The Technology For Acceleration The Stabilization Process Of Anaerobic Bioreactor Landfill Based On Leachate Recirculation

While traditional municipal solid waste (MSW) landfill has some disadvantages as long stable period, difficult and expensive for leachate treatment, the bioreactor landfill can not only accelerate the stabilization of landfilled waste, but also cut down the quantity of leachate and reduce its pollutant intensity, so it will be a competitive way to treat MSW in the future. Leachate recirculation, as one of the leading control measures, can accelerate the stabilization of bioreactor landfill and this paper focuses on this point.By means of simulated waste columns with different density and thickness, the characteristics of the movement and storage of recirculated leachate in waste was first studied in a systematic way for different leachate recirculation modes (different recirculation frequency, quantity and rate). The influence of different leachate recirculation frequency on the start-up and stabilization of anaerobic bioreactor landfill was also studied. Based on the experimental results, the kinetics model of stabilization of anaerobic bioreactor landfill was developed after the quantity of degradable solid organic waste, the leachate COD concentration and the rate of methane production in the landfill were taken into account comprehensively. In view of slowly-dropped COD concentration and the higher-kept ammonia-N concentration in the leachate in the late stabilization stage of the landfill, the idea to change its operation mode was brought forward and put successfully into practice in simulated experiment.It was shown from the experiment on the hydrodynamic characteristics of recirculated leachate that: (1) the effective water storage capacity of buried waste is a function of the leachate recirculation mode and environmental temperature. The higher recirculation frequency, the more recirculated leachate quantity and the lower recirculation rate, the higher the capacity is. The capacity changes with temperature as negative linear relationship, that is, the higher temperature, the lower capacity is. As the capacity of the waste increases with the temperature drop, at the same time, the action of microorganism starts to weaken and its requirment for the moisture becomes less, the frequency and quantity of leachate recirculation reduced properly in the environment of lower temperature will not result in the too much moisture drop. (2) Non-uniform flow prevails over the earlier stage seepage of recirculated leachate. However, the leachate recirculation with a low frequency, large quantity and small rate, the big waste density and thickness may leads to more uniform seepage. After the influence of different leachate recirculation modes on the capacity and the water moisture of the waste were fully taken into account, to recirculate leachate at high frequency, large quantity and lower rate is more favourable for improving water moisture distribution in the waste.It was shown from the simulating experiment on the start-up of anaerobic bioreactor landfill that the landfill generates methane earlier if leachate recirculation frequency is higher under the condition of adjustment pH of leachate before recirculation, but there was not much difference if leachate recirculation was implemented once every 3 days. Considering the time and the expenditure in the start-up period, the best frequency to recirculate leachate is once every 3 days for the start-up period of anaerobic bioreactor landfill.It was also indicated from the experiment on the stabilization of anaerobic bioreactor landfill that the rate of methane production finds the faster, the higher leachate recirculation frequency, but the rate will rises in a more smaller manner with the higher leachate recirculation frequency. During the stabilization of the landfill, the quickly-dropped rate of methane production does not means that the waste has been degraded well. Determination of the stabilization process of the landfill requires to take fully account of the organic pollutant strength of leachate, the rate of methane production and the degradation extent of organic so...