How short should the SRT be? – Investigation of parallel vs series C- and N-removal processes at the Blue Plains AWTP

There are well acknowledged benefits from up-stream high-rate C- and consecutive N-removal processes with reduced volume- and aeration requirements. At large 2-stage plants like Blue Plains AWTP, the 2nd dimension of having parallel trains opens up the opportunity to shift loads from one high-rate activated sludge (HRAS) train to the other. The load shift promotes biosorption on the relatively higly-loaded side and allows for achieving minimum sludge retention time (SRT) required for nitrification on the relatively lightly-loaded side by utilizing bioaugmentation from the N-removal stage. A full-plant model has been calibrated to operational data before and after start-up of the new anaerobic digestion system. Then 2 future optimization scenarios for resource recovery have been evaluated predicting 18% in methanol reduction and 6% in biogas increase.