Assessing the sustainability of biosand filters: Unveiling interlinkages and leveraging factors for effective implementation

The household slow sand filter patented biosand filter (BSF) has been implemented in several developing countries to improve access to safe water. Evaluating the sustainability of various BSF implementations is essential. However, most evaluations neglect interlinkages among factors. This leads to unclear identification of leverage points to enhance BSF sustainability, resulting in limited utility to policymakers. To address this issue, the present study carried out a systematic literature review and used systems thinking to establish complex interlinkages among some factors affecting BSF sustainability. A total of 38 studies in 21 countries from the Americas, Africa, and Asia evaluated the BSF and 31 factors were found across the studies. The most influential factors were continued use, produced water quality, operations and maintenance (OM), and willingness to pay. Continued use was positively correlated to produced water quality and negatively related to the amount of water produced. OM was positively correlated with household hygiene practices and negatively correlated with education level. Willingness to pay was positively related to household income and education level. BSF's discontinued use was attributed to broken parts and improper maintenance. This paper identified the main leverage points that should be targeted during BSF implementation to improve its sustainability. This study helps identify specific factors and enables policymakers to understand their interrelationships, facilitating well-informed decisions before implementing a BSF.