Inactivation of Pathogens in Feces by Desiccation and Urea Treatment for Application in Urine-Diverting Dry Toilets

Abstract

ABSTRACT Ecological sanitation technologies can be effective in providing health and environmental pollution control if they can efficiently reduce the pathogenicity of microorganisms carried in fecal material to safe levels. This study evaluated the sanitizing effects of different additives for dry treatment of feces from urine-diverting dry toilets, based on inactivation of Enterococcus faecalis , Salmonella enterica serovar Typhimurium, bacteriophages MS2 and ΦX, and Ascaris suum . The additives, ash (A) and oyster shell (O) in different amounts and urea (U) to optimize the process, were compared with no additive, solely urea, and sawdust as controls (C) and were covered ([ x %O:A]) or uncovered ( x %O:A). The main inactivation factors found were desiccation, ammonia content, and pH. S. Typhimurium and E. faecalis were more affected by the ammonia content. A combination of neutral to high pH and desiccation was most effective for inactivation of MS2, and desiccation was most effective for inactivation of ΦX and A. suum . The inactivation rate was modeled for all combinations studied. The most promising treatments were [150%O:A+U], 150%O:A+U, and 150%O:A. According to the models, these could inactivate, for example, 7 log 10 units of all bacteria and bacteriophages within 83, 125, and 183 days, respectively. The inactivation of A. suum was modeled, albeit the measured decay in egg viability was low.