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<br /> <br />Bay Area Clean Water Agencies | City of San Leandro Final Report | 9 <br /> Unit total present value cost per gallon ($/gpd) includes the present value capital and O&M costs <br />for the treatment strategy to remove ammonia, nitrogen and phosphorus. <br /> Unit cost for TN and TP reductions ($ per pound nutrient removed) include both capital and O&M <br />costs for the life of the project. <br /> Unit costs for TN reduction were estimated based only on the cost elements that contribute <br />to TN removal. <br /> Unit costs for phosphorus reduction were estimated based on the cost elements needed to <br />remove phosphorus. <br />The nutrient reduction is calculated based on the average removal over the life cycle period. The unit <br />cost calculation is then based on the total present value (capital and O&M average over the project <br />duration) divided by the average nutrient load reduction over the period. Table 3-4 shows the <br />discount rate and period used for the different scenarios. <br />Table 3-4. Assumptions for Life Cycle Analysis <br />Scenario Discount Rate Period (yr) <br />Optimization 2% 10 <br />Side Stream Treatment 2% 30 <br />Level 2 2% 30 <br />Level 3 2% 30 <br /> <br />4 Nutrient Load Reduction by Optimization <br />This section describes the optimization strategies that were considered, and presents the effluent <br />nutrient load and estimated costs for the recommended strategy. <br />Five optimization strategies were identified during the SLWPCP site visit. These were analyzed <br />following the site visit to screen and select the most attractive strategy. In some cases, strategies <br />were combined into one overall strategy to reduce both nitrogen and phosphorus effluent loads. The <br />five optimization strategies were screened down to four strategies as follows. <br /> <br /> Optimization Strategy 1: Modify the primary clarifiers to operate as chemically enhanced primary <br />treatment (CEPT) by adding ferric chloride and polymer. <br /> Is it feasible? Yes <br /> Potential impact on ability to reduce nutrient discharge loads? Remove phosphorus in <br />the primaries and reduce overall loadings to downstream biological processes. <br /> Result from analysis: It will remove phosphorus at the primaries and increase downstream <br />capacity. The phosphorus load reduction is limited to the wet season as the facility is already <br />removing phosphorus during the dry. It has the potential to remove more carbon than desired <br />for future total nitrogen removal (if required in the future). <br /> Recommendation: Carry forward. <br /> <br /> Optimization Strategy 2: Baseload flows to the fixed film reactors (FFRs) for nitrification <br /> Is it feasible? Yes