Study on zero-emission treatment methods for dioxins and other hazardous organics in river water and sediment

研究了日本大坂纪津河和住吉河污染表层沉积物中二恶英含量的粒度效应。样品中二恶英含量随粒径的减小而增加，粒径小于20μm的样品中二恶英含量最高。在较小的粒度级二恶英浓度较高是由于较大的有机碳含量。研究了沉积物粒径对间接热脱附法修复多环芳烃（PAHs）、二恶英（Dioxins）和多氯联苯（PCBs）污染沉积物的影响。粒径较大的有机质组分比粒径较小的组分更容易蒸发，这是由于有机碳含量较大，有机质与有机碳之间的结合力增强所致。较小尺寸部分中的有机物降解，因此在继续加热时蒸发。这些结果表明，粒度分布对沉积物中有害有机物的含量和间接热解吸法修复污染沉积物的意义。从结果中可以明显看出，以粒度分离为基础的适当方法应比传统方法更能有效地补救受污染的沉积物。还研究了微滤法去除受污染沉积物水中二恶英的效果。混凝-微滤联用技术几乎可以完全去除沉积物-水中的二恶英。此外，高级氧化技术如臭氧氧化、臭氧氧化和光催化臭氧氧化等对水和废水中难降解有机物的降解和矿化非常有效。

Effect of grain-size on dioxin contents in contaminated surface sediment samples obtained from Kizu and Sumiyoshi Rivers in Osaka, Japan, was investigated. Dioxin contents in the samples increased with smaller grain-size fractions, and less than 20μm fraction had the highest dioxin concentrations. The higher dioxin concentrations in smaller grain-size fractions were due to bigger organic carbon contents. Influence of grain-size on remediation of sediments contaminated with hazardous organics like polycyclic aromatic hydrocarbons (PAHs), dioxins and polychlorinated biphenyls (PCBs) by indirect thermal desorption method was also investigated. The organics in bigger grain-size fractions evaporated easily than those in smaller-size fractions due to bigger organic carbon contents resulting in increased binding force between the organics and organic carbon in the latter. The organics in smaller-size fractions degraded, and consequently evaporated on continued heating. These results did indicate the significance of grain-size distribution on the contents of hazardous organics in sediments, and remediation of contaminated sediments by indirect thermal desorption method. It was evident from the results that appropriate methods based on grain-size separation should be more relevant than the conventional approach for effective remediation of contaminated sediments. Removal of dioxins from contaminated sediment-water by microfiltration was also examined. Almost a complete removal of dioxins from the sediment-water was achieved by combined coagulation and microfiltration. In addition, advanced oxidation processes like photocatalysis, ozonation and photocatalytic ozonation were very effective for degradation and mineralization of recalcitrant organics present in water and wastewater.