The need for Enhanced Biological Phosphorus Removal (EBPR) in wastewater treatment plants (WTP) is increasing so that the development of steady state design models for WTPs using nitrification, denitrification and EBPR becomes more and more important. In developing such a model, theoretical and practical aspects must be considered if the qualitative and quantitative statements regarding the influence of various wastewater conditions (e.g. substrate composition) and surrounding conditions (e.g. influence of nitrate, duration of the anaerobic contact time) affecting EBPR shall be described. The presented EBPR design model is verified using data from various WTPs (e.g. Berlin-Ruhleben) currently using EBPR practices. Sensitivity studies for the most important influencing parameters and surrounding conditions are done, using fictious plant data. Recommendations are given, based on these studies, for the optimization of the EBPR process. These recommendation illustrates the most effective means towards improving the surrounding conditions for EBPR (e.g. increase of amount of readily available organic substrate, decrease of sludge age) with regard to an increase of the biologically removed phosphorus concentration.