EVALUATION OF THE LONG-TERM POLLUTION REMOVAL PERFORMANCE OF ESTABLISHED BIORETENTION CELLS

Abstract

Over the last two decades bioretention (biofiltration) systems have been commonly constructed in urban areas to manage stormwater runoff by moderating peak flows and reducing downstream pollution loads. Bioretention systems are generally soil-plant based systems which typically include a filter medium above a drainage layer. They are often either lined with a geofabric to support infiltration, or with an impermeable membrane to prevent infiltration and/or to allow stormwater harvesting and reuse. Bioretention systems are known to treat a range of stormwater pollutants through physical, chemical and biological processes such as mechanical filtering, sedimentation, adsorption, and plant and microbial uptake. However, the long-term pollution removal performance, particularly of heavy metals, remains largely unknown. It is generally accepted that the filter media used in bioretention systems has a finite life span, after which time it should be replaced. However, there is only very limited information available on when this should occur, or how to assess this. It is also recognised that contaminated filter media may require regulated disposal. This study presents results from a series of controlled field experiments conducted over two years which evaluated the pollution removal performance of a series of 10 year old bioretention systems located in an industrial state in Australia.; ;