Abstract The City and County of San Francisco mandated in 1991 maximum utilization of reclaimed water as a means of augmenting its water supply. A Master Plan is currently being developed that will implement a Water Reclamation Program. Potential users of over 27 mgd (100,000 m 3/d) of reclaimed water have been identified. These include industrial users, toilet flushing, decorative fountains, irrigation and landscaping. Almost all of these uses require reclaimed water that meets the most stringent wastewater reclamation criteria. This is true for the single largest potential use (53,000 m 3/d) which is the irrigation of parks, golf courses, and other open areas.