Microbial Hazards in Surface Soils after Limed On-site Burial of Household Fecal Sludge in Rural Cambodia

Safe management of fecal sludge in on-site sanitation systems remains challenging, particularly in low-resource contexts. Fecal sludge treatment plants are often non-existent, non-functional, or non-viable in these contexts due to costly and complex operational requirements. Decentralized fecal sludge treatment methods (e.g., burial on-site) are more commonly used by the 3.4 billion people who use on-site systems. We assessed fecal indicator bacteria in surface soils immediately before, immediately after, and 30 days after a novel service called limed on-site burial (LOB), which was recently pilot-tested in rural Cambodia and improves upon existing on-site burial methods. Before-and-after analysis of surface soils at the toilet entrance and at the center and two edges of the burial locations found that Escherichia coli (E. coli) concentrations did not increase due to LOB and likely decreased immediately after (-0.23 log10, [-0.46, -0.01]) and 30 days after service (-0.76 log10, [-0.98, -0.55]). Results confirm existing recommendations of burying fecal sludge 1.0 m underground and covering with at least 0.3 m of soil to mitigate microbial hazard to humans from LOB. Standardizing and confirming the outcomes of LOB provide a pathway towards safely managed sanitation in low-resource contexts that can help challenging regions achieve Sustainable Development Goal 6.2.