Safe, clean drinking water is a fundamental human need. Orlando Coronell at the University of North Carolina at Chapel Hill is developing improved membrane technology to purify drinking water more effectively and efficiently. "Human Water Cycle" is produced by NBC Learn in partnership with the National Science Foundation.
Human Water Cycle -- Drinking Water
ANNE THOMPSON reporting:
Safe, clean drinking water. We take it for granted every time we turn on the faucet, and yet we are highly dependent on it. In fact, approximately 86% of the U.S. population, about 270 millionpeople, relies on a public water supply, using about 42 billion gallons per day.
ORLANDO CORONELL (UNC at Chapel Hill): Water is in almost every single aspect of our lives. We need water to irrigate our crops, so our food also depends on water. We need water to produce energy in power plants.
THOMPSON: Water, food and energy are part of something called the human water cycle, a concept that shows how these three vital aspects of human life are interconnected. Orlando Coronell is a professor of environmental sciences and engineering at the University of North Carolina at Chapel Hill and funded by the National Science Foundation. His research focuses on the connection between water and energy.
CORONELL: To produce water for drinking purposes, we need to use energy. Energy is used to move the machinery that cleans water.
THOMPSON: Drinking water comes from lakes, streams and underground aquifers, and it can become contaminated in a number of different ways. For example, from fertilizer runoff and animal waste from agriculture, to chemicals discharged from factories, to viruses and bacteria in sewage systems. Water treatment plants remove these contaminants before water flows into the public supply. While necessary for public health, water treatment plants use a lotof energy and are expensive, a cost which is eventually passed on to consumers. Membrane technology is currently used to purify water. There are two types:
CORONELL: Low-pressure membranes are used to remove what we consider in the water treatment world big contaminants. Micro-organisms for example, protozoa or parasites or bacteria. High-pressure membranes on the other hand are used to remove things that are much, much, much smaller.
THOMPSON: But like any filter, membranes can ultimately become clogged. To help solve this problem, Coronell and his research team are developing something called thin-film nanocomposites, a type of high-pressure membrane embedded with nanoparticles that allows water to flow through faster and more efficiently. These membranes are just 300 microns thick, roughly 3 times the diameter of a human hair, and are composed of three different layers: the top active layer and two support layers.
CORONELL: The top layer is what we call the active layer and we call it the active layer because it is the layer responsible for the water productivity and contaminant removal capabilities of the membrane.
THOMPSON: The top active layer of the membrane is fabricated in the lab by taping the two pre-fabricated support layers to a glass plate and dipping it into two different chemicals.
KASIA GRZEBYK (UNC at Chapel Hill): This is a finished thin-film composite membrane and then the polyamide active layer that we fabricate is the really shiny layer that you can see. It’s ready to turn on the pump.
THOMPSON: The team tests the membrane's efficiency by pumping dirty water through a cross-flow filtration system and increasing the pressure over a set period of time. Samples of the clean and dirty water are then taken and compared to see how much of the contaminants are being removed by the membrane.
CORONELL: Ultimately, we want to make the technology more affordable to benefit communities all over the world that are in need of drinking water.
THOMPSON: Coronell's team incorporates nanoparticles with different properties in this top active layer that allow water to flow more efficiently through the membrane, while still maintaining or increasing the amount and types of contaminants it removes.
TONY PERRY (UNC at Chapel Hill): Some of the nanoparticles that I am working with basically self-assemble into these very unique like structures, and as a result of that, they form these highly, highly porous framework like materials or scaffolds.
THOMPSON: Coronell hopes creative new technologies like his will save energy and money and ensure a safe, plentiful supply of drinking water for a more sustainable human water cycle.
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