Environmental and geometric optimisation of cylindrical drinking water storage tanks

PURPOSE: Urban water cycle construction processes are an important element to consider when assessing the sustainability of urban areas. The present study focuses on a structural and environmental analysis of cylindrical water tanks. The goal is to optimise cylindrical water tanks from both an environmental (environmental impacts due of life cycle assessment (LCA)) and a geometric perspective (building material quantities for construction purposes depending on the tank characteristics). METHODS: A sample of 147 cases was defined based on different positions (buried, superficial and partially buried), dimensions (combinations of heights and radii) and storage capacities (between 100 and 10,000 m³). A structural analysis was conducted for a defined set of cases to determine the quantities of steel and concrete required for its construction. The environmental impacts of the entire life cycle were assessed through a life cycle assessment (LCA). Additionally, environmental standards (the less impactful option for each dimension assessed: geometry, storage capacity and position) defined in the study were applied to realistic cases to evaluate potential environmental savings. RESULTS AND DISCUSSION: The LCA shows that materials are the main contributor to environmental impacts (more than transport, installation and end of life cycle stages). For this reason, the results of the structural and environmental assessments coincide. Taller water tanks have shown to be less impactful (60 to 70 % less impact for a 10.000-m³ tank). Regarding the position, superficial water tanks have shown to have between 15 and 35 % less impact than buried ones. The environmentally preferred water storage capacity is between 1000 and 2500 m³, being between 20 and 40 % less impact. For instance, an 8000-m³ tank would emit 1040 t of CO₂ eq. Applying the environmental standards 170.5 t of CO₂ eq could be saved (16 % of the total amount). CONCLUSIONS: The results of this study show that among the cases analysed, superficially positioned cylindrical water tanks of 8.5 m in height and of between 1000 and 2500 m³ in storage capacity present fewer impacts. The use of these standards in municipal water tanks construction projects may significantly reduce environmental impacts (10 to 40 %) in all impact categories.