Utilization Of Sludge To Water Resources

Urban water treatment plant could produce1.5billion cubic meters sludge peryear, which discarded in natural environment could have a serious negative effect onthe water and the ecological environment. At present, there are many disposalmethods to treat sludge produced during urban water treatment, including sanitarylandfill, land use, natural water body discharge, entering into sewage treatment plant,etc. For these disposal methods, the cost of investment and operation is high and it iseasy to cause "secondary pollution" due to improper disposal.The sludge recycling could be achieved through mixing the sludge with otherraw materials to produce fired brick, lightweight aggregate or other building materials.In this study, the sludge produced in water treatment, sinotrans foundation pit soil,and slag were chosen as raw materials to burn sintered hollow brick. The results showthat when the ratio of raw material is3:4:3, quality indicators including criticalmoisture content, drying shrinkage, firing shrinkage and so on, could achieve theprocess requirements. Then lime burst test, hoarfrost and radiological tests wereconducted on fired specimens based on the standards of GB/T2542and GB/T6566-2010, indicating that lime burst and frost phenomenon did not appear on thefired specimens and the radioactivity of the fired specimens conformed to therequirements of the new nuclides limited radiation. Sintered lightweight aggregate testwas conducted on the sludge collected from the water treatment plant located in threeregions. For the three kinds of sludge, the physical and chemical test and two stagesof firing were carried out to obtain the expansion temperature range, softeningtemperature, optimum calcination temperature, water absorption rate, particle density.Then the proportion of raw materials for burning lightweight aggregate and burningprocess were identified. Combined with an engineering example of fired brick using sludge, the aspects of process, products and equipment selection, and projectconstruction were studied, and the social and economic effects were evaluated. Thiswork tried to provide an example of the industrialization of construction materialsusing sludge through the implementation of this method in the project.The results showed that it is feasible to produce fired brick andlightweight aggregate using sludge produced in urban water treatment plant.Construction material produced by sludge could not only provide internal combustionin the firing process, but also saves a lot of land resources, and the sludge could beutilized with the character of reclamation, harmlessness and low dosage.