Moringa Seeds and “Sticky Killer Sand” Work Together to Clean Water
By Krista Weidner
Lack of access to clean drinking water is a serious health problem in many developing countries, and often, even when methods for removing disease-causing microbes and sediment from drinking water are available, they are too expensive to be practical.
One traditional method for cleaning water in equatorial regions involves using seeds from the Moringa oleifera tree as a natural antimicrobial: When crushed seeds from the Moringa tree are added to water, they remove microbes and make the water safe for drinking. While this is an easy and accessible technique, it’s not ideal because the water can become tainted again while in storage.
The Moringa seed cleans water by releasing a positively charged protein that dissolves in the water and removes pathogens. “The problem is the seed also contains oil and other organic matter that microorganisms in the water can use as food,” explains Stephanie Butler Velegol, instructor in civil and environmental engineering. “So after it’s been stored, water treated with Moringa seed is no longer safe to drink.”
Several years ago, Velegol and her colleagues found that when they add sand, which has a negative charge, to water, the positively charged Moringa protein binds to the sand. When the Moringa protein and the sand bind together, the surface charge of the sand reverses to positive. Bacteria and sediment then stick to this "f sand" (which stands for functionalized sand). "When we rinse the f sand, we are left with 'sticky killer sand' that we can use over and over again as a filter," Velegol says.
Now Velegol and her research group are taking their findings a step further, after receiving the Material Research Institute’s inaugural Humanitarian Materials Initiative Award. Created last fall, the award is part of an initiative to support ongoing research aimed at providing long-term and sustainable solutions to problems in under-resourced regions of the world.
The team of scientists is using the $15,000 prize to fund four students, undergraduate and graduate, to do research toward improving the Moringa-coated sand filter.
One student’s work in the lab resulted in making the sand/water/Moringa mixture more efficiently—reducing mix time from more than two hours to just ten minutes. “Our process for creating the sand filter involved mixing for two and a half hours, but that’s way too long for someone doing this on the ground,” Velegol says. “Knowing that we can reduce mix time to just ten minutes, and get the same result, is one important step toward making this technique much more practical.”
She also discovered a simple field test for the reliability of the sand filter: the “stick test.” When a Moringa mixture is put into a plastic water bottle and the bottle is turned sideways and rotated, if the sand sticks to the side of the bottle that means the filter is working. “The sand sticks because the plastic has a positive charge,” Velegol explains. “On the ground, the stick test is a quick way to confirm that a particular filter works. And in the lab, we confirmed that every time the sand has a positive charge, the stick test works.” Although the stick test shows promise, Velegol emphasizes that more research is needed to ensure that lab results continue to match field results.
Two students are working this summer on creating a mathematical model to predict the filter efficiency and longevity. This will allow the filter to be reproduced under different conditions (e.g. sand type and size, quality of water) around the world.
The research team also used award funding to travel to Rwanda this past spring to extend their Moringa research focus beyond drinking water. They are collaborating with Pivot Works (http://pivotworks.co), a company working in Rwanda that turns fecal sludge into fuel. This sustainable process currently uses a cationic polymer to flocculate the sludge. The team worked with Chief Technology Officer Andrew Maguire to explore the possibility of replacing the polymer with local Moringa seeds to create the fuel much less expensively.
In searching for local growers of Moringa trees, Maguire discovered Asili Natural Oils (http://asilioils.com/), a company that grows the trees and sells the seed oil to personal care companies. “Of course, this company didn’t want to compete with Pivot Works for Moringa seeds,” Velegol says. “But we realized that when you squeeze the seeds to get the oil out, you end up with a byproduct—a seed cake—which is what contains the Moringa protein we need. It was great news that Pivot Works only needs the seed cake for their process. So if Pivot Works can buy the byproduct from Asili Natural Oils, it’s a win all around. The students were so excited about this project and where it led us during our time in Rwanda.”
Velegol is optimistic about the future of research on the Moringa seed. “We are linking hardcore science with humanitarian work,” she says, “working on strengthening that link between lab research and people on the ground. So many of our undergraduate students have a passion for humanitarian work, and we need to get the message across that engineering helps make the world a better place. Our students want to make a difference—let’s show them how they can do that using good science.”
Stephanie Velegol’s research colleagues include Manish Kumar, assistant professor of chemical engineering, Michael Erdman, director of Engineering Leadership Development in the College of Engineering, and Bashir Yusuf of Ahmadu Bello University, Nigeria. The Humanitarian Materials Initiative awards are sponsored by Covestro LLC (formerly Bayer MaterialScience LLC) and the Materials Research Institute.
Contact Dr. Velegol at email@example.com.