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Protocol to Evaluate Alternative External Carbon Sources for Denitrification at Full-Scale Wastewater Treatment Plants

April Z. Gu

120 pages
IWA Publishing
Addition of external carbon to biological nutrient removal processes to enhance denitrification to meet more stringent effluent nitrogen limits (e.g., total nitrogen < 3 to 6 mg/L) has become more common for publicly owned treatment works. The objective of this report is to establish a framework for a comprehensive and practice-orientated standardized methodology and a procedure to assess the efficiency and feasibility of an alternative carbon source for enhancing nitrogen removal at full-scale wastewater treatment facilities. The report includes a comprehensive literature review that summarizes various types of external carbon sources that can be applied for supporting denitrification. The summary included denitrification kinetics rates and coefficients. A road map is developed that depicts the overall framework and identifies the key components required for a comprehensive and systematic assessment of an alternative carbon source for denitrification. A procedure for pre-screening carbon alternatives is established and an evaluation matrix is provided. 

The document presents a list of basic parameters that should be obtained or measured to determine the potential of a carbon source. These parameters are often available from the supplier. These basic parameters are used to determine the carbon-to-nitrogen demand ratio and process performance monitoring varies for field testing different nitrogen removal processes. Therefore, the guidance document first provides protocols for evaluating denitrification performance in a general anoxic denitrification reactor. Then, more configuration-specific examples are given for the most commonly used denitrification processes, including the modified Ludzack–Ettinger (MLE) process and 4-stage Bardenpho, either as a suspended-growth system or a fixed-film system. The final selection of the external carbon source is based on a combination of literature review information, bench test parameters, and full-scale testing results.