Biofouling prevention using silver nanoparticle impregnated polyethersulfone (PES) membrane: E. coli cell-killing in a continuous cross-flow membrane module

Biofouling significantly decreases membrane performance. So silver nanoparticle (Ag-NP) was impregnated selectively on a sulfonated polyethersulfone (SPES) membrane and its efficacy was tested in a continuous, cross-flow membrane module. The main challenges are: (i) to prevent biofouling on the membrane surface, (ii) achieve zero bacterial cell (E. coli) count in the permeate water, (iii) maintain Ag concentration in the permeate stream within the permissible limit of drinking water and (iv) maintain a high tensile strength of the membrane to prevent mechanical failure. Addressing these factors would ensure a long and productive service-life of the membrane. To this end, 10(4) CFU/ml of E. coli cell suspension was passed through the Ag-SPES membrane of 150 mu m total thickness, which has a narrow (1.74 mu m thickness), upper surface of Ag-NPs. We achieved zero E. coli cell-count and a minimum (10 mu g/L) Ag concentration in the permeate stream; simultaneously increasing the tensile strength from 2.78 MPa to 3.92 MPa due to Ag-NP impregnation. Thus, for a continuous inlet flow of E. coli contaminated water, the membrane module could deliver an almost constant permeate flow rate of 3.45 L per hour, due to complete E. coil cell-killing. Simultaneously, Ag concentration in permeate stream is well below the WHO's recommended limit of 100 mu g/L, for potable quality water. Therefore, the Ag-SPES, membrane can be used as an anti-biofouling membrane in a continuous operational mode. (C) 2016 Elsevier Inc. All rights reserved