Decision-Making Process for MSWI Bottom Ash Utilization
Date Issued
2006
Date
2006
Author(s)
Huang, Chin-Ming
DOI
zh-TW
Abstract
The Taiwan Environmental Protection Administration has studied the treatment and reuse of MSWI ashes for many years and collected references on international experience accumulated by developed nations for establishing policies on treatment and reuse of MSWI ashes. The total number of incinerators is expected to increase to 27 with treatment capacity of 27,450 tons per day in service, operated daily to generate about 6,500 tons of incinerator bottom ash and 1,500 tons of incinerator fly ash, serving almost all cities in Taiwan by 2007. The citations were analyzed as the basis for current governmental decision making on policies and factors to be considered for establishing decisions on recycle and reuse of MSWI ashes. Feasible applications include utilization of ashes, which after sieving and separation of metal particles, produce secondary construction materials. When secondary construction materials comply with TCLP limitations, they can be utilized as cement additives, asphalt aggregate or road base. The decision making procedures of evaluation have been proposed in the performance criteria, health risk assessment, ecological risk assessment, to be included in the proposed process of ash utilization.
This study was associated with the assessment of CLSM with bottom ash. The assessment method that combines engineering criteria and risk assessment, then be used to select the available substitution ratio for practice. The results were showed best condition was C/W 0.4, W/S 0.35∼0.40. Therefore, the achievements of the study could serve as the basis for the decision making and risk management related to reuse of bottom ash. The health risk assessment of CLSM with bottom ash were evaluated, the cancer risk of exposure route under construction and road service was lower than 10-6, and hazard quotient for noncancer was lower than 1.
The physical and environmental properties of asphalt mixtures using various incinerator bottom ash as fine aggregate substitution were investigated. The Marshall mix design method was used to determine the asphalt content and evaluate the potential performance of IBA–asphalt mixtures. Leachates, from laboratory and outdoor leaching tests, were measured the concentration of heavy metals and daphnia toxicity. While with adequate Marshall stability, the IBA–asphalt mixtures were shown to have excessively high Marshall flow and excessively low VMA. The results of the wheel tracking tests indicated that the mixtures had low rutting resistance. The results of the water sensitivity test showed that the mixtures had a higher tensile strength ratio. Considering the environmental compatibility, the outdoor leachates showed that IBA had a high level of daphnia toxicity. From the ecological risk perspective, IBA could be identified as hazardous waste. However, after being mixed with asphalt, the concentration of heavy metals and the levels of daphnia toxicity were significantly reduced. The leachates of 10-day flat plate leaching tests indicated that the heavy metal were undetectable and the daphnia toxicity was ineffective. The IBA substitution rate would be suggested as less than 25% for surface course and less than 50% for base course
To address public concerns, TEPA has adopted stringent regulations to reduce risk in bottom ash utilization and minimize the emission of pollutants in the flue gas from MSWI. In addition to providing technical guidelines for bottom ash utilization, TEPA has initiated the demonstration projects for obtaining field data to affirm the utilization policy and to revise the technical criteria, if needed. In this way, risk in the whole utilization process will be minimized, and the benefit and cost-effectiveness of the selected strategies on utilization will be maximized. The author offers the decision making process for the utilization of bottom ash with the engineering specification, environmental risk and ecological risk.
Subjects
健康風險評估
生態風險評估
CLSM
瀝青混凝土
水蚤毒性試驗
環境相容性
決策程序
health risk assessment
ecological risk assessment
asphalt concrete
daphnia toxicity
environmental compatiblity
decision making process
Type
thesis
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