| As the world population increasing quickly and economy growing fast, the problem of environmental pollution has become increasingly worse. In recent years, many municipal sewage treatment plants have been built, which effectively alleviate the pollution of water environment caused by the discharge of municipal sewage and industrial wastewater. At the same time ,a large amount of sewage sludge produced during the process of sewage treatment may result in second pollution to the environment. Since there are high quality of nutrition elements such as nitrogen, phosphorus and kalium, the agricultural utilization of sewage sludge is become an important topics in nowadays research. However, the heavy metals in sewage sludge are the key factor restricting the utilization of sewage sludge in agriculture. Many studies have been made to decrease and reduce the poisonous effect of the heavy metals in sewage sludge, but the characters of system, economy and utility still cannot meet practical demands. Therefore, research on the removal of the heavy metal and the utilization of sewage sludge in agriculture has a very important significance. The sewage sludge from Guilin sewage treatment plant was taken and studied.The research aims is to effectively reduce the poisonous heavy metals and search for an effective method of using the sewage sludge as resources from chemistry, microbe, electrochemistry treatment and phyto-remediation four aspects. The components and chemistry character of Guilin city's sewage sludge are analysed . It is shown that the sewage sludge's nutrition can fully meet the standard of agricultural utilization. The distribution of chemistry forms of heavy metals are studied. All of these studies provide us a basis of further adopting different ways to remove the heavy metal in sewage sludge. The majority of heavy metal elements in the sewage sludge exist in their forms of sulfide, organic combination and residual. There is only a little biologic validity in the sewage sludge. Therefore, the sewage sludge can be used as resources by proper treatments.It is reached that the biologic treatment can effectively remove the heavy metals in sewage sludge. In adition to the removal rate is related to pH value, the characteristics of microbial metabolism and adsorption canspeed up the conversion of the heavy metals form and the release of the heavy metal's elements. Meanwhile, the optimal plunging with iron sulfate salt and sulfur as sub-base are discussed. It can be achieved to a good effect when plunging with cultivate sewage sludge with sulfur. The cycle of the eluviation can be shortened even without acidific.The mechanism of removing the heavy metals by chemistry, microbe, electrochemistry and plant treatment is analysed in details and systematized. It is shown considers that the effects of different acid solution to remove the heavy metals are different. There are different optimal treatment conditions for different metals. The lower pH value is, the better the effect of metals removing is. And , the existence of oxidants is of benefit to effect of removing some heavy metals. The removal effect has reverse ratio with the sewage sludge's concentration. According to experiments, it is concluded that the sewage sludge in Guilin treated by 2%H2O2 and 10%HCl can meet the agricultural standard of the heavy metals.In the electrochemistry experiments, the heavy metals can be removed basically within two hours. As the electrify time went on, the heavy metals ions concentration have been changed unconspicuous. But if high voltage is employed, there probably have a high removal rate of the heavy metals. The different treatment methods are also compared from the point of economy and the cost of the electrochemistry treatment is 4.4ï¿¥/m3,the cost of the microbe treatment is 1.04ï¿¥/m3 and the cost of chemistry treatment (2%H2O2 and 10%HCl) is 6.03ï¿¥/m3. so the best method is microbe treatment now.Using the organic commingle fertilizer made from the municipal sewage sludge can increase the production of the...
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