By Peter Chawaga
Though membrane technology is one of the fastest-developing aspects of water treatment, much is left to be done to ensure that the barriers can rid effluent of all the contaminants it might carry. Despite advances in nanotechnology, 3-D printing, and microfiltration, much can still be done to improve membranes.
Those needs continue to inspire projects like a recent one led jointly between researchers from the University of Illinois (UI) and Ben-Gurion University of the Negev (BGU) in Israel, which sought to develop a hydrogel that can keep viruses from entering water supplies.
“This research was inspired by the acute problem of waterborne pathogens, including viruses, in tertiary wastewater effluents,” the researchers, Dr. Ruiqing Lu and Professor Thanh
Nguyen from UI and Professor Moshe Herzberg from BGU, said in a joint statement. “Control of waterborne pathogens has been the focus of Nguyen, while Herzberg has been working on making the membrane technology better. We initiated this specific research due to the increasing demand for water reuse in the United States, in Israel, and across the globe.”
The researchers focused on membrane bioreactor (MBR) technology, which can yield high-quality treated wastewater without the byproducts that can result from chemical disinfection. While they acknowledged that the membrane market is making big strides, it lacks products that focus on virus removal.
“The current membrane filtration process was not designed for virus removal,” they said. “Our study showed that it is possible to achieve high virus removal while avoiding the negative effects of membrane degradation due to other constituents in the wastewater.”
The team developed a new ultrafiltration membrane that utilizes “zwitterionic polymer hydrogel” that holds both positive and negative charges to weaken virus accumulation on the filter surface. The work yielded significantly better removal of waterborne viruses compared to traditional solutions, including the norovirus and adenovirus that can target humans.
“The zwitterionic coating on one hand has almost no effect on membrane permeability and, on the other hand, improves membrane selectivity toward rejection of macromolecules as well as viruses,” said the researchers. “[This efficacy is] due to reducing the osmotic pressure in close proximity to the membrane surface, elevating hydration of the surface, and repelling non-specifically various biological colloids and macromolecules, including viruses.”
Nguyen and Herzberg have been leading independent research that, when combined, made this new membrane technology possible. Nguyen had found that, because of viruses’ unique structure, they can be prevented from collecting on certain surfaces. Herzeberg’s studies found that a zwitterionic coating could prevent wastewater molecules from sticking to a membrane and reducing its permeability. When the researchers exchanged ideas, they developed a solution that both repels viruses and maintains permeability.
“We thought that since Herzberg’s membrane has the same properties that viruses have to prevent them from sticking to another surface, this membrane should allow higher virus removal compared to commercial membranes, while keeping the same volume of water flowing through the membrane pores,” the researchers said.
The ability to better reduce harmful viruses in the environment is one that all wastewater treatment plants should want. But, as with any new technology, they’ll need to know when this solution will become available in an affordable form. In this case, it may be some time.
“We are looking for funding sources in order to develop the technology beyond this ‘proof of concept’ stage,” said the researchers. “We plan on developing an ultrafiltration membrane module that will be applicable for improving virus rejection without affecting membrane permeability.”
A test unit that demonstrates the efficacy of this new membrane could go a long way in getting the technology developed and produced at commercial scale. Until then, treatment operations will be on the lookout for the next great membrane innovation.