While sanitation is fundamental for health and wellbeing, cities of all sizes face growing challenges in providing safe, affordable and functional sanitation systems that are also sustainable. Factors such as limited political will, inadequate technical, financial and institutional capacities and failure to integrate safe sanitation systems into broader urban development have led to a persistence of unsustainable systems and missed opportunities to tackle overlapping and interacting urban challenges. This paper reviews challenges associated with providing sanitation systems in urban areas and explores ways to promote sustainable sanitation in cities. It focuses on opportunities to stimulate sustainable sanitation approaches from a resource recovery perspective, generating added value to society while protecting human and ecosystem health. We show how, if integrated within urban development, sustainable sanitation has great potential to catalyse action and contribute to multiple sustainable development goals.

The sustainable development of cities is threatened by a worldwide water crisis. Improved social learning is urgently needed to transform urban water governance and make it more integrated and adaptive. However, empirical studies remain few and fragmented. Therefore, the aim of this paper is to analyse how social learning has supported or inhibited sustainable transformations in urban water governance.On the basis of multiple case studies conducted in urban, flood-prone areas in Colombia, the Philippines, South Africa, India, and Sweden, we study learning processes related to different aspects of water management and governance.Our results show that transformations in water governance are often triggered by crises, whereas other potentials for transformation are not tapped into. Furthermore, learning is often inhibited by "lock-ins" created by powerful actors. We conclude that there is a need for more proactive design of governance structures for triple-loop learning that take into account the identified barriers and supporting principles.

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Although sanitation systems are fundamental for human health and sustainable development, limited focus has been placed on their contributions to climate mitigation and adaptation. Climate change threatens existing systems, as well as efforts to increase services for 2.3 billion people who lack even a basic sanitation service. At the same time, the sanitation and wastewater sector directly produces emissions associated with breakdown of organic matter, and treatment processes require large energy inputs. In light of these challenges, we describe gaps in how sanitation is being addressed in mitigation and adaptation, discuss how this results in little inclusion of sanitation in climate policy and financing at the global level, and implications of these gaps for different sanitation systems and geographic regions. Finally, we describe the need for planning frameworks to facilitate integration of climate change into sanitation policy and programming. This will be critical to increasing understanding of sanitation and climate change linkages among stakeholders, and more effectively including sanitation in climate action.

Globally, more than 60% of the human population live without safely managed sanitation services or even lack access to basic sanitation facilities. In addition, most of the wastewater produced in the world is discharged without proper treatment. Integrated approaches are needed to address these issues and curb the resulting adverse impacts on public health and the environment, and associated societal economic losses. The United Nations 2030 Agenda for Sustainable Development provides an important framework towards more sustainable sanitation development, in terms of both safe sanitation access and wastewater management. Innovative solutions that treat and enable productive safe use of water, and facilitate recovery of nutrients and organic matter from waste resources are booming. Some examples of trends are decentralized solutions, separation of waste flows, low-or no-flushing toilets, and converting faecal sludge to energy. These alternative technologies show huge potential to address many development challenges, contributing to multiple sustainable development goals but achieving upscaling has proved to be a major challenge. A paradigm shift to 'treatment for reuse' instead of 'treatment for disposal' is already taking place in the wastewater sector. Nevertheless, a better understanding of driving forces and enabling environments, new organizational models based on more service-oriented sanitation provision, and highlighting potential multiple societal benefits to attract investments from new sectors are identified areas that need further attention.