Fry drying of faecal sludge (South Africa)

This study examined the drying kinetics of pit latrine faecal sludge by oil immersion at various frying temperatures and analyzed the final treated sludge in the parameters of moisture content, water activity, total and volatile solids. The drying experiments were conducted at oil temperatures of 150 °C, 170 °C and 190 °C. The drying curves obtained indicated a common dehydration period of under 4 minutes considering both thickness variations of 10 mm and 14 mm. The drying kinetics were greatly influenced by high oil temperatures, the water hydrophobic effect against hot oil, and the duration of deep frying the faecal sludge. The effect of sample thickness appeared negligible in the study range.

Water activity showed great dependence on the moisture content of the final treated samples as a reduction was noted. The dehydration of the sludge also showed an increased quantity of total solids as well as volatile solids.