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Treatment conditions for the removal of contaminants from road runoff

In this work, field studies were conducted in three separate watersheds along the same motorway with an annual average daily traffic exceeding 120,000 vehicles. The aim was to assess treatment conditions for the removal of contaminants from road runoff. The study of mass transport of total suspended solids used the EU Directive (1991/271/EEC) discharge requirement for urban wastewater treatment: 60 mg/l during winter and summer. The results showed that a capture of total runoff volume was necessary during both seasons. Ten metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), as dissolved and particulate bound, were studied in the road runoff during a winter season and the following summer period. The dissolved part of Al, Cd, Co, Cr, Mn, and Ni was significantly higher in winter. The mass concentration (mg/kg) for all metals was significantly higher over the summer except for Al and Co, which showed a higher mass concentration during the winter. The total metal concentration showed a good correlation to total suspended solids (TSS) during winter with exception for Cd. Good correlation to TSS was also found for the summer period for Al, Cu, Fe, Mn, Ni, and Zn. A simple model could describe sedimentation by the initial concentration of TSS, albeit road salt (NaCl) had a significant impact on the sedimentation process during winter. Removal of dissolved metals was studied by column experiments using water granulated blast furnace slag. The result showed good removal for Cd, Cu, Ni, and Zn independent of NaCl concentrations. Sediment accumulation (mg sediment/mm precipitation) was relatively consistent for the studied summer seasons as opposed to winter. The sediment differed in metal mass concentrations (mg/kg) between the seasons. Correlations of Cu and Zn were high in regard to the guidelines for sensitivity of sediment dwelling organisms and Swedish guidelines for contaminated soils. The findings suggest that the entire runoff volume must be captured for treatement. The reduction of TSS concentration could be estimated for a specific surface load (m/h). This would also apply for majority of the studied metals that correlated well to the particulate material. Reactive filter technology using water granulated blast furnace slag could be applied for treatment of runoff for the reduction of dissolved metals. However, long-term studies are necessary for its practical implementation. Furthermore the work shows that on-line turbidity measurements could be used for expedient process control for treatment facilities in similar watersheds dominated by roads. The work could be used together with existing design methods and models to evaluate and optimise road runoff treatment.

Language

  • English

Media Info

  • Pagination: 35p+app
  • Serial:
    • TRITA-LWR. PHD
    • Issue Number: 1032
    • Publisher: KUNGLIGA TEKNISKA HOEGSKOLAN. DEPARTMENT OF LAND AND WATER RESOURCES ENGINEERING
    • ISSN: 1650-8602

Subject/Index Terms

Filing Info

  • Accession Number: 01081563
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • ISBN: 978-91-7178-661-6
  • Files: ITRD
  • Created Date: Nov 29 2007 12:37PM