Decision-support for adaptive and sustainable urban wastewater system management in the face of uncertainty
- Autores: Antonia Hadjimichael
- Directores de la Tesis: Joaquim Comas Matas (dir. tes.), Lluís Corominas Tabares (dir. tes.)
- Lectura: En la Universitat de Girona ( España ) en 2016
- Idioma: español
- Tribunal Calificador de la Tesis: Peter Vanrolleghem (presid.), Jean-Marc Neumann (secret.), Aad Oomens (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia y Tecnología del Agua por la Universidad de Girona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
With sustainable development as the new overarching goal, urban wastewater system (UWS) managers are now being asked to take all social, economic, technical and environmental facets related to their decisions into account. In this complex decision- making environment, uncertainty can be formidable. Uncertainty is present both in the ways the system is interpreted stochastically, but also in its natural ever-shifting behaviour. This inherent uncertainty leads to the conclusion that better decisions will be made if the decision-making process is adaptive and iterative. UWS decision-support frameworks exist in the literature, but none of them effectively addresses all these needs. Hence, there is a need for an adaptive framework that supports UWS management by addressing aspects of sustainability and uncertainty of various types. The development of such a framework is the main outcome of this work, and is supported by two demonstrative applications presented in this thesis.
The thesis describes a conceptual framework that can be used to assess environmental and socio-economic impacts of UWS management options under various conditions, both present and future. This is achieved by establishing an adaptive management framework for decision-support that evaluates and compares alternative solutions. Socio-economic aspects such as externalities are taken into account, along with other traditional criteria as necessary. Robustness, reliability and resilience measures are used to evaluate the performance of the system given inputs representing future and present conditions. Also included is a valuation uncertainty analysis that incorporates uncertain valuation assumptions in the decision-making process.
As part of this work, the framework was applied to the Congost UWS in Catalonia, Spain to demonstrate its applicability to a real-world challenge. The Congost UWS represents a typical problem often faced by managers: poor river water quality, an increasing population and more stringent water quality legislation. The application of the framework made use of: i) a Cost Benefit Analysis (CBA) including monetised environmental benefits and damages; ii) a Robustness Analysis of system performance against potential future conditions; iii) Reliability and Resilience Analyses of the system given contextual variability; and iv) a Valuation Uncertainty Analysis of model parameters. Several reactor volume expansions were evaluated following the framework, with the evaluations making use of electricity price projections, population growth projections and climate change projections. The results of the framework application suggest that the installation of larger volumes would give rise to increased net present values (NPVs) despite larger capital costs. The results also indicate that larger volumes would exhibit increased robustness and resilience. The results were highly dependent on the population estimates, as they appeared to affect the estimated NPVs the most, followed by electricity prices and climate change projections.
An alternative application of the sustainability assessment part of the framework is also presented. This application evaluates the sustainability aspects of four options proposed for upgrading of the UWS of Eindhoven and the Dommel River in the Netherlands, against the base-case “do-nothing” option. The options aim to reduce the overall environmental impact of the Eindhoven UWS by targeting river dissolved oxygen (DO) depletion and ammonia peaks, reducing combined sewer overflows (CSOs) and enhancing nutrient removal. The options were evaluated using Life Cycle Analysis (LCA) with the receiving river included in the boundaries. An integrated model of the UWS has proved to be a powerful tool to analyse and evaluate the proposed measures and is employed in this study. An uncertainty analysis of the estimated impacts was performed to support the outcomes. The study also used the economic concept of shadow prices to assign relative weights of socio-economic importance to the estimated life cycle impacts. This novel integration of tools complements the assessments of this UWS with the inclusion of long-term global environmental impacts and the investigation of trade-offs between different environmental impacts through a single monetary unit.
The objectives of this work have been fulfilled within this thesis. The presented framework is expected to be a valuable tool for the next generation of water decision-making and, the two applications demonstrate novel integrations of metrics and methods valuable for UWS analysis and future work.
