Hydrogel membrane improves virus filtration

CHEMICAL methods of removing viruses from drinking water could soon be replaced by a simple filtering method.

The use of a hydrogel-coated membrane could increase public safety in water-scarce regions by improving treatment methods for reused drinking water.

Facilities turning wastewater effluent into drinking water may become more common in response to severe drought, and have already been pioneered in Texas, US. But with a single litre of raw sewage containing up to 100m disease-causing viruses, microbial safety is a lasting concern.

Viruses are the smallest of all waterborne pathogens, and thus the most difficult to remove by techniques such as sedimentation and filtration. So far, disinfection methods such as UV and chlorine have been adopted, but their effectiveness is debated and they can contaminate the water with by-products such as trihalomethanes.

In response to these challenges, a recent collaborative study between researchers from Ben-Gurion University of the Negev (BGU) and the University of Illinois at Urbana-Champaign (UIUC) has demonstrated an effective filtration method. The researchers successfully grafted a zwitterionic hydrogel, which can be used as a foulant repellent, onto a commericially-available ultrafiltration membrane.

The coating, consisting of SPP ([3-(methacryloylamino) propyl] dimethyl, was applied through redox-initiated graft-polymerisation in an aqueous solution using potassium persulphate and potassium metabisulphite as initiators. In order to achieve a homogenous coating of polySPP within the membrane pores, the monomers and initiators were applied simultaneously.

Thanh Nguyen, associate professor at UIUC’s Department of Chemical Engineering, said: 'Utilising a simple graft-polymerisation of commercialised membranes to make virus removal more comprehensive is a promising development for controlling filtration of pathogens in potable water reuse.'

The hydrogel was demonstrated to effectively repel waterborne human disease virus surrogates from approaching and passing through the membrane. Although there was approximately an 18% loss in membrane permeability following grafting, when compared to an ungrafted membrane, removal of the pathogenic human norovirus surrogate (MS2) and human adenovirus (HAdV-2) was increased by 1,000 and 10,000 times respectively.

Human adenovirus is the most common cause of viral gastroenteritis in humans, and is estimated to be the second leading cause of gastroenteritis-associated mortality. The researchers said: 'This is an urgent matter of public safety. Insufficient removal of human adenovirus in municipal wastewater, for example, has been detected as a contaminant in US drinking water sources, including the Great Lakes and worldwide.'

Water Research: http://doi.org/b5x4