| The main objective of the drinking water industry is to ensure the production and distribution of safe drinking water to all its consumers, which primarily entails the inactivation of pathogenic microorganisms and removal of toxic and carcinogenic compounds. Nanofiltration (NF) membranes serve these two purposes, removing pathogens and natural organic matter that may react with disinfectants to form carcinogenic by-products, from natural waters.; Productivity losses due to membrane biofouling are one of the main impediments to a more widespread use of this technology for drinking water production. Biofouling minimization requires understanding of the fundamentals of biofilm development in environments that are common to water treatment. It is also necessary to develop monitoring techniques that could detect early stages of biofouling, in-situ, real-time and non-invasively, and trigger early counter measures, minimizing irreversible fouling occurrence.; The two main goals of this research were to better understand what biological factors govern the biofouling of NF membranes, and to evaluate the potential for ultrasonic techniques to monitor biofilm occurrence.; Extra-cellular polysaccharides (EPS), microbial cells, and selected metal ions were isolated to observe their influence on the flux decline of nanofiltration (NF) systems, using recalcitrant and readily degradable carbon sources (natural organic matter (NOM), acetate and glucose). In addition, the fouling potential of soluble microbial by-products (SMP) and NOM was compared under similar experimental conditions.; A novel, non-invasive technique using ultrasonic frequency-domain reflectometry (UFDR), was used to detect biofilm development of Pseudomonas aeruginosa on NF polyamide membrane surfaces and polycarbonate slides surfaces. Biofilm growth was monitored by its acoustic reflection behavior and differences were obtained between the signals of fouled membranes, as compared with those same surfaces prior to biofilm development. Increasing amounts of exocellular polysaccharides bound to surfaces resulted in significant decreases in reflection amplitude. |
