Analyses on a high leachate mound in a landfill of municipal solid waste in China

The leachate levels in the landfills in southern China are generally high. Field monitoring was carried out in the Suzhou landfill to investigate the leachate mound. The saturated hydraulic conductivity and soil-water characteristic curve (SWCC) of municipal solid waste were measured using samples taken from different depths of the landfill. Field monitoring reveals that a perched leachate mound and a substantial main leachate mound existed in the landfill. The saturated hydraulic conductivities of wastes in shallow, middle and deep depth were measured to be 4.81 x 10(-2), 3.50 x 10(-3) and 3.56 x 10(-4) cm/s, respectively. The results of SWCC tests show that the SWCC curve was steep when matric suction was low, and the shallower the waste the steeper would be the curve. In addition to the field and laboratory tests, an unsaturated-saturated seepage analysis was conducted to simulate the development of the high leachate mound and to calculate the annual leachate production. The simulated volumetric water content in the unsaturated zone was about 40 %, which agreed well with the test result. The calculated leachate mound was consistent with the field measurement. The calculated annual and daily leachate productions were all more reasonable than the results of the HELP model.