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Development of Laboratory Testing Method for Certification of Filter Media Used in Decentralized Stormwater Treatment Facilities

Authors: Tadele Haile, Natural Resources Research Institute; Maria Fuerhacker, University of Natural Resources and Life Science

Abstract: Decentralized filtration systems are effective for the removal of dissolved and particulate pollutants from traffic areas and metal rooftops runoff. However, their long-term performance strongly depends on hydraulic performance and the sorption capacity of the filter media. Field testing is often highly variable due to different site conditions and monitoring strategies. As a result, a laboratory testing method that mimics real environmental conditions was developed as a national filter media certification process, issued by the Austrian Standards Institute (ASI). The test method consists of several steps including hydraulic performance, particle retention (TSS), heavy metal (Cu, Pb, and Zn) removal and remobilization under de-icing salt (NaCl) application, retention of total petroleum hydrocarbons (TPH), and acid neutralization capacity. Three different runoff areas (trafficable areas, copper roofs, and zinc roofs) were tested individually by applying a 4-year pollutant load. The requirements for approval are based on minimum removal efficiencies and threshold values for groundwater protection. It includes an infiltration rate of at least 1*10-5 m/s, TSS retention of > 80%, TPH removal of >95% and effluent concentration of 0.1 mg/L, Cu removal of >80%, and Zn removal of >50%. In addition, the effluent concentration of Pb for the heavy metal test to simulate runoff from trafficable areas must be < 9 µg/L. For the remobilization test following, the effluent concentration criteria are < 50 µg/L for Cu and < 500 µg/L for Zn. To ensure reproducibility of the test method, hydraulic and pollutant retention efficiency of several filter media was investigated. Results demonstrated the test method is reproducible and has been used as a national standard protocol for the approval of all types of filter media in Austria (ÖNORM B 2506-3, 2016). Field verification revealed the testing protocol is a useful decision-making factor for designing stormwater treatment facilities.