This common plant could clean microplastics from your drinking water

The findings were published in ACS Omega, a journal of the American Chemical Society.

Moringa is native to India and grows well in many tropical regions. Its leaves and seeds are widely consumed as food due to their nutritional value. Scientists have also been exploring the seeds for years because of their potential role in water purification.

Moringa Seed Extract Performs Like Chemical Treatment

"We showed that the saline extract from the seeds performs similarly to aluminum sulfate, which is used in treatment plants to coagulate water containing microplastics. In more alkaline waters, it performed even better than the chemical product," says Gabrielle Batista, the first author of the study. She carried out the research during her master's degree in the Post-Graduate Program in Civil and Environmental Engineering (PPGECA) at the Bauru School of Engineering (FEB) at UNESP.

The study was led by Adriano Gonçalves dos Reis, a professor at ICT-UNESP and in the PPGECA at FEB-UNESP. He also heads the project "Direct and In-Line Filtration for the Removal of Microplastics from Drinking Water," which is funded by FAPESP.

"The only drawback found so far regarding aluminum sulfate was the increase in dissolved organic matter, the removal of which could make the process more expensive. However, on a small scale, such as on rural properties and in small communities, the method could be used cost-effectively and efficiently," says Reis.

How Coagulation Helps Remove Microplastics

The research focused on in-line filtration, a method in which water is first treated with a coagulant and then passed through a sand filter. This approach works best for water with low turbidity, meaning it is relatively clear and requires fewer preliminary treatment steps.

Coagulation plays a key role because microplastics and other contaminants carry a negative electrical charge. This causes them to repel each other and prevents them from being captured easily during filtration. Coagulants, including moringa salt extract (which can be made at home) and aluminum sulfate, neutralize these charges. As a result, the particles stick together, forming larger clusters that can be removed more easily.

Earlier work by the same research group showed that moringa seeds are effective throughout a full treatment cycle, including flocculation, sedimentation, and filtration. Luiz Gustavo Rodrigues Godoy, the first author of the study, completed his master's degree at FEB-UNESP with support from FAPESP.

Lab Tests With Microplastic Contaminated Water

To evaluate the method, the team added polyvinyl chloride (PVC) microplastics to tap water.

PVC was chosen because it is considered one of the most harmful plastics for human health, with known mutagenic and carcinogenic properties. It is also commonly found on the surfaces of water bodies and can persist even after conventional treatment.

The researchers exposed the PVC to ultraviolet radiation to simulate natural aging and better reflect the characteristics of real-world microplastics.

The contaminated water then went through coagulation and filtration using a Jar Test system, which mimics water treatment processes on a small scale. The results were compared with samples treated using aluminum sulfate.

To measure effectiveness, the team used scanning electron microscopy (SEM) to count microplastic particles before and after treatment. They also analyzed the size of the particle clusters formed using a high-speed camera and laser measurements. Both treatments showed similar levels of microplastic removal.

Testing Moringa in Real Water Sources

The researchers are now testing moringa seed extract on water collected from the Paraíba do Sul River, which supplies São José dos Campos. So far, the results suggest the method is effective in treating natural water conditions as well.

"There's increasing regulatory scrutiny and health concerns regarding the use of aluminum- and iron-based coagulants, as they aren't biodegradable, leave residual toxicity, and pose a risk of disease. For that reason, the search for sustainable alternatives has intensified," Reis concludes.

The findings highlight moringa as a promising, more sustainable option for reducing microplastics in drinking water, especially in smaller communities where cost and accessibility are key concerns.