Much of the current emphasis in the use of semi-permeable membranes for wastewaterreclamation has been placed on the establishment of appropriate water quality standards, and the ability ofmembrane systems to meet these standards for various high level uses such as indirect potable reuse andindustrial process water. Water quality issues are important as they provide potential reclaimed watercustomers the information needed to determine the acceptability of the product water. This emphasis onwater quality standards, however, tends to overshadow the equally important technical design issues thatestablish the feasibility and economic viability of wastewater reclamation projects.A number of significant technical issues must be addressed in the design of membrane processes forwastewater reclamation. The design directions chosen to address these issues often have significantimpacts on the feasibility and economic viability of the facility. This paper discusses some of thesetechnical issues and provides examples of how design choices impact facility capital and operating costs.Information developed during the design of the 100,000 m3 /day (26.4 million gallons per day) water reclamation plant,which will use reverse osmosis (RO) membranes to reclaim municipal secondary effluent to produce anindustrial water supply, is used to illustrate these issues. Includes 24 references, tables, figure.