Heavy metal release from different ashes during serial batch tests using water and acid

Most ashes contain a significant amount of heavy metals and when released from disposed or used ash materials, they can form a major environmental concern for underground waters. The use of water extracts to assess the easily mobilisable content of heavy metals may not provide an appropriate measure. This study describes the patterns of heavy metal release from ash materials in context with results from the German standard extraction method DIN-S4 (DIN 38 414 S4). Samples of four different ashes (municipal solid waste incineration ash, wood ash, brown coal ash and hard coal ash) were subjected to a number of serial batch tests with liquid renewal, some of which involved the addition of acid to neutralize carbonates and oxides. Release of heavy metals showed different patterns depending on the element, the type of material, the method of extraction and the type of the extractant used. Only a small fraction of the total heavy metal contents occurred as water soluble salts; of special significance was the amount of Cr released from the wood ash. The reaction time (1, 24 or 72 h between each extraction step with water) had only a small effect on the release of heavy metals. However, the release of most of the heavy metals was governed by the dissolution processes following proton inputs, indicating that pH-dependent tests such as CEN TC 292 or others are required to estimate long-term effects of heavy metal releases from ashes. Based on the chemical characteristics of ash materials in terms of their form and solubility of heavy metals, recommendations were made on the disposal or use of the four ash materials.     

Planning for environmental project implementation and development: as exemplified by the songklha lake basin planning study,Thailand

Summary This paper describes use of the economic-cumenvironmental regional development planning process (as differentiated from regional economic planning and regional environmental planning) for its first application in the Asia-Pacific region, for The Songkhla Lake Basin Planning Study, in southern Thailand. The study project was carried out, with Asian Development Bank (ADB) loan financing, as a joint venture of the national economic and national environmental planning agencies. Because of its pioneering nature, in both technical and institutional aspects, numerous lessons were learned from the project. These are described, and yield guidelines valuable for future studies of this type.Dr Harvey F. Ludwig, Chairman of Seatec International Consulting Engineers in Bangkok, has a unique record of distinguished experience in environmental engineering. This includes, in addition to his present role, experience as a professor at the University of California at Berkeley, in research (four USA national awards), in government (as Assistant Chief Engineer of the US Public Health Service Engineering Group, the predecessor to USEPA), and with numerous international assistance agencies including the World Bank, ADB, and many UN affiliates. Dr Ludwig moved to live in Bangkok in 1973 and has since been a continuing adviser to the National Environment Board of Thailand and to the Institutes of Water Resources Research of Indonesia. He is the author/coauthor of some 160 professional publications and the senior author of a textbook onEnvironmental Technology in Developing Countries, now being printed by CRC Press of Boca Raton, Florida. His work record includes projects in more than 30 Developing countries.