Keywords
hygienization
microbial inactivation
kinetics
agricultural reuse
sanitation safety
How to Cite
Abstract
Fecal sludge hygienization is essential for safe agricultural reuse, particularly within geographic regions where decentralized on-site sanitation infrastructure predominates. While solar drying and subsequent prolonged storage are extensively utilized as economically viable stabilization strategies, quantitative data describing microbial inactivation during drying and storage remain limited. This investigation systematically evaluated the temporal evolution and inactivation kinetics of pivotal microbiological parameters during the hygienization of desiccated fecal sludge over a longitudinal period extending up to twelve months. The study evaluated Escherichia coli, total coliforms, and intestinal enterococci, alongside the qualitative monitoring of Salmonella spp. and the assessment of helminth egg viability as a primary determinant of sanitary safety. Quantitative bacterial surrogates were characterized using first-order decay kinetic models, whereas pathogenic indicators were analyzed through a temporal occurrence framework to determine environmental persistence. The results demonstrate that Escherichia coli exhibited an inactivation rate constant of 0.42 month-1 (R2 = 0.78), necessitating approximately 5.5 and 11.0 months to achieve 90% and 99% reductions, respectively. Total coliform bacteria demonstrated significantly higher environmental resilience, characterized by a lower inactivation rate constant of 0.31 month-1 (R2 = 0.70), indicating a more protracted decay trajectory. While Salmonella spp. were successfully attenuated beyond detection thresholds following extended hygienization, the continued presence of viable helminth eggs corroborates their role as the most conservative sanitary indicator. These findings establish a rigorous scientific basis for the implementation of time-based hygienization criteria, thereby enhancing regulatory guidelines for the sustainable and safe reuse of fecal sludge in the circular economy.
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