A University of Saskatchewan student is researching a process that could make purifying water efficient and sustainable.
Anurag Dalai, a fourth-year physiology and pharmacology student, has discovered a particle that kills waterborne bacteria more effectively than bleach or alcohol. These nanoparticles emit a specific type of ultraviolet light that damages harmful bacterial cells like E. coli.
“Essentially, we wanted to see if we could create a novel way of cleaning water that is sustainable and efficient. We specifically looked at UV light because UV light is known to kill bacteria and this technology is used in [developing] countries for cleaning both air and water,” Dalai said, adding that UV technology is expensive to buy, install and maintain.
Dalai’s method is trying to solve issues with the current water UV purification methods where the light penetrates the water from outside. Issues arise if the water is dirty to a certain threshold, since the light then cannot penetrate it as easily and the method becomes less efficient.
“We wanted to see if we could create a way for that same UV light to be emitted within the water itself, thus eliminating that problem,” Dalai said.
In the electromagnetic spectrum, UV light ranges from 100 nanometers to 400 nanometers. Light in this range can interact with and damage bacterial DNA — a process that is well documented. Dalai uses an X-ray machine to excite calcium fluoride nanoparticles causing them to emit UV light that kills bacteria. Specifically, calcium fluoride emits UVB light which is what E. coli cells are most vulnerable to. He uses calcium fluoride because it is insoluble in water and can be filtered out easily.
In lab trials, Dalai used a technique called spectroscopy to measure the wavelength of light emitted from the nanoparticles. If the particles emitted the correct wavelength they were tested to see if they could kill bacterial cells. Dalai put crucibles containing E. coli bacteria and calcium fluoride inside an X-ray machine and exposed the samples for variable lengths of time.
Dalai found that the longer the samples were exposed to the X-rays, the more bacteria were killed. He stained the samples with a fluorescent dye and examined them under a specialized microscope to count the living and dead cells.
The goal of Dalai’s project was to show that UV light emitted from nanoparticles can be harnessed to kill E. coli cells more effectively than bleach or alcohol and he came out with positive results.
“We essentially completed the first phase of the project where the primary goal was to show that this technology can work and does work,” Dalai said.
Dalai also experimented with gamma radiation but it was ineffective.
Ideally, Dalai would like to see the UV purification method used on a larger scale to help villages in developing countries where “it will go a long way in preventing people getting sick from water contamination.” Urban populations could also benefit by making existing water treatment methods more efficient with UV light.
The next step of the project is to create a nanoparticle that doesn’t require energy excitation from an outside source like an X-ray. Dalai said the final product may be a system where UV emitting nanoparticles pass through water as it flows through a pipe.
Dalai started the project in the summer of 2011, after completing the first year of his degree. He contacted Ramaswami Sammynaiken, manager of the Saskatchewan Structural Sciences Centre and got to have his pick of a few projects.
“I chose to do this specific project because of its potentially positive impact on people’s lives and the original idea seemed interesting. Also, it was an interdisciplinary project where I could learn about chemistry, biology and physics as well as learn how to operate various pieces of equipment,” Dalai said.
Dalai spent the next two summers working on the project under the supervision of Sammynaiken.
“He helped me at every step of the way by providing the lab, materials and helping design experiments,” he said.
Dalai also worked with Jian Yang, an associate professor from the College of Pharmacy and Nutrition. His co-researchers included Abdalla Karoyo and Angela Dong, a PhD student in chemistry and a graduate student in pharmacy, respectively.
“In general, learning all the procedures, techniques, and reading up on all the science behind the experiments was a challenge. But I learned a great deal and the entire process was greatly beneficial,” Dalai said.
Dalai is confident that the project will continue going forward but he is unsure if he will be involved with the next stages.
Photo: Jordan Dumba/Photo Editor