Control of membrane biofouling by silver nanoparticles using Pseudomonas aeruginosa as a model bacterium

Biofouling in water systems results in energy loss and potential contamination. In membrane treatments in particular, it often causes flux decline and increases tolerance to cleaning procedures. The effects of exposing bacterial cells to silver nanoparticles on their attachment in the initial stage of biofilm formation and on moderating biofouling buildup in an ultrafiltration membrane apparatus were studied. A high throughput screening method was used for assessing initial bacterial attachment and biofilm formation for P. aeruginosa cells exposed to 39 mu g/mL of Ag-NPs and compared to non-exposed cells, incubated for 2-48 h. Results showed that Ag-NPs steadily retarded biofilm formation, compared to control cells, where the attached biomass increased over incubation time. To elucidate the influence of Ag-NPs on biofouling buildup in an UF apparatus, two procedures were examined: (a) cells, pre-exposed to Ag-NPs were filtered through a membrane prior to sequential filtration of growth medium, and (b) suspension of cells and growth medium were filtered through a membrane in the presence or absence of Ag-NPs. Exposed samples in both procedures resulted in lower flux decline compared to respective controls. Scanning electron micrographs of post-filtered membranes showed a biofilm layer on the control membrane and scattered individual cells on Ag-NP-exposed membrane.