Physicochemical and microbiological characterization of human faeces and urine from composting toilets in Abidjan,...

We assessed the physicochemical and microbiological properties of composting toilet products in Abidjan for their potential use in agriculture. Samples of urine and faeces were collected and analysed after 123 days of storage in plastic cans (urine) and 8 months of storage in closed composting bags (faeces). Selected physicochemical parameters (ammonium, phosphorus, potassium, calcium, magnesium) and pathogens (bacteria and helminths eggs) were monitored. Results showed that temperature and pH values were 26.0°C and 7.2, and 27.6°C and 8.6 for the faeces and urine, respectively. The physicochemical analysis revealed high nutrient contents and low trace metal levels in the faeces-based compost. Concentrations of magnesium, cadmium, copper, lead and zinc ranged from 0.46 to 54.98 mg/kg; while those of phosphorus, potassium and calcium were >700 mg/kg on average. In urine, the concentrations of phosphorus, potassium, calcium, copper and zinc were 930, 1240, 1402.8, 0.0672 and 0.121 mg/L, respectively. Various bacteria (including total coliforms, faecal coliforms, faecal streptococci and anaerobic sulphite reducers), along with Ascaris lombricoïds (1.66 eggs/g), were found in the faeces-based compost. Our findings indicate that the faeces-based compost was not homogeneous, namely with regard to the microbiological parameters, and additional time would be necessary to bring it to stability.