Construction of a Biofiltration system for Urban Water Runoff (UWR) management: environmental impact determination using Life Cycle Assessment (LCA)

Construction of a Biofiltration system for Urban Water Runoff (UWR) management: environmental impact determination using Life Cycle Assessment (LCA) V. Acevedo-García* * Singular Strategic Safe and Sustainable Initiatives (S4I), AIMEN, 27A Calle Relva Torneiros, Porrino, 36410, Spain (E-mail: [email protected]) Abstract UWR can be highly polluted and have significant negative impacts on human well-being and ecosystem health. In WATERUN project, SUDs will be implemented and optimized as a decentralized, sustainable and efficient treatment to mitigate the impact of UWR. An LCA was carried out to determine the environmental impacts of a Biofiltration system implementation (Construction phase). The construction materials used in the Structure are the ones that cause most of the environmental impact of the Construction phase. Keywords environmental impact; Life Cycle Assessment; SUDs; UWR INTRODUCTION Diffuse water pollution in urban areas remains a serious global environmental issue. Urban diffuse pollution enters the urban water catchment through precipitation, infiltration, or runoff processes from different urban surfaces. Urban runoff can be highly polluted with suspended solids, nutrients, heavy metals (Hengen et al. 2016), polycyclic aromatic hydrocarbons and microplastics among others. The cumulative effects of that pollution can have significant negative impacts on human well-being and ecosystem health. WATERUN project aims to develop an innovative methodology to support the implementation of urban water runoff (UWR) management plans in cities, integrating the principles of the WaterSensitive Urban Design (WSUD). This methodology will provide preventive and mitigation solutions, along with best management practices, adopting a holistic perspective (from source identification to remediation strategies) for diffuse water pollution control in urban catchments. This requires the development of infrastructures to investigate hydrological performance and pollution reduction, which will allow the assessment of their suitability for managing UWR using nature-based solutions in a way that minimizes impacts on the natural environment. In WATERUN project, Sustainable Urban Drainage Systems techniques (SUDs) are implemented and optimized as a decentralized, sustainable and efficient treatment to mitigate the impact of UWR. In Santiago de Compostela (Spain), a Biofiltration system has been built in the Tambre Industrial Park to treat UWR from Ptolomeo street, a high-traffic street with heavy and light traffic associated with industrial activities (commercial, courier, storage). Ptolomeo street UWR shows a significant level of contamination, containing heavy metals, microplastics and PAHs, all linked to traffic. The Biofiltration system will allow reducing the pollutant loads in the receiving waters by treating the UWR. However, at the same time its implementation, operation and decommissioning causes environmental damage. The objective of this study is to determine the environmental impacts of the Ptolomeo street Biofiltration system Construction phase via Life Cycle Assessment (LCA) in order to identify environmental hotspots and improvement opportunities, thereby supporting the innovation process. MATERIALS AND METHODS To determine the environmental impacts of the Ptolomeo street Biofiltration system construction, an LCA was carried out following ILCD handbook and ISO14040 methodology. The software SimaPro v10.1 with the database Ecoinvent 3.10 and the Environmental Footprint 3.1 method were used. The functional unit was 1 m3 of treated water, and the LCA scope was Cradle-to-Gate. The goal is to identify the primary environmental impacts associated with the Ptolomeo street Biofiltration system implementation (Construction phase). The data for the Life Cycle Inventory (LCI) consisted of primary data provided by our partners FUNDACION CENTRO GALLEGO DE INVESTIGACIONES DEL AGUA (CETAQUA), VIAQUA GESTION INTEGRAL DE AGUAS DE GALICIA SAU (VIAQUA) and UNIVERSIDADE DA CORUNA (UDC). This data included inputs from the Construction phase, specifically the construction materials of the Biofiltration system components: Structure, Filtration system and Pipes. Works required to convey UWR into the systems (road channels, pipes) were excluded. Additionally, the present study does not cover the flow monitoring and water quality sampling equipment the Biofiltration system is equipped with, as it was deemed beyond the scope. RESULTS AND DISCUSSION Figure 1 shows the environmental impacts resulting from the construction of the Ptolomeo street Biofiltration system. As can be seen, the highest environmental impact is located in the category Human toxicity, cancer (31.7%), followed by Climate change (23.4%), Resource use, fossils (12.4%) and Particulate matter (7.1%). Figure 1. Ptolomeo street Biofiltration system Construction phase Environmental impact. The contribution to the environmental impact by each of the Ptolomeo street Biofiltration system components (Structure, Filtration system and Pipes) in each of the LCA categories is shown in Figure 2. Pipes contribute the least to the environmental impact in all the categories analysed, except for Ozone depletion which accounts for 37.8%. The component causing the greatest environmental impact in almost all the categories analysed is Structure (in 15 out of 16 categories) with an average of 73.8%. Figure 2. Contribution to the environmental impact by each of the Biofiltration system components in each of the LCA categories. From the point of view of system components, the Structure contributes 80.6% of the total environmental impacts resulting from the Construction phase, while the Filtration system and Pipes account for 17.3% and 2.1%, respectively. This is in line with Figures 1 and 2, as 31.7% of the environmental impact of the Construction phase corresponds to a single category, Human toxicity, cancer, in which 97.5 % of the environmental impact is due to the Structure. Therefore, the construction materials used in the Structure are responsible for most of the environmental impact of the Ptolomeo street Biofiltration system Construction phase. The main cause is the reinforced concrete required. The reason is that cement and steel are two of the most carbon-intensive materials in construction, due to their energy-intensive production processes and reliance on fossil fuels. It is recommended to investigate alternatives, for example, the transition to low-carbon alternatives such as recycled steel and alkali-activated concrete, with an emission reduction potential of 30 to 90% (Bhattarai et al. 2025). ACKNOWLEDGEMENTS Funded by the European Union under GA number 101060922. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them. REFERENCES Hengen, T.J., Sieverding, H.L., Stone, J.J. 2016 Lifecycle Assessment Analysis of Engineered Stormwater Control Methods Common to Urban Watersheds. Journal of Water Resources Planning and Management 142(7), 04016016. https://doi.org/10.1061/(ASCE)WR.19435452.0000647 Bhattarai, B., Bhattarai, B.S., Maskey, R.K., Bhochhibhoya, S. 2025 Life Cycle Assessment of Reinforced Concrete Residential Buildings in Nepal: Pathways to Carbon Footprint Reduction through Sustainable Construction. Building and Environment, 281, 113199. https://doi.org/10.1016/j.buildenv.2025.113199