SFPUC Algae Monitoring and Mitigation Plan

Trussell recently supported an effort to update San Francisco Public Utilities Commission’s (SFPUC’s) Algae Monitoring and Mitigation Plan. The plan considers all aspects of algal bloom monitoring and mitigation, including (1) reservoir management to avoid algae growth, (2) system monitoring to track bloom development and inform treatment plant operations, and (3) response strategies at the water treatment plants to ensure sustained production of safe and aesthetically pleasing drinking water. Trussell led the effort to update the plan as it relates to SFPUC’s treatment plant operations and monitoring, and Stillwater Sciences focused on reservoir monitoring and mitigation.

Algal blooms in drinking water reservoirs can cause numerous treatment issues ranging from nuisance problems (e.g., taste and odor (T&O) complaints from geosmin) to severe water quality issues (e.g., ‘do not drink, do not boil’ announcements caused by algal toxins found in finished water). Although SFPUC has rare T&O complaints and has never detected toxins in their drinking water, the focus of the plan is to be well informed and prepared to respond to all potential issues associated with algae in their reservoirs.

Trussell investigated important aspects of treating raw water impacted by algae including (a) an evaluation of algae’s impact on coagulation, sedimentation, pre-chlorination, ozonation, and filter performance (b) monitoring and responding to detection of T&O compounds in raw water, (c) treatment strategies for when raw water has elevated total organic carbon (TOC), and (d) response strategies and treatment targets for responding to a detection of algal toxins. These investigations were conducted via jar testing, literature reviews, and analysis of historical plant performance.

Trussell has also provided SFPUC with technical memoranda summarizing extensive literature reviews regarding treatment of waters with elevated TOC, monitoring methods for detecting T&O compounds before they cause customer complaints, and detailed recommendations for responding to algal blooms of diatoms and cyanobacteria (blue-green algae) at the water treatment plants. These technical memoranda have been combined with results from the jar testing to give a thorough and informed update to SFPUC’s Algae Monitoring and Mitigation Plan.