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

• Published in: Applied and Environmental Microbiology 2009-02, Vol.75 (3), p.662-667
• Main Authors: Nordin, Annika, Nyberg, Karin, Vinnerås, Björn
• Format: Article
• Language: English
• Subjects: Agricultural Science; Ammonia; Ammonia - pharmacology; Animals; Anthelmintics - pharmacology; Ascaris suum; Ascaris suum - drug effects; Biological and medical sciences; Disease transmission; Environmental Sciences related to Agriculture and Land-use; Feces; Feces - parasitology; Food Science; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; Jordbruksvetenskap; Livsmedelsvetenskap; Microbiology; Miljö- och naturvårdsvetenskap; Public Health Microbiology; Sanitation - methods; Survival Analysis; Temperature; Temperature effects; Time Factors; Urea - pharmacology; Urine; Urine - parasitology; Worms
• ISSN: 0099-2240; 1098-5336; 1098-5336; 1098-6596
• DOI: 10.1128/AEM.01250-08

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 greater-than-or-equal24°C, NH₃ proved to be an efficient sanitizing agent in urine and feces at concentrations of greater-than-or-equal60 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.