Pit latrine flooding: Modelling the effect of management practices and structural integrity on washout

This study addresses a critical gap in sanitation and public health research by providing the first numerical assessment of flood-induced pit latrine washout volumes. These latrines are a common sanitation solution in low- and middle-income countries, but their potential to serve as sources of faecal contamination during flood events has remained a subject of debate due to a lack of empirical data. Employing a single-phase Computational Fluid Dynamics (CFD) model, this paper assesses the volume of human waste being washed out from latrines under various conditions, including initial supernatant and sludge volumes and latrine structural integrity. Simulation results suggest a phased release of faecal contaminants, with peak discharge occurring during the initial inundation and recessional phases. These distinct pathways warrant further quantification to determine their contribution to the total pollution load. The results also point to specific preventative measures, such as pre-flood emptying and timely structural repairs for latrines, to mitigate the contamination risks in flood-prone areas.