Computer simulation of moisture distribution in unlined aerobic bioreactor landfills——quasi-steady-state condition

摘要

Closed unlined landfills can found in many cities in China,as a side product of economic and urban development in last century.The degradation velocity of municipal solid waste (MSW) in such landfills can be very slow due to lack of moisture and its stabilization time can reach twenty years or more if no measure is enforced from outside.Recently aerobic bioreaetor landfill technology has been applied to accelerate MSW decomposition by introducing water and air into the landfill.However,excessive water could also result in secondary pollution to ground water.In order to apply the aerobic bioreactor landfill technology for unlined landfills treatment without leaehate across the site boundary,an appropriate water injection volume has to be determined.In this paper,a 3D mathematical model is established from mass balance and Darcy's law in a cylindrical coordinate system for the simulation of moisture distribution in an unlined aerobic bioreactor landfill.Moisture profile in landfills is obtained by coupling the aerobic bio-reaction with the water generation term at different scales.The aerobic bio-reaction rate is considered as the function of moisture content,temperature,matrix concentration,oxygen concentration and microorganism concentration.Two water injection styles,surface ponding and vertical well,were investigated.To avoid ground water contamination,moisture filtration rate is assumed to be zero at the site bottom.A feasible water injection volume is determined under quasi-steady-state.