Evaluation of soil and groundwater contamination from molten slag generated from solid waste by column test

Abstract Generation of molten slags will increase more accompanied with recently or newly built melting furnaces for industrial or municipal solid waste. Slags are utilizable for construction materials like a road subbase or a filling material. However, prior their utilization it is necessary to evaluate an environmental impact on a soil/groundwater system. This paper describes an estimation of groundwater contamination in utilization of molten slags (slags from automobile shreddered dust and municipal solid waste, and electric arc furnace slag) in the environment by column tests using a simple model proposed by Hjelmer et al. sup8). In addition according to the concept of the newly enacted soil pollution control law, taking into account of the risk of direct ingestion, the testing method of acid extraction is applied to the molten slags. In the column test a typical elution pattern of most elements was an early washout and the next diffusion leaching, while different patterns were observed in several elements; silicon was affected by the pH of the leachate and barium concentration increased gradually. Thus the released amount by a column test was generally a little more than that by the batch-type leaching test (the Japanese Leaching Test No. 46 ; JLT 46) under the same liquid/solid ratio of 10. This might indicate the JLT 46 method give an effective estimation result as well as a column test. Such toxic heavy metals as lead and arsenic were estimated not to be influential to make groundwater quality of interest increase up to the Environmental Quality (EQ). Easily soluble elements like sodium might affect 65% on the maximum of the EQ. An alkaline electric arc slag released calcium highly, and the estimation showed a possibility of an increase Ca concentration over the tap water quality (200 mg/L) in a severe condition. The ratios of "quasi-total" or "effective" contents using HCl extraction to the true total content of almost all elements were analogous in the same slag sample. This indicates the decomposition of silicate network by acid made the release of Si and also cationic modifier ions.