A series of energy optimization options (EOOs) were identified for the Ejby Molle WWTP through the analysis of historical operational data, the use of an advanced mass/energy balance simulation tool, and the adoption of a collaborative workshop-based approach in identifying and evaluating alternatives. This biological nutrient removal facility is located in Odense, Denmark, and has a treatment capacity suitable for 385.000 population equivalents. Implementation by plant staff of some of the recommended EOOs (primarily those only requiring modifications in operational strategies of existing unit processes) has succeeded in making this plant energy self-sufficient. Efforts are currently on their way for the incorporation of a deammonification-based process for side stream treatment with the objective of eventually converting it to a mainstream system. These modifications will take this plant well into a positive net energy condition.