Evaluation of Carbon Source Selection and its Impacts on Performance of an Integrated Fixed Film Activated Sludge (IFAS) Solution for a Partial Denitrification-Anammox (PdNA) Process
Open AccessThis study compares three external carbon sources (fermentate, acetate, and methanol) used to drive partial denitrification-anammox (PdNA) process in a pilot-scale system designed to evaluate an integrated fixed film activated sludge or IFAS-PdNA application for use in mainstream nitrogen removal at Blue Plains Advanced Wastewater Treatment Plant (AWTP). The objectives of this study were to evaluate the performance of the pilot for each of the three carbon sources, determine operational guidelines, and assess cost and methanol savings over conventional biological nutrient removal process.A 360 L pilot system was operated for this study. This system was fed secondary effluent wastewater directly from the Blue Plains AWTP. The major components of the pilot system consisted sequentially of a nitrification zone, followed by a PdNA zone where anaerobic ammonia oxidizing bacteria (AnAOB or anammox) were retained as part of a complex microbial community on IFAS carriers, a full denitrification (FdN) zone for nitrate polishing, and a clarifier. During stable operation with fermentate as the carbon source, the pilot achieved 52.0±35.0% PdN efficiencies and 3.0±3.3 g TIN/d removal through the PdNA pathway. Acetate addition achieved 74.5±24.8% PdN efficiencies and 7.2±4.5 g TIN/d removal through the PdNA pathway, and methanol addition achieved 32.3±17.5% PdN efficiencies and 5.1±2.9 g TIN/d removal through the PdNA pathway. Average total nitrogen removal during each period was 26.0±11.1 g TIN/d, 32.8±7.4 g TIN/d, and 21.3±6.9 g TIN/d for fermentate, acetate and methanol, respectively. Biofilm thicknesses observed were significantly higher for fermentate, when compared to acetate or methanol. PdN efficiencies with methanol was lower than in previous studies and was dependent on improving the removal capacity of anammox. Potential methanol cost savings over conventional BNR were highest when using fermentate at 45%, and significant cost savings were also achieved with methanol, at 13%. Due to high unit costs, acetate showed a potential cost increase of 107%. Based on these results, fermentate was seen to be the most appropriate carbon source for driving PdNA at Blue Plains AWTP, with indications that it could be a viable carbon source for similar PdNA implementations elsewhere. Additional study is needed to evaluate process changes necessary to ensure less variability in fermentate quality and improve the consistency of the savings achieved.
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