A systematic review of water treatment with Moringa oleifera seeds: Comparative analysis of jar testing methodologies and results

This systematic review aims to assess the reliability of contemporary research on water treatment with Moringa oleifera seeds. Academic databases were browsed on a yearly basis (2014 – 2024); identification and screening were conducted between July 17th 2023 and December 9th 2024. Primary research reports featuring jar testing with M. oleifera seed coagulant were included for data collection. Thirty-five fields were used to collect data. Data was synthesised by establishing causality between independent variables and outcomes. Conflict of interest, research quality and risk of bias were assessed using modified Cochrane tools. Fifty non-duplicate publications were identified. Of these, 25 were included for data collection. In total, 511 data points were collected and synthesised. No conflicts of interest were found. Sixteen reports received “lower” or “lowest” research quality judgements. Six reports received “high risk of bias” judgements. Bias risk was most commonly associated with experimental design and missing data. Inadequate standardisation in test water preparation, M. oleifera seed coagulant processing and jar test parameters affected treatment efficacies in unpredictable ways. Researchers who used M. oleifera seed coagulants at appropriate concentrations and adhered to the three-stage model of coagulation, flocculation and sedimentation achieved turbidity reduction rates of 80–96%. Turbidity and microbiological reduction rates were comparable in three reports, but microbiological testing was uncommon. Based on their properties, M. oleifera cationic proteins are theorised to be lectins with hevein-like binding domains. These findings are significant because this technology has been in development for at least forty years and remains experimental due to perceived unreliability, unclear safety limits and limited innovation. Suggestions for future research and standardisation are made throughout this review. If the technology is found to be a safe, effective and sustainable method of water purification, it may support Targets 6.1, 6.a and 6.b of the United Nations sustainable development goals.