Researchers from Ben-Gurion University of the Negev (BGU) and the University of Illinois at Urbana-Champaign (UIUC) said they have developed new ultrafiltration membranes that significantly improve the process of removing viruses from treated municipal wastewater used for drinking in water-scarce cities.
Current membrane filtration methods need intensive energy to adequately remove pathogenic viruses without using chemicals like chlorine, which can contaminate the water with disinfection.
The norovirus, for example, which can cause nausea, vomiting and diarrhea, is the most common cause of viral gastroenteritis in humans, and is estimated to be the second leading cause of gastroenteritis-associated mortality.
Human adenoviruses can cause a wide range of illnesses that include the common cold, sore throat, bronchitis, pneumonia, diarrhea, pink eye (conjunctivitis), fever, bladder inflammation or infection, inflammation of the stomach and intestines, and neurological disease, the researchers, Prof. Moshe Herzberg of BGU and Prof. Nguyen Thanh H. Nguyen of UIUC said in a statement.
“This is an urgent matter of public safety,” Herzberg and Nguyen said.
“Insufficient removal of human Adenovirus in municipal wastewater, for example, has been detected as a contaminant in U.S. drinking water sources, including the Great Lakes and worldwide.”
In the study, Herzberg, of the Department of Desalination and Water Treatment in the Zuckerberg Institute for Water Research at BGU, and his group grafted a special hydrogel coating onto a commercial ultrafiltration membrane.
The “zwitterionic polymer hydrogel,” as it is called, repels the viruses and does not allow it to approach or pass through the membrane.
It contains both positive and negative charges and improves efficiency by weakening virus accumulation on the modified filter surface.
The result was a significantly higher rate of removal of waterborne viruses, including human norovirus and adenovirus, the researchers said..
“Utilizing a simple graft-polymerization of commercialized membranes to make virus removal more comprehensive is a promising development for controlling filtration of pathogens in potable water reuse,” said Nguyen.
The research was published in the current issue of Water Research.
The project was supported by the US Environmental Protection Agency and the German-Israeli Water Technology Cooperation Program, which is funded by the Ministry of Science & Technology of Israel and the Federal Ministry of Education and Research of Germany.
Potable water reuse has been adopted by cities suffering water scarcity in recent years.
The microbial safety in water reuse, especially with respect to pathogenic viruses, is still a concern for water consumers.
Membrane filtration can achieve sufficient removal of pathogenic viruses without disinfection byproducts, but the required energy is intensive.
In this study, we graft-polymerized zwitterionic SPP ([3-(methacryloylamino) propyl] dimethyl (3-sulfopropyl) ammonium hydroxide) on a 150 kDa ultrafiltration polyethersulfone membrane to achieve a significantly higher virus removal.
The redox-initiated graft-polymerization was performed in an aqueous solution during filtration of the monomer and initiators, allowing for functionalizing the membrane pores with hydrophilic polySPP.
Bacteriophage MS2 and human adenovirus type 2 (HAdV-2) were used as surrogates for pathogenic human norovirus and human adenovirus. The grafting resulted in ∼18% loss of the membrane permeability but an increase of 4 log10 in HAdV-2 removal and 3 log10 in MS2 removal.
The pristine and the grafted membranes were both conditioned with soluble microbial products (SMP) extracted from a full-scale membrane bioreactor (MBR) in order to test the virus removal after fouling the membranes.
After fouling, the HAdV-2 removal by the grafted membrane was 1 log10 higher than that of the pristine membrane.
For MS2, the grafted membrane after fouling with SMP achieved an additional 5 log10 removal compared to the unmodified membrane.
The simple graft-polymerization functionalization of commercialized membrane achieving enhanced virus removal efficiency highlights the promise of membrane filtration for pathogen control in potable water reuse.
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Zwitterionic polymers have shown ultra-low biofouling properties at surfaces and excellent biocompatibility as implant.
In this study, an in situ-forming zwitterionic hydrogel was designed and evaluated, both in vitro and in vivo, as a long-term vitreous substitute.
The zwitterionic polymer poly(MPDSA-co-AC) was designed as a copolymer of the sulfobetaine methacrylamide and acryloyl cystamine monomers, providing the zwitterionic components and the thiol functional groups, respectively.
The in situ gelation was via the thiol–ene Michael addition reaction with α-PEG-MA as the crosslinker.
The gelation time, rheological properties, swelling profiles, and the transparency of zwitterionic hydrogels were studied in detail. Two systems with different crosslinker concentrations were tested in a rabbit model, and the one with the thiol–ene ratio of 2 : 1 showed excellent biocompatibility in vivo, formed space-filling hydrogels and remained transparent in the vitreous cavity for the 2 month implantation period.
Therefore, in situ-forming zwitterionic hydrogels represent a promising material system as a vitreous substitute and possibly for other soft tissue replacements.