Sustainable Urban Drainage Systems (SUDS) represent a paradigm shift in stormwater management, offering holistic solutions to urban water challenges. This review examines SUDS principles, design strategies, effectiveness and barriers to implementation. SUDS prioritize infiltration and mimic natural hydrological processes to reduce flood risk, improve water quality and support ecosystems in urban environments. Effective SUDS design integrates different components such as permeable pavements, green roofs, and rain gardens, tailored to the local context. Evidence suggests that well-designed SUDS can mitigate peak flows, reduce runoff volumes, and purify water. However, barriers to widespread adoption include lack of awareness, upfront costs, and regulatory complexity. Overcoming these will require collaborative stakeholder action to prioritize education, policy support, and funding opportunities. Future research should focus on optimizing SUDS design, assessing long-term performance, and quantifying socio-economic benefits. By integrating SUDS into urban landscapes, cities can strengthen hydrological resilience, promote sustainability, and enrich urban life.

Wastewater from the potato processing industry called protamylasse is rich in proteins and carbohydrates that potentially can be valorized through cultivation of microalgae by mixotrophic metabolism. However, the complex organic compounds are a challenge, as algae grow best on simple compounds such as volatile fatty acids (VFA). This study demonstrates a new two-stage system. First, VFA production was achieved by testing mesophilic and thermophilic anaerobic acidification (AA) at a short hydraulic retention time (HRT; 3.3 and 5 days) resulting in the release of ammonium and phosphate. HRT of 5 days and thermophilic conditions was optimal considering the high acetate yield of 0.23 g and 22 ml CH₄ per g volatile solids (VS). Then, Chlorella sorokiniana was chosen based on the obtained growth rate, and better adaption in ammonium-rich AA effluent after screening several tested microalgae (Chlorella sorokiniana, Chlorella vulgaris, Scenedesmus obliquus, and Haematococcus pluvialis). It was cultivated for valorization of nutrients and organics and successfully upscaled to 25 L photobioreactor (PBR) scale under both batch and continuous operation with high dosage of 25% (8.2 g L⁻¹ of VS) of AA effluent at an HRT of 5 days in the PBR. Chlorella sorokiniana removed more than 99% of the chemical oxygen demand (COD) and the VFA during continuous flow PBR operation. This approach contributed to the final removal efficiency of 71%, 91%, and 78% for phosphorus, nitrate, and ammonia, respectively, and production of microalgae biomass with more than 73% protein. Thus, a promising process for simultaneous treatment of high strength wastewater for microalgal protein production.

The effects of climate change and urbanisation, such as more intense rainfall and changing land use patterns, are putting increasing pressure on urban drainage systems. This study proposes a comprehensive methodology for evaluating the effectiveness of sustainable urban drainage systems (SUDSs) in mitigating flooding and managing stormwater in both current and future scenarios. The approach integrates geospatial data, including digital elevation models (DEMs) and land use information, to delineate catchments and characterise hydrological parameters. Historical rainfall records and hydrological modelling were employed to define two baseline storm events: an extreme storm involving 422 mm of rainfall over 2 h, and an average storm involving 2.84 mm of rainfall over 1 h and 18 min. Future scenarios were developed by updating these baseline events using annual rates of change in maximum and average precipitation derived from climate projections between 2025 and 2100. The analysis incorporates seven CMIP6 climate scenarios: SSP1-1.9, SSP1-2.6, SSP4-3.4, SSP4-2.5, SSP4-6.0, SSP3-7.0, and SSP5-8.5. A stochastic simulation of 1000 storms per year was carried out using a custom-built conceptual hydrological model based on CN and developed in Python, which reflects interannual variability. The results show that extreme storm volumes could increase by up to seven times and average storm volumes by up to two and a half times. Additionally, discharge peaks could exceed baseline values by up to 20% in some years, suggesting an increased occurrence of extreme runoff events. The methodology assesses SUDS performance by comparing runoff and hydrological responses between baseline and future estimates. This framework enables vulnerabilities and adaptation needs to be identified, ensuring the long-term effectiveness of SUDSs in managing urban flood risk. Addressing uncertainties in climate and land use projections emphasises the importance of integrating SUDS assessments into wider urban resilience strategies.

Urban water systems face increased risk from climate variability, increasing irrigation needs, and pressure on traditional water resources. Sustainable Urban Drainage Systems (SUDS) have become a key tool for curbing runoff, mitigating flood risk, and building water resource independence. However, the performance of these tools is currently assessed only at urban or parcel scales, with limited synergy between strategic planning and site-specific applications. In this study, we have developed a methodological framework to calculate the hydrological performance and reuse benefits of SUDS at catchment and parcel scales. This Curve Number-based method involves estimating runoff, storage dynamics and irrigation demand under various implementation and climate scenarios. The framework has been adapted for two Mediterranean case studies: Bari (Italy) at the catchment scale to capture runoff generation under current and future climate conditions, and Madrid (Spain) at the parcel scale in the Valdebebas region to evaluate local implementation and the sustainability potential of urban reverts. The results show that runoff generation depends heavily on the timing of precipitation. Greater variations and an increase in extreme events will shape future scenarios. At the catchment scale, system behaviour is constrained by runoff availability rather than storage capacity. There is a low average filling rate and evident diminishing returns as the application increases across different scales. Significant spatial variation emerges at the parcel scale, revealing this gap between runoff generation and irrigation demand. Although expanding SUDS usage reduces the demand for external water, measures that achieve full coverage led to uneven storage and low efficiency gains. In both scales, a threshold of around 50% runoff reuse for irrigation appears to provide a good trade-off between performance/efficiency. These findings emphasise the importance of examining both system-level limits and local implementation boundaries at multiple scales to prevent excessive expansion and reduce resource consumption. The developed framework is a transferable tool that facilitates the integration of urban water management into water infrastructure by combining strategic planning with site-specific design, thereby constructing a more resilient urban irrigation system. RESUMEN Los sistemas hídricos urbanos están cada vez más expuestos a la variabilidad climática, al aumento de la demanda de riego y a la creciente presión sobre los recursos hídricos convencionales. Los sistemas urbanos de drenaje sostenible (SUDS) han surgido como una estrategia clave para mitigar la escorrentía, reducir el riesgo de inundaciones y fomentar el uso local del agua. Sin embargo, su rendimiento suele evaluarse de forma aislada, a escala urbana o parcelaria, y existe una integración limitada entre la planificación estratégica y su implementación a nivel local. En esta tesis se desarrolla y aplica un marco metodológico de doble escala para evaluar el rendimiento hidrológico y el potencial de reutilización de los SUDS tanto a escala de cuenca como a escala parcelaria. El enfoque se basa en el método del número de curva e integra la estimación de la escorrentía, la dinámica de almacenamiento y la demanda de riego en diferentes escenarios de implementación y condiciones climáticas. El marco se ha aplicado a dos casos de estudio mediterráneos: Bari (Italia), analizado a escala de cuenca para caracterizar la generación de escorrentía en condiciones climáticas actuales y futuras, y Madrid (España), donde se ha realizado un análisis a escala parcelaria en el área de Valdebebas para evaluar las condiciones locales de implementación y el rendimiento del reúso. Los resultados muestran que la generación de escorrentía está fuertemente controlada por la distribución temporal de las precipitaciones y que los escenarios futuros se caracterizarán por una mayor variabilidad y una mayor amplificación de los eventos extremos. A escala de cuenca, el comportamiento del sistema está principalmente limitado por la disponibilidad de escorrentía más que por la capacidad de almacenamiento. Se observan bajos niveles medios de llenado y rendimientos decrecientes a medida que aumenta el grado de implementación.

Although Sustainable Urban Drainage Systems (SUDS) are widely recognised as essential components of resilient urban water management, the large-scale planning and evaluation of such systems remain challenging. This study assesses the hydrological and economic performance of SUDS in Madrid (Spain) under the SSP1-2.6 and SSP5-8.5 climate scenarios, applying a dual-scale methodology based on the Curve Number (CN) model. At the catchment scale, SUDS show substantial potential for irrigation reuse, with runoff-rich catchments reaching hydrological saturation earlier (plateau at r ≈ 0.4) and runoff-limited catchments stabilising at higher implementation levels (plateau at r ≈ 0.6). At the parcel scale, partial-coverage configurations (50% irrigation coverage) outperform full-coverage solutions (100% irrigation coverage), achieving maximum retention levels of 70% in SSP1-2.6 and 50% in SSP5-8.5 while requiring less surface area (10–15%). From an economic perspective, positive net present values (NPVs), acceptable internal rates of return (IRRs), and feasible payback periods occur only at very low retention levels (r < 0.05), with financial performance declining rapidly as storage capacity increases.