Contaminated water from abandoned mines, non-sanitary landfills, and tunnel excavation flows into rivers via groundwater. These sources of contamination contain significant heavy metals and are discharged without treatment. As contaminated water flows into the river, water quality decreases. Furthermore, water that flows into rivers also contaminates the soil. This causes problems for both the environment and society. However, it is difficult to place water treatment plants at each source of contamination because of problems related to economics, site security, etc. The author has selected permeable reactive barriers (PRBs) to solve these problems. The aim of this study is to develop eco-friendly technology for reuse of waste. In this study, three reacting media were used. The first reacting medium was zero-valent iron (ZVI). ZVI can be used as a PRB and is effective at removing heavy metals. The second medium was steel-making slag. It is suitable for removal of heavy metals because its components include lime and iron oxide. The final reacting medium was bark. The bark is the outer layer of a tree, and consists of dead tree trunk tissue. The chemical structure of bark includes carboxyl and hydroxyl moieties that combine well with heavy metals. In this study, the materials to be removed were heavy metals including arsenic, cadmium, copper, lead, zinc, and nickel. The experiment was carried out for two months using two pilot scale PRBs. ZVI and steel-making slag were placed on the front of the two pilot scale PRBs under the same conditions. Activated carbon and bark were placed on the end of each device. After two months, the experiment showed efficient removal of arsenic and lead. It is possible to reduce the generation of waste by removing heavy metals with waste materials like bark.

The dechlorination of chlorinated methanes by iron powder and palladium coated iron (Pd/Fe) was studied in batch experiments. Iron powder dechlorinated carbon tetrachloride (CT) with a half-life of 4 days. Three chloromethane was found as major product and less chlorinated daughters. Mass balance found was to be about 93-99%. Pd/Fe showed very enhanced reactivity for CT in comparing with plain iron. The major dechlorination products of CT were also less chlorinated methanes with Pd/Fe. Pd/Fe also degrade the produced less chlorinated compounds. Sequential reactions were occurred on Pd/Fe. As the Pd/Fe content increased, the reaction rate was increased linearly.