Achieving sustainable wastewater treatment through Nexus thinking

This present habilitation thesis in wastewater systems explores the theoretical and practical implications of achieving sustainability through and in wastewater treatment. It herby uses the discussions on circularity, sustainability and nexus thinking while investigating their relationship amongst each other and in their relation to wastewater treatment. This thesis consists of seven main chapters. Chapter 1 provides an overview of the approach in which the present manuscript delves into the aspects of circularity, sustainability and nexus concepts and wastewater treatment. Chapter 2 to 5 contain the manuscripts that relate to (a) conceptual considerations, (b) examples of circularity, (c) sustainability assessments and (d) nexus applications. Chapter 6 provides a series of lessons learned from the collated findings. Chapter 7 holds the appendix with supplemental information from the respective manuscripts. The work is based on a variety of publications that the author and her team members produced primarily between January 2016 and October 2019 (and in part until the submission of this thesis). While they include 5 published first-author peer-reviewed publications some sections also contain further relevant co-authored publications. Water security is key for a sustainable world. Wastewater can play a critical role towards provisioning water sustainably to address water scarcity and water stress. However, wastewater treatment is currently itself not sustainable. For wastewater treatment to be put on a sustainable footing, systemic change of the sector and the way wastewater is viewed needs to occur. Wastewater treatment can provide a series of resources for circular use – with nature-based solutions offering co-benefits over grey infrastructure that extend to other nexus sectors such as food and energy. However, circularity does not necessarily equate with sustainability. Environmental components are just one of the three dimensions of sustainability, but data for indicators for social and economic aspects of wastewater treatment are scarce. Moving towards sustainable solutions may only be possible by employing tools that step away from an ever-better understanding of current systems and shifting towards modes of analysis that help generate target and transformation knowledge in inter- and transdisciplinary research and project settings. These views mandate a radical revision of current curricula of engineers and other disciplines to include courses on social, economic and environmental dimensions of sustainability. Training in designing, conducting and evaluating participatory processes that include a variety of stakeholders may significantly improve future generations’ capacities to design, construct, and operate sustainable wastewater treatment systems that provide treated wastewater as a sustainable source of water in a water secure world.:ABSTRACT vii ZUSAMMENFASSUNG (ABSTRACT in German) ix ACKNOWLEDGMENTS xi 1 Introduction 2 1.1 Scope 2 1.2 The structure of this work 8 1.3 References 10 2 Conceptual explorations 14 2.1 Learning from Integrated Management Approaches to Implement the Nexus 15 2.1.1 Introduction 16 2.1.2 Methods 19 2.1.3 Results 21 2.1.4 Discussion 26 2.1.5 Conclusion 27 2.1.6 References 29 2.2 Making the Water–Soil–Waste Nexus Work: Framing the Boundaries of Resource Flows 33 2.2.1 Introduction 34 2.2.2 An Overview of Integrated Approaches Related to the WSW Nexus 36 2.2.3 The System Boundaries of Integrated Environmental Management Approaches 38 2.2.4 What Is Different This Time?—The Boundary of the Water–Soil–Waste Nexus System 41 2.2.5 Illustrating the Boundaries of the WSW Nexus System—Case Studies 43 2.2.6 Conclusions 48 2.2.7 References and Notes 50 3 Examples of circularity 56 3.1 The Role of Constructed Wetlands for Biomass Production within the Water-Soil-Waste Nexus 59 3.1.1 Introduction 60 3.1.2 Methods 63 3.1.3 Results and discussion 63 3.1.4 Conclusions 68 3.1.5 References 70 3.2 Constructed Wetlands for Resource Recovery in Developing Countries 73 3.2.1 Introduction 74 3.2.2 Methods 76 3.2.3 Results 80 3.2.4 Discussion 91 3.2.5 Conclusions 99 3.2.6 References 102 4 Assessing sustainability of wastewater systems 110 4.1 Assessing Sustainability of Wastewater Management Systems in a Multi-Scalar, Transdisciplinary Manner in Latin America 113 4.1.1 Introduction 114 4.1.2 Materials and Methods 116 4.1.3 Results 124 4.1.4 Discussion 129 4.1.5 Conclusion 132 4.1.6 References 134 4.2 Selecting Sustainable Sewage Sludge Reuse Options through a Systematic Assessment Framework: Methodology and Case Study in Latin America 137 4.2.1 Introduction 138 4.2.2 Methods 139 4.2.3 Results and discussion 141 4.2.4 Conclusion 154 4.2.5 References 156 5 Applying the Nexus 160 5.1 Considering Resources Beyond Water: Irrigation and Drainage Management in the Context of the Water–Energy–Food Nexus 161 5.1.1 Introduction 163 5.1.2 Integrating resource management through Nexus thinking 165 5.1.3 Assessing the negative and positive environmental effects of irrigation, and the provision of ecosystem services 169 5.1.4 The role of stakeholders in governing irrigation 171 5.1.5 Conclusion 173 5.1.6 References 175 5.2 Co-generating knowledge in nexus research for sustainable wastewater management 177 5.2.1 Introduction 178 5.2.2 Material and Methods 180 5.2.3 Results 184 5.2.4 Discussion 202 5.2.5 Conclusions 204 5.2.6 References 206 6 Lessons learned and outlook 210 6.1 Increased circularity does not equate in increased sustainability. 212 6.2 Data scarcity hampers quantitative knowledge generation. 214 6.3 Moving from systems’ understanding to comprehensive knowledge generation for systemic change. 217 6.4 Participation and inclusion of stakeholders is important and should not be an afterthought. 218 6.5 References 221 7 Supplemental Information (SI)/Supplemental Material (SM) 226 7.1 SI for 4.1 ‘Assessing Sustainability of Wastewater Management Systems in a Multi-Scalar, Transdisciplinary Manner in Latin America’ 226 Appendix A 226 Appendix B 233 Appendix C 240 Appendix D 241 Appendix E 243 Appendix F 251 7.2 SI for 4.2 ‘Selecting Sustainable Sewage Sludge Reuse Options through a Systematic Assessment Framework: Methodology and Case Study in Latin America’ 256 7.3 SI for 5.1 ‘Co-generating knowledge in nexus research for sustainable wastewater management’ 261 7.3.1 SM1: Expert interview questionnaire assessing information on stakeholder’s perspectives. 261 7.3.2 SM2: Wickedness Analysis questions 264 7.3.3 SM3: Detailed results of the stakeholder perspective of wastewater treatment in each case 265 7.3.4 SM4: Detailed responses to the workshop/training evaluations 272 8 Contribution of the author in collaborative publications 283 9 Eidesstattliche Versicherung 285Diese Habilitationsschrift untersucht die theoretischen und praktischen Implikationen der Erreichung von Nachhaltigkeit durch und in der Abwasserbehandlung. Sie nutzt die Diskussionen über Kreislaufwirtschaft, Nachhaltigkeit und Nexus-Denken und untersucht deren Beziehung untereinander und in ihrem Verhältnis zur Abwasserbehandlung. Dieses Manuskript besteht aus sieben Hauptkapiteln. Kapitel 1 gibt einen Überblick über den Ansatz, in dem das vorliegende Manuskript die Aspekte der Kreislaufwirtschaft, Nachhaltigkeit und Nexus-Konzepte und Abwasserbehandlung untersucht. Kapitel 2 bis 5 enthält die Manuskripte, die sich auf (a) konzeptionelle Überlegungen, (b) Beispiele für Kreislaufwirtschaft, c) Nachhaltigkeitsbewertungen und (d) Nexusanwendungen beziehen. Kapitel 6 enthält eine Reihe von Einsichten, die aus den gesammelten Erkenntnissen gezogen wurden. Das letzte Kapitel enthält die Zusatzdaten und -informationen einiger der Artikel. Die Arbeit basiert auf einer Vielzahl von Publikationen, die die Autorin und ihre Teammitglieder hauptsächlich zwischen Januar 2016 und Oktober 2019 (und teilweise bis zur Einreichung dieser Arbeit) erstellt haben. Während sie 5 veröffentlichte Erstautoren-Peer-Review-Publikationen umfassen, enthalten manche Abschnitte auch weitere relevante, mitverfasste Veröffentlichungen. Wassersicherheit ist unumgänglich für eine nachhaltige Welt. Abwasser kann eine Schlüsselrolle bei der Bereitstellung einer nachhaltigen Wasserquelle spielen, um Wasserknappheit und Wasserstress zu bewältigen. Die Abwasserbehandlung selbst ist jedoch derzeit nicht nachhaltig. Damit die Abwasserbehandlung auf eine nachhaltige Grundlage gestellt werden kann, müssen die Sektoren und die Art und Weise, wie Abwasser betrachtet wird, verändert werden. Die Abwasserbehandlung kann eine Reihe von Ressourcen für die Kreislaufwirtschaft bereitstellen – naturbasierte Lösungen bieten weitere Vorteile gegenüber grauer Infrastruktur, die sich auf andere Nexus-Sektoren wie Nahrung und Energie erstrecken. Kreislaufwirtschaft ist jedoch nicht unbedingt gleichbedeutend mit Nachhaltigkeit. Umweltkomponenten sind nur eine der drei Dimensionen der Nachhaltigkeit, aber Daten für Indikatoren für soziale und wirtschaftliche Aspekte der Abwasserbehandlung sind rar. Der Übergang zu nachhaltigen Lösungen ist möglicherweise nur möglich, wenn Instrumente eingesetzt werden, die sich von einem immer besseren Verständnis aktueller Systeme entfernen und sich in Richtung Analysemodi bewegen, die dazu beitragen, Ziel- und Transformationswissen in inter- und transdisziplinären Forschungs- und Projektumgebungen zu generieren. Diese Ergebnisse schreiben eine radikale Überarbeitung der aktuellen Lehrpläne von Ingenieuren und anderen Disziplinen vor, um Kurse über soziale, wirtschaftliche und ökologische Dimensionen der Nachhaltigkeit aufzunehmen. Schulungen in der Konzeption, Durchführung und Bewertung partizipatorischer Prozesse, die eine Vielzahl von Akteuren einbeziehen, können die Kapazitäten der zukünftigen Generation zur Planung, Konstruktion und zum Betrieb nachhaltiger Abwasserbehandlungssysteme, die behandeltes Abwasser als nachhaltige Wasserquelle in einer wassersicheren Welt bereitstellen, erheblich verbessern.:ABSTRACT vii ZUSAMMENFASSUNG (ABSTRACT in German) ix ACKNOWLEDGMENTS xi 1 Introduction 2 1.1 Scope 2 1.2 The structure of this work 8 1.3 References 10 2 Conceptual explorations 14 2.1 Learning from Integrated Management Approaches to Implement the Nexus 15 2.1.1 Introduction 16 2.1.2 Methods 19 2.1.3 Results 21 2.1.4 Discussion 26 2.1.5 Conclusion 27 2.1.6 References 29 2.2 Making the Water–Soil–Waste Nexus Work: Framing the Boundaries of Resource Flows 33 2.2.1 Introduction 34 2.2.2 An Overview of Integrated Approaches Related to the WSW Nexus 36 2.2.3 The System Boundaries of Integrated Environmental Management Approaches 38 2.2.4 What Is Different This Time?—The Boundary of the Water–Soil–Waste Nexus System 41 2.2.5 Illustrating the Boundaries of the WSW Nexus System—Case Studies 43 2.2.6 Conclusions 48 2.2.7 References and Notes 50 3 Examples of circularity 56 3.1 The Role of Constructed Wetlands for Biomass Production within the Water-Soil-Waste Nexus 59 3.1.1 Introduction 60 3.1.2 Methods 63 3.1.3 Results and discussion 63 3.1.4 Conclusions 68 3.1.5 References 70 3.2 Constructed Wetlands for Resource Recovery in Developing Countries 73 3.2.1 Introduction 74 3.2.2 Methods 76 3.2.3 Results 80 3.2.4 Discussion 91 3.2.5 Conclusions 99 3.2.6 References 102 4 Assessing sustainability of wastewater systems 110 4.1 Assessing Sustainability of Wastewater Management Systems in a Multi-Scalar, Transdisciplinary Manner in Latin America 113 4.1.1 Introduction 114 4.1.2 Materials and Methods 116 4.1.3 Results 124 4.1.4 Discussion 129 4.1.5 Conclusion 132 4.1.6 References 134 4.2 Selecting Sustainable Sewage Sludge Reuse Options through a Systematic Assessment Framework: Methodology and Case Study in Latin America 137 4.2.1 Introduction 138 4.2.2 Methods 139 4.2.3 Results and discussion 141 4.2.4 Conclusion 154 4.2.5 References 156 5 Applying the Nexus 160 5.1 Considering Resources Beyond Water: Irrigation and Drainage Management in the Context of the Water–Energy–Food Nexus 161 5.1.1 Introduction 163 5.1.2 Integrating resource management through Nexus thinking 165 5.1.3 Assessing the negative and positive environmental effects of irrigation, and the provision of ecosystem services 169 5.1.4 The role of stakeholders in governing irrigation 171 5.1.5 Conclusion 173 5.1.6 References 175 5.2 Co-generating knowledge in nexus research for sustainable wastewater management 177 5.2.1 Introduction 178 5.2.2 Material and Methods 180 5.2.3 Results 184 5.2.4 Discussion 202 5.2.5 Conclusions 204 5.2.6 References 206 6 Lessons learned and outlook 210 6.1 Increased circularity does not equate in increased sustainability. 212 6.2 Data scarcity hampers quantitative knowledge generation. 214 6.3 Moving from systems’ understanding to comprehensive knowledge generation for systemic change. 217 6.4 Participation and inclusion of stakeholders is important and should not be an afterthought. 218 6.5 References 221 7 Supplemental Information (SI)/Supplemental Material (SM) 226 7.1 SI for 4.1 ‘Assessing Sustainability of Wastewater Management Systems in a Multi-Scalar, Transdisciplinary Manner in Latin America’ 226 Appendix A 226 Appendix B 233 Appendix C 240 Appendix D 241 Appendix E 243 Appendix F 251 7.2 SI for 4.2 ‘Selecting Sustainable Sewage Sludge Reuse Options through a Systematic Assessment Framework: Methodology and Case Study in Latin America’ 256 7.3 SI for 5.1 ‘Co-generating knowledge in nexus research for sustainable wastewater management’ 261 7.3.1 SM1: Expert interview questionnaire assessing information on stakeholder’s perspectives. 261 7.3.2 SM2: Wickedness Analysis questions 264 7.3.3 SM3: Detailed results of the stakeholder perspective of wastewater treatment in each case 265 7.3.4 SM4: Detailed responses to the workshop/training evaluations 272 8 Contribution of the author in collaborative publications 283 9 Eidesstattliche Versicherung 28