Conventional WWTPs were not designed for the removal of micropollutants and thus, some of them are eliminated, transferred to sludge or biotransformed, whereas others are not altered by treatment. Upcoming regulations will be more and more stringent towards the release of micropollutants to the aquatic environment, or during sludge disposal. A more mechanistic knowledge, structured in mathematical models can be a potential means for optimizing treatment removal, either with existing infrastructure or by identifying additional treatment stages. Several gaps still remain and are ongoing topics of research all over the world: detailed dynamic data, good quality data, new concepts for modelling, new inputs, etc. The workshop will discuss approaches that are under development. What is the optimum complexity of process models to predict the fate of micropollutants through WWTPs? The novelty of the proposal consists in gathering experts from different disciplines. This is important since various aspects need to be considered for solving this complex problem successfully.