Physicochemical and microbiological characterization of human feces and urine from composting toilets in Abidjan, Côte d'Ivoire.

We assessed the physicochemical and microbiological properties of composting toilets products in Abidjan, (Côte d'Ivoire) for their potential use in agriculture. Samples of urine and feces were collected and analysed after 123 days of storage in plastic cans (urine) and 8 months of storage in closed composting bags (feces). Selected physicochemical parameters (ammonium, phosphorus, potassium, calcium, magnesium, cadmium, copper, lead and zinc) 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 feces-based compost and urine, respectively. The physicochemical analysis revealed high nutrient contents and low trace metal levels in the feces-based compost. Concentrations of magnesium, cadmium, copper, lead and zinc ranged from 0.46 to 54.98 mg/kg; whilst 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. Whereas ammonium concentration was 2012 mg/kg in feces-based compost and 57 mg/L in urine. Various bacteria including total coliforms, fecal coliforms, fecal streptococci, and anaerobic sulfite-reducers (ASR), along with Ascaris lombricoïds (1.66 eggs/g) were found in the feces-based compost. In the urine the analysis showed 20 Forming Colonies Unit (UFC) of fecal streptococci in 100 mL and 33 UFC of ASR in 50 mL. Our findings indicate that the feces-based compost was not homogeneous, namely with regards to the microbiological parameters, and an additional time would be necessary to bring it to stability.