Lucía Barbero Morales defended her doctoral thesis on 16 April at the University of Alcalá. The thesis, entitled “Nature-based Solutions for Urban Wastewater Treatment: Optimisation Strategies for Green Filters”.

The research evaluates the effectiveness of Green Filters as a Nature‑Based Solution for nutrient attenuation—particularly nitrates—in urban wastewater. The study was conducted in a pilot‑scale system treating real wastewater over a four‑year operational period, analysing different irrigation management strategies and the incorporation of soil amendments. The results show that the use of drip irrigation and the application of a wood‑chip mulch layer significantly enhance nutrient removal and biodegradation, while reducing the risk of leaching, the process by which dissolved substances such as nutrients, salts or contaminants are transported by water through the soil to deeper layers or groundwater.

The thesis highlights the importance of integrated soil and water management to consolidate Green Filters as a sustainable, low‑cost technology with strong potential for urban wastewater treatment, biomass production and aquifer recharge in urban environments.

This doctoral research was carried out within the framework of the FILVER+ project (CTM2016‑79211‑C2‑1‑R) and the PhD Programme in Hydrology and Water Resources Management. The thesis was supervised by Irene de Bustamante Gutiérrez, Director of IMDEA Agua and researcher in the Soil and Water Quality in the Environment research group, and co‑supervised by María de las Virtudes Martínez Hernández, also a researcher in the same group.