A Study On The Law Of The Water/Leachate Migration In Landfill

Landfill is the most commonly used disposition of MSW in china, but landfill leachate is complicated and difficult to be treated. In many treatments on the leachate, recirculation, with advantages of less land occupation, low investment and simple operation, is considered as an dual effictive way of processing the leachate and accelerating the stabilization of landfill. Research shows that recirculation mainly increases the moisture content of landfill to improve microenviorment of microbial anaerobic digestion, while the gravity of leachate affects the landfill gas migration. After the landfill site is closed, the combination of leachate recirculation and control of landfill gas migration will reduce pollution of leachate, control landfill gas migration, and accelerate the stabilization of landfill.In this paper, details will given for the migration laws of water and gas with leachate recirculation from four aspects:(1) Collect correlative research status about leachate recirculation, the yield model and migration laws of leachate and landfill gas at home and abroad.(2) Build the migration model of leachate and the water-gas two-phase migration model based on fluid mechanics in porous medium with the premise of considering closed landfill sites as saturating porous medium.(3) Take advantage of the software named Comsol to numerically simulate those two models above.(4) The numerically simulation of migration laws of leachate showed that the moisture content will be reduced and eventually stabilized at around 28 percent without leachate recirculation. Different way of leachate recirculation and different hydraulic load has affected the water distribution of landfill.The numerically simulation of water-gas two-phase migration showed that with the constant infiltration of water, the effective permeability coefficient of gas became smaller, resulting in gas production down.