DEVELOPMENT OF A QUICK LEACHING TEST FOR MONOLITHIC MATERIALS BY USING FACTORIAL DESIGN

A quick leaching test procedure for monolithic waste materials has bee n developed by a Nordic expert group using experimental factorial desi gn. The Dutch quick leaching test proposal in which the wetting time o f the test specimen is reduced by applying vacuum was chosen as a star ting point. The influence of the following parameters were studied: va cuum, stirring, open or closed vessel, water renewal frequency, leacha nt quality and laboratory or batch differences. The study was performe d with test specimens prepared from a cement stabilised soil containin g As, Cr and Cu. The test specimens were immersed in water and the wat er was renewed at certain time intervals. The study clearly showed tha t the use of vacuum had a strong effect on the release rate and that t he open vessel lowered the pH-values of the eluates due to uptake of c arbon dioxide in the water. The results also indicate higher emissions when stirring was applied. The following test conditions are recommen ded: application of vacuum prior to testing, use of closed test vessel , use of stirring, a test time of 3 days with four water renewals afte r 15 min vacuum steps, and then after e.g. 2 h, 23 h and 3.2 days, use of demineralised water as leachant. The amount of water must be selec ted according to the size of the test specimen. A liquid to surface (L /A) ratio of 5-10 ml cm(-2) is recommended. All four eluates collected are filtered and analysed. (C) 1998 Elsevier Science B.V. All rights reserved.