Removal of Contaminants of Emerging Concern (CECs) in Urban Waste Water Treatment Plants (UWWTPs) is highly variable and often low, causing pollution of surface and drinking water. As knowledge on breakdown of CECs is severely limited, we aim to assess and optimise biodegradation of a selected group of CECs in several UWWTPs. To that end, we will relate physico-chemical properties of micro-pollutants, genetic/enzymatic characteristics of microbes and physical conditions in reactors and treatment plants to each other, combining empirical and modelling approaches. New data, improved models, guidelines for optimisation and a full analysis of environmental and financial costs and benefits will be delivered. The outcomes will be beneficial for a large group of (end-)users, including waterboards, drinking water companies, water technology companies, governmental agencies and their advisors.