Document Type

Article

Publication Date

10-15-2013

Keywords

municipal solid waste incineration bottom ash, heavy metals, leaching, accelerated moist carbonation, accelerated pressurized slurry carbonation, ageing, heat treatment

Abstract

This study compared the performance of four different approaches for stabilization of regulated heavy metal and metalloid leaching from municipal solid waste incineration bottom ash (MSWI-BA): (i) short term (three months) heap ageing, (ii) heat treatment, (iii) accelerated moist carbonation, and (iv) accelerated pressurized slurry carbonation. Two distinct types of MSWI-BA were tested in this study: one originating from a moving-grate furnace incineration operation treating exclusively household refuse (sample B), and another originating from a fluid-bed furnace incineration operation that treats a mixture of household and light industrial wastes (sample F). The most abundant elements in the ashes were Si (20 to 27 wt.%) and Ca (16 to 19 wt.%), followed by significant quantities of Fe, Al, Na, S, K, Mg, Ti, and Cl. The main crystalline substances present in the fresh ashes were Quartz, Calcite, Apatite, Anhydrite and Gehlenite, while the amorphous fraction ranged from 56 to 73 wt.%. The leaching values of all samples were compared to the Flemish (NEN 7343) and the Walloon (DIN 38414) regulations from Belgium. Batch leaching of the fresh ashes at natural pH showed that seven elements exceeded at least one regulatory limit (Ba, Cr, Cu, Mo, Pb, Se and Zn), and that both ashes had excess basicity (pH > 12). Accelerated carbonation achieved significant reduction in ash basicity (9.3–9.9); lower than ageing (10.5–12.2) and heat treatment (11.1–12.1). For sample B, there was little distinction between the leaching results of ageing and accelerated carbonation with respect to regulatory limits; however carbonation achieved comparatively lower leaching levels. Heat treatment was especially detrimental to the leaching of Cr. For sample F, ageing was ineffective and heat treatment had marginally better results, while accelerated carbonation delivered the most effective performance, with slurry carbonation meeting all DIN limits. Slurry carbonation was deemed the most effective treatment process, achieving consistently significant leaching stabilization, while also effectively washing out Cl ions, a requirement for the utilization of the ashes in construction applications. The benefits of carbonation were linked to the formation of significant quantities of Ca-carbonates, including appreciable quantities of the Aragonite polymorph formed in the slurry carbonated samples.

Comments

5 August 2016: At the time of publication, Sheridan College author Rafael M. Santos was associated with the Katholieke Universiteit Leuven in Belgium.

Faculty

Faculty of Applied Science & Technology

School

School of Chemical and Environmental Sciences

Journal

Journal of Environmental Management

Version

Pre-print

Peer Reviewed/Refereed Publication

yes

Terms of Use

Terms of Use for Works posted in SOURCE.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Original Publication Citation

Santos, R. M., Mertens, G., Salman, M., Cizer, Ö., & Van Gerven, T. (2013). Comparative Study of Ageing, Heat Treatment and Accelerated Carbonation for Stabilization of Municipal Solid Waste Incineration Bottom Ash in View of Reducing Regulated Heavy Metal/metalloid Leaching. Journal of Environmental Management, 128, 807-821. doi:10.1016/j.jenvman.2013.06.033

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