Influence of Biodegradation Processes on the Duration of CaCO3 as a pH Buffer in Municipal Solid Waste Incinerator Bottom Ash
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- 作者：C. Annette Johnson and Gerhard Furrer
- 刊名：Environmental Science & Technology
- 出版年：2002
- 出版时间：January 15, 2002
- 年：2002
- 卷：36
- 期：2
- 页码：215 - 220
- 全文大小：93K
- 年卷期：v.36,no.2(January 15, 2002)
- ISSN：1520-5851
文摘
The long-term leachability of heavy metals from municipalsolid waste incinerator (MSWI) bottom ash is of concernbecause of its potential use as a secondary constructionmaterial. Calcite is the most important long-term buffer inMSWI bottom ash as it buffers solutions during percolationand is an important factor in the control of heavy-metalmobility. It has been argued that biodegradation of residualorganic material in the MSWI is a significant source ofacidity. Model calculations have therefore been carried outto determine the influence of biodegradation on thelongevity of the calcite buffer. Using the program STEADYQL,which couples thermodynamic equilibrium with kineticallycontrolled reactions, solution composition was estimatedat steady state. The concentration of Ca dissolved fromcalcite was estimated in the presence and absence ofgypsum as a function of the reaction rate of a number ofslow reactions: aerobic, ferrogenic, sulfogenic, andmethanogenic biodegradation; diffusion of O2 into thesystem; degassing of CO2 out of the system; and dissolutionof Ca silicate. It was found that, independent of the rate,the biodegradation of organic matter had little influence onthe longevity of the calcite buffer (between 2000 and3000 yr for a deposit of 1 m in depth), that anaerobicbiodegradation may have a slight retarding effect, andthat calcite dissolution due to acid input via precipitationwas negligible (around 3% of the total at reference conditionsfor rainwater with a pH value of 4.3).