Status Survey And Post-assessment On Sludge Treatment And Disposal In Xi’an Urban Sewage Treatment Plant

This article firstly expounds the importance of the post-assessment on sludge treatment and disposal in municipal sewage treatment plant. Then selected three Xi’an in operation sewage treatment plants’ sludge treatment and disposal as the research object, collecting the early stage of the project feasibility study report and environmental impact assessment document, combining the field survey, through the analysis of the gap between predicted and actual operation for in & out of the water quality of the water, sludge production, sludge disposal method and disposal of sludge treatment cost in sewage treatment plant, got the post-assessment results of the sludge treatment and disposal in municipal sewage treatment plant. Eventually to improve the attention and focus on urban sewage treatment plant project from feasibility study EIA stage to operation and management stage for sludge treatment and disposal.The results show that the original feasibility study and EIA documents "water before sludge" phenomenon is serious in the urban sewage treatment plant project, the description of the sludge treatment part is too simple. Although both feasibility study and EIA documents can predict with relative accuracy on the moisture content of sludge, there are too many factors influencing the sludge production and prediction accuracy, this cause the gap, more or less, between predicted value and actual value of the sludge production. In the meantime, lack of discourse on sludge treatment and disposal direction of economic rationality and technical feasibility, especially EIA document had not a word to say sludge disposal cost, although this cost of the sludge treatment and proposal occupies 50%-70% of the sewage treatment plant operation total cost.Therefore, it is a hindrance of sludge reduction, stabilization, harmless and recycling cannot be achieved in the project feasibility study and the EIA stage, and this cause a series of problems such as the shortage of funds, difficult operation, unclear disposal route and so on during the actual operation of sludge disposal. In addition, post-assessment also found that the sludge disposal relevant department responsibility is not clear and the lack of government supervision system, which are another important reasons of the low rates for sludge disposal.