Biofouling, which is the accumulation of microorganisms onto the membrane surface and on the feed spacer, is a very prominent problem in the use of reverse osmosis (RO) membranes. In the past, research and development of biofouling prevention has commonly focused on the pretreatment of the feed water, the improvement of cleaning solutions and procedures, and modifications to the membranes themselves. This research focuses on developing anti-biofouling polypropylene (PP) feed spacers. This is particularly significant because membrane replacement due to fouling is the single largest operating cost in water separation (Escobar et al. 2005).

PP was functionalized via the addition of a spacer arm with metal chelating ligands. These ligands were charged with copper or silver ions to allow for slow release of metals into the feed water in the membrane systems. Copper and silver ions have been previously used to disinfect water against microbial life because the ions interfere with enzymes involved in cellular respiration, and they bind DNA at specific sites. This functionalization was chosen as the focus because these chelating ligands are quite stable and easily synthesized, operate over a diverse range of conditions, have easily controlled binding affinities, and are well suited for model studies. In this research, the spacer arm was glycidyl methacrylate (GMA) which was polymerized to the PP using benzoyl peroxide as a radical initiator. Iminodiacetic acid (IDA) was then added to the end of the GMA spacer arm and to allow for the chelatation of the copper and silver ions.

Characterization of the PP modification was performed using Fourier transform infrared spectroscopic (FITR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and mechanical strength measurements. The effects on the biological content of water in the presence of the modified spacer were tested using a synthetic water matrix of sterile phosphate buffer solution containing Pseudomonas fluorescens P17 and Spirillium volutans strain NOX. Both modified and unmodified spacers were contacted with the feed water for 2 weeks to allow for growth and then placed in stomacher bags where the biofilm was removed. R2A Agar spread plates will then be made for each specimen and bacterial growth were quantified using a Model 920A Colony Counter.

References:

Escobar I., Hoek, E., Gabelich, C., F. DiGiano, Y. Le Gouellec, Berube, P., K. Howe, J. Allen, K. Atasi, M. Benjamin, P. Brandhuber, Brant, J.A., Chang, Y., Chapman, M., A. Childress, W. Conlon, T. Cooke, I. Crossley, G. Crozes, P. Huck, S. Kommineni, J. Jacangelo, A. Karimi, J. Kim, D. Lawler, Q. Li, L. Schideman, S. Sethi, J. Tobiason, T. Tseng, S. Veerapaneni, and A. Zander, “American Water Works Association Membrane Technology Research Committee Report: Membrane Fouling – Recent Advances and Research Needs”, Journal American Water Works Association, 97 (8), 2005, pages 79-89.