Streams and rivers have been modified in the past centuries for agricultural purposes. The Baltic Sea suffers from problems regarding eutrophication. Regulations of point-sources have decreased nutrient levels, but for a scattered source of nutrient pollution, streams are important. One way of mitigating nitrogen is with coupled denitrification and nitrification processes when stream water is transported through flow paths in the hyporheic zone, an area in the stream sediments where groundwater and stream water mix. Tullstorps brook is an agricultural stream that flows into the Baltic Sea. It has had problems with high nutrient loads and poor water quality and has therefore been restored. The fieldwork in this project was conducted in Tullstorps brook in May 2019, where Rhodamine WT (RWT) tracer test and Hydraulic Conductivity (HC) measurements were done in 3 reaches, and compared to similar fieldwork since before restorations, during the summer of 2015. Two reaches in an agricultural setting that have been restored, Reach 4 and Reach 6, were measured, as well as a control reach, Reach 5, which is in a natural setting. The tracer tests indicated a significant decrease in the velocity in remediated reaches. The results of exchange velocity between the stream flow and the hyporheic zone suggest an increase after remediation of the reaches and the residence time seems to be decreasing simultaneously. When comparing the hydraulic characteristics, different stream flow during measurements was considered in a qualitative manner. The results of HC measurements show a decrease from 2015 to 2019 in the remediated reaches. In Reach 4 it decreased from 1.20E-03 m/s to 5.0E-4 m/s and in Reach 6, HC decreased from 7.70E-04 m/s before remediations to 5.6E-04 m/s after remediation actions. All the measurements have uncertainties, especially since homogeneity is assumed to some extent and the natural environment will always be heterogeneous.

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. / <p>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</p>

No description available.

No description available.

Wastewater treatment plants (WWTPs) play a vital role in protecting the environment from much of the waste produced by humans. This includes not only human waste, but everything that makes its way into a sewerage system including greywater, stormwater, and potentially hazardous chemicals from, inter alia, chemical spills. The effects of a chemical spill if it enters a WWTP can be disastrous, resulting in the ineffective treatment of incoming water for prolonged periods of time (Söhr, 2014). This can lead to one of the dilemmas of urban wastewater systems, notably, whether it is more damaging to allow a chemical spill to bypass a WWTP, or to attempt to treat all or some of the spill and risk damaging the microbes working in the biological treatment processes (Schütze, 2002). In order to better inform policy makers and process engineers at WWTPs of which measures to take in the event of a spill, solute transport characteristics of a specific sewerage network must be defined.  A series of tracer tests were performed along The Käppala Association’s northern sewerage network to determine these solute transport characteristics, notably the dispersion coefficient which strongly affects the level of dilution that occurs between the injection point and the inlet. A simple solute transport model, carried out in Excel, was created using the Advection-Dispersion Equation (ADE) and the Manning-Strickler equation to relate flow measurements to flow velocity. Results from the experiments show that a dispersion coefficient of 1.55m2/s appears to be applicable throughout the whole of the tunnel network. A depth dependent Manning-Strickler coefficient seems to describe the flow-velocity relationship, however, this method has not been validated. The ADE begins to lose accuracy in describing solute transport as the distance from the inlet and the number of pumping stations the plume goes through increases. / Avloppsreningsverk spelar en viktig roll för att skydda miljön från mycket av det avfall som produceras av människor. Detta inkluderar inte bara mänskligt avfall utan allt som tar sig in i ett avloppssystem, till exempel gråvatten, dagvatten och potentiellt farliga kemikalier från bland annat industriutsläpp. Effekterna av ett kemiskt utsläpp kan vara katastrofala om det kommer in i ett avloppsreningsverk, vilket resulterar i ineffektiv behandling av inkommande vatten under längre perioder (Söhr, 2014). Detta är ett dilemma i urbana avloppssystem – ska man låta ett kemiskt utsläpp ledas förbi ett avloppsreningsverk, eller försöka behandla hela eller en del av utsläppet och riskera att skada mikroberna i den biologiska reningsprocessen (Schütze, 2002). För att beslutsfattare och processingenjörer vid avloppsreningsverk ska kunna fatta rätt beslut om vilka åtgärder som ska vidtas vid utsläpp måste egenskaperna för det specifika avloppsnätet definieras.  Syftet med detta projekt är att uppskatta transportparametrar och karakterisera utspädning i nätverket genom att utföra en serie spårningsförsök i Käppalaverkets upptagningsområde. För att nå syftet fanns det flera mål som genomförts: Genomföra en litteraturstudie  Skapa en förutsägbar modell i Excel baserad på flödesdata längs Käppalaförbundets tunnelsystem Genomföra en serie spårningsförsök vid flera punkter längs tunnelsystemet  Strukturerad datalagring av resultaten så att data är lätt att hitta för framtida projekt  Metoderna kan delas i två: modellering och försök. För att skapa en modell och simulera transport av ett ämne i nätet får man definiera relevanta ekvationer. För den hydrauliska delen av modellen användes Manning-Strickler-ekvationen. Resultaten från detta användes sedan i den förenklade formen av advektion-spridningsekvationen (ADE). Tunnelsystemet uppdelades i flera sektioner med samma egenskaper såsom form och geometri, och en anpassad form av ADE användes emellan sektionerna. För att nå framgång i försöken krävdes att rätt spårämne valdes. Uranin användes i försöken på grund av sina ogiftiga och stabila egenskaper och den låga detektionsgränsen. Injiceringspunkterna låg gradvis längre bort från inloppet; Försök 1 var 9km från verket till nästan 46km vid Arlanda flygplats för Försök 3.  Resultaten från simuleringarna användes för att planera injiceringstid, start- och stopptid för provtagningen och provtagningsfrekvens. Resultatet från första försöket användes för att kalibrera modellen inför de andra försöken. Resultaten från alla försök visade att en dispersionskoefficient på 1.55m2/s, som är ett mått på utspädning i nätet, verkar tillämpligt till hela tunnelsystemet. Koefficienten kan dock vara högre i de kommunala näten. En djupberoende metod för att härleda Mannings tal formulerades, men det kräver ytterligare validering.  Från alla tre försöken kan vi härleda ett förhållande mellan avstånd från inlopp och toppkoncentration samt avstånd från inlopp och varaktigheten av genombrottskurvan. Toppkoncentration visar ett linjärt eller kanske logaritmiskt förhållande med distans, och varaktigheten av genombrottskurvan visar ett starkt linjärt förhållande. Kunskaper om detta är viktigt när man vill genomföra en riskbedömning av ett kemiskt utsläpp i upptagningsområdet eftersom det ger en insikt om hur det kan påverka den biologiska reningen i ett avloppsreningsverk.  Sammanfattningsvis fungerar den enkla formen av ADE bra, men viss avvikelse ses i experiment 3. Detta beror kanske på möjliga övergående lagringsprocesser vid pumpstationerna längs tunnelsystemet. En enda dispersionskoefficient, som är ett mått på utspädning, är tillämplig i hela huvudtunnelsystemet, men spridningen i kommunala nätverk är sannolikt högre. Ytterligare arbete behövs inom dessa kommunala nätverk för att kvantifiera deras effekter.  På grundval av resultaten från detta projekt rekommenderas ytterligare forskningsundersökningar om vad som händer med föroreningar i avloppsreningsverket. Eftersom slammet vid Käppalaverket används för biogasproduktion och är Revaq-certifierat för användning på jordbruksmark är föroreningsnivån i slammet mycket viktigt både ur produktivitets- och hälso- och säkerhetsperspektiv.

The applicability and adequacy of three modeling approaches to describe and predict breakthough curves (BTCs) for non-reactive solutes in statistically homogeneous porous media were numerically and experimentally investigated. Modeling approaches were: the convection-dispersion equation (CDE) with scale-dependent dispersivity, mobile-immobile model (MIM), and the fractional convection-dispersion equation (FCDE). In order to test these modeling approaches, a prototype laboratory column system was designed for conducting miscible displacement experiments with a free-inlet boundary. Its performance and operating conditions were rigorously evaluated. When the CDE with scale-dependent dispersivity is solved numerically for generating a BTC at a given location, the scale-dependent dispersivity can be specified in several ways namely, local time-dependent dispersivity, average time-dependent dispersivity, apparent time-dependent dispersivity, apparent distance-dependent dispersivity, and local distance-dependent dispersivity. Theoretical analysis showed that, when dispersion was assumed to be a diffusion-like process, the scale-dependent dispersivity was locally time-dependent. In this case, definitions of the other dispersivities and relationships between them were directly or indirectly derived from local time-dependent dispersivity. Making choice between these dispersivities and relationships depended on the solute transport problem, solute transport conditions, level of accuracy of the calculated BTC, and computational efficiency The distribution of these scale-dependent dispersivities over scales could be described as either as a power-law function, hyperbolic function, log-power function, or as a new scale-dependent dispersivity function (termed as the LIC). The hyperbolic function and the LIC were two potentially applicable functions to adequately describe the scale dependent dispersivity distribution in statistically homogeneous porous media. All of the three modeling approaches described observed BTCs very well. The MIM was the only model that could explain the tailing phenomenon in the experimental BTCs. However, all of them could not accurately predict BTCs at other scales using parameters determined at one observed scale. For the MIM and the FCDE, the predictions might be acceptable only when the scale for prediction was very close to the observed scale. When the distribution of the dispersivity over a range of scales could be reasonably well-defined by observations, the CDE might be the best choice for predicting non-reactive solute transport in statistically homogeneous porous media. / Ph. D.

Esta dissertação apresentou um estudo dos mecanismos de transporte de sódio, fosfato e amônio em colunas indeformadas de material inconsolidado residual de arenitos da Formação Adamantina. Em campo foi realizada caracterização táctil visual do material, alem de ensaios de condutividade hidráulica. Em laboratório, realizou-se ensaio de coluna em material indeformado, para que fossem obtidos os parâmetros de fluxo de água: velocidade linear media, velocidade de Darcy, vazão e condutividade hidráulica. Também foram obtidos os coeficientes de dispersão hidrodinâmica dos três íons estudados por meio de quatro métodos. Os fatores de retardamento dos íons foram obtidos por meio de três métodos. Para auxiliar nas analises, o solo foi caracterizado mineralógica, química, física e físico-quimicamente. Adicionalmente foram feitas analises da poro simetria e estudo das trajetórias de transporte. As informações foram integradas para que fosse possível analisar os parâmetros de transporte de solutos no solo. Com esta pesquisa percebeu-se que o uso dos parâmetros de transporte em modelagem do transporte de contaminantes deve ser feito com cautela, observando tanto as características do solo (mineralógicas, físicas, físico-químicas) quanto os modelos conceituais e as limitações dos métodos utilizados. / This research aimed to study the transport mechanisms of sodium, phosphate and ammonium in undisturbed columns of unconsolidated residual material of the sandstones from the Adamantina Formation. At field, visual and tactile characterization of the material were performed as well as hydraulic conductivity tests . At laboratory, there were made column tests in undisturbed samples to obtain the parameters of water flow, i.e., average linear velocity, Darcy velocity, flow rate and hydraulic conductivity. Hydrodynamic dispersion coefficients of every studied ion were determined using four methods. The retardation factors of the three ions were obtained using three methods. To assist the analysis, the soil was mineralogical, chemistry, physically and physic-chemically characterized. We also analyzed the water retention curve, mercury intrusion porosimetry and solute transport trajectories. All available data were integrated for analyzing the parameters of solute transport in soil. The results showed that the use of transport parameters in modeling of contaminant transport should be done with caution, observing soil characteristics, the conceptual models and the limitations of the methods used.

A demanda alimentar vem aumentando de acordo com o crescimento populacional e com isso há uma necessidade de que as práticas agrícolas tornem-se cada vez mais intensas e tecnificadas, mediante o incremento, entre outros, da utilização de insumos químicos. Porém, uma vez aplicados de maneira desorganizada, sem a devida preocupação com os possíveis impactos aos recursos naturais, tais produtos podem vir a provocar danos ao solo, contaminação de águas subterrâneas (mediante sua lixiviação) e em alguns casos, podem ser responsáveis pelo aumento da salinidade em alguns solos da região do semiárido do nordeste brasileiro. Nesse sentido, devido ao fato de envolverem processos físicos na natureza, o estudo da dinâmica desses produtos químicos têm motivado diversos pesquisadores a aplicarem ferramentas matemáticas (modelos matemáticos) na área de engenharia de água e solo, buscando entender a correlação entre a dinâmica da água e o movimento de solutos no perfil do solo. Portanto, a presente pesquisa tem como objetivo a aplicação do modelo matemático HYDRUS-1D para a simulação do movimento da água e do íon potássio, em condições de laboratório, utilizando-se colunas preenchidas com dois tipos de material de solos salinos e não saturados: Argissolo Amarelo (S1) e Latossolo Vermelho Amarelo (S2). Além disso, buscou-se também avaliar tanto o desempenho do referido modelo, em condições salinas, quanto proceder a uma análise de sensibilidade. Para alcançar tais objetivos, foram conduzidas as seguintes etapas: 1) elaboração de curvas de distribuição de efluentes (Breakthrough Curves - BTC) para obtenção dos parâmetros de transporte do íon potássio, com a aplicação de soluções de 1000 ppm, 2000 ppm e 3000 ppm de concentração de potássio, nos dois tipos de solos salinos, 2) Aplicação dessas soluções de potássio na coluna preenchida com o mesmo material de solo salino não saturado, 3) Simulação dos perfis de água e potássio para os diferentes materiais de solo salino pelo modelo HYDRUS-1D e 4) Avaliação de desempenho e análise de sensibilidade do modelo HYDRUS-1D. A avaliação de desempenho foi feita levando-se em conta os seguintes índices estatísticos: erro máximo, erro absoluto médio, raiz quadrada do erro médio normalizado, coeficiente de massa residual, coeficiente de determinação, eficiência e índice de concordância de Willmott e a análise de sensibilidade foi feita mediante a determinação do erro padrão, por meio de variações positivas (+ 10%, + 20%, + 30%, + 40%, + 50%) e negativas (- 10%, - 20%, - 10%, - 40%, - 50%), dos valores de: umidade volumétrica do solo saturado, condutividade hidráulica e os parâmetros n e ? do modelo de van Genuchten (1980). Diante dos resultados obtidos, pôde-se perceber que os procedimentos experimentais (BTC\'s) para a estimativa dos parâmetros de transporte do íon potássio em condições de solo salino, foram suficientes para descrever a movimentação do íon potássio no solo, gerando informações de entrada precisas para os modelos de simulação. Em termos do modelo HYDRUS-1D, observou-se que o deslocamento do íon potássio acompanhou a frente de molhamento e que o modelo foi eficiente nas simulações de deslocamento do íon potássio e da água para ambos os solos, em condições salinas. A análise de sensibilidade evidenciou que o modelo apresentou-se sensível, às variações negativas dos dados de entrada: umidade volumétrica do solo saturado, condutividade hidráulica do solo saturado e parâmetros \"n\" e \"?\" do modelo de van Genuchten (1980). / The increased demand for food due to population growth requires that agricultural practices become increasingly intensive and very technical, including the increased use of agricultural chemicals (fertilizers). If improperly applied without considering possible impacts on natural resources, agricultural chemicals may lead to soil and groundwater contamination through their leaching from the soil root zone. They may be responsible also for increased salinity in some soils of semiarid regions in northeastern Brazil. Since many transient physical and chemical processes affect their transport in the subsurface, mathematical models have become popular tools in soil and water engineering and management in order to understand the correlation between water dynamics and solute movement in soils. Thus, this research aimed at using the HYDRUS-1D software package to simulate water and potassium movement, under laboratory conditions, in unsaturated saline soil columns filled with two soil types: an Ultisol (S1) and an Oxisol (S2). Comparisons were made with experimental data while also a sensitivity analysis was carried out to evaluate the effect of various parameters on solute transport under saline conditions. For this purpose the following studies were performed: 1) Measurement of solute breakthrough curves (BTCs) to estimate the transport parameters of the potassium ion by applying potassium solutions of 1,000 ppm, 2,000 ppm and 3,000 ppm to both soil types, 2) Application of similar potassium solutions to columns containing the same saline unsaturated soils, 3) Simulation of water and potassium distributions for different saline soil materials using HYDRUS-1D, and 4) Performance evaluation and sensitivity analyses of the HYDRUS-1D numerical model. The performance evaluation was conducted using the following statistical indices: maximum error, mean absolute error, normalized root mean square error, coefficient of residual mass, coefficient of determination, efficiency and Willmott\'s concordance index. The sensitivity analyses considered standard deviations resulting from positive and negative changes (+ 10% + 20% + 30% + 40% + 50%) (-10%, -20%, -10%, -40%, -50%) in the values of the saturated volumetric soil moisture content, the saturated hydraulic conductivity, and the parameters n and ? of van Genuchten\'s (1980) model for the unsaturated soil hydraulic functions. Results indicate that the experimental procedures (BTCs) for estimating the transport parameters of potassium for saline soil conditions were sufficient to describe potassium ion transport in the soils by generating the required input information for the simulation models. Relative to HYDRUS-1D model, the displacement of potassium was found to follow closely the wetting front, with the model providing a very efficient means for simulating the movement of both water and potassium in the two soils during saline conditions. The sensitivity analysis showed that the model was relatively sensitive to negative variations of the input data, notably the saturated water content, the saturated hydraulic conductivity, and the n and ? soil hydraulic parameters.

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).

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.