AWWA MTC57675

This paper presents a review of the major components of membrane systems with a view toward evaluating the operation and maintenance (O&M) impacts. Beginning with an initial assessment of raw water quality and desired finished water quality, the selection between RO vs. NF will be evaluated considering both capital and O&M implications based on raw water blend options and feed pressure differences. Specific components within the membrane system will be addressed including pre-treatment, physical and chemical; membrane selection, square footage and physical configurations; high pressure pump type, and pump and motor efficiencies; use of variable frequency drives on high pressure pumps; and general materials of construction and valve selection. The importance of proper hydraulic design and flow balancing will be discussed, with particular emphasis on the application of new multi-port vessels and their impact on the O&M of a plant. Misapplication of this new development in the membrane industry can significantly affect the life-cycle cost of a plant through several means including increased high pressure pumping energy and shortened membrane life as a result of inadequate cleaning access. Other topics will be addressed including energy recovery and instrumentation and controls issues. Finally, the paper includes a brief discussion on alternative procurement methods for obtaining a system designed to provide the user with the lowest life cycle cost membrane plant. Specific information developed from the authors' personal experience in the industry is incorporated in the discussions. Includes 5 references, table.