| Summary: | 碩士 === 輔英科技大學 === 環境工程與科學系碩士班 === 99 === Pretreatments on the Leaching Behaviour of
MSWI Bottom Ash
Abstract
Toxicity characteristic leaching procedure (TCLP) has been the primary environmental validation protocol for reused MSWI bottom ash in Taiwan. Nevertheless, TCLP is originally developed for the identification of hazardous wastes; it is not suitable for the investigation of the leaching potential of recycled products. In order to evaluate long term leaching potential and environmental risk of heavy metals from reuse of MSWI bottom ash; percolation test (CEN 14405), pH dependent test (CEN 14429), availability leaching test (NEN 7341) were conducts on the MSWI bottom ash with pretreatments (water-washed and phosphate acid pretreated). Immissions of ashes were calculated and compared with Building Material Decree (BMD). Also leaching of heavy metals to the soil was simulated with LeachXS-Orchestra expert system for the risk assessment.
Results show that MSWI bottom ash sampled (BAB) contain majorly silica, calcium, aluminum and iron elements. TCLP results show that BAB meets the Taiwan current regulation standard. Observation on the water-washed bottom ash (BAW) and phosphate acid treated bottom ash (BAP) shows that pretreatment with phosphate acid could effectively reduce the leaching concentration of Zn to 1.61 mg/L. Calculations from the percolation data indicate that immission could meet BMD category I and category II standard, though small amount of Mo and Sb might leach out from BAB and BAW, and tiny amount of Sb might leach out from BAP. Further comparison on the stabilization of heavy metal ability reveals that BAP>BAW>BAB. Simulation with LeachXS-Orchestra expert system indicates though Mo and Sb could penetrate the underneath soil layer, the concentrations are insignificant. Other element such as As,Cd,Ni,Pb and Zn are confined in the surface layer of soil ( 0 cm ~ 50 cm). In conclusion, stabilized MSWI bottom ash is environmental compatible, and it could be reused as recycled products.
Key words: Pretreatments, MSWI bottom ash, Leaching behaviour,
LeachXS-Orchestra.
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