Retention of heavy metals by stormwater filtration systems: breakthrough analysis.
Biofiltration systems are widely used to mitigate the impacts of stormwater on receiving waters, however their long-term capacity to retain heavy metals has not previously been assessed. Accelerated-dosing laboratory experiments were used to assess the likelihood of breakthrough occurring for three different types of soil-based filter media that are commonly used in stormwater biofilters. In all cases, breakthrough of zinc (Zn) was observed, but not of cadmium (Cd), copper (Cu) and lead (Pb). If biofiltration systems are sized so that they are large relative to their catchment (at least 2-3% of its area) or have a deep filter layer (at least 0.5 m deep), then breakthrough will not occur for at least ten years and probably longer. However, after the equivalent of 12-15 years of operation, Cd, Cu and Zn had accumulated in the filter media to levels that exceeded human health and/or ecological guidelines. Further, depending on the design, it is possible that spent filter media may be classified as contaminated soil and thus require special disposal.
Centre for Water Sensitive Cities, Department of Civil Engineering, Monash University, Victoria 3800, Australia. belinda.hatt@monash.edu
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Hatt
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Steinel
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Deletic
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Fletcher
D002980:Climate; D055867:Cyclonic Storms; D005374:Filtration / Q000379:methods*; D019216:Metals, Heavy / Q000302:isolation & purification*; D011891:Rain; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D014876:Water Pollution / Q000032:analysis
D019216:Metals, Heavy; D014874:Water Pollutants, Chemical