ABSTRACT
Membrane separation processes find applications in an array of fields as they use far less energy and chemical agents than competing processes. However, a major drawback of membrane technology is that biofilm formation alters membrane performances. Preventing biofilm formation is thus a pivotal challenge for larger-scale development of membrane processes. Here, we studied the comparative antibacterial activities of different inorganic membranes (ceramic and zeolite-coated ceramic with or without copper exchange) using several bacterial strains (Escherichia coli, Staphylococcus aureus, and Bacillus subtilis). In static conditions, alumina plates coated with Cu-exchanged zeolite showed significant bactericidal activity. In dynamic mode (circulation of a contaminated nutrient medium), there was no observable bacterial adhesion at the surface of the Cu-exchanged material. These results confirm the antifouling properties of the Cu-mordenite layer due to both the increased hydrophilicity and antibacterial properties of the active layer.Tests performed with tubular filtration membranes (without copper exchange) showed a significant decline in membrane hydraulic properties during filtration of culture media containing bacteria, whereas copper-exchanged membranes showed no decline in hydraulic permeability. Filtration tests performed with concentrated culture media containing spores of B. subtilis led to a significant decrease in membrane hydraulic permeabilities (but less so with Cu-exchanged membranes). The surfaces showed less effective global antifouling properties during the filtration of a concentrated culture medium due to competition between bacterial growth and the bactericidal effect of copper. Analyses of copper leached in solution show that after a conditioning step, the amount of copper released is negligible.
