 "Photo: Melissa Chi")
Since the early 1900s, America has pioneered the disinfection of water, and now, a century later, the research of Isabel Escobar, an associate professor of chemical and environmental engineering at UT, furthers the technology of water treatment.
Every year, approximately 4.5 million people die of waterborne disease throughout the world, the equivalent of one child every 15 seconds, Escobar said in her lecture titled “What’s in Your Water?” held Thursday at the Lake Erie Center.
Escobar said the first water disinfection technology eliminated the acute toxicity of water, or waterborne diseases that could kill a person immediately. After that technology was developed, researchers began focusing on more refined disinfection to eliminate the chronic toxicity of water, or water with contaminants that could kill a person over a prolonged period of time, she said.
“The idea of acute toxicity — so, if you drink water that’s highly contaminated with pathogens, you will die, and then the idea of the chronic toxicity that if you drink water with a carcinogenic every day for the next 40 years, you develop cancer,” she said.
Escobar’s research deals with membrane filtration, which is the technology used to eradicate the chronic pathogens in water. Escobar said a membrane is essentially a piece of plastic through which water is pushed to filter out harmful contaminants.
There are several classifications of membranes based on the size of the pores, with the largest being micro-filtration, followed by ultra-filtration, nano-filtration and reverse osmosis. Reverse osmosis uses a plastic or polymer so dense the water is defused on a molecular level. Escobar said reverse osmosis can achieve desalination, or the removal of salt from water, allowing humans to tap into ocean water for drinking as opposed to less-abundant fresh water.
“You can imagine that anything that’s not the water molecules will be rejected, will stay on that surface of the membrane, so all of a sudden those materials, they lead to what we call ‘fouling,’” she said.
The process of fouling is the accumulation of contaminants on the surface of the membrane, which create a new layer of resistance to the flow of water through the membrane and results in the need for increased pressure.
“You’re just adding layers of resistance to that flow, so you’re increasing pressure, and pressure is directly related to dollars,” Escobar said. “Water is becoming more and more expensive as you do that, so we do research in ways of preventing that fouling from happening.”
Some of Escobar’s students, like Colleen Gorey, a doctoral student in the department of chemical and environmental engineering, are researching ways of developing new ultra-filtration membranes that are self-cleaning with low fouling. Escobar’s research, however, deals specifically with reverse osmosis and desalination.
Unlike the strong membranes used in Gorey’s research, the membranes used in reverse osmosis are very fragile, Escobar said. Instead of working to change the properties of the membrane, Escobar’s research deals with modifying the plastic “feed spacer” the membrane is rolled onto.
The “feed spacer,” made from polypropylene, provides channels for the water to flow over into the membrane. Escobar said it is within the design of those channels that fouling settles and bacteria begin to grow and attach to the spacer.
Escobar said polypropylene is a polymer commonly found in the food packing industry, which makes it ideal for use in water filtration systems because it is safe for long-term use and won’t contaminate the water.
Escobar’s research deals with modifying the polypropylene spacer on a molecular level by introducing copper in the form of an electrolyte. The introduction of copper to the molecular structure of the polypropylene disrupts cellular respiration, or the ability of bacteria to grow and thrive in the channels on the spacer.
This technology can drastically reduce the layers of resistance created by fouling, which would reduce the amount of pressure needed to push water through the membrane and ultimately decrease the cost of water. In addition to the technology’s effects on the cost of water filtration, Escobar said it helps increase the life expectancy of the membrane itself.
Current membranes have a life expectancy of about five to 10 years. She said that if engineers can increase this lifespan, it would reduce the cost of membrane filtration systems, making them more affordable to parts of the world that are in dire need of water.
While researchers and engineers have moved on to eradicating the chronic toxicity of water in America, Europe, Australia and areas of Asia, Escobar said many parts of Africa and Latin America are still focusing on the acute toxicity and preventing the immediate deaths from waterborne diseases.
Escobar said the Great Lakes contain the largest amount of fresh water in the world, resulting in a fairly good outlook for the states that can tap into them. However, other areas of the country, including Florida, California, many southern states and the Great Planes Region, are experiencing water crises that have even resulted in riots, she said.
“Historically, the majority of the wars in the world have been fought over water rights,” Escobar said.
Johan Gottgens, a professor of environmental sciences, attended Escobar’s lecture.
“I think Dr. Escobar is correct; drinking water is one of the most critical resources currently, and in the future and in the past,” he said. “So, one of the big challenges for us is to make sure there is enough potable [or drinkable] water where the quality can be safeguarded for the increasing population.”
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