End-of-life of a Sustainable Drainage System: Assessment of Potential Risk of Water Pollution through Leaching of Metals

Sustainable Drainage systems (SuDS) have emerged as very effective and highly attractive approach for storm peak control, pollution retention and biodegradation, water quality improvement and groundwater re-charge via use of micro-scale integrated management practices. One of the SuDS devices widely used to infiltrate, store and treat surface runoff which allows it to recharge groundwater is the pervious paving systems (PPS). Previous studies have demonstrated relatively high removal efficiencies of 98.7% of total hydrocarbons, 95% of suspended solids, 93% of lead and 89% of COD etc. Although a few of the studies have evaluated the performance of the PPS system at end-of-life such as the hydrological performance, pollutants retention, pollutants biodegradation etc., none has assessed the potential groundwater and soil pollution by pollutants such as metals at end-of-life. Thus, the aim of this study was to evaluate potential risks associated with the decommissioning and beneficial use of wastes generated during the dismantling of the PPS. The method involved the determination of leachable concentrations of 14 metals in the PPS samples made up of extracts from Pavement blocks (P), Aggregates Alone (AA), Aggregates and Dust (AD), Dust alone (D) and Geotextile fibre which, were analysed and compared to appropriate risk-based regulatory threshold limits. The results showed that the measured concentrations of all the metals were below the appropriate risk-based regulatory threshold values for irrigation purposes as specified by FAO and USEPA. Furthermore, results all indicate that the dismantled materials can be reused as recycled aggregates for other civil construction purposes as they were all below EU LFD WAC for inert waste. This has potential to increase recycling of aggregates from construction and demolition wastes among EU Member States and minimize dependence on virgin aggregates and hence, reduction on exploitation of natural resources and sustainability of the PPS system.