WATER QUALITY VOLUME" IN THE NORTHWEST OF SPAIN FOR SIZING OF HIGHWAY RUNOFF TREATMENT SYSTEMS

Abstract

A pilot Austin sand filter has been designed to reduce metals, hydrocarbons and suspended solids from stormwater runoff in a highway reach in Fene (Spain). The unit filtrates a percentage of the annual runoff volume reducing the mobilized loads of pollutants through filtration and sorption. Before the final design of the filter, a field campaign was developed to characterize runoff pollution of the pilot catchment. Runoff was heavily polluted with sediments, COD, total phosphorous, copper and zinc. Field data was also used to develop a calibrated hydraulic model of the catchment with the Storm Water Management Model (SWMM). This model was used to size the treatment unit with a hydrologic-hydraulic criterion: % of treated annual runoff and number of discharges per year. The specific volume of the treatment unit is the so call "Water Quality Volume"-WQv- that is traditionally used to design sustainable urban drainage techniques. This paper present the analysis of the Austin filter yields using the hydrographs and polutographs measured in the control section. Following the previous hydrological methodology the sedimentation-filtration unit was sized with a WQv of 15 mm. The results of the study from field data show that 98% of the total volume of runoff and 96% of the total mass of suspended solids mobilized at the events characterized would be pass by the treatment.