On the banks of Nagdaha, a polluted and lotus-infested lake in Nepal, Soni Pradhanang is putting trash back into the water—on purpose.
She carefully assembles a platform of styrofoam and bamboo mats, then weaves it together with zip ties and coconut fiber, refuse from nearby tech stores. Then, she pokes 55 plants lush with red flowers through 2-inch holes in the platform, each plant set 6 inches apart. Though Pradhanang’s creation isn’t high-tech, it is effective, and one of the most affordable water-filtration systems available. “I’m cheap,” she says, laughing.
Pradhanang, a hydrologist at the University of Rhode Island who studies water-quality monitoring and modeling, has spent the past seven years