Study Of Modified Sewage Sludge Used As Comprehensive Cover Material In MSW Landfill

With the development of wastewater treatment technology, the problem of sludgeis more and more prominent. As our country’s economic and status of the sludge, it isnecessary and feasible for modified sludge as landfill cover material, and introduce theresearch progress of modified sludge as landfill cover material in China and abroad.HanChuan sludge plant dewatered sludge were used as research subjects inlaboratory in this paper. Based on tests of fresh sludge on the basic physical propertieshave carried out, the results show that the dewatered sludge as landfill cover orrecycling will bring a great difficulty as moisture content is very high.The dewateredsludge must be modified,if it be used as landfill cover material.The orthogonal experiment of sludge modified adopted additives which were silt,quick lime, cement and fly ash in the laboratory were conducted to evaluate the bestratio of modified sludge as final cover was determined from the aspects of strength andpermeability. Through simulation SEEP/W, it is concluded that the best coefficient ofpermeability of intermediate cover in wuhan is10-5cm/s. On the basis of orthogonal test,The best ratio of modified sludge as intermediate cover was determined. The test of wetand dry properties of modified sludge as final cover was carried out; The experiment ofdifferent temperature and soaking in water and simulated leachate of modified sludgewere carried out.Experimental results show that the sludge:silt:quick lime:cement:fly ash=100:70:15:5:10(mass ratio) is best for final cover material. After3times of dry-wetcirculation, no adverse effect to strength of the modified sludge, after2times of dry-wetcirculation, the moisture content of sludge and shear strength reaches a steady state.Since shrinkage ratio of the modified sludge is greater than swelling ratio, keep watermeasures should be taken to prevent cracking as a final cover.The proportion ofintermediate cover material is sludge: silt: quick lime: cement: tire=100,70:15:5:15(mass ratio). Soaking in water for a week, as increase of temperature, moisture contentincreases, unconfined compressive strength(UCS) is reduced, the permeabilitycoefficient decreases and keep stable. Soaking in water for a month, unconfinedcompressive strength reduced gradually, the permeability coefficient showed a trend ofdecrease; Soaking in simulated leachate, unconfined compressive strength increasesgradually, permeability coefficient showed a trend of decrease, but it changed behind inwater. Because it is acid rain city in wuhan, the modified sludge as intermediate covermaterial, does not cause perched water for a long time.