Testing the Waters - Piloting High Rate Treatment Technologies for Secondary Treatment and Total Nitrogen Removal Process Selection

The City of Portsmouth, New Hampshire conducted a side by side pilot study to evaluate high rate treatment technologies for secondary and total nitrogen removal down to 3 mg/l to upgrade their advanced primary treatment plant. The technologies piloted were: Biological Aerated Filter (BAF), Conventional Activated Sludge with BioMag (CAS-BioMag), and Moving Bed Bioreactor with Dissolved Air Flotation (MBBR-DAF). The piloting was also used to verify the vendor provided loading rates and to assess the performance of the technologies under and after conditions of hydraulic stress. All technologies were able to meet the target effluent limit goals. A life cycle cost comparison of the technologies at full scale was conducted. Based on the level of detail the technologies were approximately the same cost. As a result, the process selection decision came down to more subjective evaluation criteria and a cost/value ratio evaluation. Ultimately BAF was the recommended technology for Portsmouth.