Urban sanitation is a basic service essential for public and environmental health. Incorporating various advances over the past two decades, the urban sanitation agenda has evolved towards the paradigm shift of Citywide Inclusive Sanitation (CWIS). Overall, CWIS aims at providing equitable and sustainable sanitation services and is closely linked to Sustainable Development Goal (SDGs) 6 on clean water and sanitation and directly and indirectly benefits several other SDGs. Since its inception in 2016, CWIS has evolved through various research and implementation experiences, resulting in four conceptual frameworks that redefine sanitation as a service delivery process, emphasizing the entire sanitation value chain and the coexistence of sewered and non-sewered technologies. This discussion paper draws on 77 journal articles and grey literature explicitly linked to CWIS, reviews the state of the art on the topic by comparing the four prominent CWIS frameworks and by identifying key advances, current gaps, and emerging issues to inform ways forward towards a more unified CWIS framework.

Climate change, rapid urbanization and other grand challenges increasingly force cities to rethink their urban (water) infrastructure. In particular, decentralized urban water management solutions, which can recover valuable resources close to the source are increasingly applied to remediate water scarcity, sanitation or environmental pollution challenges. Yet, although interesting demonstration projects with decentralized solutions (from here on labeled ‘decentralized UWM solutions’) are underway in several world regions, actors developing and implementing this transformative innovation are not effectively coordinating their efforts and sharing the latest knowledge. While effective technologies, business models, or regulative frameworks increasingly exist that could inform, inspire and improve similar activities elsewhere, details of local successes and failures are still (too) rarely shared or transferred across space. Drawing from experience on the mainstreaming of other transformative infrastructure solutions (like renewable energies, electric mobility or circular waste management), we posit that the global diffusion of decentralized UWM solutions has been significantly slowed down by this lack of interaction among key stakeholders, and the resulting lack of an effective innovation ecosystem.

Climate change, rapid urbanization and other grand challenges increasingly show that urban water and wastewater man-agement needs to be deeply rethought. A transformative shift is needed away from linear end-of-pipe to more circular system designs. Actors around the world have thus started developing decentralised urban wastewater treatment and reuse systems (DUWTRS). DUWTRS improve the flexibility, resilience and circularity of water and sanitation infrastructure and can thus play a key role in developing more sustainable cities. Yet, despite their high potential in solving multiple urban development challenges at once, only a few cities worldwide have successfully implemented them at scale. We thus lack well-documented templates and best practices of successful DUWTRS implementation. The Lighthouse Project aimed at filling this gap by assessing promising examples from around the world. To generate practice-oriented lessons, we compared six projects at different scales (city-wide vs. neighbourhood), in different contexts (high-income vs. low-/middle-income) and using different technological set-ups. We selected four neighbourhood-scale and two city-scale projects, equally distributed across high- and middle-income contexts. Data was collected between November 2021 and August 2022 through an extensive literature review and more than 100 semi-structured expert interviews. An integrative assess-ment framework was developed and used to derive key success conditions for DUWTRS implementation.

The Jenfelder Au in Hamburg, Germany is a sustainable city development project, served by the "Hamburg Water Cycle" (HWC), a spearheading template for resource-recovery from source-separated water and wastewater, first of its kind at neighbourhood scale. [...]

Nirvana Country Township is a high-end residential colony in Haryana State, which reuses treated effluent from on-site wastewater treatment facilities for urban greening in several residential areas. [...]

The H+ area in Helsingborg, Sweden, is a sustainable city development project, served by "Tre-Rör-Ut" (Three-Pipes-Out), a world-unique source-separation and resource-recovery system for water, wastewater and food waste. [...]

San Francisco is spearheading the city-wide installation of onsite non-potable water reuse systems (ONWS). Through a city ordinance, local authorities have induced a quickly growing ONWS market and initiated stakeholder networks that support the diffusion of ONWS solutions in San Francisco and beyond. [...]

Bengaluru represents a globally unique context for the diffusion of on-site wastewater treatment and reuse systems (ONWS). Local authorities have introduced a series of mandates that triggered a dynamically evolving mass-market for ONWS. [...]

In recent years, shared facilities have contributed substantially to increased access to sanitation in urban areas. While shared sanitation is often the only viable option in densely-populated, low-income urban areas, it is currently considered a "limited" solution by the international community. In this paper, we analyze the conditions under which shared sanitation could be considered of adequate quality and propose a set of indicators associated with sanitation quality to be included in national household surveys. We conducted a survey with 3600 households and 2026 observational spot-checks of shared and individual household toilets in Kisumu (Kenya), Kumasi (Ghana), and Dhaka (Bangladesh). We develop a composite sanitation quality outcome measure based on observational data. Using regression analysis, we identify self-reported indicators that correlate with the spot-checked composite measure and are, therefore, robust with regard to reporting bias. Results show that (pour-) flush toilets are a highly informative indicator for sanitation quality compared to other toilet technologies. In contrast to previous arguments and depending on the context, sharing a toilet has a comparatively lower correlation with sanitation quality. Toilets still show good quality if shared among only 2-3 households. Toilet location and lighting, as well as the presence of a lockable door, are equally strong indicators for sanitation quality and could serve as alternative indicators. The findings suggest that the sanitation service levels defined by the WHO and UNICEF might be reconsidered to better capture the quality of sanitation facilities in low-income urban settlements.

Shared sanitation has immensely contributed to sanitation access in urban areas. However, due to the lack of quality standards within Sustainable Development Goal #6 and the WHO/UNICEF Joint Monitoring Programme (JMP), which evaluates progress on the SDGs, shared sanitation is at best considered a 'limited' solution. This policy brief presents the main results of the Quality Indicators of Shared Sanitation (QUISS) project: a three-country comparative mixed-methods study that identifies the key criteria of what constitutes ‘acceptable quality’ shared toilets in low-income urban contexts and provides recommendations for strengthening the acceptability, functionality and sustainability of shared sanitation facilities.

NoMix toilets separate urine and feces at the source and are a promising resource recovery technology. However, design issues hamper the transformation from unattractive to aspirational products. Little effort has been done to design toilets that account for physiological differences, leading to adverse effects on user-friendliness and urine separation efficiency. We used infrared recordings to assess gender-specific urination practices. Based on field data, we developed the Urinator, a simple device that allows simulating male and female urine streams. This supports engineers in developing more user- and gender-friendly and reuse-oriented sanitation technologies.

Shared sanitation has immensely contributed to sanitation access in urban areas, but is at best considered a "limited" solution due to the lack of quality standards within Sustainable Development Goal #6.
This policy brief presents the main results of the QUISS project (Quality Indicators of Shared Sanitation), a three-country com-parative mixed-methods study that identified the key criteria of what constitutes "accept-able quality" shared toilets in urban low-income contexts and provides recommen-dations for strengthening the acceptability, functionality and sustainability of shared sanitation facilities.

This policy brief presents the main results of a three-country study on Quality Indicators of Shared Sanitation (QUISS). QUISS assessed when shared sanitation is acceptable and what is needed to establish minimal acceptability requirements. Qualitative and quantitative data were collected in Ghana, Kenya and Bangladesh in 2019. This brief highlights the research findings for Bangladesh and provides recommendations for strengthening the acceptability, functionality and sustainability of Bangladesh’s shared sanitation facilities in low-income urban settlements.

This policy brief presents the main results of a three-country study on Quality Indicators of Shared Sanitation (QUISS). QUISS assessed when shared sanitation is acceptable and what is needed to establish minimal acceptability requirements. Qualitative and quantitative data were collected in Ghana, Kenya and Bangladesh in 2019. This brief highlights the research findings for Kenya and provides recommendations for strengthening the acceptability, functionality and sustainability of Kenya’s shared sanitation facilities in low-income urban settlements.

This policy brief presents the main results of a three-country study on Quality Indicators of Shared Sanitation (QUISS). QUISS assessed when shared sanitation is acceptable and what is needed to establish minimal acceptability requirements. Qualitative and quantitative data were collected in Ghana, Kenya and Bangladesh in 2019. This brief highlights the research findings for Ghana and provides recommendations for strengthening the acceptability, functionality and sustainability of Ghana’s shared sanitation facilities in low-income urban settlements.

Shared sanitation facilities (SSFs) have contributed considerably to sanitation access in many low-income settlements. While many SSFs are of unacceptable quality, others have been found to be a hygienically safe and a socially and economically viable sanitation option. Within its framework, the WHO/UNICEF Joint Monitoring Programme (JMP), evaluating progress on the Sustainable Development Goals, considers shared sanitation as 'limited sanitation'. Overall, there is uncertainty about the criteria to distinguish between unacceptable and acceptable quality of SSF. In our study, we used a user-centred qualitative approach in low-income urban settlements in Kumasi (Ghana), Kisumu (Kenya) and Dhaka (Bangladesh) and conducted 17 focus group discussions to evaluate how SSF users define the quality of an SSF and which aspects they consider as essential priorities for good-quality SSF. In descending order, the user priorities identified are: immediate water access, cleanliness, gender-separated toilets, flush toilets, lighting for use at night, lockable/functional doors, tiling, handwashing stations and privacy. This list can serve as input to the sanitation guidelines, local building codes and the establishment of minimum national sanitation standards. SSFs that meet these minimal criteria can then be promoted as an incremental step when individual household facilities are not feasible.