Föroreningsreduktion och flödesutjämning i makadammagasin – En studie av ett makadammagasin i Kungsbacka / Pollutant Removal Efficiencies and Flow Detention of Infiltration Trenches – An Investigation of an Infiltration Trench in Kungsbacka
Infiltration trenches are commonly applied for treatment of urban stormwater. However, the opinions whether their main purpose is to detain peak flows or to reduce pollutant loads of urban stormwater, are varying. In Sweden, there is also a lack of accurate data of the pollutant removal efficiencies and the results of the performed studies are varying a lot. For this this reason, Norconsult AB in cooperation with Chalmers University of Technology initiated a Master Thesis project with the purpose to investigate the flow detention and pollutant removal of infiltration trenches. An infiltration trench at a parking lot in Kungsbacka has been investigated during the spring and summer of 2012. In total seven rain events have been analyzed. The results show that the infiltration trench has an average removal efficiency of 80 % for suspended solids, approximately 50 % for total inorganic nitrogen and all removal efficiencies for heavy metals were over 50 %. Zinc, lead, copper and chromium have removal efficiencies of 70–80 % while cadmium and nickel have removal efficiencies of 50–60 %. The observed flow hydraulics showed good flow detention since the outflow hydrographs were generally lower than the inflow hydrographs for all storm events. The conclusion is that the infiltration trench has good pollutant removal efficiencies, and most likely well-functioning flow detention. Due to that seven storm events have been analyzed, the result is considered to be statistically reliable.