Characteristics of Residue Organic Compounds in Municipal Solid Waste Incineration Bottom Ash
Date Issued
2011
Date
2011
Author(s)
Lin, Yen-Ching
Abstract
Although heavy metals in bottom ash have been a primary issue in resource recovery of municipal solid waste incinerator residues in past decades, less studied are potentially toxic and odorous organic fractions that exist as they have not been completely oxidized during the mass burn process.
The organic carbon residues contained in municipal solid waste incineration bottom ash (MSWIBA) can be categorized into elemental carbon, extractable organic carbon and non-extractable organic carbon. The data showed the fraction of extractable organic carbon by water and dichloromethane are 110–1,670 mg kg-1 and 0–842 mg kg-1, respectively. The non-extractable organic carbon is in the range of several grams per kg of bottom ash, indicating most of the organic carbon residues are not easily water extractable. Therefore, there is a need to reveal the spectrum of the organic carbon residues in MSWIBA and to evaluate the effectiveness of using water washing as a pre-treatment process for reducing the environmental risk of the organic residues when recycling MSWIBA. In this work, two extraction techniques, soxtec extraction (SE) and supercritical fluid extraction (SFE), were employed for the full spectrum of the organic carbon residues in MSWIBA before and after pre-treatment with water washing. Although organic compounds in raw bottom ash of different seasons extracted by SE and SFE showed obvious variability, organic compounds in water-washed bottom ash of different seasons extracted by SE and SFE showed noticeable stability.
The major organic compounds such as phenols, chloro-organics and carboxylic acids in the weathered and water-washed bottom ash were quantitatively determined by GC-MS and those in washing water were determined with GC-MS after liquid-liquid extraction. For all the bottom ash samples, a total of 149 compounds were foun from weathered bottom ash and a total of 40 compounds were found from water-washed bottom ash. Organic compounds in water-washed bottom ash such as aliphatics, aliphatic amines, aromatic amines and aromatic compounds extracted by SFE and SE from different incinerators distributed over similar frequency and it was much lower than organic compounds in weathered bottom ash.
The results of quantification demonstrated that fewer organic compounds were detected in water-washed bottom ash extraction with SFE and only one chloro-organic was identified from water-washed bottom ash by SE. It indicates the effectiveness of water washing as pretreatment for organics such as several phthalates (e.g., phthalic acid isobutyl tridec-2-yn-1-yl ester, dibutyl phthalate and 2-butoxyethyl butyl benzene-1,2-dicarboxylate), organic phosphates (e.g., octicizer and phosphoric acid isodecyl diphenyl ester), aromatic amines (e.g. 1-nitro-9,10- dioxo-9,10-dihydro-anthracene-2-carboxylic acid diethylamide and 3-bromo-N- (4-bromo-2-chlorophenyl)-propanamide) and aromatic compounds (other than amines) (e.g. 7-chloro-4-methoxy-3-methyl- quinoline and 2,3-dihydro-N- hydroxy-4-methoxy-3,3-dimethyl indole-2-one). The results here suggest that washing with water can be an effective pre- treatment step for removing odour-causing and environmental concerned organics.
Subjects
Bottom ash
Water washings
Organic residue
Supercritical fluid extraction
Soxtec extraction
Odour
Type
thesis
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