Predictive Environmental Microbiology for Safe Use of Sanitation Products in Agriculture: Challenges and Perspectives

Human excreta is a local resource of plant nutrients. The recovery of resources from human excreta and the use of excreta-derived organic fertilizer (sanitation products) for agriculture are compatible with the principle of the Circular Economy. Infectious disease risk associated with resource recovery activities is reduced by following the practices recommended in the guidelines for safe use of sanitation products. This study briefly reviews the domestic and international regulations and specifies the need for developing predictive environmental microbiology. Predictive environmental microbiology is a methodology that aims to predict the rate of inactivation of pathogens in sanitation products using mathematical models. We address the main challenges in applying modeling approaches to sanitization of human excreta matrices, specifically incorporating the heterogeneous nature of matrices and technology-specific factors into the kinetics parameters. In addition, the uncertainty in viral tolerance stems from the genetic nature of viral populations and should be considered in a model of inactivation kinetics for viral indicators. We emphasize the need for a fundamental understanding of pathogen adaptation mechanisms in developing a disinfection method for sanitation products. Disclosing a genetic/phenotypic factor underlying disinfection resistance and the consequent modification of model kinetics will lead to effective sanitization strategies against enteric viruses with varied tolerance.