Striving for universal access to sanitation through a portfolio approach

On November 13, Nature Water published an article in which the authors argue for a ‘portfolio approach’ to sanitation, in order to enhance the outcomes of sanitation solutions beyond their traditional focus on public health and environmental protection. Because the reality of current day urban living spaces is diverse, with different kinds of neighbourhoods and combinations of sewered and non-sewered sanitation solutions, a portfolio approach supports a diversity of solutions that are adapted to local conditions, and each have their own advantages and disadvantages. 

The fact that many urban areas feature combinations of sanitation systems is mostly not the result of conscious planning. However, there is potential for the coordination of different sanitation sector stakeholders in a city who are working on different solutions that are adapted to particular needs, and this holds the potential of balancing different kinds of desires outcomes with each other. The authors therefore propose moving away from the idea of a master plan for centralised sanitation systems and towards support for the design and implementation of multiple sanitation systems in parallel, including centralised sanitation systems, on-site sanitation systems, various types of onsite blackwater and greywater treatment, and household-level treatment. By doing so, resilient, accessible and resource-efficient sanitation solutions can be provided through a diversity of systems at various scales to optimise benefits including economic value, resource efficiency, climate resilience and human dignity.

Achieving the sanitation targets of the United Nations’ Sustainable Development Goals (SDGs) currently seems increasingly unlikely, with nearly three billion people predicted to be living without safely managed sanitation in 2030. Recent findings highlight sanitation’s interconnections with the economy, climate change, resource recovery and service equity, serving us with an opportunity to enhance the outcomes of sanitation. This, the authors claim, offers a paradigm shift from the conventional approach which relies on centralised systems, an approach which is widespread in the industrialised North, but which currently has limited coverage or effectiveness in the Global South. 

Rather than pursuing centralised systems, the authors argue for the coordinated design and implementation of multiple sanitation systems. Individually, these systems are unlikely to achieve the speed or scale required to address the global sanitation crisis effectively. By contrast, a portfolio approach integrates different sanitation systems along a continuum, allowing for hybrid or combined forms, such as the co-treatment of faecal sludge from onsite storage or household in situ treatment with centralised systems. However, the portfolio approach goes further by optimising the integration of these systems, to achieve multiple outcomes, including public health, environmental protection, climate resilience, resource recovery and equity.

The article lists the many benefits for both the North and South. For example, in terms of cost and distribution, centralised systems offer economies of scale, while on-site systems are associated with low capital costs but do involve costs later in the life cycle. Combining these solutions offers flexibility in relation to available resources and in response to urban growth patterns. From the perspective of the circular economy, the inflow of carbon, phosphorus and nitrogen into collection systems offer the opportunity for resource recovery. From the point of view of climate resilience, centralised systems may be vulnerable to disruptions that result from unpredictable water flows or energy supplies. 

The article touches on the challenges arising from the approach, concluding that in order to implement the portfolio approach, there is a need for broad collaboration among actors involved in various aspects of diverse sanitation service models.

The portfolio approach builds upon concepts such as ‘citywide inclusive sanitation’, which promotes a systematic consideration of diverse sanitation systems. At a workshop in Altanta in 2016, a number of key stakeholders in the sector met to discuss the relative lack of progress in the provision of sanitation services in 36 lower income countries. Out of this discussion emerged the concept of citywide inclusive sanitation, which was described as a situation in which: 

Everyone benefits from adequate sanitation service delivery outcomes; human waste is safely managed along the whole sanitation service chain; effective resource recovery and re-use are considered; a diversity of technical solutions is embraced for adaptive, mixed and incremental approaches; and onsite and sewerage solutions are combined, in either centralized or decentralized systems, to better respond to the realities found in developing country cities.

Since 2018, the World Bank’s Water Global Practice, in partnership with sector development partners (including The Bill & Melinda Gates Foundation, Emory University, The University of Leeds, WaterAid and Plan International) are working jointly on the implementation of the Citywide Inclusive Sanitation (CWIS) Initiative.

Citywide Inclusive Sanitation (CWIS) aims to shift the urban sanitation paradigm, aiming to ensure everyone has access to safely managed sanitation by promoting a range of solutions—both onsite and sewered, centralised or decentralised—tailored to the realities of the world's burgeoning cities. CWIS means focusing on service provision and its enabling environment, rather than on building infrastructure. CWIS indicators are mapped to the six areas of the CWIS Service Framework—Equity, Safety, Sustainability, Responsibility, Accountability, and Resource Planning and Management.