Within the framework of the AQUAlity project, the achieved results encompass: 1) Development and application of a protocol for investigating the photochemical fate of contaminants of emerging concern (CECs) and their degradation products (DPs) as well as AOPs treatment; 2) Elucidation of the significance of photochemical reactions and their contribution to the abiotic transformation of CECs in water systems; 3) Understanding the role of the major reactive species generated during the photodegradation process; 4) Assessment of the toxicity of CECs, and their degradation products (DPs) with the employment of an integrated toxicity approach. With respect to the robustness of the processes, experimental design (DOE) and response surface methodology (RSM) were employed to determine the region where the process is not affected by variations of not significant factors and to identify the factors requiring strict control. We proposed four wastewater treatment plant (WWTP) scenarios based on practicability and feasibility of the application, providing guidance on which factors can be neglected or should be strictly controlled, for each WWTP.