Дисертації з теми "Solute transport modelling"

Surface water and groundwater systems are linked dynamically in reality as the one generally impacts directly on the other. Traditionally, however, these two water bodies have more often than not been treated as different entities by water managers and other professionals. The issue of the compartmentality of these two resources is the main focus of the study described herein. In this study, an existing 1D-2D hydro-environmental surface water model that includes a groundwater model (DIVAST-SG) has been extended to 2-D and refined through testing against three laboratory studies. A surface water-groundwater system model using foam to replicate groundwater material was created in the laboratory and the results of the hydrodynamic processes (i.e. water elevations and flowpaths) were compared with the numerical model predictions. On the whole the comparisons showed good agreement. However, dye studies for replicating pollutant transport did not show such good agreement and this discrepancy was thought to be due to a number of reasons. In the second series of studies, the groundwater material was then replaced with the more traditional sand embankment and again results for both hydrodynamic and solute transport processes (by way of dye studies) from the laboratory set up were compared with the numerical predictions which were in almost perfect agreement. In the same tidal basin, a Severn Estuary model was then designed and set up. Although there were differences from the prototype owing to space and scaling difficulties, the results showed good agreement for both tidal amplitudes and tidal currents with the predictions from the numerical model and particularly the tidal amplitudes were found to compare favourably with field studies. Tracer results from the physical model also showed consistency with simulations from previous researchers in the main estuary. Overall, the purpose of this study, which was to investigate the manner in which flow and solute (conservative tracer) fluxes interacted between surface and sub-surface flows, for simulated riverine and tidal conditions, has been achieved. These experiments and the corresponding datasets are thought to be unique.

According to published statistics regarding pharmaceutical industries, there has been a significant increase in the demand for cosmetics and skincare products. As a result, there has also been an increase in interest by researchers to conduct experimental and theoretical studies on these industries. The outermost layer of the skin, which is the stratum corneum, plays a key role in determining the skin permeability. This layer represents the first and main barrier against dehydration and screening from external elements and pathogens. Research efforts have been made to better understand skin permeability. Experimental methodologies play a key role in pharmaceutical and dermatology studies. However, ethical standards of using animal and human models in in-vitro permeability studies are very strict in their admission process and approval time. Furthermore, the lack of available material and financial resources for setting up, operating and repeating experiments has also limited the required progress. These problems can be addressed by developing better mathematical models on skin permeability. Progress, regarding the mathematical modelling of solute transport in skin, has been achieved in the last decades. The mathematical modelling strategy is used as a skin permeability predictor tool based on common physicochemical properties of the skin and penetrated solute molecules. Many factors play an important role in the formulation of a mathematical model and in determining how reliable the predicted results are. Therefore, the more skin physiological details are included in the model, the more computational efforts are required to interpret the solute permeation mechanisms in the dermal region and simulate a drug transport in the transdermal administration. The mathematical complexities associated with formulating a mathematical model of drug transport in skin significantly limit the utilities of such models in practice. Thus, a balance between the model’s complexity and how realistic it is in describing the solute transport processes in skin has to be achieved. Therefore, a mathematical model formulated on principles familiar to the pharmaceutical scientific community could be of value. In this thesis, we have developed a novel mathematical model using a compartmental approach. The proposed model enables for simulating solute transport across the stratum corneum (SC) in a variety of exposure scenarios in percutaneous drug delivery systems. The obtained results were compared with the diffusion model outcomes – which can be considered the current ‘golden standard’ for modelling skin transport – and showed a good agreement. The mathematical foundations of the model are relatively simple and better aligned with the physiology of the stratum corneum. In addition, this work shows that performing a numerical simulation using the compartmental model is less demanding than using the diffusing model, especially for complex exposure scenarios, and can be performed using free software, such as Python. The research findings of this thesis contribute towards a better understanding of transport phenomena across the skin. Also, the compartmental model proposed in this work can be used to describe transport phenomena in the membrane. Due to the similarity between the governing equations of diffusion and heat transfer, the proposed approach also offers a mathematical framework for studying heat transfer problems in biomaterials with minimum model development or computational efforts.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text

Models predicting the fate of water and dissolved chemicals in vegetated soils are required for a wide range of applications. Substantial uncertainty is present due to measurement errors, parametric uncertainty, and structural issues related to model con- ceptualisation. Due to the costs and intrusiveness of subsurface measurements there are limited datasets available to interrogate models against. Furthermore, the models are typically computationally intensive, making it di±cult to fully explore parametric and other uncertainty spaces. Hence there are two pressing needs which must be met to improve the utility of models: more data and constraints are required to quantify the impacts of uncertainty, and e±cient methodologies to explore sensitivities and uncer- tainties are also needed. This dissertation presents and applies a stochastic framework addressing the above concerns. Approaches and underlying assumptions to modelling water °ow and solute transport within soils and plants are examined, and two ex- isting models extended. The problem of uncertainty is investigated, and appropriate approaches suggested. Monte-Carlo techniques, including Markov chain Monte Carlo methods, are developed for application to the models, and tested using a comprehen- sive hydrological and radiological dataset from a plot-scale lysimeter experiment. The integrity of the experimental data is examined. Sensitivity analysis and calibration of the hydrological and radiological data sets is performed, with the ability of the model and framework to recover parameters interrogated. Structural uncertainty and e®ects of erroneous inputs are discussed. Results demonstrate the power of the methods to generate insights into process response and quantify uncertainties. The e±ciency of Markov Chain Monte Carlo techniques is demonstrated, but the advantages of retain- ing simple set search methodologies are also clear. Consideration of model structure also signi¯cantly reduces the uncertain parametric space. However, despite the unusu- ally comprehensive experimental dataset, major issues of uncertainty remain, of which data issues are a dominant component.

In this dissertation, a new numerical method is developed for the simulation of nonideal solute transport in porous media, and a first order semi-analytical solution is derived for solute transport in porous media with spatially variable multiple reaction processes. The Laplace transform is used to eliminate the time dependency and the transformed transport equations are solved both numerically and analytically. The transport solution is ultimately recovered by an efficient quotient-difference inversion algorithm. By introducing complex-valued artificial dispersion in the weighting functions, characteristics of transport solutions have been successfully addressed. The optimum of the complex-valued artificial dispersion has been derived for one dimensional problems. In multidimensional cases, the streamline upwind scheme is modified by adding complex-valued artificial dispersion along the streamline. Within this numerical scheme, the grid orientation problems have been successfully treated. The limitations on the cell Peclet number and on the Courant number were greatly relaxed. Both one dimensional and two dimensional numerical examples are used to illustrate applications of this technique. The analysis has been made for solute transport in systems with spatially variable multiple reaction processes. Specific reaction processes include reversible sorption and irreversible transformations (such as radioactive decay, hydrolysis reactions with fixed pH, and biodegradation). With the assumptions of solute transport in a system with constant hydraulic conductivity and hydrodynamic dispersion and spatially variable multiple reaction processes, a first-order semi-analytical solution is derived for an arbitrary autocovariance function, which characterizes the spatial variation of the multiple reaction processes. Results indicate that spatial variation of the transformation constants for the solution phase and the sorbed phase decreases the global rate of mass loss and enhances solute transport. If the transformation constant for the sorbed phase is spatially uniform but not zero, a similar effect is observed when there is spatial variation of the equilibrium sorption coefficient. The global rate of mass loss and apparent retardation are decreased when the spatial variability of the sorbed-phase transformation constant is positively correlated with the spatial variability of the equilibrium sorption coefficient, and increased for a negative correlation. Spatial variation of the sorption rate coefficient had minimal effect on transport.

Hydrological processes are greatly influenced by the characteristics of the domain through which the process occurs. It is generally accepted that earth materials have extreme variations from point to point in space. Consequently this heterogeneity results in high variation in hydraulic properties of soil. In order to develop a reliable predictive model for transport processes in soil, the effects of this variability must be considered. Soil heterogeneity due to presence of macropores (micro-) and to spatial variability in hydraulic properties (macro-heterogeneity) coexists in the real field conditions. The challenge is to incorporate the effects of both types of soil heterogeneity in simulation models. This thesis presents development and application of a 2D/3D numerical model for simulation of advection and diffusion-dispersion contaminant transport considering both types of soil heterogeneity. Stochastic finite element approach is used to incorporate the effects of the spatial variability of soil hydraulic properties on contaminant fate. The soil micro heterogeneity effects are modelled with a dual domain concept in which a first order kinetic expression is used to describe the transfer of the solute between the two domains. Also, the capability of the model in 3D simulation of field problems improves the accuracy of the results, since it is possible to avoid the generally applied assumption in 2D simulations. From comparison of the model results with experimental and analytical results, it is concluded that the model performs well in predicting contaminant fate and the incorporation of the both types of micro- and macro- heterogeneity in the simulation models improves the accuracy of the prediction. Also, capability of the model in evaluation of the concentration variation coefficient as an index of reliability of the model outputs makes it possible to estimate a probable interval (mean concentration minus and plus standard deviation) for the range of oscillations of possible realizations of solute distribution. Moreover, comparison of the results of the proposed method with the results obtained using the Monte Carlo approach yields a pronounced reduction in the computation cost while resulting in virtually the same response variability as the Monte Carlo technique.

The small intestine is the foremost site of nutrient absorption in the body. Although many attempts have been made at modelhng absorption through the small intestine, few account explicitly for its small-scale geometry. In this thesis we consider a model of the small intestine as a wavy-walled channel, where the wavelength and amplitude of the waves are comparable to each other but are small in relation to the channel width.

The modelling of the processes of advection and dispersion-diffusion is the most crucial factor in solute transport simulations. It is generally appreciated that the first order upwind difference scheme gives rise to excessive numerical diffusion, whereas the conventional second order central difference scheme exhibits severe oscillations for advection dominated transport, especially in regions of high solute gradients or discontinuities. Higher order schemes have therefore become increasingly used for improved accuracy and for reducing grid scale oscillations. Two such schemes are the QUICK (Quadratic Upwind Interpolation for Convective Kinematics) and TOASOD (Third Order Advection Second Order Diffusion) schemes, which are similar in formulation but different in accuracy, with the two schemes being second and third order accurate in space respectively for finite difference models. These two schemes can be written in various finite difference forms for transient solute transport models, with the different representations having different numerical properties and computational efficiencies. Although these two schemes are advectively (or convectively) stable, it has been shown that the originally proposed explicit QUICK and TOASOD schemes become numerically unstable for the case of pure advection. The stability constraints have been established for each scheme representation based upon the von Neumann stability analysis. All the derived schemes have been tested for various initial solute distributions and for a number of continuous discharge cases, with both constant and time varying velocity fields. The 1-D QUICKEST (QUICK with Estimated Streaming Term) scheme is third order accurate both in time and space. It has been shown analytically and numerically that a previously derived quasi 2-D explicit QUICKEST scheme, with a reduced accuracy in time, is unstable for the case of pure advection. The modified 2-D explicit QUICKEST, ADI-TOASOD and ADI-QUICK schemes have been developed herein and proved to be numerically stable, with the bility sta- region of each derived 2-D scheme having also been established. All these derived 2-D schemesh ave been tested in a 2-D domain for various initial solute distributions with both uniform and rotational flow fields. They were further tested for a number of 2-D continuous discharge cases, with the corresponding exact solutions having also been derived herein. All the numerical tests in both the 1-D and 2-D cases were compared with the corresponding exact solutions and the results obtained using various other difference schemes, with the higher order schemes generally producing more accurate predictions, except for the characteristic based schemes which failed to conserve mass for the 2-D rotational flow tests. The ADI-TOASOD scheme has also been applied to two water quality studies in the U. K., simulating nitrate and faecal coliform distributions respectively, with the results showing a marked improvement in comparison with the results obtained by the second order central difference scheme. Details are also given of a refined numerical representation of flooding and drying of tidal flood plains for hydrodynamic modelling, with the results showing considerable improvements in comparison with a number of existing models and in good agreement with the field measured data in a natural harbour study.

Heterogeneities in fractured rock are found at all scales; from the scale of individual fractures, to the scale of fracture networks, and to the largest regional scales. These heterogeneities cause challenges for modelling and parameter estimation of flow and solute transport. The heterogeneities in fracture aperture, characterization of the flow channelling they are causing, and implementation of this information into numerical simulation models of the solute transport in fractured media are the subjects of this thesis. Aperture variability within a fracture causes the flow channelling, where the water flow is focused in a few channels and other areas of the fracture have practically stagnant water. The flow-wetted surface is the area where the flowing water is in contact to the fracture area. Contaminants are transported with the flowing water and therefore the flow-wetted surface is an important parameter that influences the diffusion into the rock matrix and sorption to the fracture rock surface. The specific flow-wetted surface (sFWS) is the flow-wetted surface divided by the total fracture area. The sFWS is systematically analyzed for different fracture aperture distribution characteristics. The local aperture is linked to the local hydraulic conductivity K. Increasing standard deviation of the hydraulic conductivity K field (σln K) leads to decreased sFWS. The sFWS is found to be independent of the correlation length (λ) of the field. An empirical relationship is developed, which describes the sFWS as a function of the σln K. A method is also introduced to determine this key parameter by analysis of the breakthrough curve from a single-well injection-withdrawal (SWIW) test. Further, an approach is presented to incorporate the effect of fracture level heterogeneity into fracture network models and to analyze the effect on sorption and matrix diffusion, by including the sFWS parameter into the transport calculations. The results show that the median transport time is proportional to the square of the sFWS-value. The results also suggest that there are an averaging behaviour in the fracture network, the sFWS-value of each individual fracture is not important for the transport over the domain, but a mean-value can be utilized in the numerical model.
Heterogeniteter i sprickigt berg finns i alla skalor, från millimeterskala till en skala på hundratals kilometer. Dessa heterogeniteter orsakar problem vid beräkning av vattenflöde och ämnestransport. Aperturen i en spricka är öppningen mellan de två omslutande bergsidorna, den varierar både inom och mellan olika sprickor. Ämnet för denna avhandling är heterogeniteter i aperturerna inom enskilda sprickor, karaktärisering av den flödeskanalisering som uppstår på grund av dessa heterogeniteter och hur man kan använda denna information till en numerisk modell.Variabilitet av aperturen i en enskild spricka gör att vattenflödet blir fokuserat i ett fåtal kanaler, medan andra områden av sprickan kan ha praktiskt taget stillastående vatten. Den flödesvätta ytan är det område där det strömmande vattnet kommer i kontakt med sprickytan. Den flödesvätta ytan som påverkar diffusionen in i bergmatrisen och sorptionen till sprickytan är en viktig parameter eftersom föroreningar transporteras med det strömmande vattnet. Den specifika flödesvätta ytan (sFWS) är den flödesvätta ytan dividerad med den totala sprickarean. I avhandlingen analyserades sFWS systematiskt för olika statistik över sprickaperturen. Den lokala aperturen är kopplad till den lokala hydrauliska konduktiviteten K. En ökad standardavvikelse för det hydrauliska konduktivitetsfältet (σln K) ledde till minskad sFWS. sFWS visades vara oberoende av konduktivitetsfältets korrelationslängd (λ). En empirisk relation utvecklades som beskriver sFWS som en funktion av σln K. Ett SWIW-test är en typ av spårämnesförsök, där ett spårämne injiceras i en brunn följt av vatten i en bestämd tidsperiod, innan flödet vänds och en genombrottskurva registreras. Testet används traditionellt för att bestämma bergets diffusions- och sorptionsegenskaper. En metod presenterades för att bestämma den specifika flödesvätta ytan genom analys av genombrottskurvan för ett SWIW-test. Ett tillvägagångssätt introducerades för att analysera effekterna av sorption och matrisdiffusion i heterogena sprickor i en spricknätverksmodell genom att inkludera sFWS-parametern i transportberäkningar. Resultaten visade att medianvärdet för transporttiden är proportionell mot kvadraten på sFWS-värdet. Resultaten visade också att transporten genom spricknätverket inte är beroende av sFWS-värdet i de individuella sprickorna, utan att medelvärdet kan användas för modellering.

The environmental sanitation situation in Kampala’s peri-urban areas was reviewed and investigated through field studies, structured interviews with personnel from key institutions and administration of questionnaires to households in a selected peri-urban settlement (Bwaise III Parish).  In this settlement, specific field and laboratory measurements were undertaken so as to create a better understanding of the environmental sanitation situation, anthropogenic pollution loads and their transport and impact (with a focus on Phosphorus) in Kampala’s Peri-urban areas in pursuit of interventions for improving the environmental sanitation and protecting the shallow groundwater resource there. The review revealed that the urban poor in Kampala, like elsewhere in developing countries, are faced with inadequate basic services caused by a combination of institutional, legal and socio-economic issues and that the communities’ coping strategies are in most cases detrimental to their health and well-being. Field surveys showed that excreta disposal systems, solid waste and greywater are major contributors to the widespread shallow groundwater contamination in the area. Field measurements revealed that the water table responds rapidly to short rains (48 h) due to the pervious (10-5-10-3 m/s) and shallow (<1 mbgl) vadose zone, which consists of foreign material (due to reclamation). This anthropogenically influenced vadose zone has a limited contaminant attenuation capacity resulting in water quality deterioration following rains. The only operational spring in the area is fed by regional baseflow meaning a wider protection zone. The spring discharge exhibited microbial quality deterioration after rains primarily as a result of poor maintenance of the protection structure. Subsurface phosphorus (P) transport mechanisms appeared to be a combination of adsorption, precipitation, leaching from the soil media and through macropore flow with the latter two playing an important role in the wet season. The Langmuir isotherm described the phosphorus sorption data well (R2³ 0.95) and the best prediction of Langmuir sorption maximum (Cmax) had organic carbon, Ca and available phosphorus and soil pH as significant predictors. Loosely bound P (NH4Cl-P) was the least fraction (<0.4% of total P) in all layers indicating a high binding capacity of P by the soils implying that the soils have a capacity to adsorb additional P loads. Simulation results from the preliminary numerical model built in this study based on field and laboratory measurements indicate that rainfall infiltration rates > 7x10-3 mm/s drive shallow groundwater contamination with higher intense rains of relatively longer duration (³ 70 mm within 48 h) reducing phosphorus transport. Sensitivity analysis of the model input with respect to how long it takes to pollute the subsurfacehad the phosphorus sorption coefficients as being more influential than the pore size and air entry values. There are however, key contrasts between the model simulations and field observations which are useful in guiding new efforts in data collection. The study reveals that intervention measures to improve the environmental sanitation and protect the shallow groundwater in the peri-urban settlements are of a multidisciplinary nature necessitating action research with community participation.
QC 20100917

Up-to-date methods of numerical modelling of random fields were applied to investigate some features of solute transport in saturated porous media with stochastic hydraulic conductivity. The paper describes numerical experiments which were performed and presents the first results.

Up-to-date methods of numerical modelling of random fields were applied to investigate some features of solute transport in saturated porous media with stochastic hydraulic conductivity. The paper describes numerical experiments which were performed and presents the first results.

Developing low-cost and effective technologies to upgrade phosphorus (P) removal from the catchment runoffs and rural wastewater treatment facilities is one of the main research agendas to save the Baltic Sea from eutrophication. In Sweden, the construction of the constructed wetlands has been one of the environmental objectives for wastewater quality improvement in the small communities. However, the insufficiently understanding of the mechanisms underlying the process of phosphorus mobility and sorption in the constructed wetlands has limited design of the effective constructed wetlands. To provide the better understanding of sorption process in the catchment and constructed wetland system, this thesis used the GIS-based Soil and Water Assessment Tool (SWAT) to predict phosphorus mobility and identify the critical diffusing sources of phosphorus loss in the Oxunda catchment (Paper I). Then, the study developed the three-dimensional numerical Reactive TRAnsPort Model (RETRAP - 3D) in the COMSOL Multiphysics® for evaluating the long - term sorption processes and removal efficiencies of the porous reactive media for upgrading the performance of constructed wetlands (Paper II and III). The latter model coupled many physics equations to solve process of water flow, reaction kinetics and solute transport in the porous reactive adsorbent media for application in the constructed wetlands. The data from the field measurements and column experiments have been used to demonstrate the model simulation accuracy to capture the process of phosphorus sorption in the real environment. Modeling results ranked the phosphorus removal efficiency of the adsorbent media as follows: Polonite® (88 %), Filtralite P® (85%), BFS (62%), Wollastonite (57 %). The satisfactory agreement which obtained between the simulated outputs and measured data confirmed that the SWAT and RETRAP-3D are useful tools for describing various processes in the complicated system. However, further study is required to generate and validate more experimental data to evaluate the sensitivity of local parameters.

This reserch project was finacially supported by Lars Erik Lundberg scholarship foundation for projectnumber (2015/34 and 2016/12), ÅkeochGreta Lissheds Stiftelsen for project number (2015-00026), J.Gust. Richert Stiftelsen and Ecopool researchproject for smart and sustainable environment. QC 20170523

In order to understand the processes involved in water and steam floods during secondary and enhanced oil recover, waste disposal, in-situ mining and leaching, or many different types of geological phenomenona, the chemical interactions between the fluid and the surrounding minerals must be known as a function of pressure, temperature and composition. These systems are generally open systems, thus the changes in pressure, temperature and bulk composition are coupled to the chemical reactions occurring throughout the entire system and cannot be independently specified. Based on the equations of mass action and mass balance, further equations have been derived which allow chemical reactions between a fluid and solid phases to be evaluated. The equations are based on the derivatives of the mass action and mass balance equations with respect to time, and are used in a series expansion to predict the composition of the fluid and the solid phases at future times. The equations are coupled to those constraining pressure, temperature and mass flux-which have been modified to allow this coupling. Because of various limitations on many of the equations used, only a single fluid in porous media can be modelled. A computer program has been written to test the equations and concepts developed in this thesis. The results allow the following generalization for natural flow systems with decreasing pressure and temperature along the flow path to be made. Excluding systems with sufficient mechanical energy to create new flow paths and excluding all phases which exhibit decreasing solubility with increasing temperature or with decreasing pressure, every natural flow system which attempts to maintain equilibrium between the fluid and solid phases in contact with the fluid will ultimately seal itself.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

In the recent decades, therehave been frequent conflicts between groundwater waterresources and environmentally hazardous activities. Newmethodologies for aiding decision-making in groundwater impactassessment and protection areneeded and in which issues ofincreased awareness, better understanding of the groundwaterresources processes, and validation of predictive mathematicalmodels are addressed.

A framework fordecision–aid, based on predictive simulations that a)predicts the environmental impacts b) provides the totaleconomical value c) visualises the impacts and the groundwaterproperties and d) describes the uncertainties in the results isproposed herein. The framework can be applied in environmentalimpact assessments, strategic environmental assessments andprotection and management of water resources. The results ofthe model are used as feedback for determining new scenarios,depending on the required uncertainties, and if the plannedactivity is sustainable, and/or fulfils the legislative andpolicy measures. This framework is applied to a particular casestudy, Nybroåsen, in the south-eastern part of Sweden,where the highway E22 is constructed through the importantglaciofluvial esker aquifer, passing the protection zone of thewater supply for the Kalmar municipality.

The impacts from the new highwayand the existing road have been predicted by two-dimensionalphysically based time-variant flow and solute groundwatermodelling. The results, breakthrough curves of contaminantconcentration in wells and maps of concentration distributions,as well as travel times, flow paths, and capture zones forwells determined by particle tracking have been presented.

The constructed model of theNybroåsen study area was calibrated by comparing observedand simulated groundwater levels for 15 observation wells forten years of measurements. The model has been evaluated bothgraphically and numerically and the calibration target wasfulfilled for 13 of the 15 observation wells. The model workincludes investigations of the catchment information, a waterbalance study, simulation of the groundwater recharge,consideration of the unsaturated zone by a numerical columnsimulation, and sensitivity analysis.

From the sensitivity analysis ofthe flow and transport parameters, it has been shown that theuncertainties are mainly due to the hydraulic conductivity.Comparison of the derived conductivity from the steady-stateautomatic calibration and the time-variant calibration showedthat there are major differences in the derived parameters,which illustrates the importance of a time dependentcalibration over both wet and dry periods and in more than onepoint in the area of interest of the model predictions.

In addition, a multi-criteriadecision analysis has been carried out for four roadalternatives (including the new highway E22) and the existingroad in the case study concerned. The multi-criteria decisionaid is applied as an illustration of how it can be used in thestudy area to identify a) interest groups of actors and theirconcerns b) ranking of alternative road scenarios according toactors’preferences and c) coalition groups of actorsi.e.groups that have similar views with regard to theroad alternatives.

Keywords:Physically-based groundwater modelling,contamination, flow and solute transport, glaciofluvialdeposits, Nybroåsen, Sweden, and multi-criteriadecision-aid.

Die Modellierung von komplexen Systemen, wie dem Untergrund, ist ein Hilfsmittel zur Beschreibung der in der Realität ablaufenden Prozesse. Die Durchführung von Experimenten an einem Modell, um qualitative Aussagen über ein reales System zu erhalten, wird als Simulation bezeichnet. Dabei können vielfältige Modelle, wie z.B. physikalische und mathematische, zum Einsatz kommen. Die ungesättigte Bodenzone (vadose Zone) bezeichnet den Bereich zwischen der Landoberfläche und dem Grundwasserspiegel, innerhalb dessen der Wassergehalt geringer als bei Vollsättigung, und der Druck geringer als der Atmosphärendruck ist. Dieser Bodenbereich hat für die Landwirtschaft, Geobiologie, aerobe Abbauprozesse und Grundwasserneubildung eine große Bedeutung. Für die Nachbildung von Strömungs- und Stofftransportprozessen der ungesättigten Bodenzone existieren numerische Simulationsprogramme. Ziel der vorliegenden Arbeit ist eine umfangreiche Validierung des Programms PCSiWaPro® (entwickelt an der TU-Dresden, Institut für Abfallwirtschaft und Altlasten) für unterschiedliche Anwendungsfälle. Ein weiteres Ziel der Arbeit besteht in der Untersuchung der Anwendbarkeit des aktuellen Stands des Simulationsprogramms PCSiWaPro® auf unterschiedliche Praxisfälle bei Kombination der ungesättigten Bodenzone mit technischen Anlagen. Vier Anwendungsfälle mit unterschiedlichen Zielen wurden dafür im Rahmen dieser Arbeit untersucht: die Simulation von dezentraler Abwasserversickerung (Kleinkläranlage - KKA) anhand entsprechender Säulen- und Feldversuche, die Berechnung der Grundwasserneubildung am Beispiel von Lysimetern, der Wasserhaushalt von Erddämmen und die Modellierung von Deponieabdeckungssystemen. Die Anwendungsfälle unterscheiden sich durch den Zweck der Simulation, die Geometrie, die Größe, die festgelegten Anfangs- und Randbedingungen, die Simulationszeit, die Materialien, das Koordinatensystem sowie die Ein- und Ausgabewerte. Die Simulationsergebnisse konnten eindeutig zeigen, dass das Programm PCSiWaPro® für alle im Rahmen der vorliegenden Arbeit untersuchten Fälle, mit unterschiedlichen Strömungsregimen, Stofftransport-Parametern, Randbedingungen, Koordinatensystemen sowie Raum- und Zeitdiskretisierungen anwendbar ist. Die Simulationsergebnisse der Säulenversuche am Beispiel dezentraler Abwasserversickerung zeigten eine sehr gute Übereinstimmung zwischen gemessenen und mittels PCSiWa-Pro® berechneten Werten des Wasser- und Stoffhaushaltes (Druckhöhe, Abfluss und Stoff-konzentration) der untersuchten Bodentypen B3 (schwachschluffiger Sand), B4 (Grobsand) und B5 (mittelschluffiger Sand). Die Wurzel des mittleren quadratischen Fehlers (RMSE) betrug für die Berechnung der Druckhöhe 1,84 cm bei B5, 3,61 cm bei B3 und 1,27 cm bei B4. Die relative Abweichung betrug für die Berechnung der Druckhöhe 2,19 % bei B5, 1,3 % bei B3 und ca. 5,3 % bei B4. Die Durchführung der Sensitivitätsanalyse der für die Modellierung relevanten Parameter zeigte eine sehr hohe Sensitivität der VAN GENUCHTEN-Parameter und der gesättigten hydraulischen Leitfähigkeit des Bodens. Darüber hinaus führten die Parameter nach DIN 4220 und die mithilfe von Pedotransferfunktionen aus Siebanalysen genommenen Parameter zu unterschiedlichen Ergebnissen. Im Rahmen des am Institut für Abfallwirtschaft und Altlasten durchgeführten Projektes EGSIM wurden die Programme SENSIT und ISSOP (in Zusammenarbeit mit DUALIS GmbH IT Solution) entwickelt und zur Parameteridentifikation/-kalibrierung benutzt. Die im Rahmen dieser Arbeit erzielten Ergebnisse konnten nachweisen, unter welchen Bedingungen eine Nachklärung des vollbiologisch gereinigten Abwassers innerhalb der Bodenzone möglich ist, so dass am Ort der Beurteilung (Grundwasseroberfläche) kein unzulässiger Schadstoffeintrag erfolgt. In Bezug auf die KKA-Feldmodelle ist die Anwendung des rotationssymmetrischen Koordinatensystems als Voraussetzung der Realität besser zu entsprechen und nicht als Option zu betrachten. Darüber hinaus wurden anhand der Feldmodelle verschiedene Szenarien mit kontinuierlicher und diskontinuierlicher Versickerung sowie zwei unterschiedlich großen Einleitflächen durchgeführt. Das Programm PCSiWaPro® ist sowohl für ungesättigte als auch für variabel-gesättigte porösen Medien anwendbar. Dies wurde im Rahmen der Simulation des Wasserhaushaltes eines Erddamms nachgewiesen. Die durchschnittliche relative Abweichung zwischen gemessenen und mittels PCSiWaPro® berechneten Wasserständen des entsprechenden Beobachtungspunkts im untersuchten Dammkörper lag bei 0,08 % (entspricht 5,8 cm bei einer Müchtigkeit von ca. 70 m) und das Bestimmtheitsmaß (R2) betrug 0,987. Die Simulation des Wasserhaushaltes unterschiedlicher Deponieabdichtungssystemen mittels PCSiWaPro® zeigte im Allgemeinen ein funktionierendes Ableiten des auf Deponien anfallenden Regenwassers (auch bei Starkregenereignissen). Darüber hinaus haben die durchgeführten Bewuchs-Modelle nachweisen können, dass die Vegetation der Deponieoberflächen den Wassergehalt, durch Pflanzenwurzelentzug bzw. Evapotranspiration, reduzieren können. Die Simulationsergebnisse der durchgeführten Szenarien des Wasserhaushaltes von Lysimetern zur prognostischen Berechnung der Grundwasserneubildung mittels PCSiWaPro® konnten nachweisen, dass das Programm für die Berechnung der Grundwasserneubildungsrate für diesen Zweck anwendbar ist. Die relativen Abweichungen der be-rechneten von den gemessenen Grundwasserneubildungsraten sind auf die verwendeten Materialparameter sowie auf Vernachlässigung der möglicherweise in Lysimetern sich befin-denden Makroporen (duale Porosität) zurückzuführen
The modelling of complex systems such as the underground is a means to describe the processes occurring in the reality. The conducting of experiments on a model to obtain qualitative evidence about a real system is referred to as a simulation. Thereby, various models (e.g. physical and mathematical models) can be used. The unsaturated zone (vadose zone) is the region between the land surface and the water table, in which the water content is less than full saturation, and the pressure is lower than the atmospheric pressure. The unsaturated zone is very significant for agriculture, geobiology, aerobic degradation processes and groundwater recharge. The processes of water flow and solute transport in the unsaturated zone can be described by means of numerical simulation programs. The aim of the present work is a comprehensive validation of the simulation program PCSiWaPro® (developed at the TU-Dresden, Institute of Waste Management and Contaminated Site Treatment) for different applications. Another aim of this work is to investigate the applicability of the current version of PCSiWaPro® for different cases of a combination between the unsaturated zone and technical facilities. Four application cases with different objectives were investigated within the present work, which are: the simulation of decentralized wastewater infiltration with corresponding column and field experiments, the computation of groundwater recharge by means of lysimeters, the water balance of earth dams and the modelling of landfill covering systems. The application cases differ from each other by the objective of the simulation, the geometry, the size, the specified initial and boundary conditions, the simulation time, the applied materials, the coordinate system, the input and output data. The simulation results clearly showed that PCSiWaPro® is applicable for all investigated cases under consideration of different flow and solute transport regimes, parameters, boundary conditions, spatial and temporal discretization, and coordinate systems. The simulation results of the experimental soil columns for the decentralized treated wastewater infiltration case showed a very good agreement between measured and computed values of water and solute balance (pressure head, flow and solute concentration) of the investigated soil types B3 (slightly silty sand), B4 (coarse sand / gravel) and B5 (medium silty sand). The root of the mean squared error (RMSE) for the computation of the pressure head was 1,84 cm at B5, 3,61 cm at B3 and 1,27 cm at B4. The relative deviation in case of pressure head computation was 2,19 % at B5, 1,3 % at B3 and 5,3 % at B4. The implementation of the sensitivity analysis of the relevant parameters for the modelling showed a very high sensitivity of the VAN GENUCHTEN parameters and the saturated hydraulic conductivity of the soil. Moreover, the parameters according to DIN 4220 led to different results than the estimated ones according to pedotransfer methods based on sieve analysis. Within the project EGSIM, which was carried out at the Institute for waste management and contaminated sites treatment in collaboration with DUALIS GmbH IT Solution, the programs SENSIT and ISSOP were developed and used for parameter identification/ calibration. The results obtained in this Work showed under which conditions is a secondary treatment of full biologically treated wastewater in the soil possible, so that no unallowable pollutants entry in the groundwater occurs. With regard to the field models of this application the implementation of the rotationally symmetric coordinate system should be considered as a condition and not as an option for a better corresponding to the reality. Furthermore, different scenarios of the field models were carried out with continuous and discontinuous infiltration, as well as under different initiation areas. PCSiWaPro® could be applied for both unsaturated and variably-saturated porous media. This could be proven by the simulation of the water balance in an earth dam. The average relative deviation between measured and simulated water levels of the corresponding observation point in the investigated dam embankment was 0,08 % (corresponding to 5,8 cm at 70 m thickness) and the coefficient of determination (R2) was 0,987. In general, the simulation of the water balance using PCSiWaPro® of different landfill covering systems showed a successful draining of the falling rainwater (even under heavy rainfall). In addition, the implemented vegetation models have proven that the vegetation of the landfill surface can reduce the water content in the landfill by evapotranspiration and water uptake by roots. The water balance simulation results of the scenarios for the computation of groundwater recharge by means of lysimeters showed that the program is applicable for this case. The relative deviation of the simulated from the measured groundwater recharge rates occur due to the implemented material parameters as well as to the neglect of macro pores effects (dual porosity)

Durch die Stilllegung der Kali-Gewinnung und -Produktion zwischen 1990 und 1993 sowie die begonnene Rekultivierung der Kali-Rückstandshalden haben sich die Salzfrachteintragsbedingungen für die Fließgwewässer im "Südharz-Kalirevier" in Thüringen zum Teil deutlich verändert. Aufgrund erheblich geringerer Salzeinträge in die Vorfluter Wipper und Bode ist es möglich geworden, zu einer ökologisch verträglichen Salzfrachtsteuerung überzugehen. Die Komplexität der zugrunde liegenden Stofftransportprozesse im Einzugsgebiet der Wipper macht es jedoch unumgänglich, den Steuerungsvorgang nicht nur durch reine Bilanzierungsvorgänge auf der betrachteten Steuerstrecke zu erfassen (so wie bisher praktiziert), sondern auch die Abflussdynamik im Fließgewässer und den Wasserhaushalt im Gebiet mit einzubeziehen.

Die Ergebnisse dieser Arbeit dienen zum einen einer Vertiefung der Prozessverständnisse und der Interaktion von Wasserhaushalt, Abflussbildung sowie Stofftransport in bergbaubeeinflussten Einzugsgebieten am Beispiel der Unstrut bzw. ihrer relevanten Nebenflüsse. Zum anderen sollen sie zur Analyse und Bewertung eines Bewirtschaftungsplanes für die genannten Fließgewässer herangezogen werden können. Ziel dieser Arbeit ist die Erstellung eines prognosetauglichen Steuerungsinstrumentes, das für die Bewirtschaftung von Flusseinzugsgebieten unterschiedlicher Größe genutzt und unter den Rahmenbedingungen der bergbaubedingten salinaren Einträge effektiv zur Steuerung der anthropogenen Frachten eingesetzt werden kann.

Die Quellen der anthropogen eingeleiteten Salzfracht sind vor allem die Rückstandshalden der stillgelegten Kaliwerke. Durch Niederschläge entstehen salzhaltige Haldenabwässer, die zum Teil ungesteuert über oberflächennahe Ausbreitungsvorgänge direkt in die Vorfluter gelangen, ein anderer Teil wird über die Speichereinrichtungen gefasst und gezielt abgestoßen. Durch Undichtigkeiten des Laugenstapelbeckens in Wipperdorf gelangen ebenfalls ungesteuerte Frachteinträge in die Wipper. Ein weiterer Eintragspfad ist zudem die geogene Belastung.

Mit Hilfe detaillierter Angaben zu den oben genannten Eintragspfaden konnten Modellrechnungen im Zeitraum von 1992 bis 2003 durchgeführt werden. Durch die Ausarbeitung eines neuartigen Steuerungskonzeptes für das Laugenstapelbecken Wipperdorf, war es nun möglich, die gefasste Haldenlauge entsprechend der aktuellen Abflusssituation gezielt abstoßen zu können. Neben der modelltechnischen Erfassung der aktuellen hydrologischen Situation und der Vorgabe eines Chlorid-Konzentrationssteuerzieles für den Pegel Hachelbich, mussten dabei weitere Randbedingungen (Beckenkapazität, Beckenfüllstand, Mindestfüllstand, Kapazität des Ableitungskanals, usw.) berücksichtigt werden.

Es zeigte sich, dass unter Anwendung des Steuerungskonzeptes die Schwankungsbreite der Chloridkonzentration insgesamt gesehen deutlich verringert werden konnte. Die Überschreitungshäufigkeiten bezüglich eines Grenzwertes von 2 g Chlorid/l am Pegel Hachelbich fielen deutlich, und auch die maximale Dauer einer solchen Periode konnte stark verkürzt werden. Kritische Situationen bei der modelltechnischen Frachtzusteuerung traten nur dann auf, wenn Niedrigwasserverhältnisse durch die Simulationsberechnungen noch unterschätzt wurden. Dies hatte deutliche Überschreitungen der Zielvorgaben für den Pegel Hachelbich zur Folge.

Mit Hilfe des Steuerungsalgorithmus konnten desweiteren auch Szenarienberechnungen durchgeführt werden, um die Auswirkungen zukünftig zu erwartender Salzfrachten näher spezifizieren zu können. Dabei konnte festgestellt werden, dass Abdichtungsmaßnahmen der Haldenkörper sich direkt positiv auf die Entwicklung der Konzentration in Hachelbich auswirkten. Durch zusätzlich durchgeführte Langzeitszenarien konnte darüber hinaus nachgewiesen werden, dass langfristig eine Grenzwertfestlegung auf 1,5 g Chlorid/l in Hachelbich möglich ist, und die Stapelkapazitäten dazu ausreichend bemessen sind.
As a consequence of general closure and conversion of potash-industries between the years 1990 and 1993 and due to the beginning of recultivation activities on the potash stockpiles the load of dissolved potassium salt of rivers in the "Südharz-Kalirevier" in the German federal state of Thuringia has considerably changed. The extremely decreased salt inputs into the tributaries of Wipper and Bode were accompanied by a change in salt load management towards a system controlled with respect to river ecology. Due to the high complexity of salt transport processes in the Wipper catchment, the existing operation rules cannot comply with the present requirements, so that a comprehensive knowledge of water balance processes and river flow dynamics have to be included in management strategies.

On the one hand this investigation aims to analyse the processes and the interaction of water balance, runoff generation and solute transport in catchment areas influenced by salt mining activities such as the case in the river Unstrut and its relevant tributaries. On the other hand the results of this study can help to analyse and assess sustainable management plans for the above mentioned river basins. Thus the main objective of this study is to develop an integrated, predictive management tool, that can be applied for catchment areas of different spatial scales and for the effective use of controlled discharge of anthropogenic salt solution taking into account the basic input conditions from salt mining activities.

The most important sources of anthropogenic salt inputs into the river stream are the salt loads from the potash stockpiles near the disused mines. Due to usual precipitation salt solution leaches from the stockpiles, which partly reaches the river streams uncontrolled by lateral interflow processes. Another part is being gathered in reservoirs and than discharged according to special system operation rules. As well dissolved salt loads comes into the Wipper by leakage processes out of the reservoir in Wipperdorf. Furthermore geogenic input is another important emission pathway.

With detailed information about these different emission pathways, model simulations were performed within the period from 1992 to 2003. After the technical implementation of a new management strategy for the reservoir in Wipperdorf, now it was possible to push off the stored lye according to the actual runoff situation in the river stream. Beside a fully modell aided description of the whole actual hydrological situtation and provided control values for chloride concentration at the gauging station in Hachelbich, also other boundary conditions had to be considered for this purpose (such as reservoir capacity, actual fill level, minimum fill level, drain capacity etc.).

It turned out, that the application of the new management strategy led to a clear decreased range in chloride concentration. Frequencies of exceeding a critical value of 2 g chloride/l at gauging station in Hachelbich enormously declined and the maximum duration of such periods could rigorously be shortened. Particluar critical situations in calculating potential lye discharge only occured when measured flow discharge was underestimated through model simulations. In this case control values for the gauging station in Hachelbich could not be achieved.

With this new management tool scenario simulations were executed to analyse the effects of expected amounts of lye in future. These theoretical studies showed the decreasing trend in chloride concentration if restorations measures at the stockpiles would be continued. Longterm scenario runs also showed, that a threshold value of 1,5 g chloride/l in Hachelbich could be achieved and existing storage capacities therefor will be sufficiently dimensioned.

La tomographie de résistivité électrique (ERT) est une méthode courante géophysique de terrain, souvent utilisée pour détecter et l’évolution suivre les panaches de polluants en zone saturée. L’ERT est cependant une méthode intégratrice dont la fiabilité des modèles est confronte aux problèmes de non unicité des solutions du problème inverse. Ces contraintes limitent l’interprétation des modèles a un aspect qualitatif de la distribution des contrastes de résistivité modélises en 2D ou 3D, résultant du choix des paramètres d’inversion et de l’association de paramètres du milieu non identifiables a l’échelle du volume poreux.Cette thèse propose de tester la faisabilité de la méthode pour quantifier les paramètres de transport de polluants et de solutés miscibles au contact des eaux souterraines, ainsi que la sensibilité des paramètres d’inversion les plus influents sur la modélisation.Les tests expérimentaux sont réalisés en laboratoire sur des empilements 2D de billes de verre sphériques (de l’ordre de la 100èn de μm) dans un réservoir en plexiglas transparent. Deux réseaux verticaux de 21 électrodes sont disposes sur les bords latéraux du réservoir pour effectuer le suivi ERT du traceur sale (NaCl dissout) a partir de 210 points de mesures en dipôle-dipôle transverse acquis toutes les 5 minutes afin d’optimiser la résolution temporelle. Le dispositif est également dispose face a un panneau lumineux permettant de réalise un suivi vidéo simultané du colorant.L’analyse vidéo révèle une propagation plus rapide du colorant sur les bords latéraux qui reste somme toute négligeable pour les débits a la pompe les plus faibles. En revanche les mesures ERT sont fortement perturbées par les effets résistant de la cellule plexiglas qui se répercutent sur les modèles. La normalisation des mesures de résistivité apparente à partir d’une série acquise à l’état initial permet de les atténuer fortement.La modélisation est particulièrement sensible au choix du maillage, aux normes appliques (L1 ou L2) sur les données et les paramètres, et au facteur d’amortissement _. Des valeurs trop élevées de _ et du facteur d’acceptance tendent à lisser les contrastes au niveau du front de dispersion et augmentent l’impact des effets des bords horizontaux sur D et _. A l’inverse, une modélisation contrainte par de faibles valeurs de α et du facteur d’acceptante donne des résultats plus proches l’analyse vidéo, mais produit des effets de bosses à l’avant et à l’arrière du front.La vitesse interstitiel u est indépendante du choix des paramètres d’inversion pour l’ERT. Pour les deux méthodes u est toujours inférieure au débit impose par la pompe, dont le décalage est exprimé par le facteur retard Rf . Les effets de retard résultent de l’adsorption du Na+ sur les surfaces des billes de verre chargées négativement qui retarde le front de dispersion du suivi ERT. Pour le suivi vidéo, la taille importante de la molécule du colorant favorise son piégeage dans les zones ou la perméabilité est plus faible, en plus d’une éventuelle affinité avec la surface solide. Les contrastes de conductivité et la stabilité de l’interface créent par la différence de densité entre les fluides testes ici n’ont pas d’influences significatives sur la dispersion qui est dominée par le débit impose a la pompe. Les estimations du coefficient de dispersion D en fonction du nombre de Péclet sont cohérentes avec la courbe théorique de Bachmat (1968). Cependant la dispersivité α augmente pour les vitesses d’écoulement les plus élevées. Les premières expérimentations de terrain réalises en 2D sur des sables de Fontainebleau présentent l’avantage de s’affranchir des effets de bords inhérents au laboratoire. En revanche la recalibration des données normalisées par la loi de Archie est plus complexe puisqu’il est nécessaire de tenir compte de l’état de saturation de la résistivité des fluides initialement présents. De plus l’erreur importante sur les modèles ne permet pas de déduire une estimation fiable des paramètres de transport u, α (ou D), et Rf
Electrical resistivity tomography is a common geophysical method often used to detect and follow plumepollutants in aquifers. However ERT is an integrative method whose reliability of the models is faced tothe non-unicity of the inverse problem solutions. These constraints limit the interpretation to a qualitativeview of the resistivity contrasts modelled in 2D or 3D, resulting of the chosen inverse parameters and thecombination of several hydrodynamic paramaters related to the poral network.The purpose of this thesis was to test the abilities of the ERT imaging to quantify solute transport parametersin miscible displacement occurred in groundwater and the sensitivity of inverse parameters most affectingthe modelled dispersion front.Laboratory experiments are conducted on glass beads poured into a transparent plexiglas container. Twovertical lines of 21 stainless steel electrodes are fixed on the lateral sides of the container to perform the ERTmonitoring, of the NaCl dissolved in the tracer, from a sequence of 210 quadripole measurements acquiredin transverse dipole-dipole each 5 minutes. A light panel is placed behind the experimental device and avideo follow up of the dyed part of the tracer is acquired from the other side.Video analysis reveal a faster propagation of the dye in contact of the vertical edge, which is negligible forthe lowest flow rates imposed by the pump. In contrast, ERT mesurements are strongly disturbed by theresistant edges of the plexiglas container which affect the resulting models. Normalisation of the apparentresisitivity measurements acquired at the experimental stage and by the Archie’s law strongly tones downthese resistive artefacts.ERT modelling is here particularly sensitive to the grid mesh, the norm (L1 or L2 ) applied on data andparameters, and the damping factor λ. High values of λ and the cutoff factor tend to smooth the resistivityconstrasts in the area of the mixing front and increase the weight of the horizontal edge effects on D andα. While results from inverse modelling constraint by low λ and cutoff factors are much closer to the videoanalysis but with enhanced side slope effects at the rear and the front of the mixing area.The interstitial velocity u is independant of the chosen inverse parameters. For both methods u is alwaysinferior to the flow rate provided by the pump, whose the gap is expressed as a retardation factor Rf . Thisretardation is due to adsorption of Na+ on the beads surfaces, which contributes to delay the dispersionfront followed by ERT. The retardation expressed by the video analysis can be due to the important sizeof the molecule of the dye which is easily slowed down in lower permeability areas, added to an eventualaffinity to the solid surface.The ranges of fluid conductivity contrasts and stability of the interfaces tested here have no influences onthe dispersion which is dominated by the flow velocity u. Estimations of the dispersion coefficient D asfunction of the Péclet is consistent with the theoretical curve of Bachmat (1968) and Bijeljic & al (2004).Field experiments are first conducted in 2D on homogeneous unsaturated sand which is considered as aninfinite half-space. However, data normalisation is much more complicated since the saturation state andthe initial fluid conductivities need to be estimated to calibrate the Archie’s law. Because of the 3D tracerinflitration, the RMS error of 2D-ERT models highlights that the inversion process is not enough constraintby data which does not allow to quantify the transport parameters. 3D experiments were then adaptedto detect and follow plumes of saline tracers injected in the centre of the electrode device. From 3D ERTmeasurements we are able to produce reliable models in order to estimate such transport parameters as themean flow velocity, and transverse and longitudinal dispersivities

The euthropthication of the Baltic Sea is a threat that is beginning to be taken seriously by the governments concerned. In Sweden, regulations concerning the allowed nitrogen (N) concentration in the effluent water from wastewater treatment plants are being tightened up. The Rimbo wastewater treatment plant has been imposed to reduce the annual mean concentration of total N in the effluent water to levels below 15 mg l-1. A more and more common way to reduce the nitrogen level in wastewater is to let the water pass through a wetland. This study investigates the possibility to build this kind of wetland at the outlet of the Rimbo wastewater treatment plant.

A prestudy of the topography, soil characteristics and groundwater flow indicates that the land area in question is well suited for the construction of a wetland. A proposal for the design has been made by using a physically based computer model developed in the PRIMROSE project (PRocess based Integrated Management of constructed and Riverine wetlands for Optimal control of wastewater at catchment ScalE), which is financed by the EU. Analysis of the residence time distribution (RTD) is a tool for understanding wetland design characteristics and can be used for wetland engineering such as optimizing design for best possibleefficiency in nitrogen removal. In order to characterize the performance of a wetland, it is useful to translate the RTD to a key figure representing the treatment efficiency. In this work, two types of such key figures have been used. Key figure 1 gives the hydraulic efficiency and Key figure 2 gives an estimation of the nitrogen retention by an integration of hydraulic characteristics and the chemical transformation of nitrogen.

The results of this study show that constructing a wetland in Rimbo probably would be an efficient way to reduce the nitrogen level at the effluent of the wastewater plant below the limits of the regulations. In addition, a wetland would form a nice place of recreation for the people in Rimbo and also make a good habitat for birds.

Övergödningen i Östersjön är ett problem som uppmärksammas alltmer. Ett led i att minska kvävebelastningen på Östersjön är ökade krav på rening i de svenska kommunala reningsverken. Rimbo avloppsreningsanläggning har blivit ålagd ett riktvärde för totalkväve på 15 mg l-1 i utgående vatten, vilket motsvarar en reningsgrad som inte uppnås idag. Ett alltmer vanligt sätt att minska föroreningshalterna är att anlägga våtmarker i anslutning till reningsverken för att efterpolera spillvattnet. Det här arbetet är en del av en förstudie till en sådan våtmark i Rimbo.

En förundersökning av topografi, jordart och grundvattenflöden indikerar att det område som föreslagits i anslutning till reningsverket i Rimbo lämpar sig väl för ett våtmarksbygge. Förslag till utformning har tagits fram med hjälp av en fysikaliskt baserad modell över vattenströmning, utvecklad inom det EU-finansierade projektet PRIMROSE (PRocess based Integrated Management of constructed and Riverine wetlands for Optimal control of wastewater at catchment ScalE). Analys av vattnets uppehållstidsfördelning ger förståelse för våtmarkens egenskaper och kan därför användas vid t ex optimering av våtmarksdesign med avseende på kväverening. För att på ett enkelt sätt kunna jämföra olika våtmarkers effektivitet är det praktiskt att översätta uppehållstidsfördelningen till ett nyckeltal för reningseffekten. I det här arbetet har två olika sådana nyckeltal beräknats. Det första ger den hydrauliska effektiviteten och det andra bygger på en metod där våtmarkens interna hydraulik integreras med den kemiska omvandlingen av kväve. Nyckeltal 1 ger ett mått på hur stor del av volymen i våtmarken som används för kväverening, medan Nyckeltal 2 ger ett mått på den procentuella kväveavskiljningen.

Den här förstudien visar att en våtmark sannolikt skulle vara ett utmärkt sätt att klara riktvärdet för kvävehalten vid reningsverket i Rimbo. Därutöver skulle en våtmark kunna utgöra ett positivt inslag i landskapet och öka den biologiska mångfalden, inte minst vad gäller fågelliv.

Au fossé rhénan supérieur, dans l'est de la France, le Buntsandstein du Trias inférieur constitue un important réservoir d'eau souterraine et de saumures géothermiques riches en lithium. L'objectif scientifique de cette étude est de comprendre l'architecture de la Formation du Grès Vosgien inférieur (LGV), Buntsandstein moyen ; comment les processus sédimentologiques, à différentes échelles, génèrent des hétérogénéités significatives de perméabilité ; et l'effet de telles hétérogénéités sur les résultats de la modélisation des flux de fluides. L'étude utilise une caractérisation sédimentologique à haute résolution, par le biais de descriptions de profils verticaux, de modèles numériques d'affleurements et d'analyses pétrographiques. Ensuite, les mesures de perméabilité sont couplées aux données sédimentologiques, afin d'identifier différentes échelles de contrôles sédimentaires sur la distribution de la perméabilité. Enfin, un modèle conceptuel hydrostratigraphique réaliste en 2D est généré comme référence, pour évaluer comment différents scénarios de simplification des hétérogénéités impactent la modélisation des flux de fluides, en ce qui concerne le temps de résidence des particules, la macro-dispersivité et l'anisotropie mise à l'échelle.Les résultats indiquent que 93% du LGV est composé de grès déposés par un système fluvial en tresses, avec des indices suggérant que la variabilité du débit était un facteur de contrôle principal de la distribution des faciès sédimentaires et des hétérogénéités. Le modèle de superposition du LGV révèle des périodes où les processus fluviaux étaient absents, et les processus éoliens dominaient le transport et le dépôt des sédiments, constituant 7% de l'épaisseur totale du LGV. Les dépôts éoliens montrent des indications de la présence persistante d'eau dans le système, soit en raison de la montée de la nappe phréatique, soit de crues éphémères.Dans l'association de faciès des chenaux fluviaux, une relation inverse entre les conditions du régime fluvial et la perméabilité de ses faciès est observée. Dans l'association de faciès déposés par le vent et l'eau (WWL), la distribution de la perméabilité est directement influencée par les conditions climatiques, où des feuilles de sable hybrides à faible perméabilité ont été déposées dans des conditions plus humides, et des dunes éoliennes à haute perméabilité dans des conditions plus arides. Cependant, malgré la haute perméabilité des dunes éoliennes, l'architecture des WWL implique un faible potentiel de connectivité. La compaction est le principal processus influençant la perméabilité et la porosité du LGV. Les échantillons avec une proportion plus élevée de lithoclastes et d'argile infiltrée ont enregistré un degré de compaction plus avancé, tandis que les échantillons avec un pourcentage plus élevé de surcroissance de quartz ont montré un degré de compaction moindre. La surimpression diagénétique a affecté les différents faciès de manière distincte, indiquant que les processus et l'architecture sédimentaires primaires régissent la distribution des hétérogénéités de perméabilité dans le LGV. Les données de perméabilité provenant des affleurements ont montré des valeurs médianes jusqu'à trois ordres de grandeur plus élevées que celles des données de subsurface. Cependant, les mêmes faciès, et des tendances similaires des réponses porosité-perméabilité relatives aux différents faciès, sont observées entre les affleurements et les échantillons de forage, mettant en évidence la sédimentologie comme un proxy indispensable pour les études d'hétérogénéité des réservoirs[...]
At the Upper Rhine Graben, in Eastern France, the Lower Triassic Buntsandstein serves as an important reservoir of groundwater and lithium-rich geothermal brines. The scientific objective of this study is to comprehend the architecture of the Lower Grès Vosgien Formation (LGV), Middle Buntsandstein; how sedimentological processes, at different scales, generate significant permeability heterogeneities; and the effect of such heterogeneity in fluid-flow modelling results. The study employs high-resolution sedimentological characterisation, through vertical profile descriptions, digital outcrop model, and petrographic analysis. Subsequently, permeability measurements are coupled with sedimentological data, to identify different scales of sedimentary controls on permeability distribution. Finally, a realistic 2D hydrostratigraphyc conceptual model is generated as a reference, to evaluate how different scenarios of heterogeneity simplification impact fluid-flow modelling, concerning particle residence time, macro-dispersivity and upscaled anisotropy.Results indicate that 93% of the LGV is composed of sandstones deposited by a braided fluvial system, with evidence suggesting that discharge variability was a main depositional controlling factor of sedimentary facies and heterogeneity distribution. The LGV stacking pattern reveals periods when fluvial processes were absent, and aeolian processes dominated sediment transport and deposition, constituting 7% of the total LGV thickness. The aeolian deposits record indications of persistent water in the system, either due to water table rise or ephemeral floods In the fluvial channel facies association, an inverse relationship between fluvial flow regime conditions and the permeability of its facies is observed. In the wind- and water-laid facies association (WWL), permeability distribution is directly influenced by climatic conditions, where low permeability hybrid sand sheets were deposited in more humid conditions, and high permeability aeolian dunes in more arid conditions. However, despite the high permeability of the AD, the architecture of the WWL implies low connectivity potential. Compaction is the main process influencing the permeability and porosity of the LGV. Samples with a higher proportion of lithoclasts and infiltrated clay recorded a more advanced degree of compaction, whereas samples with a higher percentage of quartz overgrowth exhibited a lower degree of compaction. The diagenetic overprint affected the distinct facies differently, indicating that primary sedimentary processes and architecture govern the distribution of permeability heterogeneity in the LGV. Permeability data from outcrops exhibited median values up to three orders of magnitude higher than those from subsurface data. However, the same facies, and similar trends of relative porosity-permeability responses to the distinct facies, are observed between outcrops and borehole samples, highlighting sedimentology as an indispensable proxy for reservoir heterogeneity studies[...]

Reactive transport modelling has wide applications in geosciences. In the field of hydrogeology, it has been utilised to simulate the biogeochemical processes that disperse and degrade contaminants in the aquifer. For geotechnical applications, such as geological CO2 sequestration, the reaction of CO2 with the ambient saline aquifer determines the final success of storage. In a radioactive waste repository, scientists rely on reactive transport models to predict the mobilisation of hazardous radionuclides within space and time. In this work, the multi-component mass transport code OpenGeoSys, was coupled with two geochemical solvers, the Gibbs Energy Minimization Selektor (GEM) and the Biogeochemical Reaction Network Simulator (BRNS). Both coupled codes were verified against analytical solutions and simulation results from other numerical models. Moreover, the coupling interface was developed for parallel simulation. Test runs showed that the speed-up of reaction part had a very good linearity with number of nodes in the mesh. However, for three dimensional problems with complex geochemical reactions, the model performance was dominated by solving transport equations of mobile chemical components. OpenGeoSys-BRNS was applied to a two dimensional groundwater remediation problem. Its calculated concentration profiles fitted very well with analytical solutions and numerical results from TBC. The model revealed that natural attenuation of groundwater contaminants is mainly controlled by the mixing of carbon source and electron donor. OpenGeoSys-GEM was employed to investigate the retardation mechanism of radionuclides in the near field of a nuclear waste repository. Radium profiles in an idealised bentonite column was modelled with varying clay/water ratios. When clay content is limited, Ba-Sr-Ra sulfate solid solutions have a very strong retardation effect on the aqueous radium. Nevertheless, when clay mineral is abundant, cation exchange sites also attract Sr and Ba, thus dominates the transport of Ra.

Actuellement, la Loire, voit sa géodynamique de plus en plus détériorée. Le déficit du transport solide provoque un enfoncement du lit mineur sur plusieurs secteurs du bassin Amont. Ceci a pour conséquence une déstabilisation progressive des ouvrages (digues, ponts) et l'érosion ou le colmatage des berges ainsi qu'une baisse du niveau piézométrique des nappes alluviales. Le traitement de ces problèmes passe par une meilleure connaissance des processus d'érosion et d'incision fluviale, le premier laissant place au second une fois que la couche « alluviale » a été totalement emportée, laissant apparaître un affleurement rocheux dans le lit du cours d'eau. Ce phénomène complexe est actuellement constaté en divers endroits de la Loire, dans la plaine du Forez. Nous proposons trois approches pour l'analyser.La première approche est fondée sur la modélisation numérique utilisant les équations de Barré-Saint-Venant, pour l'écoulement, couplées aux équations d'Exner et de Meyer-Peter Müller pour le transport solide. Ce modèle monodimensionnel permet d'obtenir la côte du fond du lit de la rivière et le flux solide au droit de chaque point de calcul.La seconde approche, mécaniste, consiste à déterminer de façon semi-empirique le taux d'incision du substratum marneux à partir de deux variables majeures: la puissance hydraulique totale et le coefficient d'abrasion en un point donné. La puissance hydraulique est calculée à l'aide d'un modèle hydraulique tandis que le nombre d'abrasion est une propriété mécanique de la marne qui est déterminée à partir d'essais en laboratoire. La troisième approche relève de la géochimie. Elle consiste à déterminer les provenances des matériaux contribuant à la recharge latérale des sédiments, à partir de leurs signatures géochimiques. Ceci a fait l'objet d'analyses en laboratoire sur des échantillons prélevés sur l'ensemble du linéaire entre Grangent et Balbigny. Les résultats obtenus montrent que ces approches indépendantes sont complémentaires et permettent une description à la fois qualitative et quantitative de l'enfoncement du lit de la Loire dans le secteur d'étude
Currently, the Loire river, sees its geodynamic increasingly deteriorated. The deficit of sediment transport causes erosion of the bed on several areas of the basin. This results in a gradual destabilization of structures (dams, bridges), erosion or clogging of banks or a decline in piezometric level alluvial.Treating these problems requires a better understanding of the processes of erosion and river incision, the second succeeding the first, once the alluvial material of the bottom was completely removed, revealing a bed outcrop.This complex phenomenon is currently found in various parts of the Loire river, in the plain of Forez.We propose three approaches for this analysis.The first approach is based on numerical modeling using the equations of Barre-de-Saint-Venant, for flow, coupled with the equations of Exner and Meyer-Peter Müller for sediment transport. This monodimensional model allows the simulation of riverbed changement and sediment discharge, right each calculation point of grid mesh.The second approach is mechanistic and consists of determining the rate of marly bedrock incision by a semi-empirical method by the use of two major variables: the total hydraulic power and an abrasion coefficient. The hydraulic power is calculated using a hydraulic model, while the abrasion coefficient is a mechanical property of the marl which is determined from laboratory tests.The third approach is the geochemistry. It consists in determining the provenance of the materials from tributaries and in the main chanel by analyzing their geochemical signatures. This has been the subject of laboratory tests on samples taken across the linear from Grangent to Balbigny.The results obtained show that these independent approaches are complementary and provide both a qualitative and quantitative description of the incision of the Loire river in the study area

Cette thèse valorise les données de mesure en continu de pluie de débit et de turbidité, ainsi que les bases de donnée de résultat d'analyse et les connaissances acquises dans le cadre des trois observatoires français en hydrologie urbaine, OPUR-Paris, OTHU-Lyon et ONEVU Nantes, pour valider et améliorer les connaissances sur les flux et les sources de particules vectrices de contaminants, en réseaux d'assainissement unitaire. Les données provenant de 6 sites expérimentaux drainés par un réseau d'assainissement unitaire ont été exploitées : Marais, Quais et Clichy à Paris, Cordon Bleu et Saint-Mihiel à Nantes et Écully à Lyon, avec sur chaque site des bases de données de longue durée qui ont permis des études statistiques sur des échantillons de plusieurs dizaines d'événements pluvieux et de journées de temps sec. Cette thèse a permis : 1- d'évaluer la représentativité de la turbidité pour analyser du transport solide en réseau ; 2- d'analyser et de modéliser statistiquement les concentrations et les masses de particules à l'échelle événementielle ; 3- d'étudier la dynamique des flux et des concentrations à l'échelle intra-événementielle. Les résultats obtenus indiquent d'une part, que la turbidité permet de décrire les dynamiques intra-événementielles des flux et des concentrations à condition d'exprimer ceux-ci sous forme relative, normalisée par les valeurs moyennes événementielles. En revanche, ces valeurs événementielles sont attachées par des erreurs systématiques non négligeables induites par les variations inter-événementielles de la relation MES-Turbidité (intervalle de confiance de l'ordre de 30% de la moyenne). Ils confirment d'autre part que la contribution des dépôts aux flux de temps de pluie est importante mais variable (entre 20 et 80% de la masse à l'exutoire selon l'événement), y compris sur un site réputé exempt de dépôts (grossiers). Autrement dit, les problématiques d'ensablement et de pollution de temps de pluie ne sont pas nécessairement liées. L'autre contribution majeure est celle des eaux usées « de temps sec ». De plus, ils nous ont permis de progresser dans la compréhension des phénomènes de décalage temporel entre hydrogramme et pollutogramme et d'effet piston
This thesis exploits continuous measurement of rainfall, discharge and turbidity data and the knowledge acquired by three French observatories in urban hydrology, OPUR-Paris, OTHU Lyon and ONEVU-Nantes, to validate and improve knowledge on suspended solids discharges and sources of particles, which are major vectors of contaminants in combined sewer systems. Data from six experimental sites served by a combined sewer system were used: Marais, Quais and Clichy in Paris, Cordon Bleu and Saint-Mihiel in Nantes and Ecully in Lyon. At each site, a long duration databases enabled statistical studies on samples of several tens of rainfall events and dry weather days. This thesis allowed: 1-to assess the representativeness of turbidity to analyze sediments transport in network; 2-to analyze and model concentrations and masses of particles at the scale of rain events; 3-to study the dynamics of fluxes and concentrations at intra-event scale. Results show that turbidity can describe the dynamics of intra-event fluxes and concentrations provided these are expressed in a relative form, normalized by the event mean values. However, these mean values are attached by significant systematic errors induced by variations of the inter-event TSS-turbidity relationship (95% confidence interval about 30% of average). The contribution of sewer deposits to wet weather suspended solids discharges is important but variable (between 20 and 80% of the mass at the outlet depending on the event), including for a site allegedly free of (coarse) sewer deposits. In other words, the problems of silting and contribution from deposits to wet weather pollution are not necessarily related. The other major contribution is from “dry weather” wastewater. In addition, they we made some progress in understanding the lag-time phenomena between hydrograph and pollutograph and the piston effect

Barrages de corrections torrentielles et plages de dépôts jouent un rôle clés dans la protection contre les crues des torrents. Leurs gestionnaires ont pour mission de réduire les risques d'inondations, mais doivent désormais aussi minimiser les impacts environnementaux liés aux ouvrages de protection. Ceci nécessite une meilleure compréhension des effets des barrages de corrections torrentielles et des plages de dépôts sur le transport sédimentaire des torrents. Cette thèse s'inscrit dans cet objectif et se décompose en deux parties. Sa section sur l'état de l'art présente: i) les différents effets des barrages de correction torrentielle sur la production et le transfert sédimentaire; ii) des descriptions des processus hydrauliques et de sédimentation ayant lieu dans les plages de dépôts; et iii) les processus liés à la production et au transfert de bois d'embâcle. Une nouvelle méthode de quantification de la production sédimentaire des torrents complète cet état de l’art.La seconde partie de cette thèse présente le travail réalisé en banc d’essai expérimental. Une première série d’expérience a permis de mettre en évidence un transport par charriage plus régulier lorsque des barrages de correction torrentielle sont ajoutés à un bief alluvial. Une seconde série d’essais a été réalisée sur un modèle générique de plage de dépôt dans l’objectif d’en caractériser les écoulements. Pour cela, une nouvelle procédure de mesure et de reconstruction par approche inverse a été développée. Il en résulte une description des caractéristiques d’un écoulement proche du régime critique, ainsi que des mécanismes de rétrocontrôle entre morphologie et hydraulique pendant la phase de dépôt
Check dams and open check dams are key structures in torrent hazard protection. Their managers must mitigate flood hazards, but now must also minimize the environmental impacts of these protection structures. This requires to improve the knowledge on the effects of check dams and open check dams on the sediment transport, and this thesis forms a contribution towards this end.The section on the current state of research reviews i) the diverse effects of check dams on sediment production and transfer; ii) descriptions of the hydraulics and sedimentation processes occurring in open check dams; and iii) woody debris production and trapping processes. This state of the art is completed with proposition of new bedload transport estimation methods, specifically developed for paved streams experiencing external supply or armour breaking.Experimental results are then provided. Firstly, flume experiments highlight the emergence of a more regular bedload transport when check dams are built in alluvial reaches. In a second stage, experiments were performed on a generic Froude scale model of an open check dam basin in order to capture the features of laterally-unconstrained, highly mobile flows. A new flow measurement and inverse-reconstruction procedure has been developed. A preliminary analysis of the results describes flows that tend toward a critical regime and the occurrence of feedback mechanisms between geomorphology and hydraulics during massive bedload deposition

The successful management of solid wastes arising from the combustion of low-rank coal for electricity generation presents significant engineering and environmental challenges. The power stations in the Latrobe Valley region of Victoria, Australia, have long recognised the need for improved long term understanding of ash disposal. This thesis presents the work undertaken in evaluating the mechanisms which lead to the transport of solutes from ash disposal and develops a methodology to quantify their potential long term impacts on groundwaters beneath a disposal site. The Loy Yang power station is used as a case study. A detailed literature review is presented on the mechanisms involved in the leaching of solutes from ash disposal. In general, the release of solutes is well understood and is related to the dissolution of more soluble minerals in the ash and advective transport through pore waters as leachate, although the exact controls for trace elements is less well documented. The proportions of particular solutes and/or trace elements is site specific. For the Latrobe Valley, however, there remains little research undertaken on the behaviour of Loy Yang ash, especially aged or leached ash excavated from a disposal pond after a period of some 6 to 12 months. The principal environmental concerns relating to the disposal of ash are the potential for groundwater contamination from salt fluxes and the transport of trace elements. Thus long term disposal requires a thorough understanding of both the solute fluxes from the ash as well as the controls on the transport of these solutes through groundwater. Predicting the behaviour of ash and the leached solutes under field conditions is difficult and common laboratory tests have been found to be inadequate. The transport of sulfate in seepage was investigated through back analysis of monitoring data, field monitoring, bacterial analysis and modelling. Sulfate was shown to be undergoing strong biogeochemical reactions which attenuate its rate of migration in shallow groundwaters at the Loy Yang power station. The application of a kinetic solute transport model was able to model the monitoring data obtained to date. The chemical quality of the ash, and its source from the power station, is a critical aspect of disposal since this primarily determines the leachability and potential fluxes. After slurrying and disposal in a saturated pond, the amount of soluble minerals is lower and therefore the ash presents a lower potential for groundwater impacts. For ash excavated from a disposal pond and placed within a low moisture environment, such as an Overburden Dump, the potential for leaching and solute transport must be considered differently to that in a saturated disposal pond. Two field trial cells were operated for about 14 months to investigate such behaviour, one artificially irrigated (Wet) and a second open to rainfall only (Dry). Both cells showed the importance of unsaturated flow mechanisms in controlling the water balance and leachate generation, due mainly to the potential of ash to retain moisture in its pores. The irrigated cell showed a marked reduction in leachate salinity as irrigation continued, although some trace elements demonstrated complex leaching patterns. To further quantify ash leaching rates, a series of laboratory leaching columns were constructed and operated, with electronic logging of soil moisture using Time Domain Reflectometry (TDR). The use of TDR, although able to detect relative changes in soil moisture, was less than successful. The leachate results from the columns were encouraging and provided additional confirmation of leaching curves for particular solutes and trace elements. The soil water characteristic curve (SWCC) was established for the ash through a Tempe Cell test. This quantified more accurately the water retention properties highlighted through the field and laboratory research. Importantly, analysis of the SWCC for the ash shows that it appears to maintain high hydraulic conductivity over typical ranges of matric suctions. The geochemical controls on solutes in the various ash leachates generated in the field and laboratory were investigated through geochemical speciation modelling and plotting. The major solutes in leachate appeared to be controlled by dissolution from more soluble minerals, such as gypsum and halite, while for other species the controls were more complex. Most trace elements appeared to be controlled by a mix of mineral dissolution, co-precipitation and adsorption mechanisms. A solute transport and leaching model was developed and applied to the various data sets obtained for this thesis. The model, describing the leaching and transport of solute in one-dimensional steady state flow, gave reasonable calibration to the different column experiments. Extension of this approach to unsaturated flow and solute transport is discussed in light of the experience from the field trials. The conversion of this model to non-dimensional form was then examined and provided a useful approach for assessing the scale effects from different sized column leaching experiments and field trials. The use of batch leaching tests, although not generally representative of field conditions, can be incorporated into this approach and used to estimate the initial concentration of a solute in leachate. The use of these models provides the methodology to quantify leaching over time and at various scales, important in the engineering design of ash disposal sites. In summary, this thesis presents a detailed qualitative study of ash leaching and solute transport mechanisms, and develops a quantitative methodology for the design and assessment of ash disposal sites.

The successful management of solid wastes arising from the combustion of low-rank coal for electricity generation presents significant engineering and environmental challenges. The power stations in the Latrobe Valley region of Victoria, Australia, have long recognised the need for improved long term understanding of ash disposal. This thesis presents the work undertaken in evaluating the mechanisms which lead to the transport of solutes from ash disposal and develops a methodology to quantify their potential long term impacts on groundwaters beneath a disposal site. The Loy Yang power station is used as a case study. A detailed literature review is presented on the mechanisms involved in the leaching of solutes from ash disposal. In general, the release of solutes is well understood and is related to the dissolution of more soluble minerals in the ash and advective transport through pore waters as leachate, although the exact controls for trace elements is less well documented. The proportions of particular solutes and/or trace elements is site specific. For the Latrobe Valley, however, there remains little research undertaken on the behaviour of Loy Yang ash, especially aged or leached ash excavated from a disposal pond after a period of some 6 to 12 months. The principal environmental concerns relating to the disposal of ash are the potential for groundwater contamination from salt fluxes and the transport of trace elements. Thus long term disposal requires a thorough understanding of both the solute fluxes from the ash as well as the controls on the transport of these solutes through groundwater. Predicting the behaviour of ash and the leached solutes under field conditions is difficult and common laboratory tests have been found to be inadequate. The transport of sulfate in seepage was investigated through back analysis of monitoring data, field monitoring, bacterial analysis and modelling. Sulfate was shown to be undergoing strong biogeochemical reactions which attenuate its rate of migration in shallow groundwaters at the Loy Yang power station. The application of a kinetic solute transport model was able to model the monitoring data obtained to date. The chemical quality of the ash, and its source from the power station, is a critical aspect of disposal since this primarily determines the leachability and potential fluxes. After slurrying and disposal in a saturated pond, the amount of soluble minerals is lower and therefore the ash presents a lower potential for groundwater impacts. For ash excavated from a disposal pond and placed within a low moisture environment, such as an Overburden Dump, the potential for leaching and solute transport must be considered differently to that in a saturated disposal pond. Two field trial cells were operated for about 14 months to investigate such behaviour, one artificially irrigated (Wet) and a second open to rainfall only (Dry). Both cells showed the importance of unsaturated flow mechanisms in controlling the water balance and leachate generation, due mainly to the potential of ash to retain moisture in its pores. The irrigated cell showed a marked reduction in leachate salinity as irrigation continued, although some trace elements demonstrated complex leaching patterns. To further quantify ash leaching rates, a series of laboratory leaching columns were constructed and operated, with electronic logging of soil moisture using Time Domain Reflectometry (TDR). The use of TDR, although able to detect relative changes in soil moisture, was less than successful. The leachate results from the columns were encouraging and provided additional confirmation of leaching curves for particular solutes and trace elements. The soil water characteristic curve (SWCC) was established for the ash through a Tempe Cell test. This quantified more accurately the water retention properties highlighted through the field and laboratory research. Importantly, analysis of the SWCC for the ash shows that it appears to maintain high hydraulic conductivity over typical ranges of matric suctions. The geochemical controls on solutes in the various ash leachates generated in the field and laboratory were investigated through geochemical speciation modelling and plotting. The major solutes in leachate appeared to be controlled by dissolution from more soluble minerals, such as gypsum and halite, while for other species the controls were more complex. Most trace elements appeared to be controlled by a mix of mineral dissolution, co-precipitation and adsorption mechanisms. A solute transport and leaching model was developed and applied to the various data sets obtained for this thesis. The model, describing the leaching and transport of solute in one-dimensional steady state flow, gave reasonable calibration to the different column experiments. Extension of this approach to unsaturated flow and solute transport is discussed in light of the experience from the field trials. The conversion of this model to non-dimensional form was then examined and provided a useful approach for assessing the scale effects from different sized column leaching experiments and field trials. The use of batch leaching tests, although not generally representative of field conditions, can be incorporated into this approach and used to estimate the initial concentration of a solute in leachate. The use of these models provides the methodology to quantify leaching over time and at various scales, important in the engineering design of ash disposal sites. In summary, this thesis presents a detailed qualitative study of ash leaching and solute transport mechanisms, and develops a quantitative methodology for the design and assessment of ash disposal sites.

Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies
This document presents the implementation of several methods for geo-spatial analysis of river networks and watersheds for runoff routing and solute transport in R in order to contribute in a comprehensive hydrological modelling to the current framework of the R package ”hydromad”. The main aim of the study is to develop R routines to coupled the outputs of the hydrological framework of the R package ”hydromad” to the selected solute transport model looking forward better simulation of water-quality determinants transport at watershed scale. Following the research scheme presented in this proposal it is possible to prove the hypothesis behind the study. The simulation of solute transport at specific places of the river network was improved by implementing a runoff routing method at watershed-scale, the ”hydromad” package, and by coupling it into a suitable modeling framework for representing solute transport processes. The developed package, ”watersheds”, allows geo-spatial river network analysis and makes use of the Catchments and Rivers Network System (ECRINS) version 1.1, which constitutes the hydrographical system currently in use at the European Environment Agency as well as widely serving as the reference system for theWater Information System for Europe (WISE). The versatility of the code generated lets to implement geo-spatial analysis in any watershed included into the ECRINS, as a consequence, watersheds along entire Europe could be analyzed. This constitutes an important fact because several institutions or scientific community related with the WISE system could take advantage of the package and this document.

The cell pressure probe (CPP) is an apparatus used to measure membrane parameters of cells, namely the hydraulic conductivity which indicates the permeability of the membrane to water, the permeability coefficient which indicates the permeability of the membrane to solutes, and the reflection coefficient which indicates the extent to which water and solute transport across the membrane is coupled. This thesis is a numerical exploration of the impact of unstirred layers on the measurement of these parameters. Unstirred layers alter the effective concentration across the membrane, and hence influence the calculation of the membrane parameters which are usually obtained using the concentration value in the external bulk solution and assume a homogeneous internal cell solution. In CPP experiments, cell pressure dynamics are changed by imposing either: a) a hydrostatic perturbation, where cell sap is injected into or removed from the cell, or b) an osmotic perturbation, where permeable solutes are added to or removed from the external solution. Outputs are pressure-time curves which are termed relaxation curves. Much of the CPP data has been obtained for Chara, a large-celled algae. The model developed here will be applied to two sets of Chara data: one previously published, and one unpublished and obtained from collaborators who freely contributed their data to this study. Data from two types of CPP experiments were used to estimate membrane parameters by fitting both the classical and unstirred layer (UL) models. These were: hydrostatic pressure pulse experiments, and osmotic pressure pulse experiments using permeable solutes. This thesis comprises five chapters. Chapter 1 provides an introduction to the research area, and gives an overview of the cell system, CPP experiments, and membrane transport theory. In Chapter 2 an analysis of predictions and limitations using the classical (i.e. usual) method of parameter estimation is made by applying it to published data. This classical model makes simple assumptions about the system, allows analytical solutions to the membrane transport equations, and does not include unstirred layers. In Chapter 3, a model based upon the classical model but incorporating unstirred layers, is outlined and its behaviour and predictions examined. In Chapter 4, the unstirred layer model is applied to unpublished CPP data, its predictions compared with those from the classical model, and the overall predictions and behaviour of the unstirred layer model evaluated. Finally, in Chapter 5 an assessment of usual practices and assumptions made in the parameter estimation process using the CPP is carried out, and recommendations for future research are given. The UL model was found to reproduce the observed CPP data to a high degree of accuracy, and reproduced subtle details in the observed data better than the classical model. Estimated parameters from the two models differed significantly; the relative difference in the parameters with respect to the UL model was up to 50% for osmotic experiments and 5% for hydrostatic experiments. This shows that unstirred layers have a significant impact on estimated parameters, and that the membrane parameters commonly estimated using the classical model may be in error by up to 50%. Data from three Chara cells were fit in Chapter 4. Significant inter-cell variation in estimated parameters was found. Estimated parameters for experiments carried out within the same cell were quite consistent, indicating that the UL model is predicting the membrane parameters well since parameters are expected to characterise a cell and its membrane. The behaviour of the UL model was also consistent with expectations from the Kedem and Katchalsky theory for membrane transport, suggesting that the UL model affects the estimated membrane parameters but not the overall behaviour predicted by the membrane transport equations. Cell pressure dynamics were found to be very sensitive to the thickness of the unstirred layers in the system, so that estimated membrane parameters are dependent on knowledge of the UL thicknesses. In Chapter 4, the UL model was used to estimate the external UL thickness together with the membrane parameters, while the internal UL thickness was fixed at a value effectively equivalent to assuming the whole cell interior is a UL. The model estimated the external UL thickness to be in the range of 30-50 μm for fits to the unpublished data. Some variation in estimated parameters between types of CPP experiments (e.g. hydrostatic or osmotic experiments; experiments with positive or negative pressure perturbations) were found, but the sample size was not sufficiently large for definite conclusions to be made. The UL model did not predict polarity in the membrane parameters (i.e. differences in parameters between positive and negative pressure perturbations). This suggests that evidence of polarity found in the parameters is likely due to effects of a composite membrane (e.g. presence of a tonoplast) or of dehydration of the membrane, and not due to the presence of ULs. Data were also available from osmotic experiments where bubbles were used to separate the new and old external solutions during the solution changeover. Fits to experiments where bubbles are present were found to be more straightforward and to give more accurate estimates of membrane parameters, as the time for solution exchange was significantly shortened. Where bubbles were not present, the time for solution exchange could not be as effectively incorporated into the model due to lack of experimental data regarding the duration and shape of the solution changeover. Results clearly showed that some common assumptions regarding the effects of ULs on CPP experiments are incorrect. External ULs are often assumed to primarily influence only the first few seconds of the relaxation curve, but the UL model shows that internal and external ULs influence the cell dynamics throughout the entire course of a CPP experiment. Furthermore, the extent of the influence on ULs on CPP data can only be quantified numerically. Previous attempts at using solutions to steady-state diffusion equations, or using steady-state equations relating permeability across the membrane to permeability in the ULs to predict the impact of ULs on estimated membrane parameters, are shown to be inaccurate. Published estimates of membrane parameters for Chara are deemed to be in error, because even where effects of ULs have been claimed to be taken into account, this has not been done numerically. In addition, it is shown that relaxation curves can be fit using the classical model (which does not incorporate ULs) despite the presence of unstirred layers, because ULs do not change the fundamental shape of the relaxation curves, and therefore the true effects of ULs are hidden. It is recommended that the classical model no longer be used for parameter estimation, and a more realistic model incorporating ULs be applied. This will lead to a more accurate estimation of membrane parameters. The model developed in this thesis, by taking into account effects of unstirred layers, can help to resolve the extent to which ULs impact on estimated membrane parameters, and also the extent to which ULs influence parameter variation among different types of experiments or experimental conditions. Currently, further experimental data is necessary for a wider application of the UL model and fuller assessment of its predictions. The UL model may also be extended in the future for application to more complicated systems such as root tissues.

Ecohydrological models are extensively used to evaluate land use, land management and climate change impacts on hydrology and in-stream water quality conditions. The scale at which these models operate influences the complexity of processes incorporated within the models. For instance, a large scale hydrological model such as Soil and Water Assessment Tool (SWAT) that runs on a daily scale may ignore the sub-daily scale in-stream processes. The key processes affecting in-stream solute transport such as advection, dispersion and transient storage (dead zone) exchange can have considerable effect on the predicted stream solute concentrations, especially for localized studies. To represent realistic field conditions, it is therefore required to modify the in-stream water quality algorithms of SWAT by including these additional processes. Existing reach-scale solute transport models like OTIS (One-dimensional Transport with Inflow and Storage) considers these processes but excludes the actual biochemical reactions occurring in the stream and models nutrient uptake using an empirical first-order decay equation. Alternatively, comprehensive stream water quality models like QUAL2E (The Enhanced Stream Water Quality Model) incorporates actual biochemical reactions but neglects the transient storage exchange component which is crucial is predicting the peak and timing of solute concentrations. In this study, these two popular models (OTIS and QUAL2E) are merged to integrate all essential solute transport processes into a single in-stream water quality model known as ‘Enhanced OTIS model’. A generalized model with an improved graphical user interface was developed on MATLAB platform that performed reasonably well for both experimental data and previously published data (R²=0.76). To incorporate this model into large-scale hydrological models, it was necessary to find an alternative to estimate transient storage parameters, which are otherwise derived through calibration using experimental tracer tests. Through a meta-analysis approach, simple regression models were therefore developed for dispersion coefficient (D), storage zone area (A_s) and storage exchange coefficient (α) by relating them to easily obtainable hydraulic characteristics such as discharge, velocity, flow width and flow depth. For experimental data from two study sites, breakthrough curves and storage potential of conservative tracers were predicted with good accuracy (R²>0.5) by using the new regression equations. These equations were hence recommended as a tool for obtaining preliminary and approximate estimates of D, A_s and α when reach-specific calibration is unfeasible.

The existing water quality module in SWAT was replaced with the newly developed ‘Enhanced OTIS model’ along with the regression equations for storage parameters. Water quality predictions using the modified SWAT model (Mir-SWAT) for a study catchment in Germany showed that the improvements in process representation yields better results for dissolved oxygen (DO), phosphate and Chlorophyll-a. While the existing model simulated extreme low values of DO, Mir-SWAT improved these values with a 0.11 increase in R² value between modeled and measured values. No major improvement was observed for nitrate loads but modeled phosphate peak loads were reduced to be much closer to measured values with Mir-SWAT model. A qualitative analysis on Chl-a concentrations also indicated that average and maximum monthly Chl-a values were better predicted with Mir-SWAT when compared to SWAT model, especially for winter months. The newly developed in-stream water quality model is expected to act as a stand alone model or coupled with larger models to improve the representation of solute transport processes and nutrient uptake in these models. The improvements made to SWAT model will increase the model confidence and widen its extent of applicability to short-term and localized studies that require understanding of fine-scale solute transport dynamics.

Die Modellierung von komplexen Systemen, wie dem Untergrund, ist ein Hilfsmittel zur Beschreibung der in der Realität ablaufenden Prozesse. Die Durchführung von Experimenten an einem Modell, um qualitative Aussagen über ein reales System zu erhalten, wird als Simulation bezeichnet. Dabei können vielfältige Modelle, wie z.B. physikalische und mathematische, zum Einsatz kommen. Die ungesättigte Bodenzone (vadose Zone) bezeichnet den Bereich zwischen der Landoberfläche und dem Grundwasserspiegel, innerhalb dessen der Wassergehalt geringer als bei Vollsättigung, und der Druck geringer als der Atmosphärendruck ist. Dieser Bodenbereich hat für die Landwirtschaft, Geobiologie, aerobe Abbauprozesse und Grundwasserneubildung eine große Bedeutung. Für die Nachbildung von Strömungs- und Stofftransportprozessen der ungesättigten Bodenzone existieren numerische Simulationsprogramme. Ziel der vorliegenden Arbeit ist eine umfangreiche Validierung des Programms PCSiWaPro® (entwickelt an der TU-Dresden, Institut für Abfallwirtschaft und Altlasten) für unterschiedliche Anwendungsfälle. Ein weiteres Ziel der Arbeit besteht in der Untersuchung der Anwendbarkeit des aktuellen Stands des Simulationsprogramms PCSiWaPro® auf unterschiedliche Praxisfälle bei Kombination der ungesättigten Bodenzone mit technischen Anlagen. Vier Anwendungsfälle mit unterschiedlichen Zielen wurden dafür im Rahmen dieser Arbeit untersucht: die Simulation von dezentraler Abwasserversickerung (Kleinkläranlage - KKA) anhand entsprechender Säulen- und Feldversuche, die Berechnung der Grundwasserneubildung am Beispiel von Lysimetern, der Wasserhaushalt von Erddämmen und die Modellierung von Deponieabdeckungssystemen. Die Anwendungsfälle unterscheiden sich durch den Zweck der Simulation, die Geometrie, die Größe, die festgelegten Anfangs- und Randbedingungen, die Simulationszeit, die Materialien, das Koordinatensystem sowie die Ein- und Ausgabewerte. Die Simulationsergebnisse konnten eindeutig zeigen, dass das Programm PCSiWaPro® für alle im Rahmen der vorliegenden Arbeit untersuchten Fälle, mit unterschiedlichen Strömungsregimen, Stofftransport-Parametern, Randbedingungen, Koordinatensystemen sowie Raum- und Zeitdiskretisierungen anwendbar ist. Die Simulationsergebnisse der Säulenversuche am Beispiel dezentraler Abwasserversickerung zeigten eine sehr gute Übereinstimmung zwischen gemessenen und mittels PCSiWa-Pro® berechneten Werten des Wasser- und Stoffhaushaltes (Druckhöhe, Abfluss und Stoff-konzentration) der untersuchten Bodentypen B3 (schwachschluffiger Sand), B4 (Grobsand) und B5 (mittelschluffiger Sand). Die Wurzel des mittleren quadratischen Fehlers (RMSE) betrug für die Berechnung der Druckhöhe 1,84 cm bei B5, 3,61 cm bei B3 und 1,27 cm bei B4. Die relative Abweichung betrug für die Berechnung der Druckhöhe 2,19 % bei B5, 1,3 % bei B3 und ca. 5,3 % bei B4. Die Durchführung der Sensitivitätsanalyse der für die Modellierung relevanten Parameter zeigte eine sehr hohe Sensitivität der VAN GENUCHTEN-Parameter und der gesättigten hydraulischen Leitfähigkeit des Bodens. Darüber hinaus führten die Parameter nach DIN 4220 und die mithilfe von Pedotransferfunktionen aus Siebanalysen genommenen Parameter zu unterschiedlichen Ergebnissen. Im Rahmen des am Institut für Abfallwirtschaft und Altlasten durchgeführten Projektes EGSIM wurden die Programme SENSIT und ISSOP (in Zusammenarbeit mit DUALIS GmbH IT Solution) entwickelt und zur Parameteridentifikation/-kalibrierung benutzt. Die im Rahmen dieser Arbeit erzielten Ergebnisse konnten nachweisen, unter welchen Bedingungen eine Nachklärung des vollbiologisch gereinigten Abwassers innerhalb der Bodenzone möglich ist, so dass am Ort der Beurteilung (Grundwasseroberfläche) kein unzulässiger Schadstoffeintrag erfolgt. In Bezug auf die KKA-Feldmodelle ist die Anwendung des rotationssymmetrischen Koordinatensystems als Voraussetzung der Realität besser zu entsprechen und nicht als Option zu betrachten. Darüber hinaus wurden anhand der Feldmodelle verschiedene Szenarien mit kontinuierlicher und diskontinuierlicher Versickerung sowie zwei unterschiedlich großen Einleitflächen durchgeführt. Das Programm PCSiWaPro® ist sowohl für ungesättigte als auch für variabel-gesättigte porösen Medien anwendbar. Dies wurde im Rahmen der Simulation des Wasserhaushaltes eines Erddamms nachgewiesen. Die durchschnittliche relative Abweichung zwischen gemessenen und mittels PCSiWaPro® berechneten Wasserständen des entsprechenden Beobachtungspunkts im untersuchten Dammkörper lag bei 0,08 % (entspricht 5,8 cm bei einer Müchtigkeit von ca. 70 m) und das Bestimmtheitsmaß (R2) betrug 0,987. Die Simulation des Wasserhaushaltes unterschiedlicher Deponieabdichtungssystemen mittels PCSiWaPro® zeigte im Allgemeinen ein funktionierendes Ableiten des auf Deponien anfallenden Regenwassers (auch bei Starkregenereignissen). Darüber hinaus haben die durchgeführten Bewuchs-Modelle nachweisen können, dass die Vegetation der Deponieoberflächen den Wassergehalt, durch Pflanzenwurzelentzug bzw. Evapotranspiration, reduzieren können. Die Simulationsergebnisse der durchgeführten Szenarien des Wasserhaushaltes von Lysimetern zur prognostischen Berechnung der Grundwasserneubildung mittels PCSiWaPro® konnten nachweisen, dass das Programm für die Berechnung der Grundwasserneubildungsrate für diesen Zweck anwendbar ist. Die relativen Abweichungen der be-rechneten von den gemessenen Grundwasserneubildungsraten sind auf die verwendeten Materialparameter sowie auf Vernachlässigung der möglicherweise in Lysimetern sich befin-denden Makroporen (duale Porosität) zurückzuführen.
The modelling of complex systems such as the underground is a means to describe the processes occurring in the reality. The conducting of experiments on a model to obtain qualitative evidence about a real system is referred to as a simulation. Thereby, various models (e.g. physical and mathematical models) can be used. The unsaturated zone (vadose zone) is the region between the land surface and the water table, in which the water content is less than full saturation, and the pressure is lower than the atmospheric pressure. The unsaturated zone is very significant for agriculture, geobiology, aerobic degradation processes and groundwater recharge. The processes of water flow and solute transport in the unsaturated zone can be described by means of numerical simulation programs. The aim of the present work is a comprehensive validation of the simulation program PCSiWaPro® (developed at the TU-Dresden, Institute of Waste Management and Contaminated Site Treatment) for different applications. Another aim of this work is to investigate the applicability of the current version of PCSiWaPro® for different cases of a combination between the unsaturated zone and technical facilities. Four application cases with different objectives were investigated within the present work, which are: the simulation of decentralized wastewater infiltration with corresponding column and field experiments, the computation of groundwater recharge by means of lysimeters, the water balance of earth dams and the modelling of landfill covering systems. The application cases differ from each other by the objective of the simulation, the geometry, the size, the specified initial and boundary conditions, the simulation time, the applied materials, the coordinate system, the input and output data. The simulation results clearly showed that PCSiWaPro® is applicable for all investigated cases under consideration of different flow and solute transport regimes, parameters, boundary conditions, spatial and temporal discretization, and coordinate systems. The simulation results of the experimental soil columns for the decentralized treated wastewater infiltration case showed a very good agreement between measured and computed values of water and solute balance (pressure head, flow and solute concentration) of the investigated soil types B3 (slightly silty sand), B4 (coarse sand / gravel) and B5 (medium silty sand). The root of the mean squared error (RMSE) for the computation of the pressure head was 1,84 cm at B5, 3,61 cm at B3 and 1,27 cm at B4. The relative deviation in case of pressure head computation was 2,19 % at B5, 1,3 % at B3 and 5,3 % at B4. The implementation of the sensitivity analysis of the relevant parameters for the modelling showed a very high sensitivity of the VAN GENUCHTEN parameters and the saturated hydraulic conductivity of the soil. Moreover, the parameters according to DIN 4220 led to different results than the estimated ones according to pedotransfer methods based on sieve analysis. Within the project EGSIM, which was carried out at the Institute for waste management and contaminated sites treatment in collaboration with DUALIS GmbH IT Solution, the programs SENSIT and ISSOP were developed and used for parameter identification/ calibration. The results obtained in this Work showed under which conditions is a secondary treatment of full biologically treated wastewater in the soil possible, so that no unallowable pollutants entry in the groundwater occurs. With regard to the field models of this application the implementation of the rotationally symmetric coordinate system should be considered as a condition and not as an option for a better corresponding to the reality. Furthermore, different scenarios of the field models were carried out with continuous and discontinuous infiltration, as well as under different initiation areas. PCSiWaPro® could be applied for both unsaturated and variably-saturated porous media. This could be proven by the simulation of the water balance in an earth dam. The average relative deviation between measured and simulated water levels of the corresponding observation point in the investigated dam embankment was 0,08 % (corresponding to 5,8 cm at 70 m thickness) and the coefficient of determination (R2) was 0,987. In general, the simulation of the water balance using PCSiWaPro® of different landfill covering systems showed a successful draining of the falling rainwater (even under heavy rainfall). In addition, the implemented vegetation models have proven that the vegetation of the landfill surface can reduce the water content in the landfill by evapotranspiration and water uptake by roots. The water balance simulation results of the scenarios for the computation of groundwater recharge by means of lysimeters showed that the program is applicable for this case. The relative deviation of the simulated from the measured groundwater recharge rates occur due to the implemented material parameters as well as to the neglect of macro pores effects (dual porosity).