Estimating Safely Managed Sanitation in Urban Areas; Lessons Learned From a Global Implementation of Excreta-Flow Diagrams

Abstract

The urban population will rise to 6.7 billion by 2050. The United Nations has committed to provide everyone with safely managed sanitation, but there is limited understanding of the scale of the challenge. This paper describes a methodology for rapid assessment of sanitation in cities including a graphical representation (a shit-flow diagram or SFD) and reports on findings from implementation in 39 cities. The SFD provides high level information for planning purposes covering the entire sanitation system in a city. More than half of the human excreta produced in these cities is not safely managed. The most significant portions of the unsafely managed excreta are: (i) contents of pits and tanks which are not emptied and are overflowing, leaking, or discharging to the surrounding environment (14%); (ii) contents of pits and tanks which are emptied but not delivered to treatment (18%); (iii) fecal sludge and supernatant delivered to treatment but not treated (3%); (iv) wastewater in sewers not delivered to treatment (14%); and (v) wastewater delivered to treatment but not treated (6%). Many cities currently relying on onsite sanitation for safe storage, particularly in Africa, will need new strategies as populations grow. Containment systems that discharge to open drains are common in some Asian cities; these pose a public health risk. Dumping of excreta is widespread and there is a lack of realistic performance data on which estimates of the extent and effectiveness of treatment can be made. The SFD production process can be challenging due to a lack of data and low technical capacity in cities. There is often uncertainty over terminology and over the status of infrastructure. Formalizing definitions for the SFD preparation process was found to be useful in overcoming capacity constraints in cities. The SFD produces a credible snapshot of the sanitation situation in a city. The paper provides evidence of the urgent need for improved management and monitoring of urban sanitation in cities around the world and highlights the role of the SFD as a planning tool.

Costs, Climate and Contamination: Three Drivers for Citywide Sanitation Investment Decisions

“…Recent WHO (2018) design guidelines require that wet pit latrines only be used in areas of deep groundwater, and that if groundwater is used for domestic water supply then: pits should be located at least 1.5 m above the water table; 15 m horizontally down-gradient from the water supply; no graywater should be added; and septic tanks should discharge to a soak pit or leach field. However, appropriately designed soak-aways and absorption trenches are typically missing in dense urban areas or may be used in unfavorable groundwater conditions (high water table, highly porous soils) (World Bank, 2015;Peal et al, 2020). In addition, research has found that the travel distance of pathogens varies widely, questioning the validity of generalized separation guidance between pits and wells (Williams and Overbo, 2015).…”

Safely Managed On-Site Sanitation: A National Assessment of Sanitation Services and Potential Fecal Exposure in Indonesia

“…According to the Joint Monitoring Programme (JMP), a safely managed sanitation service means that people should use improved sanitation facilities that are not shared with other households, and the excreta produced should be treated and disposed in situ, stored temporarily, and then emptied and transported to treatment off-site or transported through a sewer with wastewater and then treated off-site. The ambition for a higher level of service-through technical improvement of existing sanitation systems or in the design and the implementation of new ones to reduce these public health risks is supported by the conclusions of recent WASH trials [2] and the development of tools such as the Shit/Excreta Flow Diagram [3] and the Pathogen Hazard Diagram [4].…”

“…In Indonesia, septic tanks, leach pit latrines, and lined pit latrines are widely used by households [4,17,18]. The term 'septic tank' is widely used in Indonesia to refer to all on-site systems including those that are not technically septic tanks [3,17]. In a watertight septic tank, the liquid effluent can only leave through the effluent pipe; there is no leakage.…”

Evaluation of User Experiences for the Clean Team Ghana Container-Based Sanitation Service in Kumasi, Ghana

“…Container Based Sanitation (CBS) is a system where sealed toilet containers are regularly collected from households and transported to treatment facilities. CBS, if properly managed, ensures full containment of faecal waste, by contrast with onsite-infiltration systems (latrines, septic tanks) which usually discharge contaminated liquid effluent locally (Peal et al, 2020). Several CBS business models have emerged globally since 2010 providing a viable, low-cost sanitation option.…”