Behind the paper: the water-purifying promise of the Moringa tree

We speak to Joseph James Russell, Andrew W. J. Paterson and Martin Pritchard, an author team based at Leeds Beckett University, about their recent PLOS Water publication “A systematic review of water treatment with Moringa oleifera seeds: Comparative analysis of jar testing methodologies and results“.

What motivated you to explore the topic and decide on this research question?

Our motivation stemmed from a significant global challenge: many people lack reliable access to safe and affordable drinking water. In resource-constrained settings, conventional water-treatment chemicals are often expensive, difficult to source or impractical for small rural communities in developing regions. This has increased interest in natural locally available materials for improving drinking water quality.

Moringa oleifera, often called the drumstick tree or miracle tree, is especially interesting because its seeds can remove suspended particles from water. This property has been studied for several decades and has real promise. However, it has not yet become a widely trusted or standardised water-treatment process, despite a long history of research. We wanted to understand why. Our research question therefore focused on how reliable the current evidence is, and what still needs to be improved before Moringa oleifera seed treatment could potentially be safely and confidently used in practice by low-resource communities.

Could you talk us through how you designed your study?

We designed the study as a systematic review of research published between 2014 and 2024. Rather than carrying out a single laboratory experiment, we stepped back to assess the wider evidence base.

We searched academic databases and screened the literature for studies that tested Moringa oleifera seed coagulants using jar testing. Jar testing is a standard laboratory method used to assess the effectiveness of a substance in causing particles in water to aggregate, settle and improve clarity. We then collected data from the included papers using 35 fields, covering the water tested, seed preparation method, dose, mixing and settling conditions, use of control samples and reporting of results.

In total, 25 studies were included and 511 data points were extracted. We also assessed research quality, risk of bias and conflicts of interest, allowing us to compare results and judge confidence in the evidence.

Did you encounter any challenges during your study?

Yes. The biggest challenge was the lack of consistency across the published studies. Researchers used different types of water, different seed-preparation methods, different doses, and different mixing and settling parameters. Some papers were very clear and detailed, while others left out important information or did not include control samples. This made comparison difficult and may help explain why the treatment method has not progressed more rapidly.

Another challenge was the predominant focus on turbidity, which is the cloudiness of water. Whilst turbidity is important, clear water is not necessarily safe water. Few studies examined microbiological safety, which is crucial when the treatment is being considered for drinking water.

These challenges were not just technical details. They address the core question of whether a promising treatment can be trusted and transferred from the laboratory to real-world use.

What did you find most striking or surprising about your results?

What stood out most was the gap between promise and reliability. When Moringa oleifera seed coagulants were used at appropriate concentrations, and when studies followed clear mixing parameters, floc-formation and settling stages, turbidity reductions of 80–96% were reported. That is a very encouraging result.

However, we also found uneven quality within the evidence base. Sixteen of the 25 studies were judged to be of lower or lowest research quality, and six raised high risk of bias concerns. This does not mean the technology does not work. Rather, it shows the field needs more rigorous experimental design and reporting criteria.

We were also struck by the rarity of microbiological testing. It is essential to know not only whether treated water looks cleaner, but whether it is safer to drink.

How do you think this research will be used and who do you hope might benefit from these new insights?

We hope the research will be used to improve the reliability and comparability of future research. For researchers, the review identifies best practices and key reporting criteria. For engineers, scientists and water professionals, it highlights the optimal conditions for water treatment with Moringa oleifera seed coagulants. For charities, non-governmental organisations and community water projects, it provides a balanced message: this is a promising low-cost treatment, but it should not be promoted as a simple solution without proper testing, guidance and safeguards.

The people who could ultimately benefit most are communities where access to conventional water treatment is limited or unreliable. If this method can be shown to be safe, effective, locally appropriate and sustainable, it could support more affordable and community-led approaches to improving water quality. However, our review also makes clear that vulnerable communities deserve robust evidence, not just hopeful claims.

What further research questions need to be addressed in this area?

Several important questions remain:

1. Future studies need to adhere to more standardised methods for preparing Moringa oleifera seed coagulants, selecting coagulant doses, selecting jar test parameters, and reporting results. Without that consistency, it will remain difficult to compare studies or develop practical guidance.
2. More research is needed on microbiological safety. Researchers need to test whether the treatment reduces levels of harmful bacteria, viruses or parasites, and whether treated water remains safe during storage.
3. We need to understand the potential risks associated with adding organic plant materials to drinking water, including allergenicity and impacts on downstream disinfection methods, such as chlorine or solar disinfection.

There are also practical questions. How should seeds be harvested, dried, stored and prepared? How might seed variation affect performance? How long do they remain effective? What training would communities need? Could the method work alongside filtration and/or disinfection? And how acceptable would it be to the people it is intended to benefit?

Why did you choose PLOS Water as a venue for your article?

PLOS Water felt like the right home for this paper because the topic sits at the intersection of water quality, public health, sustainability and development. The paper is not only about a laboratory method; it is about whether a low-cost, plant-based approach could contribute to safer and more affordable water treatment in settings where conventional systems may not always be available.

We also value the open access model. If research is intended to support those working in lower-resource settings, it is important that the findings are accessible. Publishing in PLOS Water helps the work reach a broad international audience, including people who may not have access to subscription journals.

For us, the key message is that Moringa oleifera seed treatment has genuine promise, but promise must now be matched by stronger evidence, clearer standards and careful attention to safety.

Author biographies

Joseph James Russell is a postgraduate researcher at Leeds Beckett University whose work focuses on low-cost water treatment, microbiological water quality and the toxicological safety of plant-based coagulants.

Dr Andrew W. J. Paterson is a Senior Lecturer based in the School of Health at Leeds Beckett University and contributes expertise in toxicology, microbiology and public health.

Dr Martin Pritchard is a Reader at Leeds Beckett University with research interests in water quality, sustainable treatment technologies, water quality monitoring, and water infrastructure in low-resource settings. For the past 20 years, he has worked in developing countries on water quality issues.

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