Imagine Magazine - Johns Hopkins - May/June 2015 - (Page 8)

A SolAR-PoweReD Solution to the wAteR CRiSiS by Deepika Kurup Over 70 percent Of Our blue planet is cOvered in water, sO it seems that water is everywhere. we use water fOr drinking, cOOking, cleaning, and even recreatiOn, and tO many Of us the wOrld's supply Of clean water seems endless. in reality, it is anything but. tOday there are 750 milliOn peOple in the wOrld whO lack access tO clean, safe water. we are facing a glObal water crisis. I saw this crisis for myself when visiting relatives in India. I saw people standing in long lines under the hot sun to fill buckets with tap water. I saw children filling plastic bottles with polluted water from nearby streams, and I watched them drink water that I felt was too dirty to touch. When I was in eighth grade, I decided to do something about it. Clean, Green, and Fast Currently in many developing countries, water is purified for drinking through solar disinfection (SODIS). In the SODIS method, water is poured into a colorless transparent bottle made of PET (polyethylene terephthalate) and left in the sun for at least six hours. The powerful UV radiation in sunlight inactivates disease-causing pathogens, making the water safe to drink. SODIS is simple and inexpensive, but it is very slow. In cloudy weather, it can take up to two days to purify a 2-liter bottle of water. In the last decade, the SODIS process has been accelerated by photocatalysis. When UV radiation strikes a photocatalyst, such as titanium dioxide, highly reactive oxygen species (ROS) are created. These ROS both kill bacteria and degrade organic chemical compounds, such as benzene and toluene, pollutants that cause severe health problems. However, because the photocatalysts are usually applied as coatings inside the PET bottles, they often wash off into the water, which means people end up drinking the photocatalyst. In addition, the photocatalysts currently in use actually block some UV radiation, diminishing the efficiency of the SODIS process. Three years ago, after researching ways to use the sun to purify water, I set out to overcome these drawbacks. I spent hundreds of hours reading scientific papers, building prototypes, and test- 8 imagine ing contaminated water samples in a makeshift lab in my garage. Eventually I submitted a video describing my idea for harnessing solar energy to purify water to the 2012 Discovery Education 3M Young Scientist Challenge. When I was named a finalist, I was assigned a mentor from 3M. Over the course of several weeks, my mentor, Dr. James Jonza, provided valuable guidance as I developed a pervious photocatalytic composite, which I integrated into a water purification panel. When exposed to sunlight, this device removes both bacteria and organic chemical compounds from water. I continued working independently on my project the next year. While researching ways to harness not just UV light but visible light, I found several journal articles that described the use of semiconductors, such as silver, as doping agents. I decided to add silver nitrate to my composite, which extended the photocatalytic activity of my composite from the ultraviolet (which makes up just 3% of solar radiation) into the visible light spectrum (44% of solar radiation). In order to further enhance the efficiency of water purification, in 2014 I devised a process that combines filtration with photocatalysis: First, water percolates through a filter created with novel pervious composites, which destroys 98% of coliform bacteria and degrades organics. This filtered water is then transferred to a container with a disc made of the photocatalytic composite. Exposing the container to sunlight results in 100% inactivation of coliform bacteria-in just 15 minutes. Research, Rewarded Excited by these results, I submitted my project to the 2014 Stockholm Junior Water Prize (SJWP), the world's most prestigious youth science competition for water-related research. After winning the May/June 2015

Table of Contents for the Digital Edition of Imagine Magazine - Johns Hopkins - May/June 2015

Big Picture
In My Own Words Daniel Kammen, Professor of Energy, UC Berkeley
A Solar-Powered Solution to the Water Crisis Using the sun to purify water
The PolluCell Generating electricity using waste and pollution
More than a Race The Solar Car Challenge
Energy Agenda The power of teen research
Energized! A crash course in fuels of the future
Grease Is Good Helping the environment and the community with biofuel
Fueled by Algae Sara Volz and the powerful potential of pond scum
The Future of Energy Five careers in green power
My Sanskrit Yaatra Connecting with my culture through language
Devoted Awareness My internship with Until There’s a Cure
Selected Opportunities and Resources
Off the Shelf Review of Ralph Ellison’s Invisible Man
Word Wise
Exploring Career Options Interview with green architect Andrew Thompson
One Step Ahead Six things incoming college students should know
Planning Ahead for College Developing your passions
Students Review: University of Pennsylvania
Creative Minds Imagine
Mark Your Calendar
Knossos Games

Imagine Magazine - Johns Hopkins - May/June 2015