Using the stormwater-quality model SEWSYS to identify sources and fluxes of hazardous organic substances

Stormwater-quality models simulating pollutant pathways in urban catchments are proven to be valuable means when planning and evaluating appropriate strategies to reduce the detrimental impacts of urban runoff [Zoppou, 2001]. SEWSYS, a substance flow model simulating pollutant concentrations in stormwater, is an effective instrument for predicting pollution loads from non-point sources and can therefore be used for proposing measures to reduce the release of contaminants into the environment [Ahlman, 2006]. SEWSYS is now being expanded from operating with nutrients and metals, to include also a few organic substances. In this study, two groups of organic compounds – phthalates and nonylphenols (NPs) – were selected for an initial flow analysis. These compounds, classified as “very toxic to aquatic organisms” [KEMI, 2007a], are high volume chemicals used as additives in a variety of products [KEMI, 2007b]. To incorporate phthalates and NPs into SEWSYS, an extensive literature study was accomplished. The study included identification of potential pollutant sources in urban areas, e.g. building materials and vehicles, and analysis of emission patterns and rates. Also, model input data such as source distribution and authentic rain series were collected from three urban catchment areas. Simulated pollutant concentrations were then compared with measured and analysed concentrations in stormwater from the investigated catchments. Preliminary model simulations showed that pollutant loadings and major contributing sources are catchment dependent: e.g. vehicles are the dominant sources of phthalates in traffic areas whereas construction materials are the most important sources in residential areas. These simulation results were then used for proposing adequate measures in order to mitigate phthalate and NP loads in stormwater. Calculations showed that by using phthalate- or NP-free construction materials, and by reducing the traffic load, the pollution load from residential and traffic areas was considerably decreased. These findings illustrate the use of SEWSYS as a tool for improving urban runoff quality, and corresponding simulations could easily be performed by local authorities for planning of effective abatement strategies. References Ahlman S (2006) Modelling of Substance Flows in Urban Drainage Systems. Doctoral Thesis, Department of Civil and Environmental Engineering, Chalmers University of Technology, Göteborg, Sweden. KEMI (Swedish Chemicals Agency). (2007a) Classification List. http://apps.kemi.se/klassificeringslistan/default.cfm KEMI (Swedish Chemicals Agency). (2007b) KemI-Stat. http://apps.kemi.se/kemistat/start.aspx?sprak=e Zoppou C (2001) Review of urban storm water models. Environmental Modelling & Software 16 (3), 195-231