10B Action 2019 0506 - Laserfiche WebLink

Home

2 | Final Report Bay Area Clean Water Agencies | City of San Leandro The recommended optimization strategy to reduce nutrient loads in the plant effluent includes: 1. Implement chemically enhanced primary treatment (CEPT) to the primary clarifiers by adding metal salt and polymer chemical feed facilities. 2. Add alkalinity to the aeration basins (required for nitrification). 3. Operate the aeration basins in series to control solids distribution issues and facilitate nitrification. Additionally, the basins in series will operate in step feed mode to reduce solids loading on the secondary clarifiers and facilitate total nitrogen removal. 4. Add a blower to meet the additional demand associated with nitrification. The SLWPCP is considered a candidate for sidestream treatment to reduce nitrogen loads as the plant anaerobically digests biosolids and dewaters to produce a return sidestream laden with nitrogen. The recommended sidestream treatment strategy is deammonification for reducing ammonia/nitrogen loads. The plant is also a candidate for sidestream treatment to reduce phosphorus loads by adding a metal salt upstream of the mechanical dewatering. The upgrade strategies to achieve Levels 2 and 3 for the entire plant flow include: 1. Level 2 (15 mg TN-N/L and 1 mg TP-P/L): a. Implement chemically enhanced primary treatment (CEPT) to the primary clarifiers by adding metal salt and polymer chemical feed facilities. b. Add a parallel MBR treatment train. c. Retrofit the aeration basins to operate as a biological nutrient removal (BNR) reactor to remove ammonia/total nitrogen/total phosphorus. 2. Level 3 (6 mg TN-N/L and 0.3 mg TP-P/L) a. Same as Level 2, plus: b. Add filters for denitrification and phosphorus removal. c. Add chemical feed facilities for an external carbon source to trim nitrogen at the MBR and denite filters. d. Add chemical feed facilities for metal salt addition for phosphorus removal. As shown in Table ES-1, and as might be expected, the costs generally increase from optimization to sidestream treatment, and again to Level 2 and Level 3 upgrades, respectively. The costs generally increase for both capital and O&M from the dry season to year round. Overall the present value costs range from $14 Mil for dry season optimization up to $135 Mil for Level 3 year round upgrades. In addition to costs, the relative increase in greenhouse (GHG) emissions was also evaluated. In general, the GHG emissions showed an increase as the level of treatment increases.