PRISMA 2009 checklist.

<div><p>Treatment of human excreta in humanitarian camps remains rare, leading to environmental and public health risks. Fecal sludge treatment (FST) can help reduce these risks. Our objective was to summarize barriers (hindering implementation) and facilitators (enabling implementation) to FST in humanitarian camps to inform guidance. We completed a systematic review of eight databases and 39 websites in 2020, with an update in April 2023. Documents were included if they assessed FST implementation, in a humanitarian camp setting, with primary data collection of at least output level indicators. Overall, 53 documents, including 75 FST interventions from 12 countries were included. We identified 424 barriers and 435 facilitators in 11 categories: performance (239), operation (146), technical (109), economic (78), environmental (59), spatial (55), social/cultural (47), temporal (44), safety (34), supply (29), and institutional (19). The most common facilitators of FST implementation were: high reduction efficiencies; rapid implementation with available technologies; low capital and operational costs; ease of operation and maintenance; and, achieving effluent discharge standards, effluent reuse, and safe discharge. The most common barriers included under- or over-designed systems with inappropriate materials, needing strong operational supervision and additional treatment, with effluents not meeting discharge standards. Future guidance should focus on recommendations to enable facilitators and hinder barriers. Limitations included that most of the research was from one country (Bangladesh), and in stable contexts. Strengths of this work include a holistic, broad, example-based summary of actual FST implementations in camps in humanitarian settings. This review can be used to develop guidance and checklists for implementing FST in humanitarian camps, and future research needed.</p></div>