Performance analysis of a denitrifying wastewater treatment plant

Abstract

The cleaning performance of an activated sludge wastewater treatment plant for biological nitrogen removal was evaluated based on the Activated Sludge Models No. 1 (ASM1) and No. 3 (ASM3). The COST predenitrification benchmark plant was considered as a case study. Several treatment plant performance indexes were defined based on performance indicators and operating cost factors. Plant operation was evaluated for three dynamic disturbance scenarios corresponding to dry, rain, and storm weather conditions. The aeration rate was seen to be the most sensitive process parameter for this case study, and the nitrate recycle flow rate ratio was the least sensitive of all parameters analyzed. Different qualitative predictions were obtained from the two models, as a result of different model structures. For all three weather scenarios, the sludge production predicted by the ASM1 model increases slightly as the oxygen transfer rate increases; in contrast, the sludge production decreases for the ASM3 model. However, the resulting difference in the sludge treatment cost does not qualitatively modify the cost performance index profile. For all control handles considered the rain weather scenario showed the highest cost performance index and the lowest global cleaning efficiency.