The surplus of nutrients in surface waters due to anthropogenic influences makes eutrophication an important issue in water quality in Europe. According to the Water Framework Directive of the European Union (EU-WFD) an improvement of all water bodies to a “good ecological status” is aimed. One aspect for achieving the goal is an additional reduction of nutrient immissions. In particular, the study has a focus on advanced nitrogen removal at large scale wastewater treatment plants (WWTP) in the area of Berlin and Brandenburg, Germany. A comprehensive life cycle assessment (LCA) of a generic WWTP with 1.47 million population equivalent (pe) is carried out. The WWTP includes a secondary treatment with upstream denitrification. Sludge treatment is realized by anaerobic digestion with biogas utilization and sludge disposal in a mono-incineration plant. On basis of the generic WWTP, five scenarios for an advanced nitrogen removal are analyzed and compared within the LCA: an expansion of the denitrification reactor (ExpDeni), a retrofit to a step-feed nitrogen removal (SFNR), a biologically active filtration (BAF) as post-treatment step as well as two processes for sludge liquor treatment by deammonification (Anammox) and by an SBR-reactor (SBR). Data for energy and chemical demand, effluent quality and infrastructure are based on an existing plant from Berlin and data of nitrogen removal processes on simulations and planning data for this particular WWTP. For the life cycle impact assessment, the following categories are considered: global warming potential (GWP), acidification potential (AP), marine (MEP) and freshwater eutrophication (FEP) as well as human (HTP) and freshwater ecotoxicity (FETP). Additional, the cumulative energy demand (CED) of fossil and nuclear energy resources is taken into account. For the generic WWTP two results have to be emphasized: the influence of high energy demand on potential environmental impacts and the relevance of the primary function of nutrient removal due to a high influence in eutrophication impact categories MEP and FEP. Hence, reducing electricity demand and an increased use of renewable energy resources will lead to reduced impacts. Comparing the nitrogen removal processes, SFNR is preferable to ExpDeni because of reduced energy demand (SFNR: -6%, ExpDeni: +9%) which leads to an improved environmental profile throughout all categories. Focusing on sludge liquor processes, Anammox may be recommended due to mainly lower additional impacts to SBR-process. Main issues at SBR are the high energy consumption (almost twice as high as energy demand of Anammox) and addition of methanol as carbon source. The BAF has the highest impacts in CED (+33%) and GWP (+14%) due to high energy demand for pumping and backwashing (+5%) and methanol dosing. However, favorable side-effects such as a reduction of phosphorus and heavy metal loads lead to a significant reduction in FEP (-18%) and FETP (-9%). All in all, SFNR is recommended in an overall comparison, Anammox has the second best environmental profile. BAF can be recommended if other effects in wastewater treatment are aimed at. Due to lack of data concerning trace organics, uncertainties in toxicity potential are still apparent. Besides, uncertainties in estimating N2O-emission factors have a high effect on the result of GWP. Further investigations on N2O emissions from biological treatment steps should be done to reduce the uncertainties. Finally, LCA is a powerful tool for revealing potential environmental impacts for supporting a sustainable way of decision making process.