW. Hence, the application of stubble in the CW allowed the removal of large amounts of NO3from the Lerma gully, especially when applied during the warm months, but its efficacy was limited to a short time period (up to three months).

“…The enzymatic repression is controlled by several factors such as the organic C type, pH and evolution of the microbial population involved in the reaction (Glass and Silverstein 1998, Gómez et al 2000, Martin et al 2009). The organic C from WIB was mainly ethanol, which produces low NO 2 accumulation during denitrification (Carrey et al 2014a, Gómez et al 2000, Martin et al 2009. The pH measured in the outflow water was within the optimum range for NO 2 (Glass and Silverstein 1998).…”

Section: Denitrification Enhanced By Wib Injection and No 2 Accumulationmentioning

confidence: 91%

“…The DOC inoculated is commonly calculated by considering only the organic carbon injected into the system. However, as the denitrifier biomass grows and dies, a new carbon pool, formed by dead and lysed cells, appears in the system and has the potential to become a new source for denitrification (Carrey et al 2014a, Rodríguez-Escales et al 2016b, Rodríguez-Escales et al 2014, Torrentó et al 2011. The total denitrification rate is the combined reduction of NO 3 due to the different organic carbon sources, including external, or exogenous, and internal, or endogenous, sources.…”

Section: Introductionmentioning

confidence: 99%

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

Journal of Environmental Management

Rodríguez‐Escales

Soler

et al. 2018

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 (DOC) 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 δC 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 (ε) of C-ethanol and C-DOC 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 DOC. 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.