Reading guidance：Most sludge fails to receive proper treatment and disposal is one of the main environmental problems faced by Chinas urban areas. Land use and land landfill, incineration and dumping sea is currently w

   Most sludge fails to receive proper treatment and disposal is one of the main environmental problems faced by China's urban areas. Land use and land landfill, incineration and dumping sea is currently widely used in the world in four ways, which especially to land for landfill and incineration is widely used. However, burning air pollution and high cost, limited land landfill areas and increasing the amount of sludge and other harmful to the environment disposal method (SEA), all of which promote the sludge land utilization, especially for agricultural use.
   International admiral sludge as fertilizer for agricultural use has 60 years of history. According to the U. S. Environmental Protection Agency statistics, 2000 and 2005 sludge disposal in the United States in addition to the proportion of land use from 55.5% increased to 58%, the proportion of incineration and landfill have declined in 2005, British sludge disposal, land use ratio of up to 66%. From the foreign way of sludge disposal.
   Our country started from 1961 to the agricultural utilization of sewage sludge, then Beijing Gaobeidian sewage treatment plant and the surrounding farmers the sludge to land. By the beginning of the 1980s, with the Tianjin Jizhuangzi sewage treatment plant put into operation, in the vicinity of the farmers will also use agricultural sludge was carried out. According to the statistic data, the proportion of agricultural I sewage sludge in the 44.83%. in 2000 to 2006 increased to about 50%. However, due to the sludge in addition to nutrient elements contain a variety of plant is necessary, there are a variety of harmful substances, such as heavy metals, organic pollutants, parasites and pathogens. Two in order to avoid the pollution to the environment, must be carried out the treatment on to satisfy the corresponding conditions before use in agricultural sludge. First of all, should be a reasonable choice of sludge treatment and disposal technology, which has saved the maximum nutrients Elements; secondly, the heavy metal content in sludge should meet the various national standards and industry standards; finally, the sludge must be strictly harmless treatment, in order to remove parasite eggs and pathogenic bacteria and so on.  
   According to the China < urban sewage treatment plant pollutant discharge standards > gb1898-2002 provisions, sludge to be the high temperature reactor rot or digestion can be used on agricultural land. Application with standards of sludge annually per mu amount not exceeding 2000kg (, calculated on the dry sludge). Sludge in any inorganic compounds close to standard, continuous on the same piece of soil application, shall not exceed 20 years.
   Urban sludge contains abundant organic matter and rich in nitrogen, phosphorus, potassium and other nutrients. The organic matter in the sludge is a good soil conditioner, it can promote the formation of granular structure, increase soil porosity, improve soil aeration, improve water and water holding capacity of soil and sludge. The nitrogen, phosphorus, potassium and other nutrients, is a good agricultural fertilizer, yield increasing effect on crops. Agricultural use of sludge can not only make full use of sludge nutrients, its resources, but also can reduce the cost of sludge treatment and agricultural production costs, therefore, for a country like China agricultural country, agricultural sludge disposal is a most promising disposal way.
   
   
 
   

：Exploration of reclamation road of sludge disposal in China ：When using sludge into agricultural field, pay attention to the control of toxic and harmful matters