Biofouling suppression of modified feed spacers: Localized and long-distance antibacterial activity

Biofouling hindering activity of two modified feed spacers was assessed. A 'short-distance' modification was attained by covalently binding polymeric quaternary ammonium groups (pQAs) to the spacer by atom transfer radical polymerization (ATRP). A 'long-distance' modification was based on embedding silver nanoparticles (nAg) in the polymeric spacer by sonochemical deposition. Cross-flow experiments in planar-membrane filtration cells using ultrafiltration membranes exposed to a mixed microbial enrichment were performed at conditions simulating spiral wound modules (0.15 m.s(-1) channel flow velocity). Physical properties of the modified spacers were evaluated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Microscopic analysis of the membranes adjacent to the modified spacers indicated the presence of a sporadic monolayer structure compared to a developed biofilm in the untreated spacers. SEM imaging and total organic carbon analysis of the attached layer revealed a low number of bacteria near the modified spacers and adjacent membranes. Both modified spacers displayed improved permeate fluxes compared to the control. nAg modified spacers displayed a somewhat steadier permeate flux profile within the length of the experiments probably due to the release of antibacterial active species. pQA modified spacers are assumed to have a more localized influence by direct contact on their surface. (C) 2015 Elsevier B.V. All rights reserved.