Advanced Physical and Chemical Characterization of Stormwater Sediments

Abstract

<p> This work focuses on the advanced physical analysis of stormwater sediments using laser diffraction particle size analyzer and scanning electron microscope and chemical characterization using neutron activation analysis. Since previous studies of sediments from stormwater ponds in the Greater Toronto Area indicated a marginal-to-significant level of pollution by most of the regulated heavy metals, the characteristics of the storm water sediment samples obtained in this study were compared to the sediment quality guidelines of the Ontario Ministry of the Environment. The images from optical microscope showed that the particles in the dried sediment were irregular, and the sizes of each particle vary greatly. Using scanning electron microscope, it was shown that two different structures of particles were present in the storm water sediment. It was also observed that the main compositions (above 1000ppm) of the dried sediment included, in descending order of concentration, Ca >AI> Fe> K > Mg > Na >Ti > Mn. The trace compositions (below 1000ppm) included, also in descending order of concentration, Cl > Zn > Ba > Sr > Cr > V > La > Nd > As > Br > Co > Sc > Th > Sb > Sm > Eu. The concentrations of regulated elements such as Cr, Fe Zn, As and Mn were above the lowest effect level, suggesting that treatment of stormwater sediment may be necessary. A preliminary stormwater sediment treatment experiment using thermal plasma technology was therefore conducted. After the thermal plasma treatment, the percentage of total organic carbon decreased and eight gas compounds including CO, COz, NO, NOz, NOx, SOz, H2S and CxHy emitted during the process. Enrichments of Mg, Cl and Na were observed in the treated sludge while the concentrations of K and Ca decreased. The potential of thermal plasma technology for the treatment of contaminated stormwater sediment was demonstrated. </p>