Abstract
Increase of impervious surfaces in urban area followed with increases in runoff volume and peak flow, leads to increase in urban storm water pollution. The polluted runoff has many adverse impacts on human life and environment. For that reason, the aim of this study was to investigate the efficiency of nano iron oxide coated sand with and without magnetic field in treatment of urban runoff. In present work, synthetic urban runoff was treated in continuous separate columns system which was filled with nano iron oxide coated sand with and without magnetic field. Several experimental parameters such as heavy metals, turbidity, pH, nitrate and phosphate were controlled for investigate of system efficiency. The prepared column materials were characterized with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDXA) instruments. SEM and EDXA analyses proved that the sand has been coated with nano iron oxide (Fe3O4) successfully. The results of SEM and EDXA instruments well demonstrate the formation of nano iron oxide (Fe3O4) on sand particle. Removal efficiency without magnetic field for turbidity; Pb, Zn, Cd and PO4 were observed to be 90.8%, 73.3%, 75.8%, 85.6% and 67.5%, respectively. When magnetic field was applied, the removal efficiency for turbidity, Pb, Zn, Cd and PO4 was increased to 95.7%, 89.5%, 79.9%, 91.5% and 75.6% respectively. In addition, it was observed that coated sand and magnetic field was not able to remove NO3 ions. Statistical analyses of data indicated that there was a significant difference between removals of pollutants in two tested columns. Results of this study well demonstrate the efficiency of nanosized iron oxide-coated sand in treatment of urban runoff quality; upon 75% of pollutants could be removed. In addition, in the case of magnetic field system efficiency can be improved significantly.
Highlights
Storm water runoff from paved surfaces can carry large loads of various pollutants including heavy metals, hydrocarbons, nutrients and pathogens [1,2,3]
After coating of sand with nano iron oxide, the iron content of the sand was increased to 21% of its elemental composition (Fig 3b)
This is in agreement with result of Hsu et al [15]; showing the iron content of the sand was increased by 6% after coating with nano iron oxide
Summary
Storm water runoff from paved surfaces can carry large loads of various pollutants including heavy metals, hydrocarbons, nutrients and pathogens [1,2,3]. These pollutants may originate from motorized vehicle emissions, automobile tires, brake pads, corrosion of pavement, chemical deposition on or near the pavement surface and anthropogenic activities [1,4]. For example, have been investigated as practical alternatives for treating runoffs in several studies. These systems allow reducing primarily particulate pollutants. Filtration of storm water through a filter system filled with adsorbents (e.g. zeolite, peat, granular activated carbon or sand) is another possible treatment method that is relatively recent innovation for treatment of runoff [13]
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