Discussion
septic
In our substudy nested within a randomized controlled trial that provided sanitation hardware along with initial intensive behavior change promotion, the intervention led to a sustained increase in access to a hygienic latrine with a functioning water seal, feces well-contained in a septic tank or pit, and no feces on the slab or floor of the latrine 1–3.5 years after intervention initiation. Access remained high during periods with less intensive or no promotion. The gains in hygienic latrine access were more pronounced among households with less education, less wealth and larger number of residents and children. While the intervention significantly increased reported exclusive latrine use by adults and children 3–8 years old, reported exclusive latrine use by adults was high (77%) among controls, indicating existing sanitation norms and habits. The intervention increased availability of child feces management tools but their use remained low among intervention recipients, and any gains in potty use in the intervention arm declined over time.The parent WASH Benefits study was an efficacy trial where latrine upgrades were provided to households free of charge and accompanied by initial intensive behavior change promotion. As such, the increase in hygienic latrine access among intervention recipients was substantially higher than what has typically been achieved by programmatic sanitation improvements. A systematic review on sustained adoption of sanitation interventions (defined as latrine ownership, presence, quality, functionality or use after the end of the intervention period) found that the most influential program factors associated with sustainability included frequent, personal contact with a health promoter and accountability over a period of time (Households in the sanitation arm also emptied the latrine pit less frequently, which may have been due to the recent construction of the pit latrine by the study, the dual-pit design which requires less frequent desludging, and slower pit fill-up due to reduced latrine sharing. Our findings are consistent with studies in Mozambique which found less frequent emptying of septic tanks at intervention compounds which received sanitation upgrades, including construction of sanitation infrastructure or subsidized provision of pour-flush toilets draining to a septic tank (Interventions substantially increased availability of child potties while the majority of households in both groups had a scoop or similar tool that can be used for removal of child feces. However, the use of these child feces management tools was low and inconsistent among intervention recipients. Similarly, in a recent trial in India that promoted safe child feces management along with broader latrine use, the intervention increased the percentage of households where the caregiver safely disposed of child feces by approximately 20 percentage points but only a third of intervention recipients practiced safe disposal (In rural Bangladesh, potties are uncommon and not widely available for purchase (Our previous work in rural Bangladesh suggested that unsafe child feces disposal is associated with increased Our study had some limitations. While the observable uptake indicators objectively reflected the availability and condition of infrastructure and supplies they may not accurately represent actual use as availability does not ensure use. However, our observed indicators included visual signs of likely recent use, such as the tools being wet or free of dust. Additionally, our study had a longitudinal design where we visited the same households several times. Therefore, it is possible that anticipation of a data collection visit might alert participants to improve their practices during the data collection period and, therefore, overestimate uptake (