A silver lining in the fight for clean water in India

Outside of a school in a rural village in India, a young student wearing a sari and head scarf turned a spigot. Water, transported to the site by a truck or collected in storage containers from the last rain, started to trickle out from the enormous concrete cistern. She cupped her hand under it and drank.

How that water – clean in taste and free of the bacteria and viruses that cause three-quarters of illnesses in developing countries – reaches students is a story that connects a critical water treatment breakthrough with data modeling and the on-the-ground work of graduate students in Virginia Tech’s College of Natural Resources and Environment.

The results of that effort: clean water for students in one of the poorest regions on the planet and a new roadmap to ensure that everyone has affordable access to healthy water.

From silver ions to computational data modeling

“The process of using silver ions to disinfect water is now a common, established solution for households in low- and middle-income countries,” said Luke Juran, associate professor in the Department of Geography and an affiliated faculty member of the Virginia Water Resources Research Center. “All you have to do is have a bucket of water and leave a water treatment tablet in overnight. It will kill bacteria and other microorganisms without changing the taste of water.”

The water treatment tablet – called MadiDrop+ – was developed by University of Virginia Professor James A. Smith '83, M.S. '84, who began trialing silver-embedded ceramic tablets as an inexpensive alternative to purifying water in 2015. Today, one pocket-sized tablet is capable of treating 20 liters of household water every day for an entire year.

“I thought, 'Let’s take this technology and see if we can upscale it to the community level,'” said Juran. “There are schools and hospitals and restaurants and government buildings that all use large tanks of water for drinking. How can we implement this technology on a larger scale?”

To find out, Juran secured a grant from Virginia Tech’s Institute for Society, Culture, and Environment’s Scholars Program to trial the use of MadiDrop+ tablets at the community scale. He is collaborating on the project with co-principal investigators James A. Smith and Assistant Professor Alasdair Cohen of the Virginia-Maryland College of Veterinary Medicine's Department of Population Health Sciences

As a first step and in preparation for doing the needed field research, Juran asked Dillon Mungle '22 – at the time an undergraduate student majoring in water resources policy and management in the Department of Forest Resources and Environmental Conservation – to conduct data models predicting tablet effectiveness in large water containers.

“My work was entirely computational,” said Mungle, who is currently pursuing a Master of Science in groundwater and global change at the IHE Delft Institute for Water Education in the Netherlands. “We knew the approximate water volume of the tanks and the rate at which the tablets release silver ions, so based on those variables, I created an optimization function designed to identify the ideal number and positioning of MadiDrop+ tablets.”

The model that Mungle created allows users to enter a few variables that describe conditions at a water tank site - tank dimensions, usage patterns, and refill timings - to determine the optimal number and positioning of tablets.

“I developed the model with the hope that it can be useful beyond this pilot study,” said Mungle, who received scholarship funding from the Stephen H. Schoenholtz Undergraduate Research Fund. “One important strength is that the optimization process can be modified to incorporate newly observed data."

With a data model in hand, Juran’s group partnered with the Sehgal Foundation, a nongovernment organization in India that provides support for community-led development.

Their first aim: trying to provide rural schools in need of cost-effective, clean water.

Making an impact for schools in rural India

“We felt like celebrities,” said Emily Wilcox, a master’s student in geography and one of two graduate students who collected water samples for testing. “The children at the schools would swarm around us trying to practice their English. When we’d be getting our samples, we’d have an audience of kids watching us.”

Working with three schools in Nuh district, a rural farming region an hour from the capital city of New Delhi, Wilcox and Meghan Albritton spent eight weeks over the winter break installing the MadiDrop+ tablets and then collecting water quality of tank inflow and outflow to assess the disinfection capacities of the tablets on a larger scale.

“We know that these tablets work at the household level, so our goal was to figure out what ratios would look like on a larger scale,” said Albritton, a dual master’s student in geography and public health. “The tanks we’re looking at can hold about 500 liters of water, and the tablets don’t require any maintenance. So if we can figure out how to find the right balance, it would serve as a new option for schools.”

One dimension they had to account for was the change in water levels as students use the tanks. For silver ions to be effective against bacteria, viruses, and mosquito larvae, there should be a concentration of 25 to 40 micrograms of silver per liter, with the World Health Organization recommending an upper limit of 100 micrograms per liter to ensure safe human consumption.

To reach that successful midpoint, Albritton and Wilcox used an old technology – string – to suspend a certain number of tablets at varying depths in the water tank, while keeping others at the bottom of the tank. That way, as the water level dropped during the day, the silver levels would remain within the recommended range.

“We added a pressure transducer sensor to monitor water levels throughout the day,” said Wilcox. “We were trying to figure out the right number of tablets to have at the bottom of the tank, and how many to suspend on string. It was a lot of trial and error, but our early results are very positive.”

The ongoing work required - daily collection of water samples, constant adjustment to refine the processes, and then long afternoons of lab analyses of bacteria levels – was made more challenging by the demands of working remotely in the field.

“In a lab, you have control over when your tanks are being emptied and what your exact concentrations of silver are,” said Albritton, who is from Rockmart, Georgia. “In India, we were relying on people to empty tanks and keep us updated in a language we couldn’t speak. We were also coordinating between schools and labs and the Sehgal Foundation, so there were a lot of moving parts.”

Those challenges could be as simple as trying to coordinate with someone at a school to open a gate or as complicated as trying to access a spectrophotometer – a tool that uses light to measure the concentration of a chemical substance in water – to determine silver levels in water samples.

Early results from the students’ efforts suggest that silver tablets are a promising solution.

“We haven’t run the actual statistics yet, but we saw a huge decrease in the amount of bacteria in the water after the MadiDrop+ tablets were added to the tanks, based on the number of colonies that were growing on plates in the lab,” said Albritton.

Adapting solutions to fit a place

Juran plans to build on this pilot research by expanding to more schools for extended periods of time.

“We hope to expand our offerings of undergraduate and graduate research experiences overseas,” said Juran, who is an affiliated faculty member of the Fralin Life Sciences Institute and the Center for Emerging, Zoonotic, and Arthropod-borne Pathogens. “With this project, I’d like to explore the utilization of new technologies, such as printing 3D structures to suspend MadiDrop+ tablets in tanks as well as experimenting with the next generation of tablets that also include copper as a disinfectant.”

Both Wilcox and Albritton said that experiences like their work in India are exactly why they chose to pursue degrees in geography.

“I knew I wanted to go into a geography department because I wanted to study climate and environmental research, but I wanted my work to have a human dimension,” said Wilcox. “Immersing myself in a new culture was a life-changing experience, and I’m really glad to be working on a project that aims to improve the health of so many children.”

For Juran, such experiences are critical in preparing geography students to take on tangible challenges in the world.

“What I try to teach in my classes is that the solutions my students will find to problems will exist in a place and among people,” he said. “Our solutions have to interface with society, with environments, with political systems, and with communities. The only way to really understand and experience that is to get out into the field.”