Inactivation of Ascaris Eggs in Source-Separated Urine and Feces by Ammonia at Ambient Temperatures

ABSTRACT Sustainable management of toilet waste must prevent disease transmission but allow reuse of plant nutrients. Inactivation of uterus-derived Ascaris suum eggs was studied in relation to ammonia in source-separated urine without additives and in human feces to which urea had been added, in order to evaluate ammonia-based sanitation for production of safe fertilizers from human excreta. Urine was used concentrated or diluted 1:1 and 1:3 with tap water at 4, 14, 24, and 34°C. Fecal material, with and without ash, was treated with 1% or 2% (wt/wt) urea at 24 and 34°C. At 34°C eggs were inactivated in less than 10 days in urine and in amended feces. At 24°C only feces with 2% (wt/wt) urea or 1% (wt/wt) urea at high pH (10) inactivated all eggs within 1 month, and no inactivation was observed after 75 days in urine diluted 1:3 (18 ± 11 mM NH3). At temperatures of ≥24°C, NH3 proved to be an efficient sanitizing agent in urine and feces at concentrations of ≥60 mM. Treating fecal material at 34°C can give a 6-log10 egg inactivation within 1 month, whereas at 24°C 6 months of treatment is necessary for the same level of egg inactivation. At temperatures of 14°C and below, inactivation rates were low, with viable eggs after 6 months even in concentrated urine.