Assessing ambient and internal environmental conditions of pit latrines in urban slums of Kampala, Uganda: effect on performance

There is increasing interest to improve the functionality and performance of pit latrines in low income urban areas. This study aimed at assessing the ambient and pit environmental conditions and their implications on the performance (smell and fly nuisance) of pit latrines. Forty-two pit latrines were investigated in urban slums of Kampala, Uganda, through field observation and measurements of ambient and pit environmental conditions. The implications were assessed using oxygen-reduction potential (ORP) and its association with smell/insect nuisances. The pit temperature (21 to 30.7 °C), pH (5.0–11.8) and ORP (−247 to 65.9 mV) were consistently, significantly different (p < 0.001) between the surface and 0.5 m depth of pit content. The conditions in most (95%) pit latrines were anoxic (ORP < +50 mV), and mainly within the acid formation range (ORP −199 to −51 mV). Most smelling pit latrines and flies were within the acid formation ORP range, with a significant association (gamma, G = 0.797, p = 0.014) between ORP and smell in clean latrines only. The results suggest that ventilation of pit latrines within urban slums was not sufficient. Additionally, cleanliness, moisture reduction and waste stabilisation could address bad smells in pit latrines, ultimately improving their usage in urban slums.