Filtration Systems for Stormwater Quantity and Quality Management: Guideline for Finnish Implementation

The overall objectives of urban stormwater management are appropriate drainage to minimize urban flood risk and erosion, and protection of groundwater and surface water quality. Urban systems of green infrastructure such as rain gardens, green roofs, permeable pavements, swales, wetlands, and other designed to reduce stormwater surface runoff volume have gained popularity due to their cost effectiveness as well as their multiple co-benefits. Systems of green infrastructure often utilise engineered infiltration or subsurface filtration media to optimise hydraulic conductivity/maximise water infiltration, filter particulate pollutants or provide growth media for plants and microbes. The use of chemically reactive geo- or bio-based filter media can enhance pollutant removal. The wide range of different filter materials available enables development of fit-for-purpose solutions to address a variety of site-specific conditions, such as existing soil characteristics, site conditions, anticipated or measured pollutant loads and expected rainfall. Modelling of stormwater quantity and quality, whether at catchment or site scale, provides essential information for planning and design of effective stormwater management systems. Detailed site examination of key hydrological processes and stormwater constituent source areas allows optimization of stormwater treatment system design and informs decision-making. A multi-disciplinary approach that effectively integrates robust engineering and design principles with novel material technologies and innovative blue-green solutions can manage stormwater surface runoff quantity and quality to enhance the resilience of urban areas to climate change.