Influence of sediment characteristics on long-term hydrology and water quality behaviour during the clogging process of a permeable asphalt

Sustainable urban drainage systems (SUDS) are common solution to address flow discharges, runoff volumes and pollutant concentrations caused by urban expansion and climate change trend. Among them, permeable pavements (PP) effectively manage and treat stormwater. The clogging process of PP has been addressed in previous studies but there is still room for improvement the knowledge about how it affects to their performance in terms of hydrological behaviour and pollutant removal and how it depends on sediment properties. The present study simulates and analyses the behaviour of a permeable asphalt through 47 sediment loading steps tested for six different sediment classes under laboratory conditions. The experiments were performed using permeable asphalt slabs in two laboratory rainfall simulators, measuring reductions in permeability, filtered and runoff flows, and water quality variations in effluents according to sediment loads and rainfall events. The results showed significant reductions of permeability (22-99 %) for sediment surface loads from 1 kg/m(2) onwards, except for very fine sediments (<125 mu m) (1 %). Permeability recovery after vacuum cleaning varied between 8 % and 100 % of original permeability. Sediment particle size distribution, organic matter content and rain events sequence were key variables influencing the permeability loss and its recovery, and quality of filtrated water. The hydraulic efficiency was high, filtrating almost 100 % of the applied rainfall, whenever the sediment surface load was below 4 kg/m(2), above which surface runoff was produced. The efficiency of the slab for pollutant retention was 96 % for COD, 76 % for TN, 79 % for TP, and 98 % for TSS.