Upgrading Wastewater Treatment Plants for Nutrients Removal: Possible strategies for the most relevant cases in the Portuguese context UWWTD revision in 2024 established more stringent limits on nutrients removal for UWWTPs. Out of the 529 Portuguese WWTPs present in EU 2022 dataset, 108 must be retrofitted to adapt to the new EU standards. Of these 108 WWTPs, 68, with a nominal treatment capacity corresponding to 55% of the national one, either lack a secondary treatment step, or possess it in the form of a continuous suspended biomass system. Denmark model, globally recognised as a benchmark in the wastewater field, was studied to find a possible retrofitting strategy for these 68 Portuguese WWTPs.