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<br /> <br />Bay Area Clean Water Agencies | City of San Leandro Final Report | 17 <br />6.2 Plant Upgrades to Meet Level 3 <br />The technology upgrades considered to meet the Level 3 discharge requirements are shown with <br />the process flow diagram presented in Figure 6-2. Level 3 upgrades would expand upon those listed <br />for Level 2. <br />In addition to those listed for Level 2, Level 3 upgrades requires an external carbon source chemical <br />feed facility, alum/polymer chemical feed facilities at newly constructed filters, a rapid <br />mix/flocculation tank upstream of the filters, and new filters for nitrogen and phosphorus removal. <br />The external carbon source is provided to meet the carbon requirements for meeting the TN <br />discharge target. The chemical feed facilities and the rapid mix/flocculation step prior to the filters is <br />in place to remove solids loading associated with chemical precipitation upstream of the filters. The <br />additional chemical feed facilities would operate on a daily basis to meet the TP discharge target. <br />6.3 Facility Needs to Meet Level 2 and 3 <br />A list of the facility needs to meet the Level 2 and 3 effluent limits are provided in Table 6-1. Aerial <br />layouts for the key Level 2 and 3 facilities during both dry season and year round are shown in <br />Figure 6-1 and Figure 6-2, respectively. <br />Table 6-1. Facility Needs Overview for Level 2 and 3 Plant Upgrades <br />Treatment Level 2 Level 3 <br />Primary Implement chemically enhanced primary <br />treatment (CEPT): <br />· Add metal salt chemical feed facilities <br />· Add polymer chemical feed facilities <br />Same as Level 2 <br />Biological · Parallel MBR <br />· Retrofit the aeration basins to operate <br />as a BNR reactor to achieve <br />ammonia/total nitrogen/total phosphorus <br />load reduction <br />Same as Level 2, plus: <br />· External Carbon Source Chemical Feed <br />Facility for MBR <br />Tertiary -- · Denitrification and phosphorus removal <br />filters to reduce load from the parallel <br />MBR facilities <br />· Add an external carbon source chemical <br />feed facilities <br />· Add a metal salt chemical feed facilities