Stepfeed Biological Nutrient Removal: Design and Operating Experience, Proceedings
- • Crawford, G.V, M. D. Elliot, S. Black, G. Daigger, D. Stafford
- FLORIDA WATER RESOURCES JOURNAL
treatment plants for biological nutrient removal (BNR) has become widespread, process variations such as step-feed BNR have been developed to adapt existing treatment facilities to meet effluent requirements. Since there are relatively few full-scale installations of step-feed BNR, the process and retrofit design concepts are still under development. Although step-feed BNR has a relatively small footprint for a suspendedgrowth process, it also is more complex than plug-flow or complete-mix regimes, and presents unique challenges to the designer. This article discusses major design components, including primary effluent flow splitting, chemical feed, dissolved oxygen carryover, nitrate recycle, and foam control. It also illustrates the impact of these design components on performance through process modeling examples and shows how they are being resolved in New York City and Cumberland, Maryland.