AWWA ACE63254

This slide presentation outlines a project of oxygenating the Upper San Leandro (USL) Reservoir. Taste and odors from Anabaena producing Geosmin levels several times above design capacity of ozone feed system were a problem. A 1997 study determined excessive nutrients as the cause of Anabaena blooms, and recommended hypolimnetic oxygenation to reduce internally-generated nutrients. The study also recommended destratification during spring season after heavy runoff years to reduce externally imported nutrients. A summary of the project concluded that: hypolimnetic oxygen feed for USL Reservoir required 3 tons/day after initial demand (0.2 mg/l/day); to distribute the oxygen evenly, higher rates for shorter periods appear to facilitate mixing; the treatment plant experienced lower ozone demand, as much as 50%; manganese levels also decreased, but to a lesser extent; algae composition changed from blue-green to dinoflagellates, requiring pre-chlorination; induced mixing and lower oxygen feed resulted in fewer dinoflagellates and more diatoms. Includes figures.