A microfiltration membrane was developed to filter water and reduce viral counts of a model bacteriophage. The LbL coating of the filters was performed with the synthetic polycation, poly(ethylene imine) which was covalently immobilized onto the poly(ether sulfone) water membrane material. Silver and copper nanoparticles were also coated in the LbL layers, and although an effective antiviral performance was seen, leached markedly into the filtered water [125].