Proof of Concept of Estimates of the Unsafe Return of Human Excreta to the Environment

This is a Bill and Melinda Gates Foundation project funded for a duration of 4.5 years. The multifaceted project explores:

  • Effectiveness of local sanitation technologies in reducing pathogen hazards in human waste before release to the environment
  • Development and testing of Community Hazard Flow Models for local sanitation planning, with the aim of promoting better decision-making and priority setting of sanitation interventions from the public health perspective

Water Institute conducted extensive fieldwork in India including: sampling sites along the sanitation service chain (FSM) chain; collecting data on fecal pathogen hazards; assessing design, construction, and structural integrity of the existing sanitation technologies and their performance in terms of pathogen removal; and collecting data on fecal sludge management practices in the Trichy and Coimbatore study areas of Tamil Nadu, India. A key component of the process was presentation and consultation meetings with local government authorities on FSM practices in Trichy City Corporation and Coimbatore.

Water Institute is among the first research groups, to date, to apply the pathogen hazards concept in the estimation of safely managed human waste along the sanitation service chain. As part of this project, we have:

  • Developed and piloted approaches in Trichy and Coimbatore, India to estimate the fraction of human excreta unsafely returned to the environment by key excreta return pathways along the sanitation chain, as well as ‘pathogen hazard distribution’ at the community level.
  • Conducted a review of peer-reviewed and grey literature to examine the unsafe return of human waste from pit latrines, septic tanks, and sewerage across the sanitation delivery chain.
  • Developed prototype ‘national level’ hazard flow models for four case studies.
  • Used our research to identify design features of containment systems and other factors that influence the pathogen hazards reduction in the sanitation technologies, assisting policy-makers in decision-making about sanitation technologies.

Currently, this research is also being used for quantifying fecal pathogen being released to the community environment by key excreta return pathways along the sanitation chain. Our work has unveiled the pathogen hazards associated with the sanitation technologies in Tamil Nadu. We will continue developing tools that practitioners and policy makers need to guide the management of human excreta — at scale — in individual and small-community settings throughout the world.

We believe a fully validated “Community Fecal Hazard Flow Model” will provide a framework for identifying where, in the sanitation management chain, the public health risks are greatest and how scarce investment dollars can most effectively be programmed to reduce disease and environmental contamination. Our research has already been used to improve the design of containment systems to drastically reduce the pathogenic load of human wastes.

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