Reading guidance：Reading guidance : in recent years, with rapid development of urbanization, our country has got its sludge disposal scale enlarged gradually. Sludge problems are getting worse an worse and needed to be

      In recent years, energy-saving and pollution control work have been paid more and more attention to. A series of policies have been carried out to improve these two works, which makes sludge disposal work popularized to some extend. Sludge disposal efficiency gets improved. Sludge disposal degree gets deepened. Therefore, sludge production amount is increased rapidly. According to relevant data, wet sludge production amount in our country’s sewage disposal plants reaches to about 20000000 tons. Sludge disposal is a urgent problem to be solved. In recent 10 years, owing to investment, running technology and technical level, sludge disposal adopts simple dehydration outward transport. This method pays no attention to where the sludge goes. Some areas adopts digestion disposal methods and leaves sludge piled outside and removed casually. Some use sludge as fertilizer without consideration of heavy metals content. Sludge disposal has become a bottleneck problem concerning healthy development.
     In sewage disposal factories, landfill method is adopted mainly, but caused many problems. It consume a lot of land resources and it is difficult to find new landfill places for many cities. Many landfill places are without cover. After rainy days, sludge will restore its original qualities without harmless and stable disposal and cause severe harm to landfill place. Without proper disposal methods, sludge will cause severe blockage to percolation system of landfill places and cause severe pollution to underground water. Owing to high moisture content of sludge, percolation liquid of garbage landfill will cause more pollution. There is a phenomenon for most garbage landfill places which adopts mixing landfill to refuse to accept sludge. There are very fewer garbage landfill places which use gas produced from landfill as a kind of resources. Gas produced from landfill will not cause pollution to environment, but lead to hidden danger.
     Indirect or direct land utilization has become one of the main solutions for sludge. Sludge can promote the growth of plants because of its rich nutrient elements and micro elements. Therefore, sludge can be used as fertilizer to improve soil fertilizer. However, owing to lack of systematic, scientific management and control standard, sludge may become a pollution source because of unreasonable disposal. The security of land utilization of sludge is doubted by people. Building materials application of sludge is a way of sludge reclamation which mainly includes making bricks, cement, ceramicite, glass and biochemical fiber by using sludge and its incineration products. At present, building materials applications has become a sustainable disposal method for sludge. 

：Should our country advocate land utilization of sludge? ：What is the next step for printing and dyeing sludge after disposed?