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To the Reader: An Introduction to Report <br />This report is part of the response to the Regional Watershed Permit requirements. This report <br />presents the results of the plant assessment and opportunities for nutrient reductions due to <br />optimization and upgrades as well as the associated costs for nutrient removal. It is based on the <br />findings of the site visit and the site visit report completed in 2015. It is important to note that the <br />technologies identified in this evaluation for sidestream treatment and plant upgrades are meant to <br />serve as placeholders to understand potential site requirements and costs, should they be needed. It <br />is anticipated that each agency would do additional planning to refine recommended projects prior to <br />implementation. <br />Regional Watershed Permit Overview: <br />Nutrients in the San Francisco Bay (SF Bay) are a growing concern for the Bay Area water quality <br />community. Historically, the SF Bay has not been adversely impacted by nutrient loading, although <br />there are indications that its historic resilience to the effects of nutrient enrichment may be <br />weakening.1,2 While the definition of impairment has not been reached, there is concern that the SF <br />Bay has reached a tipping point that might lead to impairment. Numerous scientific studies are being <br />conducted to understand the impact of nutrients on the SF Bay. As a result, it may be necessary to <br />limit the availability of essential nutrients, by implementing some form of nutrient removal to address <br />three potential challenges: <br />1. Ammonia toxicity and/or inhibition of phytoplankton growth. Full or partial nitrification may be <br />required. <br />2. Eutrophication. Denitrification may be required where total inorganic nitrogen is the limiting <br />nutrient. <br />3. Undesirable phytoplankton assemblage changes due to the ratio of nitrogen to phosphorus. <br />Phosphorus reduction may be required. <br />On April 9, 2014, the Water Board issued Order No. R2-2014-0014, Waste Discharge Requirements <br />for Nutrients from Municipal Wastewater Discharges to San Francisco Bay (Watershed Permit). The <br />Watershed Permit sets forth a regional framework to facilitate collaboration on studies that will inform <br />future management decisions and regulatory strategies. The permit includes four key elements for <br />evaluating nutrient load reduction opportunities at POTWs (if supported by sound science): <br />1. Plant optimization <br />2. Sidestream treatment <br />3. Plant upgrades <br />4. Nutrient reduction by other means (including source control, natural treatment systems, <br />diversion of effluent to water recycling, and others) <br /> <br />1 Cloern, J.E. and Jassby, A.D. (2012) Drivers of change in estuarine-coastal ecosystems: Discoveries <br />from four decades of study in San Francisco Bay. Reviews of Geophysics, 50, RG4001, page 21. <br />2 San Francisco Estuary Institute (SFEI) (2013) Nutrient Conceptual Model Draft, May 1, 2013, page 14. <br />San Francisco Estuary Institute, Richmond, CA.