Influence of semi-aerobic and anaerobic landfill operation with leachate recirculation on stabilization processes

To investigate the influence of semi-aerobic and anaerobic landfill operation on stabilization processes of landfill sites with leachate recirculation, in situ simulated semi-aerobic landfill sites with leachate recirculation (SLR) and anaerobic landfill sites with leachate recirculation (ALR) were constructed. Refuse properties and landfill settlement were determined. Leachate quality and landfill gas compositions were monitored regularly. Based on the data obtained, leachate quality, landfill gas and final refuse characteristics were adopted as assessment factors to quantitatively evaluate stabilization of landfill sites. The results showed that volatile solids (VS), total organic carbon (TOC) and biologically degradable matter (BDM) of aged refuse in SLR (15.8, 7.3 and 9.9%, respectively) were lower than those in ALR, which were 19.1, 9.2 and 11.3%, respectively. Settlement and reduction ratio of SLR were 1.71 m and 30.91%, respectively, and 1.40 m and 25.45% in the case of ALR. Concentrations of organic pollutants, especially ammonia, were reduced in SLR, and variation in leachate quality was also smoother than ALR. Throughout the experiment the average concentration of CH4 in ALR was higher than that in SLR (36.7 and 14.5%, respectively). At the end of the experiment, SLR was moderately stable, while ALR was moderately unstable. The comprehensive assessment index (I) for SLR and ALR was 200 and 355, respectively.