In this study the insustainability of the treatment of municipal wastewater is evaluated with the LCA-methodology. Life-Cycle Assessments (LCA) analyze and assess the environmental profile over the entire life cycle of a product or process. The LCA-methodology proved to be a proper instrument to evaluate the wastewater treatment plant on the sustainability. However, environmental impacts which are caused by sludge handling should still be classified. Besides that, the LCA should be carried out on regional level instead of on national level. In a situation of high nutrient removal the contribution of the treatment of municipal wastewater to the total insustainability level in the Netherlands is relatively low. When the sustainability of the WWTP has to be improved, the most attention has to be paid to the minimization of discharge from pollutions with the effluent and minimization of the sludge production. Because the contribution of energy consumption is relatively low, less attention can be paid to the minimization of the energy demand. The building of a WWTP and the use of chemicals are not determining the insustainability of the WWTP.