Design comparison of experimental stormwater detention systems treating concentrated road runoff

The aim was to assess the treatment efficiencies of experimental stormwater detention (extended storage) systems receiving concentrated runoff that has been pretreated by filtration with different aggregates. Randomly collected gully pot liquor was used in stead of road runoff. To test for a 'worst case scenario', the experimental system received higher volumes and pollutant concentrations in comparison to large-scale detention systems under real (frequently longer but very diluted) runoff events. Gravel, sand, Ecosoil, block paving and turf were tested in terms of their influence on the water quality. Concentrations of five-day @ 20°C ATU biochemical oxygen demand (BOD) in contrast to suspended solids (SS) were frequently reduced to below international secondary wastewater treatment standards. The denitrification process was not completed. This resulted in higher outflow than inflow nitrate-nitrogen concentrations. An analysis of variance indicated that some systems were similar in terms of most of their treatment performance variables including BOD and SS. It follows that there is no need to use additional aggregates with high adsorption capacities in the primary treatment stage from the water quality point of view (e.g., Ecosoil).