Penn State engineering students and faculty recently traveled to Rwanda to explore whether or not a readily available plant seed could be used as a viable alternative to clean wastewater.
"We joined Pivot Works, a local wastewater treatment and fuel plant, and helped them study whether the moringa seed could be used as a cheaper and more sustainable clumping agent in their wastewater treatment process," said civil engineering junior Emma Clement.
Clement, along with Stephanie Butler Velegol, undergraduate program coordinator and instructor in environmental engineering, Mike Erdman, Walter L. Robb Director of Engineering Leadership Development and instructor of engineering science & mechanics and Adam Uliana, senior in chemical engineering, traveled to Kigali, the capital of Rwanda, to work with Pivot Works. The company converts human fecal waste into renewable fuel and then sells it to industrial customers like cement companies.
While Pivot Works' current process is effective, they rely on the use of an expensive imported cationic polymer to remove the water from the fecal waste and were interested in testing out alternative, more economical methods. The Penn State group was hoping to help them with this goal.
The moringa seed comes from the Moringa oleifera tree, common to tropical and subtropical regions of the world including Rwanda, and moringa seeds have been shown to effectively treat wastewater under certain conditions.
So the researchers traveled to Rwanda to test the moringa seed's capabilities at Pivot Works' treatment plant.
The first thing they needed was indigenous moringa seeds for the experiment. In order to get them, the group connected with Asili Natural Oils, a local company that harvests moringa seeds for their essential oils. Though Asili was extracting and using the moringa seed oil, they were able to provide the researchers with moringa seed cake— the dried remnants of the seeds once the oils have been extracted—for use in their experiments. This cake contains all the fundamental elements the team needed.
The researchers then used the seed cake to replace the regular cationic polymer in Pivot Works' water clarification process.
"During their process, fecal sludge from septic tanks is delivered by truck, and it goes into this cage that catches the larger waste like a filter." Velegol said.
From there, Velegol said, they pump the waste into a second tank where the cationic polymer is added. This causes the sludge to clump. Then it is sent through a dewatering machine that separates the clumps from the water.
Once the clumps are removed, they are spread out in a greenhouse until they dry enough to be sent through an industrial drying machine that turns the material into solids, which are then sold to companies to be used as fuel.
"What we were hoping is that moringa seeds could eventually be used to replace the cationic polymer in this process," Velegol said. "Unfortunately, it didn't work."
The moringa seeds did cause the sludge to clump as expected; however, the clumps were smaller than those in the traditional method and could not be removed from the water as efficiently, so the moringa seed cake did not prove to be a sufficient replacement polymer.
Though the results were undesirable, the trip was still beneficial for future moringa research.
"We're still talking about how moringa can be used," Velegol said. "It can't be used for this current process, but it could possibly still be used for another part of the process."
The students also learned a valuable lesson on how to do lab experiments in conditions vastly different than those found in the United States.
"The people had no running water like we have in the U.S., but they were still able to perform incredible experiments every day to learn more about their sustainable process," Velegol said. "It showed us how we need to adjust what we are doing so it can be applied around the world where it is needed most."
They also enjoyed some once-in-a-lifetime experiences on their trip.
"We went on a gorilla trek, a hike through the mountains into a rain forest where we saw mountain gorillas up close, which was amazing," Clement said. "I also learned a lot about the history and culture of Rwanda, and a lot about wastewater treatment and fuel production and about moringa growing, harvesting and oil extraction processes."
Clement said she also learned a lot about herself and her ability to deal with new cultures.
"It was one of the best and most worthwhile things I have ever done in my life," she said. "I learned and experienced so much, and I feel like my research skills have really grown as a result of the work we did there."
The team plans to stay in contact with researchers at Pivot Works in order to conduct future tests.