Nitrogen transformation during the aerobic biodegradation of feces

Abstract

We have been proposing an onsite differentiable wastewater treatment system. In the system, black water is treated by non-flushing composting toilet by using sawdust as matrix, and nutrient in feces and urine is recovered as compost. Previous study showed that most of nitrogen volatized as NH₃ gas during composting process. Since most nitrogen is in urine, separating feces by urine diverting toilet bowl and supplying only feces to the composting toilet contribute to improving nitrogen recovery. In this study, we conducted composting experiments using feces and sawdust and observed the fate of nitrogen during composting process. The experimental results showed that 1) the time lag was observed between the peek time of CO₂ production rate (CO₂PR) and the peek time of ammonium nitrogen volatilization rate (ANVR); 2) composting only feces gave the high nitrogen recovery, i. e. approximately 10% to 20% of nitrogen in supplied feces volatized as an ammonia gas from the system.