Solar drying of faecal sludge from pit latrines in a bench-scale device

Solar thermal energy for drying proposes could be employed as a cost-effective solution for faecal sludge treatment. In despite of its great potential, this option has not been enough applied, and there is a lack of knowledge in literature to allow for its emergence. The present work aims at providing data and knowledge to the sanitation practitioners in solar drying, through an experimental work with a custom-designed bench-scale apparatus. Depending on the experimental conditions, the moisture content of the sludge could be reduced from 60% to 20% after 5 hours of solar drying, with an average drying rate varying between 0.5 to 0.8 kg/h/m2. The most favourable conditions for drying were during sunny weather conditions and for lower thickness of sample. A crust formation was observed to occur at the top of the sludge and may explain the lower drying rates than expected under certain conditions.