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

Abstract

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.

Resource recovery technologies as microbial risk barriers: towards safe use of excreta in agriculture based on hazard analysis and critical control point

“…The inactivation rate of pathogens is influenced by physicochemical factors of matrices. 17 Therefore, CLs of storage time and environmental factors were determined using regression tree which allowed to categorize the required storage time according to the environmental condition of storage. This review provides with the potential CCPs in a non-sewer sanitation system, what to be monitored at CCPs, and the concept of determining CLs which needs to be achieved at CCPs.…”

“…14–16 However, individual technologies are yet to be characterized for implementing the HACCP approach in SSP. To fully implement HACCP-based management in SSP, the following procedures are needed for technological barriers in advance: 8,17 1) identification of CCPs in a sanitation system, 2) selection of monitoring parameters that affect pathogen inactivation, 3) development of a pathogen inactivation kinetics model, and 4) determination of the CLs for sufficient inactivation of pathogens.…”

Estimation of alkali dosage and contact time for treating human excreta containing viruses as an emergency response: a systematic review

“…One promising approach is using an inactivation kinetics model that represents the log-reduction values (LRVs) of microorganisms as a function of variables related to the matrix and environmental conditions (20). Machine learning algorithms are advantageous for predicting LRVs because they can avoid overfitting training datasets using dimensional reduction, regularisation, and cross-validation (21).…”

Experimental Adaptation of Murine Norovirus to Calcium Hydroxide

“…In a non-sewered sanitation system, human excreta is stored in a pit or container at least 1 year to make the material safe to handle ( WHO, 2015 ; Oishi et al, 2021 ). Without this long-term storage, farm workers and sanitation workers can be directly exposed to viruses by oral transmission during collection, irrigation, and application of the excreta to farmland ( Julian et al, 2018 ; Bischel et al, 2019 ).…”