On-site sanitation system emptying practices and influential factors in Asian low- and middle-income countries: A systematic review

Different fecal sludge (FS) emptying practices have been documented worldwide, but little is known about how the type of on-site sanitation system (OSS) and other factors associated with emptying and transport influence how OSSs are emptied, nor about how FS is released to the environment during emptying. This systematic literature review assessed our current knowledge on OSS fecal sludge management practices and their impacts on pathogen releases into the environment including (i) the prevalence and frequency of emptying, (ii) the types of OSS emptying practices, (iii) other factors influencing these practices, and (iv) the return pathways into the environment during emptying and transport. The analysis included 58 peer-reviewed studies examining emptying in low- and middle-income countries in Asia published between 2001 and May 2021. Mechanical emptying was the most discussed emptying method (n=39), followed by manual emptying (n=22). The most discussed emptying factor was cost (n=19), followed by OSS accessibility (n=17). Discussion on FS releases was focused on deliberate disposal into the environment, with little on unintentional spills and leaks. Remaining gaps in the literature include the quantity, pathogenicity, and fate of FS spills during emptying, the effect of OSS type on emptying, and the effectiveness of emptying interventions. More research is needed on emptying to fully understand its impact on public health and how best to facilitate safe fecal sludge management.