Abstract: Municipal sludge is rich in organic matter and nutrients for plant growth such as N, P and K. But it can not be directly used in agriculture as a result of the contamination of heavy metals. In this paper, the origins, characteristics and hazards of heavy metals in municipal sludge are described briefly. The removal and stabilization methods of sludge including chemical, biological, physical and the combination methods, are discussed emphatically. The effects of the methods on the speciation and removal efficiency of heavy metals in sludge treatment process are analyzed. In addition, the merits and weaknesses, influence factors and application scope of these methods are compared. The results show that the speciation of heavy metals is the most critical factor that influences the removal of heavy metals from municipal sludge. There are great difference in the speciation of heavy metals to distribute in sludge and the most of heavy metals existing in stable or relatively stable state, which leads to low efficiency of physical and biological method on heavy metals removal. It is noteworthy that microbial method and lower animals treatment has a better adaptability compared with plant method owing to the limit of space and time. Although heavy metals both in oxidizable and reducible speciation could be effectively transformed and removed, the electric energy consumption is quite outstanding due to the domination of heavy metal transfer from sludge into liquid phase. At present, chemical extraction is currently the best method. It is, however, difficult to utilize treated sludge due to nutrient loss and acid ions accumulation of raw sludge. Consequently, jointly using all kinds of processing technologies in order to improve the removal efficiency of heavy metal from sludge under the premise of land use remains to be further research.

Key words: municipal sludge, waste treatment, heavy metal pollution, removal, stabilization, morphological changes, electrochemistry

摘要： 城市污水处理厂污泥产生量大，含有丰富的有机质、氮、磷、钾等农作物所需营养物质，但由于受重金属的污染使污泥无法直接农用。本文简述了城市污泥重金属的来源、特点及危害。重点论述了城市污泥中重金属去除和稳定方法，包括化学法（电化学法、化学试剂法）、生物法（微生物法、植物法、低等动物法）、物理法（超临界流体萃取、微波和超声）及联合技术。分析了各种方法处理污泥重金属过程中重金属的形态变化及其对处理效果的影响，对比各种方法的优缺点、影响因素及适用范围。指出污泥中重金属形态分布是影响去除效果的关键因素，污泥中重金属形态分布差异性大，且大部分重金属以稳定或相对稳定的状态存在，导致物理法和生物法去除效率较低，微生物和低等动物处理法相比植物法（备受时空限制）则表现出更好的适应性；电化学法对可氧化、可还原态分布的重金属都能起到较好的转化去除作用，但往往受由污泥向污泥液相中转移过程的控制，电损耗较突出；化学试剂浸提剂是目前效率较高的方法，但强酸环境常导致污泥营养物质流失和酸根离子累积，农用时容易板结而不利于污泥土地利用。因此，以土地利用为前提的条件下，将各种处理技术联合运用以提高污泥重金属去除率有待于进一步研究。

关键词: 城市污泥, 废物处理, 重金属污染, 去除, 稳定, 赋存形态, 电化学