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 but can pose health and environmental hazards if not properly managed. 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.