Study On Sludge Solidification And Sludge Incineration And Their Heavy Metal Leaching

Although sewage sludge is only a small fraction of the total, but the sludge disposal costs are high.With the accelerated urbanization process and people's living standards, China's sludge production is also rising and the sludge treatment requirements are also rising.However, due to inadequate attention to sludge treatment, lax regulatory and other reasons, led to our current level of sludge treatment can't reach the requirements of social development. China's current sludge treatment is in a simple agricultural and landfill-based, but without the rigorous treatment of the sludge used for agriculture will cause secondary pollution problems. High moisture content of the sludge, organic matter content, characteristics and poor mechanical properties will caused the landfill collapse for landfill.The current landfill has basically does not allow direct sewage sludge landfill.With the development of the society,the sludge treatment problems have become increasingly serious.To solve above problem, this paper researched the sludge solidification and sludge incineration.Detailed contents are as follows:(1)In this paper, on the basis of the traditional curing sewage sludge only in cement, adding clay as aggregate, it is a new sludge solidification method. The strength added to the cement and clay in the sludge compared to the strength only added cement is improved significantly.This shows that the clay played a very good framework effect on the sludge and increased the strength of the cured sludge.In the case of low clay incorporation,with the increase of the addition amount of clay the sludge strength is increasing;when the mixed with clay more than a peak,With the increase of the addition amount of clay the sludge strength is decreasing.This is because the clay is too much,the hydration products of cement is not enough to response completly to the clay,which led to the sludge strength is decreasing.The peak will be change with the change of the cement.The method is simple and can effectively improve the strength of the sludge, it cost lower than simply add cement and has good economic value, but when add too much material, it will affect the volume of solidified sludge to increase the processing cost.It should choose the best option based on the actual situation, to achieve reasonable results.(2)The cured sludge stabilize heavy metals in the sludge by the physical effect, chemical and biological effects.By changing the size of sludge,the pH and Eh of leaching solution can be found, when the cured sludge was crushed the physical sealing effect was affected.This is caused mainly because the microstructure of hydration products was damaged. When the sludge particle size less than 1.0mm, the physical sealing effect gradually weakened; when less than 0.15mm, the physical sealing effect largely ineffective, since the stability of heavy metals are mainly chemical stability.The lower the pH and higher Eh,the higher leaching rate of heavy metal of cured sludge. When the sludge was cured, on the one hand it can increase the sludge's pH and decrease it's Eh;On the other hand,it can effectively resist the change of sludge pH and Eh, play a buffer role. When the sludge was cured, on the one hand itcan effectively inhibit microbial (mainly sulfur bacteria) activity; on the other hand it also have a certain resistance to the invasion of the role of the microorganisms (mainly sulfur bacteria). When the amount of the micro-organisms are no more than a certain amount,the microbial activity will not affect the leaching of heavy metal generally.(3)The incineration on final disposal of sludge is the most effective and thorough way, especially the high content of organic matter in the sludge when the method is more suitable than other methods.The sludge and coal was mixed to improve the calorific value of mixed sludge,to achieve the power plant's requirements for power plants.The program not only deal with the sludge, protect the environment, but also develop the sludge's use value, to achieve the purpose of turning waste into treasure, and can create some economic benefits.Of which cement 50%,coal 40%, lime 5%,wood chips 5% of the volume ratioand can achieve better economic efficiency and coal power plant requirements.This is available for reference.Heavy metal sludge incineration ash leaching tests showed that the leaching rate of heavy metals is Maximum in the 8-hour oscillation, and then stabilized.Heavy metal sludge incineration ash leaching rate increased with decreasing pH, the pH stabilized after more than 6.