我国部分城市污泥中重金属元素形态的研究

Fraction and Bioavailability of Heavy Metal Elements in Sewage Sludges

采集从北到南五家污水处理厂的消化污泥,通过室内分析测试,研究了我国部分城市污泥中重金属元素的含量和形态分布。结果表明,消化污泥总体呈高有机碳、高氮磷、低钾、高营养的相似性,但其理化性质如阳离子交换容量(CEC)、pH等差异较大,对重金属元素的形态分布与生物可利用性有影响。同种元素在不同的污泥中含量的差异较大,相差数倍甚至10倍以上;一种污泥中不同元素含量明显不同,Zn的浓度最高,其次是Cu,Cd、B的浓度最低。连续提取的形态分布研究表明,污泥pH明显影响污泥中重金属元素的形态分布,酸性污泥(S5样品)中各重金属元素酸溶/交换态百分比明显高于其他污泥。不考虑pH因素影响,Cu、Cd、Cr和Pb主要分布在残渣态和氧化态,其酸溶/交换态和还原态含量较低;Zn、Ni和B分布受污水处理厂污泥性质影响较大,各态均有较高分布,一般高于10%,有效态含量高,生物可利用性和植物毒性较大。

With the rapid increase of sewage treatment plants, agricultural use of sewage sludges produced during sewage treatment had been paid more and more attention. Sewage sludges were collected from five wastewater treatment plants from north to south of China and the total contents of mineral elements and their fractions were investigated by a sequential extraction. The sewage sludges similarly contained high organic carbon, high content of N, P and low K concentration, but their physical- chemical properties such as pH and CEC varied greatly. There existed significant differences in metal content among different sludge samples. Generally, content of Zn was highest, and then Cu and Cr, and B, Cd concentration was lowest in all sludge samples. The fractions obtained by the sequential extraction procedure indicated that the pH value of sludge had great effect on the metals fraction, and in acid sludge from Xiamen wastewater treatment plant (pH4.4), the percentage of acid soluble/exchangeable fraction was much higher than others. Cu, Cd, Cr and Pb were principally distributed in the oxidizable fraction and residual fraction. The content of Zn, B and Ni accounted for more than 10% of the fractions, and had good mobility and bioavailability. A statewide survey for the quantitative data of sewage sludge production should be carried out to provide basic assessment for disposal in China.