Sustainable management of faecal sludge requires reasonable estimates of the quantities and qualities (Q&Q) that are accumulating at community to city-wide scale. In situ Q&Qs of faecal sludge are difficult to estimate, as faecal sludge is often stored underground in containments, records frequently do not exist, and construction is not standardized, but estimates are necessary for planning scenarios as it represents the total amount and characteristics of faecal sludge that needs to be managed. For more on measuring in situ volumes of faecal sludge, refer to the Volaser. In the past, people have estimated Q&Qs based on literature values from other contexts, or educated guesses from users and emptying service providers, but these estimates were not adequate to capture the desired accuracy and range of variability.
To address this deficiency, a methodology was developed by Eawag/Sandec, using forms of demographic (e.g. income level, number of users), environmental (e.g. soil conditions, groundwater), and technical (e.g. containment type, inputs to containment) forms of data to group together accumulated Q&Qs of faecal sludge to make localized projections. Demographic, environmental, and technical (DET) forms of data are also spatially analyzable, which is important for city-wide planning. This methodology has evolved during implementations in seven cities, and is now fully described in a book chapter in the IWA publication ‘Methods of Faecal Sludge Analysis’, which can be found here. Further developments we are working on to improve the methodology include remote sensing, and different types of machine learning and predictive modeling
Publications are listed below, steps in methodology development include:
- Q&Q studies in Kampala, Uganda, and Hanoi, Vietnam, where the first sampling plans were tested during conceptualization of the methodology.
- Two Master theses in Dar es Salaam, Tanzania, which looked at Q&Q on a neighborhood scale. The first conceptualization tests for the Volaser were also done here.
- Determining Q&Q of faecal sludge in Sircilla, a small town in India, where different methods for measuring faecal sludge accumulation rate were tested and compared.
- Collaboration with the Systems Analysis & Modeling department at Eawag to analyze spatial patterns in Q&Q data, and to explore whether models could be made from existing data that can be used in the future for making predictions with increased accuracy at a lower cost.
- Large scale Q&Q study in Lusaka, Zambia, where the objective was to make estimates of accumulating faecal sludge Q&Qs in Lusaka. 400+ samples were taken in situ from onsite sanitation technologies all over the city.
- Sharing of raw data for 845 samples taken in four cities (180 Kampala, Uganda, 80 Hanoi, Vietnam, 164 Sircilla, India, 421 Lusaka, Zambia)