Abstract:
Heavy metal is one of the major limiting factors for applications of the sewage sludge to the agricultural land. In this study, we collected the published data concerning the concentrations of heavy metals in the sewage sludge all over China from literature databases, then analyzed all the data and summarized the concentration characteristics of heavy metals and their historical changes in the past 30years. The results showed that the median concentrations of Cd, Pb, Cr, As, Hg, Cu, Ni and Zn in the sewage sludge were below the permissible limits regulated by the “Discharge standard of pollutants for municipal wastewater treatment plant” of China (GB 18918-2002). In 1980-1989, about 25% of Cd, Cu, Ni and Zn concentrations and 10% of Cd, Pb, Hg, Cu, Zn and Ni concentrations in the sewage sludge were higher than the standard; In 1990-1999, about 25% of Ni concentrations in the sewage sludge was higher than the standard, while 10% of Cd, Pb, Cr, Hg, Cu, Ni and Zn concentrations in sewage sludge were over than the standard; In 2000-2010, about 25% of Ni concentration and 10% of Cd, Cr, Hg, Cu, Zn and Ni concentrations in the sewage sludge was higher than the standard. In the last three decades, concentrations of Cd and Cu in the sewage sludge decreased gradually with the time progressing. According to the databases in the last decade, Ni,Cd and Hg should be taken as primary considerations in the pollution source control of heavy metals in the sewage sludge.