Evaluation of a sand filter material for road runoff treatment– pilot-scale field trial focused on copper and zinc removal

Abstract

The effects of stormwater discharges on receiving aquatic environments and the need for their purification were highlighted by an EU court in May 2020. The ruling stated the need for removal of dissolved pollutants, which justifies field studies for development of far-reaching methods for runoff treatment. In this study, a standard sand was used as medium for road runoff filtration and removal of dissolved and particle-bound (<0.45 μm) zinc (Zn) and copper (Cu). Data included 24 road runoff events, mimicking the flow variations and pollutant emissions over a seven-month period. The findings showed that sand can be used to remove Zn and Cu from road runoff in a gravity fed treatment system at a surface load ranging from 16.8 to 201 L m−2 h−1. The removal of total Zn and Cu was 93 and 67%, respectively. Dissolved Zn was efficiently removed by the sand (87%), however not Cu (19%). The sand efficiently removed total suspended solids (TSS) from the maximum occurring 443 mg L−1 to below 5 mg L−1. No head loss due to the TSS loadings was observed. The sand's potential to remove the investigated metals was shown, but in the longer term, effluent concentrations may exceed permitted values. HIGHLIGHTS Removal of Cu and Zn in runoff from the E4 motorway in Stockholm was studied for the first time in a sand filtration system.; Total Zn, as well as the dissolved phase, was removed to concentrations close to the most stringent effluent values applied in Sweden for stormwater.; Cu occurs as dissolved species and its removal from road runoff requires more treatment in addition to sand filtration.; Sand is suggested to be used as a cover layer when reactive filter media are used for road runoff treatment.;

Keywords

• clogging
• column experiment
• dissolved metals
• head loss
• road runoff treatment plant
• stormwater