Abstract
Composting toilet using sawdust as artificial soil matrix is an essential process in the onsite wastewater differentiable treatment system. It reduces volume of feces and urine by evaporating of water in feces and urine. And it can also attribute to nutrient recovery from human manure due to giving used sawdust that can be used as organic fertilizer rich in N, P and K. The aims of this paper are 1) to measure nitrogen balance in composting toilet and 2) to evaluate the effect of water evaporation on ammonia volatilization due to its high solubility into water. The nitrogen balance data obtained from the composting toilet operation showed that approximately 25% of nitrogen remained in the sawdust matrix and ammonia emission was always detected. The evaporation of water and ammonia volatilization occurred simultaneously from the composting toilet. In order to evaluate the effect of water evaporation onammonia volatilization, the time course of pH and ammonia concentration in sawdust matrix were observed during ammonia volatilization process with and without evaporation of water. In the experiments, the rate of ammonia volatilization was greater than the rate of water evaporation in the first period and then the rate of ammonia volatilization decreased and become lower than water evaporation. This change in ammonia volatilization was caused mainly by pH value of water in the sawdust Especially, at low water content the sawdust pH kept less than pH 6 even if ammonia concentration was high.
