Search

Managed Aquifer Recharge (MAR) can be conducted via wells or by spreading the water on a surface (e.g, during basin infiltration). While the former has the advantage of minimal area demand and the possibility of dual-use for groundwater abstraction, the latter usually has smaller construction costs and offers additional treatment to the water during infiltration via the vadose zone. Vadose Zone Wells (VZWs) combine many of these advantages, but as their hydraulics are more complex, infiltration rates and the degradation processes in the subsurface are more difficult to determine. Furthermore, they are prone to clogging and redevelopment has not been documented in the literature. Therefor, low-quality waters - with high content of suspended solids or dissolved contaminants/nutrients - are rarely infiltrated via VZWs. In this study, I will (1) evaluate the hydraulic advantage, VZWs can have over other vadose zone infiltration systems in a synthetical modeling study, (2) assess the spatial variability of key parameters for aerobic degradation below a VZW in a small-scale experiment, (3) determine the relationship between clogging dynamics and a well’s diameter and setup (gravel pack) in an experimental study and (4) demonstrate that the backflush of a VZW is possible - in contrast to the literature’s suggestions. All in all, VZWs appear to offer potential even for low-quality waters, and a further investigation for economical operation seems worthwhile., Managed Aquifer Recharge' ('MAR' = 'Künstliche Grundwasseranreicherung') kann mit Brunnen oder über flächenhafte Versickerung erfolgen (z.B. durch Infiltrationsbecken). Während Brunnen wenig Platz benötigen und neben der Infiltration auch für die Grundwasserentnahme genutzt werden können, sind Becken meist günstiger in Errichtung und Erhaltung und die Versickerung durch die ungesättigte Zone kann die Wasserqualität erheblich verbessern. 'Vadose Zone Wells' ('VZWs' ≈ 'Ungesättigte Schluckbrunnen') verbinden einige dieser Vorteile, allerdings sind Infiltrations- und Abbauprozess aufgrund der ungleich komplizierteren Hydraulik schwer vorherzusagen. Darüber hinaus sind sie anfällig für Kolmation/Clogging und über ihre Regenerierung ist nach jetzigem Stande nichts bekannt. Im Allgemeinen werden deshalb Wässer mit niedriger Qualität - hohe Trübung und/oder Schad- und Nährstoffgehalte - selten durch VZWs versickert. In dieser Studie, werde ich (1) in einer synthetischen Modellstudie die hydraulichen Vorteile aufzeigen, die VZWs gegenüber anderen Versickerungsformen haben, (2) die räumlichen Unterschiede von Schlüsselparametern für den aeroben Abbau unter einem VZW in einem Laborexperiment untersuchen, (3) die Verbindung zwischen Kolmationsdynamik sowie Brunnendurchmesser und -aufbau (insb. der Kiesschüttung) herausarbeiten und (4) demonstrieren, dass eine Rückspülung von VZWs möglich ist - anders als es die Literatur nahelegt. Insgesamt, bieten VZWs ein hohes Potential - auch für Wasser niedriger Qualität, die allerdings noch durch weitere Untersuchungen bzgl. Kosten/Nutzen und Nachhaltigkeit bestätigt werden müssen.

Assessment of potentially contaminated sites (PCS) can be expensive; hence, simple and less demanding methods and models are required. This work attempts to provide an approach that can aid in selecting the most appropriate model for the PCS. The developed method uses over 100 field site data to evaluate four test models (analytical/empirical) that provide the maximum plume length (Lmax), which is used as a principal model ranking quantity in this work. Analysis of site data shows that field plume length (Lf) follows a log-normal distribution. Subsequently, Lmax is delineated with respect to Lf using a threshold probability as underestimating, overestimating, and overly-overestimating. Akaike information criterion (AIC) and analytical hierarchy process (AHP) are considered to support the threshold approach results. The classical AIC is modified (to AICmod) to fit the term represented by the difference between Lf and Lmax. Additionally, the threshold factors as a product of subjective weights are added to the AICmod. Using Lf and Lmax, the AICmod provides a distinct ranking of the test models. For the AHP approach, the goodness of fit, underestimation, overly overestimation, and model complexity are the four chosen criteria. Similar to AICmod, the AHP approach provides a distinct ranking of the test models. The final decision on the best fitting model can be made on user criteria following the scheme developed in this work.

Groundwater vulnerability maps are important decision support tools for water resource protection against pollution and helpful in minimizing environmental damage. However, these tools carry a high subjectivity along the multiple steps taken for the development of such maps. Additionally, the theoretical model on which they are based does not consider other important parameters, such as pollutant concentration or pollutant residence time in a given section of the aquifer, solely focusing on the theoretical travel time of a pollutant particle from a release point towards a target. In this work, an integrated methodology for the evaluation of potential (intrinsic) and actual vulnerability is presented. This integrated method, named Integrated Karst Aquifer Vulnerability (IKAV), was developed after the analysis of several study cases around the world and the application of multiple intrinsic groundwater vulnerability methods in a selected study area. Also, a solute transport model served as the basis to define additional parameters for vulnerability analysis for areas severely affected by anthropogenic practices. However, the focus of the transport model must not be mistaken to be hazards and risk mapping. A defined workflow and several criteria for parameters and attributes selection, rating and weighting, and vulnerability classification are presented here. The first application of the IKAV method was carried out in the Yucatán karst, demonstrating to be a reliable method for vulnerability estimation. Results demonstrated the scope of the IKAV method in highlighting important regional conditions, minimizing the subjectivity, and expanding the analysis of vulnerability.

Land subsidence due to overexploitation of aquifers is often attributed to incoherent public policies. Taking the case of the Mahyar valley in Iran as an example, and based on a mixed-method research design, this study analyses the effects of policy incoherence on well use for agricultural irrigation and the resulting groundwater levels. Results show how an accumulation of policy incoherence over time results in an increased construction of wells, ultimately leading to a groundwater table drawdown, with a significant decrease of 7.61 m in the last 16 years.

The agricultural sector is one of the largest consumers of fresh water. With the ever-increasing problem of water scarcity, urbanization, over-population, and climate change, fresh water resources used by agriculture could be put to better use by redirecting it for drinking water purposes. In this context, many countries reuse treated urban waste water for irrigation, to overcome this problem. While this is a sustainable practice, the reuse of urban wastewater could facilitate the spread of pathogenic bacteria (or antibiotic resistant bacteria) in the subsoil region and consequently the groundwater. Since groundwater is one of the main sources of drinking water, the contaminants could pose a risk to human health. Furthermore, obtaining scientific data for emerging contaminants during water reuse is the need of the hour. The objective of this work is to build a mechanistic model that can aid in the development of large-scale risk assessment models; thus facilitating the setup of water reuse regulations for the relevant pathogenic organisms. In the present study, process based models were developed and evaluated using lab scale results. Then, the relative time scales of the processes are compared, and the relative importance of the various process studies are assessed. When assessing time scales of the processes, it is kept in mind that processes with relatively fast time scales can be approximated using equilibrium models, relatively slow processes can be neglected, and only the rate limiting processes can neither be neglected or further simplified in further model development. Therefore, an idea of the rate limiting processes assessed in lab scale can serve as important tools facilitating model simplification when evaluating larger scale models. A combined experimental and modelling approach has been used to study relevant transport and reactive processes during bacteria transport through sandy sediments. The mechanistic model contained transport processes which wer, Der Agrarsektor ist einer der größten Verbraucher von Süßwasser. Angesichts der zunehmenden Wasserknappheit, der Verstädterung, der Überbevölkerung und des Klimawandels könnten die von der Landwirtschaft genutzten Süßwasserressourcen besser genutzt werden, indem sie für Trinkwasserzwecke umgewidmet werden. In diesem Zusammenhang verwenden viele Länder aufbereitetes kommunales Abwasser für die Bewässerung, um dieses Problem zu lösen. Dies ist zwar eine nachhaltige Praxis, aber die Wiederverwendung von kommunalem Abwasser könnte die Ausbreitung pathogener Bakterien (oder antibiotikaresistenter Bakterien) im Untergrund und damit im Grundwasser fördern. Da das Grundwasser eine der Hauptquellen für Trinkwasser ist, könnten diese Schadstoffe eine Gefahr für die menschliche Gesundheit darstellen. Darüber hinaus ist es ein Gebot der Stunde, wissenschaftliche Daten über neu auftretende Verunreinigungen bei der Wasserwiederverwendung zu gewinnen. Ziel dieser Arbeit ist es, ein mechanistisches Modell zu erstellen, das bei der Entwicklung groß angelegter Risikobewertungsmodelle behilflich sein kann und somit die Aufstellung von Vorschriften für die Wiederverwendung von Wasser für die relevanten pathogenen Organismen erleichtert. In der vorliegenden Studie wurden prozessbasierte Modelle entwickelt und anhand von Ergebnissen im Labormaßstab bewertet. Anschließend werden die relativen Zeitskalen der Prozesse verglichen und die relative Bedeutung der verschiedenen Prozessstudien bewertet. Bei der Bewertung der Zeitskalen der Prozesse wird berücksichtigt, dass Prozesse mit relativ schnellen Zeitskalen durch Gleichgewichtsmodelle angenähert werden können, relativ langsame Prozesse können vernachlässigt werden, und nur die ratenbegrenzenden Prozesse dürfen in der weiteren Modellentwicklung weder vernachlässigt noch vereinfacht werden. Daher kann eine Vorstellung von den ratenbegrenzenden Prozessen, die im Labormaßstab bewertet werden, als wichtiges Instrument zur Vereinfachung des Mod

Diese Arbeit leistet einen methodischen Beitrag zur Identifizierung von Umsetzungsprozessen der Stickstoffverbindungen Ammonium und Nitrat in belasteten Grundwasserleitern mittels der Analytik der Isotopenverhältnisse N-15 bzw. O-18. Es existieren bereits verschiedene Präparationsmethoden, jedoch sind diese teilweise arbeits- oder zeitaufwändig und damit mit erheblichen Kosten verbunden. Für eine breitere Anwendbarkeit in den Umweltwissenschaften wurden im Rahmen dieser Arbeit zwei vereinfachte Methoden für die N-15 bzw. O-18 Stabilisotopenanalytik von Ammonium und Nitrat in Wässern erarbeitet. Zum einen wurde eine Fällungsmethode mit Natriumtetraphenylborat für die Probenvorbereitung der N-15 Isotopenanalyse für Ammonium weiterentwickelt, getestet und validiert. Bisher existierten keine Studien zur Anwendbarkeit dieser Methode auf die Analyse ammoniumhaltiger Wasserproben. Daher wurde die Methode in dieser Arbeit für die Anwendbarkeit auf Wasserproben optimiert, insbesondere auf natürliche Grundwasserproben. Zum anderen wurde eine gängige Aufbereitungsmethode für gelöstes Nitrat weiterentwickelt. Dabei wurden die Vorbereitungs- und Arbeitszeit der Denitrifizierermethode verkürzt, ohne die Genauigkeit der Messung negativ zu beeinflussen. Zu diesem Zweck wurden zwei bestehende Varianten der Methode miteinander kombiniert und modifiziert. Als Eignungsprüfung der Methoden zur Prozessidentifikation erfolgte eine exemplarische Feldstudie. Als Modellstandort diente ein Untersuchungsgebiet im Südosten Berlins. Der Grundwasserleiter des Standortes ist u. a. durch eine massive Kontamination von Ammonium gekennzeichnet. Im Untersuchungsgebiet wurde das sogenannte BIOXWAND-Verfahren entwickelt und zur Sanierung auf den Grundwasserleiter angewandt. Dabei handelt es sich um ein in-situ-Verfahren, wobei eine direkte Injektion von Sauerstoff in den Grundwasserleiter erfolgt um Nitrifikation zu begünstigen. Für die isotopengestützte Prozessidentifikation wurden im Rahmen dieser Arb, This thesis provides a method to identify the transformation of the nitrogen species ammonium and nitrate in polluted aquifers by analyzing the isotope ratios N-15 and O-18. Various preparation methods already exist, but are either labor intensive or time consuming and are therefore related with considerable costs. To achieve a broader applicability in environmental sciences, two simplified methods for the N-15 and O-18 stable isotope analysis of ammonium and nitrate in water were developed in this thesis. On the one hand, a precipitation method using sodium tetraphenylborate for the sample preparation of the N-15 isotope analysis for ammonium was modified, tested and validated. So far no studies could verify the applicability of this method for analysis of water samples containing ammonium. Therefore, the method was optimized for applicability to water samples, especially natural groundwater samples within this thesis. On the other hand, a common processing method for dissolved nitrate was optimized. The preparation and working time of the denitrification method was shortened without negatively affecting the accuracy of the measurement. For this purpose, two existing variants of the method were combined and modified. Furthermore, an exemplary field study was carried out to test the suitability of the preparation methods for process identification. A study area southeast of Berlin (Germany) containing an aquifer massively contaminated with ammonium served as a model location. Inside the area, the so-called BIOXWAND process, an in-situ process whereby oxygen is injected directly into the aquifer to promote nitrification, was developed and applied to the aquifer in terms of remediation. For isotope-based process identification, groundwater samples were taken twice a year from 2016 to 2019 from the BIOXWAND inflow and outflow and analyzed using the preparation methods developed. An analytical model was created for process identification.:VERZEICHNIS DER TABELLEN ......

Environmental pollution has become a global concern as consequence of industrializa-tion and urbanization. The ongoing subsurface contamination by dense non-aqueous phase liquids (DNAPLs) bears tremendous hazardous potential for humans and ecosys-tems including aquifer systems. Intended or accidental spill events have led to a vast number of registered sites affected by DNAPL type chemicals. Despite the existence of novel techniques for their exploration, characterization and remediation, economical constraints often limit efforts for risk prevention or reduction, so that information and data to characterize highly complex DNAPL contamination scenarios are often insuffi-cient and compensated by natural attenuation of groundwater-dissolved contaminant plumes. Especially, knowledge on the DNAPL source zone geometry (SZG) and source zone formation are critically required yet very scarce. Against the previously stated background, this cumulative doctoral dissertation critically examined the processes of DNAPL source zone formation at laboratory scale. A comprehensive literature review identified current limitations and open research questions in the latter research field, revealing evidence for the relevance of SZG for plume response at different scales. Giv-en only a limited number of published studies related to DNAPL source zone formation, two simplified experimental setups mimicking source zone formation in an initially fully water-saturated aquifer were developed and intensively tested. The performance of aqueous and non-wetting phase dyes was evaluated for DNAPL release into three non-consolidated porous media using reflective optical imaging in combination with a cus-tom-made image processing and analysis (IPA) framework. The latter suite allowed for the generation of physically plausible DNAPL saturation distributions with determinable level of uncertainty. Then, a limited number of DNAPL release experiments were per-formed under controlled ambient as well as wi

Leaching of soil salinity in irrigated and non-irrigated agriculture is crucial to ensure sustainable food production. Soil salinity is considered a global problem, since more than 800 million hectares (6% of the world's total area) worldwide are salt-affected. Generally, the regions affected by soil salinity also face water scarcity problems. Consequently, in these regions, even saline waters are considered to be essential resources for agriculture. The use of inefficient irrigation practices in regions that experience water scarcity, especially those using saline water, aggravates soil salinity problems. Therefore, in the context of these constraints and challenges, increasing the efficiency of water use for irrigation and leaching is necessary. An increasing interest in using drip irrigation systems (DI) is noticed in the current research that deals with water scarcity due to the benefits of applying water precisely in time and space. However, the traditional leaching guidelines, based on steady-state conditions, are not appropriate for DI. Therefore, the use of DI for leaching practices is still under question. The objectives of this study are (i) to better understand and assess the leaching process for common DI, and (ii) to develop a simulation-based optimization approach considering site-specific conditions for optimal DI design for salinity management. Accordingly, a new two-stage framework for optimizing leaching practices has been developed focusing on DI. The transient-state-based numerical model HYDRUS-2D was used for simulating water movement and solute transport processes for both stages. In the first stage, a general assessment tool for leaching practices in the form of “irrigation atlas” was created using two-dimensional (2D) numerical experiments. The atlas displays and compares the reclamation leaching results of (i) surface drip irrigation (SI), (ii) subsurface irrigation drip irrigation (SDI), (iii) sprinkler irrigation (S), and (iv) flood irriga

Im Jahr 2017 konsumierten knapp 2 Milliarden Menschen fäkalkontaminiertes Wasser. Das führte zu fast 500.000 Todesfällen. Gleichzeitig werden Trinkwasserressourcen ausgebeutet und schon heute sind 4 Milliarden Menschen von Wasserknappheit betroffen. In ländlichen Entwicklungsregionen stellt, aus technischer Sicht, die Desinfektion des Wassers eine der größten Herausforderungen für die Sicherstellung einer angemessenen Trinkwasserversorgung dar. In dieser Dissertation wird die technische sowie wirtschaftliche Machbarkeit einer solar betriebenen Anlage zur Chlorproduktion mittels Inlineelektrolyse (ECl2) als Alternative zur Lieferung und Dosierung von Chlorreagenzien analysiert und bewertet. Während der ECl2 wird das gesamte aufzubereitende Wasser durch eine Elektrolysezelle geleitet und das Chlor aus dem natürlichen Chloridgehalt des Wassers „inline“ gebildet. Unter opti-malen Betriebsbedingungen kann Trinkwasser aber auch aufbereitetes Abwasser ohne Zugabe durch Chemikalien desinfiziert werden. Damit würde die Lieferung von Chlorlösung dauerhaft entfallen. Zusätzlich wurde bewertet, inwiefern die Entfernung von Eisen und Arsen durch die ECl2 sowie der Abbau von organischen Spurenstoffen durch zusätzliche Kombination mit UV-Bestrahlung zur Radikalbildung verbessert werden kann. Alle vorgestellten Feldtests wurden in Langzeitstudien unter Realbedingungen in zukünftigen Anwendungsgebieten durchgeführt. Dadurch konnten mögliche Probleme im Be-trieb der Anlagen frühzeitig erkannt und Lösungsvorschläge erarbeitet werden. Die Erfahrungen aus dem Betrieb der ECl2-Systeme stellen dabei den größten Nutzen dieser Arbeit dar. Mit den Feldversuchen konnte gezeigt werden, dass Wasser durch die Anwendung von ECl2 sicher desinfiziert und gleichzeitig ausreichend vor Wiederverkeimung geschützt werden kann. Insbesondere die Kombination mit naturnahen Verfahren zur Vorbehandlung des zu desinfizierenden Wassers hat sich als sehr vorteilhaft für die langfristig sichere Anwendung des Ver, In 2017 nearly 2 billion people consumed water that was contaminated with feces, causing almost 500.000 diarrheal deaths. At the same time freshwater resources are depleted and water scarcity is already affecting 4 billion people worldwide. From a technical perspective the continuous supply of chemicals needed to ensure sufficient disinfection remains a major challenge in rural water treatment, and existing technical solutions to adequately disinfect water have failed in the past. This dissertation work evaluates the technical and economic feasibility of solar-driven inline electrolytic production of chlorine (ECl2), as an alternative to external chlorine supply. During ECl2 disinfection the water passes through the cell and chlorine is produced “inline” from the natural chloride content of the water. Under optimal conditions, no chemicals are required to safely disinfect drinking water and treated wastewater. Fur-thermore, the ability of ECl2 to enhance the removal of iron and arsenic from contaminated groundwater and to degrade Trace Organic Compounds (TOrC) when combined with UV were analyzed. All relevant tests have been conducted in long-term field studies in future deployment areas. This enabled the evaluation of potential operational challenges of such systems under real-world conditions. The experiences gathered from these field trials represent the major benefit of this dissertation work. The trials have shown that with ECl2 water can be safely disinfected and supplied with an adequate amount of residual disinfectant. Here, the combination with natural pre-treatment systems has proven to be beneficial. For the drinking water trial conducted in Uttarakhand, India, the ECl2 system received bank filtrate and achieved overall log re-moval rates of >5.0 for total coliforms and >3.5 for E. coli. For the disinfection of treated wastewater, the combination with a vertical flow constructed wetland (VFCW) has largely simplified the disinfection with chlorine by equal