Primary Sludge Fermenters in BNR Plants: Are they Cost-Effective for Meeting Effluent Phosphorus Limits?
Abstract:The 100 ML/d Pine Creek WWTP is a state-of-the-art BNR facility that serves the City of Calgary, Alberta. A delay in the construction of the primary sludge fermenters allowed a comparison of the performance of the BNR process with and without fermentation for extended periods of time, and facilitated a life-cycle cost analysis in which the cost of primary sludge fermentation was compared with alternative forms of primary sludge thickening and meeting the effluent total P limit by chemical addition. Data from the first 20 months of plant operation indicated that, with primary sludge fermentation, the plant is capable of reliably meeting its stringent effluent total P target of <0.3 mg/L. Without fermentation, the plant required the in-plant addition for approximately 50 mg/L of alum to meet this same effluent quality standard. The life-cycle cost comparison between primary sludge fermentation and enhanced biological phosphorus removal (EBPR), and two alternative forms of primary sludge thickening and chemical P removal, indicated that primary sludge fermentation is a cost-effective method of reliably meeting a stringent effluent total P standard. Using a 20-year net present value (NPV) analysis, xprimary sludge fermentation was found to be approximately 8 percent cheaper than mechanical primary sludge thickening and chemical P removal, and 22 percent cheaper than gravity thickening of primary sludge and chemical P removal.
Document Type: Research Article
Publication date: January 1, 2010
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