A Dissertation submitted to the Graduate School of Engineering HIROSHIMA UNIVERSITY By CERVINIA VELASCO MANALO In partial fulfillment of the requirements for the degree of Doctor of Engineering March 2016 Evaluation of Biofouling and Its Control by Hypochlorite on Polyamide Reverse Osmosis Membranes ( RO ) Cervinia V. Manalo The following people and organizations had been invaluable towards the completion of this doctorate degree and during the course of this academic journey, and for that I would like to express my sincerest and heartfelt gratitude: My professors and mentors from the Green Process Engineering Laboratory: Dr. Wataru Nishijima for his guidance and immense knowledge during the time of my research and for his valuable insights and efforts during the preparation of my papers; Dr. Satoshi Nakai, my adviser, for all the constructive opinions and advices, for his significant support during my applications for scholarship grants, and for his constant push in making me accomplish and finish this degree on time; Dr. Tetsuji Okuda for all his help during my application as a researcher and as a graduate student, for his continued guidance during my experiments and research, for ensuring my financial support as a part-time research assistant (RA) during my stay here in Japan, and for his care and kindness; My review committee, Dr. Toshinori Tsuru, Dr. Tomohisa Yoshioka, and Dr. Wataru Nishijima for their challenging questions and insightful comments that helped me write a better dissertation, for the constant encouragements, and for rendering their time and support despite the time constraints during my preliminary and final defense; CREST (Core Research for Evolutionary Science and Technology) under the project "Development of ROBUST reverse osmosis (RO)/nanofiltration (NF) membranes for various types of water sources and the Department of Chemical Engineering for the financial support given to me as a part-time RA, which enabled me to pursue my studies while living in Saijo;The scholarship grants awarded by Higashi-Hiroshima International Soroptomist

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A novel method was proposed to determine biofouling potential by direct analysis of a reverse osmosis (RO) membrane through fluorescence intensity analysis of biofilm formed on the membrane surface, thereby incorporating fouling tendencies of both feedwater and membrane. Evaluation of the biofouling potential on the RO membrane was done by accelerated biofilm formation through soaking of membranes in high biofouling potential waters obtained by adding microorganisms and glucose in test waters. The biofilm formed on the soaked membrane was quantified by fluorescence intensity microplate analysis. The soaking method's capability in detecting biofilm formation was confirmed when percentage coverage obtained through fluorescence microscopy and intensity values exhibited a linear correlation (R(2) = 0.96). Continuous cross-flow experiments confirmed the ability and reliability of the soaking method in giving biofouling potential on RO membranes when a good correlation (R(2) = 0.87) between intensity values of biofilms formed on the membrane during soaking and filtration conditions was obtained. Applicability of the test developed was shown when three commercially available polyamide (PA) RO membranes were assessed for biofouling potential. This new method can also be applied for the determination of biofouling potential in water with more than 3.6 mg L(-1) easily degradable organic carbon.

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