54 research outputs found
Integrating Enzyme-Based Kinetics in Reactive Transport Models to Simulate Spatiotemporal Dynamics of Biomarkers during Chlorinated Ethene Degradation
No full textBiomarkers such as functional gene mRNA (transcripts) and proteins (enzymes) provide direct proof of metabolic regulation during the reductive dechlorination (RD) of chlorinated ethenes (CEs). Yet, current models to simulate their spatiotemporal variability are not flexible enough to mimic the homologous behavior of RDase functional genes. To this end, we developed new enzyme-based kinetics to model the concentrations of CEs together with the transcript and enzyme levels during RD. First, the model was calibrated to existing microcosm data on RD of cis-DCE. The model mirrored the tceA and vcrA gene expression and the production of their enzymes in Dehalococcoides spp. Considering tceA and vcrA as homologous instead of nonhomologous improved fitting of the mRNA time series. Second, CEs and biomarker patterns were explored as a proof of concept under groundwater flow conditions, considering degraders occurring in immobile and mobile states. Under both microcosm and flow conditions, biomarker-rate relationships were nonlinear hysteretic because tceA and vcrA acted as homologous genes. The mobile biomarkers additionally undergo advective-dispersive transport, which increases the nonlinearity and makes the observed patterns even more challenging to interpret. The model offers a thorough mechanistic description of RD while also allowing simulation of spatiotemporal dynamic patterns of various key biomarkers in aquifers
Modeling of enhanced in situ biodenitrification at different scales: Integration of microbiological, hydrogeochemical, and isotope biogeochemical processes
No full textPremi Extraordinari de Doctorat concedit pels programes de doctorat de la UAB per curs acadèmic 2017-2018En aquesta tesi s'ha desenvolupat un model de transport reactiu que integra tots els processos principals i secundaris que afecten la desnitrificació in situ induïda a diferents escales de treball. Així, l'eina obtinguda relaciona els processos biològics induïts quan s'afegeix un donador d'electrons a l'aqüífer amb els processos geoquímics (interacció aigua-roca) i la geoquímica dels isòtops. A la primera part de la tesi (Capítol 2) és on s'ha desenvolupat el model conceptual i on s'han establert les relacions que existeixen entre la microbiologia i la geoquímica prèvia de l'aqüífer a escala de batch. D'altra banda, també s'ha desenvolupat el model conceptual de tota la geoquímica isotòpica associada al procés (δ15N-NO3-; δ18O-NO3- i δ13C-DIC incorporant tota la geoquímica del δ13C). En aquest sentit, s'ha desenvolupat un dels models biogeoquímics més complets de la literatura relacionats amb la desnitrificació in situ induïda. El model s'ha calibrat emprant dos experiments a escala de batch realitzats amb etanol i glucosa com a fonts de carboni externa. En tots dos casos, s'han obtingut molt bons ajustos amb les dades experimentals. A més, el model també incorpora l'acumulació de nitrit en el cas de l'experiment de la glucosa. L'avaluació dels processos geoquímics induïts per l'EIB ha posat de manifest que en funció de la font de carboni s'indueixen processos de precipitació (en el cas de l'etanol) i processos de dissolució de carbonats (en el cas de la glucosa). Aquests dos processos poden alterar la velocitat de l'aigua i crear importants problemes operacionals durant l'EIB. També s'han incorporat els processos de fraccionament isotòpic del nitrat millorant l'avaluació de l'abast de la desnitrificació en els models a escala de camp. Un cop elaborat el model biogeoquímic que estableix el model conceptual que quantifica les interaccions entre els diferents processos que hi intervenen, el model s'ha escalat a un cas de desnitrificació induïda a escala de camp en un aqüífer fracturat (Roda de Ter (Osona, Espanya)). En aquest apartat de la tesi (Capítol 3), s'ha perseguit avaluar quin era l'impacte del canvi d'escala en els paràmetres biogeoquímics. A més a més, també s'ha determinat el canvi de porositat induïda per la precipitació de calcita. Finalment, la incorporació dels isòtops al RTM ha permès comparar qualitativament i quantitativament l'extensió dels processos de desnitrificació calculats pel RTM i per l'equació de Rayleigh. Els resultats demostren que l'equació de Rayleigh descriu bé, en termes qualitatius, l'extensió de la desnitrificació, però en general la subestima entre un 60 i un 80%. Finalment, un cop avaluada l'aplicabilitat del model tant a escala de batch com a l'escala de camp, s'ha desenvolupat un model que reprodueix diferents escenaris d'injeccions de carboni orgànic en un experiment de columna de llarga durada considerant els canvis sobre les propietats hidràuliques produïts pel creixement microbià. Així, s'ha determinat que el creixement del biofilm va augmentar set cops la dispersivitat, augmentant, per tant, la heterogeneïtat del sistema i, conseqüentment, es va produir un canvi del model conceptual del flux i del transport del transport normal al transport no-Fickià. Aquesta transició es va caracteritzar emprant un model de transferència simple de massa. A més a més, el model de llarga durada ha permès determinar que freqüències d'injecció més espaiades en el temps produeixen un impacte menor en les propietats hidràuliques del medi. A més a més, les estratègies d'injecció amb la relació Carboni:Nitrogen per sota de l'estequiomètrica es poden emprar per a minimitzar el risc de bioclogging mantenint les taxes de degradació, sempre i quan hi hagi una població important de microorganismes.In this thesis, an integrated reactive transport model has been developed that takes into account microbiology, geochemistry, and isotope geochemistry. The first section of the thesis (Chapter 2) addresses the development of a biogeochemical model with isotope geochemistry. The goal of this chapter is the setup of the conceptual relationships among microbiology, geochemistry, and isotope geochemistry (δ15N-NO3-, δ18O-NO3-, δ13C-DIC, and all geochemistry of δ13C) during Enhanced in situ Biodenitrification. Thus, one of the most complete biogeochemical models in the literature of EIB has been developed. The model was validated with a batch-scale biodenitrification experiment using groundwater and sediment from a Roda de Ter (Osona, Spain) site and two different external organic carbon sources, i.e., ethanol and glucose. In both cases, the model fit notably well with the experimental data. Moreover, the developed model also incorporated the nitrite accumulation observed in the glucose experiment. Consideration of the water-rock interaction in the model determined that if ethanol is used as an organic carbon source, carbonate mineral precipitation is induced, whereas if glucose is used, carbonate mineral dissolution is observed. Moreover, nitrate isotope incorporation facilitated the determination of the extent of denitrification at the field scale. Finally, the incorporation of a carbon isotope flow in the model was another tool used to verify the full consistence of the model due to the central role of inorganic carbon in biodenitrification and water-rock interactions. Moreover, modeling of carbon isotope flow showed that both ethanol and glucose were inversely fractionated. After the conceptual model was carried out, it was applied to an Enhanced in situ Biodenitrification application in fractured media (also Roda de Ter (Spain)). The main goal of this chapter is to incorporate the groundwater flow equations into a previously develop biogeochemical model and to validate it in media with a complex hydrogeology. It was observed that certain batch parameters can be used directly in the field (maximum consumption rate of electron donor (kmax) and stoichiometric relationships) and that the other parameters (saturation constants (Ks) and decay (b)) should be adapted, but the modifications involved less than one order of magnitude. Moreover, the induced calcite precipitation caused a change of porosity of less than 3%. As a secondary goal, the use of the Rayleigh equation to determine the extent of EIB was also verified from a practical perspective. The model demonstrated that the Rayleigh equation underestimated the percentage of degradation by approximately 60-80% and increasingly at the fringes of the plume. Chapter 4 focuses on a model that reproduces the system under different injection conditions and with the presence of important biofilm growth. This chapter evaluates how different feeding strategies modify the hydraulic properties of the media. It was observed that a weekly feeding strategy did not modify the hydraulic properties of the media, whereas daily feeding significantly modified the dispersivity. These changes in dispersivity implied an increase in heterogeneity and a consequent change in the conceptual model of flow transport along the column from normal to non-Fickian. This transition was well characterized using a single-rate mass transfer model. Moreover, the long-term model demonstrated that use of a feeding strategy with less carbon than predicted by stoichiometry implied a reduction of biomass without a reduction in nitrate degradation rates (because of the presence of an important biomass population). Overall, the elaboration of this thesis has contributed to the knowledge of all processes involved in Enhanced in situ Biodenitrification and their quantification using numerical models. The developed model will allow improvement in the design, planning, monitoring and optimization of this technology at the field scale
Verwijdering van plantpathogenen uit drainagewater door ondergrondse opslag voor veilig irrigatiewater.
No full textDe aanwezigheid van bacteriële plantpathogen in oppervlaktewater en hun verspreiding via irrigatie vormt een bedreiging voor gewasziekten. Een natuurlijke oplossing voor veilig irrigratiewater is ondergrondse opslag van water, ofwel 'manged aquifer recharge' (MAR), Drainagewater wordt opgevangen en geïnfiltreerd in brakke/zoute watervoerende lagen (aquifer), resulterend in een zoet water 'bubbel' in de ondergrond. Dit geeft agrariërs toegang tot voldoende zoet water voor de irrigratie van gewassen, zelfs in tijden van droogte
Verwijdering van plantpathogenen uit drainagewater door ondergrondse opslag voor veilig irrigatiewater.
No full textDe aanwezigheid van bacteriële plantpathogen in oppervlaktewater en hun verspreiding via irrigatie vormt een bedreiging voor gewasziekten. Een natuurlijke oplossing voor veilig irrigratiewater is ondergrondse opslag van water, ofwel 'manged aquifer recharge' (MAR), Drainagewater wordt opgevangen en geïnfiltreerd in brakke/zoute watervoerende lagen (aquifer), resulterend in een zoet water 'bubbel' in de ondergrond. Dit geeft agrariërs toegang tot voldoende zoet water voor de irrigratie van gewassen, zelfs in tijden van droogte
Pilot study and modelling of remineralization of low-temperature desalinated water by calcite filtration
No full textTo prepare for future challenges, such as possible upcoming organic micro pollutants in the source water, including traces of medicines, pesticides, and industrial by-products, it is expected that the conventional treatment does not ensure a reliable quality of drinking water. As a result, during the past few years, Oasen started to research a new treatment concept based on 100% reverse osmosis (RO) membrane filtration to provide an excellent barrier for organic micro pollutants. However, the water produced by the RO membranes, called permeate, is corrosive, bitter in taste and does not comply with the drinking water regulation standards in the Netherlands. Therefore, a certain degree of remineralisation is crucial to solve these problems and improve the water quality. A commonly used remineralisation process is to filter the desalinated water through a calcite contactor, providing the appropriate amount of bicarbonate and calcium in the water. In order to properly design and operate the calcite filters as well as to predict the final water quality, it is essential to understand the processes that occur in the filter. The aim of this study was to find the best kinetic calcite dissolution model in order to understand the calcite grains dissolution behavior inside the filter and subsequently to adequately design and operate the calcite filter. Therefore, extensive pilot research was conducted to investigate the effect of various parameters on calcite dissolution such as the calcite grain size, velocity and carbon dioxide concentration. On top of that, the dissolution was modelled based on a successful empirical expression given by Yamauchi et al. (1987). However, it was found that the effect of the flow rate on the diffusion boundary layer around the calcite grains has not been taken into account in the study carried out by Yamauchi et al. (1987). Therefore, the effect of velocity on the calcite dissolution coefficient was investigated at five different velocity ,i.e., 5, 10,15,20,30 m/h. From there, a function was developed to describe the correlation between flow rate and the dissolution rate coefficient. In order to calculate the equilibrium concentration, the chemical reactions were simulated using PhreeqPython (Phreeqc built in Python).The main difference of this study compare to previous investigations was the low temperature of the water (12 oC vs 22-40 oC) and the smaller grain size of the calcite (0.5-1.2 mm vs 1-2 and 2-3mm) which was tested. Besides that a high range of CO2 dosing (1.45- 9.5 mmol/l) was tested. As expected from theory, the dissolution rates was strongly affected by the varied parameters. It is concluded that the smaller grain size of 0.5-1.2 mm reduced the required empty bed contact time (EBCT) to15 min where operating the filter with the larger grain size of 1-2mm needs a minimum EBCT of 25 min to reach calcite equilibrium. The CO2 dosing is recommended to be less than 3 mmol/l, since the CO2 efficiency will drop under the 60% at higher CO2 concentrations. Eventually, the optimal design will be introduced for the remineralisation process at Oasen treatment plant De Hooge Boom located in Kamerik. For this purpose various operational scenarios were compared on capital and operational cost. The overall cost including, both Capital expenses (CAPEX) and Operational expenses OPEX, was estimated between € 0.048 and 0.064 per m3 for different scenario’s where 71% consists of investment cost. The total treatment cost of this design is 0.057 €/m3 and the investment cost was found to be € 1.351.000 which is 32% less than price estimated by previous study done by Oasen. Remineralisatio
Microbially mediated kinetic sulfur isotope fractionation: reactive transport modeling benchmark
No full textMicrobiallymediated sulfate reduction is a ubiquitous process inmany subsurface systems. Isotopic fractionation is characteristic of this anaerobic process, since sulfate-reducing bacteria (SRB) favor the reduction of the lighter sulfate isotopologue (S32O42−) over the heavier isotopologue (S34O42−). Detection of isotopic shifts has been utilized as a proxy for the onset of sulfate reduction in subsurface systems such as oil reservoirs and aquifers undergoing heavy metal and radionuclide bioremediation. Reactive transport modeling (RTM) of kinetic sulfur isotope fractionation has been applied to field and laboratory studies.We developed a benchmark problem set for the simulation of kinetic sulfur isotope fractionation during microbially mediated sulfate reduction.
The benchmark problem set is comprised of three problem levels and is based on a large-scale laboratory column experimental study of organic carbon amended sulfate reduction in soils from a uranium-contaminated aquifer. Pertinent processes impacting sulfur isotopic composition such as microbial sulfate reduction and iron-sulfide reactions are included in the problem set. This benchmark also explores the different mathematical formulations in the representation of kinetic sulfur isotope fractionation as employed in the different RTMs. Participating RTM codes are the following: CrunchTope, TOUGHREACT, PHREEQC, and PHT3D. Across all problem levels, simulation results from all RTMs demonstrate reasonable agreemen
Decomposing the Bulk Electrical Conductivity of Streamflow To Recover Individual Solute Concentrations at High Frequency
No full textThe ability to evaluate stream hydrochemistry is often constrained by the capacity to sample streamwater at an adequate frequency. While technology is no longer a limiting factor, costs and sample management can still be a barrier to high-resolution water quality instrumentation. We propose a new framework for investigating the electrical conductivity (EC) of streamwater, which can be measured continuously through inexpensive sensors. We show that EC embeds information about individual ion content that can be isolated to retrieve solute concentrations at high resolution. The essence of the approach is the decomposition of the EC signal into its "harmonics", i.e., the specific contributions of the major ions that conduct current in water. The ion contribution is used to explore water quality patterns and to develop algorithms that reconstruct solute concentrations starting from EC during periods where solute measurements are not available. The approach is validated on a hydrochemical data set from Plynlimon, Wales, showing that improved estimates of high-frequency solute dynamics can easily be achieved. Our results support the installation of EC probes to complement water quality campaigns and suggest that the potential of EC measurements in rivers is currently far from being fully exploited.Sanitary Engineerin
Removal of bacterial plant pathogens in columns filled with quartz and natural sediments under anoxic and oxygenated conditions
No full textIrrigation with surface water carrying plant pathogens poses a risk for agriculture. Managed aquifer recharge enhances fresh water availability while simultaneously it may reduce the risk of plant diseases by removal of pathogens during aquifer passage. We compared the transport of three plant pathogenic bacteria with Escherichia coli WR1 as reference strain in saturated laboratory column experiments filled with quartz sand, or sandy aquifer sediments. E. coli showed the highest removal, followed by Pectobacterium carotovorum, Dickeya solani and Ralstonia solanacearum. Bacterial and non-reactive tracer breakthrough curves were fitted with Hydrus-1D and compared with colloid filtration theory (CFT). Bacterial attachment to fine and medium aquifer sand under anoxic conditions was highest with attachment rates of max. k att1 = 765 day -1 and 355 day -1, respectively. Attachment was the least to quartz sand under oxic conditions (k att1 = 61 day -1). In CFT, sticking efficiencies were higher in aquifer than in quartz sand but there was no differentiation between fine and medium aquifer sand. Overall removal ranged between < 6.8 log 10 m −1 in quartz and up to 40 log 10 m −1 in fine aquifer sand. Oxygenation of the anoxic aquifer sediments for two weeks with oxic influent water decreased the removal. The results highlight the potential of natural sand filtration to sufficiently remove plant pathogenic bacteria during aquifer storage. Sanitary Engineerin
Biogeochemical processes at the fringe of a landfill leachate pollution plume: potential for dissolved organic carbon, Fe (II), Mn(II), NH4 and CH4 oxidation.
No full textVarious redox reactions may occur at the fringe of a landfill leachate plume, involving oxidation of dissolved organic carbon (DOC), C
Decomposing the Bulk Electrical Conductivity of Streamflow To Recover Individual Solute Concentrations at High Frequency
No full textThe ability to evaluate stream hydrochemistry is often constrained by the capacity to sample streamwater at an adequate frequency. While technology is no longer a limiting factor, costs and sample management can still be a barrier to high-resolution water quality instrumentation. We propose a new framework for investigating the electrical conductivity (EC) of streamwater, which can be measured continuously through inexpensive sensors. We show that EC embeds information about individual ion content that can be isolated to retrieve solute concentrations at high resolution. The essence of the approach is the decomposition of the EC signal into its "harmonics", i.e., the specific contributions of the major ions that conduct current in water. The ion contribution is used to explore water quality patterns and to develop algorithms that reconstruct solute concentrations starting from EC during periods where solute measurements are not available. The approach is validated on a hydrochemical data set from Plynlimon, Wales, showing that improved estimates of high-frequency solute dynamics can easily be achieved. Our results support the installation of EC probes to complement water quality campaigns and suggest that the potential of EC measurements in rivers is currently far from being fully exploited.ECH
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