Researchers collaborate to improve water purification
Water is necessary for living, but the water purification process has problems — and two University of Houston engineering professors are working together to solve the costly issues of mineral scaling and biofoul buildup in water desalination plants.
Debora Rodrigues, associate professor of civil and environmental engineering for the Cullen College of Engineering, and Yandi Hu, an assistant professor for the same department, teamed up in January with a $184,000 grant from the Qatar National Research Fund to begin a three-year research project to make water purification less expensive for desalination plants.
“I want to try to develop technologies that are useful to society,” Rodrigues said. “This is one of them because the water problem is a worthwhile problem that affects lots of people. We’re having more water scarcity, so desalination is a good alternative for using the water from the ocean. It’s an alternative to get clean water.”
Saltwater, which makes up 97 percent of the earth’s water supply, must go through the desalination process to become potable water. At desalination facilities, seawater passes through filters, or membranes, which remove salt and minerals from the water.
Previously, Rodrigues worked with a UH startup called WAVVE Stream Inc. that offers technologies to enhance contaminant removal capabilities in water filtration systems — similar to Brita-type filters, she said. Her and Yu’s new technology improves the coating of membranes in desalination plants.
The current problem is two-fold: The accumulation of microorganisms and salt on desalination membranes — known as biofoul build-up and mineral scaling, respectively — prevents water from flowing through. Purification plants must either increase water pressure or temporarily halt production to clean or replace the membranes.
Rodrigues said the mineral scaling problem is akin to what happens in showerheads without water softeners.
“It’s like when water dries up (on showerheads), and a white-ish powder builds up on the surface with hard water,” she said. “Sometimes, like in your shower maybe, it gets clogged … Scaling is a fancy name to say that there is the formation of these crystals of calcium that blocks the pores of the membrane.”
Continuing the comparison, Rodrigues said that biofoul buildup is like going a long time without cleaning shower walls — microorganisms build up and turn the walls yellow. The biofoul is the same — an accumulation of microorganisms growing in the desalination membrane.
Hu, who worked to remove lead from pipes during the Flint water crisis, said the duo divide the work into their two strong suits.
“I’m more on the chemistry side, and she’s more on the microbiology side,” Hu said. “That’s why it’s nice to have collaborative work because one person knows one aspect. But this is a problem that is occurring simultaneously in the treatment systems. You have to solve both problems: mineral scaling and biofouling. You cannot solve only one problem because the other problem might become worse.”
Hu said they have already developed a new membrane coating made of a polymer-modified graphene oxide nanocomposite, which has never been used in desalination membranes. The next step in their research is to see how the new coating reacts to biofoul and mineral scaling.
If their research is as successful as they hope it will be, then the new technology could cut down costs for desalination plants. Hu said that in one case, a California desalination plant spent $728,000 cleaning membranes — consuming about 30 percent of the plant’s operating costs.
“The membrane is part of the costs,” Rodrigues said. “There’s also the energy involved as well … And also, having to stop the water treatment to remove the membrane and replace it means the whole treatment system is down for several hours, and they lose money with that, too.”
Though this is a three-year project, Hu hopes to continue working on the technology for even longer to collaborate with other faculty members in developing a better coating and, ultimately, improve to the water purification process.
“I believe we can make it more efficient,” Hu said. “Basically, we could lower the operation costs and have longer membrane lifetimes.”