熟化處理對都市垃圾焚化底渣中重金屬之影響

Effect of Different Aging Processes on the Leaching Characteristics of Heavy Metals in the Bottom Ashes from the Municipal Solid Waste Incinerators

本研究利用自然熟化、加速熟化兩種方法，分別將細粒徑(≤4.75mm)劃凶底渣樣品於靜置貯存、浸漬水中與飽和石灰水等不同條件下進行熟化處理，探討自然熟化及加速水化反應將底渣穩定化之效能。研究過程採用毒性特性溶出程序(Toxicity Characteristic Leaching Procedure, TCLP)、歐美國EPA SW-846 Method 1320 (Multiple Toxicity Characteristic Leaching Procedure, MTCLP)、歐盟管柱滲出試驗(CEN/TS 14405)及逐步萃取法(Sequential Extraction Procedure, SEP)，探討底渣中重金屬之溶出特性，並參照我國毒性特性溶出標準及荷蘭建築材料之法規標準(BMD)。研究結果得知分選後底渣雖整體而言都符合我國法定溶出標準，但發現自然熟化後底渣重金屬Cu、Zn的溶出並無因長時問貯存而降低反而有逐漸增加之趨勢，顯示底渣經長時問的貯存仍無法確保其穩定度。另外，雖TCLP及MTCLP實驗結果顯示符合現行毒性特性溶出標準，但比較歐盟整合環境性試驗方法標準與參照荷蘭建築材料之法規標準，發現仍有部分重金屬超出BMD標準值之外，其中重金屬Cu之累積溶出量，無論採自然熟化或加速熟化皆遠高於歐盟現今法規標準值。另外，由逐步萃取法得知本研究之底渣中各種金屬鍵結型態多屬不易移動之型態。

To reduce the environmental impact during the utilization and disposal of bottom ash from municipal solid waste incinerator (MSWI), the leachability of the heavy metals in the ash should be taken into consideration. in the present work, different curing processes have been used for stabilization of heavy metals in bottom ashes. To understand the effects of different curing processes on the leaching characteristics of heavy metals in the bottom ash from MSWI, bottom ash with particle size less than 4.75 mm diameter was stabilized by natural and accelerated aging. In natural aging process, the bottom ash was posed in the ambient air condition. In accelerated aging processes, ashes were soaked in tape water and saturated lime solution. Toxicity characteristic leaching procedure (TCLP), EPA SW-846 Method 1320 (Multiple Toxicity Characteristic Leaching Procedure, MTCLP), column test (CEN/TS 14405) and sequential extraction procedure (SEP) were used to evaluate the leaching characteristics of heavy metal and chloride ion in the aged bottom ashes. It was found that leaching of heavy metals in naturally aged bottom ash was not reduced with increasing curing time. However, leaching of heavy metals in accelerated aging bottom ash declined with increasing curing time. in addition, based on the TCLP, MTCLP and column test results of aged ashes through natural aging and accelerated aging processes, it was found that the heavy metals leachability can meet the requirement of TCLP standards in Taiwan, but results based on column test elucidates the bottom ash had some problems in the long-term stability. The accumulation leachability of Cu and Pb can't meet the requirement of building materials decree (BMD) standards of Netherlands. According to the SEP analysis, mainly bounded patterns of the heavy metals in the aged ashes through natural aging and accelerated aging processes are Fe-Mn oxides bound, organic matter bound and residual bound.