Previously, the analysis of energy demand for wastewater treatment was often limited to one-dimensional analyses of electricity demand. How ever, a comprehensive analysis requires the inclusion of all different contributions to energy demand. The Life Cycle Assessment (LCA) methodology defined in ISO 14040/44 is a suitable tool for this task. With it, all different primary and secondary energy demands can be quantified and assessed using consistent indicators, complemented by an assessment of other environmental impacts such as the carbon footprint.