(715d) Anti-Adhesive Properties of Polysulfone Membranes Modified with PAA/PAH Polyelectrolyte Multilayers

Microfiltration (MF) membranes are increasingly used in drinking water treatment and wastewater reuse because of their effectiveness in removing waterborne pathogens (e.g., bacteria, viruses, and protozoa cysts). However, due to the ubiquity of microorganisms in influent waters, MF processes are often hindered by biofouling which reduces clean water production, shortens membrane lifespan, and increases energy demands. To overcome these limitations, we investigate  the surface modification of polymeric MF membranes with the use of polyeletrolyte multilayers (PEMs) in order to enhance their resistance to biofouling. Specifically, commercially available polysulfone (PS) membranes are modified with poly(allylamine hydrochloride) (PAH) / polyacrylic acid (PAA) multilayers in order to enhance the membranes’ resistance to bacterial adhesion (E. coli MG1655). The properties of the modified membrane surface are characterized by using ATR-FTIR, XPS, AFM, and SEM. Crossflow membrane filtration experiments are conducted with E. coli suspensions prepared at pH 7.1 and 10 mM NaCl.  By using a fluorescent microscope, the deposition of the fluorescent E. coli cells can be observed through a window on top of the membrane housing in real time. The images of deposited bacteria on the membrane surface are taken using a digital camera at equal time intervals throughout the entire deposition process. The initial bacterial deposition rate (first 30 min) is obtained by enumerating the deposited bacteria as a function of time. The reversibility of bacterial attachment is also investigated by flushing the deposited bacteria using the same background solution at an elevated crossflow velocity and zero transmembrane pressure. The effects of PEMs modification are determined by comparing both the bacterial deposition kinetics and the degree of bacterial release from the modified membranes with those of the original membrane. In addition, the influence of the number of bilayers within the PEMs on the membrane hydraulic resistance and anti-adhesive properties is investigated.