Abstract: In order to investigate the removal characteristics and efficiency,semi-aerobic refuse with an age of 3 a in the laboratory was used to remove organics in leachate by filling in bioreactors by perfusion under the conditions of natural ventilation and closed landfilling.The experimental investigation shows that the most of organics with a molecular weight of less than 2×103 are removed by the aged refuse.Under natural ventilation and closed landfilling conditions,the removal efficiency of total dissolved organics is respectively 92% and 87% when hydraulic load is 40 L/(m3·d),and that of total dissolved refractory organics is respectively 34% and 21% when the hydraulic load is 50 L/(m3·d).Under a natural ventilation condition,the removal efficiency of chemical oxygen demand(COD) increases from 85% up to 93% as the hydraulic load decreases from 50 to 25 L/(m3·d),and the relative volume load decreases from 600 to 300 g/(m3·d).After continuous operation of 40 d,the mass concentration of COD in effluent ranges from 400 to 900 mg/L.