EVALUATION OF ELUSION RATE OF ALKALINITY FROM BOTTOM ASH FOR A LONG TERM PERIOD

The pH in a landfill layer affects many phenomena such as dissolution/precipitation and adsorption/desorption of heavy metals, activities of microorganisms, CO2 absorption/emission etc. However, because of a lack of knowledge about the leachate characteristics after closing a landfill site, some inhabitants around a landfill site that has been constructed or is under consideration are anxious about the environmental safety of the landfill site, and often oppose the construction of a new landfill site. Therefore, it is very important to predict the pH change for a long term period for the management of a landfill site after closing. In order to predict the pH in a landfill layer, it is necessary to know the total amount of alkali and acid and their supply and consumption rates.

In order to evaluate the alkali elution rate from MSW incinerator bottom ash for a long term period, sequential leaching test of 6 sizes of sieved ashes was conducted with nitric acid as a solvent. The pH of the solvent was stepwise changed to 1.7, 2.7 and 4. After changing the pH of the solvent to 4, for a leaching time of more than 2 days the pH of the leachate remained constant, at about 7 for any particle size of bottom ash. The elusion rate of total alkalinity (RA) was affected by leaching time. RA was kept constant at 2-1*10-2 mmol/g/d for a leaching time of 1 day and 5-4*10-3 mmol/g/d for a leaching time of more than 2 days, for any particle size. It is suggested that alkali dissolution could be the rate control process of alkali elution for a long term period.



Copyright: © IWWG International Waste Working Group
Quelle: Specialized Session D (Oktober 2007)
Seiten: 6
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Autor: Y. Dote
T. Sekito

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Leichtweiß-Institut
Physikalische und biologische
Aufbereitungs- und Behandlungs-
technologien, TU Braunschweig