285432 Assessment of Hydrophilic and Antimicrobial Surface Modifications for Biofouling Control
Biofouling represents a major limitation in the use of membranes for water purification. Biofilms are notoriously difficult to prevent or to eliminate. Chlorination has been successfully used to control microbial growth, but chlorine’s deleterious effects on some membranes forces costly de-chlorination before membrane treatment and re-chlorination before end use. The use of biocides and cleaning protocols for biofouling control may be reduced by membranes resistant to biofouling. This work evaluated the effect of several surface modifications on biofouling susceptibility of membranes and feed spacers. Polydopamine, a hydrophilic surface modification agent which can be deposited on nearly any substrate from aqueous dopamine solution, has recently been used to reduce organic fouling on many membranes. Polydopamine has also been used as a platform for conjugation of amine-terminated molecules, such as poly(ethylene glycol) monoamine. Poly(ethylene glycol) has a long history as an anti-fouling material in the membrane and biomedical fields. Copper coatings reportedly have antimicrobial effects and “anti-biofouling” feed spacers are currently available from some membrane manufacturers. Polydopamine and polydopamine-g-poly(ethylene glycol) coatings were applied to commercial polysulfone ultrafiltration membranes and polypropylene feed spacers. Copper coatings were applied to a polypropylene feed spacers and a commercial anti-biofouling feed spacer was also used.
Many biofouling studies reported in the literature consist of experiments which are very short term and/or are carried out under conditions not relevant to the operation of industrial membrane modules. Consequently, many anti-fouling strategies have been reported as effective in the academic literature while biofouling remains a significant hurdle in industrial applications. Modified membranes and feed spacers were tested for short-term, static bacterial adhesion and for longer-term biofilm development under realistic membrane module flow conditions. Membrane fouling simulators, containing membranes and feed spacers, have been developed which mimic the hydrodynamic conditions of full-size modules. This study showed that short-term, static adhesion tests are not predictive of ultimate biofouling potential and that the anti-fouling surface modifications employed here are insufficient for biofouling control/prevention. Reasons for the discrepancy between the short-term and long-term testing protocols will be discussed.