Mechanisms of heavy metal stabilization during sludge drying
污泥干化使重金属形态变向稳定的原因分析

During a number of drying experiments of different types of sludge under different drying temperatures, the forms of heavy metals in sludge as well as other properties of the sludge such as moisture content, density, temperature and electrical conductivity were monitored and analyzed. The results show that the original distributions of heavy metals among various forms in the tested sewage sludge are quite different, depending on sludge types and sources. However, the drying process tends to stabilize the heavy metals by transforming the acid-soluble, the reducible and the oxidizable heavy metals into the residue heavy metals. Such transformation and stabilization are mainly caused by the changes of sludge properties associated with decomposition of organic matter and sulfide. The findings are not only improved our understanding of the environmental geochemical behavior of heavy metals in sewage sludge, but also provide a scientific foundation for environment-friendly disposal of sewage sludge.