Virus disinfection in water by biogenic silver immobilized in polyvinylidene fluoride membranes

The development of innovative water disinfection strategies is of utmost importance to prevent outbreaks of waterborne diseases related to poor treatment of (drinking) water. Recently, the association of silver nanoparticles with the bacterial cell surface of Lactobacillus fermentum (referred to as biogenic silver or bio-Ag0) has been reported to exhibit antiviral properties. The microscale bacterial carrier matrix serves as a scaffold for Ag0 particles, preventing aggregation during encapsulation. In this study, bio-Ag0 was immobilized in different microporous PVDF membranes using two different pre-treatments of bio-Ag0 and the immersion-precipitation method. Inactivation of UZ1 bacteriophages using these membranes was successfully demonstrated and was most probably related to the slow release of Ag+ from the membranes. At least a 3.4 log decrease of viruses was achieved by application of a membrane containing 2500 mg bio-Ag0powder m−2 in a submerged plate membrane reactor operated at a flux of 3.1 L m−2 h−1. Upon startup, the silver concentration in the effluent initially increased to 271 μg L−1 but after filtration of 31 L m−2, the concentration approached the drinking water limit ( = 100 μg L−1). A virus decline of more than 3 log was achieved at a membrane flux of 75 L m−2 h−1, showing the potential of this membrane technology for water disinfection on small scale.

Research highlights
► In biogenic silver, silver nanoparticles are attached to a bacterial carrier matrix.
► Bio-Ag0 was successfully immobilized in PVDF membranes using immersion-precipitation.
► The antiviral activity of this material was demonstrated in a plate membrane reactor.
► The antimicrobial mechanism was most probably related to the slow release of Ag+ ions.
► The membranes can be applied for treatment of limited volumes of contaminated water.