Effect of transparent covers for collection chambers of urine-diverting dry toilets on dehydration of faecal waste

Urine-diverting dry toilets save water, reduce the demand for wastewater treatment and provide plant nutrients. The conditions in the collection chambers and the interlinked hygienic safety of subsequent faecal matter use in crop production are affected by the building design. Comparative experiments were carried out to evaluate the potential of transparent chamber covers in comparison with non-transparent chamber covers to increase temperature and ventilation in order to enhance faecal matter dehydration and sanitation. The air temperature in the chambers with transparent covers (TC) was 1.1–1.5 °C higher and the relative air humidity about 5–7% lower than in chambers with non-transparent covers. The advantage of TCs on temperature and humidity prevailed throughout the year, but was most pronounced in months with more sunshine hours and higher irradiation. Furthermore, the airflow out of the chambers through the ventilation pipes was increased by 60% in the TCs. During two-month collection and dehydration cycles the improved drying conditions in the TCs resulted in 7% lower faecal matter moisture. A trend towards an enhanced pathogen inactivation in the faecal material was observed. The results demonstrate that in the semi-arid tropics transparent covers for collection chamber of urine diverting dry toilets improve the dehydration of faecal matter.