Study And Analysis On The Disposal Process Of Civil Sewage Sludge And Its Resource Utilization

With the advancement of China’s urbanization process, urban sewage treatment plantsludge disposal problem placed in front of the decision-making level as a difficultenvironmental problem. Sewage sludge is the inevitable product of the urban sewagetreatment, which brings together the unable digested pollutants such as heavy metals andothers in urban sewage treatment process, and also contains a large number of pathogens,microbial and so on. Without proper treatment and disposal, the sewage sludge may forming asecondary pollution, causing great damage to the environment. At present, China’s sewagesludge disposal business has just started soon, the main disposal methods is still sludgelandfill and land utilization,which have a possibility of severely environmental impact, Andhave a drawback of low resource utilization ratio.Therefore, it’s badly in need of opening up anew way of sludge utilization.The research object of this study is the sewage sludge of a medium-sized city sewagetreatment plant in the northwest region of China. The experimental test results show that thecontent of toxic and harmful substances in this city sludge is at a low level. Combined withnational advocacy and local industrial structure, in line with the sludge disposal principle ofdecrease decrement, innocuity and resource, this paper presents three options: Roasting sludgeand other auxiliary material into ceramsite, Making baking-free brick with thermal dryingsludge by calcium, Land utilization with thermal drying sludge by microorganisms’ lifeactivities. This paper analysed the three options in depth and introduced gray correlationtheory to take quantitative calculation. Gray analysis results indicated that the "Roastingsludge and other auxiliary material into ceramsite" process is the better (with the relationaldegree of0.89, the remaining two were0.85,0.81).The city have numerous of thermal power plants as well as fly ash, combined with thefact, this paper selected fly ash and clay as auxiliary materials of ceramic materials selection;The ratio of the three materials is as follows: Sewage sludge: Fly ash: Clay=4:4:2. Theroasting process control conditions: Preheating temperature350°C, preheating time30min;Roasting temperature1150°C, roasting time20min. Under the roasting conditions, theceramic products density is about700kg/m3, meet the requirements of GB/T17431.1-2010"lightweight aggregate and its test methods: light aggregate".Finally, this paper take risk analysis and benefit accounting on the application of"Roasting sludge and other auxiliary material into ceramsite" process in this city, which confirmed the feasibility of the process in the city. And Proved the process is a new sewagesludge disposal method of resources utilization in line with the city’s political, environmental,economic and social.