The field-scale test of aeration to accelerate biodegradation of the waste was conducted, which was selected in an old landfill in Hubei province in China. The long-term monitoring was presented, lasted for 11 months, to estimate the degradation stability of the landfill. The monitoring parameters included the temperature, COD and BOD of leachate, gas concentration, water level, settlement, and cellulose/lignin. The results show that the waste degradation rate was increased under the aeration condition, while there was a trend of the stability in the whole waste body. The water level within the landfill was adjusted by discharge measurements, contributing to the buildup of the oxygen environment in landfill. The C/L could be used to assess the stability of the full-scale waste during the degradation process. But, there was obviously discrete by means of drilled sampling. The field-scale test was needed to provide the evidence for aeration engineering operation.
Gas migration rule is of great significance to the safe disposal of landfill. In this article, a gas–solid coupling model was developed and used to simulate the effects of various factors on gas migration. The simulation results showed that gas pressure in landfill decreased with the increase of extraction pressure, anisotropy ratio, coverage gas permeability, extraction well depth, and coverage thickness. The maximum value of gas pressure could reach 683 Pa. Among these factors, extraction pressure played the largest role in the gas pressure, while coverage thickness played the smallest role in it. The radius of influence (RoI) and gas flow rate increased with the increase of extraction pressure, refuse gas permeability, coverage thickness, and the extraction well depth, but with the decrease of coverage gas permeability. The effect of extraction well depth on RoI and gas flow rate was the most significant. When extraction well depth increased from 0.5 landfill height to 0.9 landfill height, the maximum values of RoI and extraction volume increased by 20 m and 20 m3/hr, respectively. It was suggested that the design of landfill gas (LFG) collection system should consider the influence of various factors in practical engineering.
Leachate recirculation is a critical element in the evaluation of the availability of methane production enhancement in bioreactor landfills. Field experiments in leachate injection were conducted in horizontal wells at a landfill in Hubei Province in China. The experiments included the long-term test of methane concentration and production in three cells; the test was operated with nonrecirculation (NR), continued recirculation (CR), and descending recirculation (DR). The average methane concentration in CR is 54.8%, which is higher than that in the NR and DR sites. The average biogas flow rate in the CR site was 2.2 times that in the NR site. The recirculation loading should be determined with the specific conditions, to effectively improve the methane production in field site. The position of the gas collection well was also very important, coordinating with the distribution of the leachate injection well and influence area of the liquid injection. The long-term monitoring of injection volume and gas production is essential to determine the reliability of recirculation for methane reuse.
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