A Study On The Quality Of Leachate And The Variation Character Of Landfill Gas In Intensified Semi-aerobic Landfill

As the third biggest man-made methane emission source, methane mitigation inlandfill has been a world-wide concern problem in landfill technology research field.Because of the oxygen can be introduced into landfill, methanogens can be depressedin semi-aerobic landfill. This paper had discussed the influence of cowl on thesemi-aerobic landfill gas and the quality of leachate in intensified semi-aerobiclandfill. The conclusions were as follows:Oxygen concentration in semi-aerobic landfill had a distinctive differencebetween layers. Oxygen at the bottom was mainly offered by leachate collection pipes.The surface layer was filled by aerobic zones caused by different sedimentation.Thus, oxygen concentration changed with atmospheric temperature. The middle layerwas occupied by anaerobic zone. The oxygen concentration presented a phenomenonthat surface layer>upper layer>middle layer>base layer after deducting the oxygentransferred from the leachate collection pipes.Wind energy can be better used to accelerate the air flow rate in vent pipe afterthe cowl was installed on the vent pipe of semi-aerobic landfill. Thus, oxygenconcentration and aerobic radius were expanded. The oxygen concentration andaerobic radius in semi-aerobic landfill with cowl was20.7and10.5percent more thannormal semi-aerobic landfill when the wind speed was3m/s. The effect of the cowlon oxygen transportation went max when the wind speed was5m/s. It can introduce23.5percent of oxygen more into semi-aerobic landfill and the aerobic radius can be20.2percent more. Meantime, the cowl won’t impede the air flow rate in vent pipeeven there was no wind. Also, methane concentration in MSW can be remarkablydeclined after using the cowl. It can reduce24.2,22.6,16.5percent of methane whenthe wind speed was3m/s,5m/s,7m/s each.The concentration of methane and carbon dioxide dropped down with theincrease of oxygen concentration by exponential law. The spatial variability ofmethane was higher than oxygen and carbon dioxide because of the lighter density.The higher the oxygen concentration was, the higher the temperature was. Thedistribution of temperature presented that upper layer>surface layer>middle layer>base layer because of the different heat loss.With leachate recirculation, the temperature of MSW, the solubility of organicsin leachate and the biodegradability had increased, the nitratate had decreased. Thedegradation rate of CODCrand ammonia-nitrogen in leachate-recycled semi-aerobiclandfill came to the best when the recycle rate was twice a week. The degradation ratewas423mg/(l·week) and768mg/(l·week), respectively. Average concentration ofmethane except the surface layer went up with the recirculation rate. Methaneconcentrations were17.8,25.3,27.0percent which were17.9,64.2,50.0percent morethan none recirculation when the recirculation rate was once, twice and forth a week.In all, the degradation rate of organics in leachate came to the fastest when theleachate recirculation rate was twice a week.