Study On Environmental And Engineering Properties And Landfill Of Civil Sludge

Landfill is a kind of suitable sludge disposal method for China. In the methods of laboratory tests, theoretical analysis and numerical simulations, researches were conducted on environment and engineering properties of sludge. Then, fly ash, silty clay and lime were utilized to improved the landfill properties of sludge.Different kinds of sludge disposal method at present were compared firstly. Then both advantages and disadvantages of these methods were summarized. In order to solve the technical problems in landfill of sludge for China, a method, in which the sludge will be disposed by monofill after its landfill properties was improved, was put forward in this paper.Landfill properties improved by the adding of the consolidation materials. Significant increases in sludge strength and permeability was achieved to match suitability for monofill. The adding of lime can improve the volume stability and permeability of solidified sludge. Based on orthogonal experiment, the solidifying effectiveness of silty clay was found to be more notable than fly ash. This can be resulted from the special environment of sludge in which the activities of fly ash was not excited.Freeze-drying technology and scanning electron microscope were utilized to study the microstructure of solidified sludge. It was found density of sludge was improved after solidification. The hydration effect of solidifying materials and sludge can be the reason of improvement in strength and complication in microstructure. Perimeter and area of soil grain can be effective parameters to describe the microsturcture of soil.The column fill with lime and sludge performs the highest permeability, the largest mount of leachate, the highest PH and the highest COD because of the adding of lime. Lime performed a double influence on heavy metals in sludge. It can cause the instability of copper ion in sludge but make the zinc ion more stable. The influence of silty clay and fly ash was not significant.Transport of contaminant from sludge was studied with numerical simulation in varied geological conditions. It was revealed that adsorption function, permeability and hydraulic gradient play the key role in the transport of contaminant. For normal hydraulic gradient and low permeability stratum, dispersion controls the transport. While the permeability was improved to 1×10^-4m/s, convection controls the transport and the contaminated area was expanded significantly.Life expectancy is an important design parameter of landfill. To improve the capacity and life expectancy of landfill, the slope ratio of landfill was optimized with different computation methods of slope stability. It was revealed that, when the slope ratio of 1:4～1:5 was adopted, the capacities of landfill can reach the maximum value as the stability of slope can be satisfied at the same time.