Contents of organic matter and major nutrients and the ecological effect related to land application of sewage sludge in China
中国城市污泥有机质及养分含量与土地利用

Land application is an important way for treatment of municipal sewage sludge both in China and in the world. Therefore, the contents of organic matter and nutrients in sewage sludges and their effect on promotion of plant growth have been highlighted when they are recycled in lands. There have been some systematic summaries for land application of sewage sludges in developed countries while those have not been reviewed in China though there are some specific research related to their contents of organic matter and major nutrients. Related documents about land application of sewage sludges are summarized in the paper, which focuses on the organic matter and nutrients in sewage sludges and their effects on land application. It shows from the statistical analysis of the contents of organic matter and nutrients in China's municipal sewage sludges from 29 wastewater plants that the average contents of organic matter, total N, total P and total K are 385, 27, 14 3 and 7g/kg, respectively, which are 1/3~2/3 higher than their responding contents in pig manure, respectively. It is found that the average contents of organic matter in the sewage sludges have being increased recently in China. Many supported that the sewage sludges can be applied to agriculture, forestry and horticulture because they benefit soil fertility and plant growth. It is also indicated that the contents of heavy metals have being decreased, since the last two decades. which is beneficial for land application of sewage sludges, However, the studies on harmfulness of organic pollutants and pathogens resulting from land application of sewage sludges are still limited and long term effects of their land application are needed to be understood through long term experiments in China.