The evaluation of heavy metal contents in the bottom ash from Burnaby refuse incinerator

• Main Author: Ting, Jyh-Haw
• Format: Others
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/5560

Eighteen sets of bottom ash samples from the Greater Vancouver Regional District’s (GVRD) Burnaby MSW Incinerator were collected during 1991. The samples were analyzed for particle size distribution based on seven fractions. The coarse fractions with particle sizes greater than the 9.5 mm (3/8 inch) diameter were analyzed as to material content, while the fine fractions with particle sizes less than the 9.5 mm were subjected to leaching tests following the Leachate Extraction Procedure (B.C. Reg. 63/88). Fine materials clinging to the coarse particles were collected and tested for the leachability of heavy metals. The total metal levels in the particles with sizes less than the 9.5 mm diameter were also evaluated. The results of the particle size gradation tests indicate that the bottom ash from the Burnaby MSW Incinerator generally meets the specification for a wellgraded base course specified in the B.C. Standard Specifications for Highway Construction. The material distribution in the fractions with particle sizes greater than the 9.5 mm diameter have shown that magnetic materials contributed about 12 % by weight of the bottom ash stream, which suggests the need of a second magnet. Inert materials such as glass, rock, concrete, ceramic and clinker were found to be the largest component of the coarse particles with sizes greater than the 9.5 mm diameter. The leaching test results of the three fine bottom ash fractions with particle sizes less than the 9.5 mm diameter have shown that lead is the only of the eight selected elements which would leach out with levels exceeding the regulation limits. In the three fine bottom ash fractions, the one with particle sizes between the 2.36 mm and the 4.75 mm diameter were found to contain the greatest leachable lead levels. On the other hand, the coarsest fraction with particle sizes between the 4.75 mm and 9.5 mm diameter were found to leach out lead with the lowest levels. The fine material clinging to the coarse particles were also found to leach out heavy metals with levels comparable to the three fine bottom ash fractions. The results of the total metal concentrations in the three fine bottom ash fractions indicate that metal levels generally increase with a particle size decrease. For leachable metal levels, the trend is not apparent. === Applied Science, Faculty of === Civil Engineering, Department of === Graduate