Faecal sludge containment characteristics and their implications on safe desludging in unplanned settlements of Dar es Salaam, Tanzania

In unplanned urban settlements, where onsite sanitation systems are the norm, desludging of faecal sludge (FS) containments is a necessity because of the lack of land space to enable new construction. Poorly designed toilet facilities however may jeopardize the progress towards attainment of safely managed sanitation. This study examined FS characteristics and containment design and their effect on safe desludging with a case of two selected unplanned settlements of Dar es Salaam, Tanzania. The analysis focused on design features for the strength of the containment, access to the containment, and desludging characteristics of the FS. The Desludgeability potential of FS was determined on basis of flow behaviour explained in terms of moisture content and volatile solids. Research results showed that partially lined pits, lack of containment access holes and solid wastes are design and usage features which negatively affect containment strength and potential for safe desludging. The analysis further found that, only 54.8% of containments studied have FS that can be desludged by either mechanized or hand pumps. Pour flush toilets and septic tanks indicated a slightly higher potential for safe desludging compared to traditional pit latrines, however, the difference is not statistically significant (P = 0.180). Thus, safe desludging is a problem across all types of containments. To enhance safe desludging in Dar es Salaam, three key design features and usage ought to be urgently addressed: first, a requirement to ensure that all pits are fully lined inside, second, the mandatory presence of an access hole for FS desludging and third, limitations on solid waste entering the pits.