The Irvine Ranch Water District (IWRD) is evaluating alternate technologies to be used to treat various types of water for potable and nonpotable use. The technology of microfiltration has advanced significantly in recent years and has proven to be effective in treating coagulated waters, secondary treated wastewater effluents, and algae laden effluents. The IRWD desires to investigate the application of microfiltration technology for the following water sources: colored groundwater; Michelson Wastewater Reclamation Plant (MWRP); Sand Canyon Reservoir; and Santiago Reservoir. The main objective of this project is to conduct pilot studies and collect operations and water quality information to determine the effectiveness of microfiltration on the above sources. This project has been divided into two phases. Phase I, a preliminary screening study performed for a limited number of days at each site, is complete. Phase II is a more extensive pilot program to test promising applications identified during Phase I and to develop design criteria for full scale facilities. The microfiltration process consists of filtering water through hollow membrane fibers. As water flows through each membrane fiber, particulate matter is retained on the surface and the treated water flows through the membrane.