The clogging behaviour and treatment efficiency of a range of porous pavements

This paper presents the findings of a laboratory investigation into the clogging behaviour of three different porous pavements that were most representative of the available range and their pollutant removal efficiency over time. These pavements were monolithic Porous Asphalt (PA), Permapave (PP), and modular Hydrapave (HP). The pavements were dosed with a semi-synthetic stormwater mixture over a continuous period of 20 weeks, at a flow rate of 3.9 mm/hr, the intensity of which corresponds to the 90 th percentile of an average recurrence interval (ARI) storm in Melbourne or the mean of an ARI storm in Brisbane, Australia. Inflow and outflow samples were collected and analysed for key pollutants such as total suspended solids (TSS), total phosphorus (TP), total nitrogen (TN), heavy metals and dissolved nutrients. Flow rates, pH and temperature readings were also measured. A 1 in 5 year Brisbane storm, which is equivalent to more than a 1 in 100 year Melbourne storm was simulated in the 6 th , 10 th and 17 th weeks to evaluate the rate of clogging; this corresponded to 5.5, 10.4 and 17.5 years of operation in Melbourne, or about half these periods in Brisbane. Under normal dosing, all three systems were capable of removing approximately 100% of TSS, 30% of TP and 20% of TN after 17 years of operation, with no large differences between the systems. For the ‘average’ conditions, none of the pavements showed signs of clogging even after 17 years of operation in Melbourne or 8.5 years in Brisbane. However, for the flooding conditions, HP started to pond after 5.5 years in Melbourne (or less than 3 years in Brisbane), while PA showed signs of clogging after 10.4 years in Melbourne (5.2 years in Brisbane). However, Permapave has still not showed signs of clogging after 17 years of operation in Melbourne, even for a 1 in 100 year event.