Old methods of filtering water involved distillation by using heat to evaporate and then condense contaminated water, leaving behind impurities. The amount of energy needed for this process makes it prohibitively expensive.
Modern technologies involve filtration, utilizing materials such as sand, gravel, and activated carbon. Filtration through permeable membranes is also commonly used. Following filtration, water is chlorinated to treat waterborne infectious bacteria, such as E.coli.
Foudazi and a group of graduate and undergraduate are developing nanofiltration, ultrafiltration, and microfiltration membranes. These membranes can filter out impurities, such as heavy metals, nitrates, and other substances that taint water, along with treating proteins, bacteria and viruses that accumulate on the surface of membranes, thus eliminating the need for chlorine treatment.
“Chlorine is not a safe chemical and it has health effects and produces harmful disinfection byproducts. While the Environmental Protection Agency regulates the use of chlorine, it is a trade-off,” said Foudazi.
Nanofiltration and ultrafiltration membranes have very small pores – from a few nanometers to about 100 nanometers. Foudazi is experimenting with different pore sizes to ensure that the separation of contaminates is effective.
Additionally, the membranes are made from compounds that possess antibacterial qualities. Conventional antibacterial membranes are created through the application of antibacterial substances to the surface of the membranes through complex and expensive processes that require the use of harmful solvents.
Perhaps the biggest challenge in membrane technology is increasing the flow rate while decreasing the energy requirement used to push the fluid through the membrane. Highly permeable membranes can filter the water by gravity rather than being pushed by some means requiring electricity.
“We are using materials that are commercially available, such as surfactants, compounds that are found in everyday products like detergents and personal hygiene products.” Surfactants lower the surface tension between the liquid and solids. Foudazi uses a templating approach in which a high density of pores with same size can be produced within a thin polymeric layer.
Foudazi estimates that this process may render the water filtration process roughly 50 percent less expensive than conventional methods. His process can be scaled-up for industrial purposes as well as adapted in small portable units for production in rural areas and small communities.
This technology also has usefulness in the biomedical field and could be used to create artificial kidneys, said Foudazi. “The membrane works just like our kidneys – they filter the blood to remove waste and control the balance of the blood.”
With potential for commercialization, Foudazi is working with NMSU’s Arrowhead Center on patenting the process. He already has two patents related to technologies used in the capture of carbon dioxide.