This study evaluated the performance of media filtration stormwater treatment devices for removing suspended solids, copper and zinc from road runoff.
Between September 2010 and March 2012, a field programme comprising the measurement of runoff volumes and the collection and analysis of influent and effluent samples was conducted using three different commercially available devices installed at sites in the Auckland region.
Field conditions were found to have a marked influence on device performance. In particular, low suspended solid concentrations in runoff contributed to each of the three devices achieving lower overall contaminant removal rates than reported previously, although performance varied in relation to differences in influent quality between sites and between storm events.
Relatively frequent bypassing of treatment also influenced performance; with contaminant removal rates typically lower during storm events where bypassing occurred.
The devices generally achieved only limited removal of dissolved copper and zinc, with export of dissolved zinc occurring in one case and effluent samples from another of the devices routinely exceeding a water quality guideline for dissolved zinc.
The results of the study provided the basis for guidance on the use, design, operation and maintenance of media filtration devices and on expectations relating to their performance.
Keywords: contaminant removal, copper, media filtration devices, particle size distribution, road runoff, stormwater treatment, suspended solids, zinc